{ "miscs": [ { "textRaw": "About this documentation", "name": "About this documentation", "introduced_in": "v0.10.0", "type": "misc", "desc": "
Welcome to the official API reference documentation for Node.js!
\nNode.js is a JavaScript runtime built on the V8 JavaScript engine.
", "miscs": [ { "textRaw": "Contributing", "name": "contributing", "desc": "Report errors in this documentation in the issue tracker. See\nthe contributing guide for directions on how to submit pull requests.
", "type": "misc", "displayName": "Contributing" }, { "textRaw": "Stability index", "name": "Stability index", "type": "misc", "desc": "Throughout the documentation are indications of a section's stability. Some APIs\nare so proven and so relied upon that they are unlikely to ever change at all.\nOthers are brand new and experimental, or known to be hazardous.
\nThe stability indices are as follows:
\n\n\n\nStability: 0 - Deprecated. The feature may emit warnings. Backward\ncompatibility is not guaranteed.
\n
\n\n\nStability: 1 - Experimental. The feature is not subject to\nsemantic versioning rules. Non-backward compatible changes or removal may\noccur in any future release. Use of the feature is not recommended in\nproduction environments.
\nExperimental features are subdivided into stages:
\n\n
\n- 1.0 - Early development. Experimental features at this stage are unfinished\nand subject to substantial change.
\n- 1.1 - Active development. Experimental features at this stage are nearing\nminimum viability.
\n- 1.2 - Release candidate. Experimental features at this stage are hopefully\nready to become stable. No further breaking changes are anticipated but may\nstill occur in response to user feedback. We encourage user testing and\nfeedback so that we can know that this feature is ready to be marked as\nstable.
\n
\n\n\nStability: 2 - Stable. Compatibility with the npm ecosystem is a high\npriority.
\n
\n\nStability: 3 - Legacy. Although this feature is unlikely to be removed and is\nstill covered by semantic versioning guarantees, it is no longer actively\nmaintained, and other alternatives are available.
\n
Features are marked as legacy rather than being deprecated if their use does no\nharm, and they are widely relied upon within the npm ecosystem. Bugs found in\nlegacy features are unlikely to be fixed.
\nUse caution when making use of Experimental features, particularly when\nauthoring libraries. Users may not be aware that experimental features are being\nused. Bugs or behavior changes may surprise users when Experimental API\nmodifications occur. To avoid surprises, use of an Experimental feature may need\na command-line flag. Experimental features may also emit a warning.
" }, { "textRaw": "Stability overview", "name": "stability_overview", "desc": "\n", "type": "misc", "displayName": "Stability overview" }, { "textRaw": "JSON output", "name": "json_output", "meta": { "added": [ "v0.6.12" ], "changes": [] }, "desc": "Every .html
document has a corresponding .json
document. This is for IDEs\nand other utilities that consume the documentation.
Node.js functions which wrap a system call will document that. The docs link\nto the corresponding man pages which describe how the system call works.
\nMost Unix system calls have Windows analogues. Still, behavior differences may\nbe unavoidable.
", "type": "misc", "displayName": "System calls and man pages" } ], "source": "doc/api/documentation.md" }, { "textRaw": "C++ addons", "name": "C++ addons", "introduced_in": "v0.10.0", "type": "misc", "desc": "Addons are dynamically-linked shared objects written in C++. The\nrequire()
function can load addons as ordinary Node.js modules.\nAddons provide an interface between JavaScript and C/C++ libraries.
There are three options for implementing addons: Node-API, nan, or direct\nuse of internal V8, libuv, and Node.js libraries. Unless there is a need for\ndirect access to functionality which is not exposed by Node-API, use Node-API.\nRefer to C/C++ addons with Node-API for more information on\nNode-API.
\nWhen not using Node-API, implementing addons is complicated,\ninvolving knowledge of several components and APIs:
\nV8: the C++ library Node.js uses to provide the\nJavaScript implementation. V8 provides the mechanisms for creating objects,\ncalling functions, etc. V8's API is documented mostly in the\nv8.h
header file (deps/v8/include/v8.h
in the Node.js source\ntree), which is also available online.
libuv: The C library that implements the Node.js event loop, its worker\nthreads and all of the asynchronous behaviors of the platform. It also\nserves as a cross-platform abstraction library, giving easy, POSIX-like\naccess across all major operating systems to many common system tasks, such\nas interacting with the file system, sockets, timers, and system events. libuv\nalso provides a threading abstraction similar to POSIX threads for\nmore sophisticated asynchronous addons that need to move beyond the\nstandard event loop. Addon authors should\navoid blocking the event loop with I/O or other time-intensive tasks by\noffloading work via libuv to non-blocking system operations, worker threads,\nor a custom use of libuv threads.
\nInternal Node.js libraries. Node.js itself exports C++ APIs that addons can\nuse, the most important of which is the node::ObjectWrap
class.
Node.js includes other statically linked libraries including OpenSSL. These\nother libraries are located in the deps/
directory in the Node.js source\ntree. Only the libuv, OpenSSL, V8, and zlib symbols are purposefully\nre-exported by Node.js and may be used to various extents by addons. See\nLinking to libraries included with Node.js for additional information.
All of the following examples are available for download and may\nbe used as the starting-point for an addon.
", "miscs": [ { "textRaw": "Hello world", "name": "hello_world", "desc": "This \"Hello world\" example is a simple addon, written in C++, that is the\nequivalent of the following JavaScript code:
\nmodule.exports.hello = () => 'world';\n
\nFirst, create the file hello.cc
:
// hello.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid Method(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n args.GetReturnValue().Set(String::NewFromUtf8(\n isolate, \"world\").ToLocalChecked());\n}\n\nvoid Initialize(Local<Object> exports) {\n NODE_SET_METHOD(exports, \"hello\", Method);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)\n\n} // namespace demo\n
\nAll Node.js addons must export an initialization function following\nthe pattern:
\nvoid Initialize(Local<Object> exports);\nNODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)\n
\nThere is no semi-colon after NODE_MODULE
as it's not a function (see\nnode.h
).
The module_name
must match the filename of the final binary (excluding\nthe .node
suffix).
In the hello.cc
example, then, the initialization function is Initialize
\nand the addon module name is addon
.
When building addons with node-gyp
, using the macro NODE_GYP_MODULE_NAME
as\nthe first parameter of NODE_MODULE()
will ensure that the name of the final\nbinary will be passed to NODE_MODULE()
.
Addons defined with NODE_MODULE()
can not be loaded in multiple contexts or\nmultiple threads at the same time.
There are environments in which Node.js addons may need to be loaded multiple\ntimes in multiple contexts. For example, the Electron runtime runs multiple\ninstances of Node.js in a single process. Each instance will have its own\nrequire()
cache, and thus each instance will need a native addon to behave\ncorrectly when loaded via require()
. This means that the addon\nmust support multiple initializations.
A context-aware addon can be constructed by using the macro\nNODE_MODULE_INITIALIZER
, which expands to the name of a function which Node.js\nwill expect to find when it loads an addon. An addon can thus be initialized as\nin the following example:
using namespace v8;\n\nextern \"C\" NODE_MODULE_EXPORT void\nNODE_MODULE_INITIALIZER(Local<Object> exports,\n Local<Value> module,\n Local<Context> context) {\n /* Perform addon initialization steps here. */\n}\n
\nAnother option is to use the macro NODE_MODULE_INIT()
, which will also\nconstruct a context-aware addon. Unlike NODE_MODULE()
, which is used to\nconstruct an addon around a given addon initializer function,\nNODE_MODULE_INIT()
serves as the declaration of such an initializer to be\nfollowed by a function body.
The following three variables may be used inside the function body following an\ninvocation of NODE_MODULE_INIT()
:
Local<Object> exports
,Local<Value> module
, andLocal<Context> context
The choice to build a context-aware addon carries with it the responsibility of\ncarefully managing global static data. Since the addon may be loaded multiple\ntimes, potentially even from different threads, any global static data stored\nin the addon must be properly protected, and must not contain any persistent\nreferences to JavaScript objects. The reason for this is that JavaScript\nobjects are only valid in one context, and will likely cause a crash when\naccessed from the wrong context or from a different thread than the one on which\nthey were created.
\nThe context-aware addon can be structured to avoid global static data by\nperforming the following steps:
\nstatic void DeleteInstance(void* data) {\n // Cast `data` to an instance of the class and delete it.\n}\n
\nnew
keyword.node::AddEnvironmentCleanupHook()
, passing it the above-created\ninstance and a pointer to DeleteInstance()
. This will ensure the instance is\ndeleted when the environment is torn down.v8::External
, andv8::External
to all methods exposed to JavaScript by passing it\nto v8::FunctionTemplate::New()
or v8::Function::New()
which creates the\nnative-backed JavaScript functions. The third parameter of\nv8::FunctionTemplate::New()
or v8::Function::New()
accepts the\nv8::External
and makes it available in the native callback using the\nv8::FunctionCallbackInfo::Data()
method.This will ensure that the per-addon-instance data reaches each binding that can\nbe called from JavaScript. The per-addon-instance data must also be passed into\nany asynchronous callbacks the addon may create.
\nThe following example illustrates the implementation of a context-aware addon:
\n#include <node.h>\n\nusing namespace v8;\n\nclass AddonData {\n public:\n explicit AddonData(Isolate* isolate):\n call_count(0) {\n // Ensure this per-addon-instance data is deleted at environment cleanup.\n node::AddEnvironmentCleanupHook(isolate, DeleteInstance, this);\n }\n\n // Per-addon data.\n int call_count;\n\n static void DeleteInstance(void* data) {\n delete static_cast<AddonData*>(data);\n }\n};\n\nstatic void Method(const v8::FunctionCallbackInfo<v8::Value>& info) {\n // Retrieve the per-addon-instance data.\n AddonData* data =\n reinterpret_cast<AddonData*>(info.Data().As<External>()->Value());\n data->call_count++;\n info.GetReturnValue().Set((double)data->call_count);\n}\n\n// Initialize this addon to be context-aware.\nNODE_MODULE_INIT(/* exports, module, context */) {\n Isolate* isolate = context->GetIsolate();\n\n // Create a new instance of `AddonData` for this instance of the addon and\n // tie its life cycle to that of the Node.js environment.\n AddonData* data = new AddonData(isolate);\n\n // Wrap the data in a `v8::External` so we can pass it to the method we\n // expose.\n Local<External> external = External::New(isolate, data);\n\n // Expose the method `Method` to JavaScript, and make sure it receives the\n // per-addon-instance data we created above by passing `external` as the\n // third parameter to the `FunctionTemplate` constructor.\n exports->Set(context,\n String::NewFromUtf8(isolate, \"method\").ToLocalChecked(),\n FunctionTemplate::New(isolate, Method, external)\n ->GetFunction(context).ToLocalChecked()).FromJust();\n}\n
",
"modules": [
{
"textRaw": "Worker support",
"name": "worker_support",
"meta": {
"changes": [
{
"version": [
"v14.8.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34572",
"description": "Cleanup hooks may now be asynchronous."
}
]
},
"desc": "In order to be loaded from multiple Node.js environments,\nsuch as a main thread and a Worker thread, an add-on needs to either:
\nNODE_MODULE_INIT()
as described aboveIn order to support Worker
threads, addons need to clean up any resources\nthey may have allocated when such a thread exists. This can be achieved through\nthe usage of the AddEnvironmentCleanupHook()
function:
void AddEnvironmentCleanupHook(v8::Isolate* isolate,\n void (*fun)(void* arg),\n void* arg);\n
\nThis function adds a hook that will run before a given Node.js instance shuts\ndown. If necessary, such hooks can be removed before they are run using\nRemoveEnvironmentCleanupHook()
, which has the same signature. Callbacks are\nrun in last-in first-out order.
If necessary, there is an additional pair of AddEnvironmentCleanupHook()
\nand RemoveEnvironmentCleanupHook()
overloads, where the cleanup hook takes a\ncallback function. This can be used for shutting down asynchronous resources,\nsuch as any libuv handles registered by the addon.
The following addon.cc
uses AddEnvironmentCleanupHook
:
// addon.cc\n#include <node.h>\n#include <assert.h>\n#include <stdlib.h>\n\nusing node::AddEnvironmentCleanupHook;\nusing v8::HandleScope;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\n\n// Note: In a real-world application, do not rely on static/global data.\nstatic char cookie[] = \"yum yum\";\nstatic int cleanup_cb1_called = 0;\nstatic int cleanup_cb2_called = 0;\n\nstatic void cleanup_cb1(void* arg) {\n Isolate* isolate = static_cast<Isolate*>(arg);\n HandleScope scope(isolate);\n Local<Object> obj = Object::New(isolate);\n assert(!obj.IsEmpty()); // assert VM is still alive\n assert(obj->IsObject());\n cleanup_cb1_called++;\n}\n\nstatic void cleanup_cb2(void* arg) {\n assert(arg == static_cast<void*>(cookie));\n cleanup_cb2_called++;\n}\n\nstatic void sanity_check(void*) {\n assert(cleanup_cb1_called == 1);\n assert(cleanup_cb2_called == 1);\n}\n\n// Initialize this addon to be context-aware.\nNODE_MODULE_INIT(/* exports, module, context */) {\n Isolate* isolate = context->GetIsolate();\n\n AddEnvironmentCleanupHook(isolate, sanity_check, nullptr);\n AddEnvironmentCleanupHook(isolate, cleanup_cb2, cookie);\n AddEnvironmentCleanupHook(isolate, cleanup_cb1, isolate);\n}\n
\nTest in JavaScript by running:
\n// test.js\nrequire('./build/Release/addon');\n
",
"type": "module",
"displayName": "Worker support"
}
],
"type": "module",
"displayName": "Context-aware addons"
},
{
"textRaw": "Building",
"name": "building",
"desc": "Once the source code has been written, it must be compiled into the binary\naddon.node
file. To do so, create a file called binding.gyp
in the\ntop-level of the project describing the build configuration of the module\nusing a JSON-like format. This file is used by node-gyp, a tool written\nspecifically to compile Node.js addons.
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [ \"hello.cc\" ]\n }\n ]\n}\n
\nA version of the node-gyp
utility is bundled and distributed with\nNode.js as part of npm
. This version is not made directly available for\ndevelopers to use and is intended only to support the ability to use the\nnpm install
command to compile and install addons. Developers who wish to\nuse node-gyp
directly can install it using the command\nnpm install -g node-gyp
. See the node-gyp
installation instructions for\nmore information, including platform-specific requirements.
Once the binding.gyp
file has been created, use node-gyp configure
to\ngenerate the appropriate project build files for the current platform. This\nwill generate either a Makefile
(on Unix platforms) or a vcxproj
file\n(on Windows) in the build/
directory.
Next, invoke the node-gyp build
command to generate the compiled addon.node
\nfile. This will be put into the build/Release/
directory.
When using npm install
to install a Node.js addon, npm uses its own bundled\nversion of node-gyp
to perform this same set of actions, generating a\ncompiled version of the addon for the user's platform on demand.
Once built, the binary addon can be used from within Node.js by pointing\nrequire()
to the built addon.node
module:
// hello.js\nconst addon = require('./build/Release/addon');\n\nconsole.log(addon.hello());\n// Prints: 'world'\n
\nBecause the exact path to the compiled addon binary can vary depending on how\nit is compiled (i.e. sometimes it may be in ./build/Debug/
), addons can use\nthe bindings package to load the compiled module.
While the bindings
package implementation is more sophisticated in how it\nlocates addon modules, it is essentially using a try…catch
pattern similar to:
try {\n return require('./build/Release/addon.node');\n} catch (err) {\n return require('./build/Debug/addon.node');\n}\n
",
"type": "module",
"displayName": "Building"
},
{
"textRaw": "Linking to libraries included with Node.js",
"name": "linking_to_libraries_included_with_node.js",
"desc": "Node.js uses statically linked libraries such as V8, libuv, and OpenSSL. All\naddons are required to link to V8 and may link to any of the other dependencies\nas well. Typically, this is as simple as including the appropriate\n#include <...>
statements (e.g. #include <v8.h>
) and node-gyp
will locate\nthe appropriate headers automatically. However, there are a few caveats to be\naware of:
When node-gyp
runs, it will detect the specific release version of Node.js\nand download either the full source tarball or just the headers. If the full\nsource is downloaded, addons will have complete access to the full set of\nNode.js dependencies. However, if only the Node.js headers are downloaded,\nthen only the symbols exported by Node.js will be available.
node-gyp
can be run using the --nodedir
flag pointing at a local Node.js\nsource image. Using this option, the addon will have access to the full set of\ndependencies.
The filename extension of the compiled addon binary is .node
(as opposed\nto .dll
or .so
). The require()
function is written to look for\nfiles with the .node
file extension and initialize those as dynamically-linked\nlibraries.
When calling require()
, the .node
extension can usually be\nomitted and Node.js will still find and initialize the addon. One caveat,\nhowever, is that Node.js will first attempt to locate and load modules or\nJavaScript files that happen to share the same base name. For instance, if\nthere is a file addon.js
in the same directory as the binary addon.node
,\nthen require('addon')
will give precedence to the addon.js
file\nand load it instead.
Each of the examples illustrated in this document directly use the\nNode.js and V8 APIs for implementing addons. The V8 API can, and has, changed\ndramatically from one V8 release to the next (and one major Node.js release to\nthe next). With each change, addons may need to be updated and recompiled in\norder to continue functioning. The Node.js release schedule is designed to\nminimize the frequency and impact of such changes but there is little that\nNode.js can do to ensure stability of the V8 APIs.
\nThe Native Abstractions for Node.js (or nan
) provide a set of tools that\naddon developers are recommended to use to keep compatibility between past and\nfuture releases of V8 and Node.js. See the nan
examples for an\nillustration of how it can be used.
Node-API is an API for building native addons. It is independent from\nthe underlying JavaScript runtime (e.g. V8) and is maintained as part of\nNode.js itself. This API will be Application Binary Interface (ABI) stable\nacross versions of Node.js. It is intended to insulate addons from\nchanges in the underlying JavaScript engine and allow modules\ncompiled for one version to run on later versions of Node.js without\nrecompilation. Addons are built/packaged with the same approach/tools\noutlined in this document (node-gyp, etc.). The only difference is the\nset of APIs that are used by the native code. Instead of using the V8\nor Native Abstractions for Node.js APIs, the functions available\nin the Node-API are used.
\nCreating and maintaining an addon that benefits from the ABI stability\nprovided by Node-API carries with it certain\nimplementation considerations.
\nTo use Node-API in the above \"Hello world\" example, replace the content of\nhello.cc
with the following. All other instructions remain the same.
// hello.cc using Node-API\n#include <node_api.h>\n\nnamespace demo {\n\nnapi_value Method(napi_env env, napi_callback_info args) {\n napi_value greeting;\n napi_status status;\n\n status = napi_create_string_utf8(env, \"world\", NAPI_AUTO_LENGTH, &greeting);\n if (status != napi_ok) return nullptr;\n return greeting;\n}\n\nnapi_value init(napi_env env, napi_value exports) {\n napi_status status;\n napi_value fn;\n\n status = napi_create_function(env, nullptr, 0, Method, nullptr, &fn);\n if (status != napi_ok) return nullptr;\n\n status = napi_set_named_property(env, exports, \"hello\", fn);\n if (status != napi_ok) return nullptr;\n return exports;\n}\n\nNAPI_MODULE(NODE_GYP_MODULE_NAME, init)\n\n} // namespace demo\n
\nThe functions available and how to use them are documented in\nC/C++ addons with Node-API.
", "type": "misc", "displayName": "Node-API" }, { "textRaw": "Addon examples", "name": "addon_examples", "desc": "Following are some example addons intended to help developers get started. The\nexamples use the V8 APIs. Refer to the online V8 reference\nfor help with the various V8 calls, and V8's Embedder's Guide for an\nexplanation of several concepts used such as handles, scopes, function\ntemplates, etc.
\nEach of these examples using the following binding.gyp
file:
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [ \"addon.cc\" ]\n }\n ]\n}\n
\nIn cases where there is more than one .cc
file, simply add the additional\nfilename to the sources
array:
\"sources\": [\"addon.cc\", \"myexample.cc\"]\n
\nOnce the binding.gyp
file is ready, the example addons can be configured and\nbuilt using node-gyp
:
node-gyp configure build\n
",
"modules": [
{
"textRaw": "Function arguments",
"name": "function_arguments",
"desc": "Addons will typically expose objects and functions that can be accessed from\nJavaScript running within Node.js. When functions are invoked from JavaScript,\nthe input arguments and return value must be mapped to and from the C/C++\ncode.
\nThe following example illustrates how to read function arguments passed from\nJavaScript and how to return a result:
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Exception;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\n// This is the implementation of the \"add\" method\n// Input arguments are passed using the\n// const FunctionCallbackInfo<Value>& args struct\nvoid Add(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n // Check the number of arguments passed.\n if (args.Length() < 2) {\n // Throw an Error that is passed back to JavaScript\n isolate->ThrowException(Exception::TypeError(\n String::NewFromUtf8(isolate,\n \"Wrong number of arguments\").ToLocalChecked()));\n return;\n }\n\n // Check the argument types\n if (!args[0]->IsNumber() || !args[1]->IsNumber()) {\n isolate->ThrowException(Exception::TypeError(\n String::NewFromUtf8(isolate,\n \"Wrong arguments\").ToLocalChecked()));\n return;\n }\n\n // Perform the operation\n double value =\n args[0].As<Number>()->Value() + args[1].As<Number>()->Value();\n Local<Number> num = Number::New(isolate, value);\n\n // Set the return value (using the passed in\n // FunctionCallbackInfo<Value>&)\n args.GetReturnValue().Set(num);\n}\n\nvoid Init(Local<Object> exports) {\n NODE_SET_METHOD(exports, \"add\", Add);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\n
\nOnce compiled, the example addon can be required and used from within Node.js:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconsole.log('This should be eight:', addon.add(3, 5));\n
",
"type": "module",
"displayName": "Function arguments"
},
{
"textRaw": "Callbacks",
"name": "callbacks",
"desc": "It is common practice within addons to pass JavaScript functions to a C++\nfunction and execute them from there. The following example illustrates how\nto invoke such callbacks:
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Null;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid RunCallback(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n Local<Function> cb = Local<Function>::Cast(args[0]);\n const unsigned argc = 1;\n Local<Value> argv[argc] = {\n String::NewFromUtf8(isolate,\n \"hello world\").ToLocalChecked() };\n cb->Call(context, Null(isolate), argc, argv).ToLocalChecked();\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, \"exports\", RunCallback);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\n
\nThis example uses a two-argument form of Init()
that receives the full\nmodule
object as the second argument. This allows the addon to completely\noverwrite exports
with a single function instead of adding the function as a\nproperty of exports
.
To test it, run the following JavaScript:
\n// test.js\nconst addon = require('./build/Release/addon');\n\naddon((msg) => {\n console.log(msg);\n// Prints: 'hello world'\n});\n
\nIn this example, the callback function is invoked synchronously.
", "type": "module", "displayName": "Callbacks" }, { "textRaw": "Object factory", "name": "object_factory", "desc": "Addons can create and return new objects from within a C++ function as\nillustrated in the following example. An object is created and returned with a\nproperty msg
that echoes the string passed to createObject()
:
// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n Local<Object> obj = Object::New(isolate);\n obj->Set(context,\n String::NewFromUtf8(isolate,\n \"msg\").ToLocalChecked(),\n args[0]->ToString(context).ToLocalChecked())\n .FromJust();\n\n args.GetReturnValue().Set(obj);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, \"exports\", CreateObject);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\n
\nTo test it in JavaScript:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst obj1 = addon('hello');\nconst obj2 = addon('world');\nconsole.log(obj1.msg, obj2.msg);\n// Prints: 'hello world'\n
",
"type": "module",
"displayName": "Object factory"
},
{
"textRaw": "Function factory",
"name": "function_factory",
"desc": "Another common scenario is creating JavaScript functions that wrap C++\nfunctions and returning those back to JavaScript:
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid MyFunction(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n args.GetReturnValue().Set(String::NewFromUtf8(\n isolate, \"hello world\").ToLocalChecked());\n}\n\nvoid CreateFunction(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n Local<Context> context = isolate->GetCurrentContext();\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, MyFunction);\n Local<Function> fn = tpl->GetFunction(context).ToLocalChecked();\n\n // omit this to make it anonymous\n fn->SetName(String::NewFromUtf8(\n isolate, \"theFunction\").ToLocalChecked());\n\n args.GetReturnValue().Set(fn);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, \"exports\", CreateFunction);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\n
\nTo test:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst fn = addon();\nconsole.log(fn());\n// Prints: 'hello world'\n
",
"type": "module",
"displayName": "Function factory"
},
{
"textRaw": "Wrapping C++ objects",
"name": "wrapping_c++_objects",
"desc": "It is also possible to wrap C++ objects/classes in a way that allows new\ninstances to be created using the JavaScript new
operator:
// addon.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Local;\nusing v8::Object;\n\nvoid InitAll(Local<Object> exports) {\n MyObject::Init(exports);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, InitAll)\n\n} // namespace demo\n
\nThen, in myobject.h
, the wrapper class inherits from node::ObjectWrap
:
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Local<v8::Object> exports);\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);\n\n double value_;\n};\n\n} // namespace demo\n\n#endif\n
\nIn myobject.cc
, implement the various methods that are to be exposed.\nBelow, the method plusOne()
is exposed by adding it to the constructor's\nprototype:
// myobject.cc\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::ObjectTemplate;\nusing v8::String;\nusing v8::Value;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Local<Object> exports) {\n Isolate* isolate = exports->GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n Local<ObjectTemplate> addon_data_tpl = ObjectTemplate::New(isolate);\n addon_data_tpl->SetInternalFieldCount(1); // 1 field for the MyObject::New()\n Local<Object> addon_data =\n addon_data_tpl->NewInstance(context).ToLocalChecked();\n\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New, addon_data);\n tpl->SetClassName(String::NewFromUtf8(isolate, \"MyObject\").ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n // Prototype\n NODE_SET_PROTOTYPE_METHOD(tpl, \"plusOne\", PlusOne);\n\n Local<Function> constructor = tpl->GetFunction(context).ToLocalChecked();\n addon_data->SetInternalField(0, constructor);\n exports->Set(context, String::NewFromUtf8(\n isolate, \"MyObject\").ToLocalChecked(),\n constructor).FromJust();\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ?\n 0 : args[0]->NumberValue(context).FromMaybe(0);\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons =\n args.Data().As<Object>()->GetInternalField(0)\n .As<Value>().As<Function>();\n Local<Object> result =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n args.GetReturnValue().Set(result);\n }\n}\n\nvoid MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());\n obj->value_ += 1;\n\n args.GetReturnValue().Set(Number::New(isolate, obj->value_));\n}\n\n} // namespace demo\n
\nTo build this example, the myobject.cc
file must be added to the\nbinding.gyp
:
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [\n \"addon.cc\",\n \"myobject.cc\"\n ]\n }\n ]\n}\n
\nTest it with:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst obj = new addon.MyObject(10);\nconsole.log(obj.plusOne());\n// Prints: 11\nconsole.log(obj.plusOne());\n// Prints: 12\nconsole.log(obj.plusOne());\n// Prints: 13\n
\nThe destructor for a wrapper object will run when the object is\ngarbage-collected. For destructor testing, there are command-line flags that\ncan be used to make it possible to force garbage collection. These flags are\nprovided by the underlying V8 JavaScript engine. They are subject to change\nor removal at any time. They are not documented by Node.js or V8, and they\nshould never be used outside of testing.
\nDuring shutdown of the process or worker threads destructors are not called\nby the JS engine. Therefore it's the responsibility of the user to track\nthese objects and ensure proper destruction to avoid resource leaks.
", "type": "module", "displayName": "Wrapping C++ objects" }, { "textRaw": "Factory of wrapped objects", "name": "factory_of_wrapped_objects", "desc": "Alternatively, it is possible to use a factory pattern to avoid explicitly\ncreating object instances using the JavaScript new
operator:
const obj = addon.createObject();\n// instead of:\n// const obj = new addon.Object();\n
\nFirst, the createObject()
method is implemented in addon.cc
:
// addon.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n MyObject::NewInstance(args);\n}\n\nvoid InitAll(Local<Object> exports, Local<Object> module) {\n MyObject::Init(exports->GetIsolate());\n\n NODE_SET_METHOD(module, \"exports\", CreateObject);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, InitAll)\n\n} // namespace demo\n
\nIn myobject.h
, the static method NewInstance()
is added to handle\ninstantiating the object. This method takes the place of using new
in\nJavaScript:
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Isolate* isolate);\n static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Global<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif\n
\nThe implementation in myobject.cc
is similar to the previous example:
// myobject.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing node::AddEnvironmentCleanupHook;\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Global;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\n// Warning! This is not thread-safe, this addon cannot be used for worker\n// threads.\nGlobal<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Isolate* isolate) {\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(isolate, \"MyObject\").ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n // Prototype\n NODE_SET_PROTOTYPE_METHOD(tpl, \"plusOne\", PlusOne);\n\n Local<Context> context = isolate->GetCurrentContext();\n constructor.Reset(isolate, tpl->GetFunction(context).ToLocalChecked());\n\n AddEnvironmentCleanupHook(isolate, [](void*) {\n constructor.Reset();\n }, nullptr);\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ?\n 0 : args[0]->NumberValue(context).FromMaybe(0);\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n args.GetReturnValue().Set(instance);\n }\n}\n\nvoid MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n const unsigned argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Context> context = isolate->GetCurrentContext();\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n\n args.GetReturnValue().Set(instance);\n}\n\nvoid MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());\n obj->value_ += 1;\n\n args.GetReturnValue().Set(Number::New(isolate, obj->value_));\n}\n\n} // namespace demo\n
\nOnce again, to build this example, the myobject.cc
file must be added to the\nbinding.gyp
:
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [\n \"addon.cc\",\n \"myobject.cc\"\n ]\n }\n ]\n}\n
\nTest it with:
\n// test.js\nconst createObject = require('./build/Release/addon');\n\nconst obj = createObject(10);\nconsole.log(obj.plusOne());\n// Prints: 11\nconsole.log(obj.plusOne());\n// Prints: 12\nconsole.log(obj.plusOne());\n// Prints: 13\n\nconst obj2 = createObject(20);\nconsole.log(obj2.plusOne());\n// Prints: 21\nconsole.log(obj2.plusOne());\n// Prints: 22\nconsole.log(obj2.plusOne());\n// Prints: 23\n
",
"type": "module",
"displayName": "Factory of wrapped objects"
},
{
"textRaw": "Passing wrapped objects around",
"name": "passing_wrapped_objects_around",
"desc": "In addition to wrapping and returning C++ objects, it is possible to pass\nwrapped objects around by unwrapping them with the Node.js helper function\nnode::ObjectWrap::Unwrap
. The following examples shows a function add()
\nthat can take two MyObject
objects as input arguments:
// addon.cc\n#include <node.h>\n#include <node_object_wrap.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n MyObject::NewInstance(args);\n}\n\nvoid Add(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n MyObject* obj1 = node::ObjectWrap::Unwrap<MyObject>(\n args[0]->ToObject(context).ToLocalChecked());\n MyObject* obj2 = node::ObjectWrap::Unwrap<MyObject>(\n args[1]->ToObject(context).ToLocalChecked());\n\n double sum = obj1->value() + obj2->value();\n args.GetReturnValue().Set(Number::New(isolate, sum));\n}\n\nvoid InitAll(Local<Object> exports) {\n MyObject::Init(exports->GetIsolate());\n\n NODE_SET_METHOD(exports, \"createObject\", CreateObject);\n NODE_SET_METHOD(exports, \"add\", Add);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, InitAll)\n\n} // namespace demo\n
\nIn myobject.h
, a new public method is added to allow access to private values\nafter unwrapping the object.
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Isolate* isolate);\n static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);\n inline double value() const { return value_; }\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Global<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif\n
\nThe implementation of myobject.cc
is similar to before:
// myobject.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing node::AddEnvironmentCleanupHook;\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Global;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\n// Warning! This is not thread-safe, this addon cannot be used for worker\n// threads.\nGlobal<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Isolate* isolate) {\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(isolate, \"MyObject\").ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n Local<Context> context = isolate->GetCurrentContext();\n constructor.Reset(isolate, tpl->GetFunction(context).ToLocalChecked());\n\n AddEnvironmentCleanupHook(isolate, [](void*) {\n constructor.Reset();\n }, nullptr);\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ?\n 0 : args[0]->NumberValue(context).FromMaybe(0);\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n args.GetReturnValue().Set(instance);\n }\n}\n\nvoid MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n const unsigned argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Context> context = isolate->GetCurrentContext();\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n\n args.GetReturnValue().Set(instance);\n}\n\n} // namespace demo\n
\nTest it with:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst obj1 = addon.createObject(10);\nconst obj2 = addon.createObject(20);\nconst result = addon.add(obj1, obj2);\n\nconsole.log(result);\n// Prints: 30\n
",
"type": "module",
"displayName": "Passing wrapped objects around"
}
],
"type": "misc",
"displayName": "Addon examples"
}
],
"source": "doc/api/addons.md"
},
{
"textRaw": "Node-API",
"name": "Node-API",
"introduced_in": "v8.0.0",
"type": "misc",
"stability": 2,
"stabilityText": "Stable",
"desc": "Node-API (formerly N-API) is an API for building native Addons. It is\nindependent from the underlying JavaScript runtime (for example, V8) and is\nmaintained as part of Node.js itself. This API will be Application Binary\nInterface (ABI) stable across versions of Node.js. It is intended to insulate\naddons from changes in the underlying JavaScript engine and allow modules\ncompiled for one major version to run on later major versions of Node.js without\nrecompilation. The ABI Stability guide provides a more in-depth explanation.
\nAddons are built/packaged with the same approach/tools outlined in the section\ntitled C++ Addons. The only difference is the set of APIs that are used by\nthe native code. Instead of using the V8 or Native Abstractions for Node.js\nAPIs, the functions available in Node-API are used.
\nAPIs exposed by Node-API are generally used to create and manipulate\nJavaScript values. Concepts and operations generally map to ideas specified\nin the ECMA-262 Language Specification. The APIs have the following\nproperties:
\nnapi_status
. This\nstatus indicates whether the API call succeeded or failed.napi_value
.napi_get_last_error_info
. More information can be found in the error\nhandling section Error handling.Node-API is a C API that ensures ABI stability across Node.js versions\nand different compiler levels. A C++ API can be easier to use.\nTo support using C++, the project maintains a\nC++ wrapper module called node-addon-api
.\nThis wrapper provides an inlinable C++ API. Binaries built\nwith node-addon-api
will depend on the symbols for the Node-API C-based\nfunctions exported by Node.js. node-addon-api
is a more\nefficient way to write code that calls Node-API. Take, for example, the\nfollowing node-addon-api
code. The first section shows the\nnode-addon-api
code and the second section shows what actually gets\nused in the addon.
Object obj = Object::New(env);\nobj[\"foo\"] = String::New(env, \"bar\");\n
\nnapi_status status;\nnapi_value object, string;\nstatus = napi_create_object(env, &object);\nif (status != napi_ok) {\n napi_throw_error(env, ...);\n return;\n}\n\nstatus = napi_create_string_utf8(env, \"bar\", NAPI_AUTO_LENGTH, &string);\nif (status != napi_ok) {\n napi_throw_error(env, ...);\n return;\n}\n\nstatus = napi_set_named_property(env, object, \"foo\", string);\nif (status != napi_ok) {\n napi_throw_error(env, ...);\n return;\n}\n
\nThe end result is that the addon only uses the exported C APIs. As a result,\nit still gets the benefits of the ABI stability provided by the C API.
\nWhen using node-addon-api
instead of the C APIs, start with the API docs\nfor node-addon-api
.
The Node-API Resource offers\nan excellent orientation and tips for developers just getting started with\nNode-API and node-addon-api
. Additional media resources can be found on the\nNode-API Media page.
Although Node-API provides an ABI stability guarantee, other parts of Node.js do\nnot, and any external libraries used from the addon may not. In particular,\nnone of the following APIs provide an ABI stability guarantee across major\nversions:
\nthe Node.js C++ APIs available via any of
\n#include <node.h>\n#include <node_buffer.h>\n#include <node_version.h>\n#include <node_object_wrap.h>\n
\nthe libuv APIs which are also included with Node.js and available via
\n#include <uv.h>\n
\nthe V8 API available via
\n#include <v8.h>\n
\nThus, for an addon to remain ABI-compatible across Node.js major versions, it\nmust use Node-API exclusively by restricting itself to using
\n#include <node_api.h>\n
\nand by checking, for all external libraries that it uses, that the external\nlibrary makes ABI stability guarantees similar to Node-API.
", "type": "misc", "displayName": "Implications of ABI stability" }, { "textRaw": "Building", "name": "building", "desc": "Unlike modules written in JavaScript, developing and deploying Node.js\nnative addons using Node-API requires an additional set of tools. Besides the\nbasic tools required to develop for Node.js, the native addon developer\nrequires a toolchain that can compile C and C++ code into a binary. In\naddition, depending upon how the native addon is deployed, the user of\nthe native addon will also need to have a C/C++ toolchain installed.
\nFor Linux developers, the necessary C/C++ toolchain packages are readily\navailable. GCC is widely used in the Node.js community to build and\ntest across a variety of platforms. For many developers, the LLVM\ncompiler infrastructure is also a good choice.
\nFor Mac developers, Xcode offers all the required compiler tools.\nHowever, it is not necessary to install the entire Xcode IDE. The following\ncommand installs the necessary toolchain:
\nxcode-select --install\n
\nFor Windows developers, Visual Studio offers all the required compiler\ntools. However, it is not necessary to install the entire Visual Studio\nIDE. The following command installs the necessary toolchain:
\nnpm install --global windows-build-tools\n
\nThe sections below describe the additional tools available for developing\nand deploying Node.js native addons.
", "modules": [ { "textRaw": "Build tools", "name": "build_tools", "desc": "Both the tools listed here require that users of the native\naddon have a C/C++ toolchain installed in order to successfully install\nthe native addon.
", "modules": [ { "textRaw": "node-gyp", "name": "node-gyp", "desc": "node-gyp is a build system based on the gyp-next fork of\nGoogle's GYP tool and comes bundled with npm. GYP, and therefore node-gyp,\nrequires that Python be installed.
\nHistorically, node-gyp has been the tool of choice for building native\naddons. It has widespread adoption and documentation. However, some\ndevelopers have run into limitations in node-gyp.
", "type": "module", "displayName": "node-gyp" } ], "properties": [ { "textRaw": "CMake.js", "name": "js", "desc": "CMake.js is an alternative build system based on CMake.
\nCMake.js is a good choice for projects that already use CMake or for\ndevelopers affected by limitations in node-gyp. build_with_cmake
is an\nexample of a CMake-based native addon project.
The three tools listed here permit native addon developers and maintainers\nto create and upload binaries to public or private servers. These tools are\ntypically integrated with CI/CD build systems like Travis CI and\nAppVeyor to build and upload binaries for a variety of platforms and\narchitectures. These binaries are then available for download by users who\ndo not need to have a C/C++ toolchain installed.
", "modules": [ { "textRaw": "node-pre-gyp", "name": "node-pre-gyp", "desc": "node-pre-gyp is a tool based on node-gyp that adds the ability to\nupload binaries to a server of the developer's choice. node-pre-gyp has\nparticularly good support for uploading binaries to Amazon S3.
", "type": "module", "displayName": "node-pre-gyp" }, { "textRaw": "prebuild", "name": "prebuild", "desc": "prebuild is a tool that supports builds using either node-gyp or\nCMake.js. Unlike node-pre-gyp which supports a variety of servers, prebuild\nuploads binaries only to GitHub releases. prebuild is a good choice for\nGitHub projects using CMake.js.
", "type": "module", "displayName": "prebuild" }, { "textRaw": "prebuildify", "name": "prebuildify", "desc": "prebuildify is a tool based on node-gyp. The advantage of prebuildify is\nthat the built binaries are bundled with the native addon when it's\nuploaded to npm. The binaries are downloaded from npm and are immediately\navailable to the module user when the native addon is installed.
", "type": "module", "displayName": "prebuildify" } ], "type": "module", "displayName": "Uploading precompiled binaries" } ], "type": "misc", "displayName": "Building" }, { "textRaw": "Usage", "name": "usage", "desc": "In order to use the Node-API functions, include the file node_api.h
which\nis located in the src directory in the node development tree:
#include <node_api.h>\n
\nThis will opt into the default NAPI_VERSION
for the given release of Node.js.\nIn order to ensure compatibility with specific versions of Node-API, the version\ncan be specified explicitly when including the header:
#define NAPI_VERSION 3\n#include <node_api.h>\n
\nThis restricts the Node-API surface to just the functionality that was available\nin the specified (and earlier) versions.
\nSome of the Node-API surface is experimental and requires explicit opt-in:
\n#define NAPI_EXPERIMENTAL\n#include <node_api.h>\n
\nIn this case the entire API surface, including any experimental APIs, will be\navailable to the module code.
\nOccasionally, experimental features are introduced that affect already-released\nand stable APIs. These features can be disabled by an opt-out:
\n#define NAPI_EXPERIMENTAL\n#define NODE_API_EXPERIMENTAL_<FEATURE_NAME>_OPT_OUT\n#include <node_api.h>\n
\nwhere <FEATURE_NAME>
is the name of an experimental feature that affects both\nexperimental and stable APIs.
Up until version 9, Node-API versions were additive and versioned\nindependently from Node.js. This meant that any version was\nan extension to the previous version in that it had all of\nthe APIs from the previous version with some additions. Each\nNode.js version only supported a single Node-API version.\nFor example v18.15.0 supports only Node-API version 8. ABI stability was\nachieved because 8 was a strict superset of all previous versions.
\nAs of version 9, while Node-API versions continue to be versioned\nindependently an add-on that ran with Node-API version 9 may need\ncode updates to run with Node-API version 10. ABI stability\nis maintained, however, because Node.js versions that support\nNode-API versions higher than 8 will support all versions\nbetween 8 and the highest version they support and will default\nto providing the version 8 APIs unless an add-on opts into a\nhigher Node-API version. This approach provides the flexibility\nof better optimizing existing Node-API functions while\nmaintaining ABI stability. Existing add-ons can continue to run without\nrecompilation using an earlier version of Node-API. If an add-on\nneeds functionality from a newer Node-API version, changes to existing\ncode and recompilation will be needed to use those new functions anyway.
\nIn versions of Node.js that support Node-API version 9 and later, defining\nNAPI_VERSION=X
and using the existing add-on initialization macros\nwill bake in the requested Node-API version that will be used at runtime\ninto the add-on. If NAPI_VERSION
is not set it will default to 8.
This table may not be up to date in older streams, the most up to date\ninformation is in the latest API documentation in:\nNode-API version matrix
\n\nNode-API version | \nSupported In | \n
---|---|
9 | \nv18.17.0+, 20.3.0+, 21.0.0 and all later versions | \n
8 | \nv12.22.0+, v14.17.0+, v15.12.0+, 16.0.0 and all later versions | \n
7 | \nv10.23.0+, v12.19.0+, v14.12.0+, 15.0.0 and all later versions | \n
6 | \nv10.20.0+, v12.17.0+, 14.0.0 and all later versions | \n
5 | \nv10.17.0+, v12.11.0+, 13.0.0 and all later versions | \n
4 | \nv10.16.0+, v11.8.0+, 12.0.0 and all later versions | \n
3 | \nv6.14.2*, 8.11.2+, v9.11.0+*, 10.0.0 and all later versions | \n
2 | \nv8.10.0+*, v9.3.0+*, 10.0.0 and all later versions | \n
1 | \nv8.6.0+**, v9.0.0+*, 10.0.0 and all later versions | \n
* Node-API was experimental.
\n** Node.js 8.0.0 included Node-API as experimental. It was released as\nNode-API version 1 but continued to evolve until Node.js 8.6.0. The API is\ndifferent in versions prior to Node.js 8.6.0. We recommend Node-API version 3 or\nlater.
\nEach API documented for Node-API will have a header named added in:
, and APIs\nwhich are stable will have the additional header Node-API version:
.\nAPIs are directly usable when using a Node.js version which supports\nthe Node-API version shown in Node-API version:
or higher.\nWhen using a Node.js version that does not support the\nNode-API version:
listed or if there is no Node-API version:
listed,\nthen the API will only be available if\n#define NAPI_EXPERIMENTAL
precedes the inclusion of node_api.h
\nor js_native_api.h
. If an API appears not to be available on\na version of Node.js which is later than the one shown in added in:
then\nthis is most likely the reason for the apparent absence.
The Node-APIs associated strictly with accessing ECMAScript features from native\ncode can be found separately in js_native_api.h
and js_native_api_types.h
.\nThe APIs defined in these headers are included in node_api.h
and\nnode_api_types.h
. The headers are structured in this way in order to allow\nimplementations of Node-API outside of Node.js. For those implementations the\nNode.js specific APIs may not be applicable.
The Node.js-specific parts of an addon can be separated from the code that\nexposes the actual functionality to the JavaScript environment so that the\nlatter may be used with multiple implementations of Node-API. In the example\nbelow, addon.c
and addon.h
refer only to js_native_api.h
. This ensures\nthat addon.c
can be reused to compile against either the Node.js\nimplementation of Node-API or any implementation of Node-API outside of Node.js.
addon_node.c
is a separate file that contains the Node.js specific entry point\nto the addon and which instantiates the addon by calling into addon.c
when the\naddon is loaded into a Node.js environment.
// addon.h\n#ifndef _ADDON_H_\n#define _ADDON_H_\n#include <js_native_api.h>\nnapi_value create_addon(napi_env env);\n#endif // _ADDON_H_\n
\n// addon.c\n#include \"addon.h\"\n\n#define NODE_API_CALL(env, call) \\\n do { \\\n napi_status status = (call); \\\n if (status != napi_ok) { \\\n const napi_extended_error_info* error_info = NULL; \\\n napi_get_last_error_info((env), &error_info); \\\n const char* err_message = error_info->error_message; \\\n bool is_pending; \\\n napi_is_exception_pending((env), &is_pending); \\\n /* If an exception is already pending, don't rethrow it */ \\\n if (!is_pending) { \\\n const char* message = (err_message == NULL) \\\n ? \"empty error message\" \\\n : err_message; \\\n napi_throw_error((env), NULL, message); \\\n } \\\n return NULL; \\\n } \\\n } while(0)\n\nstatic napi_value\nDoSomethingUseful(napi_env env, napi_callback_info info) {\n // Do something useful.\n return NULL;\n}\n\nnapi_value create_addon(napi_env env) {\n napi_value result;\n NODE_API_CALL(env, napi_create_object(env, &result));\n\n napi_value exported_function;\n NODE_API_CALL(env, napi_create_function(env,\n \"doSomethingUseful\",\n NAPI_AUTO_LENGTH,\n DoSomethingUseful,\n NULL,\n &exported_function));\n\n NODE_API_CALL(env, napi_set_named_property(env,\n result,\n \"doSomethingUseful\",\n exported_function));\n\n return result;\n}\n
\n// addon_node.c\n#include <node_api.h>\n#include \"addon.h\"\n\nNAPI_MODULE_INIT(/* napi_env env, napi_value exports */) {\n // This function body is expected to return a `napi_value`.\n // The variables `napi_env env` and `napi_value exports` may be used within\n // the body, as they are provided by the definition of `NAPI_MODULE_INIT()`.\n return create_addon(env);\n}\n
",
"type": "misc",
"displayName": "Node-API version matrix"
},
{
"textRaw": "Environment life cycle APIs",
"name": "environment_life_cycle_apis",
"desc": "Section 8.7 of the ECMAScript Language Specification defines the concept\nof an \"Agent\" as a self-contained environment in which JavaScript code runs.\nMultiple such Agents may be started and terminated either concurrently or in\nsequence by the process.
\nA Node.js environment corresponds to an ECMAScript Agent. In the main process,\nan environment is created at startup, and additional environments can be created\non separate threads to serve as worker threads. When Node.js is embedded in\nanother application, the main thread of the application may also construct and\ndestroy a Node.js environment multiple times during the life cycle of the\napplication process such that each Node.js environment created by the\napplication may, in turn, during its life cycle create and destroy additional\nenvironments as worker threads.
\nFrom the perspective of a native addon this means that the bindings it provides\nmay be called multiple times, from multiple contexts, and even concurrently from\nmultiple threads.
\nNative addons may need to allocate global state which they use during\ntheir life cycle of an Node.js environment such that the state can be\nunique to each instance of the addon.
\nTo this end, Node-API provides a way to associate data such that its life cycle\nis tied to the life cycle of a Node.js environment.
", "modules": [ { "textRaw": "`napi_set_instance_data`", "name": "`napi_set_instance_data`", "meta": { "added": [ "v12.8.0", "v10.20.0" ], "napiVersion": [ 6 ], "changes": [] }, "desc": "napi_status napi_set_instance_data(node_api_nogc_env env,\n void* data,\n napi_finalize finalize_cb,\n void* finalize_hint);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] data
: The data item to make available to bindings of this instance.[in] finalize_cb
: The function to call when the environment is being torn\ndown. The function receives data
so that it might free it.\nnapi_finalize
provides more details.[in] finalize_hint
: Optional hint to pass to the finalize callback during\ncollection.Returns napi_ok
if the API succeeded.
This API associates data
with the currently running Node.js environment. data
\ncan later be retrieved using napi_get_instance_data()
. Any existing data\nassociated with the currently running Node.js environment which was set by means\nof a previous call to napi_set_instance_data()
will be overwritten. If a\nfinalize_cb
was provided by the previous call, it will not be called.
napi_status napi_get_instance_data(node_api_nogc_env env,\n void** data);\n
\n[in] env
: The environment that the Node-API call is invoked under.[out] data
: The data item that was previously associated with the currently\nrunning Node.js environment by a call to napi_set_instance_data()
.Returns napi_ok
if the API succeeded.
This API retrieves data that was previously associated with the currently\nrunning Node.js environment via napi_set_instance_data()
. If no data is set,\nthe call will succeed and data
will be set to NULL
.
Node-API exposes the following fundamental data types as abstractions that are\nconsumed by the various APIs. These APIs should be treated as opaque,\nintrospectable only with other Node-API calls.
", "modules": [ { "textRaw": "`napi_status`", "name": "`napi_status`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "Integral status code indicating the success or failure of a Node-API call.\nCurrently, the following status codes are supported.
\ntypedef enum {\n napi_ok,\n napi_invalid_arg,\n napi_object_expected,\n napi_string_expected,\n napi_name_expected,\n napi_function_expected,\n napi_number_expected,\n napi_boolean_expected,\n napi_array_expected,\n napi_generic_failure,\n napi_pending_exception,\n napi_cancelled,\n napi_escape_called_twice,\n napi_handle_scope_mismatch,\n napi_callback_scope_mismatch,\n napi_queue_full,\n napi_closing,\n napi_bigint_expected,\n napi_date_expected,\n napi_arraybuffer_expected,\n napi_detachable_arraybuffer_expected,\n napi_would_deadlock, /* unused */\n napi_no_external_buffers_allowed,\n napi_cannot_run_js\n} napi_status;\n
\nIf additional information is required upon an API returning a failed status,\nit can be obtained by calling napi_get_last_error_info
.
typedef struct {\n const char* error_message;\n void* engine_reserved;\n uint32_t engine_error_code;\n napi_status error_code;\n} napi_extended_error_info;\n
\nerror_message
: UTF8-encoded string containing a VM-neutral description of\nthe error.engine_reserved
: Reserved for VM-specific error details. This is currently\nnot implemented for any VM.engine_error_code
: VM-specific error code. This is currently\nnot implemented for any VM.error_code
: The Node-API status code that originated with the last error.See the Error handling section for additional information.
", "type": "module", "displayName": "`napi_extended_error_info`" }, { "textRaw": "`napi_env`", "name": "`napi_env`", "desc": "napi_env
is used to represent a context that the underlying Node-API\nimplementation can use to persist VM-specific state. This structure is passed\nto native functions when they're invoked, and it must be passed back when\nmaking Node-API calls. Specifically, the same napi_env
that was passed in when\nthe initial native function was called must be passed to any subsequent\nnested Node-API calls. Caching the napi_env
for the purpose of general reuse,\nand passing the napi_env
between instances of the same addon running on\ndifferent Worker
threads is not allowed. The napi_env
becomes invalid\nwhen an instance of a native addon is unloaded. Notification of this event is\ndelivered through the callbacks given to napi_add_env_cleanup_hook
and\nnapi_set_instance_data
.
This variant of napi_env
is passed to synchronous finalizers\n(node_api_nogc_finalize
). There is a subset of Node-APIs which accept\na parameter of type node_api_nogc_env
as their first argument. These APIs do\nnot access the state of the JavaScript engine and are thus safe to call from\nsynchronous finalizers. Passing a parameter of type napi_env
to these APIs is\nallowed, however, passing a parameter of type node_api_nogc_env
to APIs that\naccess the JavaScript engine state is not allowed. Attempting to do so without\na cast will produce a compiler warning or an error when add-ons are compiled\nwith flags which cause them to emit warnings and/or errors when incorrect\npointer types are passed into a function. Calling such APIs from a synchronous\nfinalizer will ultimately result in the termination of the application.
This is an opaque pointer that is used to represent a JavaScript value.
", "type": "module", "displayName": "`napi_value`" }, { "textRaw": "`napi_threadsafe_function`", "name": "`napi_threadsafe_function`", "meta": { "added": [ "v10.6.0" ], "napiVersion": [ 4 ], "changes": [] }, "desc": "This is an opaque pointer that represents a JavaScript function which can be\ncalled asynchronously from multiple threads via\nnapi_call_threadsafe_function()
.
A value to be given to napi_release_threadsafe_function()
to indicate whether\nthe thread-safe function is to be closed immediately (napi_tsfn_abort
) or\nmerely released (napi_tsfn_release
) and thus available for subsequent use via\nnapi_acquire_threadsafe_function()
and napi_call_threadsafe_function()
.
typedef enum {\n napi_tsfn_release,\n napi_tsfn_abort\n} napi_threadsafe_function_release_mode;\n
",
"type": "module",
"displayName": "`napi_threadsafe_function_release_mode`"
},
{
"textRaw": "`napi_threadsafe_function_call_mode`",
"name": "`napi_threadsafe_function_call_mode`",
"meta": {
"added": [
"v10.6.0"
],
"napiVersion": [
4
],
"changes": []
},
"desc": "A value to be given to napi_call_threadsafe_function()
to indicate whether\nthe call should block whenever the queue associated with the thread-safe\nfunction is full.
typedef enum {\n napi_tsfn_nonblocking,\n napi_tsfn_blocking\n} napi_threadsafe_function_call_mode;\n
",
"type": "module",
"displayName": "`napi_threadsafe_function_call_mode`"
},
{
"textRaw": "Node-API memory management types",
"name": "node-api_memory_management_types",
"modules": [
{
"textRaw": "`napi_handle_scope`",
"name": "`napi_handle_scope`",
"desc": "This is an abstraction used to control and modify the lifetime of objects\ncreated within a particular scope. In general, Node-API values are created\nwithin the context of a handle scope. When a native method is called from\nJavaScript, a default handle scope will exist. If the user does not explicitly\ncreate a new handle scope, Node-API values will be created in the default handle\nscope. For any invocations of code outside the execution of a native method\n(for instance, during a libuv callback invocation), the module is required to\ncreate a scope before invoking any functions that can result in the creation\nof JavaScript values.
\nHandle scopes are created using napi_open_handle_scope
and are destroyed\nusing napi_close_handle_scope
. Closing the scope can indicate to the GC\nthat all napi_value
s created during the lifetime of the handle scope are no\nlonger referenced from the current stack frame.
For more details, review the Object lifetime management.
", "type": "module", "displayName": "`napi_handle_scope`" }, { "textRaw": "`napi_escapable_handle_scope`", "name": "`napi_escapable_handle_scope`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "Escapable handle scopes are a special type of handle scope to return values\ncreated within a particular handle scope to a parent scope.
", "type": "module", "displayName": "`napi_escapable_handle_scope`" }, { "textRaw": "`napi_ref`", "name": "`napi_ref`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "This is the abstraction to use to reference a napi_value
. This allows for\nusers to manage the lifetimes of JavaScript values, including defining their\nminimum lifetimes explicitly.
For more details, review the Object lifetime management.
", "type": "module", "displayName": "`napi_ref`" }, { "textRaw": "`napi_type_tag`", "name": "`napi_type_tag`", "meta": { "added": [ "v14.8.0", "v12.19.0" ], "napiVersion": [ 8 ], "changes": [] }, "desc": "A 128-bit value stored as two unsigned 64-bit integers. It serves as a UUID\nwith which JavaScript objects or externals can be \"tagged\" in order to\nensure that they are of a certain type. This is a stronger check than\nnapi_instanceof
, because the latter can report a false positive if the\nobject's prototype has been manipulated. Type-tagging is most useful in\nconjunction with napi_wrap
because it ensures that the pointer retrieved\nfrom a wrapped object can be safely cast to the native type corresponding to the\ntype tag that had been previously applied to the JavaScript object.
typedef struct {\n uint64_t lower;\n uint64_t upper;\n} napi_type_tag;\n
",
"type": "module",
"displayName": "`napi_type_tag`"
},
{
"textRaw": "`napi_async_cleanup_hook_handle`",
"name": "`napi_async_cleanup_hook_handle`",
"meta": {
"added": [
"v14.10.0",
"v12.19.0"
],
"changes": []
},
"desc": "An opaque value returned by napi_add_async_cleanup_hook
. It must be passed\nto napi_remove_async_cleanup_hook
when the chain of asynchronous cleanup\nevents completes.
Opaque datatype that is passed to a callback function. It can be used for\ngetting additional information about the context in which the callback was\ninvoked.
", "type": "module", "displayName": "`napi_callback_info`" }, { "textRaw": "`napi_callback`", "name": "`napi_callback`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "Function pointer type for user-provided native functions which are to be\nexposed to JavaScript via Node-API. Callback functions should satisfy the\nfollowing signature:
\ntypedef napi_value (*napi_callback)(napi_env, napi_callback_info);\n
\nUnless for reasons discussed in Object Lifetime Management, creating a\nhandle and/or callback scope inside a napi_callback
is not necessary.
Function pointer type for add-on provided functions that allow the user to be\nnotified when externally-owned data is ready to be cleaned up because the\nobject it was associated with has been garbage-collected. The user must provide\na function satisfying the following signature which would get called upon the\nobject's collection. Currently, node_api_nogc_finalize
can be used for\nfinding out when objects that have external data are collected.
typedef void (*node_api_nogc_finalize)(node_api_nogc_env env,\n void* finalize_data,\n void* finalize_hint);\n
\nUnless for reasons discussed in Object Lifetime Management, creating a\nhandle and/or callback scope inside the function body is not necessary.
\nSince these functions may be called while the JavaScript engine is in a state\nwhere it cannot execute JavaScript code, only Node-APIs which accept a\nnode_api_nogc_env
as their first parameter may be called.\nnode_api_post_finalizer
can be used to schedule Node-API calls that\nrequire access to the JavaScript engine's state to run after the current\ngarbage collection cycle has completed.
In the case of node_api_create_external_string_latin1
and\nnode_api_create_external_string_utf16
the env
parameter may be null,\nbecause external strings can be collected during the latter part of environment\nshutdown.
Change History:
\nexperimental (NAPI_EXPERIMENTAL
):
Only Node-API calls that accept a node_api_nogc_env
as their first\nparameter may be called, otherwise the application will be terminated with an\nappropriate error message. This feature can be turned off by defining\nNODE_API_EXPERIMENTAL_NOGC_ENV_OPT_OUT
.
Function pointer type for add-on provided function that allow the user to\nschedule a group of calls to Node-APIs in response to a garbage collection\nevent, after the garbage collection cycle has completed. These function\npointers can be used with node_api_post_finalizer
.
typedef void (*napi_finalize)(napi_env env,\n void* finalize_data,\n void* finalize_hint);\n
\nChange History:
\nexperimental (NAPI_EXPERIMENTAL
is defined):
A function of this type may no longer be used as a finalizer, except with\nnode_api_post_finalizer
. node_api_nogc_finalize
must be used\ninstead. This feature can be turned off by defining\nNODE_API_EXPERIMENTAL_NOGC_ENV_OPT_OUT
.
Function pointer used with functions that support asynchronous\noperations. Callback functions must satisfy the following signature:
\ntypedef void (*napi_async_execute_callback)(napi_env env, void* data);\n
\nImplementations of this function must avoid making Node-API calls that execute\nJavaScript or interact with JavaScript objects. Node-API calls should be in the\nnapi_async_complete_callback
instead. Do not use the napi_env
parameter as\nit will likely result in execution of JavaScript.
Function pointer used with functions that support asynchronous\noperations. Callback functions must satisfy the following signature:
\ntypedef void (*napi_async_complete_callback)(napi_env env,\n napi_status status,\n void* data);\n
\nUnless for reasons discussed in Object Lifetime Management, creating a\nhandle and/or callback scope inside the function body is not necessary.
", "type": "module", "displayName": "`napi_async_complete_callback`" }, { "textRaw": "`napi_threadsafe_function_call_js`", "name": "`napi_threadsafe_function_call_js`", "meta": { "added": [ "v10.6.0" ], "napiVersion": [ 4 ], "changes": [] }, "desc": "Function pointer used with asynchronous thread-safe function calls. The callback\nwill be called on the main thread. Its purpose is to use a data item arriving\nvia the queue from one of the secondary threads to construct the parameters\nnecessary for a call into JavaScript, usually via napi_call_function
, and then\nmake the call into JavaScript.
The data arriving from the secondary thread via the queue is given in the data
\nparameter and the JavaScript function to call is given in the js_callback
\nparameter.
Node-API sets up the environment prior to calling this callback, so it is\nsufficient to call the JavaScript function via napi_call_function
rather than\nvia napi_make_callback
.
Callback functions must satisfy the following signature:
\ntypedef void (*napi_threadsafe_function_call_js)(napi_env env,\n napi_value js_callback,\n void* context,\n void* data);\n
\n[in] env
: The environment to use for API calls, or NULL
if the thread-safe\nfunction is being torn down and data
may need to be freed.[in] js_callback
: The JavaScript function to call, or NULL
if the\nthread-safe function is being torn down and data
may need to be freed. It\nmay also be NULL
if the thread-safe function was created without\njs_callback
.[in] context
: The optional data with which the thread-safe function was\ncreated.[in] data
: Data created by the secondary thread. It is the responsibility of\nthe callback to convert this native data to JavaScript values (with Node-API\nfunctions) that can be passed as parameters when js_callback
is invoked.\nThis pointer is managed entirely by the threads and this callback. Thus this\ncallback should free the data.Unless for reasons discussed in Object Lifetime Management, creating a\nhandle and/or callback scope inside the function body is not necessary.
", "type": "module", "displayName": "`napi_threadsafe_function_call_js`" }, { "textRaw": "`napi_cleanup_hook`", "name": "`napi_cleanup_hook`", "meta": { "added": [ "v19.2.0", "v18.13.0" ], "napiVersion": [ 3 ], "changes": [] }, "desc": "Function pointer used with napi_add_env_cleanup_hook
. It will be called\nwhen the environment is being torn down.
Callback functions must satisfy the following signature:
\ntypedef void (*napi_cleanup_hook)(void* data);\n
\n[in] data
: The data that was passed to napi_add_env_cleanup_hook
.Function pointer used with napi_add_async_cleanup_hook
. It will be called\nwhen the environment is being torn down.
Callback functions must satisfy the following signature:
\ntypedef void (*napi_async_cleanup_hook)(napi_async_cleanup_hook_handle handle,\n void* data);\n
\n[in] handle
: The handle that must be passed to\nnapi_remove_async_cleanup_hook
after completion of the asynchronous\ncleanup.[in] data
: The data that was passed to napi_add_async_cleanup_hook
.The body of the function should initiate the asynchronous cleanup actions at the\nend of which handle
must be passed in a call to\nnapi_remove_async_cleanup_hook
.
Node-API uses both return values and JavaScript exceptions for error handling.\nThe following sections explain the approach for each case.
", "modules": [ { "textRaw": "Return values", "name": "return_values", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "All of the Node-API functions share the same error handling pattern. The\nreturn type of all API functions is napi_status
.
The return value will be napi_ok
if the request was successful and\nno uncaught JavaScript exception was thrown. If an error occurred AND\nan exception was thrown, the napi_status
value for the error\nwill be returned. If an exception was thrown, and no error occurred,\nnapi_pending_exception
will be returned.
In cases where a return value other than napi_ok
or\nnapi_pending_exception
is returned, napi_is_exception_pending
\nmust be called to check if an exception is pending.\nSee the section on exceptions for more details.
The full set of possible napi_status
values is defined\nin napi_api_types.h
.
The napi_status
return value provides a VM-independent representation of\nthe error which occurred. In some cases it is useful to be able to get\nmore detailed information, including a string representing the error as well as\nVM (engine)-specific information.
In order to retrieve this information napi_get_last_error_info
\nis provided which returns a napi_extended_error_info
structure.\nThe format of the napi_extended_error_info
structure is as follows:
typedef struct napi_extended_error_info {\n const char* error_message;\n void* engine_reserved;\n uint32_t engine_error_code;\n napi_status error_code;\n};\n
\nerror_message
: Textual representation of the error that occurred.engine_reserved
: Opaque handle reserved for engine use only.engine_error_code
: VM specific error code.error_code
: Node-API status code for the last error.napi_get_last_error_info
returns the information for the last\nNode-API call that was made.
Do not rely on the content or format of any of the extended information as it\nis not subject to SemVer and may change at any time. It is intended only for\nlogging purposes.
", "modules": [ { "textRaw": "`napi_get_last_error_info`", "name": "`napi_get_last_error_info`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status\nnapi_get_last_error_info(node_api_nogc_env env,\n const napi_extended_error_info** result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: The napi_extended_error_info
structure with more\ninformation about the error.Returns napi_ok
if the API succeeded.
This API retrieves a napi_extended_error_info
structure with information\nabout the last error that occurred.
The content of the napi_extended_error_info
returned is only valid up until\na Node-API function is called on the same env
. This includes a call to\nnapi_is_exception_pending
so it may often be necessary to make a copy\nof the information so that it can be used later. The pointer returned\nin error_message
points to a statically-defined string so it is safe to use\nthat pointer if you have copied it out of the error_message
field (which will\nbe overwritten) before another Node-API function was called.
Do not rely on the content or format of any of the extended information as it\nis not subject to SemVer and may change at any time. It is intended only for\nlogging purposes.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_get_last_error_info`" } ], "type": "module", "displayName": "Return values" }, { "textRaw": "Exceptions", "name": "exceptions", "desc": "Any Node-API function call may result in a pending JavaScript exception. This is\nthe case for any of the API functions, even those that may not cause the\nexecution of JavaScript.
\nIf the napi_status
returned by a function is napi_ok
then no\nexception is pending and no additional action is required. If the\nnapi_status
returned is anything other than napi_ok
or\nnapi_pending_exception
, in order to try to recover and continue\ninstead of simply returning immediately, napi_is_exception_pending
\nmust be called in order to determine if an exception is pending or not.
In many cases when a Node-API function is called and an exception is\nalready pending, the function will return immediately with a\nnapi_status
of napi_pending_exception
. However, this is not the case\nfor all functions. Node-API allows a subset of the functions to be\ncalled to allow for some minimal cleanup before returning to JavaScript.\nIn that case, napi_status
will reflect the status for the function. It\nwill not reflect previous pending exceptions. To avoid confusion, check\nthe error status after every function call.
When an exception is pending one of two approaches can be employed.
\nThe first approach is to do any appropriate cleanup and then return so that\nexecution will return to JavaScript. As part of the transition back to\nJavaScript, the exception will be thrown at the point in the JavaScript\ncode where the native method was invoked. The behavior of most Node-API calls\nis unspecified while an exception is pending, and many will simply return\nnapi_pending_exception
, so do as little as possible and then return to\nJavaScript where the exception can be handled.
The second approach is to try to handle the exception. There will be cases\nwhere the native code can catch the exception, take the appropriate action,\nand then continue. This is only recommended in specific cases\nwhere it is known that the exception can be safely handled. In these\ncases napi_get_and_clear_last_exception
can be used to get and\nclear the exception. On success, result will contain the handle to\nthe last JavaScript Object
thrown. If it is determined, after\nretrieving the exception, the exception cannot be handled after all\nit can be re-thrown it with napi_throw
where error is the\nJavaScript value to be thrown.
The following utility functions are also available in case native code\nneeds to throw an exception or determine if a napi_value
is an instance\nof a JavaScript Error
object: napi_throw_error
,\nnapi_throw_type_error
, napi_throw_range_error
, node_api_throw_syntax_error
and napi_is_error
.
The following utility functions are also available in case native\ncode needs to create an Error
object: napi_create_error
,\nnapi_create_type_error
, napi_create_range_error
and node_api_create_syntax_error
,\nwhere result is the napi_value
that refers to the newly created\nJavaScript Error
object.
The Node.js project is adding error codes to all of the errors\ngenerated internally. The goal is for applications to use these\nerror codes for all error checking. The associated error messages\nwill remain, but will only be meant to be used for logging and\ndisplay with the expectation that the message can change without\nSemVer applying. In order to support this model with Node-API, both\nin internal functionality and for module specific functionality\n(as its good practice), the throw_
and create_
functions\ntake an optional code parameter which is the string for the code\nto be added to the error object. If the optional parameter is NULL
\nthen no code will be associated with the error. If a code is provided,\nthe name associated with the error is also updated to be:
originalName [code]\n
\nwhere originalName
is the original name associated with the error\nand code
is the code that was provided. For example, if the code\nis 'ERR_ERROR_1'
and a TypeError
is being created the name will be:
TypeError [ERR_ERROR_1]\n
",
"modules": [
{
"textRaw": "`napi_throw`",
"name": "`napi_throw`",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "NAPI_EXTERN napi_status napi_throw(napi_env env, napi_value error);\n
\n[in] env
: The environment that the API is invoked under.[in] error
: The JavaScript value to be thrown.Returns napi_ok
if the API succeeded.
This API throws the JavaScript value provided.
", "type": "module", "displayName": "`napi_throw`" }, { "textRaw": "`napi_throw_error`", "name": "`napi_throw_error`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_throw_error(napi_env env,\n const char* code,\n const char* msg);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional error code to be set on the error.[in] msg
: C string representing the text to be associated with the error.Returns napi_ok
if the API succeeded.
This API throws a JavaScript Error
with the text provided.
NAPI_EXTERN napi_status napi_throw_type_error(napi_env env,\n const char* code,\n const char* msg);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional error code to be set on the error.[in] msg
: C string representing the text to be associated with the error.Returns napi_ok
if the API succeeded.
This API throws a JavaScript TypeError
with the text provided.
NAPI_EXTERN napi_status napi_throw_range_error(napi_env env,\n const char* code,\n const char* msg);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional error code to be set on the error.[in] msg
: C string representing the text to be associated with the error.Returns napi_ok
if the API succeeded.
This API throws a JavaScript RangeError
with the text provided.
NAPI_EXTERN napi_status node_api_throw_syntax_error(napi_env env,\n const char* code,\n const char* msg);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional error code to be set on the error.[in] msg
: C string representing the text to be associated with the error.Returns napi_ok
if the API succeeded.
This API throws a JavaScript SyntaxError
with the text provided.
NAPI_EXTERN napi_status napi_is_error(napi_env env,\n napi_value value,\n bool* result);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The napi_value
to be checked.[out] result
: Boolean value that is set to true if napi_value
represents\nan error, false otherwise.Returns napi_ok
if the API succeeded.
This API queries a napi_value
to check if it represents an error object.
NAPI_EXTERN napi_status napi_create_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional napi_value
with the string for the error code to be\nassociated with the error.[in] msg
: napi_value
that references a JavaScript string
to be used as\nthe message for the Error
.[out] result
: napi_value
representing the error created.Returns napi_ok
if the API succeeded.
This API returns a JavaScript Error
with the text provided.
NAPI_EXTERN napi_status napi_create_type_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional napi_value
with the string for the error code to be\nassociated with the error.[in] msg
: napi_value
that references a JavaScript string
to be used as\nthe message for the Error
.[out] result
: napi_value
representing the error created.Returns napi_ok
if the API succeeded.
This API returns a JavaScript TypeError
with the text provided.
NAPI_EXTERN napi_status napi_create_range_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional napi_value
with the string for the error code to be\nassociated with the error.[in] msg
: napi_value
that references a JavaScript string
to be used as\nthe message for the Error
.[out] result
: napi_value
representing the error created.Returns napi_ok
if the API succeeded.
This API returns a JavaScript RangeError
with the text provided.
NAPI_EXTERN napi_status node_api_create_syntax_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] code
: Optional napi_value
with the string for the error code to be\nassociated with the error.[in] msg
: napi_value
that references a JavaScript string
to be used as\nthe message for the Error
.[out] result
: napi_value
representing the error created.Returns napi_ok
if the API succeeded.
This API returns a JavaScript SyntaxError
with the text provided.
napi_status napi_get_and_clear_last_exception(napi_env env,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: The exception if one is pending, NULL
otherwise.Returns napi_ok
if the API succeeded.
This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_get_and_clear_last_exception`" }, { "textRaw": "`napi_is_exception_pending`", "name": "`napi_is_exception_pending`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_is_exception_pending(napi_env env, bool* result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: Boolean value that is set to true if an exception is pending.Returns napi_ok
if the API succeeded.
This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_is_exception_pending`" }, { "textRaw": "`napi_fatal_exception`", "name": "`napi_fatal_exception`", "meta": { "added": [ "v9.10.0" ], "napiVersion": [ 3 ], "changes": [] }, "desc": "napi_status napi_fatal_exception(napi_env env, napi_value err);\n
\n[in] env
: The environment that the API is invoked under.[in] err
: The error that is passed to 'uncaughtException'
.Trigger an 'uncaughtException'
in JavaScript. Useful if an async\ncallback throws an exception with no way to recover.
In the event of an unrecoverable error in a native addon, a fatal error can be\nthrown to immediately terminate the process.
", "modules": [ { "textRaw": "`napi_fatal_error`", "name": "`napi_fatal_error`", "meta": { "added": [ "v8.2.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_NO_RETURN void napi_fatal_error(const char* location,\n size_t location_len,\n const char* message,\n size_t message_len);\n
\n[in] location
: Optional location at which the error occurred.[in] location_len
: The length of the location in bytes, or\nNAPI_AUTO_LENGTH
if it is null-terminated.[in] message
: The message associated with the error.[in] message_len
: The length of the message in bytes, or NAPI_AUTO_LENGTH
\nif it is null-terminated.The function call does not return, the process will be terminated.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_fatal_error`" } ], "type": "module", "displayName": "Fatal errors" } ], "type": "misc", "displayName": "Error handling" }, { "textRaw": "Object lifetime management", "name": "object_lifetime_management", "desc": "As Node-API calls are made, handles to objects in the heap for the underlying\nVM may be returned as napi_values
. These handles must hold the\nobjects 'live' until they are no longer required by the native code,\notherwise the objects could be collected before the native code was\nfinished using them.
As object handles are returned they are associated with a\n'scope'. The lifespan for the default scope is tied to the lifespan\nof the native method call. The result is that, by default, handles\nremain valid and the objects associated with these handles will be\nheld live for the lifespan of the native method call.
\nIn many cases, however, it is necessary that the handles remain valid for\neither a shorter or longer lifespan than that of the native method.\nThe sections which follow describe the Node-API functions that can be used\nto change the handle lifespan from the default.
", "modules": [ { "textRaw": "Making handle lifespan shorter than that of the native method", "name": "making_handle_lifespan_shorter_than_that_of_the_native_method", "desc": "It is often necessary to make the lifespan of handles shorter than\nthe lifespan of a native method. For example, consider a native method\nthat has a loop which iterates through the elements in a large array:
\nfor (int i = 0; i < 1000000; i++) {\n napi_value result;\n napi_status status = napi_get_element(env, object, i, &result);\n if (status != napi_ok) {\n break;\n }\n // do something with element\n}\n
\nThis would result in a large number of handles being created, consuming\nsubstantial resources. In addition, even though the native code could only\nuse the most recent handle, all of the associated objects would also be\nkept alive since they all share the same scope.
\nTo handle this case, Node-API provides the ability to establish a new 'scope' to\nwhich newly created handles will be associated. Once those handles\nare no longer required, the scope can be 'closed' and any handles associated\nwith the scope are invalidated. The methods available to open/close scopes are\nnapi_open_handle_scope
and napi_close_handle_scope
.
Node-API only supports a single nested hierarchy of scopes. There is only one\nactive scope at any time, and all new handles will be associated with that\nscope while it is active. Scopes must be closed in the reverse order from\nwhich they are opened. In addition, all scopes created within a native method\nmust be closed before returning from that method.
\nTaking the earlier example, adding calls to napi_open_handle_scope
and\nnapi_close_handle_scope
would ensure that at most a single handle\nis valid throughout the execution of the loop:
for (int i = 0; i < 1000000; i++) {\n napi_handle_scope scope;\n napi_status status = napi_open_handle_scope(env, &scope);\n if (status != napi_ok) {\n break;\n }\n napi_value result;\n status = napi_get_element(env, object, i, &result);\n if (status != napi_ok) {\n break;\n }\n // do something with element\n status = napi_close_handle_scope(env, scope);\n if (status != napi_ok) {\n break;\n }\n}\n
\nWhen nesting scopes, there are cases where a handle from an\ninner scope needs to live beyond the lifespan of that scope. Node-API supports\nan 'escapable scope' in order to support this case. An escapable scope\nallows one handle to be 'promoted' so that it 'escapes' the\ncurrent scope and the lifespan of the handle changes from the current\nscope to that of the outer scope.
\nThe methods available to open/close escapable scopes are\nnapi_open_escapable_handle_scope
and\nnapi_close_escapable_handle_scope
.
The request to promote a handle is made through napi_escape_handle
which\ncan only be called once.
NAPI_EXTERN napi_status napi_open_handle_scope(napi_env env,\n napi_handle_scope* result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: napi_value
representing the new scope.Returns napi_ok
if the API succeeded.
This API opens a new scope.
", "type": "module", "displayName": "`napi_open_handle_scope`" }, { "textRaw": "`napi_close_handle_scope`", "name": "`napi_close_handle_scope`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_close_handle_scope(napi_env env,\n napi_handle_scope scope);\n
\n[in] env
: The environment that the API is invoked under.[in] scope
: napi_value
representing the scope to be closed.Returns napi_ok
if the API succeeded.
This API closes the scope passed in. Scopes must be closed in the\nreverse order from which they were created.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_close_handle_scope`" }, { "textRaw": "`napi_open_escapable_handle_scope`", "name": "`napi_open_escapable_handle_scope`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\n napi_open_escapable_handle_scope(napi_env env,\n napi_handle_scope* result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: napi_value
representing the new scope.Returns napi_ok
if the API succeeded.
This API opens a new scope from which one object can be promoted\nto the outer scope.
", "type": "module", "displayName": "`napi_open_escapable_handle_scope`" }, { "textRaw": "`napi_close_escapable_handle_scope`", "name": "`napi_close_escapable_handle_scope`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\n napi_close_escapable_handle_scope(napi_env env,\n napi_handle_scope scope);\n
\n[in] env
: The environment that the API is invoked under.[in] scope
: napi_value
representing the scope to be closed.Returns napi_ok
if the API succeeded.
This API closes the scope passed in. Scopes must be closed in the\nreverse order from which they were created.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_close_escapable_handle_scope`" }, { "textRaw": "`napi_escape_handle`", "name": "`napi_escape_handle`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_escape_handle(napi_env env,\n napi_escapable_handle_scope scope,\n napi_value escapee,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] scope
: napi_value
representing the current scope.[in] escapee
: napi_value
representing the JavaScript Object
to be\nescaped.[out] result
: napi_value
representing the handle to the escaped Object
\nin the outer scope.Returns napi_ok
if the API succeeded.
This API promotes the handle to the JavaScript object so that it is valid\nfor the lifetime of the outer scope. It can only be called once per scope.\nIf it is called more than once an error will be returned.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_escape_handle`" } ], "type": "module", "displayName": "Making handle lifespan shorter than that of the native method" }, { "textRaw": "References to values with a lifespan longer than that of the native method", "name": "references_to_values_with_a_lifespan_longer_than_that_of_the_native_method", "desc": "In some cases, an addon will need to be able to create and reference values\nwith a lifespan longer than that of a single native method invocation. For\nexample, to create a constructor and later use that constructor\nin a request to create instances, it must be possible to reference\nthe constructor object across many different instance creation requests. This\nwould not be possible with a normal handle returned as a napi_value
as\ndescribed in the earlier section. The lifespan of a normal handle is\nmanaged by scopes and all scopes must be closed before the end of a native\nmethod.
Node-API provides methods for creating persistent references to values.\nCurrently Node-API only allows references to be created for a\nlimited set of value types, including object, external, function, and symbol.
\nEach reference has an associated count with a value of 0 or higher,\nwhich determines whether the reference will keep the corresponding value alive.\nReferences with a count of 0 do not prevent values from being collected.\nValues of object (object, function, external) and symbol types are becoming\n'weak' references and can still be accessed while they are not collected.\nAny count greater than 0 will prevent the values from being collected.
\nSymbol values have different flavors. The true weak reference behavior is\nonly supported by local symbols created with the napi_create_symbol
function\nor the JavaScript Symbol()
constructor calls. Globally registered symbols\ncreated with the node_api_symbol_for
function or JavaScript Symbol.for()
\nfunction calls remain always strong references because the garbage collector\ndoes not collect them. The same is true for well-known symbols such as\nSymbol.iterator
. They are also never collected by the garbage collector.
References can be created with an initial reference count. The count can\nthen be modified through napi_reference_ref
and\nnapi_reference_unref
. If an object is collected while the count\nfor a reference is 0, all subsequent calls to\nget the object associated with the reference napi_get_reference_value
\nwill return NULL
for the returned napi_value
. An attempt to call\nnapi_reference_ref
for a reference whose object has been collected\nresults in an error.
References must be deleted once they are no longer required by the addon. When\na reference is deleted, it will no longer prevent the corresponding object from\nbeing collected. Failure to delete a persistent reference results in\na 'memory leak' with both the native memory for the persistent reference and\nthe corresponding object on the heap being retained forever.
\nThere can be multiple persistent references created which refer to the same\nobject, each of which will either keep the object live or not based on its\nindividual count. Multiple persistent references to the same object\ncan result in unexpectedly keeping alive native memory. The native structures\nfor a persistent reference must be kept alive until finalizers for the\nreferenced object are executed. If a new persistent reference is created\nfor the same object, the finalizers for that object will not be\nrun and the native memory pointed by the earlier persistent reference\nwill not be freed. This can be avoided by calling\nnapi_delete_reference
in addition to napi_reference_unref
when possible.
Change History:
\nExperimental (NAPI_EXPERIMENTAL
is defined):
References can be created for all value types. The new supported value\ntypes do not support weak reference semantic and the values of these types\nare released when the reference count becomes 0 and cannot be accessed from\nthe reference anymore.
\nNAPI_EXTERN napi_status napi_create_reference(napi_env env,\n napi_value value,\n uint32_t initial_refcount,\n napi_ref* result);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The napi_value
for which a reference is being created.[in] initial_refcount
: Initial reference count for the new reference.[out] result
: napi_ref
pointing to the new reference.Returns napi_ok
if the API succeeded.
This API creates a new reference with the specified reference count\nto the value passed in.
", "type": "module", "displayName": "`napi_create_reference`" }, { "textRaw": "`napi_delete_reference`", "name": "`napi_delete_reference`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_delete_reference(napi_env env, napi_ref ref);\n
\n[in] env
: The environment that the API is invoked under.[in] ref
: napi_ref
to be deleted.Returns napi_ok
if the API succeeded.
This API deletes the reference passed in.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_delete_reference`" }, { "textRaw": "`napi_reference_ref`", "name": "`napi_reference_ref`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_reference_ref(napi_env env,\n napi_ref ref,\n uint32_t* result);\n
\n[in] env
: The environment that the API is invoked under.[in] ref
: napi_ref
for which the reference count will be incremented.[out] result
: The new reference count.Returns napi_ok
if the API succeeded.
This API increments the reference count for the reference\npassed in and returns the resulting reference count.
", "type": "module", "displayName": "`napi_reference_ref`" }, { "textRaw": "`napi_reference_unref`", "name": "`napi_reference_unref`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_reference_unref(napi_env env,\n napi_ref ref,\n uint32_t* result);\n
\n[in] env
: The environment that the API is invoked under.[in] ref
: napi_ref
for which the reference count will be decremented.[out] result
: The new reference count.Returns napi_ok
if the API succeeded.
This API decrements the reference count for the reference\npassed in and returns the resulting reference count.
", "type": "module", "displayName": "`napi_reference_unref`" }, { "textRaw": "`napi_get_reference_value`", "name": "`napi_get_reference_value`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_get_reference_value(napi_env env,\n napi_ref ref,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] ref
: The napi_ref
for which the corresponding value is\nbeing requested.[out] result
: The napi_value
referenced by the napi_ref
.Returns napi_ok
if the API succeeded.
If still valid, this API returns the napi_value
representing the\nJavaScript value associated with the napi_ref
. Otherwise, result\nwill be NULL
.
While a Node.js process typically releases all its resources when exiting,\nembedders of Node.js, or future Worker support, may require addons to register\nclean-up hooks that will be run once the current Node.js environment exits.
\nNode-API provides functions for registering and un-registering such callbacks.\nWhen those callbacks are run, all resources that are being held by the addon\nshould be freed up.
", "modules": [ { "textRaw": "`napi_add_env_cleanup_hook`", "name": "`napi_add_env_cleanup_hook`", "meta": { "added": [ "v10.2.0" ], "napiVersion": [ 3 ], "changes": [] }, "desc": "NODE_EXTERN napi_status napi_add_env_cleanup_hook(node_api_nogc_env env,\n napi_cleanup_hook fun,\n void* arg);\n
\nRegisters fun
as a function to be run with the arg
parameter once the\ncurrent Node.js environment exits.
A function can safely be specified multiple times with different\narg
values. In that case, it will be called multiple times as well.\nProviding the same fun
and arg
values multiple times is not allowed\nand will lead the process to abort.
The hooks will be called in reverse order, i.e. the most recently added one\nwill be called first.
\nRemoving this hook can be done by using napi_remove_env_cleanup_hook
.\nTypically, that happens when the resource for which this hook was added\nis being torn down anyway.
For asynchronous cleanup, napi_add_async_cleanup_hook
is available.
NAPI_EXTERN napi_status napi_remove_env_cleanup_hook(node_api_nogc_env env,\n void (*fun)(void* arg),\n void* arg);\n
\nUnregisters fun
as a function to be run with the arg
parameter once the\ncurrent Node.js environment exits. Both the argument and the function value\nneed to be exact matches.
The function must have originally been registered\nwith napi_add_env_cleanup_hook
, otherwise the process will abort.
NAPI_EXTERN napi_status napi_add_async_cleanup_hook(\n node_api_nogc_env env,\n napi_async_cleanup_hook hook,\n void* arg,\n napi_async_cleanup_hook_handle* remove_handle);\n
\n[in] env
: The environment that the API is invoked under.[in] hook
: The function pointer to call at environment teardown.[in] arg
: The pointer to pass to hook
when it gets called.[out] remove_handle
: Optional handle that refers to the asynchronous cleanup\nhook.Registers hook
, which is a function of type napi_async_cleanup_hook
, as\na function to be run with the remove_handle
and arg
parameters once the\ncurrent Node.js environment exits.
Unlike napi_add_env_cleanup_hook
, the hook is allowed to be asynchronous.
Otherwise, behavior generally matches that of napi_add_env_cleanup_hook
.
If remove_handle
is not NULL
, an opaque value will be stored in it\nthat must later be passed to napi_remove_async_cleanup_hook
,\nregardless of whether the hook has already been invoked.\nTypically, that happens when the resource for which this hook was added\nis being torn down anyway.
NAPI_EXTERN napi_status napi_remove_async_cleanup_hook(\n napi_async_cleanup_hook_handle remove_handle);\n
\n[in] remove_handle
: The handle to an asynchronous cleanup hook that was\ncreated with napi_add_async_cleanup_hook
.Unregisters the cleanup hook corresponding to remove_handle
. This will prevent\nthe hook from being executed, unless it has already started executing.\nThis must be called on any napi_async_cleanup_hook_handle
value obtained\nfrom napi_add_async_cleanup_hook
.
The Node.js environment may be torn down at an arbitrary time as soon as\npossible with JavaScript execution disallowed, like on the request of\nworker.terminate()
. When the environment is being torn down, the\nregistered napi_finalize
callbacks of JavaScript objects, thread-safe\nfunctions and environment instance data are invoked immediately and\nindependently.
The invocation of napi_finalize
callbacks is scheduled after the manually\nregistered cleanup hooks. In order to ensure a proper order of addon\nfinalization during environment shutdown to avoid use-after-free in the\nnapi_finalize
callback, addons should register a cleanup hook with\nnapi_add_env_cleanup_hook
and napi_add_async_cleanup_hook
to manually\nrelease the allocated resource in a proper order.
Node-API modules are registered in a manner similar to other modules\nexcept that instead of using the NODE_MODULE
macro the following\nis used:
NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)\n
\nThe next difference is the signature for the Init
method. For a Node-API\nmodule it is as follows:
napi_value Init(napi_env env, napi_value exports);\n
\nThe return value from Init
is treated as the exports
object for the module.\nThe Init
method is passed an empty object via the exports
parameter as a\nconvenience. If Init
returns NULL
, the parameter passed as exports
is\nexported by the module. Node-API modules cannot modify the module
object but\ncan specify anything as the exports
property of the module.
To add the method hello
as a function so that it can be called as a method\nprovided by the addon:
napi_value Init(napi_env env, napi_value exports) {\n napi_status status;\n napi_property_descriptor desc = {\n \"hello\",\n NULL,\n Method,\n NULL,\n NULL,\n NULL,\n napi_writable | napi_enumerable | napi_configurable,\n NULL\n };\n status = napi_define_properties(env, exports, 1, &desc);\n if (status != napi_ok) return NULL;\n return exports;\n}\n
\nTo set a function to be returned by the require()
for the addon:
napi_value Init(napi_env env, napi_value exports) {\n napi_value method;\n napi_status status;\n status = napi_create_function(env, \"exports\", NAPI_AUTO_LENGTH, Method, NULL, &method);\n if (status != napi_ok) return NULL;\n return method;\n}\n
\nTo define a class so that new instances can be created (often used with\nObject wrap):
\n// NOTE: partial example, not all referenced code is included\nnapi_value Init(napi_env env, napi_value exports) {\n napi_status status;\n napi_property_descriptor properties[] = {\n { \"value\", NULL, NULL, GetValue, SetValue, NULL, napi_writable | napi_configurable, NULL },\n DECLARE_NAPI_METHOD(\"plusOne\", PlusOne),\n DECLARE_NAPI_METHOD(\"multiply\", Multiply),\n };\n\n napi_value cons;\n status =\n napi_define_class(env, \"MyObject\", New, NULL, 3, properties, &cons);\n if (status != napi_ok) return NULL;\n\n status = napi_create_reference(env, cons, 1, &constructor);\n if (status != napi_ok) return NULL;\n\n status = napi_set_named_property(env, exports, \"MyObject\", cons);\n if (status != napi_ok) return NULL;\n\n return exports;\n}\n
\nYou can also use the NAPI_MODULE_INIT
macro, which acts as a shorthand\nfor NAPI_MODULE
and defining an Init
function:
NAPI_MODULE_INIT(/* napi_env env, napi_value exports */) {\n napi_value answer;\n napi_status result;\n\n status = napi_create_int64(env, 42, &answer);\n if (status != napi_ok) return NULL;\n\n status = napi_set_named_property(env, exports, \"answer\", answer);\n if (status != napi_ok) return NULL;\n\n return exports;\n}\n
\nThe parameters env
and exports
are provided to the body of the\nNAPI_MODULE_INIT
macro.
All Node-API addons are context-aware, meaning they may be loaded multiple\ntimes. There are a few design considerations when declaring such a module.\nThe documentation on context-aware addons provides more details.
\nThe variables env
and exports
will be available inside the function body\nfollowing the macro invocation.
For more details on setting properties on objects, see the section on\nWorking with JavaScript properties.
\nFor more details on building addon modules in general, refer to the existing\nAPI.
", "type": "misc", "displayName": "Module registration" }, { "textRaw": "Working with JavaScript values", "name": "working_with_javascript_values", "desc": "Node-API exposes a set of APIs to create all types of JavaScript values.\nSome of these types are documented under Section 6\nof the ECMAScript Language Specification.
\nFundamentally, these APIs are used to do one of the following:
\nundefined
and null
Node-API values are represented by the type napi_value
.\nAny Node-API call that requires a JavaScript value takes in a napi_value
.\nIn some cases, the API does check the type of the napi_value
up-front.\nHowever, for better performance, it's better for the caller to make sure that\nthe napi_value
in question is of the JavaScript type expected by the API.
typedef enum {\n napi_key_include_prototypes,\n napi_key_own_only\n} napi_key_collection_mode;\n
\nDescribes the Keys/Properties
filter enums:
napi_key_collection_mode
limits the range of collected properties.
napi_key_own_only
limits the collected properties to the given\nobject only. napi_key_include_prototypes
will include all keys\nof the objects's prototype chain as well.
typedef enum {\n napi_key_all_properties = 0,\n napi_key_writable = 1,\n napi_key_enumerable = 1 << 1,\n napi_key_configurable = 1 << 2,\n napi_key_skip_strings = 1 << 3,\n napi_key_skip_symbols = 1 << 4\n} napi_key_filter;\n
\nProperty filter bits. They can be or'ed to build a composite filter.
", "type": "module", "displayName": "`napi_key_filter`" }, { "textRaw": "`napi_key_conversion`", "name": "`napi_key_conversion`", "meta": { "added": [ "v13.7.0", "v12.17.0", "v10.20.0" ], "napiVersion": [ 6 ], "changes": [] }, "desc": "typedef enum {\n napi_key_keep_numbers,\n napi_key_numbers_to_strings\n} napi_key_conversion;\n
\nnapi_key_numbers_to_strings
will convert integer indices to\nstrings. napi_key_keep_numbers
will return numbers for integer\nindices.
typedef enum {\n // ES6 types (corresponds to typeof)\n napi_undefined,\n napi_null,\n napi_boolean,\n napi_number,\n napi_string,\n napi_symbol,\n napi_object,\n napi_function,\n napi_external,\n napi_bigint,\n} napi_valuetype;\n
\nDescribes the type of a napi_value
. This generally corresponds to the types\ndescribed in Section 6.1 of the ECMAScript Language Specification.\nIn addition to types in that section, napi_valuetype
can also represent\nFunction
s and Object
s with external data.
A JavaScript value of type napi_external
appears in JavaScript as a plain\nobject such that no properties can be set on it, and no prototype.
typedef enum {\n napi_int8_array,\n napi_uint8_array,\n napi_uint8_clamped_array,\n napi_int16_array,\n napi_uint16_array,\n napi_int32_array,\n napi_uint32_array,\n napi_float32_array,\n napi_float64_array,\n napi_bigint64_array,\n napi_biguint64_array,\n} napi_typedarray_type;\n
\nThis represents the underlying binary scalar datatype of the TypedArray
.\nElements of this enum correspond to\nSection 22.2 of the ECMAScript Language Specification.
napi_status napi_create_array(napi_env env, napi_value* result)\n
\n[in] env
: The environment that the Node-API call is invoked under.[out] result
: A napi_value
representing a JavaScript Array
.Returns napi_ok
if the API succeeded.
This API returns a Node-API value corresponding to a JavaScript Array
type.\nJavaScript arrays are described in\nSection 22.1 of the ECMAScript Language Specification.
napi_status napi_create_array_with_length(napi_env env,\n size_t length,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] length
: The initial length of the Array
.[out] result
: A napi_value
representing a JavaScript Array
.Returns napi_ok
if the API succeeded.
This API returns a Node-API value corresponding to a JavaScript Array
type.\nThe Array
's length property is set to the passed-in length parameter.\nHowever, the underlying buffer is not guaranteed to be pre-allocated by the VM\nwhen the array is created. That behavior is left to the underlying VM\nimplementation. If the buffer must be a contiguous block of memory that can be\ndirectly read and/or written via C, consider using\nnapi_create_external_arraybuffer
.
JavaScript arrays are described in\nSection 22.1 of the ECMAScript Language Specification.
", "type": "module", "displayName": "`napi_create_array_with_length`" }, { "textRaw": "`napi_create_arraybuffer`", "name": "`napi_create_arraybuffer`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_create_arraybuffer(napi_env env,\n size_t byte_length,\n void** data,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] length
: The length in bytes of the array buffer to create.[out] data
: Pointer to the underlying byte buffer of the ArrayBuffer
.\ndata
can optionally be ignored by passing NULL
.[out] result
: A napi_value
representing a JavaScript ArrayBuffer
.Returns napi_ok
if the API succeeded.
This API returns a Node-API value corresponding to a JavaScript ArrayBuffer
.\nArrayBuffer
s are used to represent fixed-length binary data buffers. They are\nnormally used as a backing-buffer for TypedArray
objects.\nThe ArrayBuffer
allocated will have an underlying byte buffer whose size is\ndetermined by the length
parameter that's passed in.\nThe underlying buffer is optionally returned back to the caller in case the\ncaller wants to directly manipulate the buffer. This buffer can only be\nwritten to directly from native code. To write to this buffer from JavaScript,\na typed array or DataView
object would need to be created.
JavaScript ArrayBuffer
objects are described in\nSection 24.1 of the ECMAScript Language Specification.
napi_status napi_create_buffer(napi_env env,\n size_t size,\n void** data,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] size
: Size in bytes of the underlying buffer.[out] data
: Raw pointer to the underlying buffer.\ndata
can optionally be ignored by passing NULL
.[out] result
: A napi_value
representing a node::Buffer
.Returns napi_ok
if the API succeeded.
This API allocates a node::Buffer
object. While this is still a\nfully-supported data structure, in most cases using a TypedArray
will suffice.
napi_status napi_create_buffer_copy(napi_env env,\n size_t length,\n const void* data,\n void** result_data,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] size
: Size in bytes of the input buffer (should be the same as the size\nof the new buffer).[in] data
: Raw pointer to the underlying buffer to copy from.[out] result_data
: Pointer to the new Buffer
's underlying data buffer.\nresult_data
can optionally be ignored by passing NULL
.[out] result
: A napi_value
representing a node::Buffer
.Returns napi_ok
if the API succeeded.
This API allocates a node::Buffer
object and initializes it with data copied\nfrom the passed-in buffer. While this is still a fully-supported data\nstructure, in most cases using a TypedArray
will suffice.
napi_status napi_create_date(napi_env env,\n double time,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] time
: ECMAScript time value in milliseconds since 01 January, 1970 UTC.[out] result
: A napi_value
representing a JavaScript Date
.Returns napi_ok
if the API succeeded.
This API does not observe leap seconds; they are ignored, as\nECMAScript aligns with POSIX time specification.
\nThis API allocates a JavaScript Date
object.
JavaScript Date
objects are described in\nSection 20.3 of the ECMAScript Language Specification.
napi_status napi_create_external(napi_env env,\n void* data,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] data
: Raw pointer to the external data.[in] finalize_cb
: Optional callback to call when the external value is being\ncollected. napi_finalize
provides more details.[in] finalize_hint
: Optional hint to pass to the finalize callback during\ncollection.[out] result
: A napi_value
representing an external value.Returns napi_ok
if the API succeeded.
This API allocates a JavaScript value with external data attached to it. This\nis used to pass external data through JavaScript code, so it can be retrieved\nlater by native code using napi_get_value_external
.
The API adds a napi_finalize
callback which will be called when the JavaScript\nobject just created has been garbage collected.
The created value is not an object, and therefore does not support additional\nproperties. It is considered a distinct value type: calling napi_typeof()
with\nan external value yields napi_external
.
napi_status\nnapi_create_external_arraybuffer(napi_env env,\n void* external_data,\n size_t byte_length,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] external_data
: Pointer to the underlying byte buffer of the\nArrayBuffer
.[in] byte_length
: The length in bytes of the underlying buffer.[in] finalize_cb
: Optional callback to call when the ArrayBuffer
is being\ncollected. napi_finalize
provides more details.[in] finalize_hint
: Optional hint to pass to the finalize callback during\ncollection.[out] result
: A napi_value
representing a JavaScript ArrayBuffer
.Returns napi_ok
if the API succeeded.
Some runtimes other than Node.js have dropped support for external buffers.\nOn runtimes other than Node.js this method may return\nnapi_no_external_buffers_allowed
to indicate that external\nbuffers are not supported. One such runtime is Electron as\ndescribed in this issue\nelectron/issues/35801.
In order to maintain broadest compatibility with all runtimes\nyou may define NODE_API_NO_EXTERNAL_BUFFERS_ALLOWED
in your addon before\nincludes for the node-api headers. Doing so will hide the 2 functions\nthat create external buffers. This will ensure a compilation error\noccurs if you accidentally use one of these methods.
This API returns a Node-API value corresponding to a JavaScript ArrayBuffer
.\nThe underlying byte buffer of the ArrayBuffer
is externally allocated and\nmanaged. The caller must ensure that the byte buffer remains valid until the\nfinalize callback is called.
The API adds a napi_finalize
callback which will be called when the JavaScript\nobject just created has been garbage collected.
JavaScript ArrayBuffer
s are described in\nSection 24.1 of the ECMAScript Language Specification.
napi_status napi_create_external_buffer(napi_env env,\n size_t length,\n void* data,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] length
: Size in bytes of the input buffer (should be the same as the\nsize of the new buffer).[in] data
: Raw pointer to the underlying buffer to expose to JavaScript.[in] finalize_cb
: Optional callback to call when the ArrayBuffer
is being\ncollected. napi_finalize
provides more details.[in] finalize_hint
: Optional hint to pass to the finalize callback during\ncollection.[out] result
: A napi_value
representing a node::Buffer
.Returns napi_ok
if the API succeeded.
Some runtimes other than Node.js have dropped support for external buffers.\nOn runtimes other than Node.js this method may return\nnapi_no_external_buffers_allowed
to indicate that external\nbuffers are not supported. One such runtime is Electron as\ndescribed in this issue\nelectron/issues/35801.
In order to maintain broadest compatibility with all runtimes\nyou may define NODE_API_NO_EXTERNAL_BUFFERS_ALLOWED
in your addon before\nincludes for the node-api headers. Doing so will hide the 2 functions\nthat create external buffers. This will ensure a compilation error\noccurs if you accidentally use one of these methods.
This API allocates a node::Buffer
object and initializes it with data\nbacked by the passed in buffer. While this is still a fully-supported data\nstructure, in most cases using a TypedArray
will suffice.
The API adds a napi_finalize
callback which will be called when the JavaScript\nobject just created has been garbage collected.
For Node.js >=4 Buffers
are Uint8Array
s.
napi_status napi_create_object(napi_env env, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[out] result
: A napi_value
representing a JavaScript Object
.Returns napi_ok
if the API succeeded.
This API allocates a default JavaScript Object
.\nIt is the equivalent of doing new Object()
in JavaScript.
The JavaScript Object
type is described in Section 6.1.7 of the\nECMAScript Language Specification.
napi_status napi_create_symbol(napi_env env,\n napi_value description,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] description
: Optional napi_value
which refers to a JavaScript\nstring
to be set as the description for the symbol.[out] result
: A napi_value
representing a JavaScript symbol
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript symbol
value from a UTF8-encoded C string.
The JavaScript symbol
type is described in Section 19.4\nof the ECMAScript Language Specification.
napi_status node_api_symbol_for(napi_env env,\n const char* utf8description,\n size_t length,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] utf8description
: UTF-8 C string representing the text to be used as the\ndescription for the symbol.[in] length
: The length of the description string in bytes, or\nNAPI_AUTO_LENGTH
if it is null-terminated.[out] result
: A napi_value
representing a JavaScript symbol
.Returns napi_ok
if the API succeeded.
This API searches in the global registry for an existing symbol with the given\ndescription. If the symbol already exists it will be returned, otherwise a new\nsymbol will be created in the registry.
\nThe JavaScript symbol
type is described in Section 19.4 of the ECMAScript\nLanguage Specification.
napi_status napi_create_typedarray(napi_env env,\n napi_typedarray_type type,\n size_t length,\n napi_value arraybuffer,\n size_t byte_offset,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] type
: Scalar datatype of the elements within the TypedArray
.[in] length
: Number of elements in the TypedArray
.[in] arraybuffer
: ArrayBuffer
underlying the typed array.[in] byte_offset
: The byte offset within the ArrayBuffer
from which to\nstart projecting the TypedArray
.[out] result
: A napi_value
representing a JavaScript TypedArray
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript TypedArray
object over an existing\nArrayBuffer
. TypedArray
objects provide an array-like view over an\nunderlying data buffer where each element has the same underlying binary scalar\ndatatype.
It's required that (length * size_of_element) + byte_offset
should\nbe <= the size in bytes of the array passed in. If not, a RangeError
exception\nis raised.
JavaScript TypedArray
objects are described in\nSection 22.2 of the ECMAScript Language Specification.
napi_status napi_create_dataview(napi_env env,\n size_t byte_length,\n napi_value arraybuffer,\n size_t byte_offset,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] length
: Number of elements in the DataView
.[in] arraybuffer
: ArrayBuffer
underlying the DataView
.[in] byte_offset
: The byte offset within the ArrayBuffer
from which to\nstart projecting the DataView
.[out] result
: A napi_value
representing a JavaScript DataView
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript DataView
object over an existing ArrayBuffer
.\nDataView
objects provide an array-like view over an underlying data buffer,\nbut one which allows items of different size and type in the ArrayBuffer
.
It is required that byte_length + byte_offset
is less than or equal to the\nsize in bytes of the array passed in. If not, a RangeError
exception is\nraised.
JavaScript DataView
objects are described in\nSection 24.3 of the ECMAScript Language Specification.
napi_status napi_create_int32(napi_env env, int32_t value, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: Integer value to be represented in JavaScript.[out] result
: A napi_value
representing a JavaScript number
.Returns napi_ok
if the API succeeded.
This API is used to convert from the C int32_t
type to the JavaScript\nnumber
type.
The JavaScript number
type is described in\nSection 6.1.6 of the ECMAScript Language Specification.
napi_status napi_create_uint32(napi_env env, uint32_t value, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: Unsigned integer value to be represented in JavaScript.[out] result
: A napi_value
representing a JavaScript number
.Returns napi_ok
if the API succeeded.
This API is used to convert from the C uint32_t
type to the JavaScript\nnumber
type.
The JavaScript number
type is described in\nSection 6.1.6 of the ECMAScript Language Specification.
napi_status napi_create_int64(napi_env env, int64_t value, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: Integer value to be represented in JavaScript.[out] result
: A napi_value
representing a JavaScript number
.Returns napi_ok
if the API succeeded.
This API is used to convert from the C int64_t
type to the JavaScript\nnumber
type.
The JavaScript number
type is described in Section 6.1.6\nof the ECMAScript Language Specification. Note the complete range of int64_t
\ncannot be represented with full precision in JavaScript. Integer values\noutside the range of Number.MIN_SAFE_INTEGER
-(2**53 - 1)
-\nNumber.MAX_SAFE_INTEGER
(2**53 - 1)
will lose precision.
napi_status napi_create_double(napi_env env, double value, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: Double-precision value to be represented in JavaScript.[out] result
: A napi_value
representing a JavaScript number
.Returns napi_ok
if the API succeeded.
This API is used to convert from the C double
type to the JavaScript\nnumber
type.
The JavaScript number
type is described in\nSection 6.1.6 of the ECMAScript Language Specification.
napi_status napi_create_bigint_int64(napi_env env,\n int64_t value,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: Integer value to be represented in JavaScript.[out] result
: A napi_value
representing a JavaScript BigInt
.Returns napi_ok
if the API succeeded.
This API converts the C int64_t
type to the JavaScript BigInt
type.
napi_status napi_create_bigint_uint64(napi_env env,\n uint64_t value,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: Unsigned integer value to be represented in JavaScript.[out] result
: A napi_value
representing a JavaScript BigInt
.Returns napi_ok
if the API succeeded.
This API converts the C uint64_t
type to the JavaScript BigInt
type.
napi_status napi_create_bigint_words(napi_env env,\n int sign_bit,\n size_t word_count,\n const uint64_t* words,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] sign_bit
: Determines if the resulting BigInt
will be positive or\nnegative.[in] word_count
: The length of the words
array.[in] words
: An array of uint64_t
little-endian 64-bit words.[out] result
: A napi_value
representing a JavaScript BigInt
.Returns napi_ok
if the API succeeded.
This API converts an array of unsigned 64-bit words into a single BigInt
\nvalue.
The resulting BigInt
is calculated as: (–1)sign_bit
(words[0]
\n× (264)0 + words[1]
× (264)1 + …)
napi_status napi_create_string_latin1(napi_env env,\n const char* str,\n size_t length,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] str
: Character buffer representing an ISO-8859-1-encoded string.[in] length
: The length of the string in bytes, or NAPI_AUTO_LENGTH
if it\nis null-terminated.[out] result
: A napi_value
representing a JavaScript string
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript string
value from an ISO-8859-1-encoded C\nstring. The native string is copied.
The JavaScript string
type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status\nnode_api_create_external_string_latin1(napi_env env,\n char* str,\n size_t length,\n napi_finalize finalize_callback,\n void* finalize_hint,\n napi_value* result,\n bool* copied);\n
\n[in] env
: The environment that the API is invoked under.[in] str
: Character buffer representing an ISO-8859-1-encoded string.[in] length
: The length of the string in bytes, or NAPI_AUTO_LENGTH
if it\nis null-terminated.[in] finalize_callback
: The function to call when the string is being\ncollected. The function will be called with the following parameters:\n[in] env
: The environment in which the add-on is running. This value\nmay be null if the string is being collected as part of the termination\nof the worker or the main Node.js instance.[in] data
: This is the value str
as a void*
pointer.[in] finalize_hint
: This is the value finalize_hint
that was given\nto the API.\nnapi_finalize
provides more details.\nThis parameter is optional. Passing a null value means that the add-on\ndoesn't need to be notified when the corresponding JavaScript string is\ncollected.[in] finalize_hint
: Optional hint to pass to the finalize callback during\ncollection.[out] result
: A napi_value
representing a JavaScript string
.[out] copied
: Whether the string was copied. If it was, the finalizer will\nalready have been invoked to destroy str
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript string
value from an ISO-8859-1-encoded C\nstring. The native string may not be copied and must thus exist for the entire\nlife cycle of the JavaScript value.
The JavaScript string
type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status napi_create_string_utf16(napi_env env,\n const char16_t* str,\n size_t length,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] str
: Character buffer representing a UTF16-LE-encoded string.[in] length
: The length of the string in two-byte code units, or\nNAPI_AUTO_LENGTH
if it is null-terminated.[out] result
: A napi_value
representing a JavaScript string
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript string
value from a UTF16-LE-encoded C string.\nThe native string is copied.
The JavaScript string
type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status\nnode_api_create_external_string_utf16(napi_env env,\n char16_t* str,\n size_t length,\n napi_finalize finalize_callback,\n void* finalize_hint,\n napi_value* result,\n bool* copied);\n
\n[in] env
: The environment that the API is invoked under.[in] str
: Character buffer representing a UTF16-LE-encoded string.[in] length
: The length of the string in two-byte code units, or\nNAPI_AUTO_LENGTH
if it is null-terminated.[in] finalize_callback
: The function to call when the string is being\ncollected. The function will be called with the following parameters:\n[in] env
: The environment in which the add-on is running. This value\nmay be null if the string is being collected as part of the termination\nof the worker or the main Node.js instance.[in] data
: This is the value str
as a void*
pointer.[in] finalize_hint
: This is the value finalize_hint
that was given\nto the API.\nnapi_finalize
provides more details.\nThis parameter is optional. Passing a null value means that the add-on\ndoesn't need to be notified when the corresponding JavaScript string is\ncollected.[in] finalize_hint
: Optional hint to pass to the finalize callback during\ncollection.[out] result
: A napi_value
representing a JavaScript string
.[out] copied
: Whether the string was copied. If it was, the finalizer will\nalready have been invoked to destroy str
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript string
value from a UTF16-LE-encoded C string.\nThe native string may not be copied and must thus exist for the entire life\ncycle of the JavaScript value.
The JavaScript string
type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status napi_create_string_utf8(napi_env env,\n const char* str,\n size_t length,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] str
: Character buffer representing a UTF8-encoded string.[in] length
: The length of the string in bytes, or NAPI_AUTO_LENGTH
if it\nis null-terminated.[out] result
: A napi_value
representing a JavaScript string
.Returns napi_ok
if the API succeeded.
This API creates a JavaScript string
value from a UTF8-encoded C string.\nThe native string is copied.
The JavaScript string
type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status NAPI_CDECL node_api_create_property_key_utf16(napi_env env,\n const char16_t* str,\n size_t length,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] str
: Character buffer representing a UTF16-LE-encoded string.[in] length
: The length of the string in two-byte code units, or\nNAPI_AUTO_LENGTH
if it is null-terminated.[out] result
: A napi_value
representing an optimized JavaScript string
\nto be used as a property key for objects.Returns napi_ok
if the API succeeded.
This API creates an optimized JavaScript string
value from\na UTF16-LE-encoded C string to be used as a property key for objects.\nThe native string is copied.
Many JavaScript engines including V8 use internalized strings as keys\nto set and get property values. They typically use a hash table to create\nand lookup such strings. While it adds some cost per key creation, it improves\nthe performance after that by enabling comparison of string pointers instead\nof the whole strings.
\nIf a new JavaScript string is intended to be used as a property key, then for\nsome JavaScript engines it will be more efficient to use\nthe node_api_create_property_key_utf16
function.\nOtherwise, use the napi_create_string_utf16
or\nnode_api_create_external_string_utf16
functions as there may be additional\noverhead in creating/storing strings with this method.
The JavaScript string
type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status napi_get_array_length(napi_env env,\n napi_value value,\n uint32_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing the JavaScript Array
whose length is\nbeing queried.[out] result
: uint32
representing length of the array.Returns napi_ok
if the API succeeded.
This API returns the length of an array.
\nArray
length is described in Section 22.1.4.1 of the ECMAScript Language\nSpecification.
napi_status napi_get_arraybuffer_info(napi_env env,\n napi_value arraybuffer,\n void** data,\n size_t* byte_length)\n
\n[in] env
: The environment that the API is invoked under.[in] arraybuffer
: napi_value
representing the ArrayBuffer
being queried.[out] data
: The underlying data buffer of the ArrayBuffer
. If byte_length\nis 0
, this may be NULL
or any other pointer value.[out] byte_length
: Length in bytes of the underlying data buffer.Returns napi_ok
if the API succeeded.
This API is used to retrieve the underlying data buffer of an ArrayBuffer
and\nits length.
WARNING: Use caution while using this API. The lifetime of the underlying data\nbuffer is managed by the ArrayBuffer
even after it's returned. A\npossible safe way to use this API is in conjunction with\nnapi_create_reference
, which can be used to guarantee control over the\nlifetime of the ArrayBuffer
. It's also safe to use the returned data buffer\nwithin the same callback as long as there are no calls to other APIs that might\ntrigger a GC.
napi_status napi_get_buffer_info(napi_env env,\n napi_value value,\n void** data,\n size_t* length)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing the node::Buffer
or Uint8Array
\nbeing queried.[out] data
: The underlying data buffer of the node::Buffer
or\nUint8Array
. If length is 0
, this may be NULL
or any other pointer value.[out] length
: Length in bytes of the underlying data buffer.Returns napi_ok
if the API succeeded.
This method returns the identical data
and byte_length
as\nnapi_get_typedarray_info
. And napi_get_typedarray_info
accepts a\nnode::Buffer
(a Uint8Array) as the value too.
This API is used to retrieve the underlying data buffer of a node::Buffer
\nand its length.
Warning: Use caution while using this API since the underlying data buffer's\nlifetime is not guaranteed if it's managed by the VM.
", "type": "module", "displayName": "`napi_get_buffer_info`" }, { "textRaw": "`napi_get_prototype`", "name": "`napi_get_prototype`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_prototype(napi_env env,\n napi_value object,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] object
: napi_value
representing JavaScript Object
whose prototype\nto return. This returns the equivalent of Object.getPrototypeOf
(which is\nnot the same as the function's prototype
property).[out] result
: napi_value
representing prototype of the given object.Returns napi_ok
if the API succeeded.
napi_status napi_get_typedarray_info(napi_env env,\n napi_value typedarray,\n napi_typedarray_type* type,\n size_t* length,\n void** data,\n napi_value* arraybuffer,\n size_t* byte_offset)\n
\n[in] env
: The environment that the API is invoked under.[in] typedarray
: napi_value
representing the TypedArray
whose\nproperties to query.[out] type
: Scalar datatype of the elements within the TypedArray
.[out] length
: The number of elements in the TypedArray
.[out] data
: The data buffer underlying the TypedArray
adjusted by\nthe byte_offset
value so that it points to the first element in the\nTypedArray
. If the length of the array is 0
, this may be NULL
or\nany other pointer value.[out] arraybuffer
: The ArrayBuffer
underlying the TypedArray
.[out] byte_offset
: The byte offset within the underlying native array\nat which the first element of the arrays is located. The value for the data\nparameter has already been adjusted so that data points to the first element\nin the array. Therefore, the first byte of the native array would be at\ndata - byte_offset
.Returns napi_ok
if the API succeeded.
This API returns various properties of a typed array.
\nAny of the out parameters may be NULL
if that property is unneeded.
Warning: Use caution while using this API since the underlying data buffer\nis managed by the VM.
", "type": "module", "displayName": "`napi_get_typedarray_info`" }, { "textRaw": "`napi_get_dataview_info`", "name": "`napi_get_dataview_info`", "meta": { "added": [ "v8.3.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_dataview_info(napi_env env,\n napi_value dataview,\n size_t* byte_length,\n void** data,\n napi_value* arraybuffer,\n size_t* byte_offset)\n
\n[in] env
: The environment that the API is invoked under.[in] dataview
: napi_value
representing the DataView
whose\nproperties to query.[out] byte_length
: Number of bytes in the DataView
.[out] data
: The data buffer underlying the DataView
.\nIf byte_length is 0
, this may be NULL
or any other pointer value.[out] arraybuffer
: ArrayBuffer
underlying the DataView
.[out] byte_offset
: The byte offset within the data buffer from which\nto start projecting the DataView
.Returns napi_ok
if the API succeeded.
Any of the out parameters may be NULL
if that property is unneeded.
This API returns various properties of a DataView
.
napi_status napi_get_date_value(napi_env env,\n napi_value value,\n double* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing a JavaScript Date
.[out] result
: Time value as a double
represented as milliseconds since\nmidnight at the beginning of 01 January, 1970 UTC.This API does not observe leap seconds; they are ignored, as\nECMAScript aligns with POSIX time specification.
\nReturns napi_ok
if the API succeeded. If a non-date napi_value
is passed\nin it returns napi_date_expected
.
This API returns the C double primitive of time value for the given JavaScript\nDate
.
napi_status napi_get_value_bool(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript Boolean
.[out] result
: C boolean primitive equivalent of the given JavaScript\nBoolean
.Returns napi_ok
if the API succeeded. If a non-boolean napi_value
is\npassed in it returns napi_boolean_expected
.
This API returns the C boolean primitive equivalent of the given JavaScript\nBoolean
.
napi_status napi_get_value_double(napi_env env,\n napi_value value,\n double* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript number
.[out] result
: C double primitive equivalent of the given JavaScript\nnumber
.Returns napi_ok
if the API succeeded. If a non-number napi_value
is passed\nin it returns napi_number_expected
.
This API returns the C double primitive equivalent of the given JavaScript\nnumber
.
napi_status napi_get_value_bigint_int64(napi_env env,\n napi_value value,\n int64_t* result,\n bool* lossless);\n
\n[in] env
: The environment that the API is invoked under[in] value
: napi_value
representing JavaScript BigInt
.[out] result
: C int64_t
primitive equivalent of the given JavaScript\nBigInt
.[out] lossless
: Indicates whether the BigInt
value was converted\nlosslessly.Returns napi_ok
if the API succeeded. If a non-BigInt
is passed in it\nreturns napi_bigint_expected
.
This API returns the C int64_t
primitive equivalent of the given JavaScript\nBigInt
. If needed it will truncate the value, setting lossless
to false
.
napi_status napi_get_value_bigint_uint64(napi_env env,\n napi_value value,\n uint64_t* result,\n bool* lossless);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript BigInt
.[out] result
: C uint64_t
primitive equivalent of the given JavaScript\nBigInt
.[out] lossless
: Indicates whether the BigInt
value was converted\nlosslessly.Returns napi_ok
if the API succeeded. If a non-BigInt
is passed in it\nreturns napi_bigint_expected
.
This API returns the C uint64_t
primitive equivalent of the given JavaScript\nBigInt
. If needed it will truncate the value, setting lossless
to false
.
napi_status napi_get_value_bigint_words(napi_env env,\n napi_value value,\n int* sign_bit,\n size_t* word_count,\n uint64_t* words);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript BigInt
.[out] sign_bit
: Integer representing if the JavaScript BigInt
is positive\nor negative.[in/out] word_count
: Must be initialized to the length of the words
\narray. Upon return, it will be set to the actual number of words that\nwould be needed to store this BigInt
.[out] words
: Pointer to a pre-allocated 64-bit word array.Returns napi_ok
if the API succeeded.
This API converts a single BigInt
value into a sign bit, 64-bit little-endian\narray, and the number of elements in the array. sign_bit
and words
may be\nboth set to NULL
, in order to get only word_count
.
napi_status napi_get_value_external(napi_env env,\n napi_value value,\n void** result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript external value.[out] result
: Pointer to the data wrapped by the JavaScript external value.Returns napi_ok
if the API succeeded. If a non-external napi_value
is\npassed in it returns napi_invalid_arg
.
This API retrieves the external data pointer that was previously passed to\nnapi_create_external()
.
napi_status napi_get_value_int32(napi_env env,\n napi_value value,\n int32_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript number
.[out] result
: C int32
primitive equivalent of the given JavaScript\nnumber
.Returns napi_ok
if the API succeeded. If a non-number napi_value
\nis passed in napi_number_expected
.
This API returns the C int32
primitive equivalent\nof the given JavaScript number
.
If the number exceeds the range of the 32 bit integer, then the result is\ntruncated to the equivalent of the bottom 32 bits. This can result in a large\npositive number becoming a negative number if the value is > 231 - 1.
\nNon-finite number values (NaN
, +Infinity
, or -Infinity
) set the\nresult to zero.
napi_status napi_get_value_int64(napi_env env,\n napi_value value,\n int64_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript number
.[out] result
: C int64
primitive equivalent of the given JavaScript\nnumber
.Returns napi_ok
if the API succeeded. If a non-number napi_value
\nis passed in it returns napi_number_expected
.
This API returns the C int64
primitive equivalent of the given JavaScript\nnumber
.
number
values outside the range of Number.MIN_SAFE_INTEGER
\n-(2**53 - 1)
- Number.MAX_SAFE_INTEGER
(2**53 - 1)
will lose\nprecision.
Non-finite number values (NaN
, +Infinity
, or -Infinity
) set the\nresult to zero.
napi_status napi_get_value_string_latin1(napi_env env,\n napi_value value,\n char* buf,\n size_t bufsize,\n size_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript string.[in] buf
: Buffer to write the ISO-8859-1-encoded string into. If NULL
is\npassed in, the length of the string in bytes and excluding the null terminator\nis returned in result
.[in] bufsize
: Size of the destination buffer. When this value is\ninsufficient, the returned string is truncated and null-terminated.[out] result
: Number of bytes copied into the buffer, excluding the null\nterminator.Returns napi_ok
if the API succeeded. If a non-string
napi_value
\nis passed in it returns napi_string_expected
.
This API returns the ISO-8859-1-encoded string corresponding the value passed\nin.
", "type": "module", "displayName": "`napi_get_value_string_latin1`" }, { "textRaw": "`napi_get_value_string_utf8`", "name": "`napi_get_value_string_utf8`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_value_string_utf8(napi_env env,\n napi_value value,\n char* buf,\n size_t bufsize,\n size_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript string.[in] buf
: Buffer to write the UTF8-encoded string into. If NULL
is passed\nin, the length of the string in bytes and excluding the null terminator is\nreturned in result
.[in] bufsize
: Size of the destination buffer. When this value is\ninsufficient, the returned string is truncated and null-terminated.[out] result
: Number of bytes copied into the buffer, excluding the null\nterminator.Returns napi_ok
if the API succeeded. If a non-string
napi_value
\nis passed in it returns napi_string_expected
.
This API returns the UTF8-encoded string corresponding the value passed in.
", "type": "module", "displayName": "`napi_get_value_string_utf8`" }, { "textRaw": "`napi_get_value_string_utf16`", "name": "`napi_get_value_string_utf16`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_value_string_utf16(napi_env env,\n napi_value value,\n char16_t* buf,\n size_t bufsize,\n size_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript string.[in] buf
: Buffer to write the UTF16-LE-encoded string into. If NULL
is\npassed in, the length of the string in 2-byte code units and excluding the\nnull terminator is returned.[in] bufsize
: Size of the destination buffer. When this value is\ninsufficient, the returned string is truncated and null-terminated.[out] result
: Number of 2-byte code units copied into the buffer, excluding\nthe null terminator.Returns napi_ok
if the API succeeded. If a non-string
napi_value
\nis passed in it returns napi_string_expected
.
This API returns the UTF16-encoded string corresponding the value passed in.
", "type": "module", "displayName": "`napi_get_value_string_utf16`" }, { "textRaw": "`napi_get_value_uint32`", "name": "`napi_get_value_uint32`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_value_uint32(napi_env env,\n napi_value value,\n uint32_t* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing JavaScript number
.[out] result
: C primitive equivalent of the given napi_value
as a\nuint32_t
.Returns napi_ok
if the API succeeded. If a non-number napi_value
\nis passed in it returns napi_number_expected
.
This API returns the C primitive equivalent of the given napi_value
as a\nuint32_t
.
napi_status napi_get_boolean(napi_env env, bool value, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The value of the boolean to retrieve.[out] result
: napi_value
representing JavaScript Boolean
singleton to\nretrieve.Returns napi_ok
if the API succeeded.
This API is used to return the JavaScript singleton object that is used to\nrepresent the given boolean value.
", "type": "module", "displayName": "`napi_get_boolean`" }, { "textRaw": "`napi_get_global`", "name": "`napi_get_global`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_global(napi_env env, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[out] result
: napi_value
representing JavaScript global
object.Returns napi_ok
if the API succeeded.
This API returns the global
object.
napi_status napi_get_null(napi_env env, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[out] result
: napi_value
representing JavaScript null
object.Returns napi_ok
if the API succeeded.
This API returns the null
object.
napi_status napi_get_undefined(napi_env env, napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[out] result
: napi_value
representing JavaScript Undefined value.Returns napi_ok
if the API succeeded.
This API returns the Undefined object.
", "type": "module", "displayName": "`napi_get_undefined`" } ], "type": "module", "displayName": "Functions to get global instances" } ], "type": "misc", "displayName": "Working with JavaScript values" }, { "textRaw": "Working with JavaScript values and abstract operations", "name": "working_with_javascript_values_and_abstract_operations", "desc": "Node-API exposes a set of APIs to perform some abstract operations on JavaScript\nvalues. Some of these operations are documented under Section 7\nof the ECMAScript Language Specification.
\nThese APIs support doing one of the following:
\nnumber
or\nstring
).napi_status napi_coerce_to_bool(napi_env env,\n napi_value value,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to coerce.[out] result
: napi_value
representing the coerced JavaScript Boolean
.Returns napi_ok
if the API succeeded.
This API implements the abstract operation ToBoolean()
as defined in\nSection 7.1.2 of the ECMAScript Language Specification.
napi_status napi_coerce_to_number(napi_env env,\n napi_value value,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to coerce.[out] result
: napi_value
representing the coerced JavaScript number
.Returns napi_ok
if the API succeeded.
This API implements the abstract operation ToNumber()
as defined in\nSection 7.1.3 of the ECMAScript Language Specification.\nThis function potentially runs JS code if the passed-in value is an\nobject.
napi_status napi_coerce_to_object(napi_env env,\n napi_value value,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to coerce.[out] result
: napi_value
representing the coerced JavaScript Object
.Returns napi_ok
if the API succeeded.
This API implements the abstract operation ToObject()
as defined in\nSection 7.1.13 of the ECMAScript Language Specification.
napi_status napi_coerce_to_string(napi_env env,\n napi_value value,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to coerce.[out] result
: napi_value
representing the coerced JavaScript string
.Returns napi_ok
if the API succeeded.
This API implements the abstract operation ToString()
as defined in\nSection 7.1.13 of the ECMAScript Language Specification.\nThis function potentially runs JS code if the passed-in value is an\nobject.
napi_status napi_typeof(napi_env env, napi_value value, napi_valuetype* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value whose type to query.[out] result
: The type of the JavaScript value.Returns napi_ok
if the API succeeded.
napi_invalid_arg
if the type of value
is not a known ECMAScript type and\nvalue
is not an External value.This API represents behavior similar to invoking the typeof
Operator on\nthe object as defined in Section 12.5.5 of the ECMAScript Language\nSpecification. However, there are some differences:
null
as a separate type, while ECMAScript typeof
would detect\nobject
.If value
has a type that is invalid, an error is returned.
napi_status napi_instanceof(napi_env env,\n napi_value object,\n napi_value constructor,\n bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] object
: The JavaScript value to check.[in] constructor
: The JavaScript function object of the constructor function\nto check against.[out] result
: Boolean that is set to true if object instanceof constructor
\nis true.Returns napi_ok
if the API succeeded.
This API represents invoking the instanceof
Operator on the object as\ndefined in Section 12.10.4 of the ECMAScript Language Specification.
napi_status napi_is_array(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given object is an array.Returns napi_ok
if the API succeeded.
This API represents invoking the IsArray
operation on the object\nas defined in Section 7.2.2 of the ECMAScript Language Specification.
napi_status napi_is_arraybuffer(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given object is an ArrayBuffer
.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is an array buffer.
napi_status napi_is_buffer(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given napi_value
represents a node::Buffer
or\nUint8Array
object.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is a buffer or Uint8Array.\nnapi_is_typedarray
should be preferred if the caller needs to check if the\nvalue is a Uint8Array.
napi_status napi_is_date(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given napi_value
represents a JavaScript Date
\nobject.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is a date.
napi_status napi_is_error(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given napi_value
represents an Error
object.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is an Error
.
napi_status napi_is_typedarray(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given napi_value
represents a TypedArray
.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is a typed array.
napi_status napi_is_dataview(napi_env env, napi_value value, bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The JavaScript value to check.[out] result
: Whether the given napi_value
represents a DataView
.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is a DataView
.
napi_status napi_strict_equals(napi_env env,\n napi_value lhs,\n napi_value rhs,\n bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] lhs
: The JavaScript value to check.[in] rhs
: The JavaScript value to check against.[out] result
: Whether the two napi_value
objects are equal.Returns napi_ok
if the API succeeded.
This API represents the invocation of the Strict Equality algorithm as\ndefined in Section 7.2.14 of the ECMAScript Language Specification.
", "type": "module", "displayName": "`napi_strict_equals`" }, { "textRaw": "`napi_detach_arraybuffer`", "name": "`napi_detach_arraybuffer`", "meta": { "added": [ "v13.0.0", "v12.16.0", "v10.22.0" ], "napiVersion": [ 7 ], "changes": [] }, "desc": "napi_status napi_detach_arraybuffer(napi_env env,\n napi_value arraybuffer)\n
\n[in] env
: The environment that the API is invoked under.[in] arraybuffer
: The JavaScript ArrayBuffer
to be detached.Returns napi_ok
if the API succeeded. If a non-detachable ArrayBuffer
is\npassed in it returns napi_detachable_arraybuffer_expected
.
Generally, an ArrayBuffer
is non-detachable if it has been detached before.\nThe engine may impose additional conditions on whether an ArrayBuffer
is\ndetachable. For example, V8 requires that the ArrayBuffer
be external,\nthat is, created with napi_create_external_arraybuffer
.
This API represents the invocation of the ArrayBuffer
detach operation as\ndefined in Section 24.1.1.3 of the ECMAScript Language Specification.
napi_status napi_is_detached_arraybuffer(napi_env env,\n napi_value arraybuffer,\n bool* result)\n
\n[in] env
: The environment that the API is invoked under.[in] arraybuffer
: The JavaScript ArrayBuffer
to be checked.[out] result
: Whether the arraybuffer
is detached.Returns napi_ok
if the API succeeded.
The ArrayBuffer
is considered detached if its internal data is null
.
This API represents the invocation of the ArrayBuffer
IsDetachedBuffer
\noperation as defined in Section 24.1.1.2 of the ECMAScript Language\nSpecification.
Node-API exposes a set of APIs to get and set properties on JavaScript\nobjects. Some of these types are documented under Section 7 of the\nECMAScript Language Specification.
\nProperties in JavaScript are represented as a tuple of a key and a value.\nFundamentally, all property keys in Node-API can be represented in one of the\nfollowing forms:
\nuint32_t
napi_value
. This can\nbe a napi_value
representing a string
, number
, or symbol
.Node-API values are represented by the type napi_value
.\nAny Node-API call that requires a JavaScript value takes in a napi_value
.\nHowever, it's the caller's responsibility to make sure that the\nnapi_value
in question is of the JavaScript type expected by the API.
The APIs documented in this section provide a simple interface to\nget and set properties on arbitrary JavaScript objects represented by\nnapi_value
.
For instance, consider the following JavaScript code snippet:
\nconst obj = {};\nobj.myProp = 123;\n
\nThe equivalent can be done using Node-API values with the following snippet:
\nnapi_status status = napi_generic_failure;\n\n// const obj = {}\nnapi_value obj, value;\nstatus = napi_create_object(env, &obj);\nif (status != napi_ok) return status;\n\n// Create a napi_value for 123\nstatus = napi_create_int32(env, 123, &value);\nif (status != napi_ok) return status;\n\n// obj.myProp = 123\nstatus = napi_set_named_property(env, obj, \"myProp\", value);\nif (status != napi_ok) return status;\n
\nIndexed properties can be set in a similar manner. Consider the following\nJavaScript snippet:
\nconst arr = [];\narr[123] = 'hello';\n
\nThe equivalent can be done using Node-API values with the following snippet:
\nnapi_status status = napi_generic_failure;\n\n// const arr = [];\nnapi_value arr, value;\nstatus = napi_create_array(env, &arr);\nif (status != napi_ok) return status;\n\n// Create a napi_value for 'hello'\nstatus = napi_create_string_utf8(env, \"hello\", NAPI_AUTO_LENGTH, &value);\nif (status != napi_ok) return status;\n\n// arr[123] = 'hello';\nstatus = napi_set_element(env, arr, 123, value);\nif (status != napi_ok) return status;\n
\nProperties can be retrieved using the APIs described in this section.\nConsider the following JavaScript snippet:
\nconst arr = [];\nconst value = arr[123];\n
\nThe following is the approximate equivalent of the Node-API counterpart:
\nnapi_status status = napi_generic_failure;\n\n// const arr = []\nnapi_value arr, value;\nstatus = napi_create_array(env, &arr);\nif (status != napi_ok) return status;\n\n// const value = arr[123]\nstatus = napi_get_element(env, arr, 123, &value);\nif (status != napi_ok) return status;\n
\nFinally, multiple properties can also be defined on an object for performance\nreasons. Consider the following JavaScript:
\nconst obj = {};\nObject.defineProperties(obj, {\n 'foo': { value: 123, writable: true, configurable: true, enumerable: true },\n 'bar': { value: 456, writable: true, configurable: true, enumerable: true },\n});\n
\nThe following is the approximate equivalent of the Node-API counterpart:
\nnapi_status status = napi_status_generic_failure;\n\n// const obj = {};\nnapi_value obj;\nstatus = napi_create_object(env, &obj);\nif (status != napi_ok) return status;\n\n// Create napi_values for 123 and 456\nnapi_value fooValue, barValue;\nstatus = napi_create_int32(env, 123, &fooValue);\nif (status != napi_ok) return status;\nstatus = napi_create_int32(env, 456, &barValue);\nif (status != napi_ok) return status;\n\n// Set the properties\nnapi_property_descriptor descriptors[] = {\n { \"foo\", NULL, NULL, NULL, NULL, fooValue, napi_writable | napi_configurable, NULL },\n { \"bar\", NULL, NULL, NULL, NULL, barValue, napi_writable | napi_configurable, NULL }\n}\nstatus = napi_define_properties(env,\n obj,\n sizeof(descriptors) / sizeof(descriptors[0]),\n descriptors);\nif (status != napi_ok) return status;\n
",
"modules": [
{
"textRaw": "Structures",
"name": "structures",
"modules": [
{
"textRaw": "`napi_property_attributes`",
"name": "`napi_property_attributes`",
"meta": {
"changes": [
{
"version": "v14.12.0",
"pr-url": "https://github.com/nodejs/node/pull/35214",
"description": "added `napi_default_method` and `napi_default_property`."
}
]
},
"desc": "typedef enum {\n napi_default = 0,\n napi_writable = 1 << 0,\n napi_enumerable = 1 << 1,\n napi_configurable = 1 << 2,\n\n // Used with napi_define_class to distinguish static properties\n // from instance properties. Ignored by napi_define_properties.\n napi_static = 1 << 10,\n\n // Default for class methods.\n napi_default_method = napi_writable | napi_configurable,\n\n // Default for object properties, like in JS obj[prop].\n napi_default_jsproperty = napi_writable |\n napi_enumerable |\n napi_configurable,\n} napi_property_attributes;\n
\nnapi_property_attributes
are flags used to control the behavior of properties\nset on a JavaScript object. Other than napi_static
they correspond to the\nattributes listed in Section 6.1.7.1\nof the ECMAScript Language Specification.\nThey can be one or more of the following bitflags:
napi_default
: No explicit attributes are set on the property. By default, a\nproperty is read only, not enumerable and not configurable.napi_writable
: The property is writable.napi_enumerable
: The property is enumerable.napi_configurable
: The property is configurable as defined in\nSection 6.1.7.1 of the ECMAScript Language Specification.napi_static
: The property will be defined as a static property on a class as\nopposed to an instance property, which is the default. This is used only by\nnapi_define_class
. It is ignored by napi_define_properties
.napi_default_method
: Like a method in a JS class, the property is\nconfigurable and writeable, but not enumerable.napi_default_jsproperty
: Like a property set via assignment in JavaScript,\nthe property is writable, enumerable, and configurable.typedef struct {\n // One of utf8name or name should be NULL.\n const char* utf8name;\n napi_value name;\n\n napi_callback method;\n napi_callback getter;\n napi_callback setter;\n napi_value value;\n\n napi_property_attributes attributes;\n void* data;\n} napi_property_descriptor;\n
\nutf8name
: Optional string describing the key for the property,\nencoded as UTF8. One of utf8name
or name
must be provided for the\nproperty.name
: Optional napi_value
that points to a JavaScript string or symbol\nto be used as the key for the property. One of utf8name
or name
must\nbe provided for the property.value
: The value that's retrieved by a get access of the property if the\nproperty is a data property. If this is passed in, set getter
, setter
,\nmethod
and data
to NULL
(since these members won't be used).getter
: A function to call when a get access of the property is performed.\nIf this is passed in, set value
and method
to NULL
(since these members\nwon't be used). The given function is called implicitly by the runtime when\nthe property is accessed from JavaScript code (or if a get on the property is\nperformed using a Node-API call). napi_callback
provides more details.setter
: A function to call when a set access of the property is performed.\nIf this is passed in, set value
and method
to NULL
(since these members\nwon't be used). The given function is called implicitly by the runtime when\nthe property is set from JavaScript code (or if a set on the property is\nperformed using a Node-API call). napi_callback
provides more details.method
: Set this to make the property descriptor object's value
\nproperty to be a JavaScript function represented by method
. If this is\npassed in, set value
, getter
and setter
to NULL
(since these members\nwon't be used). napi_callback
provides more details.attributes
: The attributes associated with the particular property. See\nnapi_property_attributes
.data
: The callback data passed into method
, getter
and setter
if this\nfunction is invoked.napi_status napi_get_property_names(napi_env env,\n napi_value object,\n napi_value* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to retrieve the properties.[out] result
: A napi_value
representing an array of JavaScript values\nthat represent the property names of the object. The API can be used to\niterate over result
using napi_get_array_length
\nand napi_get_element
.Returns napi_ok
if the API succeeded.
This API returns the names of the enumerable properties of object
as an array\nof strings. The properties of object
whose key is a symbol will not be\nincluded.
napi_get_all_property_names(napi_env env,\n napi_value object,\n napi_key_collection_mode key_mode,\n napi_key_filter key_filter,\n napi_key_conversion key_conversion,\n napi_value* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to retrieve the properties.[in] key_mode
: Whether to retrieve prototype properties as well.[in] key_filter
: Which properties to retrieve\n(enumerable/readable/writable).[in] key_conversion
: Whether to convert numbered property keys to strings.[out] result
: A napi_value
representing an array of JavaScript values\nthat represent the property names of the object. napi_get_array_length
\nand napi_get_element
can be used to iterate over result
.Returns napi_ok
if the API succeeded.
This API returns an array containing the names of the available properties\nof this object.
", "type": "module", "displayName": "`napi_get_all_property_names`" }, { "textRaw": "`napi_set_property`", "name": "`napi_set_property`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_set_property(napi_env env,\n napi_value object,\n napi_value key,\n napi_value value);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object on which to set the property.[in] key
: The name of the property to set.[in] value
: The property value.Returns napi_ok
if the API succeeded.
This API set a property on the Object
passed in.
napi_status napi_get_property(napi_env env,\n napi_value object,\n napi_value key,\n napi_value* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to retrieve the property.[in] key
: The name of the property to retrieve.[out] result
: The value of the property.Returns napi_ok
if the API succeeded.
This API gets the requested property from the Object
passed in.
napi_status napi_has_property(napi_env env,\n napi_value object,\n napi_value key,\n bool* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to query.[in] key
: The name of the property whose existence to check.[out] result
: Whether the property exists on the object or not.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in has the named property.
napi_status napi_delete_property(napi_env env,\n napi_value object,\n napi_value key,\n bool* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to query.[in] key
: The name of the property to delete.[out] result
: Whether the property deletion succeeded or not. result
can\noptionally be ignored by passing NULL
.Returns napi_ok
if the API succeeded.
This API attempts to delete the key
own property from object
.
napi_status napi_has_own_property(napi_env env,\n napi_value object,\n napi_value key,\n bool* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to query.[in] key
: The name of the own property whose existence to check.[out] result
: Whether the own property exists on the object or not.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in has the named own property. key
must\nbe a string
or a symbol
, or an error will be thrown. Node-API will not\nperform any conversion between data types.
napi_status napi_set_named_property(napi_env env,\n napi_value object,\n const char* utf8Name,\n napi_value value);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object on which to set the property.[in] utf8Name
: The name of the property to set.[in] value
: The property value.Returns napi_ok
if the API succeeded.
This method is equivalent to calling napi_set_property
with a napi_value
\ncreated from the string passed in as utf8Name
.
napi_status napi_get_named_property(napi_env env,\n napi_value object,\n const char* utf8Name,\n napi_value* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to retrieve the property.[in] utf8Name
: The name of the property to get.[out] result
: The value of the property.Returns napi_ok
if the API succeeded.
This method is equivalent to calling napi_get_property
with a napi_value
\ncreated from the string passed in as utf8Name
.
napi_status napi_has_named_property(napi_env env,\n napi_value object,\n const char* utf8Name,\n bool* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to query.[in] utf8Name
: The name of the property whose existence to check.[out] result
: Whether the property exists on the object or not.Returns napi_ok
if the API succeeded.
This method is equivalent to calling napi_has_property
with a napi_value
\ncreated from the string passed in as utf8Name
.
napi_status napi_set_element(napi_env env,\n napi_value object,\n uint32_t index,\n napi_value value);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to set the properties.[in] index
: The index of the property to set.[in] value
: The property value.Returns napi_ok
if the API succeeded.
This API sets an element on the Object
passed in.
napi_status napi_get_element(napi_env env,\n napi_value object,\n uint32_t index,\n napi_value* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to retrieve the property.[in] index
: The index of the property to get.[out] result
: The value of the property.Returns napi_ok
if the API succeeded.
This API gets the element at the requested index.
", "type": "module", "displayName": "`napi_get_element`" }, { "textRaw": "`napi_has_element`", "name": "`napi_has_element`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_has_element(napi_env env,\n napi_value object,\n uint32_t index,\n bool* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to query.[in] index
: The index of the property whose existence to check.[out] result
: Whether the property exists on the object or not.Returns napi_ok
if the API succeeded.
This API returns if the Object
passed in has an element at the\nrequested index.
napi_status napi_delete_element(napi_env env,\n napi_value object,\n uint32_t index,\n bool* result);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to query.[in] index
: The index of the property to delete.[out] result
: Whether the element deletion succeeded or not. result
can\noptionally be ignored by passing NULL
.Returns napi_ok
if the API succeeded.
This API attempts to delete the specified index
from object
.
napi_status napi_define_properties(napi_env env,\n napi_value object,\n size_t property_count,\n const napi_property_descriptor* properties);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object from which to retrieve the properties.[in] property_count
: The number of elements in the properties
array.[in] properties
: The array of property descriptors.Returns napi_ok
if the API succeeded.
This method allows the efficient definition of multiple properties on a given\nobject. The properties are defined using property descriptors (see\nnapi_property_descriptor
). Given an array of such property descriptors,\nthis API will set the properties on the object one at a time, as defined by\nDefineOwnProperty()
(described in Section 9.1.6 of the ECMA-262\nspecification).
napi_status napi_object_freeze(napi_env env,\n napi_value object);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to freeze.Returns napi_ok
if the API succeeded.
This method freezes a given object. This prevents new properties from\nbeing added to it, existing properties from being removed, prevents\nchanging the enumerability, configurability, or writability of existing\nproperties, and prevents the values of existing properties from being changed.\nIt also prevents the object's prototype from being changed. This is described\nin Section 19.1.2.6 of the\nECMA-262 specification.
", "type": "module", "displayName": "`napi_object_freeze`" }, { "textRaw": "`napi_object_seal`", "name": "`napi_object_seal`", "meta": { "added": [ "v14.14.0", "v12.20.0" ], "napiVersion": [ 8 ], "changes": [] }, "desc": "napi_status napi_object_seal(napi_env env,\n napi_value object);\n
\n[in] env
: The environment that the Node-API call is invoked under.[in] object
: The object to seal.Returns napi_ok
if the API succeeded.
This method seals a given object. This prevents new properties from being\nadded to it, as well as marking all existing properties as non-configurable.\nThis is described in Section 19.1.2.20\nof the ECMA-262 specification.
", "type": "module", "displayName": "`napi_object_seal`" } ], "type": "module", "displayName": "Functions" } ], "type": "misc", "displayName": "Working with JavaScript properties" }, { "textRaw": "Working with JavaScript functions", "name": "working_with_javascript_functions", "desc": "Node-API provides a set of APIs that allow JavaScript code to\ncall back into native code. Node-APIs that support calling back\ninto native code take in a callback functions represented by\nthe napi_callback
type. When the JavaScript VM calls back to\nnative code, the napi_callback
function provided is invoked. The APIs\ndocumented in this section allow the callback function to do the\nfollowing:
napi_value
back from the callback.Additionally, Node-API provides a set of functions which allow calling\nJavaScript functions from native code. One can either call a function\nlike a regular JavaScript function call, or as a constructor\nfunction.
\nAny non-NULL
data which is passed to this API via the data
field of the\nnapi_property_descriptor
items can be associated with object
and freed\nwhenever object
is garbage-collected by passing both object
and the data to\nnapi_add_finalizer
.
NAPI_EXTERN napi_status napi_call_function(napi_env env,\n napi_value recv,\n napi_value func,\n size_t argc,\n const napi_value* argv,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] recv
: The this
value passed to the called function.[in] func
: napi_value
representing the JavaScript function to be invoked.[in] argc
: The count of elements in the argv
array.[in] argv
: Array of napi_values
representing JavaScript values passed in\nas arguments to the function.[out] result
: napi_value
representing the JavaScript object returned.Returns napi_ok
if the API succeeded.
This method allows a JavaScript function object to be called from a native\nadd-on. This is the primary mechanism of calling back from the add-on's\nnative code into JavaScript. For the special case of calling into JavaScript\nafter an async operation, see napi_make_callback
.
A sample use case might look as follows. Consider the following JavaScript\nsnippet:
\nfunction AddTwo(num) {\n return num + 2;\n}\nglobal.AddTwo = AddTwo;\n
\nThen, the above function can be invoked from a native add-on using the\nfollowing code:
\n// Get the function named \"AddTwo\" on the global object\nnapi_value global, add_two, arg;\nnapi_status status = napi_get_global(env, &global);\nif (status != napi_ok) return;\n\nstatus = napi_get_named_property(env, global, \"AddTwo\", &add_two);\nif (status != napi_ok) return;\n\n// const arg = 1337\nstatus = napi_create_int32(env, 1337, &arg);\nif (status != napi_ok) return;\n\nnapi_value* argv = &arg;\nsize_t argc = 1;\n\n// AddTwo(arg);\nnapi_value return_val;\nstatus = napi_call_function(env, global, add_two, argc, argv, &return_val);\nif (status != napi_ok) return;\n\n// Convert the result back to a native type\nint32_t result;\nstatus = napi_get_value_int32(env, return_val, &result);\nif (status != napi_ok) return;\n
",
"type": "module",
"displayName": "`napi_call_function`"
},
{
"textRaw": "`napi_create_function`",
"name": "`napi_create_function`",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "napi_status napi_create_function(napi_env env,\n const char* utf8name,\n size_t length,\n napi_callback cb,\n void* data,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] utf8Name
: Optional name of the function encoded as UTF8. This is\nvisible within JavaScript as the new function object's name
property.[in] length
: The length of the utf8name
in bytes, or NAPI_AUTO_LENGTH
if\nit is null-terminated.[in] cb
: The native function which should be called when this function\nobject is invoked. napi_callback
provides more details.[in] data
: User-provided data context. This will be passed back into the\nfunction when invoked later.[out] result
: napi_value
representing the JavaScript function object for\nthe newly created function.Returns napi_ok
if the API succeeded.
This API allows an add-on author to create a function object in native code.\nThis is the primary mechanism to allow calling into the add-on's native code\nfrom JavaScript.
\nThe newly created function is not automatically visible from script after this\ncall. Instead, a property must be explicitly set on any object that is visible\nto JavaScript, in order for the function to be accessible from script.
\nIn order to expose a function as part of the\nadd-on's module exports, set the newly created function on the exports\nobject. A sample module might look as follows:
\nnapi_value SayHello(napi_env env, napi_callback_info info) {\n printf(\"Hello\\n\");\n return NULL;\n}\n\nnapi_value Init(napi_env env, napi_value exports) {\n napi_status status;\n\n napi_value fn;\n status = napi_create_function(env, NULL, 0, SayHello, NULL, &fn);\n if (status != napi_ok) return NULL;\n\n status = napi_set_named_property(env, exports, \"sayHello\", fn);\n if (status != napi_ok) return NULL;\n\n return exports;\n}\n\nNAPI_MODULE(NODE_GYP_MODULE_NAME, Init)\n
\nGiven the above code, the add-on can be used from JavaScript as follows:
\nconst myaddon = require('./addon');\nmyaddon.sayHello();\n
\nThe string passed to require()
is the name of the target in binding.gyp
\nresponsible for creating the .node
file.
Any non-NULL
data which is passed to this API via the data
parameter can\nbe associated with the resulting JavaScript function (which is returned in the\nresult
parameter) and freed whenever the function is garbage-collected by\npassing both the JavaScript function and the data to napi_add_finalizer
.
JavaScript Function
s are described in Section 19.2 of the ECMAScript\nLanguage Specification.
napi_status napi_get_cb_info(napi_env env,\n napi_callback_info cbinfo,\n size_t* argc,\n napi_value* argv,\n napi_value* thisArg,\n void** data)\n
\n[in] env
: The environment that the API is invoked under.[in] cbinfo
: The callback info passed into the callback function.[in-out] argc
: Specifies the length of the provided argv
array and\nreceives the actual count of arguments. argc
can\noptionally be ignored by passing NULL
.[out] argv
: C array of napi_value
s to which the arguments will be\ncopied. If there are more arguments than the provided count, only the\nrequested number of arguments are copied. If there are fewer arguments\nprovided than claimed, the rest of argv
is filled with napi_value
values\nthat represent undefined
. argv
can optionally be ignored by\npassing NULL
.[out] thisArg
: Receives the JavaScript this
argument for the call.\nthisArg
can optionally be ignored by passing NULL
.[out] data
: Receives the data pointer for the callback. data
can\noptionally be ignored by passing NULL
.Returns napi_ok
if the API succeeded.
This method is used within a callback function to retrieve details about the\ncall like the arguments and the this
pointer from a given callback info.
napi_status napi_get_new_target(napi_env env,\n napi_callback_info cbinfo,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] cbinfo
: The callback info passed into the callback function.[out] result
: The new.target
of the constructor call.Returns napi_ok
if the API succeeded.
This API returns the new.target
of the constructor call. If the current\ncallback is not a constructor call, the result is NULL
.
napi_status napi_new_instance(napi_env env,\n napi_value cons,\n size_t argc,\n napi_value* argv,\n napi_value* result)\n
\n[in] env
: The environment that the API is invoked under.[in] cons
: napi_value
representing the JavaScript function to be invoked\nas a constructor.[in] argc
: The count of elements in the argv
array.[in] argv
: Array of JavaScript values as napi_value
representing the\narguments to the constructor. If argc
is zero this parameter may be\nomitted by passing in NULL
.[out] result
: napi_value
representing the JavaScript object returned,\nwhich in this case is the constructed object.This method is used to instantiate a new JavaScript value using a given\nnapi_value
that represents the constructor for the object. For example,\nconsider the following snippet:
function MyObject(param) {\n this.param = param;\n}\n\nconst arg = 'hello';\nconst value = new MyObject(arg);\n
\nThe following can be approximated in Node-API using the following snippet:
\n// Get the constructor function MyObject\nnapi_value global, constructor, arg, value;\nnapi_status status = napi_get_global(env, &global);\nif (status != napi_ok) return;\n\nstatus = napi_get_named_property(env, global, \"MyObject\", &constructor);\nif (status != napi_ok) return;\n\n// const arg = \"hello\"\nstatus = napi_create_string_utf8(env, \"hello\", NAPI_AUTO_LENGTH, &arg);\nif (status != napi_ok) return;\n\nnapi_value* argv = &arg;\nsize_t argc = 1;\n\n// const value = new MyObject(arg)\nstatus = napi_new_instance(env, constructor, argc, argv, &value);\n
\nReturns napi_ok
if the API succeeded.
Node-API offers a way to \"wrap\" C++ classes and instances so that the class\nconstructor and methods can be called from JavaScript.
\nnapi_define_class
API defines a JavaScript class with constructor,\nstatic properties and methods, and instance properties and methods that\ncorrespond to the C++ class.napi_wrap
to wrap a new C++ instance in a JavaScript object,\nthen returns the wrapper object.napi_callback
C++ function is invoked. For an instance\ncallback, napi_unwrap
obtains the C++ instance that is the target of\nthe call.For wrapped objects it may be difficult to distinguish between a function\ncalled on a class prototype and a function called on an instance of a class.\nA common pattern used to address this problem is to save a persistent\nreference to the class constructor for later instanceof
checks.
napi_value MyClass_constructor = NULL;\nstatus = napi_get_reference_value(env, MyClass::es_constructor, &MyClass_constructor);\nassert(napi_ok == status);\nbool is_instance = false;\nstatus = napi_instanceof(env, es_this, MyClass_constructor, &is_instance);\nassert(napi_ok == status);\nif (is_instance) {\n // napi_unwrap() ...\n} else {\n // otherwise...\n}\n
\nThe reference must be freed once it is no longer needed.
\nThere are occasions where napi_instanceof()
is insufficient for ensuring that\na JavaScript object is a wrapper for a certain native type. This is the case\nespecially when wrapped JavaScript objects are passed back into the addon via\nstatic methods rather than as the this
value of prototype methods. In such\ncases there is a chance that they may be unwrapped incorrectly.
const myAddon = require('./build/Release/my_addon.node');\n\n// `openDatabase()` returns a JavaScript object that wraps a native database\n// handle.\nconst dbHandle = myAddon.openDatabase();\n\n// `query()` returns a JavaScript object that wraps a native query handle.\nconst queryHandle = myAddon.query(dbHandle, 'Gimme ALL the things!');\n\n// There is an accidental error in the line below. The first parameter to\n// `myAddon.queryHasRecords()` should be the database handle (`dbHandle`), not\n// the query handle (`query`), so the correct condition for the while-loop\n// should be\n//\n// myAddon.queryHasRecords(dbHandle, queryHandle)\n//\nwhile (myAddon.queryHasRecords(queryHandle, dbHandle)) {\n // retrieve records\n}\n
\nIn the above example myAddon.queryHasRecords()
is a method that accepts two\narguments. The first is a database handle and the second is a query handle.\nInternally, it unwraps the first argument and casts the resulting pointer to a\nnative database handle. It then unwraps the second argument and casts the\nresulting pointer to a query handle. If the arguments are passed in the wrong\norder, the casts will work, however, there is a good chance that the underlying\ndatabase operation will fail, or will even cause an invalid memory access.
To ensure that the pointer retrieved from the first argument is indeed a pointer\nto a database handle and, similarly, that the pointer retrieved from the second\nargument is indeed a pointer to a query handle, the implementation of\nqueryHasRecords()
has to perform a type validation. Retaining the JavaScript\nclass constructor from which the database handle was instantiated and the\nconstructor from which the query handle was instantiated in napi_ref
s can\nhelp, because napi_instanceof()
can then be used to ensure that the instances\npassed into queryHashRecords()
are indeed of the correct type.
Unfortunately, napi_instanceof()
does not protect against prototype\nmanipulation. For example, the prototype of the database handle instance can be\nset to the prototype of the constructor for query handle instances. In this\ncase, the database handle instance can appear as a query handle instance, and it\nwill pass the napi_instanceof()
test for a query handle instance, while still\ncontaining a pointer to a database handle.
To this end, Node-API provides type-tagging capabilities.
\nA type tag is a 128-bit integer unique to the addon. Node-API provides the\nnapi_type_tag
structure for storing a type tag. When such a value is passed\nalong with a JavaScript object or external stored in a napi_value
to\nnapi_type_tag_object()
, the JavaScript object will be \"marked\" with the\ntype tag. The \"mark\" is invisible on the JavaScript side. When a JavaScript\nobject arrives into a native binding, napi_check_object_type_tag()
can be used\nalong with the original type tag to determine whether the JavaScript object was\npreviously \"marked\" with the type tag. This creates a type-checking capability\nof a higher fidelity than napi_instanceof()
can provide, because such type-\ntagging survives prototype manipulation and addon unloading/reloading.
Continuing the above example, the following skeleton addon implementation\nillustrates the use of napi_type_tag_object()
and\nnapi_check_object_type_tag()
.
// This value is the type tag for a database handle. The command\n//\n// uuidgen | sed -r -e 's/-//g' -e 's/(.{16})(.*)/0x\\1, 0x\\2/'\n//\n// can be used to obtain the two values with which to initialize the structure.\nstatic const napi_type_tag DatabaseHandleTypeTag = {\n 0x1edf75a38336451d, 0xa5ed9ce2e4c00c38\n};\n\n// This value is the type tag for a query handle.\nstatic const napi_type_tag QueryHandleTypeTag = {\n 0x9c73317f9fad44a3, 0x93c3920bf3b0ad6a\n};\n\nstatic napi_value\nopenDatabase(napi_env env, napi_callback_info info) {\n napi_status status;\n napi_value result;\n\n // Perform the underlying action which results in a database handle.\n DatabaseHandle* dbHandle = open_database();\n\n // Create a new, empty JS object.\n status = napi_create_object(env, &result);\n if (status != napi_ok) return NULL;\n\n // Tag the object to indicate that it holds a pointer to a `DatabaseHandle`.\n status = napi_type_tag_object(env, result, &DatabaseHandleTypeTag);\n if (status != napi_ok) return NULL;\n\n // Store the pointer to the `DatabaseHandle` structure inside the JS object.\n status = napi_wrap(env, result, dbHandle, NULL, NULL, NULL);\n if (status != napi_ok) return NULL;\n\n return result;\n}\n\n// Later when we receive a JavaScript object purporting to be a database handle\n// we can use `napi_check_object_type_tag()` to ensure that it is indeed such a\n// handle.\n\nstatic napi_value\nquery(napi_env env, napi_callback_info info) {\n napi_status status;\n size_t argc = 2;\n napi_value argv[2];\n bool is_db_handle;\n\n status = napi_get_cb_info(env, info, &argc, argv, NULL, NULL);\n if (status != napi_ok) return NULL;\n\n // Check that the object passed as the first parameter has the previously\n // applied tag.\n status = napi_check_object_type_tag(env,\n argv[0],\n &DatabaseHandleTypeTag,\n &is_db_handle);\n if (status != napi_ok) return NULL;\n\n // Throw a `TypeError` if it doesn't.\n if (!is_db_handle) {\n // Throw a TypeError.\n return NULL;\n }\n}\n
",
"modules": [
{
"textRaw": "`napi_define_class`",
"name": "`napi_define_class`",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "napi_status napi_define_class(napi_env env,\n const char* utf8name,\n size_t length,\n napi_callback constructor,\n void* data,\n size_t property_count,\n const napi_property_descriptor* properties,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] utf8name
: Name of the JavaScript constructor function. For clarity,\nit is recommended to use the C++ class name when wrapping a C++ class.[in] length
: The length of the utf8name
in bytes, or NAPI_AUTO_LENGTH
\nif it is null-terminated.[in] constructor
: Callback function that handles constructing instances\nof the class. When wrapping a C++ class, this method must be a static member\nwith the napi_callback
signature. A C++ class constructor cannot be\nused. napi_callback
provides more details.[in] data
: Optional data to be passed to the constructor callback as\nthe data
property of the callback info.[in] property_count
: Number of items in the properties
array argument.[in] properties
: Array of property descriptors describing static and\ninstance data properties, accessors, and methods on the class\nSee napi_property_descriptor
.[out] result
: A napi_value
representing the constructor function for\nthe class.Returns napi_ok
if the API succeeded.
Defines a JavaScript class, including:
\nconstructor
can be used to\ninstantiate a new C++ class instance, which can then be placed inside the\nJavaScript object instance being constructed using napi_wrap
.napi_static
attribute).prototype
object. When wrapping a\nC++ class, non-static data properties, accessors, and methods of the C++\nclass can be called from the static functions given in the property\ndescriptors without the napi_static
attribute after retrieving the C++ class\ninstance placed inside the JavaScript object instance by using\nnapi_unwrap
.When wrapping a C++ class, the C++ constructor callback passed via constructor
\nshould be a static method on the class that calls the actual class constructor,\nthen wraps the new C++ instance in a JavaScript object, and returns the wrapper\nobject. See napi_wrap
for details.
The JavaScript constructor function returned from napi_define_class
is\noften saved and used later to construct new instances of the class from native\ncode, and/or to check whether provided values are instances of the class. In\nthat case, to prevent the function value from being garbage-collected, a\nstrong persistent reference to it can be created using\nnapi_create_reference
, ensuring that the reference count is kept >= 1.
Any non-NULL
data which is passed to this API via the data
parameter or via\nthe data
field of the napi_property_descriptor
array items can be associated\nwith the resulting JavaScript constructor (which is returned in the result
\nparameter) and freed whenever the class is garbage-collected by passing both\nthe JavaScript function and the data to napi_add_finalizer
.
napi_status napi_wrap(napi_env env,\n napi_value js_object,\n void* native_object,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_ref* result);\n
\n[in] env
: The environment that the API is invoked under.[in] js_object
: The JavaScript object that will be the wrapper for the\nnative object.[in] native_object
: The native instance that will be wrapped in the\nJavaScript object.[in] finalize_cb
: Optional native callback that can be used to free the\nnative instance when the JavaScript object has been garbage-collected.\nnapi_finalize
provides more details.[in] finalize_hint
: Optional contextual hint that is passed to the\nfinalize callback.[out] result
: Optional reference to the wrapped object.Returns napi_ok
if the API succeeded.
Wraps a native instance in a JavaScript object. The native instance can be\nretrieved later using napi_unwrap()
.
When JavaScript code invokes a constructor for a class that was defined using\nnapi_define_class()
, the napi_callback
for the constructor is invoked.\nAfter constructing an instance of the native class, the callback must then call\nnapi_wrap()
to wrap the newly constructed instance in the already-created\nJavaScript object that is the this
argument to the constructor callback.\n(That this
object was created from the constructor function's prototype
,\nso it already has definitions of all the instance properties and methods.)
Typically when wrapping a class instance, a finalize callback should be\nprovided that simply deletes the native instance that is received as the data
\nargument to the finalize callback.
The optional returned reference is initially a weak reference, meaning it\nhas a reference count of 0. Typically this reference count would be incremented\ntemporarily during async operations that require the instance to remain valid.
\nCaution: The optional returned reference (if obtained) should be deleted via\nnapi_delete_reference
ONLY in response to the finalize callback\ninvocation. If it is deleted before then, then the finalize callback may never\nbe invoked. Therefore, when obtaining a reference a finalize callback is also\nrequired in order to enable correct disposal of the reference.
Finalizer callbacks may be deferred, leaving a window where the object has\nbeen garbage collected (and the weak reference is invalid) but the finalizer\nhasn't been called yet. When using napi_get_reference_value()
on weak\nreferences returned by napi_wrap()
, you should still handle an empty result.
Calling napi_wrap()
a second time on an object will return an error. To\nassociate another native instance with the object, use napi_remove_wrap()
\nfirst.
napi_status napi_unwrap(napi_env env,\n napi_value js_object,\n void** result);\n
\n[in] env
: The environment that the API is invoked under.[in] js_object
: The object associated with the native instance.[out] result
: Pointer to the wrapped native instance.Returns napi_ok
if the API succeeded.
Retrieves a native instance that was previously wrapped in a JavaScript\nobject using napi_wrap()
.
When JavaScript code invokes a method or property accessor on the class, the\ncorresponding napi_callback
is invoked. If the callback is for an instance\nmethod or accessor, then the this
argument to the callback is the wrapper\nobject; the wrapped C++ instance that is the target of the call can be obtained\nthen by calling napi_unwrap()
on the wrapper object.
napi_status napi_remove_wrap(napi_env env,\n napi_value js_object,\n void** result);\n
\n[in] env
: The environment that the API is invoked under.[in] js_object
: The object associated with the native instance.[out] result
: Pointer to the wrapped native instance.Returns napi_ok
if the API succeeded.
Retrieves a native instance that was previously wrapped in the JavaScript\nobject js_object
using napi_wrap()
and removes the wrapping. If a finalize\ncallback was associated with the wrapping, it will no longer be called when the\nJavaScript object becomes garbage-collected.
napi_status napi_type_tag_object(napi_env env,\n napi_value js_object,\n const napi_type_tag* type_tag);\n
\n[in] env
: The environment that the API is invoked under.[in] js_object
: The JavaScript object or external to be marked.[in] type_tag
: The tag with which the object is to be marked.Returns napi_ok
if the API succeeded.
Associates the value of the type_tag
pointer with the JavaScript object or\nexternal. napi_check_object_type_tag()
can then be used to compare the tag\nthat was attached to the object with one owned by the addon to ensure that the\nobject has the right type.
If the object already has an associated type tag, this API will return\nnapi_invalid_arg
.
napi_status napi_check_object_type_tag(napi_env env,\n napi_value js_object,\n const napi_type_tag* type_tag,\n bool* result);\n
\n[in] env
: The environment that the API is invoked under.[in] js_object
: The JavaScript object or external whose type tag to\nexamine.[in] type_tag
: The tag with which to compare any tag found on the object.[out] result
: Whether the type tag given matched the type tag on the\nobject. false
is also returned if no type tag was found on the object.Returns napi_ok
if the API succeeded.
Compares the pointer given as type_tag
with any that can be found on\njs_object
. If no tag is found on js_object
or, if a tag is found but it does\nnot match type_tag
, then result
is set to false
. If a tag is found and it\nmatches type_tag
, then result
is set to true
.
napi_status napi_add_finalizer(napi_env env,\n napi_value js_object,\n void* finalize_data,\n node_api_nogc_finalize finalize_cb,\n void* finalize_hint,\n napi_ref* result);\n
\n[in] env
: The environment that the API is invoked under.[in] js_object
: The JavaScript object to which the native data will be\nattached.[in] finalize_data
: Optional data to be passed to finalize_cb
.[in] finalize_cb
: Native callback that will be used to free the\nnative data when the JavaScript object has been garbage-collected.\nnapi_finalize
provides more details.[in] finalize_hint
: Optional contextual hint that is passed to the\nfinalize callback.[out] result
: Optional reference to the JavaScript object.Returns napi_ok
if the API succeeded.
Adds a napi_finalize
callback which will be called when the JavaScript object\nin js_object
has been garbage-collected.
This API can be called multiple times on a single JavaScript object.
\nCaution: The optional returned reference (if obtained) should be deleted via\nnapi_delete_reference
ONLY in response to the finalize callback\ninvocation. If it is deleted before then, then the finalize callback may never\nbe invoked. Therefore, when obtaining a reference a finalize callback is also\nrequired in order to enable correct disposal of the reference.
napi_status node_api_post_finalizer(node_api_nogc_env env,\n napi_finalize finalize_cb,\n void* finalize_data,\n void* finalize_hint);\n
\n[in] env
: The environment that the API is invoked under.[in] finalize_cb
: Native callback that will be used to free the\nnative data when the JavaScript object has been garbage-collected.\nnapi_finalize
provides more details.[in] finalize_data
: Optional data to be passed to finalize_cb
.[in] finalize_hint
: Optional contextual hint that is passed to the\nfinalize callback.Returns napi_ok
if the API succeeded.
Schedules a napi_finalize
callback to be called asynchronously in the\nevent loop.
Normally, finalizers are called while the GC (garbage collector) collects\nobjects. At that point calling any Node-API that may cause changes in the GC\nstate will be disabled and will crash Node.js.
\nnode_api_post_finalizer
helps to work around this limitation by allowing the\nadd-on to defer calls to such Node-APIs to a point in time outside of the GC\nfinalization.
Addon modules often need to leverage async helpers from libuv as part of their\nimplementation. This allows them to schedule work to be executed asynchronously\nso that their methods can return in advance of the work being completed. This\nallows them to avoid blocking overall execution of the Node.js application.
\nNode-API provides an ABI-stable interface for these\nsupporting functions which covers the most common asynchronous use cases.
\nNode-API defines the napi_async_work
structure which is used to manage\nasynchronous workers. Instances are created/deleted with\nnapi_create_async_work
and napi_delete_async_work
.
The execute
and complete
callbacks are functions that will be\ninvoked when the executor is ready to execute and when it completes its\ntask respectively.
The execute
function should avoid making any Node-API calls\nthat could result in the execution of JavaScript or interaction with\nJavaScript objects. Most often, any code that needs to make Node-API\ncalls should be made in complete
callback instead.\nAvoid using the napi_env
parameter in the execute callback as\nit will likely execute JavaScript.
These functions implement the following interfaces:
\ntypedef void (*napi_async_execute_callback)(napi_env env,\n void* data);\ntypedef void (*napi_async_complete_callback)(napi_env env,\n napi_status status,\n void* data);\n
\nWhen these methods are invoked, the data
parameter passed will be the\naddon-provided void*
data that was passed into the\nnapi_create_async_work
call.
Once created the async worker can be queued\nfor execution using the napi_queue_async_work
function:
napi_status napi_queue_async_work(node_api_nogc_env env,\n napi_async_work work);\n
\nnapi_cancel_async_work
can be used if the work needs\nto be cancelled before the work has started execution.
After calling napi_cancel_async_work
, the complete
callback\nwill be invoked with a status value of napi_cancelled
.\nThe work should not be deleted before the complete
\ncallback invocation, even when it was cancelled.
napi_status napi_create_async_work(napi_env env,\n napi_value async_resource,\n napi_value async_resource_name,\n napi_async_execute_callback execute,\n napi_async_complete_callback complete,\n void* data,\n napi_async_work* result);\n
\n[in] env
: The environment that the API is invoked under.[in] async_resource
: An optional object associated with the async work\nthat will be passed to possible async_hooks
init
hooks.[in] async_resource_name
: Identifier for the kind of resource that is being\nprovided for diagnostic information exposed by the async_hooks
API.[in] execute
: The native function which should be called to execute the\nlogic asynchronously. The given function is called from a worker pool thread\nand can execute in parallel with the main event loop thread.[in] complete
: The native function which will be called when the\nasynchronous logic is completed or is cancelled. The given function is called\nfrom the main event loop thread. napi_async_complete_callback
provides\nmore details.[in] data
: User-provided data context. This will be passed back into the\nexecute and complete functions.[out] result
: napi_async_work*
which is the handle to the newly created\nasync work.Returns napi_ok
if the API succeeded.
This API allocates a work object that is used to execute logic asynchronously.\nIt should be freed using napi_delete_async_work
once the work is no longer\nrequired.
async_resource_name
should be a null-terminated, UTF-8-encoded string.
The async_resource_name
identifier is provided by the user and should be\nrepresentative of the type of async work being performed. It is also recommended\nto apply namespacing to the identifier, e.g. by including the module name. See\nthe async_hooks
documentation for more information.
napi_status napi_delete_async_work(napi_env env,\n napi_async_work work);\n
\n[in] env
: The environment that the API is invoked under.[in] work
: The handle returned by the call to napi_create_async_work
.Returns napi_ok
if the API succeeded.
This API frees a previously allocated work object.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_delete_async_work`" }, { "textRaw": "`napi_queue_async_work`", "name": "`napi_queue_async_work`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_queue_async_work(node_api_nogc_env env,\n napi_async_work work);\n
\n[in] env
: The environment that the API is invoked under.[in] work
: The handle returned by the call to napi_create_async_work
.Returns napi_ok
if the API succeeded.
This API requests that the previously allocated work be scheduled\nfor execution. Once it returns successfully, this API must not be called again\nwith the same napi_async_work
item or the result will be undefined.
napi_status napi_cancel_async_work(node_api_nogc_env env,\n napi_async_work work);\n
\n[in] env
: The environment that the API is invoked under.[in] work
: The handle returned by the call to napi_create_async_work
.Returns napi_ok
if the API succeeded.
This API cancels queued work if it has not yet\nbeen started. If it has already started executing, it cannot be\ncancelled and napi_generic_failure
will be returned. If successful,\nthe complete
callback will be invoked with a status value of\nnapi_cancelled
. The work should not be deleted before the complete
\ncallback invocation, even if it has been successfully cancelled.
This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_cancel_async_work`" } ], "type": "misc", "displayName": "Simple asynchronous operations" }, { "textRaw": "Custom asynchronous operations", "name": "custom_asynchronous_operations", "desc": "The simple asynchronous work APIs above may not be appropriate for every\nscenario. When using any other asynchronous mechanism, the following APIs\nare necessary to ensure an asynchronous operation is properly tracked by\nthe runtime.
", "modules": [ { "textRaw": "`napi_async_init`", "name": "`napi_async_init`", "meta": { "added": [ "v8.6.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_async_init(napi_env env,\n napi_value async_resource,\n napi_value async_resource_name,\n napi_async_context* result)\n
\n[in] env
: The environment that the API is invoked under.[in] async_resource
: Object associated with the async work\nthat will be passed to possible async_hooks
init
hooks and can be\naccessed by async_hooks.executionAsyncResource()
.[in] async_resource_name
: Identifier for the kind of resource that is being\nprovided for diagnostic information exposed by the async_hooks
API.[out] result
: The initialized async context.Returns napi_ok
if the API succeeded.
The async_resource
object needs to be kept alive until\nnapi_async_destroy
to keep async_hooks
related API acts correctly. In\norder to retain ABI compatibility with previous versions, napi_async_context
s\nare not maintaining the strong reference to the async_resource
objects to\navoid introducing causing memory leaks. However, if the async_resource
is\ngarbage collected by JavaScript engine before the napi_async_context
was\ndestroyed by napi_async_destroy
, calling napi_async_context
related APIs\nlike napi_open_callback_scope
and napi_make_callback
can cause\nproblems like loss of async context when using the AsyncLocalStorage
API.
In order to retain ABI compatibility with previous versions, passing NULL
\nfor async_resource
does not result in an error. However, this is not\nrecommended as this will result in undesirable behavior with async_hooks
\ninit
hooks and async_hooks.executionAsyncResource()
as the resource is\nnow required by the underlying async_hooks
implementation in order to provide\nthe linkage between async callbacks.
napi_status napi_async_destroy(napi_env env,\n napi_async_context async_context);\n
\n[in] env
: The environment that the API is invoked under.[in] async_context
: The async context to be destroyed.Returns napi_ok
if the API succeeded.
This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_async_destroy`" }, { "textRaw": "`napi_make_callback`", "name": "`napi_make_callback`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [ { "version": "v8.6.0", "pr-url": "https://github.com/nodejs/node/pull/15189", "description": "Added `async_context` parameter." } ] }, "desc": "NAPI_EXTERN napi_status napi_make_callback(napi_env env,\n napi_async_context async_context,\n napi_value recv,\n napi_value func,\n size_t argc,\n const napi_value* argv,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] async_context
: Context for the async operation that is\ninvoking the callback. This should normally be a value previously\nobtained from napi_async_init
.\nIn order to retain ABI compatibility with previous versions, passing NULL
\nfor async_context
does not result in an error. However, this results\nin incorrect operation of async hooks. Potential issues include loss of\nasync context when using the AsyncLocalStorage
API.[in] recv
: The this
value passed to the called function.[in] func
: napi_value
representing the JavaScript function to be invoked.[in] argc
: The count of elements in the argv
array.[in] argv
: Array of JavaScript values as napi_value
representing the\narguments to the function. If argc
is zero this parameter may be\nomitted by passing in NULL
.[out] result
: napi_value
representing the JavaScript object returned.Returns napi_ok
if the API succeeded.
This method allows a JavaScript function object to be called from a native\nadd-on. This API is similar to napi_call_function
. However, it is used to call\nfrom native code back into JavaScript after returning from an async\noperation (when there is no other script on the stack). It is a fairly simple\nwrapper around node::MakeCallback
.
Note it is not necessary to use napi_make_callback
from within a\nnapi_async_complete_callback
; in that situation the callback's async\ncontext has already been set up, so a direct call to napi_call_function
\nis sufficient and appropriate. Use of the napi_make_callback
function\nmay be required when implementing custom async behavior that does not use\nnapi_create_async_work
.
Any process.nextTick
s or Promises scheduled on the microtask queue by\nJavaScript during the callback are ran before returning back to C/C++.
NAPI_EXTERN napi_status napi_open_callback_scope(napi_env env,\n napi_value resource_object,\n napi_async_context context,\n napi_callback_scope* result)\n
\n[in] env
: The environment that the API is invoked under.[in] resource_object
: An object associated with the async work\nthat will be passed to possible async_hooks
init
hooks. This\nparameter has been deprecated and is ignored at runtime. Use the\nasync_resource
parameter in napi_async_init
instead.[in] context
: Context for the async operation that is invoking the callback.\nThis should be a value previously obtained from napi_async_init
.[out] result
: The newly created scope.There are cases (for example, resolving promises) where it is\nnecessary to have the equivalent of the scope associated with a callback\nin place when making certain Node-API calls. If there is no other script on\nthe stack the napi_open_callback_scope
and\nnapi_close_callback_scope
functions can be used to open/close\nthe required scope.
NAPI_EXTERN napi_status napi_close_callback_scope(napi_env env,\n napi_callback_scope scope)\n
\n[in] env
: The environment that the API is invoked under.[in] scope
: The scope to be closed.This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "`napi_close_callback_scope`" } ], "type": "misc", "displayName": "Custom asynchronous operations" }, { "textRaw": "Version management", "name": "version_management", "modules": [ { "textRaw": "`napi_get_node_version`", "name": "`napi_get_node_version`", "meta": { "added": [ "v8.4.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "typedef struct {\n uint32_t major;\n uint32_t minor;\n uint32_t patch;\n const char* release;\n} napi_node_version;\n\nnapi_status napi_get_node_version(node_api_nogc_env env,\n const napi_node_version** version);\n
\n[in] env
: The environment that the API is invoked under.[out] version
: A pointer to version information for Node.js itself.Returns napi_ok
if the API succeeded.
This function fills the version
struct with the major, minor, and patch\nversion of Node.js that is currently running, and the release
field with the\nvalue of process.release.name
.
The returned buffer is statically allocated and does not need to be freed.
", "type": "module", "displayName": "`napi_get_node_version`" }, { "textRaw": "`napi_get_version`", "name": "`napi_get_version`", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_version(node_api_nogc_env env,\n uint32_t* result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: The highest version of Node-API supported.Returns napi_ok
if the API succeeded.
This API returns the highest Node-API version supported by the\nNode.js runtime. Node-API is planned to be additive such that\nnewer releases of Node.js may support additional API functions.\nIn order to allow an addon to use a newer function when running with\nversions of Node.js that support it, while providing\nfallback behavior when running with Node.js versions that don't\nsupport it:
\nnapi_get_version()
to determine if the API is available.uv_dlsym()
.NAPI_EXTERN napi_status napi_adjust_external_memory(node_api_nogc_env env,\n int64_t change_in_bytes,\n int64_t* result);\n
\n[in] env
: The environment that the API is invoked under.[in] change_in_bytes
: The change in externally allocated memory that is kept\nalive by JavaScript objects.[out] result
: The adjusted valueReturns napi_ok
if the API succeeded.
This function gives V8 an indication of the amount of externally allocated\nmemory that is kept alive by JavaScript objects (i.e. a JavaScript object\nthat points to its own memory allocated by a native addon). Registering\nexternally allocated memory will trigger global garbage collections more\noften than it would otherwise.
", "type": "module", "displayName": "`napi_adjust_external_memory`" } ], "type": "misc", "displayName": "Memory management" }, { "textRaw": "Promises", "name": "promises", "desc": "Node-API provides facilities for creating Promise
objects as described in\nSection 25.4 of the ECMA specification. It implements promises as a pair of\nobjects. When a promise is created by napi_create_promise()
, a \"deferred\"\nobject is created and returned alongside the Promise
. The deferred object is\nbound to the created Promise
and is the only means to resolve or reject the\nPromise
using napi_resolve_deferred()
or napi_reject_deferred()
. The\ndeferred object that is created by napi_create_promise()
is freed by\nnapi_resolve_deferred()
or napi_reject_deferred()
. The Promise
object may\nbe returned to JavaScript where it can be used in the usual fashion.
For example, to create a promise and pass it to an asynchronous worker:
\nnapi_deferred deferred;\nnapi_value promise;\nnapi_status status;\n\n// Create the promise.\nstatus = napi_create_promise(env, &deferred, &promise);\nif (status != napi_ok) return NULL;\n\n// Pass the deferred to a function that performs an asynchronous action.\ndo_something_asynchronous(deferred);\n\n// Return the promise to JS\nreturn promise;\n
\nThe above function do_something_asynchronous()
would perform its asynchronous\naction and then it would resolve or reject the deferred, thereby concluding the\npromise and freeing the deferred:
napi_deferred deferred;\nnapi_value undefined;\nnapi_status status;\n\n// Create a value with which to conclude the deferred.\nstatus = napi_get_undefined(env, &undefined);\nif (status != napi_ok) return NULL;\n\n// Resolve or reject the promise associated with the deferred depending on\n// whether the asynchronous action succeeded.\nif (asynchronous_action_succeeded) {\n status = napi_resolve_deferred(env, deferred, undefined);\n} else {\n status = napi_reject_deferred(env, deferred, undefined);\n}\nif (status != napi_ok) return NULL;\n\n// At this point the deferred has been freed, so we should assign NULL to it.\ndeferred = NULL;\n
",
"modules": [
{
"textRaw": "`napi_create_promise`",
"name": "`napi_create_promise`",
"meta": {
"added": [
"v8.5.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "napi_status napi_create_promise(napi_env env,\n napi_deferred* deferred,\n napi_value* promise);\n
\n[in] env
: The environment that the API is invoked under.[out] deferred
: A newly created deferred object which can later be passed to\nnapi_resolve_deferred()
or napi_reject_deferred()
to resolve resp. reject\nthe associated promise.[out] promise
: The JavaScript promise associated with the deferred object.Returns napi_ok
if the API succeeded.
This API creates a deferred object and a JavaScript promise.
", "type": "module", "displayName": "`napi_create_promise`" }, { "textRaw": "`napi_resolve_deferred`", "name": "`napi_resolve_deferred`", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_resolve_deferred(napi_env env,\n napi_deferred deferred,\n napi_value resolution);\n
\n[in] env
: The environment that the API is invoked under.[in] deferred
: The deferred object whose associated promise to resolve.[in] resolution
: The value with which to resolve the promise.This API resolves a JavaScript promise by way of the deferred object\nwith which it is associated. Thus, it can only be used to resolve JavaScript\npromises for which the corresponding deferred object is available. This\neffectively means that the promise must have been created using\nnapi_create_promise()
and the deferred object returned from that call must\nhave been retained in order to be passed to this API.
The deferred object is freed upon successful completion.
", "type": "module", "displayName": "`napi_resolve_deferred`" }, { "textRaw": "`napi_reject_deferred`", "name": "`napi_reject_deferred`", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_reject_deferred(napi_env env,\n napi_deferred deferred,\n napi_value rejection);\n
\n[in] env
: The environment that the API is invoked under.[in] deferred
: The deferred object whose associated promise to resolve.[in] rejection
: The value with which to reject the promise.This API rejects a JavaScript promise by way of the deferred object\nwith which it is associated. Thus, it can only be used to reject JavaScript\npromises for which the corresponding deferred object is available. This\neffectively means that the promise must have been created using\nnapi_create_promise()
and the deferred object returned from that call must\nhave been retained in order to be passed to this API.
The deferred object is freed upon successful completion.
", "type": "module", "displayName": "`napi_reject_deferred`" }, { "textRaw": "`napi_is_promise`", "name": "`napi_is_promise`", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_is_promise(napi_env env,\n napi_value value,\n bool* is_promise);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: The value to examine[out] is_promise
: Flag indicating whether promise
is a native promise\nobject (that is, a promise object created by the underlying engine).Node-API provides an API for executing a string containing JavaScript using the\nunderlying JavaScript engine.
", "modules": [ { "textRaw": "`napi_run_script`", "name": "`napi_run_script`", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_run_script(napi_env env,\n napi_value script,\n napi_value* result);\n
\n[in] env
: The environment that the API is invoked under.[in] script
: A JavaScript string containing the script to execute.[out] result
: The value resulting from having executed the script.This function executes a string of JavaScript code and returns its result with\nthe following caveats:
\neval
, this function does not allow the script to access the current\nlexical scope, and therefore also does not allow to access the\nmodule scope, meaning that pseudo-globals such as require
will not be\navailable.var
declarations\nin the script will be added to the global
object. Variable declarations\nmade using let
and const
will be visible globally, but will not be added\nto the global
object.this
is global
within the script.Node-API provides a function for getting the current event loop associated with\na specific napi_env
.
NAPI_EXTERN napi_status napi_get_uv_event_loop(node_api_nogc_env env,\n struct uv_loop_s** loop);\n
\n[in] env
: The environment that the API is invoked under.[out] loop
: The current libuv loop instance.JavaScript functions can normally only be called from a native addon's main\nthread. If an addon creates additional threads, then Node-API functions that\nrequire a napi_env
, napi_value
, or napi_ref
must not be called from those\nthreads.
When an addon has additional threads and JavaScript functions need to be invoked\nbased on the processing completed by those threads, those threads must\ncommunicate with the addon's main thread so that the main thread can invoke the\nJavaScript function on their behalf. The thread-safe function APIs provide an\neasy way to do this.
\nThese APIs provide the type napi_threadsafe_function
as well as APIs to\ncreate, destroy, and call objects of this type.\nnapi_create_threadsafe_function()
creates a persistent reference to a\nnapi_value
that holds a JavaScript function which can be called from multiple\nthreads. The calls happen asynchronously. This means that values with which the\nJavaScript callback is to be called will be placed in a queue, and, for each\nvalue in the queue, a call will eventually be made to the JavaScript function.
Upon creation of a napi_threadsafe_function
a napi_finalize
callback can be\nprovided. This callback will be invoked on the main thread when the thread-safe\nfunction is about to be destroyed. It receives the context and the finalize data\ngiven during construction, and provides an opportunity for cleaning up after the\nthreads e.g. by calling uv_thread_join()
. Aside from the main loop thread,\nno threads should be using the thread-safe function after the finalize callback\ncompletes.
The context
given during the call to napi_create_threadsafe_function()
can\nbe retrieved from any thread with a call to\nnapi_get_threadsafe_function_context()
.
napi_call_threadsafe_function()
can be used for initiating a call into\nJavaScript. napi_call_threadsafe_function()
accepts a parameter which controls\nwhether the API behaves blockingly. If set to napi_tsfn_nonblocking
, the API\nbehaves non-blockingly, returning napi_queue_full
if the queue was full,\npreventing data from being successfully added to the queue. If set to\nnapi_tsfn_blocking
, the API blocks until space becomes available in the queue.\nnapi_call_threadsafe_function()
never blocks if the thread-safe function was\ncreated with a maximum queue size of 0.
napi_call_threadsafe_function()
should not be called with napi_tsfn_blocking
\nfrom a JavaScript thread, because, if the queue is full, it may cause the\nJavaScript thread to deadlock.
The actual call into JavaScript is controlled by the callback given via the\ncall_js_cb
parameter. call_js_cb
is invoked on the main thread once for each\nvalue that was placed into the queue by a successful call to\nnapi_call_threadsafe_function()
. If such a callback is not given, a default\ncallback will be used, and the resulting JavaScript call will have no arguments.\nThe call_js_cb
callback receives the JavaScript function to call as a\nnapi_value
in its parameters, as well as the void*
context pointer used when\ncreating the napi_threadsafe_function
, and the next data pointer that was\ncreated by one of the secondary threads. The callback can then use an API such\nas napi_call_function()
to call into JavaScript.
The callback may also be invoked with env
and call_js_cb
both set to NULL
\nto indicate that calls into JavaScript are no longer possible, while items\nremain in the queue that may need to be freed. This normally occurs when the\nNode.js process exits while there is a thread-safe function still active.
It is not necessary to call into JavaScript via napi_make_callback()
because\nNode-API runs call_js_cb
in a context appropriate for callbacks.
Zero or more queued items may be invoked in each tick of the event loop.\nApplications should not depend on a specific behavior other than progress in\ninvoking callbacks will be made and events will be invoked\nas time moves forward.
", "type": "module", "displayName": "Calling a thread-safe function" }, { "textRaw": "Reference counting of thread-safe functions", "name": "reference_counting_of_thread-safe_functions", "desc": "Threads can be added to and removed from a napi_threadsafe_function
object\nduring its existence. Thus, in addition to specifying an initial number of\nthreads upon creation, napi_acquire_threadsafe_function
can be called to\nindicate that a new thread will start making use of the thread-safe function.\nSimilarly, napi_release_threadsafe_function
can be called to indicate that an\nexisting thread will stop making use of the thread-safe function.
napi_threadsafe_function
objects are destroyed when every thread which uses\nthe object has called napi_release_threadsafe_function()
or has received a\nreturn status of napi_closing
in response to a call to\nnapi_call_threadsafe_function
. The queue is emptied before the\nnapi_threadsafe_function
is destroyed. napi_release_threadsafe_function()
\nshould be the last API call made in conjunction with a given\nnapi_threadsafe_function
, because after the call completes, there is no\nguarantee that the napi_threadsafe_function
is still allocated. For the same\nreason, do not use a thread-safe function\nafter receiving a return value of napi_closing
in response to a call to\nnapi_call_threadsafe_function
. Data associated with the\nnapi_threadsafe_function
can be freed in its napi_finalize
callback which\nwas passed to napi_create_threadsafe_function()
. The parameter\ninitial_thread_count
of napi_create_threadsafe_function
marks the initial\nnumber of acquisitions of the thread-safe functions, instead of calling\nnapi_acquire_threadsafe_function
multiple times at creation.
Once the number of threads making use of a napi_threadsafe_function
reaches\nzero, no further threads can start making use of it by calling\nnapi_acquire_threadsafe_function()
. In fact, all subsequent API calls\nassociated with it, except napi_release_threadsafe_function()
, will return an\nerror value of napi_closing
.
The thread-safe function can be \"aborted\" by giving a value of napi_tsfn_abort
\nto napi_release_threadsafe_function()
. This will cause all subsequent APIs\nassociated with the thread-safe function except\nnapi_release_threadsafe_function()
to return napi_closing
even before its\nreference count reaches zero. In particular, napi_call_threadsafe_function()
\nwill return napi_closing
, thus informing the threads that it is no longer\npossible to make asynchronous calls to the thread-safe function. This can be\nused as a criterion for terminating the thread. Upon receiving a return value\nof napi_closing
from napi_call_threadsafe_function()
a thread must not use\nthe thread-safe function anymore because it is no longer guaranteed to\nbe allocated.
Similarly to libuv handles, thread-safe functions can be \"referenced\" and\n\"unreferenced\". A \"referenced\" thread-safe function will cause the event loop on\nthe thread on which it is created to remain alive until the thread-safe function\nis destroyed. In contrast, an \"unreferenced\" thread-safe function will not\nprevent the event loop from exiting. The APIs napi_ref_threadsafe_function
and\nnapi_unref_threadsafe_function
exist for this purpose.
Neither does napi_unref_threadsafe_function
mark the thread-safe functions as\nable to be destroyed nor does napi_ref_threadsafe_function
prevent it from\nbeing destroyed.
NAPI_EXTERN napi_status\nnapi_create_threadsafe_function(napi_env env,\n napi_value func,\n napi_value async_resource,\n napi_value async_resource_name,\n size_t max_queue_size,\n size_t initial_thread_count,\n void* thread_finalize_data,\n napi_finalize thread_finalize_cb,\n void* context,\n napi_threadsafe_function_call_js call_js_cb,\n napi_threadsafe_function* result);\n
\n[in] env
: The environment that the API is invoked under.[in] func
: An optional JavaScript function to call from another thread. It\nmust be provided if NULL
is passed to call_js_cb
.[in] async_resource
: An optional object associated with the async work that\nwill be passed to possible async_hooks
init
hooks.[in] async_resource_name
: A JavaScript string to provide an identifier for\nthe kind of resource that is being provided for diagnostic information exposed\nby the async_hooks
API.[in] max_queue_size
: Maximum size of the queue. 0
for no limit.[in] initial_thread_count
: The initial number of acquisitions, i.e. the\ninitial number of threads, including the main thread, which will be making use\nof this function.[in] thread_finalize_data
: Optional data to be passed to thread_finalize_cb
.[in] thread_finalize_cb
: Optional function to call when the\nnapi_threadsafe_function
is being destroyed.[in] context
: Optional data to attach to the resulting\nnapi_threadsafe_function
.[in] call_js_cb
: Optional callback which calls the JavaScript function in\nresponse to a call on a different thread. This callback will be called on the\nmain thread. If not given, the JavaScript function will be called with no\nparameters and with undefined
as its this
value.\nnapi_threadsafe_function_call_js
provides more details.[out] result
: The asynchronous thread-safe JavaScript function.Change History:
\nExperimental (NAPI_EXPERIMENTAL
is defined):
Uncaught exceptions thrown in call_js_cb
are handled with the\n'uncaughtException'
event, instead of being ignored.
NAPI_EXTERN napi_status\nnapi_get_threadsafe_function_context(napi_threadsafe_function func,\n void** result);\n
\n[in] func
: The thread-safe function for which to retrieve the context.[out] result
: The location where to store the context.This API may be called from any thread which makes use of func
.
NAPI_EXTERN napi_status\nnapi_call_threadsafe_function(napi_threadsafe_function func,\n void* data,\n napi_threadsafe_function_call_mode is_blocking);\n
\n[in] func
: The asynchronous thread-safe JavaScript function to invoke.[in] data
: Data to send into JavaScript via the callback call_js_cb
\nprovided during the creation of the thread-safe JavaScript function.[in] is_blocking
: Flag whose value can be either napi_tsfn_blocking
to\nindicate that the call should block if the queue is full or\nnapi_tsfn_nonblocking
to indicate that the call should return immediately\nwith a status of napi_queue_full
whenever the queue is full.This API should not be called with napi_tsfn_blocking
from a JavaScript\nthread, because, if the queue is full, it may cause the JavaScript thread to\ndeadlock.
This API will return napi_closing
if napi_release_threadsafe_function()
was\ncalled with abort
set to napi_tsfn_abort
from any thread. The value is only\nadded to the queue if the API returns napi_ok
.
This API may be called from any thread which makes use of func
.
NAPI_EXTERN napi_status\nnapi_acquire_threadsafe_function(napi_threadsafe_function func);\n
\n[in] func
: The asynchronous thread-safe JavaScript function to start making\nuse of.A thread should call this API before passing func
to any other thread-safe\nfunction APIs to indicate that it will be making use of func
. This prevents\nfunc
from being destroyed when all other threads have stopped making use of\nit.
This API may be called from any thread which will start making use of func
.
NAPI_EXTERN napi_status\nnapi_release_threadsafe_function(napi_threadsafe_function func,\n napi_threadsafe_function_release_mode mode);\n
\n[in] func
: The asynchronous thread-safe JavaScript function whose reference\ncount to decrement.[in] mode
: Flag whose value can be either napi_tsfn_release
to indicate\nthat the current thread will make no further calls to the thread-safe\nfunction, or napi_tsfn_abort
to indicate that in addition to the current\nthread, no other thread should make any further calls to the thread-safe\nfunction. If set to napi_tsfn_abort
, further calls to\nnapi_call_threadsafe_function()
will return napi_closing
, and no further\nvalues will be placed in the queue.A thread should call this API when it stops making use of func
. Passing func
\nto any thread-safe APIs after having called this API has undefined results, as\nfunc
may have been destroyed.
This API may be called from any thread which will stop making use of func
.
NAPI_EXTERN napi_status\nnapi_ref_threadsafe_function(node_api_nogc_env env, napi_threadsafe_function func);\n
\n[in] env
: The environment that the API is invoked under.[in] func
: The thread-safe function to reference.This API is used to indicate that the event loop running on the main thread\nshould not exit until func
has been destroyed. Similar to uv_ref
it is\nalso idempotent.
Neither does napi_unref_threadsafe_function
mark the thread-safe functions as\nable to be destroyed nor does napi_ref_threadsafe_function
prevent it from\nbeing destroyed. napi_acquire_threadsafe_function
and\nnapi_release_threadsafe_function
are available for that purpose.
This API may only be called from the main thread.
", "type": "module", "displayName": "`napi_ref_threadsafe_function`" }, { "textRaw": "`napi_unref_threadsafe_function`", "name": "`napi_unref_threadsafe_function`", "meta": { "added": [ "v10.6.0" ], "napiVersion": [ 4 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\nnapi_unref_threadsafe_function(node_api_nogc_env env, napi_threadsafe_function func);\n
\n[in] env
: The environment that the API is invoked under.[in] func
: The thread-safe function to unreference.This API is used to indicate that the event loop running on the main thread\nmay exit before func
is destroyed. Similar to uv_unref
it is also\nidempotent.
This API may only be called from the main thread.
", "type": "module", "displayName": "`napi_unref_threadsafe_function`" } ], "type": "misc", "displayName": "Asynchronous thread-safe function calls" }, { "textRaw": "Miscellaneous utilities", "name": "miscellaneous_utilities", "modules": [ { "textRaw": "`node_api_get_module_file_name`", "name": "`node_api_get_module_file_name`", "meta": { "added": [ "v15.9.0", "v14.18.0", "v12.22.0" ], "napiVersion": [ 9 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\nnode_api_get_module_file_name(node_api_nogc_env env, const char** result);\n\n
\n[in] env
: The environment that the API is invoked under.[out] result
: A URL containing the absolute path of the\nlocation from which the add-on was loaded. For a file on the local\nfile system it will start with file://
. The string is null-terminated and\nowned by env
and must thus not be modified or freed.result
may be an empty string if the add-on loading process fails to establish\nthe add-on's file name during loading.
Node.js comes with a variety of CLI options. These options expose built-in\ndebugging, multiple ways to execute scripts, and other helpful runtime options.
\nTo view this documentation as a manual page in a terminal, run man node
.
node [options] [V8 options] [<program-entry-point> | -e \"script\" | -] [--] [arguments]
node inspect [<program-entry-point> | -e \"script\" | <host>:<port>] …
node --v8-options
Execute without arguments to start the REPL.
\nFor more info about node inspect
, see the debugger documentation.
The program entry point is a specifier-like string. If the string is not an\nabsolute path, it's resolved as a relative path from the current working\ndirectory. That path is then resolved by CommonJS module loader, or by the\nES module loader if --experimental-default-type=module
\nis passed. If no corresponding file is found, an error is thrown.
If a file is found, its path will be passed to the\nES module loader under any of the following conditions:
\n--import
or\n--experimental-default-type=module
..mjs
extension..cjs
extension, and the nearest parent\npackage.json
file contains a top-level \"type\"
field with a value of\n\"module\"
.Otherwise, the file is loaded using the CommonJS module loader. See\nModules loaders for more details.
", "modules": [ { "textRaw": "ECMAScript modules loader entry point caveat", "name": "ecmascript_modules_loader_entry_point_caveat", "desc": "When loading, the ES module loader loads the program\nentry point, the node
command will accept as input only files with .js
,\n.mjs
, or .cjs
extensions; with .wasm
extensions when\n--experimental-wasm-modules
is enabled; and with no extension when\n--experimental-default-type=module
is passed.
All options, including V8 options, allow words to be separated by both\ndashes (-
) or underscores (_
). For example, --pending-deprecation
is\nequivalent to --pending_deprecation
.
If an option that takes a single value (such as --max-http-header-size
) is\npassed more than once, then the last passed value is used. Options from the\ncommand line take precedence over options passed through the NODE_OPTIONS
\nenvironment variable.
Alias for stdin. Analogous to the use of -
in other command-line utilities,\nmeaning that the script is read from stdin, and the rest of the options\nare passed to that script.
Indicate the end of node options. Pass the rest of the arguments to the script.\nIf no script filename or eval/print script is supplied prior to this, then\nthe next argument is used as a script filename.
", "type": "module", "displayName": "`--`" }, { "textRaw": "`--abort-on-uncaught-exception`", "name": "`--abort-on-uncaught-exception`", "meta": { "added": [ "v0.10.8" ], "changes": [] }, "desc": "Aborting instead of exiting causes a core file to be generated for post-mortem\nanalysis using a debugger (such as lldb
, gdb
, and mdb
).
If this flag is passed, the behavior can still be set to not abort through\nprocess.setUncaughtExceptionCaptureCallback()
(and through usage of the\nnode:domain
module that uses it).
When using the Permission Model, the process will not be able to use\nnative addons by default.\nAttempts to do so will throw an ERR_DLOPEN_DISABLED
unless the\nuser explicitly passes the --allow-addons
flag when starting Node.js.
Example:
\n// Attempt to require an native addon\nrequire('nodejs-addon-example');\n
\n$ node --experimental-permission --allow-fs-read=* index.js\nnode:internal/modules/cjs/loader:1319\n return process.dlopen(module, path.toNamespacedPath(filename));\n ^\n\nError: Cannot load native addon because loading addons is disabled.\n at Module._extensions..node (node:internal/modules/cjs/loader:1319:18)\n at Module.load (node:internal/modules/cjs/loader:1091:32)\n at Module._load (node:internal/modules/cjs/loader:938:12)\n at Module.require (node:internal/modules/cjs/loader:1115:19)\n at require (node:internal/modules/helpers:130:18)\n at Object.<anonymous> (/home/index.js:1:15)\n at Module._compile (node:internal/modules/cjs/loader:1233:14)\n at Module._extensions..js (node:internal/modules/cjs/loader:1287:10)\n at Module.load (node:internal/modules/cjs/loader:1091:32)\n at Module._load (node:internal/modules/cjs/loader:938:12) {\n code: 'ERR_DLOPEN_DISABLED'\n}\n
",
"type": "module",
"displayName": "`--allow-addons`"
},
{
"textRaw": "`--allow-child-process`",
"name": "`--allow-child-process`",
"meta": {
"added": [
"v20.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": ".1 - Active development",
"desc": "When using the Permission Model, the process will not be able to spawn any\nchild process by default.\nAttempts to do so will throw an ERR_ACCESS_DENIED
unless the\nuser explicitly passes the --allow-child-process
flag when starting Node.js.
Example:
\nconst childProcess = require('node:child_process');\n// Attempt to bypass the permission\nchildProcess.spawn('node', ['-e', 'require(\"fs\").writeFileSync(\"/new-file\", \"example\")']);\n
\n$ node --experimental-permission --allow-fs-read=* index.js\nnode:internal/child_process:388\n const err = this._handle.spawn(options);\n ^\nError: Access to this API has been restricted\n at ChildProcess.spawn (node:internal/child_process:388:28)\n at Object.spawn (node:child_process:723:9)\n at Object.<anonymous> (/home/index.js:3:14)\n at Module._compile (node:internal/modules/cjs/loader:1120:14)\n at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n at Module.load (node:internal/modules/cjs/loader:998:32)\n at Module._load (node:internal/modules/cjs/loader:839:12)\n at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n at node:internal/main/run_main_module:17:47 {\n code: 'ERR_ACCESS_DENIED',\n permission: 'ChildProcess'\n}\n
",
"type": "module",
"displayName": "`--allow-child-process`"
},
{
"textRaw": "`--allow-fs-read`",
"name": "`--allow-fs-read`",
"meta": {
"added": [
"v20.0.0"
],
"changes": [
{
"version": "v20.7.0",
"pr-url": "https://github.com/nodejs/node/pull/49047",
"description": "Paths delimited by comma (`,`) are no longer allowed."
}
]
},
"stability": 1,
"stabilityText": ".1 - Active development",
"desc": "This flag configures file system read permissions using\nthe Permission Model.
\nThe valid arguments for the --allow-fs-read
flag are:
*
- To allow all FileSystemRead
operations.--allow-fs-read
flags.\nExample --allow-fs-read=/folder1/ --allow-fs-read=/folder1/
Paths delimited by comma (,
) are no longer allowed.\nWhen passing a single flag with a comma a warning will be displayed.
Examples can be found in the File System Permissions documentation.
\nRelative paths are NOT yet supported by the CLI flag.
\nThe initializer module also needs to be allowed. Consider the following example:
\n$ node --experimental-permission t.js\nnode:internal/modules/cjs/loader:162\n const result = internalModuleStat(filename);\n ^\n\nError: Access to this API has been restricted\n at stat (node:internal/modules/cjs/loader:162:18)\n at Module._findPath (node:internal/modules/cjs/loader:640:16)\n at resolveMainPath (node:internal/modules/run_main:15:25)\n at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:53:24)\n at node:internal/main/run_main_module:23:47 {\n code: 'ERR_ACCESS_DENIED',\n permission: 'FileSystemRead',\n resource: '/Users/rafaelgss/repos/os/node/t.js'\n}\n
\nThe process needs to have access to the index.js
module:
node --experimental-permission --allow-fs-read=/path/to/index.js index.js\n
",
"type": "module",
"displayName": "`--allow-fs-read`"
},
{
"textRaw": "`--allow-fs-write`",
"name": "`--allow-fs-write`",
"meta": {
"added": [
"v20.0.0"
],
"changes": [
{
"version": "v20.7.0",
"pr-url": "https://github.com/nodejs/node/pull/49047",
"description": "Paths delimited by comma (`,`) are no longer allowed."
}
]
},
"stability": 1,
"stabilityText": ".1 - Active development",
"desc": "This flag configures file system write permissions using\nthe Permission Model.
\nThe valid arguments for the --allow-fs-write
flag are:
*
- To allow all FileSystemWrite
operations.--allow-fs-read
flags.\nExample --allow-fs-read=/folder1/ --allow-fs-read=/folder1/
Paths delimited by comma (,
) are no longer allowed.\nWhen passing a single flag with a comma a warning will be displayed.
Examples can be found in the File System Permissions documentation.
\nRelative paths are NOT supported through the CLI flag.
", "type": "module", "displayName": "`--allow-fs-write`" }, { "textRaw": "`--allow-worker`", "name": "`--allow-worker`", "meta": { "added": [ "v20.0.0" ], "changes": [] }, "stability": 1, "stabilityText": ".1 - Active development", "desc": "When using the Permission Model, the process will not be able to create any\nworker threads by default.\nFor security reasons, the call will throw an ERR_ACCESS_DENIED
unless the\nuser explicitly pass the flag --allow-worker
in the main Node.js process.
Example:
\nconst { Worker } = require('node:worker_threads');\n// Attempt to bypass the permission\nnew Worker(__filename);\n
\n$ node --experimental-permission --allow-fs-read=* index.js\nnode:internal/worker:188\n this[kHandle] = new WorkerImpl(url,\n ^\n\nError: Access to this API has been restricted\n at new Worker (node:internal/worker:188:21)\n at Object.<anonymous> (/home/index.js.js:3:1)\n at Module._compile (node:internal/modules/cjs/loader:1120:14)\n at Module._extensions..js (node:internal/modules/cjs/loader:1174:10)\n at Module.load (node:internal/modules/cjs/loader:998:32)\n at Module._load (node:internal/modules/cjs/loader:839:12)\n at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)\n at node:internal/main/run_main_module:17:47 {\n code: 'ERR_ACCESS_DENIED',\n permission: 'WorkerThreads'\n}\n
",
"type": "module",
"displayName": "`--allow-worker`"
},
{
"textRaw": "`--build-snapshot`",
"name": "`--build-snapshot`",
"meta": {
"added": [
"v18.8.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Generates a snapshot blob when the process exits and writes it to\ndisk, which can be loaded later with --snapshot-blob
.
When building the snapshot, if --snapshot-blob
is not specified,\nthe generated blob will be written, by default, to snapshot.blob
\nin the current working directory. Otherwise it will be written to\nthe path specified by --snapshot-blob
.
$ echo \"globalThis.foo = 'I am from the snapshot'\" > snapshot.js\n\n# Run snapshot.js to initialize the application and snapshot the\n# state of it into snapshot.blob.\n$ node --snapshot-blob snapshot.blob --build-snapshot snapshot.js\n\n$ echo \"console.log(globalThis.foo)\" > index.js\n\n# Load the generated snapshot and start the application from index.js.\n$ node --snapshot-blob snapshot.blob index.js\nI am from the snapshot\n
\nThe v8.startupSnapshot
API can be used to specify an entry point at\nsnapshot building time, thus avoiding the need of an additional entry\nscript at deserialization time:
$ echo \"require('v8').startupSnapshot.setDeserializeMainFunction(() => console.log('I am from the snapshot'))\" > snapshot.js\n$ node --snapshot-blob snapshot.blob --build-snapshot snapshot.js\n$ node --snapshot-blob snapshot.blob\nI am from the snapshot\n
\nFor more information, check out the v8.startupSnapshot
API documentation.
Currently the support for run-time snapshot is experimental in that:
\nSpecifies the path to a JSON configuration file which configures snapshot\ncreation behavior.
\nThe following options are currently supported:
\nbuilder
<string> Required. Provides the name to the script that is executed\nbefore building the snapshot, as if --build-snapshot
had been passed\nwith builder
as the main script name.withoutCodeCache
<boolean> Optional. Including the code cache reduces the\ntime spent on compiling functions included in the snapshot at the expense\nof a bigger snapshot size and potentially breaking portability of the\nsnapshot.When using this flag, additional script files provided on the command line will\nnot be executed and instead be interpreted as regular command line arguments.
", "type": "module", "displayName": "`--build-snapshot-config`" }, { "textRaw": "`-c`, `--check`", "name": "`-c`,_`--check`", "meta": { "added": [ "v5.0.0", "v4.2.0" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/19600", "description": "The `--require` option is now supported when checking a file." } ] }, "desc": "Syntax check the script without executing.
", "type": "module", "displayName": "`-c`, `--check`" }, { "textRaw": "`--completion-bash`", "name": "`--completion-bash`", "meta": { "added": [ "v10.12.0" ], "changes": [] }, "desc": "Print source-able bash completion script for Node.js.
\nnode --completion-bash > node_bash_completion\nsource node_bash_completion\n
",
"type": "module",
"displayName": "`--completion-bash`"
},
{
"textRaw": "`-C condition`, `--conditions=condition`",
"name": "`-c_condition`,_`--conditions=condition`",
"meta": {
"added": [
"v14.9.0",
"v12.19.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Enable experimental support for custom conditional exports resolution\nconditions.
\nAny number of custom string condition names are permitted.
\nThe default Node.js conditions of \"node\"
, \"default\"
, \"import\"
, and\n\"require\"
will always apply as defined.
For example, to run a module with \"development\" resolutions:
\nnode -C development app.js\n
",
"type": "module",
"displayName": "`-C condition`, `--conditions=condition`"
},
{
"textRaw": "`--cpu-prof`",
"name": "`--cpu-prof`",
"meta": {
"added": [
"v12.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Starts the V8 CPU profiler on start up, and writes the CPU profile to disk\nbefore exit.
\nIf --cpu-prof-dir
is not specified, the generated profile is placed\nin the current working directory.
If --cpu-prof-name
is not specified, the generated profile is\nnamed CPU.${yyyymmdd}.${hhmmss}.${pid}.${tid}.${seq}.cpuprofile
.
$ node --cpu-prof index.js\n$ ls *.cpuprofile\nCPU.20190409.202950.15293.0.0.cpuprofile\n
",
"type": "module",
"displayName": "`--cpu-prof`"
},
{
"textRaw": "`--cpu-prof-dir`",
"name": "`--cpu-prof-dir`",
"meta": {
"added": [
"v12.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Specify the directory where the CPU profiles generated by --cpu-prof
will\nbe placed.
The default value is controlled by the\n--diagnostic-dir
command-line option.
Specify the sampling interval in microseconds for the CPU profiles generated\nby --cpu-prof
. The default is 1000 microseconds.
Specify the file name of the CPU profile generated by --cpu-prof
.
Set the directory to which all diagnostic output files are written.\nDefaults to current working directory.
\nAffects the default output directory of:
\n", "type": "module", "displayName": "`--diagnostic-dir=directory`" }, { "textRaw": "`--disable-warning=code-or-type`", "name": "`--disable-warning=code-or-type`", "stability": 1, "stabilityText": ".1 - Active development", "meta": { "added": [ "v21.3.0" ], "changes": [] }, "desc": "Disable specific process warnings by code
or type
.
Warnings emitted from process.emitWarning()
may contain a\ncode
and a type
. This option will not-emit warnings that have a matching\ncode
or type
.
List of deprecation warnings.
\nThe Node.js core warning types are: DeprecationWarning
and\nExperimentalWarning
For example, the following script will not emit\nDEP0025 require('node:sys')
when executed with\nnode --disable-warning=DEP0025
:
import sys from 'node:sys';\n
\nconst sys = require('node:sys');\n
\nFor example, the following script will emit the\nDEP0025 require('node:sys')
, but not any Experimental\nWarnings (such as\nExperimentalWarning: vm.measureMemory
is an experimental feature\nin <=v21) when executed with node --disable-warning=ExperimentalWarning
:
import sys from 'node:sys';\nimport vm from 'node:vm';\n\nvm.measureMemory();\n
\nconst sys = require('node:sys');\nconst vm = require('node:vm');\n\nvm.measureMemory();\n
",
"type": "module",
"displayName": "`--disable-warning=code-or-type`"
},
{
"textRaw": "`--disable-proto=mode`",
"name": "`--disable-proto=mode`",
"meta": {
"added": [
"v13.12.0",
"v12.17.0"
],
"changes": []
},
"desc": "Disable the Object.prototype.__proto__
property. If mode
is delete
, the\nproperty is removed entirely. If mode
is throw
, accesses to the\nproperty throw an exception with the code ERR_PROTO_ACCESS
.
Make built-in language features like eval
and new Function
that generate\ncode from strings throw an exception instead. This does not affect the Node.js\nnode:vm
module.
Set the default value of verbatim
in dns.lookup()
and\ndnsPromises.lookup()
. The value could be:
ipv4first
: sets default verbatim
false
.verbatim
: sets default verbatim
true
.The default is verbatim
and dns.setDefaultResultOrder()
have higher\npriority than --dns-result-order
.
Enable FIPS-compliant crypto at startup. (Requires Node.js to be built\nagainst FIPS-compatible OpenSSL.)
", "type": "module", "displayName": "`--enable-fips`" }, { "textRaw": "`--enable-network-family-autoselection`", "name": "`--enable-network-family-autoselection`", "meta": { "added": [ "v18.18.0" ], "changes": [] }, "desc": "Enables the family autoselection algorithm unless connection options explicitly\ndisables it.
", "type": "module", "displayName": "`--enable-network-family-autoselection`" }, { "textRaw": "`--enable-source-maps`", "name": "`--enable-source-maps`", "meta": { "added": [ "v12.12.0" ], "changes": [ { "version": [ "v15.11.0", "v14.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/37362", "description": "This API is no longer experimental." } ] }, "desc": "Enable Source Map v3 support for stack traces.
\nWhen using a transpiler, such as TypeScript, stack traces thrown by an\napplication reference the transpiled code, not the original source position.\n--enable-source-maps
enables caching of Source Maps and makes a best\neffort to report stack traces relative to the original source file.
Overriding Error.prepareStackTrace
may prevent --enable-source-maps
from\nmodifying the stack trace. Call and return the results of the original\nError.prepareStackTrace
in the overriding function to modify the stack trace\nwith source maps.
const originalPrepareStackTrace = Error.prepareStackTrace;\nError.prepareStackTrace = (error, trace) => {\n // Modify error and trace and format stack trace with\n // original Error.prepareStackTrace.\n return originalPrepareStackTrace(error, trace);\n};\n
\nNote, enabling source maps can introduce latency to your application\nwhen Error.stack
is accessed. If you access Error.stack
frequently\nin your application, take into account the performance implications\nof --enable-source-maps
.
Loads environment variables from a file relative to the current directory,\nmaking them available to applications on process.env
. The environment\nvariables which configure Node.js, such as NODE_OPTIONS
,\nare parsed and applied. If the same variable is defined in the environment and\nin the file, the value from the environment takes precedence.
You can pass multiple --env-file
arguments. Subsequent files override\npre-existing variables defined in previous files.
node --env-file=.env --env-file=.development.env index.js\n
\nThe format of the file should be one line per key-value pair of environment\nvariable name and value separated by =
:
PORT=3000\n
\nAny text after a #
is treated as a comment:
# This is a comment\nPORT=3000 # This is also a comment\n
\nValues can start and end with the following quotes: \\
, \"
or '
.\nThey are omitted from the values.
USERNAME=\"nodejs\" # will result in `nodejs` as the value.\n
\nMulti-line values are supported:
\nMULTI_LINE=\"THIS IS\nA MULTILINE\"\n# will result in `THIS IS\\nA MULTILINE` as the value.\n
\nExport keyword before a key is ignored:
\nexport USERNAME=\"nodejs\" # will result in `nodejs` as the value.\n
",
"type": "module",
"displayName": "`--env-file=config`"
},
{
"textRaw": "`-e`, `--eval \"script\"`",
"name": "`-e`,_`--eval_\"script\"`",
"meta": {
"added": [
"v0.5.2"
],
"changes": [
{
"version": "v5.11.0",
"pr-url": "https://github.com/nodejs/node/pull/5348",
"description": "Built-in libraries are now available as predefined variables."
}
]
},
"desc": "Evaluate the following argument as JavaScript. The modules which are\npredefined in the REPL can also be used in script
.
On Windows, using cmd.exe
a single quote will not work correctly because it\nonly recognizes double \"
for quoting. In Powershell or Git bash, both '
\nand \"
are usable.
Define which module system, module
or commonjs
, to use for the following:
String input provided via --eval
or STDIN, if --input-type
is unspecified.
Files ending in .js
or with no extension, if there is no package.json
file\npresent in the same folder or any parent folder.
Files ending in .js
or with no extension, if the nearest parent\npackage.json
field lacks a \"type\"
field; unless the package.json
folder\nor any parent folder is inside a node_modules
folder.
In other words, --experimental-default-type=module
flips all the places where\nNode.js currently defaults to CommonJS to instead default to ECMAScript modules,\nwith the exception of folders and subfolders below node_modules
, for backward\ncompatibility.
Under --experimental-default-type=module
and --experimental-wasm-modules
,\nfiles with no extension will be treated as WebAssembly if they begin with the\nWebAssembly magic number (\\0asm
); otherwise they will be treated as ES module\nJavaScript.
Node.js will inspect the source code of ambiguous input to determine whether it\ncontains ES module syntax; if such syntax is detected, the input will be treated\nas an ES module.
\nAmbiguous input is defined as:
\n.js
extension or no extension; and either no controlling\npackage.json
file or one that lacks a type
field; and\n--experimental-default-type
is not specified.--eval
or STDIN) when neither --input-type
nor\n--experimental-default-type
are specified.ES module syntax is defined as syntax that would throw when evaluated as\nCommonJS. This includes import
and export
statements and import.meta
\nreferences. It does not include import()
expressions, which are valid in\nCommonJS.
Enable experimental import.meta.resolve()
parent URL support, which allows\npassing a second parentURL
argument for contextual resolution.
Previously gated the entire import.meta.resolve
feature.
\n\nThis flag is discouraged and may be removed in a future version of Node.js.\nPlease use\n
\n--import
withregister()
instead.
Specify the module
containing exported module customization hooks.\nmodule
may be any string accepted as an import
specifier.
Enable experimental support for the https:
protocol in import
specifiers.
Enable the Permission Model for current process. When enabled, the\nfollowing permissions are restricted:
\n--allow-fs-read
, --allow-fs-write
flags--allow-child-process
flag--allow-worker
flagUse the specified file as a security policy.
", "type": "module", "displayName": "`--experimental-policy`" }, { "textRaw": "`--experimental-sea-config`", "name": "`--experimental-sea-config`", "meta": { "added": [ "v20.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "desc": "Use this flag to generate a blob that can be injected into the Node.js\nbinary to produce a single executable application. See the documentation\nabout this configuration for details.
", "type": "module", "displayName": "`--experimental-sea-config`" }, { "textRaw": "`--experimental-shadow-realm`", "name": "`--experimental-shadow-realm`", "meta": { "added": [ "v19.0.0", "v18.13.0" ], "changes": [] }, "desc": "Use this flag to enable ShadowRealm support.
", "type": "module", "displayName": "`--experimental-shadow-realm`" }, { "textRaw": "`--experimental-test-coverage`", "name": "`--experimental-test-coverage`", "meta": { "added": [ "v19.7.0", "v18.15.0" ], "changes": [ { "version": [ "v20.1.0", "v18.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/47686", "description": "This option can be used with `--test`." } ] }, "desc": "When used in conjunction with the node:test
module, a code coverage report is\ngenerated as part of the test runner output. If no tests are run, a coverage\nreport is not generated. See the documentation on\ncollecting code coverage from tests for more details.
Enable experimental ES Module support in the node:vm
module.
Enable experimental WebAssembly System Interface (WASI) support.
", "type": "module", "displayName": "`--experimental-wasi-unstable-preview1`" }, { "textRaw": "`--experimental-wasm-modules`", "name": "`--experimental-wasm-modules`", "meta": { "added": [ "v12.3.0" ], "changes": [] }, "desc": "Enable experimental WebAssembly module support.
", "type": "module", "displayName": "`--experimental-wasm-modules`" }, { "textRaw": "`--experimental-websocket`", "name": "`--experimental-websocket`", "meta": { "added": [ "v21.0.0" ], "changes": [] }, "desc": "Enable experimental WebSocket
support.
Disable loading native addons that are not context-aware.
", "type": "module", "displayName": "`--force-context-aware`" }, { "textRaw": "`--force-fips`", "name": "`--force-fips`", "meta": { "added": [ "v6.0.0" ], "changes": [] }, "desc": "Force FIPS-compliant crypto on startup. (Cannot be disabled from script code.)\n(Same requirements as --enable-fips
.)
Enforces uncaughtException
event on Node-API asynchronous callbacks.
To prevent from an existing add-on from crashing the process, this flag is not\nenabled by default. In the future, this flag will be enabled by default to\nenforce the correct behavior.
", "type": "module", "displayName": "`--force-node-api-uncaught-exceptions-policy`" }, { "textRaw": "`--frozen-intrinsics`", "name": "`--frozen-intrinsics`", "meta": { "added": [ "v11.12.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "desc": "Enable experimental frozen intrinsics like Array
and Object
.
Only the root context is supported. There is no guarantee that\nglobalThis.Array
is indeed the default intrinsic reference. Code may break\nunder this flag.
To allow polyfills to be added,\n--require
and --import
both run before freezing intrinsics.
Starts the V8 heap profiler on start up, and writes the heap profile to disk\nbefore exit.
\nIf --heap-prof-dir
is not specified, the generated profile is placed\nin the current working directory.
If --heap-prof-name
is not specified, the generated profile is\nnamed Heap.${yyyymmdd}.${hhmmss}.${pid}.${tid}.${seq}.heapprofile
.
$ node --heap-prof index.js\n$ ls *.heapprofile\nHeap.20190409.202950.15293.0.001.heapprofile\n
",
"type": "module",
"displayName": "`--heap-prof`"
},
{
"textRaw": "`--heap-prof-dir`",
"name": "`--heap-prof-dir`",
"meta": {
"added": [
"v12.4.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Specify the directory where the heap profiles generated by --heap-prof
will\nbe placed.
The default value is controlled by the\n--diagnostic-dir
command-line option.
Specify the average sampling interval in bytes for the heap profiles generated\nby --heap-prof
. The default is 512 * 1024 bytes.
Specify the file name of the heap profile generated by --heap-prof
.
Writes a V8 heap snapshot to disk when the V8 heap usage is approaching the\nheap limit. count
should be a non-negative integer (in which case\nNode.js will write no more than max_count
snapshots to disk).
When generating snapshots, garbage collection may be triggered and bring\nthe heap usage down. Therefore multiple snapshots may be written to disk\nbefore the Node.js instance finally runs out of memory. These heap snapshots\ncan be compared to determine what objects are being allocated during the\ntime consecutive snapshots are taken. It's not guaranteed that Node.js will\nwrite exactly max_count
snapshots to disk, but it will try\nits best to generate at least one and up to max_count
snapshots before the\nNode.js instance runs out of memory when max_count
is greater than 0
.
Generating V8 snapshots takes time and memory (both memory managed by the\nV8 heap and native memory outside the V8 heap). The bigger the heap is,\nthe more resources it needs. Node.js will adjust the V8 heap to accommodate\nthe additional V8 heap memory overhead, and try its best to avoid using up\nall the memory available to the process. When the process uses\nmore memory than the system deems appropriate, the process may be terminated\nabruptly by the system, depending on the system configuration.
\n$ node --max-old-space-size=100 --heapsnapshot-near-heap-limit=3 index.js\nWrote snapshot to Heap.20200430.100036.49580.0.001.heapsnapshot\nWrote snapshot to Heap.20200430.100037.49580.0.002.heapsnapshot\nWrote snapshot to Heap.20200430.100038.49580.0.003.heapsnapshot\n\n<--- Last few GCs --->\n\n[49580:0x110000000] 4826 ms: Mark-sweep 130.6 (147.8) -> 130.5 (147.8) MB, 27.4 / 0.0 ms (average mu = 0.126, current mu = 0.034) allocation failure scavenge might not succeed\n[49580:0x110000000] 4845 ms: Mark-sweep 130.6 (147.8) -> 130.6 (147.8) MB, 18.8 / 0.0 ms (average mu = 0.088, current mu = 0.031) allocation failure scavenge might not succeed\n\n\n<--- JS stacktrace --->\n\nFATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory\n....\n
",
"type": "module",
"displayName": "`--heapsnapshot-near-heap-limit=max_count`"
},
{
"textRaw": "`--heapsnapshot-signal=signal`",
"name": "`--heapsnapshot-signal=signal`",
"meta": {
"added": [
"v12.0.0"
],
"changes": []
},
"desc": "Enables a signal handler that causes the Node.js process to write a heap dump\nwhen the specified signal is received. signal
must be a valid signal name.\nDisabled by default.
$ node --heapsnapshot-signal=SIGUSR2 index.js &\n$ ps aux\nUSER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND\nnode 1 5.5 6.1 787252 247004 ? Ssl 16:43 0:02 node --heapsnapshot-signal=SIGUSR2 index.js\n$ kill -USR2 1\n$ ls\nHeap.20190718.133405.15554.0.001.heapsnapshot\n
",
"type": "module",
"displayName": "`--heapsnapshot-signal=signal`"
},
{
"textRaw": "`-h`, `--help`",
"name": "`-h`,_`--help`",
"meta": {
"added": [
"v0.1.3"
],
"changes": []
},
"desc": "Print node command-line options.\nThe output of this option is less detailed than this document.
", "type": "module", "displayName": "`-h`, `--help`" }, { "textRaw": "`--icu-data-dir=file`", "name": "`--icu-data-dir=file`", "meta": { "added": [ "v0.11.15" ], "changes": [] }, "desc": "Specify ICU data load path. (Overrides NODE_ICU_DATA
.)
Preload the specified module at startup. If the flag is provided several times,\neach module will be executed sequentially in the order they appear, starting\nwith the ones provided in NODE_OPTIONS
.
Follows ECMAScript module resolution rules.\nUse --require
to load a CommonJS module.\nModules preloaded with --require
will run before modules preloaded with --import
.
This configures Node.js to interpret --eval
or STDIN
input as CommonJS or\nas an ES module. Valid values are \"commonjs\"
or \"module\"
. The default is\n\"commonjs\"
unless --experimental-default-type=module
is used.
The REPL does not support this option. Usage of --input-type=module
with\n--print
will throw an error, as --print
does not support ES module\nsyntax.
Enable leniency flags on the HTTP parser. This may allow\ninteroperability with non-conformant HTTP implementations.
\nWhen enabled, the parser will accept the following:
\nTransfer-Encoding
\nand Content-Length
headers.Connection: close
is present.chunked
has been provided.\\n
to be used as token separator instead of \\r\\n
.\\r\\n
not to be provided after a chunk.\\r\\n
.All the above will expose your application to request smuggling\nor poisoning attack. Avoid using this option.
", "type": "module", "displayName": "`--insecure-http-parser`" }, { "textRaw": "`--inspect[=[host:]port]`", "name": "`--inspect[=[host:]port]`", "meta": { "added": [ "v6.3.0" ], "changes": [] }, "desc": "Activate inspector on host:port
. Default is 127.0.0.1:9229
.
V8 inspector integration allows tools such as Chrome DevTools and IDEs to debug\nand profile Node.js instances. The tools attach to Node.js instances via a\ntcp port and communicate using the Chrome DevTools Protocol.
\n\n", "modules": [ { "textRaw": "Warning: binding inspector to a public IP:port combination is insecure", "name": "warning:_binding_inspector_to_a_public_ip:port_combination_is_insecure", "desc": "Binding the inspector to a public IP (including 0.0.0.0
) with an open port is\ninsecure, as it allows external hosts to connect to the inspector and perform\na remote code execution attack.
If specifying a host, make sure that either:
\nMore specifically, --inspect=0.0.0.0
is insecure if the port (9229
by\ndefault) is not firewall-protected.
See the debugging security implications section for more information.
", "type": "module", "displayName": "Warning: binding inspector to a public IP:port combination is insecure" } ], "type": "module", "displayName": "`--inspect[=[host:]port]`" }, { "textRaw": "`--inspect-brk[=[host:]port]`", "name": "`--inspect-brk[=[host:]port]`", "meta": { "added": [ "v7.6.0" ], "changes": [] }, "desc": "Activate inspector on host:port
and break at start of user script.\nDefault host:port
is 127.0.0.1:9229
.
Set the host:port
to be used when the inspector is activated.\nUseful when activating the inspector by sending the SIGUSR1
signal.
Default host is 127.0.0.1
.
See the security warning below regarding the host
\nparameter usage.
Specify ways of the inspector web socket url exposure.
\nBy default inspector websocket url is available in stderr and under /json/list
\nendpoint on http://host:port/json/list
.
Opens the REPL even if stdin does not appear to be a terminal.
", "type": "module", "displayName": "`-i`, `--interactive`" }, { "textRaw": "`--jitless`", "name": "`--jitless`", "meta": { "added": [ "v12.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental. This flag is inherited from V8 and is subject to change upstream.", "desc": "Disable runtime allocation of executable memory. This may be\nrequired on some platforms for security reasons. It can also reduce attack\nsurface on other platforms, but the performance impact may be severe.
", "type": "module", "displayName": "`--jitless`" }, { "textRaw": "`--max-http-header-size=size`", "name": "`--max-http-header-size=size`", "meta": { "added": [ "v11.6.0", "v10.15.0" ], "changes": [ { "version": "v13.13.0", "pr-url": "https://github.com/nodejs/node/pull/32520", "description": "Change maximum default size of HTTP headers from 8 KiB to 16 KiB." } ] }, "desc": "Specify the maximum size, in bytes, of HTTP headers. Defaults to 16 KiB.
", "type": "module", "displayName": "`--max-http-header-size=size`" }, { "textRaw": "`--napi-modules`", "name": "`--napi-modules`", "meta": { "added": [ "v7.10.0" ], "changes": [] }, "desc": "This option is a no-op. It is kept for compatibility.
", "type": "module", "displayName": "`--napi-modules`" }, { "textRaw": "`--no-addons`", "name": "`--no-addons`", "meta": { "added": [ "v16.10.0", "v14.19.0" ], "changes": [] }, "desc": "Disable the node-addons
exports condition as well as disable loading\nnative addons. When --no-addons
is specified, calling process.dlopen
or\nrequiring a native C++ addon will fail and throw an exception.
Silence deprecation warnings.
", "type": "module", "displayName": "`--no-deprecation`" }, { "textRaw": "`--no-experimental-fetch`", "name": "`--no-experimental-fetch`", "meta": { "added": [ "v18.0.0" ], "changes": [] }, "desc": "Disable exposition of Fetch API on the global scope.
", "type": "module", "displayName": "`--no-experimental-fetch`" }, { "textRaw": "`--no-experimental-global-customevent`", "name": "`--no-experimental-global-customevent`", "meta": { "added": [ "v19.0.0" ], "changes": [] }, "desc": "Disable exposition of CustomEvent Web API on the global scope.
", "type": "module", "displayName": "`--no-experimental-global-customevent`" }, { "textRaw": "`--no-experimental-global-navigator`", "name": "`--no-experimental-global-navigator`", "meta": { "added": [ "v21.2.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "desc": "Disable exposition of Navigator API on the global scope.
", "type": "module", "displayName": "`--no-experimental-global-navigator`" }, { "textRaw": "`--no-experimental-global-webcrypto`", "name": "`--no-experimental-global-webcrypto`", "meta": { "added": [ "v19.0.0" ], "changes": [] }, "desc": "Disable exposition of Web Crypto API on the global scope.
", "type": "module", "displayName": "`--no-experimental-global-webcrypto`" }, { "textRaw": "`--no-experimental-repl-await`", "name": "`--no-experimental-repl-await`", "meta": { "added": [ "v16.6.0" ], "changes": [] }, "desc": "Use this flag to disable top-level await in REPL.
", "type": "module", "displayName": "`--no-experimental-repl-await`" }, { "textRaw": "`--no-extra-info-on-fatal-exception`", "name": "`--no-extra-info-on-fatal-exception`", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "desc": "Hide extra information on fatal exception that causes exit.
", "type": "module", "displayName": "`--no-extra-info-on-fatal-exception`" }, { "textRaw": "`--no-force-async-hooks-checks`", "name": "`--no-force-async-hooks-checks`", "meta": { "added": [ "v9.0.0" ], "changes": [] }, "desc": "Disables runtime checks for async_hooks
. These will still be enabled\ndynamically when async_hooks
is enabled.
Do not search modules from global paths like $HOME/.node_modules
and\n$NODE_PATH
.
Disables the family autoselection algorithm unless connection options explicitly\nenables it.
", "type": "module", "displayName": "`--no-network-family-autoselection`" }, { "textRaw": "`--no-warnings`", "name": "`--no-warnings`", "meta": { "added": [ "v6.0.0" ], "changes": [] }, "desc": "Silence all process warnings (including deprecations).
", "type": "module", "displayName": "`--no-warnings`" }, { "textRaw": "`--node-memory-debug`", "name": "`--node-memory-debug`", "meta": { "added": [ "v15.0.0", "v14.18.0" ], "changes": [] }, "desc": "Enable extra debug checks for memory leaks in Node.js internals. This is\nusually only useful for developers debugging Node.js itself.
", "type": "module", "displayName": "`--node-memory-debug`" }, { "textRaw": "`--openssl-config=file`", "name": "`--openssl-config=file`", "meta": { "added": [ "v6.9.0" ], "changes": [] }, "desc": "Load an OpenSSL configuration file on startup. Among other uses, this can be\nused to enable FIPS-compliant crypto if Node.js is built\nagainst FIPS-enabled OpenSSL.
", "type": "module", "displayName": "`--openssl-config=file`" }, { "textRaw": "`--openssl-legacy-provider`", "name": "`--openssl-legacy-provider`", "meta": { "added": [ "v17.0.0", "v16.17.0" ], "changes": [] }, "desc": "Enable OpenSSL 3.0 legacy provider. For more information please see\nOSSL_PROVIDER-legacy.
", "type": "module", "displayName": "`--openssl-legacy-provider`" }, { "textRaw": "`--openssl-shared-config`", "name": "`--openssl-shared-config`", "meta": { "added": [ "v18.5.0", "v16.17.0", "v14.21.0" ], "changes": [] }, "desc": "Enable OpenSSL default configuration section, openssl_conf
to be read from\nthe OpenSSL configuration file. The default configuration file is named\nopenssl.cnf
but this can be changed using the environment variable\nOPENSSL_CONF
, or by using the command line option --openssl-config
.\nThe location of the default OpenSSL configuration file depends on how OpenSSL\nis being linked to Node.js. Sharing the OpenSSL configuration may have unwanted\nimplications and it is recommended to use a configuration section specific to\nNode.js which is nodejs_conf
and is default when this option is not used.
Emit pending deprecation warnings.
\nPending deprecations are generally identical to a runtime deprecation with the\nnotable exception that they are turned off by default and will not be emitted\nunless either the --pending-deprecation
command-line flag, or the\nNODE_PENDING_DEPRECATION=1
environment variable, is set. Pending deprecations\nare used to provide a kind of selective \"early warning\" mechanism that\ndevelopers may leverage to detect deprecated API usage.
Instructs Node.js to error prior to running any code if the policy does not have\nthe specified integrity. It expects a Subresource Integrity string as a\nparameter.
", "type": "module", "displayName": "`--policy-integrity=sri`" }, { "textRaw": "`--preserve-symlinks`", "name": "`--preserve-symlinks`", "meta": { "added": [ "v6.3.0" ], "changes": [] }, "desc": "Instructs the module loader to preserve symbolic links when resolving and\ncaching modules.
\nBy default, when Node.js loads a module from a path that is symbolically linked\nto a different on-disk location, Node.js will dereference the link and use the\nactual on-disk \"real path\" of the module as both an identifier and as a root\npath to locate other dependency modules. In most cases, this default behavior\nis acceptable. However, when using symbolically linked peer dependencies, as\nillustrated in the example below, the default behavior causes an exception to\nbe thrown if moduleA
attempts to require moduleB
as a peer dependency:
{appDir}\n ├── app\n │ ├── index.js\n │ └── node_modules\n │ ├── moduleA -> {appDir}/moduleA\n │ └── moduleB\n │ ├── index.js\n │ └── package.json\n └── moduleA\n ├── index.js\n └── package.json\n
\nThe --preserve-symlinks
command-line flag instructs Node.js to use the\nsymlink path for modules as opposed to the real path, allowing symbolically\nlinked peer dependencies to be found.
Note, however, that using --preserve-symlinks
can have other side effects.\nSpecifically, symbolically linked native modules can fail to load if those\nare linked from more than one location in the dependency tree (Node.js would\nsee those as two separate modules and would attempt to load the module multiple\ntimes, causing an exception to be thrown).
The --preserve-symlinks
flag does not apply to the main module, which allows\nnode --preserve-symlinks node_module/.bin/<foo>
to work. To apply the same\nbehavior for the main module, also use --preserve-symlinks-main
.
Instructs the module loader to preserve symbolic links when resolving and\ncaching the main module (require.main
).
This flag exists so that the main module can be opted-in to the same behavior\nthat --preserve-symlinks
gives to all other imports; they are separate flags,\nhowever, for backward compatibility with older Node.js versions.
--preserve-symlinks-main
does not imply --preserve-symlinks
; use\n--preserve-symlinks-main
in addition to\n--preserve-symlinks
when it is not desirable to follow symlinks before\nresolving relative paths.
See --preserve-symlinks
for more information.
Identical to -e
but prints the result.
Generate V8 profiler output.
", "type": "module", "displayName": "`--prof`" }, { "textRaw": "`--prof-process`", "name": "`--prof-process`", "meta": { "added": [ "v5.2.0" ], "changes": [] }, "desc": "Process V8 profiler output generated using the V8 option --prof
.
Write process warnings to the given file instead of printing to stderr. The\nfile will be created if it does not exist, and will be appended to if it does.\nIf an error occurs while attempting to write the warning to the file, the\nwarning will be written to stderr instead.
\nThe file
name may be an absolute path. If it is not, the default directory it\nwill be written to is controlled by the\n--diagnostic-dir
command-line option.
Write reports in a compact format, single-line JSON, more easily consumable\nby log processing systems than the default multi-line format designed for\nhuman consumption.
", "type": "module", "displayName": "`--report-compact`" }, { "textRaw": "`--report-dir=directory`, `report-directory=directory`", "name": "`--report-dir=directory`,_`report-directory=directory`", "meta": { "added": [ "v11.8.0" ], "changes": [ { "version": [ "v13.12.0", "v12.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/32242", "description": "This option is no longer experimental." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/27312", "description": "Changed from `--diagnostic-report-directory` to `--report-directory`." } ] }, "desc": "Location at which the report will be generated.
", "type": "module", "displayName": "`--report-dir=directory`, `report-directory=directory`" }, { "textRaw": "`--report-filename=filename`", "name": "`--report-filename=filename`", "meta": { "added": [ "v11.8.0" ], "changes": [ { "version": [ "v13.12.0", "v12.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/32242", "description": "This option is no longer experimental." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/27312", "description": "changed from `--diagnostic-report-filename` to `--report-filename`." } ] }, "desc": "Name of the file to which the report will be written.
\nIf the filename is set to 'stdout'
or 'stderr'
, the report is written to\nthe stdout or stderr of the process respectively.
Enables the report to be triggered on fatal errors (internal errors within\nthe Node.js runtime such as out of memory) that lead to termination of the\napplication. Useful to inspect various diagnostic data elements such as heap,\nstack, event loop state, resource consumption etc. to reason about the fatal\nerror.
", "type": "module", "displayName": "`--report-on-fatalerror`" }, { "textRaw": "`--report-on-signal`", "name": "`--report-on-signal`", "meta": { "added": [ "v11.8.0" ], "changes": [ { "version": [ "v13.12.0", "v12.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/32242", "description": "This option is no longer experimental." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/27312", "description": "changed from `--diagnostic-report-on-signal` to `--report-on-signal`." } ] }, "desc": "Enables report to be generated upon receiving the specified (or predefined)\nsignal to the running Node.js process. The signal to trigger the report is\nspecified through --report-signal
.
Sets or resets the signal for report generation (not supported on Windows).\nDefault signal is SIGUSR2
.
Enables report to be generated when the process exits due to an uncaught\nexception. Useful when inspecting the JavaScript stack in conjunction with\nnative stack and other runtime environment data.
", "type": "module", "displayName": "`--report-uncaught-exception`" }, { "textRaw": "`-r`, `--require module`", "name": "`-r`,_`--require_module`", "meta": { "added": [ "v1.6.0" ], "changes": [] }, "desc": "Preload the specified module at startup.
\nFollows require()
's module resolution\nrules. module
may be either a path to a file, or a node module name.
Only CommonJS modules are supported.\nUse --import
to preload an ECMAScript module.\nModules preloaded with --require
will run before modules preloaded with --import
.
Initializes an OpenSSL secure heap of n
bytes. When initialized, the\nsecure heap is used for selected types of allocations within OpenSSL\nduring key generation and other operations. This is useful, for instance,\nto prevent sensitive information from leaking due to pointer overruns\nor underruns.
The secure heap is a fixed size and cannot be resized at runtime so,\nif used, it is important to select a large enough heap to cover all\napplication uses.
\nThe heap size given must be a power of two. Any value less than 2\nwill disable the secure heap.
\nThe secure heap is disabled by default.
\nThe secure heap is not available on Windows.
\nSee CRYPTO_secure_malloc_init
for more details.
When using --secure-heap
, the --secure-heap-min
flag specifies the\nminimum allocation from the secure heap. The minimum value is 2
.\nThe maximum value is the lesser of --secure-heap
or 2147483647
.\nThe value given must be a power of two.
When used with --build-snapshot
, --snapshot-blob
specifies the path\nwhere the generated snapshot blob is written to. If not specified, the\ngenerated blob is written to snapshot.blob
in the current working directory.
When used without --build-snapshot
, --snapshot-blob
specifies the\npath to the blob that is used to restore the application state.
When loading a snapshot, Node.js checks that:
\nIf they don't match, Node.js refuses to load the snapshot and exits with\nstatus code 1.
", "type": "module", "displayName": "`--snapshot-blob=path`" }, { "textRaw": "`--test`", "name": "`--test`", "meta": { "added": [ "v18.1.0", "v16.17.0" ], "changes": [ { "version": "v20.0.0", "pr-url": "https://github.com/nodejs/node/pull/46983", "description": "The test runner is now stable." }, { "version": [ "v19.2.0", "v18.13.0" ], "pr-url": "https://github.com/nodejs/node/pull/45214", "description": "Test runner now supports running in watch mode." } ] }, "desc": "Starts the Node.js command line test runner. This flag cannot be combined with\n--watch-path
, --check
, --eval
, --interactive
, or the inspector.\nSee the documentation on running tests from the command line\nfor more details.
The maximum number of test files that the test runner CLI will execute\nconcurrently. The default value is os.availableParallelism() - 1
.
A regular expression that configures the test runner to only execute tests\nwhose name matches the provided pattern. See the documentation on\nfiltering tests by name for more details.
", "type": "module", "displayName": "`--test-name-pattern`" }, { "textRaw": "`--test-only`", "name": "`--test-only`", "meta": { "added": [ "v18.0.0", "v16.17.0" ], "changes": [ { "version": "v20.0.0", "pr-url": "https://github.com/nodejs/node/pull/46983", "description": "The test runner is now stable." } ] }, "desc": "Configures the test runner to only execute top level tests that have the only
\noption set.
A test reporter to use when running tests. See the documentation on\ntest reporters for more details.
", "type": "module", "displayName": "`--test-reporter`" }, { "textRaw": "`--test-reporter-destination`", "name": "`--test-reporter-destination`", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [ { "version": "v20.0.0", "pr-url": "https://github.com/nodejs/node/pull/46983", "description": "The test runner is now stable." } ] }, "desc": "The destination for the corresponding test reporter. See the documentation on\ntest reporters for more details.
", "type": "module", "displayName": "`--test-reporter-destination`" }, { "textRaw": "`--test-shard`", "name": "`--test-shard`", "meta": { "added": [ "v20.5.0" ], "changes": [] }, "desc": "Test suite shard to execute in a format of <index>/<total>
, where
index
is a positive integer, index of divided parts\ntotal
is a positive integer, total of divided part\nThis command will divide all tests files into total
equal parts,\nand will run only those that happen to be in an index
part.
For example, to split your tests suite into three parts, use this:
\nnode --test --test-shard=1/3\nnode --test --test-shard=2/3\nnode --test --test-shard=3/3\n
",
"type": "module",
"displayName": "`--test-shard`"
},
{
"textRaw": "`--test-timeout`",
"name": "`--test-timeout`",
"meta": {
"added": [
"v21.2.0"
],
"changes": []
},
"desc": "A number of milliseconds the test execution will fail after. If unspecified,\nsubtests inherit this value from their parent. The default value is Infinity
.
Throw errors for deprecations.
", "type": "module", "displayName": "`--throw-deprecation`" }, { "textRaw": "`--title=title`", "name": "`--title=title`", "meta": { "added": [ "v10.7.0" ], "changes": [] }, "desc": "Set process.title
on startup.
Specify an alternative default TLS cipher list. Requires Node.js to be built\nwith crypto support (default).
", "type": "module", "displayName": "`--tls-cipher-list=list`" }, { "textRaw": "`--tls-keylog=file`", "name": "`--tls-keylog=file`", "meta": { "added": [ "v13.2.0", "v12.16.0" ], "changes": [] }, "desc": "Log TLS key material to a file. The key material is in NSS SSLKEYLOGFILE
\nformat and can be used by software (such as Wireshark) to decrypt the TLS\ntraffic.
Set tls.DEFAULT_MAX_VERSION
to 'TLSv1.2'. Use to disable support for\nTLSv1.3.
Set default tls.DEFAULT_MAX_VERSION
to 'TLSv1.3'. Use to enable support\nfor TLSv1.3.
Set default tls.DEFAULT_MIN_VERSION
to 'TLSv1'. Use for compatibility with\nold TLS clients or servers.
Set default tls.DEFAULT_MIN_VERSION
to 'TLSv1.1'. Use for compatibility\nwith old TLS clients or servers.
Set default tls.DEFAULT_MIN_VERSION
to 'TLSv1.2'. This is the default for\n12.x and later, but the option is supported for compatibility with older Node.js\nversions.
Set default tls.DEFAULT_MIN_VERSION
to 'TLSv1.3'. Use to disable support\nfor TLSv1.2, which is not as secure as TLSv1.3.
Print short summaries of calls to Atomics.wait()
to stderr.\nThe output could look like this:
(node:15701) [Thread 0] Atomics.wait(<address> + 0, 1, inf) started\n(node:15701) [Thread 0] Atomics.wait(<address> + 0, 1, inf) did not wait because the values mismatched\n(node:15701) [Thread 0] Atomics.wait(<address> + 0, 0, 10) started\n(node:15701) [Thread 0] Atomics.wait(<address> + 0, 0, 10) timed out\n(node:15701) [Thread 0] Atomics.wait(<address> + 4, 0, inf) started\n(node:15701) [Thread 1] Atomics.wait(<address> + 4, -1, inf) started\n(node:15701) [Thread 0] Atomics.wait(<address> + 4, 0, inf) was woken up by another thread\n(node:15701) [Thread 1] Atomics.wait(<address> + 4, -1, inf) was woken up by another thread\n
\nThe fields here correspond to:
\nworker_threads.threadId
SharedArrayBuffer
in question, as well as the\nbyte offset corresponding to the index passed to Atomics.wait()
Atomics.wait()
Atomics.wait
Print stack traces for deprecations.
", "type": "module", "displayName": "`--trace-deprecation`" }, { "textRaw": "`--trace-event-categories`", "name": "`--trace-event-categories`", "meta": { "added": [ "v7.7.0" ], "changes": [] }, "desc": "A comma separated list of categories that should be traced when trace event\ntracing is enabled using --trace-events-enabled
.
Template string specifying the filepath for the trace event data, it\nsupports ${rotation}
and ${pid}
.
Enables the collection of trace event tracing information.
", "type": "module", "displayName": "`--trace-events-enabled`" }, { "textRaw": "`--trace-exit`", "name": "`--trace-exit`", "meta": { "added": [ "v13.5.0", "v12.16.0" ], "changes": [] }, "desc": "Prints a stack trace whenever an environment is exited proactively,\ni.e. invoking process.exit()
.
Prints a stack trace on SIGINT.
", "type": "module", "displayName": "`--trace-sigint`" }, { "textRaw": "`--trace-sync-io`", "name": "`--trace-sync-io`", "meta": { "added": [ "v2.1.0" ], "changes": [] }, "desc": "Prints a stack trace whenever synchronous I/O is detected after the first turn\nof the event loop.
", "type": "module", "displayName": "`--trace-sync-io`" }, { "textRaw": "`--trace-tls`", "name": "`--trace-tls`", "meta": { "added": [ "v12.2.0" ], "changes": [] }, "desc": "Prints TLS packet trace information to stderr
. This can be used to debug TLS\nconnection problems.
Print stack traces for uncaught exceptions; usually, the stack trace associated\nwith the creation of an Error
is printed, whereas this makes Node.js also\nprint the stack trace associated with throwing the value (which does not need\nto be an Error
instance).
Enabling this option may affect garbage collection behavior negatively.
", "type": "module", "displayName": "`--trace-uncaught`" }, { "textRaw": "`--trace-warnings`", "name": "`--trace-warnings`", "meta": { "added": [ "v6.0.0" ], "changes": [] }, "desc": "Print stack traces for process warnings (including deprecations).
", "type": "module", "displayName": "`--trace-warnings`" }, { "textRaw": "`--track-heap-objects`", "name": "`--track-heap-objects`", "meta": { "added": [ "v2.4.0" ], "changes": [] }, "desc": "Track heap object allocations for heap snapshots.
", "type": "module", "displayName": "`--track-heap-objects`" }, { "textRaw": "`--unhandled-rejections=mode`", "name": "`--unhandled-rejections=mode`", "meta": { "added": [ "v12.0.0", "v10.17.0" ], "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/33021", "description": "Changed default mode to `throw`. Previously, a warning was emitted." } ] }, "desc": "Using this flag allows to change what should happen when an unhandled rejection\noccurs. One of the following modes can be chosen:
\nthrow
: Emit unhandledRejection
. If this hook is not set, raise the\nunhandled rejection as an uncaught exception. This is the default.strict
: Raise the unhandled rejection as an uncaught exception. If the\nexception is handled, unhandledRejection
is emitted.warn
: Always trigger a warning, no matter if the unhandledRejection
\nhook is set or not but do not print the deprecation warning.warn-with-error-code
: Emit unhandledRejection
. If this hook is not\nset, trigger a warning, and set the process exit code to 1.none
: Silence all warnings.If a rejection happens during the command line entry point's ES module static\nloading phase, it will always raise it as an uncaught exception.
", "type": "module", "displayName": "`--unhandled-rejections=mode`" }, { "textRaw": "`--use-bundled-ca`, `--use-openssl-ca`", "name": "`--use-bundled-ca`,_`--use-openssl-ca`", "meta": { "added": [ "v6.11.0" ], "changes": [] }, "desc": "Use bundled Mozilla CA store as supplied by current Node.js version\nor use OpenSSL's default CA store. The default store is selectable\nat build-time.
\nThe bundled CA store, as supplied by Node.js, is a snapshot of Mozilla CA store\nthat is fixed at release time. It is identical on all supported platforms.
\nUsing OpenSSL store allows for external modifications of the store. For most\nLinux and BSD distributions, this store is maintained by the distribution\nmaintainers and system administrators. OpenSSL CA store location is dependent on\nconfiguration of the OpenSSL library but this can be altered at runtime using\nenvironment variables.
\nSee SSL_CERT_DIR
and SSL_CERT_FILE
.
Re-map the Node.js static code to large memory pages at startup. If supported on\nthe target system, this will cause the Node.js static code to be moved onto 2\nMiB pages instead of 4 KiB pages.
\nThe following values are valid for mode
:
off
: No mapping will be attempted. This is the default.on
: If supported by the OS, mapping will be attempted. Failure to map will\nbe ignored and a message will be printed to standard error.silent
: If supported by the OS, mapping will be attempted. Failure to map\nwill be ignored and will not be reported.Print V8 command-line options.
", "type": "module", "displayName": "`--v8-options`" }, { "textRaw": "`--v8-pool-size=num`", "name": "`--v8-pool-size=num`", "meta": { "added": [ "v5.10.0" ], "changes": [] }, "desc": "Set V8's thread pool size which will be used to allocate background jobs.
\nIf set to 0
then Node.js will choose an appropriate size of the thread pool\nbased on an estimate of the amount of parallelism.
The amount of parallelism refers to the number of computations that can be\ncarried out simultaneously in a given machine. In general, it's the same as the\namount of CPUs, but it may diverge in environments such as VMs or containers.
", "type": "module", "displayName": "`--v8-pool-size=num`" }, { "textRaw": "`-v`, `--version`", "name": "`-v`,_`--version`", "meta": { "added": [ "v0.1.3" ], "changes": [] }, "desc": "Print node's version.
", "type": "module", "displayName": "`-v`, `--version`" }, { "textRaw": "`--watch`", "name": "`--watch`", "meta": { "added": [ "v18.11.0", "v16.19.0" ], "changes": [ { "version": [ "v19.2.0", "v18.13.0" ], "pr-url": "https://github.com/nodejs/node/pull/45214", "description": "Test runner now supports running in watch mode." } ] }, "stability": 1, "stabilityText": "Experimental", "desc": "Starts Node.js in watch mode.\nWhen in watch mode, changes in the watched files cause the Node.js process to\nrestart.\nBy default, watch mode will watch the entry point\nand any required or imported module.\nUse --watch-path
to specify what paths to watch.
This flag cannot be combined with\n--check
, --eval
, --interactive
, or the REPL.
node --watch index.js\n
",
"type": "module",
"displayName": "`--watch`"
},
{
"textRaw": "`--watch-path`",
"name": "`--watch-path`",
"meta": {
"added": [
"v18.11.0",
"v16.19.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Starts Node.js in watch mode and specifies what paths to watch.\nWhen in watch mode, changes in the watched paths cause the Node.js process to\nrestart.\nThis will turn off watching of required or imported modules, even when used in\ncombination with --watch
.
This flag cannot be combined with\n--check
, --eval
, --interactive
, --test
, or the REPL.
node --watch-path=./src --watch-path=./tests index.js\n
\nThis option is only supported on macOS and Windows.\nAn ERR_FEATURE_UNAVAILABLE_ON_PLATFORM
exception will be thrown\nwhen the option is used on a platform that does not support it.
Disable the clearing of the console when watch mode restarts the process.
\nnode --watch --watch-preserve-output test.js\n
",
"type": "module",
"displayName": "`--watch-preserve-output`"
},
{
"textRaw": "`--zero-fill-buffers`",
"name": "`--zero-fill-buffers`",
"meta": {
"added": [
"v6.0.0"
],
"changes": []
},
"desc": "Automatically zero-fills all newly allocated Buffer
and SlowBuffer
\ninstances.
The FORCE_COLOR
environment variable is used to\nenable ANSI colorized output. The value may be:
1
, true
, or the empty string ''
indicate 16-color support,2
to indicate 256-color support, or3
to indicate 16 million-color support.When FORCE_COLOR
is used and set to a supported value, both the NO_COLOR
,\nand NODE_DISABLE_COLORS
environment variables are ignored.
Any other value will result in colorized output being disabled.
", "type": "module", "displayName": "`FORCE_COLOR=[1, 2, 3]`" }, { "textRaw": "`NO_COLOR=NO_COLOR
is an alias for NODE_DISABLE_COLORS
. The value of the\nenvironment variable is arbitrary.
','
-separated list of core modules that should print debug information.
','
-separated list of core C++ modules that should print debug information.
When set, colors will not be used in the REPL.
", "type": "module", "displayName": "`NODE_DISABLE_COLORS=1`" }, { "textRaw": "`NODE_EXTRA_CA_CERTS=file`", "name": "`node_extra_ca_certs=file`", "meta": { "added": [ "v7.3.0" ], "changes": [] }, "desc": "When set, the well known \"root\" CAs (like VeriSign) will be extended with the\nextra certificates in file
. The file should consist of one or more trusted\ncertificates in PEM format. A message will be emitted (once) with\nprocess.emitWarning()
if the file is missing or\nmalformed, but any errors are otherwise ignored.
Neither the well known nor extra certificates are used when the ca
\noptions property is explicitly specified for a TLS or HTTPS client or server.
This environment variable is ignored when node
runs as setuid root or\nhas Linux file capabilities set.
The NODE_EXTRA_CA_CERTS
environment variable is only read when the Node.js\nprocess is first launched. Changing the value at runtime using\nprocess.env.NODE_EXTRA_CA_CERTS
has no effect on the current process.
Data path for ICU (Intl
object) data. Will extend linked-in data when compiled\nwith small-icu support.
When set to 1
, process warnings are silenced.
A space-separated list of command-line options. options...
are interpreted\nbefore command-line options, so command-line options will override or\ncompound after anything in options...
. Node.js will exit with an error if\nan option that is not allowed in the environment is used, such as -p
or a\nscript file.
If an option value contains a space, it can be escaped using double quotes:
\nNODE_OPTIONS='--require \"./my path/file.js\"'\n
\nA singleton flag passed as a command-line option will override the same flag\npassed into NODE_OPTIONS
:
# The inspector will be available on port 5555\nNODE_OPTIONS='--inspect=localhost:4444' node --inspect=localhost:5555\n
\nA flag that can be passed multiple times will be treated as if its\nNODE_OPTIONS
instances were passed first, and then its command-line\ninstances afterwards:
NODE_OPTIONS='--require \"./a.js\"' node --require \"./b.js\"\n# is equivalent to:\nnode --require \"./a.js\" --require \"./b.js\"\n
\nNode.js options that are allowed are:
\n\n--allow-addons
--allow-child-process
--allow-fs-read
--allow-fs-write
--allow-worker
--conditions
, -C
--diagnostic-dir
--disable-proto
--disable-warning
--dns-result-order
--enable-fips
--enable-network-family-autoselection
--enable-source-maps
--experimental-abortcontroller
--experimental-default-type
--experimental-detect-module
--experimental-import-meta-resolve
--experimental-json-modules
--experimental-loader
--experimental-modules
--experimental-network-imports
--experimental-permission
--experimental-policy
--experimental-shadow-realm
--experimental-specifier-resolution
--experimental-top-level-await
--experimental-vm-modules
--experimental-wasi-unstable-preview1
--experimental-wasm-modules
--experimental-websocket
--force-context-aware
--force-fips
--force-node-api-uncaught-exceptions-policy
--frozen-intrinsics
--heapsnapshot-near-heap-limit
--heapsnapshot-signal
--http-parser
--icu-data-dir
--import
--input-type
--insecure-http-parser
--inspect-brk
--inspect-port
, --debug-port
--inspect-publish-uid
--inspect
--max-http-header-size
--napi-modules
--no-addons
--no-deprecation
--no-experimental-fetch
--no-experimental-global-customevent
--no-experimental-global-navigator
--no-experimental-global-webcrypto
--no-experimental-repl-await
--no-extra-info-on-fatal-exception
--no-force-async-hooks-checks
--no-global-search-paths
--no-network-family-autoselection
--no-warnings
--node-memory-debug
--openssl-config
--openssl-legacy-provider
--openssl-shared-config
--pending-deprecation
--policy-integrity
--preserve-symlinks-main
--preserve-symlinks
--prof-process
--redirect-warnings
--report-compact
--report-dir
, --report-directory
--report-filename
--report-on-fatalerror
--report-on-signal
--report-signal
--report-uncaught-exception
--require
, -r
--secure-heap-min
--secure-heap
--snapshot-blob
--test-only
--test-reporter-destination
--test-reporter
--test-shard
--throw-deprecation
--title
--tls-cipher-list
--tls-keylog
--tls-max-v1.2
--tls-max-v1.3
--tls-min-v1.0
--tls-min-v1.1
--tls-min-v1.2
--tls-min-v1.3
--trace-atomics-wait
--trace-deprecation
--trace-event-categories
--trace-event-file-pattern
--trace-events-enabled
--trace-exit
--trace-sigint
--trace-sync-io
--trace-tls
--trace-uncaught
--trace-warnings
--track-heap-objects
--unhandled-rejections
--use-bundled-ca
--use-largepages
--use-openssl-ca
--v8-pool-size
--watch-path
--watch-preserve-output
--watch
--zero-fill-buffers
V8 options that are allowed are:
\n\n--abort-on-uncaught-exception
--disallow-code-generation-from-strings
--enable-etw-stack-walking
--huge-max-old-generation-size
--interpreted-frames-native-stack
--jitless
--max-old-space-size
--max-semi-space-size
--perf-basic-prof-only-functions
--perf-basic-prof
--perf-prof-unwinding-info
--perf-prof
--stack-trace-limit
--perf-basic-prof-only-functions
, --perf-basic-prof
,\n--perf-prof-unwinding-info
, and --perf-prof
are only available on Linux.
--enable-etw-stack-walking
is only available on Windows.
':'
-separated list of directories prefixed to the module search path.
On Windows, this is a ';'
-separated list instead.
When set to 1
, emit pending deprecation warnings.
Pending deprecations are generally identical to a runtime deprecation with the\nnotable exception that they are turned off by default and will not be emitted\nunless either the --pending-deprecation
command-line flag, or the\nNODE_PENDING_DEPRECATION=1
environment variable, is set. Pending deprecations\nare used to provide a kind of selective \"early warning\" mechanism that\ndevelopers may leverage to detect deprecated API usage.
Set the number of pending pipe instance handles when the pipe server is waiting\nfor connections. This setting applies to Windows only.
", "type": "module", "displayName": "`NODE_PENDING_PIPE_INSTANCES=instances`" }, { "textRaw": "`NODE_PRESERVE_SYMLINKS=1`", "name": "`node_preserve_symlinks=1`", "meta": { "added": [ "v7.1.0" ], "changes": [] }, "desc": "When set to 1
, instructs the module loader to preserve symbolic links when\nresolving and caching modules.
When set, process warnings will be emitted to the given file instead of\nprinting to stderr. The file will be created if it does not exist, and will be\nappended to if it does. If an error occurs while attempting to write the\nwarning to the file, the warning will be written to stderr instead. This is\nequivalent to using the --redirect-warnings=file
command-line flag.
Path to a Node.js module which will be loaded in place of the built-in REPL.\nOverriding this value to an empty string (''
) will use the built-in REPL.
Path to the file used to store the persistent REPL history. The default path is\n~/.node_repl_history
, which is overridden by this variable. Setting the value\nto an empty string (''
or ' '
) disables persistent REPL history.
If value
equals '1'
, the check for a supported platform is skipped during\nNode.js startup. Node.js might not execute correctly. Any issues encountered\non unsupported platforms will not be fixed.
If value
equals 'child'
, test reporter options will be overridden and test\noutput will be sent to stdout in the TAP format. If any other value is provided,\nNode.js makes no guarantees about the reporter format used or its stability.
If value
equals '0'
, certificate validation is disabled for TLS connections.\nThis makes TLS, and HTTPS by extension, insecure. The use of this environment\nvariable is strongly discouraged.
When set, Node.js will begin outputting V8 JavaScript code coverage and\nSource Map data to the directory provided as an argument (coverage\ninformation is written as JSON to files with a coverage
prefix).
NODE_V8_COVERAGE
will automatically propagate to subprocesses, making it\neasier to instrument applications that call the child_process.spawn()
family\nof functions. NODE_V8_COVERAGE
can be set to an empty string, to prevent\npropagation.
Coverage is output as an array of ScriptCoverage objects on the top-level\nkey result
:
{\n \"result\": [\n {\n \"scriptId\": \"67\",\n \"url\": \"internal/tty.js\",\n \"functions\": []\n }\n ]\n}\n
",
"type": "module",
"displayName": "Coverage output"
},
{
"textRaw": "Source map cache",
"name": "source_map_cache",
"stability": 1,
"stabilityText": "Experimental",
"desc": "If found, source map data is appended to the top-level key source-map-cache
\non the JSON coverage object.
source-map-cache
is an object with keys representing the files source maps\nwere extracted from, and values which include the raw source-map URL\n(in the key url
), the parsed Source Map v3 information (in the key data
),\nand the line lengths of the source file (in the key lineLengths
).
{\n \"result\": [\n {\n \"scriptId\": \"68\",\n \"url\": \"file:///absolute/path/to/source.js\",\n \"functions\": []\n }\n ],\n \"source-map-cache\": {\n \"file:///absolute/path/to/source.js\": {\n \"url\": \"./path-to-map.json\",\n \"data\": {\n \"version\": 3,\n \"sources\": [\n \"file:///absolute/path/to/original.js\"\n ],\n \"names\": [\n \"Foo\",\n \"console\",\n \"info\"\n ],\n \"mappings\": \"MAAMA,IACJC,YAAaC\",\n \"sourceRoot\": \"./\"\n },\n \"lineLengths\": [\n 13,\n 62,\n 38,\n 27\n ]\n }\n }\n}\n
",
"type": "module",
"displayName": "Source map cache"
}
],
"type": "module",
"displayName": "`NODE_V8_COVERAGE=dir`"
},
{
"textRaw": "`OPENSSL_CONF=file`",
"name": "`openssl_conf=file`",
"meta": {
"added": [
"v6.11.0"
],
"changes": []
},
"desc": "Load an OpenSSL configuration file on startup. Among other uses, this can be\nused to enable FIPS-compliant crypto if Node.js is built with\n./configure --openssl-fips
.
If the --openssl-config
command-line option is used, the environment\nvariable is ignored.
If --use-openssl-ca
is enabled, this overrides and sets OpenSSL's directory\ncontaining trusted certificates.
Be aware that unless the child environment is explicitly set, this environment\nvariable will be inherited by any child processes, and if they use OpenSSL, it\nmay cause them to trust the same CAs as node.
", "type": "module", "displayName": "`SSL_CERT_DIR=dir`" }, { "textRaw": "`SSL_CERT_FILE=file`", "name": "`ssl_cert_file=file`", "meta": { "added": [ "v7.7.0" ], "changes": [] }, "desc": "If --use-openssl-ca
is enabled, this overrides and sets OpenSSL's file\ncontaining trusted certificates.
Be aware that unless the child environment is explicitly set, this environment\nvariable will be inherited by any child processes, and if they use OpenSSL, it\nmay cause them to trust the same CAs as node.
", "type": "module", "displayName": "`SSL_CERT_FILE=file`" }, { "textRaw": "`TZ`", "name": "`tz`", "meta": { "added": [ "v0.0.1" ], "changes": [ { "version": [ "v16.2.0" ], "pr-url": "https://github.com/nodejs/node/pull/38642", "description": "Changing the TZ variable using process.env.TZ = changes the timezone on Windows as well." }, { "version": [ "v13.0.0" ], "pr-url": "https://github.com/nodejs/node/pull/20026", "description": "Changing the TZ variable using process.env.TZ = changes the timezone on POSIX systems." } ] }, "desc": "The TZ
environment variable is used to specify the timezone configuration.
While Node.js does not support all of the various ways that TZ
is handled in\nother environments, it does support basic timezone IDs (such as\n'Etc/UTC'
, 'Europe/Paris'
, or 'America/New_York'
).\nIt may support a few other abbreviations or aliases, but these are strongly\ndiscouraged and not guaranteed.
$ TZ=Europe/Dublin node -pe \"new Date().toString()\"\nWed May 12 2021 20:30:48 GMT+0100 (Irish Standard Time)\n
",
"type": "module",
"displayName": "`TZ`"
},
{
"textRaw": "`UV_THREADPOOL_SIZE=size`",
"name": "`uv_threadpool_size=size`",
"desc": "Set the number of threads used in libuv's threadpool to size
threads.
Asynchronous system APIs are used by Node.js whenever possible, but where they\ndo not exist, libuv's threadpool is used to create asynchronous node APIs based\non synchronous system APIs. Node.js APIs that use the threadpool are:
\nfs
APIs, other than the file watcher APIs and those that are explicitly\nsynchronouscrypto.pbkdf2()
, crypto.scrypt()
,\ncrypto.randomBytes()
, crypto.randomFill()
, crypto.generateKeyPair()
dns.lookup()
zlib
APIs, other than those that are explicitly synchronousBecause libuv's threadpool has a fixed size, it means that if for whatever\nreason any of these APIs takes a long time, other (seemingly unrelated) APIs\nthat run in libuv's threadpool will experience degraded performance. In order to\nmitigate this issue, one potential solution is to increase the size of libuv's\nthreadpool by setting the 'UV_THREADPOOL_SIZE'
environment variable to a value\ngreater than 4
(its current default value). For more information, see the\nlibuv threadpool documentation.
Enable or disable libuv's use of io_uring
on supported platforms.
On supported platforms, io_uring
can significantly improve the performance of\nvarious asynchronous I/O operations.
io_uring
is disabled by default due to security concerns. When io_uring
\nis enabled, applications must not change the user identity of the process at\nruntime. In this case, JavaScript functions such as process.setuid()
are\nunavailable, and native addons must not invoke system functions such as\nsetuid(2)
.
This environment variable is implemented by a dependency of Node.js and may be\nremoved in future versions of Node.js. No stability guarantees are provided for\nthe behavior of this environment variable.
", "type": "module", "displayName": "`UV_USE_IO_URING=value`" } ], "type": "misc", "displayName": "Environment variables" }, { "textRaw": "Useful V8 options", "name": "useful_v8_options", "desc": "V8 has its own set of CLI options. Any V8 CLI option that is provided to node
\nwill be passed on to V8 to handle. V8's options have no stability guarantee.\nThe V8 team themselves don't consider them to be part of their formal API,\nand reserve the right to change them at any time. Likewise, they are not\ncovered by the Node.js stability guarantees. Many of the V8\noptions are of interest only to V8 developers. Despite this, there is a small\nset of V8 options that are widely applicable to Node.js, and they are\ndocumented here:
Sets the max memory size of V8's old memory section. As memory\nconsumption approaches the limit, V8 will spend more time on\ngarbage collection in an effort to free unused memory.
\nOn a machine with 2 GiB of memory, consider setting this to\n1536 (1.5 GiB) to leave some memory for other uses and avoid swapping.
\nnode --max-old-space-size=1536 index.js\n
",
"type": "module",
"displayName": "`--max-old-space-size=SIZE` (in megabytes)"
},
{
"textRaw": "`--max-semi-space-size=SIZE` (in megabytes)",
"name": "`--max-semi-space-size=size`_(in_megabytes)",
"desc": "Sets the maximum semi-space size for V8's scavenge garbage collector in\nMiB (megabytes).\nIncreasing the max size of a semi-space may improve throughput for Node.js at\nthe cost of more memory consumption.
\nSince the young generation size of the V8 heap is three times (see\nYoungGenerationSizeFromSemiSpaceSize
in V8) the size of the semi-space,\nan increase of 1 MiB to semi-space applies to each of the three individual\nsemi-spaces and causes the heap size to increase by 3 MiB. The throughput\nimprovement depends on your workload (see #42511).
The default value is 16 MiB for 64-bit systems and 8 MiB for 32-bit systems. To\nget the best configuration for your application, you should try different\nmax-semi-space-size values when running benchmarks for your application.
\nFor example, benchmark on a 64-bit systems:
\nfor MiB in 16 32 64 128; do\n node --max-semi-space-size=$MiB index.js\ndone\n
",
"type": "module",
"displayName": "`--max-semi-space-size=SIZE` (in megabytes)"
}
],
"type": "misc",
"displayName": "Useful V8 options"
}
],
"source": "doc/api/cli.md"
},
{
"textRaw": "Corepack",
"name": "Corepack",
"introduced_in": "v14.19.0",
"type": "misc",
"meta": {
"added": [
"v16.9.0",
"v14.19.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "Corepack is an experimental tool to help with\nmanaging versions of your package managers. It exposes binary proxies for\neach supported package manager that, when called, will identify whatever\npackage manager is configured for the current project, download it if needed,\nand finally run it.
\nDespite Corepack being distributed with default installs of Node.js, the package\nmanagers managed by Corepack are not part of the Node.js distribution and:
\nThis feature simplifies two core workflows:
\nIt eases new contributor onboarding, since they won't have to follow\nsystem-specific installation processes anymore just to have the package\nmanager you want them to.
\nIt allows you to ensure that everyone in your team will use exactly the\npackage manager version you intend them to, without them having to\nmanually synchronize it each time you need to make an update.
\nDue to its experimental status, Corepack currently needs to be explicitly\nenabled to have any effect. To do that, run corepack enable
, which\nwill set up the symlinks in your environment next to the node
binary\n(and overwrite the existing symlinks if necessary).
From this point forward, any call to the supported binaries will work\nwithout further setup. Should you experience a problem, run\ncorepack disable
to remove the proxies from your system (and consider\nopening an issue on the Corepack repository to let us know).
The Corepack proxies will find the closest package.json
file in your\ncurrent directory hierarchy to extract its \"packageManager\"
property.
If the value corresponds to a supported package manager, Corepack will make\nsure that all calls to the relevant binaries are run against the requested\nversion, downloading it on demand if needed, and aborting if it cannot be\nsuccessfully retrieved.
\nYou can use corepack use
to ask Corepack to update your local\npackage.json
to use the package manager of your choice:
corepack use pnpm@7.x # sets the latest 7.x version in the package.json\ncorepack use yarn@* # sets the latest version in the package.json\n
",
"type": "module",
"displayName": "Configuring a package"
},
{
"textRaw": "Upgrading the global versions",
"name": "upgrading_the_global_versions",
"desc": "When running outside of an existing project (for example when running\nyarn init
), Corepack will by default use predefined versions roughly\ncorresponding to the latest stable releases from each tool. Those versions can\nbe overridden by running the corepack install
command along with the\npackage manager version you wish to set:
corepack install --global yarn@x.y.z\n
\nAlternately, a tag or range may be used:
\ncorepack install --global pnpm@*\ncorepack install --global yarn@stable\n
",
"type": "module",
"displayName": "Upgrading the global versions"
},
{
"textRaw": "Offline workflow",
"name": "offline_workflow",
"desc": "Many production environments don't have network access. Since Corepack\nusually downloads the package manager releases straight from their registries,\nit can conflict with such environments. To avoid that happening, call the\ncorepack pack
command while you still have network access (typically at\nthe same time you're preparing your deploy image). This will ensure that the\nrequired package managers are available even without network access.
The pack
command has various flags. Consult the detailed\nCorepack documentation for more information.
The following binaries are provided through Corepack:
\nPackage manager | \nBinary names | \n
---|---|
Yarn | \nyarn , yarnpkg | \n
pnpm | \npnpm , pnpx | \n
While Corepack could support npm like any other package manager, its\nshims aren't enabled by default. This has a few consequences:
\nIt's always possible to run a npm
command within a project configured to\nbe used with another package manager, since Corepack cannot intercept it.
While npm
is a valid option in the \"packageManager\"
property, the\nlack of shim will cause the global npm to be used.
npm prevents accidentally overriding the Corepack binaries when doing a global\ninstall. To avoid this problem, consider one of the following options:
\nDon't run this command; Corepack will provide the package manager\nbinaries anyway and will ensure that the requested versions are always\navailable, so installing the package managers explicitly isn't needed.
\nAdd the --force
flag to npm install
; this will tell npm that it's fine to\noverride binaries, but you'll erase the Corepack ones in the process. (Run\ncorepack enable
to add them back.)
Node.js includes a command-line debugging utility. The Node.js debugger client\nis not a full-featured debugger, but simple stepping and inspection are\npossible.
\nTo use it, start Node.js with the inspect
argument followed by the path to the\nscript to debug.
$ node inspect myscript.js\n< Debugger listening on ws://127.0.0.1:9229/621111f9-ffcb-4e82-b718-48a145fa5db8\n< For help, see: https://nodejs.org/en/docs/inspector\n<\nconnecting to 127.0.0.1:9229 ... ok\n< Debugger attached.\n<\n ok\nBreak on start in myscript.js:2\n 1 // myscript.js\n> 2 global.x = 5;\n 3 setTimeout(() => {\n 4 debugger;\ndebug>\n
\nThe debugger automatically breaks on the first executable line. To instead\nrun until the first breakpoint (specified by a debugger
statement), set\nthe NODE_INSPECT_RESUME_ON_START
environment variable to 1
.
$ cat myscript.js\n// myscript.js\nglobal.x = 5;\nsetTimeout(() => {\n debugger;\n console.log('world');\n}, 1000);\nconsole.log('hello');\n$ NODE_INSPECT_RESUME_ON_START=1 node inspect myscript.js\n< Debugger listening on ws://127.0.0.1:9229/f1ed133e-7876-495b-83ae-c32c6fc319c2\n< For help, see: https://nodejs.org/en/docs/inspector\n<\nconnecting to 127.0.0.1:9229 ... ok\n< Debugger attached.\n<\n< hello\n<\nbreak in myscript.js:4\n 2 global.x = 5;\n 3 setTimeout(() => {\n> 4 debugger;\n 5 console.log('world');\n 6 }, 1000);\ndebug> next\nbreak in myscript.js:5\n 3 setTimeout(() => {\n 4 debugger;\n> 5 console.log('world');\n 6 }, 1000);\n 7 console.log('hello');\ndebug> repl\nPress Ctrl+C to leave debug repl\n> x\n5\n> 2 + 2\n4\ndebug> next\n< world\n<\nbreak in myscript.js:6\n 4 debugger;\n 5 console.log('world');\n> 6 }, 1000);\n 7 console.log('hello');\n 8\ndebug> .exit\n$\n
\nThe repl
command allows code to be evaluated remotely. The next
command\nsteps to the next line. Type help
to see what other commands are available.
Pressing enter
without typing a command will repeat the previous debugger\ncommand.
It is possible to watch expression and variable values while debugging. On\nevery breakpoint, each expression from the watchers list will be evaluated\nin the current context and displayed immediately before the breakpoint's\nsource code listing.
\nTo begin watching an expression, type watch('my_expression')
. The command\nwatchers
will print the active watchers. To remove a watcher, type\nunwatch('my_expression')
.
cont
, c
: Continue executionnext
, n
: Step nextstep
, s
: Step inout
, o
: Step outpause
: Pause running code (like pause button in Developer Tools)setBreakpoint()
, sb()
: Set breakpoint on current linesetBreakpoint(line)
, sb(line)
: Set breakpoint on specific linesetBreakpoint('fn()')
, sb(...)
: Set breakpoint on a first statement in\nfunction's bodysetBreakpoint('script.js', 1)
, sb(...)
: Set breakpoint on first line of\nscript.js
setBreakpoint('script.js', 1, 'num < 4')
, sb(...)
: Set conditional\nbreakpoint on first line of script.js
that only breaks when num < 4
\nevaluates to true
clearBreakpoint('script.js', 1)
, cb(...)
: Clear breakpoint in script.js
\non line 1It is also possible to set a breakpoint in a file (module) that\nis not loaded yet:
\n$ node inspect main.js\n< Debugger listening on ws://127.0.0.1:9229/48a5b28a-550c-471b-b5e1-d13dd7165df9\n< For help, see: https://nodejs.org/en/docs/inspector\n<\nconnecting to 127.0.0.1:9229 ... ok\n< Debugger attached.\n<\nBreak on start in main.js:1\n> 1 const mod = require('./mod.js');\n 2 mod.hello();\n 3 mod.hello();\ndebug> setBreakpoint('mod.js', 22)\nWarning: script 'mod.js' was not loaded yet.\ndebug> c\nbreak in mod.js:22\n 20 // USE OR OTHER DEALINGS IN THE SOFTWARE.\n 21\n>22 exports.hello = function() {\n 23 return 'hello from module';\n 24 };\ndebug>\n
\nIt is also possible to set a conditional breakpoint that only breaks when a\ngiven expression evaluates to true
:
$ node inspect main.js\n< Debugger listening on ws://127.0.0.1:9229/ce24daa8-3816-44d4-b8ab-8273c8a66d35\n< For help, see: https://nodejs.org/en/docs/inspector\n<\nconnecting to 127.0.0.1:9229 ... ok\n< Debugger attached.\nBreak on start in main.js:7\n 5 }\n 6\n> 7 addOne(10);\n 8 addOne(-1);\n 9\ndebug> setBreakpoint('main.js', 4, 'num < 0')\n 1 'use strict';\n 2\n 3 function addOne(num) {\n> 4 return num + 1;\n 5 }\n 6\n 7 addOne(10);\n 8 addOne(-1);\n 9\ndebug> cont\nbreak in main.js:4\n 2\n 3 function addOne(num) {\n> 4 return num + 1;\n 5 }\n 6\ndebug> exec('num')\n-1\ndebug>\n
",
"type": "module",
"displayName": "Breakpoints"
},
{
"textRaw": "Information",
"name": "information",
"desc": "backtrace
, bt
: Print backtrace of current execution framelist(5)
: List scripts source code with 5 line context (5 lines before and\nafter)watch(expr)
: Add expression to watch listunwatch(expr)
: Remove expression from watch listunwatch(index)
: Remove expression at specific index from watch listwatchers
: List all watchers and their values (automatically listed on each\nbreakpoint)repl
: Open debugger's repl for evaluation in debugging script's contextexec expr
, p expr
: Execute an expression in debugging script's context and\nprint its valueprofile
: Start CPU profiling sessionprofileEnd
: Stop current CPU profiling sessionprofiles
: List all completed CPU profiling sessionsprofiles[n].save(filepath = 'node.cpuprofile')
: Save CPU profiling session\nto disk as JSONtakeHeapSnapshot(filepath = 'node.heapsnapshot')
: Take a heap snapshot\nand save to disk as JSONrun
: Run script (automatically runs on debugger's start)restart
: Restart scriptkill
: Kill scriptscripts
: List all loaded scriptsversion
: Display V8's versionV8 Inspector integration allows attaching Chrome DevTools to Node.js\ninstances for debugging and profiling. It uses the\nChrome DevTools Protocol.
\nV8 Inspector can be enabled by passing the --inspect
flag when starting a\nNode.js application. It is also possible to supply a custom port with that flag,\ne.g. --inspect=9222
will accept DevTools connections on port 9222.
To break on the first line of the application code, pass the --inspect-brk
\nflag instead of --inspect
.
$ node --inspect index.js\nDebugger listening on ws://127.0.0.1:9229/dc9010dd-f8b8-4ac5-a510-c1a114ec7d29\nFor help, see: https://nodejs.org/en/docs/inspector\n
\n(In the example above, the UUID dc9010dd-f8b8-4ac5-a510-c1a114ec7d29\nat the end of the URL is generated on the fly, it varies in different\ndebugging sessions.)
\nIf the Chrome browser is older than 66.0.3345.0,\nuse inspector.html
instead of js_app.html
in the above URL.
Chrome DevTools doesn't support debugging worker threads yet.\nndb can be used to debug them.
", "type": "module", "displayName": "V8 inspector integration for Node.js" } ], "type": "misc", "displayName": "Advanced usage" } ], "source": "doc/api/debugger.md" }, { "textRaw": "Deprecated APIs", "name": "Deprecated APIs", "introduced_in": "v7.7.0", "type": "misc", "desc": "Node.js APIs might be deprecated for any of the following reasons:
\nNode.js uses four kinds of deprecations:
\nnode_modules
code only)A Documentation-only deprecation is one that is expressed only within the\nNode.js API docs. These generate no side-effects while running Node.js.\nSome Documentation-only deprecations trigger a runtime warning when launched\nwith --pending-deprecation
flag (or its alternative,\nNODE_PENDING_DEPRECATION=1
environment variable), similarly to Runtime\ndeprecations below. Documentation-only deprecations that support that flag\nare explicitly labeled as such in the\nlist of Deprecated APIs.
An Application deprecation for only non-node_modules
code will, by default,\ngenerate a process warning that will be printed to stderr
the first time\nthe deprecated API is used in code that's not loaded from node_modules
.\nWhen the --throw-deprecation
command-line flag is used, a Runtime\ndeprecation will cause an error to be thrown. When\n--pending-deprecation
is used, warnings will also be emitted for\ncode loaded from node_modules
.
A runtime deprecation for all code is similar to the runtime deprecation\nfor non-node_modules
code, except that it also emits a warning for\ncode loaded from node_modules
.
An End-of-Life deprecation is used when functionality is or will soon be removed\nfrom Node.js.
", "miscs": [ { "textRaw": "Revoking deprecations", "name": "revoking_deprecations", "desc": "Occasionally, the deprecation of an API might be reversed. In such situations,\nthis document will be updated with information relevant to the decision.\nHowever, the deprecation identifier will not be modified.
", "type": "misc", "displayName": "Revoking deprecations" }, { "textRaw": "List of deprecated APIs", "name": "list_of_deprecated_apis", "modules": [ { "textRaw": "DEP0001: `http.OutgoingMessage.prototype.flush`", "name": "dep0001:_`http.outgoingmessage.prototype.flush`", "meta": { "changes": [ { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/31164", "description": "End-of-Life." }, { "version": [ "v6.12.0", "v4.8.6" ], "pr-url": "https://github.com/nodejs/node/pull/10116", "description": "A deprecation code has been assigned." }, { "version": "v1.6.0", "pr-url": "https://github.com/nodejs/node/pull/1156", "description": "Runtime deprecation." } ] }, "desc": "Type: End-of-Life
\nOutgoingMessage.prototype.flush()
has been removed. Use\nOutgoingMessage.prototype.flushHeaders()
instead.
Type: End-of-Life
\nThe _linklist
module is deprecated. Please use a userland alternative.
Type: End-of-Life
\nThe _writableState.buffer
has been removed. Use _writableState.getBuffer()
\ninstead.
Type: End-of-Life
\nThe CryptoStream.prototype.readyState
property was removed.
Type: Application (non-node_modules
code only)
The Buffer()
function and new Buffer()
constructor are deprecated due to\nAPI usability issues that can lead to accidental security issues.
As an alternative, use one of the following methods of constructing Buffer
\nobjects:
Buffer.alloc(size[, fill[, encoding]])
: Create a Buffer
with\ninitialized memory.Buffer.allocUnsafe(size)
: Create a Buffer
with\nuninitialized memory.Buffer.allocUnsafeSlow(size)
: Create a Buffer
with uninitialized\nmemory.Buffer.from(array)
: Create a Buffer
with a copy of array
Buffer.from(arrayBuffer[, byteOffset[, length]])
-\nCreate a Buffer
that wraps the given arrayBuffer
.Buffer.from(buffer)
: Create a Buffer
that copies buffer
.Buffer.from(string[, encoding])
: Create a Buffer
\nthat copies string
.Without --pending-deprecation
, runtime warnings occur only for code not in\nnode_modules
. This means there will not be deprecation warnings for\nBuffer()
usage in dependencies. With --pending-deprecation
, a runtime\nwarning results no matter where the Buffer()
usage occurs.
Type: End-of-Life
\nWithin the child_process
module's spawn()
, fork()
, and exec()
\nmethods, the options.customFds
option is deprecated. The options.stdio
\noption should be used instead.
Type: End-of-Life
\nIn an earlier version of the Node.js cluster
, a boolean property with the name\nsuicide
was added to the Worker
object. The intent of this property was to\nprovide an indication of how and why the Worker
instance exited. In Node.js\n6.0.0, the old property was deprecated and replaced with a new\nworker.exitedAfterDisconnect
property. The old property name did not\nprecisely describe the actual semantics and was unnecessarily emotion-laden.
Type: Documentation-only
\nThe node:constants
module is deprecated. When requiring access to constants\nrelevant to specific Node.js builtin modules, developers should instead refer\nto the constants
property exposed by the relevant module. For instance,\nrequire('node:fs').constants
and require('node:os').constants
.
Type: End-of-Life
\nUse of the crypto.pbkdf2()
API without specifying a digest was deprecated\nin Node.js 6.0 because the method defaulted to using the non-recommended\n'SHA1'
digest. Previously, a deprecation warning was printed. Starting in\nNode.js 8.0.0, calling crypto.pbkdf2()
or crypto.pbkdf2Sync()
with\ndigest
set to undefined
will throw a TypeError
.
Beginning in Node.js v11.0.0, calling these functions with digest
set to\nnull
would print a deprecation warning to align with the behavior when digest
\nis undefined
.
Now, however, passing either undefined
or null
will throw a TypeError
.
Type: End-of-Life
\nThe crypto.createCredentials()
API was removed. Please use\ntls.createSecureContext()
instead.
Type: End-of-Life
\nThe crypto.Credentials
class was removed. Please use tls.SecureContext
\ninstead.
Type: End-of-Life
\nDomain.dispose()
has been removed. Recover from failed I/O actions\nexplicitly via error event handlers set on the domain instead.
Type: End-of-Life
\nCalling an asynchronous function without a callback throws a TypeError
\nin Node.js 10.0.0 onwards. See https://github.com/nodejs/node/pull/12562.
Type: End-of-Life
\nThe fs.read()
legacy String
interface is deprecated. Use the Buffer
\nAPI as mentioned in the documentation instead.
Type: End-of-Life
\nThe fs.readSync()
legacy String
interface is deprecated. Use the\nBuffer
API as mentioned in the documentation instead.
Type: End-of-Life
\nThe GLOBAL
and root
aliases for the global
property were deprecated\nin Node.js 6.0.0 and have since been removed.
Type: End-of-Life
\nIntl.v8BreakIterator
was a non-standard extension and has been removed.\nSee Intl.Segmenter
.
Type: End-of-Life
\nUnhandled promise rejections are deprecated. By default, promise rejections\nthat are not handled terminate the Node.js process with a non-zero exit\ncode. To change the way Node.js treats unhandled rejections, use the\n--unhandled-rejections
command-line option.
Type: End-of-Life
\nIn certain cases, require('.')
could resolve outside the package directory.\nThis behavior has been removed.
Type: End-of-Life
\nThe Server.connections
property was deprecated in Node.js v0.9.7 and has\nbeen removed. Please use the Server.getConnections()
method instead.
Type: End-of-Life
\nThe Server.listenFD()
method was deprecated and removed. Please use\nServer.listen({fd: <number>})
instead.
Type: End-of-Life
\nThe os.tmpDir()
API was deprecated in Node.js 7.0.0 and has since been\nremoved. Please use os.tmpdir()
instead.
Type: End-of-Life
\nThe os.getNetworkInterfaces()
method is deprecated. Please use the\nos.networkInterfaces()
method instead.
Type: End-of-Life
\nThe REPLServer.prototype.convertToContext()
API has been removed.
Type: Runtime
\nThe node:sys
module is deprecated. Please use the util
module instead.
Type: End-of-Life
\nutil.print()
has been removed. Please use console.log()
instead.
Type: End-of-Life
\nutil.puts()
has been removed. Please use console.log()
instead.
Type: End-of-Life
\nutil.debug()
has been removed. Please use console.error()
instead.
Type: End-of-Life
\nutil.error()
has been removed. Please use console.error()
instead.
Type: Documentation-only
\nThe SlowBuffer
class is deprecated. Please use\nBuffer.allocUnsafeSlow(size)
instead.
Type: Documentation-only
\nThe ecdh.setPublicKey()
method is now deprecated as its inclusion in the\nAPI is not useful.
Type: Documentation-only
\nThe domain
module is deprecated and should not be used.
Type: Documentation-only
\nThe events.listenerCount(emitter, eventName)
API is\ndeprecated. Please use emitter.listenerCount(eventName)
instead.
Type: Documentation-only
\nThe fs.exists(path, callback)
API is deprecated. Please use\nfs.stat()
or fs.access()
instead.
Type: Documentation-only
\nThe fs.lchmod(path, mode, callback)
API is deprecated.
Type: Documentation-only
\nThe fs.lchmodSync(path, mode)
API is deprecated.
Type: Deprecation revoked
\nThe fs.lchown(path, uid, gid, callback)
API was deprecated. The\ndeprecation was revoked because the requisite supporting APIs were added in\nlibuv.
Type: Deprecation revoked
\nThe fs.lchownSync(path, uid, gid)
API was deprecated. The deprecation was\nrevoked because the requisite supporting APIs were added in libuv.
Type: Documentation-only
\nThe require.extensions
property is deprecated.
Type: Runtime
\nThe punycode
module is deprecated. Please use a userland alternative\ninstead.
Type: End-of-Life
\nThe NODE_REPL_HISTORY_FILE
environment variable was removed. Please use\nNODE_REPL_HISTORY
instead.
Type: End-of-Life
\nThe tls.CryptoStream
class was removed. Please use\ntls.TLSSocket
instead.
Type: Documentation-only
\nThe tls.SecurePair
class is deprecated. Please use\ntls.TLSSocket
instead.
Type: Documentation-only
\nThe util.isArray()
API is deprecated. Please use Array.isArray()
\ninstead.
Type: Documentation-only
\nThe util.isBoolean()
API is deprecated.
Type: Documentation-only
\nThe util.isBuffer()
API is deprecated. Please use\nBuffer.isBuffer()
instead.
Type: Documentation-only
\nThe util.isDate()
API is deprecated.
Type: Documentation-only
\nThe util.isError()
API is deprecated.
Type: Documentation-only
\nThe util.isFunction()
API is deprecated.
Type: Documentation-only
\nThe util.isNull()
API is deprecated.
Type: Documentation-only
\nThe util.isNullOrUndefined()
API is deprecated.
Type: Documentation-only
\nThe util.isNumber()
API is deprecated.
Type: Documentation-only
\nThe util.isObject()
API is deprecated.
Type: Documentation-only
\nThe util.isPrimitive()
API is deprecated.
Type: Documentation-only
\nThe util.isRegExp()
API is deprecated.
Type: Documentation-only
\nThe util.isString()
API is deprecated.
Type: Documentation-only
\nThe util.isSymbol()
API is deprecated.
Type: Documentation-only
\nThe util.isUndefined()
API is deprecated.
Type: Documentation-only
\nThe util.log()
API is deprecated.
Type: Documentation-only
\nThe util._extend()
API is deprecated.
Type: End-of-Life
\nThe fs.SyncWriteStream
class was never intended to be a publicly accessible\nAPI and has been removed. No alternative API is available. Please use a userland\nalternative.
Type: End-of-Life
\n--debug
activates the legacy V8 debugger interface, which was removed as\nof V8 5.8. It is replaced by Inspector which is activated with --inspect
\ninstead.
Type: Documentation-only
\nThe node:http
module ServerResponse.prototype.writeHeader()
API is\ndeprecated. Please use ServerResponse.prototype.writeHead()
instead.
The ServerResponse.prototype.writeHeader()
method was never documented as an\nofficially supported API.
Type: Runtime
\nThe tls.createSecurePair()
API was deprecated in documentation in Node.js\n0.11.3. Users should use tls.Socket
instead.
Type: End-of-Life
\nThe node:repl
module's REPL_MODE_MAGIC
constant, used for replMode
option,\nhas been removed. Its behavior has been functionally identical to that of\nREPL_MODE_SLOPPY
since Node.js 6.0.0, when V8 5.0 was imported. Please use\nREPL_MODE_SLOPPY
instead.
The NODE_REPL_MODE
environment variable is used to set the underlying\nreplMode
of an interactive node
session. Its value, magic
, is also\nremoved. Please use sloppy
instead.
Type: Runtime
\nThe node:http
module OutgoingMessage.prototype._headers
and\nOutgoingMessage.prototype._headerNames
properties are deprecated. Use one of\nthe public methods (e.g. OutgoingMessage.prototype.getHeader()
,\nOutgoingMessage.prototype.getHeaders()
,\nOutgoingMessage.prototype.getHeaderNames()
,\nOutgoingMessage.prototype.getRawHeaderNames()
,\nOutgoingMessage.prototype.hasHeader()
,\nOutgoingMessage.prototype.removeHeader()
,\nOutgoingMessage.prototype.setHeader()
) for working with outgoing headers.
The OutgoingMessage.prototype._headers
and\nOutgoingMessage.prototype._headerNames
properties were never documented as\nofficially supported properties.
Type: Documentation-only
\nThe node:http
module OutgoingMessage.prototype._renderHeaders()
API is\ndeprecated.
The OutgoingMessage.prototype._renderHeaders
property was never documented as\nan officially supported API.
Type: End-of-Life
\nnode debug
corresponds to the legacy CLI debugger which has been replaced with\na V8-inspector based CLI debugger available through node inspect
.
Type: End-of-Life
\nDebugContext has been removed in V8 and is not available in Node.js 10+.
\nDebugContext was an experimental API.
", "type": "module", "displayName": "DEP0069: `vm.runInDebugContext(string)`" }, { "textRaw": "DEP0070: `async_hooks.currentId()`", "name": "dep0070:_`async_hooks.currentid()`", "meta": { "changes": [ { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/14414", "description": "End-of-Life." }, { "version": "v8.2.0", "pr-url": "https://github.com/nodejs/node/pull/13490", "description": "Runtime deprecation." } ] }, "desc": "Type: End-of-Life
\nasync_hooks.currentId()
was renamed to async_hooks.executionAsyncId()
for\nclarity.
This change was made while async_hooks
was an experimental API.
Type: End-of-Life
\nasync_hooks.triggerId()
was renamed to async_hooks.triggerAsyncId()
for\nclarity.
This change was made while async_hooks
was an experimental API.
Type: End-of-Life
\nasync_hooks.AsyncResource.triggerId()
was renamed to\nasync_hooks.AsyncResource.triggerAsyncId()
for clarity.
This change was made while async_hooks
was an experimental API.
Type: End-of-Life
\nAccessing several internal, undocumented properties of net.Server
instances\nwith inappropriate names is deprecated.
As the original API was undocumented and not generally useful for non-internal\ncode, no replacement API is provided.
", "type": "module", "displayName": "DEP0073: Several internal properties of `net.Server`" }, { "textRaw": "DEP0074: `REPLServer.bufferedCommand`", "name": "dep0074:_`replserver.bufferedcommand`", "meta": { "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/33286", "description": "End-of-Life." }, { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/13687", "description": "Runtime deprecation." } ] }, "desc": "Type: End-of-Life
\nThe REPLServer.bufferedCommand
property was deprecated in favor of\nREPLServer.clearBufferedCommand()
.
Type: End-of-Life
\nREPLServer.parseREPLKeyword()
was removed from userland visibility.
Type: End-of-Life
\ntls.parseCertString()
was a trivial parsing helper that was made public by\nmistake. While it was supposed to parse certificate subject and issuer strings,\nit never handled multi-value Relative Distinguished Names correctly.
Earlier versions of this document suggested using querystring.parse()
as an\nalternative to tls.parseCertString()
. However, querystring.parse()
also does\nnot handle all certificate subjects correctly and should not be used.
Type: Runtime
\nModule._debug()
is deprecated.
The Module._debug()
function was never documented as an officially\nsupported API.
Type: End-of-Life
\nREPLServer.turnOffEditorMode()
was removed from userland visibility.
Type: End-of-Life
\nUsing a property named inspect
on an object to specify a custom inspection\nfunction for util.inspect()
is deprecated. Use util.inspect.custom
\ninstead. For backward compatibility with Node.js prior to version 6.4.0, both\ncan be specified.
Type: Documentation-only
\nThe internal path._makeLong()
was not intended for public use. However,\nuserland modules have found it useful. The internal API is deprecated\nand replaced with an identical, public path.toNamespacedPath()
method.
Type: Runtime
\nfs.truncate()
fs.truncateSync()
usage with a file descriptor is\ndeprecated. Please use fs.ftruncate()
or fs.ftruncateSync()
to work with\nfile descriptors.
Type: End-of-Life
\nREPLServer.prototype.memory()
is only necessary for the internal mechanics of\nthe REPLServer
itself. Do not use this function.
Type: End-of-Life.
\nThe ecdhCurve
option to tls.createSecureContext()
and tls.TLSSocket
could\nbe set to false
to disable ECDH entirely on the server only. This mode was\ndeprecated in preparation for migrating to OpenSSL 1.1.0 and consistency with\nthe client and is now unsupported. Use the ciphers
parameter instead.
Type: End-of-Life
\nSince Node.js versions 4.4.0 and 5.2.0, several modules only intended for\ninternal usage were mistakenly exposed to user code through require()
. These\nmodules were:
v8/tools/codemap
v8/tools/consarray
v8/tools/csvparser
v8/tools/logreader
v8/tools/profile_view
v8/tools/profile
v8/tools/SourceMap
v8/tools/splaytree
v8/tools/tickprocessor-driver
v8/tools/tickprocessor
node-inspect/lib/_inspect
(from 7.6.0)node-inspect/lib/internal/inspect_client
(from 7.6.0)node-inspect/lib/internal/inspect_repl
(from 7.6.0)The v8/*
modules do not have any exports, and if not imported in a specific\norder would in fact throw errors. As such there are virtually no legitimate use\ncases for importing them through require()
.
On the other hand, node-inspect
can be installed locally through a package\nmanager, as it is published on the npm registry under the same name. No source\ncode modification is necessary if that is done.
Type: End-of-Life
\nThe AsyncHooks sensitive API was never documented and had various minor issues.\nUse the AsyncResource
API instead. See\nhttps://github.com/nodejs/node/issues/15572.
Type: End-of-Life
\nrunInAsyncIdScope
doesn't emit the 'before'
or 'after'
event and can thus\ncause a lot of issues. See https://github.com/nodejs/node/issues/14328.
Type: Deprecation revoked
\nImporting assert directly was not recommended as the exposed functions use\nloose equality checks. The deprecation was revoked because use of the\nnode:assert
module is not discouraged, and the deprecation caused developer\nconfusion.
Type: End-of-Life
\nNode.js used to support all GCM authentication tag lengths which are accepted by\nOpenSSL when calling decipher.setAuthTag()
. Beginning with Node.js\nv11.0.0, only authentication tag lengths of 128, 120, 112, 104, 96, 64, and 32\nbits are allowed. Authentication tags of other lengths are invalid per\nNIST SP 800-38D.
Type: End-of-Life
\nThe crypto.DEFAULT_ENCODING
property only existed for compatibility with\nNode.js releases prior to versions 0.9.3 and has been removed.
Type: Documentation-only
\nAssigning properties to the top-level this
as an alternative\nto module.exports
is deprecated. Developers should use exports
\nor module.exports
instead.
Type: Documentation-only
\nThe crypto.fips
property is deprecated. Please use crypto.setFips()
\nand crypto.getFips()
instead.
Type: Runtime
\nUsing assert.fail()
with more than one argument is deprecated. Use\nassert.fail()
with only one argument or use a different node:assert
module\nmethod.
Type: Runtime
\ntimers.enroll()
is deprecated. Please use the publicly documented\nsetTimeout()
or setInterval()
instead.
Type: Runtime
\ntimers.unenroll()
is deprecated. Please use the publicly documented\nclearTimeout()
or clearInterval()
instead.
Type: Runtime
\nUsers of MakeCallback
that add the domain
property to carry context,\nshould start using the async_context
variant of MakeCallback
or\nCallbackScope
, or the high-level AsyncResource
class.
Type: End-of-Life
\nThe embedded API provided by AsyncHooks exposes .emitBefore()
and\n.emitAfter()
methods which are very easy to use incorrectly which can lead\nto unrecoverable errors.
Use asyncResource.runInAsyncScope()
API instead which provides a much\nsafer, and more convenient, alternative. See\nhttps://github.com/nodejs/node/pull/18513.
Type: Compile-time
\nCertain versions of node::MakeCallback
APIs available to native addons are\ndeprecated. Please use the versions of the API that accept an async_context
\nparameter.
Type: Runtime
\nprocess.assert()
is deprecated. Please use the assert
module instead.
This was never a documented feature.
", "type": "module", "displayName": "DEP0100: `process.assert()`" }, { "textRaw": "DEP0101: `--with-lttng`", "name": "dep0101:_`--with-lttng`", "meta": { "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/18982", "description": "End-of-Life." } ] }, "desc": "Type: End-of-Life
\nThe --with-lttng
compile-time option has been removed.
Type: End-of-Life
\nUsing the noAssert
argument has no functionality anymore. All input is\nverified regardless of the value of noAssert
. Skipping the verification\ncould lead to hard-to-find errors and crashes.
Type: Documentation-only (supports --pending-deprecation
)
Using process.binding()
in general should be avoided. The type checking\nmethods in particular can be replaced by using util.types
.
This deprecation has been superseded by the deprecation of the\nprocess.binding()
API (DEP0111).
Type: Documentation-only (supports --pending-deprecation
)
When assigning a non-string property to process.env
, the assigned value is\nimplicitly converted to a string. This behavior is deprecated if the assigned\nvalue is not a string, boolean, or number. In the future, such assignment might\nresult in a thrown error. Please convert the property to a string before\nassigning it to process.env
.
Type: End-of-Life
\ndecipher.finaltol()
has never been documented and was an alias for\ndecipher.final()
. This API has been removed, and it is recommended to use\ndecipher.final()
instead.
Type: Runtime
\nUsing crypto.createCipher()
and crypto.createDecipher()
must be\navoided as they use a weak key derivation function (MD5 with no salt) and static\ninitialization vectors. It is recommended to derive a key using\ncrypto.pbkdf2()
or crypto.scrypt()
with random salts and to use\ncrypto.createCipheriv()
and crypto.createDecipheriv()
to obtain the\nCipher
and Decipher
objects respectively.
Type: End-of-Life
\nThis was an undocumented helper function not intended for use outside Node.js\ncore and obsoleted by the removal of NPN (Next Protocol Negotiation) support.
", "type": "module", "displayName": "DEP0107: `tls.convertNPNProtocols()`" }, { "textRaw": "DEP0108: `zlib.bytesRead`", "name": "dep0108:_`zlib.bytesread`", "meta": { "changes": [ { "version": "v11.0.0", "pr-url": "https://github.com/nodejs/node/pull/23308", "description": "Runtime deprecation." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/19414", "description": "Documentation-only deprecation." } ] }, "desc": "Type: Runtime
\nDeprecated alias for zlib.bytesWritten
. This original name was chosen\nbecause it also made sense to interpret the value as the number of bytes\nread by the engine, but is inconsistent with other streams in Node.js that\nexpose values under these names.
Type: End-of-Life
\nSome previously supported (but strictly invalid) URLs were accepted through the\nhttp.request()
, http.get()
, https.request()
,\nhttps.get()
, and tls.checkServerIdentity()
APIs because those were\naccepted by the legacy url.parse()
API. The mentioned APIs now use the WHATWG\nURL parser that requires strictly valid URLs. Passing an invalid URL is\ndeprecated and support will be removed in the future.
Type: Documentation-only
\nThe produceCachedData
option is deprecated. Use\nscript.createCachedData()
instead.
Type: Documentation-only (supports --pending-deprecation
)
process.binding()
is for use by Node.js internal code only.
While process.binding()
has not reached End-of-Life status in general, it is\nunavailable when policies or the permission model are enabled.
Type: Runtime
\nThe node:dgram
module previously contained several APIs that were never meant\nto accessed outside of Node.js core: Socket.prototype._handle
,\nSocket.prototype._receiving
, Socket.prototype._bindState
,\nSocket.prototype._queue
, Socket.prototype._reuseAddr
,\nSocket.prototype._healthCheck()
, Socket.prototype._stopReceiving()
, and\ndgram._createSocketHandle()
.
Type: End-of-Life
\nCipher.setAuthTag()
and Decipher.getAuthTag()
are no longer available. They\nwere never documented and would throw when called.
Type: End-of-Life
\nThe crypto._toBuf()
function was not designed to be used by modules outside\nof Node.js core and was removed.
Type: Documentation-only (supports --pending-deprecation
)
In recent versions of Node.js, there is no difference between\ncrypto.randomBytes()
and crypto.pseudoRandomBytes()
. The latter is\ndeprecated along with the undocumented aliases crypto.prng()
and\ncrypto.rng()
in favor of crypto.randomBytes()
and might be removed in a\nfuture release.
Type: Deprecation revoked
\nThe legacy URL API is deprecated. This includes url.format()
,\nurl.parse()
, url.resolve()
, and the legacy urlObject
. Please\nuse the WHATWG URL API instead.
Type: End-of-Life
\nPrevious versions of Node.js exposed handles to internal native objects through\nthe _handle
property of the Cipher
, Decipher
, DiffieHellman
,\nDiffieHellmanGroup
, ECDH
, Hash
, Hmac
, Sign
, and Verify
classes.\nThe _handle
property has been removed because improper use of the native\nobject can lead to crashing the application.
Type: Runtime
\nPrevious versions of Node.js supported dns.lookup()
with a falsy host name\nlike dns.lookup(false)
due to backward compatibility.\nThis behavior is undocumented and is thought to be unused in real world apps.\nIt will become an error in future versions of Node.js.
Type: Documentation-only (supports --pending-deprecation
)
process.binding('uv').errname()
is deprecated. Please use\nutil.getSystemErrorName()
instead.
Type: End-of-Life
\nWindows Performance Counter support has been removed from Node.js. The\nundocumented COUNTER_NET_SERVER_CONNECTION()
,\nCOUNTER_NET_SERVER_CONNECTION_CLOSE()
, COUNTER_HTTP_SERVER_REQUEST()
,\nCOUNTER_HTTP_SERVER_RESPONSE()
, COUNTER_HTTP_CLIENT_REQUEST()
, and\nCOUNTER_HTTP_CLIENT_RESPONSE()
functions have been deprecated.
Type: Runtime
\nThe undocumented net._setSimultaneousAccepts()
function was originally\nintended for debugging and performance tuning when using the\nnode:child_process
and node:cluster
modules on Windows. The function is not\ngenerally useful and is being removed. See discussion here:\nhttps://github.com/nodejs/node/issues/18391
Type: Runtime
\nPlease use Server.prototype.setSecureContext()
instead.
Type: Runtime
\nSetting the TLS ServerName to an IP address is not permitted by\nRFC 6066. This will be ignored in a future version.
", "type": "module", "displayName": "DEP0123: setting the TLS ServerName to an IP address" }, { "textRaw": "DEP0124: using `REPLServer.rli`", "name": "dep0124:_using_`replserver.rli`", "meta": { "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/33286", "description": "End-of-Life." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26260", "description": "Runtime deprecation." } ] }, "desc": "Type: End-of-Life
\nThis property is a reference to the instance itself.
", "type": "module", "displayName": "DEP0124: using `REPLServer.rli`" }, { "textRaw": "DEP0125: `require('node:_stream_wrap')`", "name": "dep0125:_`require('node:_stream_wrap')`", "meta": { "changes": [ { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26245", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nThe node:_stream_wrap
module is deprecated.
Type: Runtime
\nThe previously undocumented timers.active()
is deprecated.\nPlease use the publicly documented timeout.refresh()
instead.\nIf re-referencing the timeout is necessary, timeout.ref()
can be used\nwith no performance impact since Node.js 10.
Type: Runtime
\nThe previously undocumented and \"private\" timers._unrefActive()
is deprecated.\nPlease use the publicly documented timeout.refresh()
instead.\nIf unreferencing the timeout is necessary, timeout.unref()
can be used\nwith no performance impact since Node.js 10.
Type: Runtime
\nModules that have an invalid main
entry (e.g., ./does-not-exist.js
) and\nalso have an index.js
file in the top level directory will resolve the\nindex.js
file. That is deprecated and is going to throw an error in future\nNode.js versions.
Type: Runtime
\nThe _channel
property of child process objects returned by spawn()
and\nsimilar functions is not intended for public use. Use ChildProcess.channel
\ninstead.
Type: End-of-Life
\nUse module.createRequire()
instead.
Type: End-of-Life
\nThe legacy HTTP parser, used by default in versions of Node.js prior to 12.0.0,\nis deprecated and has been removed in v13.0.0. Prior to v13.0.0, the\n--http-parser=legacy
command-line flag could be used to revert to using the\nlegacy parser.
Type: Runtime
\nPassing a callback to worker.terminate()
is deprecated. Use the returned\nPromise
instead, or a listener to the worker's 'exit'
event.
Type: Documentation-only
\nPrefer response.socket
over response.connection
and\nrequest.socket
over request.connection
.
Type: Documentation-only (supports --pending-deprecation
)
The process._tickCallback
property was never documented as\nan officially supported API.
Type: Runtime
\nWriteStream.open()
and ReadStream.open()
are undocumented internal\nAPIs that do not make sense to use in userland. File streams should always be\nopened through their corresponding factory methods fs.createWriteStream()
\nand fs.createReadStream()
) or by passing a file descriptor in options.
Type: Documentation-only
\nresponse.finished
indicates whether response.end()
has been\ncalled, not whether 'finish'
has been emitted and the underlying data\nis flushed.
Use response.writableFinished
or response.writableEnded
\naccordingly instead to avoid the ambiguity.
To maintain existing behavior response.finished
should be replaced with\nresponse.writableEnded
.
Type: Runtime
\nAllowing a fs.FileHandle
object to be closed on garbage collection is\ndeprecated. In the future, doing so might result in a thrown error that will\nterminate the process.
Please ensure that all fs.FileHandle
objects are explicitly closed using\nFileHandle.prototype.close()
when the fs.FileHandle
is no longer needed:
const fsPromises = require('node:fs').promises;\nasync function openAndClose() {\n let filehandle;\n try {\n filehandle = await fsPromises.open('thefile.txt', 'r');\n } finally {\n if (filehandle !== undefined)\n await filehandle.close();\n }\n}\n
",
"type": "module",
"displayName": "DEP0137: Closing fs.FileHandle on garbage collection"
},
{
"textRaw": "DEP0138: `process.mainModule`",
"name": "dep0138:_`process.mainmodule`",
"meta": {
"changes": [
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/32232",
"description": "Documentation-only deprecation."
}
]
},
"desc": "Type: Documentation-only
\nprocess.mainModule
is a CommonJS-only feature while process
global\nobject is shared with non-CommonJS environment. Its use within ECMAScript\nmodules is unsupported.
It is deprecated in favor of require.main
, because it serves the same\npurpose and is only available on CommonJS environment.
Type: Documentation-only
\nCalling process.umask()
with no argument causes the process-wide umask to be\nwritten twice. This introduces a race condition between threads, and is a\npotential security vulnerability. There is no safe, cross-platform alternative\nAPI.
Type: Documentation-only
\nUse request.destroy()
instead of request.abort()
.
Type: Documentation-only (supports --pending-deprecation
)
The node:repl
module exported the input and output stream twice. Use .input
\ninstead of .inputStream
and .output
instead of .outputStream
.
Type: Documentation-only
\nThe node:repl
module exports a _builtinLibs
property that contains an array\nof built-in modules. It was incomplete so far and instead it's better to rely\nupon require('node:module').builtinModules
.
Type: Runtime\nTransform._transformState
will be removed in future versions where it is\nno longer required due to simplification of the implementation.
Type: Documentation-only (supports --pending-deprecation
)
A CommonJS module can access the first module that required it using\nmodule.parent
. This feature is deprecated because it does not work\nconsistently in the presence of ECMAScript modules and because it gives an\ninaccurate representation of the CommonJS module graph.
Some modules use it to check if they are the entry point of the current process.\nInstead, it is recommended to compare require.main
and module
:
if (require.main === module) {\n // Code section that will run only if current file is the entry point.\n}\n
\nWhen looking for the CommonJS modules that have required the current one,\nrequire.cache
and module.children
can be used:
const moduleParents = Object.values(require.cache)\n .filter((m) => m.children.includes(module));\n
",
"type": "module",
"displayName": "DEP0144: `module.parent`"
},
{
"textRaw": "DEP0145: `socket.bufferSize`",
"name": "dep0145:_`socket.buffersize`",
"meta": {
"changes": [
{
"version": "v14.6.0",
"pr-url": "https://github.com/nodejs/node/pull/34088",
"description": "Documentation-only deprecation."
}
]
},
"desc": "Type: Documentation-only
\nsocket.bufferSize
is just an alias for writable.writableLength
.
Type: Documentation-only
\nThe crypto.Certificate()
constructor is deprecated. Use\nstatic methods of crypto.Certificate()
instead.
Type: Runtime
\nIn future versions of Node.js, recursive
option will be ignored for\nfs.rmdir
, fs.rmdirSync
, and fs.promises.rmdir
.
Use fs.rm(path, { recursive: true, force: true })
,\nfs.rmSync(path, { recursive: true, force: true })
or\nfs.promises.rm(path, { recursive: true, force: true })
instead.
Type: Runtime
\nUsing a trailing \"/\"
to define subpath folder mappings in the\nsubpath exports or subpath imports fields is deprecated. Use\nsubpath patterns instead.
Type: Documentation-only.
\nPrefer message.socket
over message.connection
.
Type: End-of-Life
\nThe process.config
property provides access to Node.js compile-time settings.\nHowever, the property is mutable and therefore subject to tampering. The ability\nto change the value will be removed in a future version of Node.js.
Type: Runtime
\nPreviously, index.js
and extension searching lookups would apply to\nimport 'pkg'
main entry point resolution, even when resolving ES modules.
With this deprecation, all ES module main entry point resolutions require\nan explicit \"exports\"
or \"main\"
entry with the exact file extension.
Type: Runtime
\nThe 'gc'
, 'http2'
, and 'http'
<PerformanceEntry> object types have\nadditional properties assigned to them that provide additional information.\nThese properties are now available within the standard detail
property\nof the PerformanceEntry
object. The existing accessors have been\ndeprecated and should no longer be used.
Type: End-of-Life
\nUsing a non-nullish non-integer value for family
option, a non-nullish\nnon-number value for hints
option, a non-nullish non-boolean value for all
\noption, or a non-nullish non-boolean value for verbatim
option in\ndns.lookup()
and dnsPromises.lookup()
throws an\nERR_INVALID_ARG_TYPE
error.
Type: Runtime
\nThe 'hash'
and 'mgf1Hash'
options are replaced with 'hashAlgorithm'
\nand 'mgf1HashAlgorithm'
.
Type: Runtime
\nThe remapping of specifiers ending in \"/\"
like import 'pkg/x/'
is deprecated\nfor package \"exports\"
and \"imports\"
pattern resolutions.
Type: Documentation-only
\nMove to <Stream> API instead, as the http.ClientRequest
,\nhttp.ServerResponse
, and http.IncomingMessage
are all stream-based.\nCheck stream.destroyed
instead of the .aborted
property, and listen for\n'close'
instead of 'abort'
, 'aborted'
event.
The .aborted
property and 'abort'
event are only useful for detecting\n.abort()
calls. For closing a request early, use the Stream\n.destroy([error])
then check the .destroyed
property and 'close'
event\nshould have the same effect. The receiving end should also check the\nreadable.readableEnded
value on http.IncomingMessage
to get whether\nit was an aborted or graceful destroy.
Type: End-of-Life
\nAn undocumented feature of Node.js streams was to support thenables in\nimplementation methods. This is now deprecated, use callbacks instead and avoid\nuse of async function for streams implementation methods.
\nThis feature caused users to encounter unexpected problems where the user\nimplements the function in callback style but uses e.g. an async method which\nwould cause an error since mixing promise and callback semantics is not valid.
\nconst w = new Writable({\n async final(callback) {\n await someOp();\n callback();\n },\n});\n
",
"type": "module",
"displayName": "DEP0157: Thenable support in streams"
},
{
"textRaw": "DEP0158: `buffer.slice(start, end)`",
"name": "dep0158:_`buffer.slice(start,_end)`",
"meta": {
"changes": [
{
"version": [
"v17.5.0",
"v16.15.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41596",
"description": "Documentation-only deprecation."
}
]
},
"desc": "Type: Documentation-only
\nThis method was deprecated because it is not compatible with\nUint8Array.prototype.slice()
, which is a superclass of Buffer
.
Use buffer.subarray
which does the same thing instead.
Type: End-of-Life
\nThis error code was removed due to adding more confusion to\nthe errors used for value type validation.
", "type": "module", "displayName": "DEP0159: `ERR_INVALID_CALLBACK`" }, { "textRaw": "DEP0160: `process.on('multipleResolves', handler)`", "name": "dep0160:_`process.on('multipleresolves',_handler)`", "meta": { "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41896", "description": "Runtime deprecation." }, { "version": [ "v17.6.0", "v16.15.0" ], "pr-url": "https://github.com/nodejs/node/pull/41872", "description": "Documentation-only deprecation." } ] }, "desc": "Type: Runtime.
\nThis event was deprecated because it did not work with V8 promise combinators\nwhich diminished its usefulness.
", "type": "module", "displayName": "DEP0160: `process.on('multipleResolves', handler)`" }, { "textRaw": "DEP0161: `process._getActiveRequests()` and `process._getActiveHandles()`", "name": "dep0161:_`process._getactiverequests()`_and_`process._getactivehandles()`", "meta": { "changes": [ { "version": [ "v17.6.0", "v16.15.0" ], "pr-url": "https://github.com/nodejs/node/pull/41587", "description": "Documentation-only deprecation." } ] }, "desc": "Type: Documentation-only
\nThe process._getActiveHandles()
and process._getActiveRequests()
\nfunctions are not intended for public use and can be removed in future\nreleases.
Use process.getActiveResourcesInfo()
to get a list of types of active\nresources and not the actual references.
Type: End-of-Life
\nImplicit coercion of objects with own toString
property, passed as second\nparameter in fs.write()
, fs.writeFile()
, fs.appendFile()
,\nfs.writeFileSync()
, and fs.appendFileSync()
is deprecated.\nConvert them to primitive strings.
Type: Documentation-only
\nThese methods were deprecated because they can be used in a way which does not\nhold the channel reference alive long enough to receive the events.
\nUse diagnostics_channel.subscribe(name, onMessage)
or\ndiagnostics_channel.unsubscribe(name, onMessage)
which does the same\nthing instead.
Type: End-of-Life
\nValues other than undefined
, null
, integer numbers, and integer strings\n(e.g., '1'
) are deprecated as value for the code
parameter in\nprocess.exit()
and as value to assign to process.exitCode
.
Type: Documentation-only
\nThe --trace-atomics-wait
flag is deprecated.
Type: Runtime
\nPackage imports and exports targets mapping into paths including a double slash\n(of \"/\" or \"\\\") are deprecated and will fail with a resolution validation\nerror in a future release. This same deprecation also applies to pattern matches\nstarting or ending in a slash.
", "type": "module", "displayName": "DEP0166: Double slashes in imports and exports targets" }, { "textRaw": "DEP0167: Weak `DiffieHellmanGroup` instances (`modp1`, `modp2`, `modp5`)", "name": "dep0167:_weak_`diffiehellmangroup`_instances_(`modp1`,_`modp2`,_`modp5`)", "meta": { "changes": [ { "version": [ "v18.10.0", "v16.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/44588", "description": "Documentation-only deprecation." } ] }, "desc": "Type: Documentation-only
\nThe well-known MODP groups modp1
, modp2
, and modp5
are deprecated because\nthey are not secure against practical attacks. See RFC 8247 Section 2.4 for\ndetails.
These groups might be removed in future versions of Node.js. Applications that\nrely on these groups should evaluate using stronger MODP groups instead.
", "type": "module", "displayName": "DEP0167: Weak `DiffieHellmanGroup` instances (`modp1`, `modp2`, `modp5`)" }, { "textRaw": "DEP0168: Unhandled exception in Node-API callbacks", "name": "dep0168:_unhandled_exception_in_node-api_callbacks", "meta": { "changes": [ { "version": [ "v18.3.0", "v16.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/36510", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nThe implicit suppression of uncaught exceptions in Node-API callbacks is now\ndeprecated.
\nSet the flag --force-node-api-uncaught-exceptions-policy
to force Node.js\nto emit an 'uncaughtException'
event if the exception is not handled in\nNode-API callbacks.
Type: Documentation-only (supports --pending-deprecation
)
url.parse()
behavior is not standardized and prone to errors that\nhave security implications. Use the WHATWG URL API instead. CVEs are not\nissued for url.parse()
vulnerabilities.
Type: Runtime
\nurl.parse()
accepts URLs with ports that are not numbers. This behavior\nmight result in host name spoofing with unexpected input. These URLs will throw\nan error in future versions of Node.js, as the WHATWG URL API does already.
Type: Documentation-only
\nIn a future version of Node.js, message.headers
,\nmessage.headersDistinct
, message.trailers
, and\nmessage.trailersDistinct
will be read-only.
Type: Runtime
\nIn a future version of Node.js, the asyncResource
property will no longer\nbe added when a function is bound to an AsyncResource
.
Type: Documentation-only
\nIn a future version of Node.js, assert.CallTracker
,\nwill be removed.\nConsider using alternatives such as the mock
helper function.
Type: Runtime
\nCalling util.promisify
on a function that returns a
Type: Documentation-only
\nThe util.toUSVString()
API is deprecated. Please use\nString.prototype.toWellFormed
instead.
Type: Documentation-only
\nF_OK
, R_OK
, W_OK
and X_OK
getters exposed directly on node:fs
are\ndeprecated. Get them from fs.constants
or fs.promises.constants
instead.
Type: End-of-Life
\nThe util.types.isWebAssemblyCompiledModule
API has been removed.\nPlease use value instanceof WebAssembly.Module
instead.
Type: Documentation-only
\nThe dirent.path
is deprecated due to its lack of consistency across\nrelease lines. Please use dirent.parentPath
instead.
Type: Documentation-only
\nCalling Hash
class directly with Hash()
or new Hash()
is\ndeprecated due to being internals, not intended for public use.\nPlease use the crypto.createHash()
method to create Hash instances.
Applications running in Node.js will generally experience four categories of\nerrors:
\nAssertionError
s are a special class of error that can be triggered when\nNode.js detects an exceptional logic violation that should never occur. These\nare raised typically by the node:assert
module.All JavaScript and system errors raised by Node.js inherit from, or are\ninstances of, the standard JavaScript <Error> class and are guaranteed\nto provide at least the properties available on that class.
", "miscs": [ { "textRaw": "Error propagation and interception", "name": "Error propagation and interception", "type": "misc", "desc": "Node.js supports several mechanisms for propagating and handling errors that\noccur while an application is running. How these errors are reported and\nhandled depends entirely on the type of Error
and the style of the API that is\ncalled.
All JavaScript errors are handled as exceptions that immediately generate\nand throw an error using the standard JavaScript throw
mechanism. These\nare handled using the try…catch
construct provided by the\nJavaScript language.
// Throws with a ReferenceError because z is not defined.\ntry {\n const m = 1;\n const n = m + z;\n} catch (err) {\n // Handle the error here.\n}\n
\nAny use of the JavaScript throw
mechanism will raise an exception that\nmust be handled or the Node.js process will exit immediately.
With few exceptions, Synchronous APIs (any blocking method that does not\nreturn a <Promise> nor accept a callback
function, such as\nfs.readFileSync
), will use throw
to report errors.
Errors that occur within Asynchronous APIs may be reported in multiple ways:
\nSome asynchronous methods returns a <Promise>, you should always take into\naccount that it might be rejected. See --unhandled-rejections
flag for\nhow the process will react to an unhandled promise rejection.
const fs = require('fs/promises');\n\n(async () => {\n let data;\n try {\n data = await fs.readFile('a file that does not exist');\n } catch (err) {\n console.error('There was an error reading the file!', err);\n return;\n }\n // Otherwise handle the data\n})();\n
\nMost asynchronous methods that accept a callback
function will accept an\nError
object passed as the first argument to that function. If that first\nargument is not null
and is an instance of Error
, then an error occurred\nthat should be handled.
const fs = require('node:fs');\nfs.readFile('a file that does not exist', (err, data) => {\n if (err) {\n console.error('There was an error reading the file!', err);\n return;\n }\n // Otherwise handle the data\n});\n
\nWhen an asynchronous method is called on an object that is an\nEventEmitter
, errors can be routed to that object's 'error'
event.
const net = require('node:net');\nconst connection = net.connect('localhost');\n\n// Adding an 'error' event handler to a stream:\nconnection.on('error', (err) => {\n // If the connection is reset by the server, or if it can't\n // connect at all, or on any sort of error encountered by\n // the connection, the error will be sent here.\n console.error(err);\n});\n\nconnection.pipe(process.stdout);\n
\nA handful of typically asynchronous methods in the Node.js API may still\nuse the throw
mechanism to raise exceptions that must be handled using\ntry…catch
. There is no comprehensive list of such methods; please\nrefer to the documentation of each method to determine the appropriate\nerror handling mechanism required.
The use of the 'error'
event mechanism is most common for stream-based\nand event emitter-based APIs, which themselves represent a series of\nasynchronous operations over time (as opposed to a single operation that may\npass or fail).
For all EventEmitter
objects, if an 'error'
event handler is not\nprovided, the error will be thrown, causing the Node.js process to report an\nuncaught exception and crash unless either: a handler has been registered for\nthe 'uncaughtException'
event, or the deprecated node:domain
\nmodule is used.
const EventEmitter = require('node:events');\nconst ee = new EventEmitter();\n\nsetImmediate(() => {\n // This will crash the process because no 'error' event\n // handler has been added.\n ee.emit('error', new Error('This will crash'));\n});\n
\nErrors generated in this way cannot be intercepted using try…catch
as\nthey are thrown after the calling code has already exited.
Developers must refer to the documentation for each method to determine\nexactly how errors raised by those methods are propagated.
" }, { "textRaw": "Exceptions vs. errors", "name": "Exceptions vs. errors", "type": "misc", "desc": "A JavaScript exception is a value that is thrown as a result of an invalid\noperation or as the target of a throw
statement. While it is not required\nthat these values are instances of Error
or classes which inherit from\nError
, all exceptions thrown by Node.js or the JavaScript runtime will be\ninstances of Error
.
Some exceptions are unrecoverable at the JavaScript layer. Such exceptions\nwill always cause the Node.js process to crash. Examples include assert()
\nchecks or abort()
calls in the C++ layer.
Errors originating in crypto
or tls
are of class Error
, and in addition to\nthe standard .code
and .message
properties, may have some additional\nOpenSSL-specific properties.
An array of errors that can give context to where in the OpenSSL library an\nerror originates from.
" }, { "textRaw": "`error.function`", "name": "function", "desc": "The OpenSSL function the error originates in.
" }, { "textRaw": "`error.library`", "name": "library", "desc": "The OpenSSL library the error originates in.
" }, { "textRaw": "`error.reason`", "name": "reason", "desc": "A human-readable string describing the reason for the error.
\n" } ], "type": "misc", "displayName": "OpenSSL errors" }, { "textRaw": "Node.js error codes", "name": "node.js_error_codes", "desc": "", "modules": [ { "textRaw": "`ABORT_ERR`", "name": "`abort_err`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Used when an operation has been aborted (typically using an AbortController
).
APIs not using AbortSignal
s typically do not raise an error with this code.
This code does not use the regular ERR_*
convention Node.js errors use in\norder to be compatible with the web platform's AbortError
.
A special type of error that is triggered whenever Node.js tries to get access\nto a resource restricted by the Permission Model.
\n", "type": "module", "displayName": "`ERR_ACCESS_DENIED`" }, { "textRaw": "`ERR_AMBIGUOUS_ARGUMENT`", "name": "`err_ambiguous_argument`", "desc": "A function argument is being used in a way that suggests that the function\nsignature may be misunderstood. This is thrown by the node:assert
module when\nthe message
parameter in assert.throws(block, message)
matches the error\nmessage thrown by block
because that usage suggests that the user believes\nmessage
is the expected message rather than the message the AssertionError
\nwill display if block
does not throw.
An iterable argument (i.e. a value that works with for...of
loops) was\nrequired, but not provided to a Node.js API.
A special type of error that can be triggered whenever Node.js detects an\nexceptional logic violation that should never occur. These are raised typically\nby the node:assert
module.
An attempt was made to register something that is not a function as an\nAsyncHooks
callback.
The type of an asynchronous resource was invalid. Users are also able\nto define their own types if using the public embedder API.
\n", "type": "module", "displayName": "`ERR_ASYNC_TYPE`" }, { "textRaw": "`ERR_BROTLI_COMPRESSION_FAILED`", "name": "`err_brotli_compression_failed`", "desc": "Data passed to a Brotli stream was not successfully compressed.
\n", "type": "module", "displayName": "`ERR_BROTLI_COMPRESSION_FAILED`" }, { "textRaw": "`ERR_BROTLI_INVALID_PARAM`", "name": "`err_brotli_invalid_param`", "desc": "An invalid parameter key was passed during construction of a Brotli stream.
\n", "type": "module", "displayName": "`ERR_BROTLI_INVALID_PARAM`" }, { "textRaw": "`ERR_BUFFER_CONTEXT_NOT_AVAILABLE`", "name": "`err_buffer_context_not_available`", "desc": "An attempt was made to create a Node.js Buffer
instance from addon or embedder\ncode, while in a JS engine Context that is not associated with a Node.js\ninstance. The data passed to the Buffer
method will have been released\nby the time the method returns.
When encountering this error, a possible alternative to creating a Buffer
\ninstance is to create a normal Uint8Array
, which only differs in the\nprototype of the resulting object. Uint8Array
s are generally accepted in all\nNode.js core APIs where Buffer
s are; they are available in all Contexts.
An operation outside the bounds of a Buffer
was attempted.
An attempt has been made to create a Buffer
larger than the maximum allowed\nsize.
Node.js was unable to watch for the SIGINT
signal.
A child process was closed before the parent received a reply.
\n", "type": "module", "displayName": "`ERR_CHILD_CLOSED_BEFORE_REPLY`" }, { "textRaw": "`ERR_CHILD_PROCESS_IPC_REQUIRED`", "name": "`err_child_process_ipc_required`", "desc": "Used when a child process is being forked without specifying an IPC channel.
\n", "type": "module", "displayName": "`ERR_CHILD_PROCESS_IPC_REQUIRED`" }, { "textRaw": "`ERR_CHILD_PROCESS_STDIO_MAXBUFFER`", "name": "`err_child_process_stdio_maxbuffer`", "desc": "Used when the main process is trying to read data from the child process's\nSTDERR/STDOUT, and the data's length is longer than the maxBuffer
option.
There was an attempt to use a MessagePort
instance in a closed\nstate, usually after .close()
has been called.
Console
was instantiated without stdout
stream, or Console
has a\nnon-writable stdout
or stderr
stream.
A class constructor was called that is not callable.
\n", "type": "module", "displayName": "`ERR_CONSTRUCT_CALL_INVALID`" }, { "textRaw": "`ERR_CONSTRUCT_CALL_REQUIRED`", "name": "`err_construct_call_required`", "desc": "A constructor for a class was called without new
.
The vm context passed into the API is not yet initialized. This could happen\nwhen an error occurs (and is caught) during the creation of the\ncontext, for example, when the allocation fails or the maximum call stack\nsize is reached when the context is created.
\n", "type": "module", "displayName": "`ERR_CONTEXT_NOT_INITIALIZED`" }, { "textRaw": "`ERR_CRYPTO_CUSTOM_ENGINE_NOT_SUPPORTED`", "name": "`err_crypto_custom_engine_not_supported`", "desc": "An OpenSSL engine was requested (for example, through the clientCertEngine
or\nprivateKeyEngine
TLS options) that is not supported by the version of OpenSSL\nbeing used, likely due to the compile-time flag OPENSSL_NO_ENGINE
.
An invalid value for the format
argument was passed to the crypto.ECDH()
\nclass getPublicKey()
method.
An invalid value for the key
argument has been passed to the\ncrypto.ECDH()
class computeSecret()
method. It means that the public\nkey lies outside of the elliptic curve.
An invalid crypto engine identifier was passed to\nrequire('node:crypto').setEngine()
.
The --force-fips
command-line argument was used but there was an attempt\nto enable or disable FIPS mode in the node:crypto
module.
An attempt was made to enable or disable FIPS mode, but FIPS mode was not\navailable.
\n", "type": "module", "displayName": "`ERR_CRYPTO_FIPS_UNAVAILABLE`" }, { "textRaw": "`ERR_CRYPTO_HASH_FINALIZED`", "name": "`err_crypto_hash_finalized`", "desc": "hash.digest()
was called multiple times. The hash.digest()
method must\nbe called no more than one time per instance of a Hash
object.
hash.update()
failed for any reason. This should rarely, if ever, happen.
The given crypto keys are incompatible with the attempted operation.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INCOMPATIBLE_KEY`" }, { "textRaw": "`ERR_CRYPTO_INCOMPATIBLE_KEY_OPTIONS`", "name": "`err_crypto_incompatible_key_options`", "desc": "The selected public or private key encoding is incompatible with other options.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INCOMPATIBLE_KEY_OPTIONS`" }, { "textRaw": "`ERR_CRYPTO_INITIALIZATION_FAILED`", "name": "`err_crypto_initialization_failed`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Initialization of the crypto subsystem failed.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INITIALIZATION_FAILED`" }, { "textRaw": "`ERR_CRYPTO_INVALID_AUTH_TAG`", "name": "`err_crypto_invalid_auth_tag`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid authentication tag was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_AUTH_TAG`" }, { "textRaw": "`ERR_CRYPTO_INVALID_COUNTER`", "name": "`err_crypto_invalid_counter`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid counter was provided for a counter-mode cipher.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_COUNTER`" }, { "textRaw": "`ERR_CRYPTO_INVALID_CURVE`", "name": "`err_crypto_invalid_curve`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid elliptic-curve was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_CURVE`" }, { "textRaw": "`ERR_CRYPTO_INVALID_DIGEST`", "name": "`err_crypto_invalid_digest`", "desc": "An invalid crypto digest algorithm was specified.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_DIGEST`" }, { "textRaw": "`ERR_CRYPTO_INVALID_IV`", "name": "`err_crypto_invalid_iv`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid initialization vector was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_IV`" }, { "textRaw": "`ERR_CRYPTO_INVALID_JWK`", "name": "`err_crypto_invalid_jwk`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid JSON Web Key was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_JWK`" }, { "textRaw": "`ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE`", "name": "`err_crypto_invalid_key_object_type`", "desc": "The given crypto key object's type is invalid for the attempted operation.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE`" }, { "textRaw": "`ERR_CRYPTO_INVALID_KEYLEN`", "name": "`err_crypto_invalid_keylen`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid key length was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_KEYLEN`" }, { "textRaw": "`ERR_CRYPTO_INVALID_KEYPAIR`", "name": "`err_crypto_invalid_keypair`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid key pair was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_KEYPAIR`" }, { "textRaw": "`ERR_CRYPTO_INVALID_KEYTYPE`", "name": "`err_crypto_invalid_keytype`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid key type was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_KEYTYPE`" }, { "textRaw": "`ERR_CRYPTO_INVALID_MESSAGELEN`", "name": "`err_crypto_invalid_messagelen`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid message length was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_MESSAGELEN`" }, { "textRaw": "`ERR_CRYPTO_INVALID_SCRYPT_PARAMS`", "name": "`err_crypto_invalid_scrypt_params`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Invalid scrypt algorithm parameters were provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_SCRYPT_PARAMS`" }, { "textRaw": "`ERR_CRYPTO_INVALID_STATE`", "name": "`err_crypto_invalid_state`", "desc": "A crypto method was used on an object that was in an invalid state. For\ninstance, calling cipher.getAuthTag()
before calling cipher.final()
.
An invalid authentication tag length was provided.
\n", "type": "module", "displayName": "`ERR_CRYPTO_INVALID_TAG_LENGTH`" }, { "textRaw": "`ERR_CRYPTO_JOB_INIT_FAILED`", "name": "`err_crypto_job_init_failed`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Initialization of an asynchronous crypto operation failed.
\n", "type": "module", "displayName": "`ERR_CRYPTO_JOB_INIT_FAILED`" }, { "textRaw": "`ERR_CRYPTO_JWK_UNSUPPORTED_CURVE`", "name": "`err_crypto_jwk_unsupported_curve`", "desc": "Key's Elliptic Curve is not registered for use in the\nJSON Web Key Elliptic Curve Registry.
\n", "type": "module", "displayName": "`ERR_CRYPTO_JWK_UNSUPPORTED_CURVE`" }, { "textRaw": "`ERR_CRYPTO_JWK_UNSUPPORTED_KEY_TYPE`", "name": "`err_crypto_jwk_unsupported_key_type`", "desc": "Key's Asymmetric Key Type is not registered for use in the\nJSON Web Key Types Registry.
\n", "type": "module", "displayName": "`ERR_CRYPTO_JWK_UNSUPPORTED_KEY_TYPE`" }, { "textRaw": "`ERR_CRYPTO_OPERATION_FAILED`", "name": "`err_crypto_operation_failed`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "A crypto operation failed for an otherwise unspecified reason.
\n", "type": "module", "displayName": "`ERR_CRYPTO_OPERATION_FAILED`" }, { "textRaw": "`ERR_CRYPTO_PBKDF2_ERROR`", "name": "`err_crypto_pbkdf2_error`", "desc": "The PBKDF2 algorithm failed for unspecified reasons. OpenSSL does not provide\nmore details and therefore neither does Node.js.
\n", "type": "module", "displayName": "`ERR_CRYPTO_PBKDF2_ERROR`" }, { "textRaw": "`ERR_CRYPTO_SCRYPT_INVALID_PARAMETER`", "name": "`err_crypto_scrypt_invalid_parameter`", "desc": "One or more crypto.scrypt()
or crypto.scryptSync()
parameters are\noutside their legal range.
Node.js was compiled without scrypt
support. Not possible with the official\nrelease binaries but can happen with custom builds, including distro builds.
A signing key
was not provided to the sign.sign()
method.
crypto.timingSafeEqual()
was called with Buffer
, TypedArray
, or\nDataView
arguments of different lengths.
An unknown cipher was specified.
\n", "type": "module", "displayName": "`ERR_CRYPTO_UNKNOWN_CIPHER`" }, { "textRaw": "`ERR_CRYPTO_UNKNOWN_DH_GROUP`", "name": "`err_crypto_unknown_dh_group`", "desc": "An unknown Diffie-Hellman group name was given. See\ncrypto.getDiffieHellman()
for a list of valid group names.
An attempt to invoke an unsupported crypto operation was made.
\n", "type": "module", "displayName": "`ERR_CRYPTO_UNSUPPORTED_OPERATION`" }, { "textRaw": "`ERR_DEBUGGER_ERROR`", "name": "`err_debugger_error`", "meta": { "added": [ "v16.4.0", "v14.17.4" ], "changes": [] }, "desc": "An error occurred with the debugger.
\n", "type": "module", "displayName": "`ERR_DEBUGGER_ERROR`" }, { "textRaw": "`ERR_DEBUGGER_STARTUP_ERROR`", "name": "`err_debugger_startup_error`", "meta": { "added": [ "v16.4.0", "v14.17.4" ], "changes": [] }, "desc": "The debugger timed out waiting for the required host/port to be free.
\n", "type": "module", "displayName": "`ERR_DEBUGGER_STARTUP_ERROR`" }, { "textRaw": "`ERR_DLOPEN_DISABLED`", "name": "`err_dlopen_disabled`", "meta": { "added": [ "v16.10.0", "v14.19.0" ], "changes": [] }, "desc": "Loading native addons has been disabled using --no-addons
.
A call to process.dlopen()
failed.
The fs.Dir
was previously closed.
A synchronous read or close call was attempted on an fs.Dir
which has\nongoing asynchronous operations.
c-ares
failed to set the DNS server.
The node:domain
module was not usable since it could not establish the\nrequired error handling hooks, because\nprocess.setUncaughtExceptionCaptureCallback()
had been called at an\nearlier point in time.
process.setUncaughtExceptionCaptureCallback()
could not be called\nbecause the node:domain
module has been loaded at an earlier point in time.
The stack trace is extended to include the point in time at which the\nnode:domain
module had been loaded.
v8.startupSnapshot.setDeserializeMainFunction()
could not be called\nbecause it had already been called before.
Data provided to TextDecoder()
API was invalid according to the encoding\nprovided.
Encoding provided to TextDecoder()
API was not one of the\nWHATWG Supported Encodings.
--print
cannot be used with ESM input.
Thrown when an attempt is made to recursively dispatch an event on EventTarget
.
The JS execution context is not associated with a Node.js environment.\nThis may occur when Node.js is used as an embedded library and some hooks\nfor the JS engine are not set up properly.
\n", "type": "module", "displayName": "`ERR_EXECUTION_ENVIRONMENT_NOT_AVAILABLE`" }, { "textRaw": "`ERR_FALSY_VALUE_REJECTION`", "name": "`err_falsy_value_rejection`", "desc": "A Promise
that was callbackified via util.callbackify()
was rejected with a\nfalsy value.
Used when a feature that is not available\nto the current platform which is running Node.js is used.
\n", "type": "module", "displayName": "`ERR_FEATURE_UNAVAILABLE_ON_PLATFORM`" }, { "textRaw": "`ERR_FS_CP_DIR_TO_NON_DIR`", "name": "`err_fs_cp_dir_to_non_dir`", "meta": { "added": [ "v16.7.0" ], "changes": [] }, "desc": "An attempt was made to copy a directory to a non-directory (file, symlink,\netc.) using fs.cp()
.
An attempt was made to copy over a file that already existed with\nfs.cp()
, with the force
and errorOnExist
set to true
.
When using fs.cp()
, src
or dest
pointed to an invalid path.
An error is thrown when writing to an HTTP response which does not allow\ncontents.
", "type": "module", "displayName": "`ERR_HTTP_BODY_NOT_ALLOWED`" }, { "textRaw": "`ERR_HTTP_CONTENT_LENGTH_MISMATCH`", "name": "`err_http_content_length_mismatch`", "desc": "Response body size doesn't match with the specified content-length header value.
\n", "type": "module", "displayName": "`ERR_HTTP_CONTENT_LENGTH_MISMATCH`" }, { "textRaw": "`ERR_FS_CP_FIFO_PIPE`", "name": "`err_fs_cp_fifo_pipe`", "meta": { "added": [ "v16.7.0" ], "changes": [] }, "desc": "An attempt was made to copy a named pipe with fs.cp()
.
An attempt was made to copy a non-directory (file, symlink, etc.) to a directory\nusing fs.cp()
.
An attempt was made to copy to a socket with fs.cp()
.
When using fs.cp()
, a symlink in dest
pointed to a subdirectory\nof src
.
An attempt was made to copy to an unknown file type with fs.cp()
.
Path is a directory.
\n", "type": "module", "displayName": "`ERR_FS_EISDIR`" }, { "textRaw": "`ERR_FS_FILE_TOO_LARGE`", "name": "`err_fs_file_too_large`", "desc": "An attempt has been made to read a file whose size is larger than the maximum\nallowed size for a Buffer
.
An invalid symlink type was passed to the fs.symlink()
or\nfs.symlinkSync()
methods.
An attempt was made to add more headers after the headers had already been sent.
\n", "type": "module", "displayName": "`ERR_HTTP_HEADERS_SENT`" }, { "textRaw": "`ERR_HTTP_INVALID_HEADER_VALUE`", "name": "`err_http_invalid_header_value`", "desc": "An invalid HTTP header value was specified.
\n", "type": "module", "displayName": "`ERR_HTTP_INVALID_HEADER_VALUE`" }, { "textRaw": "`ERR_HTTP_INVALID_STATUS_CODE`", "name": "`err_http_invalid_status_code`", "desc": "Status code was outside the regular status code range (100-999).
\n", "type": "module", "displayName": "`ERR_HTTP_INVALID_STATUS_CODE`" }, { "textRaw": "`ERR_HTTP_REQUEST_TIMEOUT`", "name": "`err_http_request_timeout`", "desc": "The client has not sent the entire request within the allowed time.
\n", "type": "module", "displayName": "`ERR_HTTP_REQUEST_TIMEOUT`" }, { "textRaw": "`ERR_HTTP_SOCKET_ASSIGNED`", "name": "`err_http_socket_assigned`", "desc": "The given ServerResponse
was already assigned a socket.
Changing the socket encoding is not allowed per RFC 7230 Section 3.
\n", "type": "module", "displayName": "`ERR_HTTP_SOCKET_ENCODING`" }, { "textRaw": "`ERR_HTTP_TRAILER_INVALID`", "name": "`err_http_trailer_invalid`", "desc": "The Trailer
header was set even though the transfer encoding does not support\nthat.
HTTP/2 ALTSVC frames require a valid origin.
\n", "type": "module", "displayName": "`ERR_HTTP2_ALTSVC_INVALID_ORIGIN`" }, { "textRaw": "`ERR_HTTP2_ALTSVC_LENGTH`", "name": "`err_http2_altsvc_length`", "desc": "HTTP/2 ALTSVC frames are limited to a maximum of 16,382 payload bytes.
\n", "type": "module", "displayName": "`ERR_HTTP2_ALTSVC_LENGTH`" }, { "textRaw": "`ERR_HTTP2_CONNECT_AUTHORITY`", "name": "`err_http2_connect_authority`", "desc": "For HTTP/2 requests using the CONNECT
method, the :authority
pseudo-header\nis required.
For HTTP/2 requests using the CONNECT
method, the :path
pseudo-header is\nforbidden.
For HTTP/2 requests using the CONNECT
method, the :scheme
pseudo-header is\nforbidden.
A non-specific HTTP/2 error has occurred.
\n", "type": "module", "displayName": "`ERR_HTTP2_ERROR`" }, { "textRaw": "`ERR_HTTP2_GOAWAY_SESSION`", "name": "`err_http2_goaway_session`", "desc": "New HTTP/2 Streams may not be opened after the Http2Session
has received a\nGOAWAY
frame from the connected peer.
Multiple values were provided for an HTTP/2 header field that was required to\nhave only a single value.
\n", "type": "module", "displayName": "`ERR_HTTP2_HEADER_SINGLE_VALUE`" }, { "textRaw": "`ERR_HTTP2_HEADERS_AFTER_RESPOND`", "name": "`err_http2_headers_after_respond`", "desc": "An additional headers was specified after an HTTP/2 response was initiated.
\n", "type": "module", "displayName": "`ERR_HTTP2_HEADERS_AFTER_RESPOND`" }, { "textRaw": "`ERR_HTTP2_HEADERS_SENT`", "name": "`err_http2_headers_sent`", "desc": "An attempt was made to send multiple response headers.
\n", "type": "module", "displayName": "`ERR_HTTP2_HEADERS_SENT`" }, { "textRaw": "`ERR_HTTP2_INFO_STATUS_NOT_ALLOWED`", "name": "`err_http2_info_status_not_allowed`", "desc": "Informational HTTP status codes (1xx
) may not be set as the response status\ncode on HTTP/2 responses.
HTTP/1 connection specific headers are forbidden to be used in HTTP/2\nrequests and responses.
\n", "type": "module", "displayName": "`ERR_HTTP2_INVALID_CONNECTION_HEADERS`" }, { "textRaw": "`ERR_HTTP2_INVALID_HEADER_VALUE`", "name": "`err_http2_invalid_header_value`", "desc": "An invalid HTTP/2 header value was specified.
\n", "type": "module", "displayName": "`ERR_HTTP2_INVALID_HEADER_VALUE`" }, { "textRaw": "`ERR_HTTP2_INVALID_INFO_STATUS`", "name": "`err_http2_invalid_info_status`", "desc": "An invalid HTTP informational status code has been specified. Informational\nstatus codes must be an integer between 100
and 199
(inclusive).
HTTP/2 ORIGIN
frames require a valid origin.
Input Buffer
and Uint8Array
instances passed to the\nhttp2.getUnpackedSettings()
API must have a length that is a multiple of\nsix.
Only valid HTTP/2 pseudoheaders (:status
, :path
, :authority
, :scheme
,\nand :method
) may be used.
An action was performed on an Http2Session
object that had already been\ndestroyed.
An invalid value has been specified for an HTTP/2 setting.
\n", "type": "module", "displayName": "`ERR_HTTP2_INVALID_SETTING_VALUE`" }, { "textRaw": "`ERR_HTTP2_INVALID_STREAM`", "name": "`err_http2_invalid_stream`", "desc": "An operation was performed on a stream that had already been destroyed.
\n", "type": "module", "displayName": "`ERR_HTTP2_INVALID_STREAM`" }, { "textRaw": "`ERR_HTTP2_MAX_PENDING_SETTINGS_ACK`", "name": "`err_http2_max_pending_settings_ack`", "desc": "Whenever an HTTP/2 SETTINGS
frame is sent to a connected peer, the peer is\nrequired to send an acknowledgment that it has received and applied the new\nSETTINGS
. By default, a maximum number of unacknowledged SETTINGS
frames may\nbe sent at any given time. This error code is used when that limit has been\nreached.
An attempt was made to initiate a new push stream from within a push stream.\nNested push streams are not permitted.
\n", "type": "module", "displayName": "`ERR_HTTP2_NESTED_PUSH`" }, { "textRaw": "`ERR_HTTP2_NO_MEM`", "name": "`err_http2_no_mem`", "desc": "Out of memory when using the http2session.setLocalWindowSize(windowSize)
API.
An attempt was made to directly manipulate (read, write, pause, resume, etc.) a\nsocket attached to an Http2Session
.
HTTP/2 ORIGIN
frames are limited to a length of 16382 bytes.
The number of streams created on a single HTTP/2 session reached the maximum\nlimit.
\n", "type": "module", "displayName": "`ERR_HTTP2_OUT_OF_STREAMS`" }, { "textRaw": "`ERR_HTTP2_PAYLOAD_FORBIDDEN`", "name": "`err_http2_payload_forbidden`", "desc": "A message payload was specified for an HTTP response code for which a payload is\nforbidden.
\n", "type": "module", "displayName": "`ERR_HTTP2_PAYLOAD_FORBIDDEN`" }, { "textRaw": "`ERR_HTTP2_PING_CANCEL`", "name": "`err_http2_ping_cancel`", "desc": "An HTTP/2 ping was canceled.
\n", "type": "module", "displayName": "`ERR_HTTP2_PING_CANCEL`" }, { "textRaw": "`ERR_HTTP2_PING_LENGTH`", "name": "`err_http2_ping_length`", "desc": "HTTP/2 ping payloads must be exactly 8 bytes in length.
\n", "type": "module", "displayName": "`ERR_HTTP2_PING_LENGTH`" }, { "textRaw": "`ERR_HTTP2_PSEUDOHEADER_NOT_ALLOWED`", "name": "`err_http2_pseudoheader_not_allowed`", "desc": "An HTTP/2 pseudo-header has been used inappropriately. Pseudo-headers are header\nkey names that begin with the :
prefix.
An attempt was made to create a push stream, which had been disabled by the\nclient.
\n", "type": "module", "displayName": "`ERR_HTTP2_PUSH_DISABLED`" }, { "textRaw": "`ERR_HTTP2_SEND_FILE`", "name": "`err_http2_send_file`", "desc": "An attempt was made to use the Http2Stream.prototype.responseWithFile()
API to\nsend a directory.
An attempt was made to use the Http2Stream.prototype.responseWithFile()
API to\nsend something other than a regular file, but offset
or length
options were\nprovided.
The Http2Session
closed with a non-zero error code.
The Http2Session
settings canceled.
An attempt was made to connect a Http2Session
object to a net.Socket
or\ntls.TLSSocket
that had already been bound to another Http2Session
object.
An attempt was made to use the socket
property of an Http2Session
that\nhas already been closed.
Use of the 101
Informational status code is forbidden in HTTP/2.
An invalid HTTP status code has been specified. Status codes must be an integer\nbetween 100
and 599
(inclusive).
An Http2Stream
was destroyed before any data was transmitted to the connected\npeer.
A non-zero error code was been specified in an RST_STREAM
frame.
When setting the priority for an HTTP/2 stream, the stream may be marked as\na dependency for a parent stream. This error code is used when an attempt is\nmade to mark a stream and dependent of itself.
\n", "type": "module", "displayName": "`ERR_HTTP2_STREAM_SELF_DEPENDENCY`" }, { "textRaw": "`ERR_HTTP2_TOO_MANY_CUSTOM_SETTINGS`", "name": "`err_http2_too_many_custom_settings`", "desc": "The number of supported custom settings (10) has been exceeded.
\n", "type": "module", "displayName": "`ERR_HTTP2_TOO_MANY_CUSTOM_SETTINGS`" }, { "textRaw": "`ERR_HTTP2_TOO_MANY_INVALID_FRAMES`", "name": "`err_http2_too_many_invalid_frames`", "meta": { "added": [ "v15.14.0" ], "changes": [] }, "desc": "The limit of acceptable invalid HTTP/2 protocol frames sent by the peer,\nas specified through the maxSessionInvalidFrames
option, has been exceeded.
Trailing headers have already been sent on the Http2Stream
.
The http2stream.sendTrailers()
method cannot be called until after the\n'wantTrailers'
event is emitted on an Http2Stream
object. The\n'wantTrailers'
event will only be emitted if the waitForTrailers
option\nis set for the Http2Stream
.
http2.connect()
was passed a URL that uses any protocol other than http:
or\nhttps:
.
An attempt was made to construct an object using a non-public constructor.
\n", "type": "module", "displayName": "`ERR_ILLEGAL_CONSTRUCTOR`" }, { "textRaw": "`ERR_IMPORT_ATTRIBUTE_TYPE_INCOMPATIBLE`", "name": "`err_import_attribute_type_incompatible`", "meta": { "added": [ "v21.1.0" ], "changes": [] }, "desc": "An import type
attribute was provided, but the specified module is of a\ndifferent type.
An import attribute is missing, preventing the specified module to be imported.
\n", "type": "module", "displayName": "`ERR_IMPORT_ATTRIBUTE_MISSING`" }, { "textRaw": "`ERR_IMPORT_ATTRIBUTE_UNSUPPORTED`", "name": "`err_import_attribute_unsupported`", "meta": { "added": [ "v21.0.0" ], "changes": [] }, "desc": "An import attribute is not supported by this version of Node.js.
\n", "type": "module", "displayName": "`ERR_IMPORT_ATTRIBUTE_UNSUPPORTED`" }, { "textRaw": "`ERR_INCOMPATIBLE_OPTION_PAIR`", "name": "`err_incompatible_option_pair`", "desc": "An option pair is incompatible with each other and cannot be used at the same\ntime.
\n", "type": "module", "displayName": "`ERR_INCOMPATIBLE_OPTION_PAIR`" }, { "textRaw": "`ERR_INPUT_TYPE_NOT_ALLOWED`", "name": "`err_input_type_not_allowed`", "stability": 1, "stabilityText": "Experimental", "desc": "The --input-type
flag was used to attempt to execute a file. This flag can\nonly be used with input via --eval
, --print
, or STDIN
.
While using the node:inspector
module, an attempt was made to activate the\ninspector when it already started to listen on a port. Use inspector.close()
\nbefore activating it on a different address.
While using the node:inspector
module, an attempt was made to connect when the\ninspector was already connected.
While using the node:inspector
module, an attempt was made to use the\ninspector after the session had already closed.
An error occurred while issuing a command via the node:inspector
module.
The inspector
is not active when inspector.waitForDebugger()
is called.
The node:inspector
module is not available for use.
While using the node:inspector
module, an attempt was made to use the\ninspector before it was connected.
An API was called on the main thread that can only be used from\nthe worker thread.
\n", "type": "module", "displayName": "`ERR_INSPECTOR_NOT_WORKER`" }, { "textRaw": "`ERR_INTERNAL_ASSERTION`", "name": "`err_internal_assertion`", "desc": "There was a bug in Node.js or incorrect usage of Node.js internals.\nTo fix the error, open an issue at https://github.com/nodejs/node/issues.
\n", "type": "module", "displayName": "`ERR_INTERNAL_ASSERTION`" }, { "textRaw": "`ERR_INVALID_ADDRESS_FAMILY`", "name": "`err_invalid_address_family`", "desc": "The provided address family is not understood by the Node.js API.
\n", "type": "module", "displayName": "`ERR_INVALID_ADDRESS_FAMILY`" }, { "textRaw": "`ERR_INVALID_ARG_TYPE`", "name": "`err_invalid_arg_type`", "desc": "An argument of the wrong type was passed to a Node.js API.
\n", "type": "module", "displayName": "`ERR_INVALID_ARG_TYPE`" }, { "textRaw": "`ERR_INVALID_ARG_VALUE`", "name": "`err_invalid_arg_value`", "desc": "An invalid or unsupported value was passed for a given argument.
\n", "type": "module", "displayName": "`ERR_INVALID_ARG_VALUE`" }, { "textRaw": "`ERR_INVALID_ASYNC_ID`", "name": "`err_invalid_async_id`", "desc": "An invalid asyncId
or triggerAsyncId
was passed using AsyncHooks
. An id\nless than -1 should never happen.
A swap was performed on a Buffer
but its size was not compatible with the\noperation.
Invalid characters were detected in headers.
\n", "type": "module", "displayName": "`ERR_INVALID_CHAR`" }, { "textRaw": "`ERR_INVALID_CURSOR_POS`", "name": "`err_invalid_cursor_pos`", "desc": "A cursor on a given stream cannot be moved to a specified row without a\nspecified column.
\n", "type": "module", "displayName": "`ERR_INVALID_CURSOR_POS`" }, { "textRaw": "`ERR_INVALID_FD`", "name": "`err_invalid_fd`", "desc": "A file descriptor ('fd') was not valid (e.g. it was a negative value).
\n", "type": "module", "displayName": "`ERR_INVALID_FD`" }, { "textRaw": "`ERR_INVALID_FD_TYPE`", "name": "`err_invalid_fd_type`", "desc": "A file descriptor ('fd') type was not valid.
\n", "type": "module", "displayName": "`ERR_INVALID_FD_TYPE`" }, { "textRaw": "`ERR_INVALID_FILE_URL_HOST`", "name": "`err_invalid_file_url_host`", "desc": "A Node.js API that consumes file:
URLs (such as certain functions in the\nfs
module) encountered a file URL with an incompatible host. This\nsituation can only occur on Unix-like systems where only localhost
or an empty\nhost is supported.
A Node.js API that consumes file:
URLs (such as certain functions in the\nfs
module) encountered a file URL with an incompatible path. The exact\nsemantics for determining whether a path can be used is platform-dependent.
An attempt was made to send an unsupported \"handle\" over an IPC communication\nchannel to a child process. See subprocess.send()
and process.send()
\nfor more information.
An invalid HTTP token was supplied.
\n", "type": "module", "displayName": "`ERR_INVALID_HTTP_TOKEN`" }, { "textRaw": "`ERR_INVALID_IP_ADDRESS`", "name": "`err_invalid_ip_address`", "desc": "An IP address is not valid.
\n", "type": "module", "displayName": "`ERR_INVALID_IP_ADDRESS`" }, { "textRaw": "`ERR_INVALID_MIME_SYNTAX`", "name": "`err_invalid_mime_syntax`", "desc": "The syntax of a MIME is not valid.
\n", "type": "module", "displayName": "`ERR_INVALID_MIME_SYNTAX`" }, { "textRaw": "`ERR_INVALID_MODULE`", "name": "`err_invalid_module`", "meta": { "added": [ "v15.0.0", "v14.18.0" ], "changes": [] }, "desc": "An attempt was made to load a module that does not exist or was otherwise not\nvalid.
\n", "type": "module", "displayName": "`ERR_INVALID_MODULE`" }, { "textRaw": "`ERR_INVALID_MODULE_SPECIFIER`", "name": "`err_invalid_module_specifier`", "desc": "The imported module string is an invalid URL, package name, or package subpath\nspecifier.
\n", "type": "module", "displayName": "`ERR_INVALID_MODULE_SPECIFIER`" }, { "textRaw": "`ERR_INVALID_OBJECT_DEFINE_PROPERTY`", "name": "`err_invalid_object_define_property`", "desc": "An error occurred while setting an invalid attribute on the property of\nan object.
\n", "type": "module", "displayName": "`ERR_INVALID_OBJECT_DEFINE_PROPERTY`" }, { "textRaw": "`ERR_INVALID_PACKAGE_CONFIG`", "name": "`err_invalid_package_config`", "desc": "An invalid package.json
file failed parsing.
The package.json
\"exports\"
field contains an invalid target mapping\nvalue for the attempted module resolution.
While using the Performance Timing API (perf_hooks
), a performance mark is\ninvalid.
An invalid options.protocol
was passed to http.request()
.
Both breakEvalOnSigint
and eval
options were set in the REPL
config,\nwhich is not supported.
The input may not be used in the REPL
. The conditions under which this\nerror is used are described in the REPL
documentation.
Thrown in case a function option does not provide a valid value for one of its\nreturned object properties on execution.
\n", "type": "module", "displayName": "`ERR_INVALID_RETURN_PROPERTY`" }, { "textRaw": "`ERR_INVALID_RETURN_PROPERTY_VALUE`", "name": "`err_invalid_return_property_value`", "desc": "Thrown in case a function option does not provide an expected value\ntype for one of its returned object properties on execution.
\n", "type": "module", "displayName": "`ERR_INVALID_RETURN_PROPERTY_VALUE`" }, { "textRaw": "`ERR_INVALID_RETURN_VALUE`", "name": "`err_invalid_return_value`", "desc": "Thrown in case a function option does not return an expected value\ntype on execution, such as when a function is expected to return a promise.
\n", "type": "module", "displayName": "`ERR_INVALID_RETURN_VALUE`" }, { "textRaw": "`ERR_INVALID_STATE`", "name": "`err_invalid_state`", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Indicates that an operation cannot be completed due to an invalid state.\nFor instance, an object may have already been destroyed, or may be\nperforming another operation.
\n", "type": "module", "displayName": "`ERR_INVALID_STATE`" }, { "textRaw": "`ERR_INVALID_SYNC_FORK_INPUT`", "name": "`err_invalid_sync_fork_input`", "desc": "A Buffer
, TypedArray
, DataView
, or string
was provided as stdio input to\nan asynchronous fork. See the documentation for the child_process
module\nfor more information.
A Node.js API function was called with an incompatible this
value.
const urlSearchParams = new URLSearchParams('foo=bar&baz=new');\n\nconst buf = Buffer.alloc(1);\nurlSearchParams.has.call(buf, 'foo');\n// Throws a TypeError with code 'ERR_INVALID_THIS'\n
\n",
"type": "module",
"displayName": "`ERR_INVALID_THIS`"
},
{
"textRaw": "`ERR_INVALID_TUPLE`",
"name": "`err_invalid_tuple`",
"desc": "An element in the iterable
provided to the WHATWG\nURLSearchParams
constructor did not\nrepresent a [name, value]
tuple – that is, if an element is not iterable, or\ndoes not consist of exactly two elements.
An invalid URI was passed.
\n", "type": "module", "displayName": "`ERR_INVALID_URI`" }, { "textRaw": "`ERR_INVALID_URL`", "name": "`err_invalid_url`", "desc": "An invalid URL was passed to the WHATWG URL
\nconstructor or the legacy url.parse()
to be parsed.\nThe thrown error object typically has an additional property 'input'
that\ncontains the URL that failed to parse.
An attempt was made to use a URL of an incompatible scheme (protocol) for a\nspecific purpose. It is only used in the WHATWG URL API support in the\nfs
module (which only accepts URLs with 'file'
scheme), but may be used\nin other Node.js APIs as well in the future.
An attempt was made to use an IPC communication channel that was already closed.
\n", "type": "module", "displayName": "`ERR_IPC_CHANNEL_CLOSED`" }, { "textRaw": "`ERR_IPC_DISCONNECTED`", "name": "`err_ipc_disconnected`", "desc": "An attempt was made to disconnect an IPC communication channel that was already\ndisconnected. See the documentation for the child_process
module\nfor more information.
An attempt was made to create a child Node.js process using more than one IPC\ncommunication channel. See the documentation for the child_process
module\nfor more information.
An attempt was made to open an IPC communication channel with a synchronously\nforked Node.js process. See the documentation for the child_process
module\nfor more information.
An ESM loader hook returned without calling next()
and without explicitly\nsignaling a short circuit.
An attempt was made to load a resource, but the resource did not match the\nintegrity defined by the policy manifest. See the documentation for policy\nmanifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_ASSERT_INTEGRITY`" }, { "textRaw": "`ERR_MANIFEST_DEPENDENCY_MISSING`", "name": "`err_manifest_dependency_missing`", "desc": "An attempt was made to load a resource, but the resource was not listed as a\ndependency from the location that attempted to load it. See the documentation\nfor policy manifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_DEPENDENCY_MISSING`" }, { "textRaw": "`ERR_MANIFEST_INTEGRITY_MISMATCH`", "name": "`err_manifest_integrity_mismatch`", "desc": "An attempt was made to load a policy manifest, but the manifest had multiple\nentries for a resource which did not match each other. Update the manifest\nentries to match in order to resolve this error. See the documentation for\npolicy manifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_INTEGRITY_MISMATCH`" }, { "textRaw": "`ERR_MANIFEST_INVALID_RESOURCE_FIELD`", "name": "`err_manifest_invalid_resource_field`", "desc": "A policy manifest resource had an invalid value for one of its fields. Update\nthe manifest entry to match in order to resolve this error. See the\ndocumentation for policy manifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_INVALID_RESOURCE_FIELD`" }, { "textRaw": "`ERR_MANIFEST_INVALID_SPECIFIER`", "name": "`err_manifest_invalid_specifier`", "desc": "A policy manifest resource had an invalid value for one of its dependency\nmappings. Update the manifest entry to match to resolve this error. See the\ndocumentation for policy manifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_INVALID_SPECIFIER`" }, { "textRaw": "`ERR_MANIFEST_PARSE_POLICY`", "name": "`err_manifest_parse_policy`", "desc": "An attempt was made to load a policy manifest, but the manifest was unable to\nbe parsed. See the documentation for policy manifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_PARSE_POLICY`" }, { "textRaw": "`ERR_MANIFEST_TDZ`", "name": "`err_manifest_tdz`", "desc": "An attempt was made to read from a policy manifest, but the manifest\ninitialization has not yet taken place. This is likely a bug in Node.js.
\n", "type": "module", "displayName": "`ERR_MANIFEST_TDZ`" }, { "textRaw": "`ERR_MANIFEST_UNKNOWN_ONERROR`", "name": "`err_manifest_unknown_onerror`", "desc": "A policy manifest was loaded, but had an unknown value for its \"onerror\"\nbehavior. See the documentation for policy manifests for more information.
\n", "type": "module", "displayName": "`ERR_MANIFEST_UNKNOWN_ONERROR`" }, { "textRaw": "`ERR_MEMORY_ALLOCATION_FAILED`", "name": "`err_memory_allocation_failed`", "desc": "An attempt was made to allocate memory (usually in the C++ layer) but it\nfailed.
\n", "type": "module", "displayName": "`ERR_MEMORY_ALLOCATION_FAILED`" }, { "textRaw": "`ERR_MESSAGE_TARGET_CONTEXT_UNAVAILABLE`", "name": "`err_message_target_context_unavailable`", "meta": { "added": [ "v14.5.0", "v12.19.0" ], "changes": [] }, "desc": "A message posted to a MessagePort
could not be deserialized in the target\nvm Context
. Not all Node.js objects can be successfully instantiated in\nany context at this time, and attempting to transfer them using postMessage()
\ncan fail on the receiving side in that case.
A method is required but not implemented.
\n", "type": "module", "displayName": "`ERR_METHOD_NOT_IMPLEMENTED`" }, { "textRaw": "`ERR_MISSING_ARGS`", "name": "`err_missing_args`", "desc": "A required argument of a Node.js API was not passed. This is only used for\nstrict compliance with the API specification (which in some cases may accept\nfunc(undefined)
but not func()
). In most native Node.js APIs,\nfunc(undefined)
and func()
are treated identically, and the\nERR_INVALID_ARG_TYPE
error code may be used instead.
For APIs that accept options objects, some options might be mandatory. This code\nis thrown if a required option is missing.
\n", "type": "module", "displayName": "`ERR_MISSING_OPTION`" }, { "textRaw": "`ERR_MISSING_PASSPHRASE`", "name": "`err_missing_passphrase`", "desc": "An attempt was made to read an encrypted key without specifying a passphrase.
\n", "type": "module", "displayName": "`ERR_MISSING_PASSPHRASE`" }, { "textRaw": "`ERR_MISSING_PLATFORM_FOR_WORKER`", "name": "`err_missing_platform_for_worker`", "desc": "The V8 platform used by this instance of Node.js does not support creating\nWorkers. This is caused by lack of embedder support for Workers. In particular,\nthis error will not occur with standard builds of Node.js.
\n", "type": "module", "displayName": "`ERR_MISSING_PLATFORM_FOR_WORKER`" }, { "textRaw": "`ERR_MODULE_NOT_FOUND`", "name": "`err_module_not_found`", "desc": "A module file could not be resolved by the ECMAScript modules loader while\nattempting an import
operation or when loading the program entry point.
A callback was called more than once.
\nA callback is almost always meant to only be called once as the query\ncan either be fulfilled or rejected but not both at the same time. The latter\nwould be possible by calling a callback more than once.
\n", "type": "module", "displayName": "`ERR_MULTIPLE_CALLBACK`" }, { "textRaw": "`ERR_NAPI_CONS_FUNCTION`", "name": "`err_napi_cons_function`", "desc": "While using Node-API
, a constructor passed was not a function.
While calling napi_create_dataview()
, a given offset
was outside the bounds\nof the dataview or offset + length
was larger than a length of given buffer
.
While calling napi_create_typedarray()
, the provided offset
was not a\nmultiple of the element size.
While calling napi_create_typedarray()
, (length * size_of_element) + byte_offset
was larger than the length of given buffer
.
An error occurred while invoking the JavaScript portion of the thread-safe\nfunction.
\n", "type": "module", "displayName": "`ERR_NAPI_TSFN_CALL_JS`" }, { "textRaw": "`ERR_NAPI_TSFN_GET_UNDEFINED`", "name": "`err_napi_tsfn_get_undefined`", "desc": "An error occurred while attempting to retrieve the JavaScript undefined
\nvalue.
On the main thread, values are removed from the queue associated with the\nthread-safe function in an idle loop. This error indicates that an error\nhas occurred when attempting to start the loop.
\n", "type": "module", "displayName": "`ERR_NAPI_TSFN_START_IDLE_LOOP`" }, { "textRaw": "`ERR_NAPI_TSFN_STOP_IDLE_LOOP`", "name": "`err_napi_tsfn_stop_idle_loop`", "desc": "Once no more items are left in the queue, the idle loop must be suspended. This\nerror indicates that the idle loop has failed to stop.
\n", "type": "module", "displayName": "`ERR_NAPI_TSFN_STOP_IDLE_LOOP`" }, { "textRaw": "`ERR_NOT_BUILDING_SNAPSHOT`", "name": "`err_not_building_snapshot`", "desc": "An attempt was made to use operations that can only be used when building\nV8 startup snapshot even though Node.js isn't building one.
\n", "type": "module", "displayName": "`ERR_NOT_BUILDING_SNAPSHOT`" }, { "textRaw": "`ERR_NOT_IN_SINGLE_EXECUTABLE_APPLICATION`", "name": "`err_not_in_single_executable_application`", "meta": { "added": [ "v21.7.0" ], "changes": [] }, "desc": "The operation cannot be performed when it's not in a single-executable\napplication.
\n", "type": "module", "displayName": "`ERR_NOT_IN_SINGLE_EXECUTABLE_APPLICATION`" }, { "textRaw": "`ERR_NOT_SUPPORTED_IN_SNAPSHOT`", "name": "`err_not_supported_in_snapshot`", "desc": "An attempt was made to perform operations that are not supported when\nbuilding a startup snapshot.
\n", "type": "module", "displayName": "`ERR_NOT_SUPPORTED_IN_SNAPSHOT`" }, { "textRaw": "`ERR_NO_CRYPTO`", "name": "`err_no_crypto`", "desc": "An attempt was made to use crypto features while Node.js was not compiled with\nOpenSSL crypto support.
\n", "type": "module", "displayName": "`ERR_NO_CRYPTO`" }, { "textRaw": "`ERR_NO_ICU`", "name": "`err_no_icu`", "desc": "An attempt was made to use features that require ICU, but Node.js was not\ncompiled with ICU support.
\n", "type": "module", "displayName": "`ERR_NO_ICU`" }, { "textRaw": "`ERR_NON_CONTEXT_AWARE_DISABLED`", "name": "`err_non_context_aware_disabled`", "desc": "A non-context-aware native addon was loaded in a process that disallows them.
\n", "type": "module", "displayName": "`ERR_NON_CONTEXT_AWARE_DISABLED`" }, { "textRaw": "`ERR_OUT_OF_RANGE`", "name": "`err_out_of_range`", "desc": "A given value is out of the accepted range.
\n", "type": "module", "displayName": "`ERR_OUT_OF_RANGE`" }, { "textRaw": "`ERR_PACKAGE_IMPORT_NOT_DEFINED`", "name": "`err_package_import_not_defined`", "desc": "The package.json
\"imports\"
field does not define the given internal\npackage specifier mapping.
The package.json
\"exports\"
field does not export the requested subpath.\nBecause exports are encapsulated, private internal modules that are not exported\ncannot be imported through the package resolution, unless using an absolute URL.
When strict
set to true
, thrown by util.parseArgs()
if a <boolean>\nvalue is provided for an option of type <string>, or if a <string>\nvalue is provided for an option of type <boolean>.
Thrown by util.parseArgs()
, when a positional argument is provided and\nallowPositionals
is set to false
.
When strict
set to true
, thrown by util.parseArgs()
if an argument\nis not configured in options
.
An invalid timestamp value was provided for a performance mark or measure.
\n", "type": "module", "displayName": "`ERR_PERFORMANCE_INVALID_TIMESTAMP`" }, { "textRaw": "`ERR_PERFORMANCE_MEASURE_INVALID_OPTIONS`", "name": "`err_performance_measure_invalid_options`", "desc": "Invalid options were provided for a performance measure.
\n", "type": "module", "displayName": "`ERR_PERFORMANCE_MEASURE_INVALID_OPTIONS`" }, { "textRaw": "`ERR_PROTO_ACCESS`", "name": "`err_proto_access`", "desc": "Accessing Object.prototype.__proto__
has been forbidden using\n--disable-proto=throw
. Object.getPrototypeOf
and\nObject.setPrototypeOf
should be used to get and set the prototype of an\nobject.
An attempt was made to require()
an ES Module.
Script execution was interrupted by SIGINT
(For\nexample, Ctrl+C was pressed.)
Script execution timed out, possibly due to bugs in the script being executed.
\n", "type": "module", "displayName": "`ERR_SCRIPT_EXECUTION_TIMEOUT`" }, { "textRaw": "`ERR_SERVER_ALREADY_LISTEN`", "name": "`err_server_already_listen`", "desc": "The server.listen()
method was called while a net.Server
was already\nlistening. This applies to all instances of net.Server
, including HTTP, HTTPS,\nand HTTP/2 Server
instances.
The server.close()
method was called when a net.Server
was not\nrunning. This applies to all instances of net.Server
, including HTTP, HTTPS,\nand HTTP/2 Server
instances.
A key was passed to single executable application APIs to identify an asset,\nbut no match could be found.
\n", "type": "module", "displayName": "`ERR_SINGLE_EXECUTABLE_APPLICATION_ASSET_NOT_FOUND`" }, { "textRaw": "`ERR_SOCKET_ALREADY_BOUND`", "name": "`err_socket_already_bound`", "desc": "An attempt was made to bind a socket that has already been bound.
\n", "type": "module", "displayName": "`ERR_SOCKET_ALREADY_BOUND`" }, { "textRaw": "`ERR_SOCKET_BAD_BUFFER_SIZE`", "name": "`err_socket_bad_buffer_size`", "desc": "An invalid (negative) size was passed for either the recvBufferSize
or\nsendBufferSize
options in dgram.createSocket()
.
An API function expecting a port >= 0 and < 65536 received an invalid value.
\n", "type": "module", "displayName": "`ERR_SOCKET_BAD_PORT`" }, { "textRaw": "`ERR_SOCKET_BAD_TYPE`", "name": "`err_socket_bad_type`", "desc": "An API function expecting a socket type (udp4
or udp6
) received an invalid\nvalue.
While using dgram.createSocket()
, the size of the receive or send Buffer
\ncould not be determined.
An attempt was made to operate on an already closed socket.
\n", "type": "module", "displayName": "`ERR_SOCKET_CLOSED`" }, { "textRaw": "`ERR_SOCKET_CLOSED_BEFORE_CONNECTION`", "name": "`err_socket_closed_before_connection`", "desc": "When calling net.Socket.write()
on a connecting socket and the socket was\nclosed before the connection was established.
The socket was unable to connect to any address returned by the DNS within the\nallowed timeout when using the family autoselection algorithm.
\n", "type": "module", "displayName": "`ERR_SOCKET_CONNECTION_TIMEOUT`" }, { "textRaw": "`ERR_SOCKET_DGRAM_IS_CONNECTED`", "name": "`err_socket_dgram_is_connected`", "desc": "A dgram.connect()
call was made on an already connected socket.
A dgram.disconnect()
or dgram.remoteAddress()
call was made on a\ndisconnected socket.
A call was made and the UDP subsystem was not running.
\n", "type": "module", "displayName": "`ERR_SOCKET_DGRAM_NOT_RUNNING`" }, { "textRaw": "`ERR_SRI_PARSE`", "name": "`err_sri_parse`", "desc": "A string was provided for a Subresource Integrity check, but was unable to be\nparsed. Check the format of integrity attributes by looking at the\nSubresource Integrity specification.
\n", "type": "module", "displayName": "`ERR_SRI_PARSE`" }, { "textRaw": "`ERR_STREAM_ALREADY_FINISHED`", "name": "`err_stream_already_finished`", "desc": "A stream method was called that cannot complete because the stream was\nfinished.
\n", "type": "module", "displayName": "`ERR_STREAM_ALREADY_FINISHED`" }, { "textRaw": "`ERR_STREAM_CANNOT_PIPE`", "name": "`err_stream_cannot_pipe`", "desc": "An attempt was made to call stream.pipe()
on a Writable
stream.
A stream method was called that cannot complete because the stream was\ndestroyed using stream.destroy()
.
An attempt was made to call stream.write()
with a null
chunk.
An error returned by stream.finished()
and stream.pipeline()
, when a stream\nor a pipeline ends non gracefully with no explicit error.
An attempt was made to call stream.push()
after a null
(EOF) had been\npushed to the stream.
An attempt was made to call stream.unshift()
after the 'end'
event was\nemitted.
Prevents an abort if a string decoder was set on the Socket or if the decoder\nis in objectMode
.
const Socket = require('node:net').Socket;\nconst instance = new Socket();\n\ninstance.setEncoding('utf8');\n
\n",
"type": "module",
"displayName": "`ERR_STREAM_WRAP`"
},
{
"textRaw": "`ERR_STREAM_WRITE_AFTER_END`",
"name": "`err_stream_write_after_end`",
"desc": "An attempt was made to call stream.write()
after stream.end()
has been\ncalled.
An attempt has been made to create a string longer than the maximum allowed\nlength.
\n", "type": "module", "displayName": "`ERR_STRING_TOO_LONG`" }, { "textRaw": "`ERR_SYNTHETIC`", "name": "`err_synthetic`", "desc": "An artificial error object used to capture the call stack for diagnostic\nreports.
\n", "type": "module", "displayName": "`ERR_SYNTHETIC`" }, { "textRaw": "`ERR_SYSTEM_ERROR`", "name": "`err_system_error`", "desc": "An unspecified or non-specific system error has occurred within the Node.js\nprocess. The error object will have an err.info
object property with\nadditional details.
An error representing a failing lexer state.
\n", "type": "module", "displayName": "`ERR_TAP_LEXER_ERROR`" }, { "textRaw": "`ERR_TAP_PARSER_ERROR`", "name": "`err_tap_parser_error`", "desc": "An error representing a failing parser state. Additional information about\nthe token causing the error is available via the cause
property.
This error represents a failed TAP validation.
\n", "type": "module", "displayName": "`ERR_TAP_VALIDATION_ERROR`" }, { "textRaw": "`ERR_TEST_FAILURE`", "name": "`err_test_failure`", "desc": "This error represents a failed test. Additional information about the failure\nis available via the cause
property. The failureType
property specifies\nwhat the test was doing when the failure occurred.
This error is thrown when an ALPNCallback
returns a value that is not in the\nlist of ALPN protocols offered by the client.
This error is thrown when creating a TLSServer
if the TLS options include\nboth ALPNProtocols
and ALPNCallback
. These options are mutually exclusive.
This error is thrown by checkServerIdentity
if a user-supplied\nsubjectaltname
property violates encoding rules. Certificate objects produced\nby Node.js itself always comply with encoding rules and will never cause\nthis error.
While using TLS, the host name/IP of the peer did not match any of the\nsubjectAltNames
in its certificate.
While using TLS, the parameter offered for the Diffie-Hellman (DH
)\nkey-agreement protocol is too small. By default, the key length must be greater\nthan or equal to 1024 bits to avoid vulnerabilities, even though it is strongly\nrecommended to use 2048 bits or larger for stronger security.
A TLS/SSL handshake timed out. In this case, the server must also abort the\nconnection.
\n", "type": "module", "displayName": "`ERR_TLS_HANDSHAKE_TIMEOUT`" }, { "textRaw": "`ERR_TLS_INVALID_CONTEXT`", "name": "`err_tls_invalid_context`", "meta": { "added": [ "v13.3.0" ], "changes": [] }, "desc": "The context must be a SecureContext
.
The specified secureProtocol
method is invalid. It is either unknown, or\ndisabled because it is insecure.
Valid TLS protocol versions are 'TLSv1'
, 'TLSv1.1'
, or 'TLSv1.2'
.
The TLS socket must be connected and securely established. Ensure the 'secure'\nevent is emitted before continuing.
\n", "type": "module", "displayName": "`ERR_TLS_INVALID_STATE`" }, { "textRaw": "`ERR_TLS_PROTOCOL_VERSION_CONFLICT`", "name": "`err_tls_protocol_version_conflict`", "desc": "Attempting to set a TLS protocol minVersion
or maxVersion
conflicts with an\nattempt to set the secureProtocol
explicitly. Use one mechanism or the other.
Failed to set PSK identity hint. Hint may be too long.
\n", "type": "module", "displayName": "`ERR_TLS_PSK_SET_IDENTIY_HINT_FAILED`" }, { "textRaw": "`ERR_TLS_RENEGOTIATION_DISABLED`", "name": "`err_tls_renegotiation_disabled`", "desc": "An attempt was made to renegotiate TLS on a socket instance with renegotiation\ndisabled.
\n", "type": "module", "displayName": "`ERR_TLS_RENEGOTIATION_DISABLED`" }, { "textRaw": "`ERR_TLS_REQUIRED_SERVER_NAME`", "name": "`err_tls_required_server_name`", "desc": "While using TLS, the server.addContext()
method was called without providing\na host name in the first parameter.
An excessive amount of TLS renegotiations is detected, which is a potential\nvector for denial-of-service attacks.
\n", "type": "module", "displayName": "`ERR_TLS_SESSION_ATTACK`" }, { "textRaw": "`ERR_TLS_SNI_FROM_SERVER`", "name": "`err_tls_sni_from_server`", "desc": "An attempt was made to issue Server Name Indication from a TLS server-side\nsocket, which is only valid from a client.
\n", "type": "module", "displayName": "`ERR_TLS_SNI_FROM_SERVER`" }, { "textRaw": "`ERR_TRACE_EVENTS_CATEGORY_REQUIRED`", "name": "`err_trace_events_category_required`", "desc": "The trace_events.createTracing()
method requires at least one trace event\ncategory.
The node:trace_events
module could not be loaded because Node.js was compiled\nwith the --without-v8-platform
flag.
A Transform
stream finished while it was still transforming.
A Transform
stream finished with data still in the write buffer.
The initialization of a TTY failed due to a system error.
\n", "type": "module", "displayName": "`ERR_TTY_INIT_FAILED`" }, { "textRaw": "`ERR_UNAVAILABLE_DURING_EXIT`", "name": "`err_unavailable_during_exit`", "desc": "Function was called within a process.on('exit')
handler that shouldn't be\ncalled within process.on('exit')
handler.
process.setUncaughtExceptionCaptureCallback()
was called twice,\nwithout first resetting the callback to null
.
This error is designed to prevent accidentally overwriting a callback registered\nfrom another module.
\n", "type": "module", "displayName": "`ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET`" }, { "textRaw": "`ERR_UNESCAPED_CHARACTERS`", "name": "`err_unescaped_characters`", "desc": "A string that contained unescaped characters was received.
\n", "type": "module", "displayName": "`ERR_UNESCAPED_CHARACTERS`" }, { "textRaw": "`ERR_UNHANDLED_ERROR`", "name": "`err_unhandled_error`", "desc": "An unhandled error occurred (for instance, when an 'error'
event is emitted\nby an EventEmitter
but an 'error'
handler is not registered).
Used to identify a specific kind of internal Node.js error that should not\ntypically be triggered by user code. Instances of this error point to an\ninternal bug within the Node.js binary itself.
\n", "type": "module", "displayName": "`ERR_UNKNOWN_BUILTIN_MODULE`" }, { "textRaw": "`ERR_UNKNOWN_CREDENTIAL`", "name": "`err_unknown_credential`", "desc": "A Unix group or user identifier that does not exist was passed.
\n", "type": "module", "displayName": "`ERR_UNKNOWN_CREDENTIAL`" }, { "textRaw": "`ERR_UNKNOWN_ENCODING`", "name": "`err_unknown_encoding`", "desc": "An invalid or unknown encoding option was passed to an API.
\n", "type": "module", "displayName": "`ERR_UNKNOWN_ENCODING`" }, { "textRaw": "`ERR_UNKNOWN_FILE_EXTENSION`", "name": "`err_unknown_file_extension`", "stability": 1, "stabilityText": "Experimental", "desc": "An attempt was made to load a module with an unknown or unsupported file\nextension.
\n", "type": "module", "displayName": "`ERR_UNKNOWN_FILE_EXTENSION`" }, { "textRaw": "`ERR_UNKNOWN_MODULE_FORMAT`", "name": "`err_unknown_module_format`", "stability": 1, "stabilityText": "Experimental", "desc": "An attempt was made to load a module with an unknown or unsupported format.
\n", "type": "module", "displayName": "`ERR_UNKNOWN_MODULE_FORMAT`" }, { "textRaw": "`ERR_UNKNOWN_SIGNAL`", "name": "`err_unknown_signal`", "desc": "An invalid or unknown process signal was passed to an API expecting a valid\nsignal (such as subprocess.kill()
).
import
a directory URL is unsupported. Instead,\nself-reference a package using its name and define a custom subpath in\nthe \"exports\"
field of the package.json
file.
import './'; // unsupported\nimport './index.js'; // supported\nimport 'package-name'; // supported\n
\n",
"type": "module",
"displayName": "`ERR_UNSUPPORTED_DIR_IMPORT`"
},
{
"textRaw": "`ERR_UNSUPPORTED_ESM_URL_SCHEME`",
"name": "`err_unsupported_esm_url_scheme`",
"desc": "import
with URL schemes other than file
and data
is unsupported.
An attempt was made to resolve an invalid module referrer. This can happen when\nimporting or calling import.meta.resolve()
with either:
file
.try {\n // Trying to import the package 'bare-specifier' from a `data:` URL module:\n await import('data:text/javascript,import \"bare-specifier\"');\n} catch (e) {\n console.log(e.code); // ERR_UNSUPPORTED_RESOLVE_REQUEST\n}\n
\n",
"type": "module",
"displayName": "`ERR_UNSUPPORTED_RESOLVE_REQUEST`"
},
{
"textRaw": "`ERR_USE_AFTER_CLOSE`",
"name": "`err_use_after_close`",
"stability": 1,
"stabilityText": "Experimental",
"desc": "An attempt was made to use something that was already closed.
\n", "type": "module", "displayName": "`ERR_USE_AFTER_CLOSE`" }, { "textRaw": "`ERR_VALID_PERFORMANCE_ENTRY_TYPE`", "name": "`err_valid_performance_entry_type`", "desc": "While using the Performance Timing API (perf_hooks
), no valid performance\nentry types are found.
A dynamic import callback was invoked without --experimental-vm-modules
.
A dynamic import callback was not specified.
\n", "type": "module", "displayName": "`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`" }, { "textRaw": "`ERR_VM_MODULE_ALREADY_LINKED`", "name": "`err_vm_module_already_linked`", "desc": "The module attempted to be linked is not eligible for linking, because of one of\nthe following reasons:
\nlinkingStatus
is 'linked'
)linkingStatus
is 'linking'
)linkingStatus
is 'errored'
)The cachedData
option passed to a module constructor is invalid.
Cached data cannot be created for modules which have already been evaluated.
\n", "type": "module", "displayName": "`ERR_VM_MODULE_CANNOT_CREATE_CACHED_DATA`" }, { "textRaw": "`ERR_VM_MODULE_DIFFERENT_CONTEXT`", "name": "`err_vm_module_different_context`", "desc": "The module being returned from the linker function is from a different context\nthan the parent module. Linked modules must share the same context.
\n", "type": "module", "displayName": "`ERR_VM_MODULE_DIFFERENT_CONTEXT`" }, { "textRaw": "`ERR_VM_MODULE_LINK_FAILURE`", "name": "`err_vm_module_link_failure`", "desc": "The module was unable to be linked due to a failure.
\n", "type": "module", "displayName": "`ERR_VM_MODULE_LINK_FAILURE`" }, { "textRaw": "`ERR_VM_MODULE_NOT_MODULE`", "name": "`err_vm_module_not_module`", "desc": "The fulfilled value of a linking promise is not a vm.Module
object.
The current module's status does not allow for this operation. The specific\nmeaning of the error depends on the specific function.
\n", "type": "module", "displayName": "`ERR_VM_MODULE_STATUS`" }, { "textRaw": "`ERR_WASI_ALREADY_STARTED`", "name": "`err_wasi_already_started`", "desc": "The WASI instance has already started.
\n", "type": "module", "displayName": "`ERR_WASI_ALREADY_STARTED`" }, { "textRaw": "`ERR_WASI_NOT_STARTED`", "name": "`err_wasi_not_started`", "desc": "The WASI instance has not been started.
\n", "type": "module", "displayName": "`ERR_WASI_NOT_STARTED`" }, { "textRaw": "`ERR_WEBASSEMBLY_RESPONSE`", "name": "`err_webassembly_response`", "meta": { "added": [ "v18.1.0" ], "changes": [] }, "desc": "The Response
that has been passed to WebAssembly.compileStreaming
or to\nWebAssembly.instantiateStreaming
is not a valid WebAssembly response.
The Worker
initialization failed.
The execArgv
option passed to the Worker
constructor contains\ninvalid flags.
An operation failed because the Worker
instance is not currently running.
The Worker
instance terminated because it reached its memory limit.
The path for the main script of a worker is neither an absolute path\nnor a relative path starting with ./
or ../
.
All attempts at serializing an uncaught exception from a worker thread failed.
\n", "type": "module", "displayName": "`ERR_WORKER_UNSERIALIZABLE_ERROR`" }, { "textRaw": "`ERR_WORKER_UNSUPPORTED_OPERATION`", "name": "`err_worker_unsupported_operation`", "desc": "The requested functionality is not supported in worker threads.
\n", "type": "module", "displayName": "`ERR_WORKER_UNSUPPORTED_OPERATION`" }, { "textRaw": "`ERR_ZLIB_INITIALIZATION_FAILED`", "name": "`err_zlib_initialization_failed`", "desc": "Creation of a zlib
object failed due to incorrect configuration.
Too much HTTP header data was received. In order to protect against malicious or\nmalconfigured clients, if more than 8 KiB of HTTP header data is received then\nHTTP parsing will abort without a request or response object being created, and\nan Error
with this code will be emitted.
Too much data was received for a chunk extensions. In order to protect against\nmalicious or malconfigured clients, if more than 16 KiB of data is received\nthen an Error
with this code will be emitted.
Server is sending both a Content-Length
header and Transfer-Encoding: chunked
.
Transfer-Encoding: chunked
allows the server to maintain an HTTP persistent\nconnection for dynamically generated content.\nIn this case, the Content-Length
HTTP header cannot be used.
Use Content-Length
or Transfer-Encoding: chunked
.
A module file could not be resolved by the CommonJS modules loader while\nattempting a require()
operation or when loading the program entry point.
The value passed to postMessage()
contained an object that is not supported\nfor transferring.
The UTF-16 encoding was used with hash.digest()
. While the\nhash.digest()
method does allow an encoding
argument to be passed in,\ncausing the method to return a string rather than a Buffer
, the UTF-16\nencoding (e.g. ucs
or utf16le
) is not supported.
Used when a failure occurs sending an individual frame on the HTTP/2\nsession.
\n", "type": "module", "displayName": "`ERR_HTTP2_FRAME_ERROR`" }, { "textRaw": "`ERR_HTTP2_HEADERS_OBJECT`", "name": "`err_http2_headers_object`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when an HTTP/2 Headers Object is expected.
\n", "type": "module", "displayName": "`ERR_HTTP2_HEADERS_OBJECT`" }, { "textRaw": "`ERR_HTTP2_HEADER_REQUIRED`", "name": "`err_http2_header_required`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when a required header is missing in an HTTP/2 message.
\n", "type": "module", "displayName": "`ERR_HTTP2_HEADER_REQUIRED`" }, { "textRaw": "`ERR_HTTP2_INFO_HEADERS_AFTER_RESPOND`", "name": "`err_http2_info_headers_after_respond`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "HTTP/2 informational headers must only be sent prior to calling the\nHttp2Stream.prototype.respond()
method.
Used when an action has been performed on an HTTP/2 Stream that has already\nbeen closed.
\n", "type": "module", "displayName": "`ERR_HTTP2_STREAM_CLOSED`" }, { "textRaw": "`ERR_HTTP_INVALID_CHAR`", "name": "`err_http_invalid_char`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when an invalid character is found in an HTTP response status message\n(reason phrase).
\n", "type": "module", "displayName": "`ERR_HTTP_INVALID_CHAR`" }, { "textRaw": "`ERR_INDEX_OUT_OF_RANGE`", "name": "`err_index_out_of_range`", "meta": { "added": [ "v10.0.0" ], "removed": [ "v11.0.0" ], "changes": [] }, "desc": "A given index was out of the accepted range (e.g. negative offsets).
\n", "type": "module", "displayName": "`ERR_INDEX_OUT_OF_RANGE`" }, { "textRaw": "`ERR_INVALID_OPT_VALUE`", "name": "`err_invalid_opt_value`", "meta": { "added": [ "v8.0.0" ], "removed": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid or unexpected value was passed in an options object.
\n", "type": "module", "displayName": "`ERR_INVALID_OPT_VALUE`" }, { "textRaw": "`ERR_INVALID_OPT_VALUE_ENCODING`", "name": "`err_invalid_opt_value_encoding`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v15.0.0" ], "changes": [] }, "desc": "An invalid or unknown file encoding was passed.
\n", "type": "module", "displayName": "`ERR_INVALID_OPT_VALUE_ENCODING`" }, { "textRaw": "`ERR_INVALID_TRANSFER_OBJECT`", "name": "`err_invalid_transfer_object`", "meta": { "removed": [ "v21.0.0" ], "changes": [ { "version": "v21.0.0", "pr-url": "https://github.com/nodejs/node/pull/47839", "description": "A `DOMException` is thrown instead." } ] }, "desc": "An invalid transfer object was passed to postMessage()
.
An import assertion has failed, preventing the specified module to be imported.
\n", "type": "module", "displayName": "`ERR_IMPORT_ASSERTION_TYPE_FAILED`" }, { "textRaw": "`ERR_IMPORT_ASSERTION_TYPE_MISSING`", "name": "`err_import_assertion_type_missing`", "meta": { "added": [ "v17.1.0", "v16.14.0" ], "removed": [ "v21.1.0" ], "changes": [] }, "desc": "An import assertion is missing, preventing the specified module to be imported.
\n", "type": "module", "displayName": "`ERR_IMPORT_ASSERTION_TYPE_MISSING`" }, { "textRaw": "`ERR_IMPORT_ASSERTION_TYPE_UNSUPPORTED`", "name": "`err_import_assertion_type_unsupported`", "meta": { "added": [ "v17.1.0", "v16.14.0" ], "removed": [ "v21.1.0" ], "changes": [] }, "desc": "An import attribute is not supported by this version of Node.js.
\n", "type": "module", "displayName": "`ERR_IMPORT_ASSERTION_TYPE_UNSUPPORTED`" }, { "textRaw": "`ERR_MISSING_MESSAGE_PORT_IN_TRANSFER_LIST`", "name": "`err_missing_message_port_in_transfer_list`", "meta": { "removed": [ "v15.0.0" ], "changes": [] }, "desc": "This error code was replaced by ERR_MISSING_TRANSFERABLE_IN_TRANSFER_LIST
\nin Node.js v15.0.0, because it is no longer accurate as other types of\ntransferable objects also exist now.
An object that needs to be explicitly listed in the transferList
argument\nis in the object passed to a postMessage()
call, but is not provided\nin the transferList
for that call. Usually, this is a MessagePort
.
In Node.js versions prior to v15.0.0, the error code being used here was\nERR_MISSING_MESSAGE_PORT_IN_TRANSFER_LIST
. However, the set of\ntransferable object types has been expanded to cover more types than\nMessagePort
.
Used by the Node-API
when Constructor.prototype
is not an object.
Response was received but was invalid when importing a module over the network.
\n", "type": "module", "displayName": "`ERR_NETWORK_IMPORT_BAD_RESPONSE`" }, { "textRaw": "`ERR_NETWORK_IMPORT_DISALLOWED`", "name": "`err_network_import_disallowed`", "stability": 1, "stabilityText": "Experimental", "desc": "A network module attempted to load another module that it is not allowed to\nload. Likely this restriction is for security reasons.
\n", "type": "module", "displayName": "`ERR_NETWORK_IMPORT_DISALLOWED`" }, { "textRaw": "`ERR_NO_LONGER_SUPPORTED`", "name": "`err_no_longer_supported`", "desc": "A Node.js API was called in an unsupported manner, such as\nBuffer.write(string, encoding, offset[, length])
.
An operation failed. This is typically used to signal the general failure\nof an asynchronous operation.
\n", "type": "module", "displayName": "`ERR_OPERATION_FAILED`" }, { "textRaw": "`ERR_OUTOFMEMORY`", "name": "`err_outofmemory`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used generically to identify that an operation caused an out of memory\ncondition.
\n", "type": "module", "displayName": "`ERR_OUTOFMEMORY`" }, { "textRaw": "`ERR_PARSE_HISTORY_DATA`", "name": "`err_parse_history_data`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "The node:repl
module was unable to parse data from the REPL history file.
Data could not be sent on a socket.
\n", "type": "module", "displayName": "`ERR_SOCKET_CANNOT_SEND`" }, { "textRaw": "`ERR_STDERR_CLOSE`", "name": "`err_stderr_close`", "meta": { "removed": [ "v10.12.0" ], "changes": [ { "version": "v10.12.0", "pr-url": "https://github.com/nodejs/node/pull/23053", "description": "Rather than emitting an error, `process.stderr.end()` now only closes the stream side but not the underlying resource, making this error obsolete." } ] }, "desc": "An attempt was made to close the process.stderr
stream. By design, Node.js\ndoes not allow stdout
or stderr
streams to be closed by user code.
An attempt was made to close the process.stdout
stream. By design, Node.js\ndoes not allow stdout
or stderr
streams to be closed by user code.
Used when an attempt is made to use a readable stream that has not implemented\nreadable._read()
.
Used when a TLS renegotiation request has failed in a non-specific way.
\n", "type": "module", "displayName": "`ERR_TLS_RENEGOTIATION_FAILED`" }, { "textRaw": "`ERR_TRANSFERRING_EXTERNALIZED_SHAREDARRAYBUFFER`", "name": "`err_transferring_externalized_sharedarraybuffer`", "meta": { "added": [ "v10.5.0" ], "removed": [ "v14.0.0" ], "changes": [] }, "desc": "A SharedArrayBuffer
whose memory is not managed by the JavaScript engine\nor by Node.js was encountered during serialization. Such a SharedArrayBuffer
\ncannot be serialized.
This can only happen when native addons create SharedArrayBuffer
s in\n\"externalized\" mode, or put existing SharedArrayBuffer
into externalized mode.
An attempt was made to launch a Node.js process with an unknown stdin
file\ntype. This error is usually an indication of a bug within Node.js itself,\nalthough it is possible for user code to trigger it.
An attempt was made to launch a Node.js process with an unknown stdout
or\nstderr
file type. This error is usually an indication of a bug within Node.js\nitself, although it is possible for user code to trigger it.
The V8 BreakIterator
API was used but the full ICU data set is not installed.
Used when a given value is out of the accepted range.
\n", "type": "module", "displayName": "`ERR_VALUE_OUT_OF_RANGE`" }, { "textRaw": "`ERR_VM_MODULE_NOT_LINKED`", "name": "`err_vm_module_not_linked`", "desc": "The module must be successfully linked before instantiation.
\n", "type": "module", "displayName": "`ERR_VM_MODULE_NOT_LINKED`" }, { "textRaw": "`ERR_VM_MODULE_LINKING_ERRORED`", "name": "`err_vm_module_linking_errored`", "meta": { "added": [ "v10.0.0" ], "removed": [ "v18.1.0", "v16.17.0" ], "changes": [] }, "desc": "The linker function returned a module for which linking has failed.
\n", "type": "module", "displayName": "`ERR_VM_MODULE_LINKING_ERRORED`" }, { "textRaw": "`ERR_WORKER_UNSUPPORTED_EXTENSION`", "name": "`err_worker_unsupported_extension`", "meta": { "added": [ "v11.0.0" ], "removed": [ "v16.9.0" ], "changes": [] }, "desc": "The pathname used for the main script of a worker has an\nunknown file extension.
\n", "type": "module", "displayName": "`ERR_WORKER_UNSUPPORTED_EXTENSION`" }, { "textRaw": "`ERR_ZLIB_BINDING_CLOSED`", "name": "`err_zlib_binding_closed`", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when an attempt is made to use a zlib
object after it has already been\nclosed.
The native call from process.cpuUsage
could not be processed.
A generic JavaScript <Error> object that does not denote any specific\ncircumstance of why the error occurred. Error
objects capture a \"stack trace\"\ndetailing the point in the code at which the Error
was instantiated, and may\nprovide a text description of the error.
All errors generated by Node.js, including all system and JavaScript errors,\nwill either be instances of, or inherit from, the Error
class.
Creates a .stack
property on targetObject
, which when accessed returns\na string representing the location in the code at which\nError.captureStackTrace()
was called.
const myObject = {};\nError.captureStackTrace(myObject);\nmyObject.stack; // Similar to `new Error().stack`\n
\nThe first line of the trace will be prefixed with\n${myObject.name}: ${myObject.message}
.
The optional constructorOpt
argument accepts a function. If given, all frames\nabove constructorOpt
, including constructorOpt
, will be omitted from the\ngenerated stack trace.
The constructorOpt
argument is useful for hiding implementation\ndetails of error generation from the user. For instance:
function a() {\n b();\n}\n\nfunction b() {\n c();\n}\n\nfunction c() {\n // Create an error without stack trace to avoid calculating the stack trace twice.\n const { stackTraceLimit } = Error;\n Error.stackTraceLimit = 0;\n const error = new Error();\n Error.stackTraceLimit = stackTraceLimit;\n\n // Capture the stack trace above function b\n Error.captureStackTrace(error, b); // Neither function c, nor b is included in the stack trace\n throw error;\n}\n\na();\n
"
}
],
"properties": [
{
"textRaw": "`stackTraceLimit` {number}",
"type": "number",
"name": "stackTraceLimit",
"desc": "The Error.stackTraceLimit
property specifies the number of stack frames\ncollected by a stack trace (whether generated by new Error().stack
or\nError.captureStackTrace(obj)
).
The default value is 10
but may be set to any valid JavaScript number. Changes\nwill affect any stack trace captured after the value has been changed.
If set to a non-number value, or set to a negative number, stack traces will\nnot capture any frames.
" }, { "textRaw": "`cause` {any}", "type": "any", "name": "cause", "meta": { "added": [ "v16.9.0" ], "changes": [] }, "desc": "If present, the error.cause
property is the underlying cause of the Error
.\nIt is used when catching an error and throwing a new one with a different\nmessage or code in order to still have access to the original error.
The error.cause
property is typically set by calling\nnew Error(message, { cause })
. It is not set by the constructor if the\ncause
option is not provided.
This property allows errors to be chained. When serializing Error
objects,\nutil.inspect()
recursively serializes error.cause
if it is set.
const cause = new Error('The remote HTTP server responded with a 500 status');\nconst symptom = new Error('The message failed to send', { cause });\n\nconsole.log(symptom);\n// Prints:\n// Error: The message failed to send\n// at REPL2:1:17\n// at Script.runInThisContext (node:vm:130:12)\n// ... 7 lines matching cause stack trace ...\n// at [_line] [as _line] (node:internal/readline/interface:886:18) {\n// [cause]: Error: The remote HTTP server responded with a 500 status\n// at REPL1:1:15\n// at Script.runInThisContext (node:vm:130:12)\n// at REPLServer.defaultEval (node:repl:574:29)\n// at bound (node:domain:426:15)\n// at REPLServer.runBound [as eval] (node:domain:437:12)\n// at REPLServer.onLine (node:repl:902:10)\n// at REPLServer.emit (node:events:549:35)\n// at REPLServer.emit (node:domain:482:12)\n// at [_onLine] [as _onLine] (node:internal/readline/interface:425:12)\n// at [_line] [as _line] (node:internal/readline/interface:886:18)\n
"
},
{
"textRaw": "`code` {string}",
"type": "string",
"name": "code",
"desc": "The error.code
property is a string label that identifies the kind of error.\nerror.code
is the most stable way to identify an error. It will only change\nbetween major versions of Node.js. In contrast, error.message
strings may\nchange between any versions of Node.js. See Node.js error codes for details\nabout specific codes.
The error.message
property is the string description of the error as set by\ncalling new Error(message)
. The message
passed to the constructor will also\nappear in the first line of the stack trace of the Error
, however changing\nthis property after the Error
object is created may not change the first\nline of the stack trace (for example, when error.stack
is read before this\nproperty is changed).
const err = new Error('The message');\nconsole.error(err.message);\n// Prints: The message\n
"
},
{
"textRaw": "`stack` {string}",
"type": "string",
"name": "stack",
"desc": "The error.stack
property is a string describing the point in the code at which\nthe Error
was instantiated.
Error: Things keep happening!\n at /home/gbusey/file.js:525:2\n at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)\n at Actor.<anonymous> (/home/gbusey/actors.js:400:8)\n at increaseSynergy (/home/gbusey/actors.js:701:6)\n
\nThe first line is formatted as <error class name>: <error message>
, and\nis followed by a series of stack frames (each line beginning with \"at \").\nEach frame describes a call site within the code that lead to the error being\ngenerated. V8 attempts to display a name for each function (by variable name,\nfunction name, or object method name), but occasionally it will not be able to\nfind a suitable name. If V8 cannot determine a name for the function, only\nlocation information will be displayed for that frame. Otherwise, the\ndetermined function name will be displayed with location information appended\nin parentheses.
Frames are only generated for JavaScript functions. If, for example, execution\nsynchronously passes through a C++ addon function called cheetahify
which\nitself calls a JavaScript function, the frame representing the cheetahify
call\nwill not be present in the stack traces:
const cheetahify = require('./native-binding.node');\n\nfunction makeFaster() {\n // `cheetahify()` *synchronously* calls speedy.\n cheetahify(function speedy() {\n throw new Error('oh no!');\n });\n}\n\nmakeFaster();\n// will throw:\n// /home/gbusey/file.js:6\n// throw new Error('oh no!');\n// ^\n// Error: oh no!\n// at speedy (/home/gbusey/file.js:6:11)\n// at makeFaster (/home/gbusey/file.js:5:3)\n// at Object.<anonymous> (/home/gbusey/file.js:10:1)\n// at Module._compile (module.js:456:26)\n// at Object.Module._extensions..js (module.js:474:10)\n// at Module.load (module.js:356:32)\n// at Function.Module._load (module.js:312:12)\n// at Function.Module.runMain (module.js:497:10)\n// at startup (node.js:119:16)\n// at node.js:906:3\n
\nThe location information will be one of:
\nnative
, if the frame represents a call internal to V8 (as in [].forEach
).plain-filename.js:line:column
, if the frame represents a call internal\nto Node.js./absolute/path/to/file.js:line:column
, if the frame represents a call in\na user program (using CommonJS module system), or its dependencies.<transport-protocol>:///url/to/module/file.mjs:line:column
, if the frame\nrepresents a call in a user program (using ES module system), or\nits dependencies.The string representing the stack trace is lazily generated when the\nerror.stack
property is accessed.
The number of frames captured by the stack trace is bounded by the smaller of\nError.stackTraceLimit
or the number of available frames on the current event\nloop tick.
Creates a new Error
object and sets the error.message
property to the\nprovided text message. If an object is passed as message
, the text message\nis generated by calling String(message)
. If the cause
option is provided,\nit is assigned to the error.cause
property. The error.stack
property will\nrepresent the point in the code at which new Error()
was called. Stack traces\nare dependent on V8's stack trace API. Stack traces extend only to either\n(a) the beginning of synchronous code execution, or (b) the number of frames\ngiven by the property Error.stackTraceLimit
, whichever is smaller.
Indicates the failure of an assertion. For details, see\nClass: assert.AssertionError
.
Indicates that a provided argument was not within the set or range of\nacceptable values for a function; whether that is a numeric range, or\noutside the set of options for a given function parameter.
\nrequire('node:net').connect(-1);\n// Throws \"RangeError: \"port\" option should be >= 0 and < 65536: -1\"\n
\nNode.js will generate and throw RangeError
instances immediately as a form\nof argument validation.
Indicates that an attempt is being made to access a variable that is not\ndefined. Such errors commonly indicate typos in code, or an otherwise broken\nprogram.
\nWhile client code may generate and propagate these errors, in practice, only V8\nwill do so.
\ndoesNotExist;\n// Throws ReferenceError, doesNotExist is not a variable in this program.\n
\nUnless an application is dynamically generating and running code,\nReferenceError
instances indicate a bug in the code or its dependencies.
Indicates that a program is not valid JavaScript. These errors may only be\ngenerated and propagated as a result of code evaluation. Code evaluation may\nhappen as a result of eval
, Function
, require
, or vm. These errors\nare almost always indicative of a broken program.
try {\n require('node:vm').runInThisContext('binary ! isNotOk');\n} catch (err) {\n // 'err' will be a SyntaxError.\n}\n
\nSyntaxError
instances are unrecoverable in the context that created them –\nthey may only be caught by other contexts.
Node.js generates system errors when exceptions occur within its runtime\nenvironment. These usually occur when an application violates an operating\nsystem constraint. For example, a system error will occur if an application\nattempts to read a file that does not exist.
\naddress
<string> If present, the address to which a network connection\nfailedcode
<string> The string error codedest
<string> If present, the file path destination when reporting a file\nsystem errorerrno
<number> The system-provided error numberinfo
<Object> If present, extra details about the error conditionmessage
<string> A system-provided human-readable description of the errorpath
<string> If present, the file path when reporting a file system errorport
<number> If present, the network connection port that is not availablesyscall
<string> The name of the system call that triggered the errorIf present, error.address
is a string describing the address to which a\nnetwork connection failed.
The error.code
property is a string representing the error code.
If present, error.dest
is the file path destination when reporting a file\nsystem error.
The error.errno
property is a negative number which corresponds\nto the error code defined in libuv Error handling
.
On Windows the error number provided by the system will be normalized by libuv.
\nTo get the string representation of the error code, use\nutil.getSystemErrorName(error.errno)
.
If present, error.info
is an object with details about the error condition.
error.message
is a system-provided human-readable description of the error.
If present, error.path
is a string containing a relevant invalid pathname.
If present, error.port
is the network connection port that is not available.
The error.syscall
property is a string describing the syscall that failed.
This is a list of system errors commonly-encountered when writing a Node.js\nprogram. For a comprehensive list, see the errno
(3) man page.
EACCES
(Permission denied): An attempt was made to access a file in a way\nforbidden by its file access permissions.
EADDRINUSE
(Address already in use): An attempt to bind a server\n(net
, http
, or https
) to a local address failed due to\nanother server on the local system already occupying that address.
ECONNREFUSED
(Connection refused): No connection could be made because the\ntarget machine actively refused it. This usually results from trying to\nconnect to a service that is inactive on the foreign host.
ECONNRESET
(Connection reset by peer): A connection was forcibly closed by\na peer. This normally results from a loss of the connection on the remote\nsocket due to a timeout or reboot. Commonly encountered via the http
\nand net
modules.
EEXIST
(File exists): An existing file was the target of an operation that\nrequired that the target not exist.
EISDIR
(Is a directory): An operation expected a file, but the given\npathname was a directory.
EMFILE
(Too many open files in system): Maximum number of\nfile descriptors allowable on the system has been reached, and\nrequests for another descriptor cannot be fulfilled until at least one\nhas been closed. This is encountered when opening many files at once in\nparallel, especially on systems (in particular, macOS) where there is a low\nfile descriptor limit for processes. To remedy a low limit, run\nulimit -n 2048
in the same shell that will run the Node.js process.
ENOENT
(No such file or directory): Commonly raised by fs
operations\nto indicate that a component of the specified pathname does not exist. No\nentity (file or directory) could be found by the given path.
ENOTDIR
(Not a directory): A component of the given pathname existed, but\nwas not a directory as expected. Commonly raised by fs.readdir
.
ENOTEMPTY
(Directory not empty): A directory with entries was the target\nof an operation that requires an empty directory, usually fs.unlink
.
ENOTFOUND
(DNS lookup failed): Indicates a DNS failure of either\nEAI_NODATA
or EAI_NONAME
. This is not a standard POSIX error.
EPERM
(Operation not permitted): An attempt was made to perform an\noperation that requires elevated privileges.
EPIPE
(Broken pipe): A write on a pipe, socket, or FIFO for which there is\nno process to read the data. Commonly encountered at the net
and\nhttp
layers, indicative that the remote side of the stream being\nwritten to has been closed.
ETIMEDOUT
(Operation timed out): A connect or send request failed because\nthe connected party did not properly respond after a period of time. Usually\nencountered by http
or net
. Often a sign that a socket.end()
\nwas not properly called.
Indicates that a provided argument is not an allowable type. For example,\npassing a function to a parameter which expects a string would be a TypeError
.
require('node:url').parse(() => { });\n// Throws TypeError, since it expected a string.\n
\nNode.js will generate and throw TypeError
instances immediately as a form\nof argument validation.
These objects are available in all modules.
\nThe following variables may appear to be global but are not. They exist only in\nthe scope of CommonJS modules:
\n__dirname
__filename
exports
module
require()
The objects listed here are specific to Node.js. There are built-in objects\nthat are part of the JavaScript language itself, which are also globally\naccessible.
", "globals": [ { "textRaw": "Class: `AbortController`", "type": "global", "name": "AbortController", "meta": { "added": [ "v15.0.0", "v14.17.0" ], "changes": [ { "version": "v15.4.0", "pr-url": "https://github.com/nodejs/node/pull/35949", "description": "No longer experimental." } ] }, "desc": "A utility class used to signal cancelation in selected Promise
-based APIs.\nThe API is based on the Web API AbortController
.
const ac = new AbortController();\n\nac.signal.addEventListener('abort', () => console.log('Aborted!'),\n { once: true });\n\nac.abort();\n\nconsole.log(ac.signal.aborted); // Prints true\n
",
"methods": [
{
"textRaw": "`abortController.abort([reason])`",
"type": "method",
"name": "abort",
"meta": {
"added": [
"v15.0.0",
"v14.17.0"
],
"changes": [
{
"version": [
"v17.2.0",
"v16.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40807",
"description": "Added the new optional reason argument."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`reason` {any} An optional reason, retrievable on the `AbortSignal`'s `reason` property.",
"name": "reason",
"type": "any",
"desc": "An optional reason, retrievable on the `AbortSignal`'s `reason` property."
}
]
}
],
"desc": "Triggers the abort signal, causing the abortController.signal
to emit\nthe 'abort'
event.
The AbortSignal
is used to notify observers when the\nabortController.abort()
method is called.
Returns a new already aborted AbortSignal
.
Returns a new AbortSignal
which will be aborted in delay
milliseconds.
Returns a new AbortSignal
which will be aborted if any of the provided\nsignals are aborted. Its abortSignal.reason
will be set to whichever\none of the signals
caused it to be aborted.
The 'abort'
event is emitted when the abortController.abort()
method\nis called. The callback is invoked with a single object argument with a\nsingle type
property set to 'abort'
:
const ac = new AbortController();\n\n// Use either the onabort property...\nac.signal.onabort = () => console.log('aborted!');\n\n// Or the EventTarget API...\nac.signal.addEventListener('abort', (event) => {\n console.log(event.type); // Prints 'abort'\n}, { once: true });\n\nac.abort();\n
\nThe AbortController
with which the AbortSignal
is associated will only\never trigger the 'abort'
event once. We recommended that code check\nthat the abortSignal.aborted
attribute is false
before adding an 'abort'
\nevent listener.
Any event listeners attached to the AbortSignal
should use the\n{ once: true }
option (or, if using the EventEmitter
APIs to attach a\nlistener, use the once()
method) to ensure that the event listener is\nremoved as soon as the 'abort'
event is handled. Failure to do so may\nresult in memory leaks.
An optional callback function that may be set by user code to be notified\nwhen the abortController.abort()
function has been called.
An optional reason specified when the AbortSignal
was triggered.
const ac = new AbortController();\nac.abort(new Error('boom!'));\nconsole.log(ac.signal.reason); // Error: boom!\n
"
}
],
"methods": [
{
"textRaw": "`abortSignal.throwIfAborted()`",
"type": "method",
"name": "throwIfAborted",
"meta": {
"added": [
"v17.3.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "If abortSignal.aborted
is true
, throws abortSignal.reason
.
See <Blob>.
" }, { "textRaw": "Class: `Buffer`", "type": "global", "name": "Buffer", "meta": { "added": [ "v0.1.103" ], "changes": [] }, "desc": "Used to handle binary data. See the buffer section.
" }, { "textRaw": "`clearImmediate(immediateObject)`", "type": "global", "name": "clearImmediate", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "desc": "clearImmediate
is described in the timers section.
clearInterval
is described in the timers section.
clearTimeout
is described in the timers section.
Used to print to stdout and stderr. See the console
section.
A browser-compatible implementation of the CustomEvent
Web API.
A browser-compatible implementation of the Event
class. See\nEventTarget
and Event
API for more details.
A browser-compatible implementation of the EventTarget
class. See\nEventTarget
and Event
API for more details.
See <File>.
" }, { "textRaw": "`global`", "name": "`global`", "meta": { "added": [ "v0.1.27" ], "changes": [] }, "type": "global", "stability": 3, "stabilityText": "Legacy. Use [`globalThis`][] instead.", "desc": "In browsers, the top-level scope has traditionally been the global scope. This\nmeans that var something
will define a new global variable, except within\nECMAScript modules. In Node.js, this is different. The top-level scope is not\nthe global scope; var something
inside a Node.js module will be local to that\nmodule, regardless of whether it is a CommonJS module or an\nECMAScript module.
The MessageChannel
class. See MessageChannel
for more details.
The MessageEvent
class. See MessageEvent
for more details.
The MessagePort
class. See MessagePort
for more details.
The PerformanceEntry
class. See PerformanceEntry
for more details.
The PerformanceMark
class. See PerformanceMark
for more details.
The PerformanceMeasure
class. See PerformanceMeasure
for more details.
The PerformanceObserver
class. See PerformanceObserver
for more details.
The PerformanceObserverEntryList
class. See\nPerformanceObserverEntryList
for more details.
The PerformanceResourceTiming
class. See PerformanceResourceTiming
for\nmore details.
The process object. See the process
object section.
callback
<Function> Function to be queued.The queueMicrotask()
method queues a microtask to invoke callback
. If\ncallback
throws an exception, the process
object 'uncaughtException'
\nevent will be emitted.
The microtask queue is managed by V8 and may be used in a similar manner to\nthe process.nextTick()
queue, which is managed by Node.js. The\nprocess.nextTick()
queue is always processed before the microtask queue\nwithin each turn of the Node.js event loop.
// Here, `queueMicrotask()` is used to ensure the 'load' event is always\n// emitted asynchronously, and therefore consistently. Using\n// `process.nextTick()` here would result in the 'load' event always emitting\n// before any other promise jobs.\n\nDataHandler.prototype.load = async function load(key) {\n const hit = this._cache.get(key);\n if (hit !== undefined) {\n queueMicrotask(() => {\n this.emit('load', hit);\n });\n return;\n }\n\n const data = await fetchData(key);\n this._cache.set(key, data);\n this.emit('load', data);\n};\n
"
},
{
"textRaw": "`setImmediate(callback[, ...args])`",
"type": "global",
"name": "setImmediate",
"meta": {
"added": [
"v0.9.1"
],
"changes": []
},
"desc": "setImmediate
is described in the timers section.
setInterval
is described in the timers section.
setTimeout
is described in the timers section.
The WHATWG structuredClone
method.
The WHATWG DOMException
class. See DOMException
for more details.
The WHATWG TextDecoder
class. See the TextDecoder
section.
The WHATWG TextEncoder
class. See the TextEncoder
section.
The WHATWG URL
class. See the URL
section.
The WHATWG URLSearchParams
class. See the URLSearchParams
section.
The object that acts as the namespace for all W3C\nWebAssembly related functionality. See the\nMozilla Developer Network for usage and compatibility.
" } ], "classes": [ { "textRaw": "Class: `ByteLengthQueuingStrategy`", "type": "class", "name": "ByteLengthQueuingStrategy", "meta": { "added": [ "v18.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental.", "desc": "A browser-compatible implementation of ByteLengthQueuingStrategy
.
A browser-compatible implementation of CompressionStream
.
A browser-compatible implementation of CountQueuingStrategy
.
A browser-compatible implementation of DecompressionStream
.
A browser-compatible implementation of ReadableByteStreamController
.
A browser-compatible implementation of ReadableStream
.
A browser-compatible implementation of ReadableStreamBYOBReader
.
A browser-compatible implementation of ReadableStreamBYOBRequest
.
A browser-compatible implementation of ReadableStreamDefaultController
.
A browser-compatible implementation of ReadableStreamDefaultReader
.
A browser-compatible implementation of TextDecoderStream
.
A browser-compatible implementation of TextEncoderStream
.
A browser-compatible implementation of TransformStream
.
A browser-compatible implementation of TransformStreamDefaultController
.
A browser-compatible implementation of WritableStream
.
A browser-compatible implementation of WritableStreamDefaultController
.
A browser-compatible implementation of WritableStreamDefaultWriter
.
This variable may appear to be global but is not. See __dirname
.
This variable may appear to be global but is not. See __filename
.
See <BroadcastChannel>.
", "type": "misc", "displayName": "`BroadcastChannel`" }, { "textRaw": "`Crypto`", "name": "`crypto`", "meta": { "added": [ "v17.6.0", "v16.15.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/42083", "description": "No longer behind `--experimental-global-webcrypto` CLI flag." } ] }, "stability": 1, "stabilityText": "Experimental. Disable this API with the [`--no-experimental-global-webcrypto`][] CLI flag.", "desc": "A browser-compatible implementation of <Crypto>. This global is available\nonly if the Node.js binary was compiled with including support for the\nnode:crypto
module.
A browser-compatible implementation of the Web Crypto API.
", "type": "misc", "displayName": "`crypto`" }, { "textRaw": "`CryptoKey`", "name": "`cryptokey`", "meta": { "added": [ "v17.6.0", "v16.15.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/42083", "description": "No longer behind `--experimental-global-webcrypto` CLI flag." } ] }, "stability": 1, "stabilityText": "Experimental. Disable this API with the [`--no-experimental-global-webcrypto`][] CLI flag.", "desc": "A browser-compatible implementation of <CryptoKey>. This global is available\nonly if the Node.js binary was compiled with including support for the\nnode:crypto
module.
This variable may appear to be global but is not. See exports
.
A browser-compatible implementation of the fetch()
function.
A browser-compatible implementation of <FormData>.
", "type": "misc", "displayName": "Class `FormData`" }, { "textRaw": "Class `Headers`", "name": "class_`headers`", "meta": { "added": [ "v17.5.0", "v16.15.0" ], "changes": [ { "version": [ "v21.0.0" ], "pr-url": "https://github.com/nodejs/node/pull/45684", "description": "No longer experimental." }, { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41811", "description": "No longer behind `--experimental-fetch` CLI flag." } ] }, "stability": 2, "stabilityText": "Stable", "desc": "A browser-compatible implementation of <Headers>.
", "type": "misc", "displayName": "Class `Headers`" }, { "textRaw": "`module`", "name": "`module`", "desc": "This variable may appear to be global but is not. See module
.
A partial implementation of the Navigator API.
", "type": "misc", "displayName": "`Navigator`" }, { "textRaw": "`navigator`", "name": "`navigator`", "meta": { "added": [ "v21.0.0" ], "changes": [] }, "stability": 1, "stabilityText": ".1 - Active development. Disable this API with the [`--no-experimental-global-navigator`][] CLI flag.", "desc": "A partial implementation of window.navigator
.
The navigator.hardwareConcurrency
read-only property returns the number of\nlogical processors available to the current Node.js instance.
console.log(`This process is running on ${navigator.hardwareConcurrency} logical processors`);\n
"
},
{
"textRaw": "`language` {string}",
"type": "string",
"name": "language",
"meta": {
"added": [
"v21.2.0"
],
"changes": []
},
"desc": "The navigator.language
read-only property returns a string representing the\npreferred language of the Node.js instance. The language will be determined by\nthe ICU library used by Node.js at runtime based on the\ndefault language of the operating system.
The value is representing the language version as defined in RFC 5646.
\nThe fallback value on builds without ICU is 'en-US'
.
console.log(`The preferred language of the Node.js instance has the tag '${navigator.language}'`);\n
"
},
{
"textRaw": "`languages` {ArrayThe navigator.languages
read-only property returns an array of strings\nrepresenting the preferred languages of the Node.js instance.\nBy default navigator.languages
contains only the value of\nnavigator.language
, which will be determined by the ICU library used by\nNode.js at runtime based on the default language of the operating system.
The fallback value on builds without ICU is ['en-US']
.
console.log(`The preferred languages are '${navigator.languages}'`);\n
"
},
{
"textRaw": "`platform` {string}",
"type": "string",
"name": "platform",
"meta": {
"added": [
"v21.2.0"
],
"changes": []
},
"desc": "The navigator.platform
read-only property returns a string identifying the\nplatform on which the Node.js instance is running.
console.log(`This process is running on ${navigator.platform}`);\n
"
},
{
"textRaw": "`userAgent` {string}",
"type": "string",
"name": "userAgent",
"meta": {
"added": [
"v21.1.0"
],
"changes": []
},
"desc": "The navigator.userAgent
read-only property returns user agent\nconsisting of the runtime name and major version number.
console.log(`The user-agent is ${navigator.userAgent}`); // Prints \"Node.js/21\"\n
"
}
],
"type": "misc",
"displayName": "`navigator`"
},
{
"textRaw": "`performance`",
"name": "`performance`",
"meta": {
"added": [
"v16.0.0"
],
"changes": []
},
"desc": "The perf_hooks.performance
object.
A browser-compatible implementation of <Response>.
", "type": "misc", "displayName": "`Response`" }, { "textRaw": "`Request`", "name": "`request`", "meta": { "added": [ "v17.5.0", "v16.15.0" ], "changes": [ { "version": [ "v21.0.0" ], "pr-url": "https://github.com/nodejs/node/pull/45684", "description": "No longer experimental." }, { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41811", "description": "No longer behind `--experimental-fetch` CLI flag." } ] }, "stability": 2, "stabilityText": "Stable", "desc": "A browser-compatible implementation of <Request>.
", "type": "misc", "displayName": "`Request`" }, { "textRaw": "`SubtleCrypto`", "name": "`subtlecrypto`", "meta": { "added": [ "v17.6.0", "v16.15.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/42083", "description": "No longer behind `--experimental-global-webcrypto` CLI flag." } ] }, "stability": 1, "stabilityText": "Experimental. Disable this API with the [`--no-experimental-global-webcrypto`][] CLI flag.", "desc": "A browser-compatible implementation of <SubtleCrypto>. This global is available\nonly if the Node.js binary was compiled with including support for the\nnode:crypto
module.
A browser-compatible implementation of WebSocket
. Enable this API\nwith the --experimental-websocket
CLI flag.
Global alias for buffer.atob()
.
Global alias for buffer.btoa()
.
This variable may appear to be global but is not. See require()
.
Node.js has many features that make it easier to write internationalized\nprograms. Some of them are:
\nIntl
objectString.prototype.localeCompare()
and\nDate.prototype.toLocaleString()
require('node:buffer').transcode()
require('node:util').TextDecoder
RegExp
Unicode Property EscapesNode.js and the underlying V8 engine use\nInternational Components for Unicode (ICU) to implement these features\nin native C/C++ code. The full ICU data set is provided by Node.js by default.\nHowever, due to the size of the ICU data file, several\noptions are provided for customizing the ICU data set either when\nbuilding or running Node.js.
", "miscs": [ { "textRaw": "Options for building Node.js", "name": "options_for_building_node.js", "desc": "To control how ICU is used in Node.js, four configure
options are available\nduring compilation. Additional details on how to compile Node.js are documented\nin BUILDING.md.
--with-intl=none
/--without-intl
--with-intl=system-icu
--with-intl=small-icu
--with-intl=full-icu
(default)An overview of available Node.js and JavaScript features for each configure
\noption:
Feature | \nnone | \nsystem-icu | \nsmall-icu | \nfull-icu | \n
---|---|---|---|---|
String.prototype.normalize() | \nnone (function is no-op) | \nfull | \nfull | \nfull | \n
String.prototype.to*Case() | \nfull | \nfull | \nfull | \nfull | \n
Intl | \nnone (object does not exist) | \npartial/full (depends on OS) | \npartial (English-only) | \nfull | \n
String.prototype.localeCompare() | \npartial (not locale-aware) | \nfull | \nfull | \nfull | \n
String.prototype.toLocale*Case() | \npartial (not locale-aware) | \nfull | \nfull | \nfull | \n
Number.prototype.toLocaleString() | \npartial (not locale-aware) | \npartial/full (depends on OS) | \npartial (English-only) | \nfull | \n
Date.prototype.toLocale*String() | \npartial (not locale-aware) | \npartial/full (depends on OS) | \npartial (English-only) | \nfull | \n
Legacy URL Parser | \npartial (no IDN support) | \nfull | \nfull | \nfull | \n
WHATWG URL Parser | \npartial (no IDN support) | \nfull | \nfull | \nfull | \n
require('node:buffer').transcode() | \nnone (function does not exist) | \nfull | \nfull | \nfull | \n
REPL | \npartial (inaccurate line editing) | \nfull | \nfull | \nfull | \n
require('node:util').TextDecoder | \npartial (basic encodings support) | \npartial/full (depends on OS) | \npartial (Unicode-only) | \nfull | \n
RegExp Unicode Property Escapes | \nnone (invalid RegExp error) | \nfull | \nfull | \nfull | \n
The \"(not locale-aware)\" designation denotes that the function carries out its\noperation just like the non-Locale
version of the function, if one\nexists. For example, under none
mode, Date.prototype.toLocaleString()
's\noperation is identical to that of Date.prototype.toString()
.
If this option is chosen, ICU is disabled and most internationalization\nfeatures mentioned above will be unavailable in the resulting node
binary.
Node.js can link against an ICU build already installed on the system. In fact,\nmost Linux distributions already come with ICU installed, and this option would\nmake it possible to reuse the same set of data used by other components in the\nOS.
\nFunctionalities that only require the ICU library itself, such as\nString.prototype.normalize()
and the WHATWG URL parser, are fully\nsupported under system-icu
. Features that require ICU locale data in\naddition, such as Intl.DateTimeFormat
may be fully or partially\nsupported, depending on the completeness of the ICU data installed on the\nsystem.
This option makes the resulting binary link against the ICU library statically,\nand includes a subset of ICU data (typically only the English locale) within\nthe node
executable.
Functionalities that only require the ICU library itself, such as\nString.prototype.normalize()
and the WHATWG URL parser, are fully\nsupported under small-icu
. Features that require ICU locale data in addition,\nsuch as Intl.DateTimeFormat
, generally only work with the English locale:
const january = new Date(9e8);\nconst english = new Intl.DateTimeFormat('en', { month: 'long' });\nconst spanish = new Intl.DateTimeFormat('es', { month: 'long' });\n\nconsole.log(english.format(january));\n// Prints \"January\"\nconsole.log(spanish.format(january));\n// Prints either \"M01\" or \"January\" on small-icu, depending on the user’s default locale\n// Should print \"enero\"\n
\nThis mode provides a balance between features and binary size.
", "modules": [ { "textRaw": "Providing ICU data at runtime", "name": "providing_icu_data_at_runtime", "desc": "If the small-icu
option is used, one can still provide additional locale data\nat runtime so that the JS methods would work for all ICU locales. Assuming the\ndata file is stored at /runtime/directory/with/dat/file
, it can be made\navailable to ICU through either:
The --with-icu-default-data-dir
configure option:
./configure --with-icu-default-data-dir=/runtime/directory/with/dat/file --with-intl=small-icu\n
\nThis only embeds the default data directory path into the binary.\nThe actual data file is going to be loaded at runtime from this directory\npath.
\nThe NODE_ICU_DATA
environment variable:
env NODE_ICU_DATA=/runtime/directory/with/dat/file node\n
\nThe --icu-data-dir
CLI parameter:
node --icu-data-dir=/runtime/directory/with/dat/file\n
\nWhen more than one of them is specified, the --icu-data-dir
CLI parameter has\nthe highest precedence, then the NODE_ICU_DATA
environment variable, then\nthe --with-icu-default-data-dir
configure option.
ICU is able to automatically find and load a variety of data formats, but the\ndata must be appropriate for the ICU version, and the file correctly named.\nThe most common name for the data file is icudtX[bl].dat
, where X
denotes\nthe intended ICU version, and b
or l
indicates the system's endianness.\nNode.js would fail to load if the expected data file cannot be read from the\nspecified directory. The name of the data file corresponding to the current\nNode.js version can be computed with:
`icudt${process.versions.icu.split('.')[0]}${os.endianness()[0].toLowerCase()}.dat`;\n
\nCheck \"ICU Data\" article in the ICU User Guide for other supported formats\nand more details on ICU data in general.
\nThe full-icu npm module can greatly simplify ICU data installation by\ndetecting the ICU version of the running node
executable and downloading the\nappropriate data file. After installing the module through npm i full-icu
,\nthe data file will be available at ./node_modules/full-icu
. This path can be\nthen passed either to NODE_ICU_DATA
or --icu-data-dir
as shown above to\nenable full Intl
support.
This option makes the resulting binary link against ICU statically and include\na full set of ICU data. A binary created this way has no further external\ndependencies and supports all locales, but might be rather large. This is\nthe default behavior if no --with-intl
flag is passed. The official binaries\nare also built in this mode.
To verify that ICU is enabled at all (system-icu
, small-icu
, or\nfull-icu
), simply checking the existence of Intl
should suffice:
const hasICU = typeof Intl === 'object';\n
\nAlternatively, checking for process.versions.icu
, a property defined only\nwhen ICU is enabled, works too:
const hasICU = typeof process.versions.icu === 'string';\n
\nTo check for support for a non-English locale (i.e. full-icu
or\nsystem-icu
), Intl.DateTimeFormat
can be a good distinguishing factor:
const hasFullICU = (() => {\n try {\n const january = new Date(9e8);\n const spanish = new Intl.DateTimeFormat('es', { month: 'long' });\n return spanish.format(january) === 'enero';\n } catch (err) {\n return false;\n }\n})();\n
\nFor more verbose tests for Intl
support, the following resources may be found\nto be helpful:
Intl
support is\nbuilt correctly.ECMAScript modules are the official standard format to package JavaScript\ncode for reuse. Modules are defined using a variety of import
and\nexport
statements.
The following example of an ES module exports a function:
\n// addTwo.mjs\nfunction addTwo(num) {\n return num + 2;\n}\n\nexport { addTwo };\n
\nThe following example of an ES module imports the function from addTwo.mjs
:
// app.mjs\nimport { addTwo } from './addTwo.mjs';\n\n// Prints: 6\nconsole.log(addTwo(4));\n
\nNode.js fully supports ECMAScript modules as they are currently specified and\nprovides interoperability between them and its original module format,\nCommonJS.
\n\n", "type": "misc", "displayName": "esm" }, { "textRaw": "Enabling", "name": "Enabling", "type": "misc", "desc": "
Node.js has two module systems: CommonJS modules and ECMAScript modules.
\nAuthors can tell Node.js to interpret JavaScript as an ES module via the .mjs
\nfile extension, the package.json
\"type\"
field with a value \"module\"
,\nthe --input-type
flag with a value of \"module\"
, or the\n--experimental-default-type
flag with a value of \"module\"
. These are\nexplicit markers of code being intended to run as an ES module.
Inversely, authors can tell Node.js to interpret JavaScript as CommonJS via the\n.cjs
file extension, the package.json
\"type\"
field with a value\n\"commonjs\"
, the --input-type
flag with a value of \"commonjs\"
, or the\n--experimental-default-type
flag with a value of \"commonjs\"
.
When code lacks explicit markers for either module system, Node.js will inspect\nthe source code of a module to look for ES module syntax. If such syntax is\nfound, Node.js will run the code as an ES module; otherwise it will run the\nmodule as CommonJS. See Determining module system for more details.
\n\n" }, { "textRaw": "Packages", "name": "packages", "desc": "
This section was moved to Modules: Packages.
", "type": "misc", "displayName": "Packages" }, { "textRaw": "`import` Specifiers", "name": "`import`_specifiers", "modules": [ { "textRaw": "Terminology", "name": "terminology", "desc": "The specifier of an import
statement is the string after the from
keyword,\ne.g. 'node:path'
in import { sep } from 'node:path'
. Specifiers are also\nused in export from
statements, and as the argument to an import()
\nexpression.
There are three types of specifiers:
\nRelative specifiers like './startup.js'
or '../config.mjs'
. They refer\nto a path relative to the location of the importing file. The file extension\nis always necessary for these.
Bare specifiers like 'some-package'
or 'some-package/shuffle'
. They can\nrefer to the main entry point of a package by the package name, or a\nspecific feature module within a package prefixed by the package name as per\nthe examples respectively. Including the file extension is only necessary\nfor packages without an \"exports\"
field.
Absolute specifiers like 'file:///opt/nodejs/config.js'
. They refer\ndirectly and explicitly to a full path.
Bare specifier resolutions are handled by the Node.js module\nresolution and loading algorithm.\nAll other specifier resolutions are always only resolved with\nthe standard relative URL resolution semantics.
\nLike in CommonJS, module files within packages can be accessed by appending a\npath to the package name unless the package's package.json
contains an\n\"exports\"
field, in which case files within packages can only be accessed\nvia the paths defined in \"exports\"
.
For details on these package resolution rules that apply to bare specifiers in\nthe Node.js module resolution, see the packages documentation.
", "type": "module", "displayName": "Terminology" }, { "textRaw": "Mandatory file extensions", "name": "mandatory_file_extensions", "desc": "A file extension must be provided when using the import
keyword to resolve\nrelative or absolute specifiers. Directory indexes (e.g. './startup/index.js'
)\nmust also be fully specified.
This behavior matches how import
behaves in browser environments, assuming a\ntypically configured server.
ES modules are resolved and cached as URLs. This means that special characters\nmust be percent-encoded, such as #
with %23
and ?
with %3F
.
file:
, node:
, and data:
URL schemes are supported. A specifier like\n'https://example.com/app.js'
is not supported natively in Node.js unless using\na custom HTTPS loader.
Modules are loaded multiple times if the import
specifier used to resolve\nthem has a different query or fragment.
import './foo.mjs?query=1'; // loads ./foo.mjs with query of \"?query=1\"\nimport './foo.mjs?query=2'; // loads ./foo.mjs with query of \"?query=2\"\n
\nThe volume root may be referenced via /
, //
, or file:///
. Given the\ndifferences between URL and path resolution (such as percent encoding\ndetails), it is recommended to use url.pathToFileURL when importing a path.
data:
URLs are supported for importing with the following MIME types:
text/javascript
for ES modulesapplication/json
for JSONapplication/wasm
for Wasmimport 'data:text/javascript,console.log(\"hello!\");';\nimport _ from 'data:application/json,\"world!\"' with { type: 'json' };\n
\ndata:
URLs only resolve bare specifiers for builtin modules\nand absolute specifiers. Resolving\nrelative specifiers does not work because data:
is not a\nspecial scheme. For example, attempting to load ./foo
\nfrom data:text/javascript,import \"./foo\";
fails to resolve because there\nis no concept of relative resolution for data:
URLs.
node:
URLs are supported as an alternative means to load Node.js builtin\nmodules. This URL scheme allows for builtin modules to be referenced by valid\nabsolute URL strings.
import fs from 'node:fs/promises';\n
\n",
"type": "module",
"displayName": "`node:` imports"
}
],
"type": "module",
"displayName": "URLs"
}
],
"type": "misc",
"displayName": "`import` Specifiers"
},
{
"textRaw": "Import attributes",
"name": "import_attributes",
"meta": {
"added": [
"v17.1.0",
"v16.14.0"
],
"changes": [
{
"version": "v21.0.0",
"pr-url": "https://github.com/nodejs/node/pull/50140",
"description": "Switch from Import Assertions to Import Attributes."
}
]
},
"stability": 1,
"stabilityText": ".1 - Active development",
"desc": "\n\nThis feature was previously named \"Import assertions\", and using the
\nassert
\nkeyword instead ofwith
. Any uses in code of the priorassert
keyword\nshould be updated to usewith
instead.
The Import Attributes proposal adds an inline syntax for module import\nstatements to pass on more information alongside the module specifier.
\nimport fooData from './foo.json' with { type: 'json' };\n\nconst { default: barData } =\n await import('./bar.json', { with: { type: 'json' } });\n
\nNode.js supports the following type
values, for which the attribute is\nmandatory:
Attribute type | \nNeeded for | \n
---|---|
'json' | \nJSON modules | \n
Core modules provide named exports of their public API. A\ndefault export is also provided which is the value of the CommonJS exports.\nThe default export can be used for, among other things, modifying the named\nexports. Named exports of builtin modules are updated only by calling\nmodule.syncBuiltinESMExports()
.
import EventEmitter from 'node:events';\nconst e = new EventEmitter();\n
\nimport { readFile } from 'node:fs';\nreadFile('./foo.txt', (err, source) => {\n if (err) {\n console.error(err);\n } else {\n console.log(source);\n }\n});\n
\nimport fs, { readFileSync } from 'node:fs';\nimport { syncBuiltinESMExports } from 'node:module';\nimport { Buffer } from 'node:buffer';\n\nfs.readFileSync = () => Buffer.from('Hello, ESM');\nsyncBuiltinESMExports();\n\nfs.readFileSync === readFileSync;\n
",
"type": "misc",
"displayName": "Builtin modules"
},
{
"textRaw": "`import()` expressions",
"name": "`import()`_expressions",
"desc": "Dynamic import()
is supported in both CommonJS and ES modules. In CommonJS\nmodules it can be used to load ES modules.
An import
statement can reference an ES module or a CommonJS module.\nimport
statements are permitted only in ES modules, but dynamic import()
\nexpressions are supported in CommonJS for loading ES modules.
When importing CommonJS modules, the\nmodule.exports
object is provided as the default export. Named exports may be\navailable, provided by static analysis as a convenience for better ecosystem\ncompatibility.
The CommonJS module require
always treats the files it references as CommonJS.
Using require
to load an ES module is not supported because ES modules have\nasynchronous execution. Instead, use import()
to load an ES module\nfrom a CommonJS module.
CommonJS modules consist of a module.exports
object which can be of any type.
When importing a CommonJS module, it can be reliably imported using the ES\nmodule default import or its corresponding sugar syntax:
\n\nimport { default as cjs } from 'cjs';\n\n// The following import statement is \"syntax sugar\" (equivalent but sweeter)\n// for `{ default as cjsSugar }` in the above import statement:\nimport cjsSugar from 'cjs';\n\nconsole.log(cjs);\nconsole.log(cjs === cjsSugar);\n// Prints:\n// <module.exports>\n// true\n
\nThe ECMAScript Module Namespace representation of a CommonJS module is always\na namespace with a default
export key pointing to the CommonJS\nmodule.exports
value.
This Module Namespace Exotic Object can be directly observed either when using\nimport * as m from 'cjs'
or a dynamic import:
import * as m from 'cjs';\nconsole.log(m);\nconsole.log(m === await import('cjs'));\n// Prints:\n// [Module] { default: <module.exports> }\n// true\n
\nFor better compatibility with existing usage in the JS ecosystem, Node.js\nin addition attempts to determine the CommonJS named exports of every imported\nCommonJS module to provide them as separate ES module exports using a static\nanalysis process.
\nFor example, consider a CommonJS module written:
\n// cjs.cjs\nexports.name = 'exported';\n
\nThe preceding module supports named imports in ES modules:
\n\nimport { name } from './cjs.cjs';\nconsole.log(name);\n// Prints: 'exported'\n\nimport cjs from './cjs.cjs';\nconsole.log(cjs);\n// Prints: { name: 'exported' }\n\nimport * as m from './cjs.cjs';\nconsole.log(m);\n// Prints: [Module] { default: { name: 'exported' }, name: 'exported' }\n
\nAs can be seen from the last example of the Module Namespace Exotic Object being\nlogged, the name
export is copied off of the module.exports
object and set\ndirectly on the ES module namespace when the module is imported.
Live binding updates or new exports added to module.exports
are not detected\nfor these named exports.
The detection of named exports is based on common syntax patterns but does not\nalways correctly detect named exports. In these cases, using the default\nimport form described above can be a better option.
\nNamed exports detection covers many common export patterns, reexport patterns\nand build tool and transpiler outputs. See cjs-module-lexer for the exact\nsemantics implemented.
", "type": "module", "displayName": "CommonJS Namespaces" }, { "textRaw": "Differences between ES modules and CommonJS", "name": "differences_between_es_modules_and_commonjs", "modules": [ { "textRaw": "No `require`, `exports`, or `module.exports`", "name": "no_`require`,_`exports`,_or_`module.exports`", "desc": "In most cases, the ES module import
can be used to load CommonJS modules.
If needed, a require
function can be constructed within an ES module using\nmodule.createRequire()
.
These CommonJS variables are not available in ES modules.
\n__filename
and __dirname
use cases can be replicated via\nimport.meta.filename
and import.meta.dirname
.
Addons are not currently supported with ES module imports.
\nThey can instead be loaded with module.createRequire()
or\nprocess.dlopen
.
Relative resolution can be handled via new URL('./local', import.meta.url)
.
For a complete require.resolve
replacement, there is the\nimport.meta.resolve API.
Alternatively module.createRequire()
can be used.
NODE_PATH
is not part of resolving import
specifiers. Please use symlinks\nif this behavior is desired.
require.extensions
is not used by import
. Module customization hooks can\nprovide a replacement.
require.cache
is not used by import
as the ES module loader has its own\nseparate cache.
", "type": "module", "displayName": "No `require.cache`" } ], "type": "module", "displayName": "Differences between ES modules and CommonJS" } ], "type": "misc", "displayName": "Interoperability with CommonJS" }, { "textRaw": "JSON modules", "name": "json_modules", "stability": 1, "stabilityText": "Experimental", "desc": "
JSON files can be referenced by import
:
import packageConfig from './package.json' with { type: 'json' };\n
\nThe with { type: 'json' }
syntax is mandatory; see Import Attributes.
The imported JSON only exposes a default
export. There is no support for named\nexports. A cache entry is created in the CommonJS cache to avoid duplication.\nThe same object is returned in CommonJS if the JSON module has already been\nimported from the same path.
", "type": "misc", "displayName": "JSON modules" }, { "textRaw": "Wasm modules", "name": "wasm_modules", "stability": 1, "stabilityText": "Experimental", "desc": "
Importing WebAssembly modules is supported under the\n--experimental-wasm-modules
flag, allowing any .wasm
files to be\nimported as normal modules while also supporting their module imports.
This integration is in line with the\nES Module Integration Proposal for WebAssembly.
\nFor example, an index.mjs
containing:
import * as M from './module.wasm';\nconsole.log(M);\n
\nexecuted under:
\nnode --experimental-wasm-modules index.mjs\n
\nwould provide the exports interface for the instantiation of module.wasm
.
", "type": "misc", "displayName": "Wasm modules" }, { "textRaw": "Top-level `await`", "name": "top-level_`await`", "meta": { "added": [ "v14.8.0" ], "changes": [] }, "desc": "
The await
keyword may be used in the top level body of an ECMAScript module.
Assuming an a.mjs
with
export const five = await Promise.resolve(5);\n
\nAnd a b.mjs
with
import { five } from './a.mjs';\n\nconsole.log(five); // Logs `5`\n
\nnode b.mjs # works\n
\nIf a top level await
expression never resolves, the node
process will exit\nwith a 13
status code.
import { spawn } from 'node:child_process';\nimport { execPath } from 'node:process';\n\nspawn(execPath, [\n '--input-type=module',\n '--eval',\n // Never-resolving Promise:\n 'await new Promise(() => {})',\n]).once('exit', (code) => {\n console.log(code); // Logs `13`\n});\n
",
"type": "misc",
"displayName": "Top-level `await`"
},
{
"textRaw": "HTTPS and HTTP imports",
"name": "https_and_http_imports",
"stability": 1,
"stabilityText": "Experimental",
"desc": "Importing network based modules using https:
and http:
is supported under\nthe --experimental-network-imports
flag. This allows web browser-like imports\nto work in Node.js with a few differences due to application stability and\nsecurity concerns that are different when running in a privileged environment\ninstead of a browser sandbox.
Automatic protocol negotiation for HTTP/2 and HTTP/3 is not yet supported.
", "type": "module", "displayName": "Imports are limited to HTTP/1" }, { "textRaw": "HTTP is limited to loopback addresses", "name": "http_is_limited_to_loopback_addresses", "desc": "http:
is vulnerable to man-in-the-middle attacks and is not allowed to be\nused for addresses outside of the IPv4 address 127.0.0.0/8
(127.0.0.1
to\n127.255.255.255
) and the IPv6 address ::1
. Support for http:
is intended\nto be used for local development.
Authorization
, Cookie
, and Proxy-Authorization
headers are not sent to the\nserver. Avoid including user info in parts of imported URLs. A security model\nfor safely using these on the server is being worked on.
CORS is designed to allow a server to limit the consumers of an API to a\nspecific set of hosts. This is not supported as it does not make sense for a\nserver-based implementation.
", "type": "module", "displayName": "CORS is never checked on the destination server" }, { "textRaw": "Cannot load non-network dependencies", "name": "cannot_load_non-network_dependencies", "desc": "These modules cannot access other modules that are not over http:
or https:
.\nTo still access local modules while avoiding the security concern, pass in\nreferences to the local dependencies:
// file.mjs\nimport worker_threads from 'node:worker_threads';\nimport { configure, resize } from 'https://example.com/imagelib.mjs';\nconfigure({ worker_threads });\n
\n// https://example.com/imagelib.mjs\nlet worker_threads;\nexport function configure(opts) {\n worker_threads = opts.worker_threads;\n}\nexport function resize(img, size) {\n // Perform resizing in worker_thread to avoid main thread blocking\n}\n
",
"type": "module",
"displayName": "Cannot load non-network dependencies"
},
{
"textRaw": "Network-based loading is not enabled by default",
"name": "network-based_loading_is_not_enabled_by_default",
"desc": "For now, the --experimental-network-imports
flag is required to enable loading\nresources over http:
or https:
. In the future, a different mechanism will be\nused to enforce this. Opt-in is required to prevent transitive dependencies\ninadvertently using potentially mutable state that could affect reliability\nof Node.js applications.
", "type": "module", "displayName": "Network-based loading is not enabled by default" } ], "type": "misc", "displayName": "HTTPS and HTTP imports" }, { "textRaw": "Loaders", "name": "loaders", "desc": "
The former Loaders documentation is now at\nModules: Customization hooks.
", "type": "misc", "displayName": "Loaders" }, { "textRaw": "Resolution and loading algorithm", "name": "resolution_and_loading_algorithm", "modules": [ { "textRaw": "Features", "name": "features", "desc": "The default resolver has the following properties:
\nThe default loader has the following properties
\nnode:
URLsdata:
URLsfile:
module loadingfile:
loading\n(supports only .cjs
, .js
, and .mjs
)The algorithm to load an ES module specifier is given through the\nESM_RESOLVE method below. It returns the resolved URL for a\nmodule specifier relative to a parentURL.
\nThe resolution algorithm determines the full resolved URL for a module\nload, along with its suggested module format. The resolution algorithm\ndoes not determine whether the resolved URL protocol can be loaded,\nor whether the file extensions are permitted, instead these validations\nare applied by Node.js during the load phase\n(for example, if it was asked to load a URL that has a protocol that is\nnot file:
, data:
, node:
, or if --experimental-network-imports
\nis enabled, https:
).
The algorithm also tries to determine the format of the file based\non the extension (see ESM_FILE_FORMAT
algorithm below). If it does\nnot recognize the file extension (eg if it is not .mjs
, .cjs
, or\n.json
), then a format of undefined
is returned,\nwhich will throw during the load phase.
The algorithm to determine the module format of a resolved URL is\nprovided by ESM_FILE_FORMAT, which returns the unique module\nformat for any file. The \"module\" format is returned for an ECMAScript\nModule, while the \"commonjs\" format is used to indicate loading through the\nlegacy CommonJS loader. Additional formats such as \"addon\" can be extended in\nfuture updates.
\nIn the following algorithms, all subroutine errors are propagated as errors\nof these top-level routines unless stated otherwise.
\ndefaultConditions is the conditional environment name array,\n[\"node\", \"import\"]
.
The resolver can throw the following errors:
\nESM_RESOLVE(specifier, parentURL)
\n\n\n\n
\n- Let resolved be undefined.
\n- If specifier is a valid URL, then\n
\n\n
\n- Set resolved to the result of parsing and reserializing\nspecifier as a URL.
\n- Otherwise, if specifier starts with \"/\", \"./\", or \"../\", then\n
\n\n
\n- Set resolved to the URL resolution of specifier relative to\nparentURL.
\n- Otherwise, if specifier starts with \"#\", then\n
\n\n
\n- Set resolved to the result of\nPACKAGE_IMPORTS_RESOLVE(specifier,\nparentURL, defaultConditions).
\n- Otherwise,\n
\n\n
\n- Note: specifier is now a bare specifier.
\n- Set resolved the result of\nPACKAGE_RESOLVE(specifier, parentURL).
\n- Let format be undefined.
\n- If resolved is a \"file:\" URL, then\n
\n\n
\n- If resolved contains any percent encodings of \"/\" or \"\\\" (\"%2F\"\nand \"%5C\" respectively), then\n
\n\n
\n- Throw an Invalid Module Specifier error.
\n- If the file at resolved is a directory, then\n
\n\n
\n- Throw an Unsupported Directory Import error.
\n- If the file at resolved does not exist, then\n
\n\n
\n- Throw a Module Not Found error.
\n- Set resolved to the real path of resolved, maintaining the\nsame URL querystring and fragment components.
\n- Set format to the result of ESM_FILE_FORMAT(resolved).
\n- Otherwise,\n
\n\n
\n- Set format the module format of the content type associated with the\nURL resolved.
\n- Return format and resolved to the loading phase
\n
PACKAGE_RESOLVE(packageSpecifier, parentURL)
\n\n\n\n
\n- Let packageName be undefined.
\n- If packageSpecifier is an empty string, then\n
\n\n
\n- Throw an Invalid Module Specifier error.
\n- If packageSpecifier is a Node.js builtin module name, then\n
\n\n
\n- Return the string \"node:\" concatenated with packageSpecifier.
\n- If packageSpecifier does not start with \"@\", then\n
\n\n
\n- Set packageName to the substring of packageSpecifier until the first\n\"/\" separator or the end of the string.
\n- Otherwise,\n
\n\n
\n- If packageSpecifier does not contain a \"/\" separator, then\n
\n\n
\n- Throw an Invalid Module Specifier error.
\n- Set packageName to the substring of packageSpecifier\nuntil the second \"/\" separator or the end of the string.
\n- If packageName starts with \".\" or contains \"\\\" or \"%\", then\n
\n\n
\n- Throw an Invalid Module Specifier error.
\n- Let packageSubpath be \".\" concatenated with the substring of\npackageSpecifier from the position at the length of packageName.
\n- If packageSubpath ends in \"/\", then\n
\n\n
\n- Throw an Invalid Module Specifier error.
\n- Let selfUrl be the result of\nPACKAGE_SELF_RESOLVE(packageName, packageSubpath, parentURL).
\n- If selfUrl is not undefined, return selfUrl.
\n- While parentURL is not the file system root,\n
\n\n
\n- Let packageURL be the URL resolution of \"node_modules/\"\nconcatenated with packageSpecifier, relative to parentURL.
\n- Set parentURL to the parent folder URL of parentURL.
\n- If the folder at packageURL does not exist, then\n
\n\n
\n- Continue the next loop iteration.
\n- Let pjson be the result of READ_PACKAGE_JSON(packageURL).
\n- If pjson is not null and pjson.exports is not null or\nundefined, then\n
\n\n
\n- Return the result of PACKAGE_EXPORTS_RESOLVE(packageURL,\npackageSubpath, pjson.exports, defaultConditions).
\n- Otherwise, if packageSubpath is equal to \".\", then\n
\n\n
\n- If pjson.main is a string, then\n
\n\n
\n- Return the URL resolution of main in packageURL.
\n- Otherwise,\n
\n\n
\n- Return the URL resolution of packageSubpath in packageURL.
\n- Throw a Module Not Found error.
\n
PACKAGE_SELF_RESOLVE(packageName, packageSubpath, parentURL)
\n\n\n\n
\n- Let packageURL be the result of LOOKUP_PACKAGE_SCOPE(parentURL).
\n- If packageURL is null, then\n
\n\n
\n- Return undefined.
\n- Let pjson be the result of READ_PACKAGE_JSON(packageURL).
\n- If pjson is null or if pjson.exports is null or\nundefined, then\n
\n\n
\n- Return undefined.
\n- If pjson.name is equal to packageName, then\n
\n\n
\n- Return the result of PACKAGE_EXPORTS_RESOLVE(packageURL,\npackageSubpath, pjson.exports, defaultConditions).
\n- Otherwise, return undefined.
\n
PACKAGE_EXPORTS_RESOLVE(packageURL, subpath, exports, conditions)
\n\n\n\n
\n- If exports is an Object with both a key starting with \".\" and a key not\nstarting with \".\", throw an Invalid Package Configuration error.
\n- If subpath is equal to \".\", then\n
\n\n
\n- Let mainExport be undefined.
\n- If exports is a String or Array, or an Object containing no keys\nstarting with \".\", then\n
\n\n
\n- Set mainExport to exports.
\n- Otherwise if exports is an Object containing a \".\" property, then\n
\n\n
\n- Set mainExport to exports[\".\"].
\n- If mainExport is not undefined, then\n
\n\n
\n- Let resolved be the result of PACKAGE_TARGET_RESOLVE(\npackageURL, mainExport, null, false, conditions).
\n- If resolved is not null or undefined, return resolved.
\n- Otherwise, if exports is an Object and all keys of exports start with\n\".\", then\n
\n\n
\n- Assert: subpath begins with \"./\".
\n- Let resolved be the result of PACKAGE_IMPORTS_EXPORTS_RESOLVE(\nsubpath, exports, packageURL, false, conditions).
\n- If resolved is not null or undefined, return resolved.
\n- Throw a Package Path Not Exported error.
\n
PACKAGE_IMPORTS_RESOLVE(specifier, parentURL, conditions)
\n\n\n\n
\n- Assert: specifier begins with \"#\".
\n- If specifier is exactly equal to \"#\" or starts with \"#/\", then\n
\n\n
\n- Throw an Invalid Module Specifier error.
\n- Let packageURL be the result of LOOKUP_PACKAGE_SCOPE(parentURL).
\n- If packageURL is not null, then\n
\n\n
\n- Let pjson be the result of READ_PACKAGE_JSON(packageURL).
\n- If pjson.imports is a non-null Object, then\n
\n\n
\n- Let resolved be the result of\nPACKAGE_IMPORTS_EXPORTS_RESOLVE(\nspecifier, pjson.imports, packageURL, true, conditions).
\n- If resolved is not null or undefined, return resolved.
\n- Throw a Package Import Not Defined error.
\n
PACKAGE_IMPORTS_EXPORTS_RESOLVE(matchKey, matchObj, packageURL,\nisImports, conditions)
\n\n\n\n
\n- If matchKey is a key of matchObj and does not contain \"*\", then\n
\n\n
\n- Let target be the value of matchObj[matchKey].
\n- Return the result of PACKAGE_TARGET_RESOLVE(packageURL,\ntarget, null, isImports, conditions).
\n- Let expansionKeys be the list of keys of matchObj containing only a\nsingle \"*\", sorted by the sorting function PATTERN_KEY_COMPARE\nwhich orders in descending order of specificity.
\n- For each key expansionKey in expansionKeys, do\n
\n\n
\n- Let patternBase be the substring of expansionKey up to but excluding\nthe first \"*\" character.
\n- If matchKey starts with but is not equal to patternBase, then\n
\n\n
\n- Let patternTrailer be the substring of expansionKey from the\nindex after the first \"*\" character.
\n- If patternTrailer has zero length, or if matchKey ends with\npatternTrailer and the length of matchKey is greater than or\nequal to the length of expansionKey, then\n
\n\n
\n- Let target be the value of matchObj[expansionKey].
\n- Let patternMatch be the substring of matchKey starting at the\nindex of the length of patternBase up to the length of\nmatchKey minus the length of patternTrailer.
\n- Return the result of PACKAGE_TARGET_RESOLVE(packageURL,\ntarget, patternMatch, isImports, conditions).
\n- Return null.
\n
PATTERN_KEY_COMPARE(keyA, keyB)
\n\n\n\n
\n- Assert: keyA ends with \"/\" or contains only a single \"*\".
\n- Assert: keyB ends with \"/\" or contains only a single \"*\".
\n- Let baseLengthA be the index of \"*\" in keyA plus one, if keyA\ncontains \"*\", or the length of keyA otherwise.
\n- Let baseLengthB be the index of \"*\" in keyB plus one, if keyB\ncontains \"*\", or the length of keyB otherwise.
\n- If baseLengthA is greater than baseLengthB, return -1.
\n- If baseLengthB is greater than baseLengthA, return 1.
\n- If keyA does not contain \"*\", return 1.
\n- If keyB does not contain \"*\", return -1.
\n- If the length of keyA is greater than the length of keyB, return -1.
\n- If the length of keyB is greater than the length of keyA, return 1.
\n- Return 0.
\n
PACKAGE_TARGET_RESOLVE(packageURL, target, patternMatch,\nisImports, conditions)
\n\n\n\n
\n- If target is a String, then\n
\n\n
\n- If target does not start with \"./\", then\n
\n\n
\n- If isImports is false, or if target starts with \"../\" or\n\"/\", or if target is a valid URL, then\n
\n\n
\n- Throw an Invalid Package Target error.
\n- If patternMatch is a String, then\n
\n\n
\n- Return PACKAGE_RESOLVE(target with every instance of \"*\"\nreplaced by patternMatch, packageURL + \"/\").
\n- Return PACKAGE_RESOLVE(target, packageURL + \"/\").
\n- If target split on \"/\" or \"\\\" contains any \"\", \".\", \"..\",\nor \"node_modules\" segments after the first \".\" segment, case\ninsensitive and including percent encoded variants, throw an Invalid\nPackage Target error.
\n- Let resolvedTarget be the URL resolution of the concatenation of\npackageURL and target.
\n- Assert: packageURL is contained in resolvedTarget.
\n- If patternMatch is null, then\n
\n\n
\n- Return resolvedTarget.
\n- If patternMatch split on \"/\" or \"\\\" contains any \"\", \".\",\n\"..\", or \"node_modules\" segments, case insensitive and including\npercent encoded variants, throw an Invalid Module Specifier error.
\n- Return the URL resolution of resolvedTarget with every instance of\n\"*\" replaced with patternMatch.
\n- Otherwise, if target is a non-null Object, then\n
\n\n
\n- If target contains any index property keys, as defined in ECMA-262\n6.1.7 Array Index, throw an Invalid Package Configuration error.
\n- For each property p of target, in object insertion order as,\n
\n\n
\n- If p equals \"default\" or conditions contains an entry for p,\nthen\n
\n\n
\n- Let targetValue be the value of the p property in target.
\n- Let resolved be the result of PACKAGE_TARGET_RESOLVE(\npackageURL, targetValue, patternMatch, isImports,\nconditions).
\n- If resolved is equal to undefined, continue the loop.
\n- Return resolved.
\n- Return undefined.
\n- Otherwise, if target is an Array, then\n
\n\n
\n- If _target.length is zero, return null.
\n- For each item targetValue in target, do\n
\n\n
\n- Let resolved be the result of PACKAGE_TARGET_RESOLVE(\npackageURL, targetValue, patternMatch, isImports,\nconditions), continuing the loop on any Invalid Package Target\nerror.
\n- If resolved is undefined, continue the loop.
\n- Return resolved.
\n- Return or throw the last fallback resolution null return or error.
\n- Otherwise, if target is null, return null.
\n- Otherwise throw an Invalid Package Target error.
\n
ESM_FILE_FORMAT(url)
\n\n\n\n
\n- Assert: url corresponds to an existing file.
\n- If url ends in \".mjs\", then\n
\n\n
\n- Return \"module\".
\n- If url ends in \".cjs\", then\n
\n\n
\n- Return \"commonjs\".
\n- If url ends in \".json\", then\n
\n\n
\n- Return \"json\".
\n- If
\n--experimental-wasm-modules
is enabled and url ends in\n\".wasm\", then\n\n
\n- Return \"wasm\".
\n- Let packageURL be the result of LOOKUP_PACKAGE_SCOPE(url).
\n- Let pjson be the result of READ_PACKAGE_JSON(packageURL).
\n- Let packageType be null.
\n- If pjson?.type is \"module\" or \"commonjs\", then\n
\n\n
\n- Set packageType to pjson.type.
\n- If url ends in \".js\", then\n
\n\n
\n- If packageType is not null, then\n
\n\n
\n- Return packageType.
\n- If
\n--experimental-detect-module
is enabled and the source of\nmodule contains static import or export syntax, then\n\n
\n- Return \"module\".
\n- Return \"commonjs\".
\n- If url does not have any extension, then\n
\n\n
\n- If packageType is \"module\" and
\n--experimental-wasm-modules
is\nenabled and the file at url contains the header for a WebAssembly\nmodule, then\n\n
\n- Return \"wasm\".
\n- If packageType is not null, then\n
\n\n
\n- Return packageType.
\n- If
\n--experimental-detect-module
is enabled and the source of\nmodule contains static import or export syntax, then\n\n
\n- Return \"module\".
\n- Return \"commonjs\".
\n- Return undefined (will throw during load phase).
\n
LOOKUP_PACKAGE_SCOPE(url)
\n\n\n\n
\n- Let scopeURL be url.
\n- While scopeURL is not the file system root,\n
\n\n
\n- Set scopeURL to the parent URL of scopeURL.
\n- If scopeURL ends in a \"node_modules\" path segment, return null.
\n- Let pjsonURL be the resolution of \"package.json\" within\nscopeURL.
\n- if the file at pjsonURL exists, then\n
\n\n
\n- Return scopeURL.
\n- Return null.
\n
READ_PACKAGE_JSON(packageURL)
\n\n", "type": "module", "displayName": "Resolution Algorithm Specification" }, { "textRaw": "Customizing ESM specifier resolution algorithm", "name": "customizing_esm_specifier_resolution_algorithm", "desc": "\n
\n- Let pjsonURL be the resolution of \"package.json\" within packageURL.
\n- If the file at pjsonURL does not exist, then\n
\n\n
\n- Return null.
\n- If the file at packageURL does not parse as valid JSON, then\n
\n\n
\n- Throw an Invalid Package Configuration error.
\n- Return the parsed JSON source of the file at pjsonURL.
\n
Module customization hooks provide a mechanism for customizing the ESM\nspecifier resolution algorithm. An example that provides CommonJS-style\nresolution for ESM specifiers is commonjs-extension-resolution-loader.
\n", "type": "module", "displayName": "Customizing ESM specifier resolution algorithm" } ], "type": "misc", "displayName": "Resolution and loading algorithm" } ], "properties": [ { "textRaw": "`meta` {Object}", "type": "Object", "name": "meta", "desc": "The import.meta
meta property is an Object
that contains the following\nproperties.
\n", "shortDesc": "The directory name of the current module. This is the same as the [`path.dirname()`][] of the [`import.meta.filename`][]." }, { "textRaw": "`filename` {string} The full absolute path and filename of the current module, with", "type": "string", "name": "filename", "meta": { "added": [ "v21.2.0" ], "changes": [] }, "stability": 1, "stabilityText": ".2 - Release candidate", "desc": "Caveat: only present on
\nfile:
modules.
\n", "shortDesc": "The full absolute path and filename of the current module, with" }, { "textRaw": "`url` {string} The absolute `file:` URL of the module.", "type": "string", "name": "url", "desc": "Caveat only local modules support this property. Modules not using the\n
\nfile:
protocol will not provide it.
This is defined exactly the same as it is in browsers providing the URL of the\ncurrent module file.
\nThis enables useful patterns such as relative file loading:
\nimport { readFileSync } from 'node:fs';\nconst buffer = readFileSync(new URL('./data.proto', import.meta.url));\n
",
"shortDesc": "The absolute `file:` URL of the module."
}
],
"methods": [
{
"textRaw": "`import.meta.resolve(specifier)`",
"type": "method",
"name": "resolve",
"meta": {
"added": [
"v13.9.0",
"v12.16.2"
],
"changes": [
{
"version": "v20.6.0",
"pr-url": "https://github.com/nodejs/node/pull/49028",
"description": "Unflag `import.meta.resolve`, with `parentURL` parameter still flagged."
},
{
"version": "v20.6.0",
"pr-url": "https://github.com/nodejs/node/pull/49038",
"description": "This API no longer throws when targeting `file:` URLs that do not map to an existing file on the local FS."
},
{
"version": "v20.0.0",
"pr-url": "https://github.com/nodejs/node/pull/44710",
"description": "This API now returns a string synchronously instead of a Promise."
},
{
"version": [
"v16.2.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/38587",
"description": "Add support for WHATWG `URL` object to `parentURL` parameter."
}
]
},
"stability": 1,
"stabilityText": ".2 - Release candidate",
"signatures": [
{
"return": {
"textRaw": "Returns: {string} The absolute URL string that the specifier would resolve to.",
"name": "return",
"type": "string",
"desc": "The absolute URL string that the specifier would resolve to."
},
"params": [
{
"textRaw": "`specifier` {string} The module specifier to resolve relative to the current module.",
"name": "specifier",
"type": "string",
"desc": "The module specifier to resolve relative to the current module."
}
]
}
],
"desc": "import.meta.resolve
is a module-relative resolution function scoped to\neach module, returning the URL string.
const dependencyAsset = import.meta.resolve('component-lib/asset.css');\n// file:///app/node_modules/component-lib/asset.css\nimport.meta.resolve('./dep.js');\n// file:///app/dep.js\n
\nAll features of the Node.js module resolution are supported. Dependency\nresolutions are subject to the permitted exports resolutions within the package.
\nCaveats:
\nrequire.resolve
.Non-standard API:
\nWhen using the --experimental-import-meta-resolve
flag, that function accepts\na second argument:
parent
<string> | <URL> An optional absolute parent module URL to resolve from.\nDefault: import.meta.url
A package is a folder tree described by a package.json
file. The package\nconsists of the folder containing the package.json
file and all subfolders\nuntil the next folder containing another package.json
file, or a folder\nnamed node_modules
.
This page provides guidance for package authors writing package.json
files\nalong with a reference for the package.json
fields defined by Node.js.
Node.js will treat the following as ES modules when passed to node
as the\ninitial input, or when referenced by import
statements or import()
\nexpressions:
Files with an .mjs
extension.
Files with a .js
extension when the nearest parent package.json
file\ncontains a top-level \"type\"
field with a value of \"module\"
.
Strings passed in as an argument to --eval
, or piped to node
via STDIN
,\nwith the flag --input-type=module
.
When using --experimental-detect-module
, code containing syntax only\nsuccessfully parsed as ES modules, such as import
or export
\nstatements or import.meta
, having no explicit marker of how it should be\ninterpreted. Explicit markers are .mjs
or .cjs
extensions, package.json
\n\"type\"
fields with either \"module\"
or \"commonjs\"
values, or\n--input-type
or --experimental-default-type
flags. Dynamic import()
\nexpressions are supported in either CommonJS or ES modules and would not\ncause a file to be treated as an ES module.
Node.js will treat the following as CommonJS when passed to node
as the\ninitial input, or when referenced by import
statements or import()
\nexpressions:
Files with a .cjs
extension.
Files with a .js
extension when the nearest parent package.json
file\ncontains a top-level field \"type\"
with a value of \"commonjs\"
.
Strings passed in as an argument to --eval
or --print
, or piped to node
\nvia STDIN
, with the flag --input-type=commonjs
.
Aside from these explicit cases, there are other cases where Node.js defaults to\none module system or the other based on the value of the\n--experimental-default-type
flag:
Files ending in .js
or with no extension, if there is no package.json
file\npresent in the same folder or any parent folder.
Files ending in .js
or with no extension, if the nearest parent\npackage.json
field lacks a \"type\"
field; unless the folder is inside a\nnode_modules
folder. (Package scopes under node_modules
are always treated\nas CommonJS when the package.json
file lacks a \"type\"
field, regardless\nof --experimental-default-type
, for backward compatibility.)
Strings passed in as an argument to --eval
or piped to node
via STDIN
,\nwhen --input-type
is unspecified.
This flag currently defaults to \"commonjs\"
, but it may change in the future to\ndefault to \"module\"
. For this reason it is best to be explicit wherever\npossible; in particular, package authors should always include the \"type\"
\nfield in their package.json
files, even in packages where all sources are\nCommonJS. Being explicit about the type
of the package will future-proof the\npackage in case the default type of Node.js ever changes, and it will also make\nthings easier for build tools and loaders to determine how the files in the\npackage should be interpreted.
Node.js has two systems for resolving a specifier and loading modules.
\nThere is the CommonJS module loader:
\nrequire()
calls..js
, .json
, and finally .node
) and then attempt to resolve\nfolders as modules..json
as JSON text files..node
files are interpreted as compiled addon modules loaded with\nprocess.dlopen()
..json
or .node
extensions as JavaScript\ntext files.There is the ECMAScript module loader:
\nimport
statements and import()
expressions.'./startup/index.js'
) must be fully specified..js
, .mjs
, and .cjs
extensions for JavaScript text\nfiles.cjs-module-lexer
to try to identify named exports,\nwhich are available if they can be determined through static analysis.\nImported CommonJS modules have their URLs converted to absolute\npaths and are then loaded via the CommonJS module loader.Within a package, the package.json
\"type\"
field defines how\nNode.js should interpret .js
files. If a package.json
file does not have a\n\"type\"
field, .js
files are treated as CommonJS.
A package.json
\"type\"
value of \"module\"
tells Node.js to interpret .js
\nfiles within that package as using ES module syntax.
The \"type\"
field applies not only to initial entry points (node my-app.js
)\nbut also to files referenced by import
statements and import()
expressions.
// my-app.js, treated as an ES module because there is a package.json\n// file in the same folder with \"type\": \"module\".\n\nimport './startup/init.js';\n// Loaded as ES module since ./startup contains no package.json file,\n// and therefore inherits the \"type\" value from one level up.\n\nimport 'commonjs-package';\n// Loaded as CommonJS since ./node_modules/commonjs-package/package.json\n// lacks a \"type\" field or contains \"type\": \"commonjs\".\n\nimport './node_modules/commonjs-package/index.js';\n// Loaded as CommonJS since ./node_modules/commonjs-package/package.json\n// lacks a \"type\" field or contains \"type\": \"commonjs\".\n
\nFiles ending with .mjs
are always loaded as ES modules regardless of\nthe nearest parent package.json
.
Files ending with .cjs
are always loaded as CommonJS regardless of the\nnearest parent package.json
.
import './legacy-file.cjs';\n// Loaded as CommonJS since .cjs is always loaded as CommonJS.\n\nimport 'commonjs-package/src/index.mjs';\n// Loaded as ES module since .mjs is always loaded as ES module.\n
\nThe .mjs
and .cjs
extensions can be used to mix types within the same\npackage:
Within a \"type\": \"module\"
package, Node.js can be instructed to\ninterpret a particular file as CommonJS by naming it with a .cjs
\nextension (since both .js
and .mjs
files are treated as ES modules within\na \"module\"
package).
Within a \"type\": \"commonjs\"
package, Node.js can be instructed to\ninterpret a particular file as an ES module by naming it with an .mjs
\nextension (since both .js
and .cjs
files are treated as CommonJS within a\n\"commonjs\"
package).
Strings passed in as an argument to --eval
(or -e
), or piped to node
via\nSTDIN
, are treated as ES modules when the --input-type=module
flag\nis set.
node --input-type=module --eval \"import { sep } from 'node:path'; console.log(sep);\"\n\necho \"import { sep } from 'node:path'; console.log(sep);\" | node --input-type=module\n
\nFor completeness there is also --input-type=commonjs
, for explicitly running\nstring input as CommonJS. This is the default behavior if --input-type
is\nunspecified.
While all Node.js projects are expected to be installable by all package\nmanagers once published, their development teams are often required to use one\nspecific package manager. To make this process easier, Node.js ships with a\ntool called Corepack that aims to make all package managers transparently\navailable in your environment - provided you have Node.js installed.
\nBy default Corepack won't enforce any specific package manager and will use\nthe generic \"Last Known Good\" versions associated with each Node.js release,\nbut you can improve this experience by setting the \"packageManager\"
field\nin your project's package.json
.
In a package's package.json
file, two fields can define entry points for a\npackage: \"main\"
and \"exports\"
. Both fields apply to both ES module\nand CommonJS module entry points.
The \"main\"
field is supported in all versions of Node.js, but its\ncapabilities are limited: it only defines the main entry point of the package.
The \"exports\"
provides a modern alternative to \"main\"
allowing\nmultiple entry points to be defined, conditional entry resolution support\nbetween environments, and preventing any other entry points besides those\ndefined in \"exports\"
. This encapsulation allows module authors to\nclearly define the public interface for their package.
For new packages targeting the currently supported versions of Node.js, the\n\"exports\"
field is recommended. For packages supporting Node.js 10 and\nbelow, the \"main\"
field is required. If both \"exports\"
and\n\"main\"
are defined, the \"exports\"
field takes precedence over\n\"main\"
in supported versions of Node.js.
Conditional exports can be used within \"exports\"
to define different\npackage entry points per environment, including whether the package is\nreferenced via require
or via import
. For more information about supporting\nboth CommonJS and ES modules in a single package please consult\nthe dual CommonJS/ES module packages section.
Existing packages introducing the \"exports\"
field will prevent consumers\nof the package from using any entry points that are not defined, including the\npackage.json
(e.g. require('your-package/package.json')
). This will\nlikely be a breaking change.
To make the introduction of \"exports\"
non-breaking, ensure that every\npreviously supported entry point is exported. It is best to explicitly specify\nentry points so that the package's public API is well-defined. For example,\na project that previously exported main
, lib
,\nfeature
, and the package.json
could use the following package.exports
:
{\n \"name\": \"my-package\",\n \"exports\": {\n \".\": \"./lib/index.js\",\n \"./lib\": \"./lib/index.js\",\n \"./lib/index\": \"./lib/index.js\",\n \"./lib/index.js\": \"./lib/index.js\",\n \"./feature\": \"./feature/index.js\",\n \"./feature/index\": \"./feature/index.js\",\n \"./feature/index.js\": \"./feature/index.js\",\n \"./package.json\": \"./package.json\"\n }\n}\n
\nAlternatively a project could choose to export entire folders both with and\nwithout extensioned subpaths using export patterns:
\n{\n \"name\": \"my-package\",\n \"exports\": {\n \".\": \"./lib/index.js\",\n \"./lib\": \"./lib/index.js\",\n \"./lib/*\": \"./lib/*.js\",\n \"./lib/*.js\": \"./lib/*.js\",\n \"./feature\": \"./feature/index.js\",\n \"./feature/*\": \"./feature/*.js\",\n \"./feature/*.js\": \"./feature/*.js\",\n \"./package.json\": \"./package.json\"\n }\n}\n
\nWith the above providing backwards-compatibility for any minor package versions,\na future major change for the package can then properly restrict the exports\nto only the specific feature exports exposed:
\n{\n \"name\": \"my-package\",\n \"exports\": {\n \".\": \"./lib/index.js\",\n \"./feature/*.js\": \"./feature/*.js\",\n \"./feature/internal/*\": null\n }\n}\n
",
"modules": [
{
"textRaw": "Main entry point export",
"name": "main_entry_point_export",
"desc": "When writing a new package, it is recommended to use the \"exports\"
field:
{\n \"exports\": \"./index.js\"\n}\n
\nWhen the \"exports\"
field is defined, all subpaths of the package are\nencapsulated and no longer available to importers. For example,\nrequire('pkg/subpath.js')
throws an ERR_PACKAGE_PATH_NOT_EXPORTED
\nerror.
This encapsulation of exports provides more reliable guarantees\nabout package interfaces for tools and when handling semver upgrades for a\npackage. It is not a strong encapsulation since a direct require of any\nabsolute subpath of the package such as\nrequire('/path/to/node_modules/pkg/subpath.js')
will still load subpath.js
.
All currently supported versions of Node.js and modern build tools support the\n\"exports\"
field. For projects using an older version of Node.js or a related\nbuild tool, compatibility can be achieved by including the \"main\"
field\nalongside \"exports\"
pointing to the same module:
{\n \"main\": \"./index.js\",\n \"exports\": \"./index.js\"\n}\n
",
"type": "module",
"displayName": "Main entry point export"
},
{
"textRaw": "Subpath exports",
"name": "subpath_exports",
"meta": {
"added": [
"v12.7.0"
],
"changes": []
},
"desc": "When using the \"exports\"
field, custom subpaths can be defined along\nwith the main entry point by treating the main entry point as the\n\".\"
subpath:
{\n \"exports\": {\n \".\": \"./index.js\",\n \"./submodule.js\": \"./src/submodule.js\"\n }\n}\n
\nNow only the defined subpath in \"exports\"
can be imported by a consumer:
import submodule from 'es-module-package/submodule.js';\n// Loads ./node_modules/es-module-package/src/submodule.js\n
\nWhile other subpaths will error:
\nimport submodule from 'es-module-package/private-module.js';\n// Throws ERR_PACKAGE_PATH_NOT_EXPORTED\n
",
"modules": [
{
"textRaw": "Extensions in subpaths",
"name": "extensions_in_subpaths",
"desc": "Package authors should provide either extensioned (import 'pkg/subpath.js'
) or\nextensionless (import 'pkg/subpath'
) subpaths in their exports. This ensures\nthat there is only one subpath for each exported module so that all dependents\nimport the same consistent specifier, keeping the package contract clear for\nconsumers and simplifying package subpath completions.
Traditionally, packages tended to use the extensionless style, which has the\nbenefits of readability and of masking the true path of the file within the\npackage.
\nWith import maps now providing a standard for package resolution in browsers\nand other JavaScript runtimes, using the extensionless style can result in\nbloated import map definitions. Explicit file extensions can avoid this issue by\nenabling the import map to utilize a packages folder mapping to map multiple\nsubpaths where possible instead of a separate map entry per package subpath\nexport. This also mirrors the requirement of using the full specifier path\nin relative and absolute import specifiers.
", "type": "module", "displayName": "Extensions in subpaths" } ], "type": "module", "displayName": "Subpath exports" }, { "textRaw": "Exports sugar", "name": "exports_sugar", "meta": { "added": [ "v12.11.0" ], "changes": [] }, "desc": "If the \".\"
export is the only export, the \"exports\"
field provides sugar\nfor this case being the direct \"exports\"
field value.
{\n \"exports\": {\n \".\": \"./index.js\"\n }\n}\n
\ncan be written:
\n{\n \"exports\": \"./index.js\"\n}\n
",
"type": "module",
"displayName": "Exports sugar"
},
{
"textRaw": "Subpath imports",
"name": "subpath_imports",
"meta": {
"added": [
"v14.6.0",
"v12.19.0"
],
"changes": []
},
"desc": "In addition to the \"exports\"
field, there is a package \"imports\"
field\nto create private mappings that only apply to import specifiers from within the\npackage itself.
Entries in the \"imports\"
field must always start with #
to ensure they are\ndisambiguated from external package specifiers.
For example, the imports field can be used to gain the benefits of conditional\nexports for internal modules:
\n// package.json\n{\n \"imports\": {\n \"#dep\": {\n \"node\": \"dep-node-native\",\n \"default\": \"./dep-polyfill.js\"\n }\n },\n \"dependencies\": {\n \"dep-node-native\": \"^1.0.0\"\n }\n}\n
\nwhere import '#dep'
does not get the resolution of the external package\ndep-node-native
(including its exports in turn), and instead gets the local\nfile ./dep-polyfill.js
relative to the package in other environments.
Unlike the \"exports\"
field, the \"imports\"
field permits mapping to external\npackages.
The resolution rules for the imports field are otherwise analogous to the\nexports field.
", "type": "module", "displayName": "Subpath imports" }, { "textRaw": "Subpath patterns", "name": "subpath_patterns", "meta": { "added": [ "v14.13.0", "v12.20.0" ], "changes": [ { "version": [ "v16.10.0", "v14.19.0" ], "pr-url": "https://github.com/nodejs/node/pull/40041", "description": "Support pattern trailers in \"imports\" field." }, { "version": [ "v16.9.0", "v14.19.0" ], "pr-url": "https://github.com/nodejs/node/pull/39635", "description": "Support pattern trailers." } ] }, "desc": "For packages with a small number of exports or imports, we recommend\nexplicitly listing each exports subpath entry. But for packages that have\nlarge numbers of subpaths, this might cause package.json
bloat and\nmaintenance issues.
For these use cases, subpath export patterns can be used instead:
\n// ./node_modules/es-module-package/package.json\n{\n \"exports\": {\n \"./features/*.js\": \"./src/features/*.js\"\n },\n \"imports\": {\n \"#internal/*.js\": \"./src/internal/*.js\"\n }\n}\n
\n*
maps expose nested subpaths as it is a string replacement syntax\nonly.
All instances of *
on the right hand side will then be replaced with this\nvalue, including if it contains any /
separators.
import featureX from 'es-module-package/features/x.js';\n// Loads ./node_modules/es-module-package/src/features/x.js\n\nimport featureY from 'es-module-package/features/y/y.js';\n// Loads ./node_modules/es-module-package/src/features/y/y.js\n\nimport internalZ from '#internal/z.js';\n// Loads ./node_modules/es-module-package/src/internal/z.js\n
\nThis is a direct static matching and replacement without any special handling\nfor file extensions. Including the \"*.js\"
on both sides of the mapping\nrestricts the exposed package exports to only JS files.
The property of exports being statically enumerable is maintained with exports\npatterns since the individual exports for a package can be determined by\ntreating the right hand side target pattern as a **
glob against the list of\nfiles within the package. Because node_modules
paths are forbidden in exports\ntargets, this expansion is dependent on only the files of the package itself.
To exclude private subfolders from patterns, null
targets can be used:
// ./node_modules/es-module-package/package.json\n{\n \"exports\": {\n \"./features/*.js\": \"./src/features/*.js\",\n \"./features/private-internal/*\": null\n }\n}\n
\nimport featureInternal from 'es-module-package/features/private-internal/m.js';\n// Throws: ERR_PACKAGE_PATH_NOT_EXPORTED\n\nimport featureX from 'es-module-package/features/x.js';\n// Loads ./node_modules/es-module-package/src/features/x.js\n
",
"type": "module",
"displayName": "Subpath patterns"
},
{
"textRaw": "Conditional exports",
"name": "conditional_exports",
"meta": {
"added": [
"v13.2.0",
"v12.16.0"
],
"changes": [
{
"version": [
"v13.7.0",
"v12.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/31001",
"description": "Unflag conditional exports."
}
]
},
"desc": "Conditional exports provide a way to map to different paths depending on\ncertain conditions. They are supported for both CommonJS and ES module imports.
\nFor example, a package that wants to provide different ES module exports for\nrequire()
and import
can be written:
// package.json\n{\n \"exports\": {\n \"import\": \"./index-module.js\",\n \"require\": \"./index-require.cjs\"\n },\n \"type\": \"module\"\n}\n
\nNode.js implements the following conditions, listed in order from most\nspecific to least specific as conditions should be defined:
\n\"node-addons\"
- similar to \"node\"
and matches for any Node.js environment.\nThis condition can be used to provide an entry point which uses native C++\naddons as opposed to an entry point which is more universal and doesn't rely\non native addons. This condition can be disabled via the\n--no-addons
flag.\"node\"
- matches for any Node.js environment. Can be a CommonJS or ES\nmodule file. In most cases explicitly calling out the Node.js platform is\nnot necessary.\"import\"
- matches when the package is loaded via import
or\nimport()
, or via any top-level import or resolve operation by the\nECMAScript module loader. Applies regardless of the module format of the\ntarget file. Always mutually exclusive with \"require\"
.\"require\"
- matches when the package is loaded via require()
. The\nreferenced file should be loadable with require()
although the condition\nmatches regardless of the module format of the target file. Expected\nformats include CommonJS, JSON, and native addons but not ES modules as\nrequire()
doesn't support them. Always mutually exclusive with\n\"import\"
.\"default\"
- the generic fallback that always matches. Can be a CommonJS\nor ES module file. This condition should always come last.Within the \"exports\"
object, key order is significant. During condition\nmatching, earlier entries have higher priority and take precedence over later\nentries. The general rule is that conditions should be from most specific to\nleast specific in object order.
Using the \"import\"
and \"require\"
conditions can lead to some hazards,\nwhich are further explained in the dual CommonJS/ES module packages section.
The \"node-addons\"
condition can be used to provide an entry point which\nuses native C++ addons. However, this condition can be disabled via the\n--no-addons
flag. When using \"node-addons\"
, it's recommended to treat\n\"default\"
as an enhancement that provides a more universal entry point, e.g.\nusing WebAssembly instead of a native addon.
Conditional exports can also be extended to exports subpaths, for example:
\n{\n \"exports\": {\n \".\": \"./index.js\",\n \"./feature.js\": {\n \"node\": \"./feature-node.js\",\n \"default\": \"./feature.js\"\n }\n }\n}\n
\nDefines a package where require('pkg/feature.js')
and\nimport 'pkg/feature.js'
could provide different implementations between\nNode.js and other JS environments.
When using environment branches, always include a \"default\"
condition where\npossible. Providing a \"default\"
condition ensures that any unknown JS\nenvironments are able to use this universal implementation, which helps avoid\nthese JS environments from having to pretend to be existing environments in\norder to support packages with conditional exports. For this reason, using\n\"node\"
and \"default\"
condition branches is usually preferable to using\n\"node\"
and \"browser\"
condition branches.
In addition to direct mappings, Node.js also supports nested condition objects.
\nFor example, to define a package that only has dual mode entry points for\nuse in Node.js but not the browser:
\n{\n \"exports\": {\n \"node\": {\n \"import\": \"./feature-node.mjs\",\n \"require\": \"./feature-node.cjs\"\n },\n \"default\": \"./feature.mjs\"\n }\n}\n
\nConditions continue to be matched in order as with flat conditions. If\na nested condition does not have any mapping it will continue checking\nthe remaining conditions of the parent condition. In this way nested\nconditions behave analogously to nested JavaScript if
statements.
When running Node.js, custom user conditions can be added with the\n--conditions
flag:
node --conditions=development index.js\n
\nwhich would then resolve the \"development\"
condition in package imports and\nexports, while resolving the existing \"node\"
, \"node-addons\"
, \"default\"
,\n\"import\"
, and \"require\"
conditions as appropriate.
Any number of custom conditions can be set with repeat flags.
", "type": "module", "displayName": "Resolving user conditions" }, { "textRaw": "Community Conditions Definitions", "name": "community_conditions_definitions", "desc": "Condition strings other than the \"import\"
, \"require\"
, \"node\"
,\n\"node-addons\"
and \"default\"
conditions\nimplemented in Node.js core are ignored by default.
Other platforms may implement other conditions and user conditions can be\nenabled in Node.js via the --conditions
/ -C
flag.
Since custom package conditions require clear definitions to ensure correct\nusage, a list of common known package conditions and their strict definitions\nis provided below to assist with ecosystem coordination.
\n\"types\"
- can be used by typing systems to resolve the typing file for\nthe given export. This condition should always be included first.\"browser\"
- any web browser environment.\"development\"
- can be used to define a development-only environment\nentry point, for example to provide additional debugging context such as\nbetter error messages when running in a development mode. Must always be\nmutually exclusive with \"production\"
.\"production\"
- can be used to define a production environment entry\npoint. Must always be mutually exclusive with \"development\"
.For other runtimes, platform-specific condition key definitions are maintained\nby the WinterCG in the Runtime Keys proposal specification.
\nNew conditions definitions may be added to this list by creating a pull request\nto the Node.js documentation for this section. The requirements for listing\na new condition definition here are that:
\n\"types\"
condition is a good example: It\ndoesn't really belong in the Runtime Keys proposal but is a good fit\nhere in the Node.js docs.The above definitions may be moved to a dedicated conditions registry in due\ncourse.
", "type": "module", "displayName": "Community Conditions Definitions" }, { "textRaw": "Self-referencing a package using its name", "name": "self-referencing_a_package_using_its_name", "meta": { "added": [ "v13.1.0", "v12.16.0" ], "changes": [ { "version": [ "v13.6.0", "v12.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/31002", "description": "Unflag self-referencing a package using its name." } ] }, "desc": "Within a package, the values defined in the package's\npackage.json
\"exports\"
field can be referenced via the package's name.\nFor example, assuming the package.json
is:
// package.json\n{\n \"name\": \"a-package\",\n \"exports\": {\n \".\": \"./index.mjs\",\n \"./foo.js\": \"./foo.js\"\n }\n}\n
\nThen any module in that package can reference an export in the package itself:
\n// ./a-module.mjs\nimport { something } from 'a-package'; // Imports \"something\" from ./index.mjs.\n
\nSelf-referencing is available only if package.json
has \"exports\"
, and\nwill allow importing only what that \"exports\"
(in the package.json
)\nallows. So the code below, given the previous package, will generate a runtime\nerror:
// ./another-module.mjs\n\n// Imports \"another\" from ./m.mjs. Fails because\n// the \"package.json\" \"exports\" field\n// does not provide an export named \"./m.mjs\".\nimport { another } from 'a-package/m.mjs';\n
\nSelf-referencing is also available when using require
, both in an ES module,\nand in a CommonJS one. For example, this code will also work:
// ./a-module.js\nconst { something } = require('a-package/foo.js'); // Loads from ./foo.js.\n
\nFinally, self-referencing also works with scoped packages. For example, this\ncode will also work:
\n// package.json\n{\n \"name\": \"@my/package\",\n \"exports\": \"./index.js\"\n}\n
\n// ./index.js\nmodule.exports = 42;\n
\n// ./other.js\nconsole.log(require('@my/package'));\n
\n$ node other.js\n42\n
",
"type": "module",
"displayName": "Self-referencing a package using its name"
}
],
"type": "misc",
"displayName": "Package entry points"
},
{
"textRaw": "Dual CommonJS/ES module packages",
"name": "dual_commonjs/es_module_packages",
"desc": "Prior to the introduction of support for ES modules in Node.js, it was a common\npattern for package authors to include both CommonJS and ES module JavaScript\nsources in their package, with package.json
\"main\"
specifying the\nCommonJS entry point and package.json
\"module\"
specifying the ES module\nentry point.\nThis enabled Node.js to run the CommonJS entry point while build tools such as\nbundlers used the ES module entry point, since Node.js ignored (and still\nignores) the top-level \"module\"
field.
Node.js can now run ES module entry points, and a package can contain both\nCommonJS and ES module entry points (either via separate specifiers such as\n'pkg'
and 'pkg/es-module'
, or both at the same specifier via Conditional\nexports). Unlike in the scenario where \"module\"
is only used by bundlers,\nor ES module files are transpiled into CommonJS on the fly before evaluation by\nNode.js, the files referenced by the ES module entry point are evaluated as ES\nmodules.
When an application is using a package that provides both CommonJS and ES module\nsources, there is a risk of certain bugs if both versions of the package get\nloaded. This potential comes from the fact that the pkgInstance
created by\nconst pkgInstance = require('pkg')
is not the same as the pkgInstance
\ncreated by import pkgInstance from 'pkg'
(or an alternative main path like\n'pkg/module'
). This is the “dual package hazard,” where two versions of the\nsame package can be loaded within the same runtime environment. While it is\nunlikely that an application or package would intentionally load both versions\ndirectly, it is common for an application to load one version while a dependency\nof the application loads the other version. This hazard can happen because\nNode.js supports intermixing CommonJS and ES modules, and can lead to unexpected\nbehavior.
If the package main export is a constructor, an instanceof
comparison of\ninstances created by the two versions returns false
, and if the export is an\nobject, properties added to one (like pkgInstance.foo = 3
) are not present on\nthe other. This differs from how import
and require
statements work in\nall-CommonJS or all-ES module environments, respectively, and therefore is\nsurprising to users. It also differs from the behavior users are familiar with\nwhen using transpilation via tools like Babel or esm
.
First, the hazard described in the previous section occurs when a package\ncontains both CommonJS and ES module sources and both sources are provided for\nuse in Node.js, either via separate main entry points or exported paths. A\npackage might instead be written where any version of Node.js receives only\nCommonJS sources, and any separate ES module sources the package might contain\nare intended only for other environments such as browsers. Such a package\nwould be usable by any version of Node.js, since import
can refer to CommonJS\nfiles; but it would not provide any of the advantages of using ES module syntax.
A package might also switch from CommonJS to ES module syntax in a breaking\nchange version bump. This has the disadvantage that the\nnewest version of the package would only be usable in ES module-supporting\nversions of Node.js.
\nEvery pattern has tradeoffs, but there are two broad approaches that satisfy the\nfollowing conditions:
\nrequire
and import
.'pkg'
can be used by both require
to\nresolve to a CommonJS file and by import
to resolve to an ES module file.\n(And likewise for exported paths, e.g. 'pkg/feature'
.)import { name } from 'pkg'
rather\nthan import pkg from 'pkg'; pkg.name
.Write the package in CommonJS or transpile ES module sources into CommonJS, and\ncreate an ES module wrapper file that defines the named exports. Using\nConditional exports, the ES module wrapper is used for import
and the\nCommonJS entry point for require
.
// ./node_modules/pkg/package.json\n{\n \"type\": \"module\",\n \"exports\": {\n \"import\": \"./wrapper.mjs\",\n \"require\": \"./index.cjs\"\n }\n}\n
\nThe preceding example uses explicit extensions .mjs
and .cjs
.\nIf your files use the .js
extension, \"type\": \"module\"
will cause such files\nto be treated as ES modules, just as \"type\": \"commonjs\"
would cause them\nto be treated as CommonJS.\nSee Enabling.
// ./node_modules/pkg/index.cjs\nexports.name = 'value';\n
\n// ./node_modules/pkg/wrapper.mjs\nimport cjsModule from './index.cjs';\nexport const name = cjsModule.name;\n
\nIn this example, the name
from import { name } from 'pkg'
is the same\nsingleton as the name
from const { name } = require('pkg')
. Therefore ===
\nreturns true
when comparing the two name
s and the divergent specifier hazard\nis avoided.
If the module is not simply a list of named exports, but rather contains a\nunique function or object export like module.exports = function () { ... }
,\nor if support in the wrapper for the import pkg from 'pkg'
pattern is desired,\nthen the wrapper would instead be written to export the default optionally\nalong with any named exports as well:
import cjsModule from './index.cjs';\nexport const name = cjsModule.name;\nexport default cjsModule;\n
\nThis approach is appropriate for any of the following use cases:
\nutilities
\npackage is used directly in an application, and a utilities-plus
package\nadds a few more functions to utilities
. Because the wrapper exports\nunderlying CommonJS files, it doesn't matter if utilities-plus
is written in\nCommonJS or ES module syntax; it will work either way.A variant of this approach not requiring conditional exports for consumers could\nbe to add an export, e.g. \"./module\"
, to point to an all-ES module-syntax\nversion of the package. This could be used via import 'pkg/module'
by users\nwho are certain that the CommonJS version will not be loaded anywhere in the\napplication, such as by dependencies; or if the CommonJS version can be loaded\nbut doesn't affect the ES module version (for example, because the package is\nstateless):
// ./node_modules/pkg/package.json\n{\n \"type\": \"module\",\n \"exports\": {\n \".\": \"./index.cjs\",\n \"./module\": \"./wrapper.mjs\"\n }\n}\n
",
"type": "module",
"displayName": "Approach #1: Use an ES module wrapper"
},
{
"textRaw": "Approach #2: Isolate state",
"name": "approach_#2:_isolate_state",
"desc": "A package.json
file can define the separate CommonJS and ES module entry\npoints directly:
// ./node_modules/pkg/package.json\n{\n \"type\": \"module\",\n \"exports\": {\n \"import\": \"./index.mjs\",\n \"require\": \"./index.cjs\"\n }\n}\n
\nThis can be done if both the CommonJS and ES module versions of the package are\nequivalent, for example because one is the transpiled output of the other; and\nthe package's management of state is carefully isolated (or the package is\nstateless).
\nThe reason that state is an issue is because both the CommonJS and ES module\nversions of the package might get used within an application; for example, the\nuser's application code could import
the ES module version while a dependency\nrequire
s the CommonJS version. If that were to occur, two copies of the\npackage would be loaded in memory and therefore two separate states would be\npresent. This would likely cause hard-to-troubleshoot bugs.
Aside from writing a stateless package (if JavaScript's Math
were a package,\nfor example, it would be stateless as all of its methods are static), there are\nsome ways to isolate state so that it's shared between the potentially loaded\nCommonJS and ES module instances of the package:
If possible, contain all state within an instantiated object. JavaScript's\nDate
, for example, needs to be instantiated to contain state; if it were a\npackage, it would be used like this:
import Date from 'date';\nconst someDate = new Date();\n// someDate contains state; Date does not\n
\nThe new
keyword isn't required; a package's function can return a new\nobject, or modify a passed-in object, to keep the state external to the\npackage.
Isolate the state in one or more CommonJS files that are shared between the\nCommonJS and ES module versions of the package. For example, if the CommonJS\nand ES module entry points are index.cjs
and index.mjs
, respectively:
// ./node_modules/pkg/index.cjs\nconst state = require('./state.cjs');\nmodule.exports.state = state;\n
\n// ./node_modules/pkg/index.mjs\nimport state from './state.cjs';\nexport {\n state,\n};\n
\nEven if pkg
is used via both require
and import
in an application (for\nexample, via import
in application code and via require
by a dependency)\neach reference of pkg
will contain the same state; and modifying that\nstate from either module system will apply to both.
Any plugins that attach to the package's singleton would need to separately\nattach to both the CommonJS and ES module singletons.
\nThis approach is appropriate for any of the following use cases:
\nEven with isolated state, there is still the cost of possible extra code\nexecution between the CommonJS and ES module versions of a package.
\nAs with the previous approach, a variant of this approach not requiring\nconditional exports for consumers could be to add an export, e.g.\n\"./module\"
, to point to an all-ES module-syntax version of the package:
// ./node_modules/pkg/package.json\n{\n \"type\": \"module\",\n \"exports\": {\n \".\": \"./index.cjs\",\n \"./module\": \"./index.mjs\"\n }\n}\n
",
"type": "module",
"displayName": "Approach #2: Isolate state"
}
],
"type": "module",
"displayName": "Writing dual packages while avoiding or minimizing hazards"
}
],
"type": "misc",
"displayName": "Dual CommonJS/ES module packages"
},
{
"textRaw": "Node.js `package.json` field definitions",
"name": "node.js_`package.json`_field_definitions",
"desc": "This section describes the fields used by the Node.js runtime. Other tools (such\nas npm) use\nadditional fields which are ignored by Node.js and not documented here.
\nThe following fields in package.json
files are used in Node.js:
\"name\"
- Relevant when using named imports within a package. Also used\nby package managers as the name of the package.\"main\"
- The default module when loading the package, if exports is not\nspecified, and in versions of Node.js prior to the introduction of exports.\"packageManager\"
- The package manager recommended when contributing to\nthe package. Leveraged by the Corepack shims.\"type\"
- The package type determining whether to load .js
files as\nCommonJS or ES modules.\"exports\"
- Package exports and conditional exports. When present,\nlimits which submodules can be loaded from within the package.\"imports\"
- Package imports, for use by modules within the package\nitself.{\n \"name\": \"package-name\"\n}\n
\nThe \"name\"
field defines your package's name. Publishing to the\nnpm registry requires a name that satisfies\ncertain requirements.
The \"name\"
field can be used in addition to the \"exports\"
field to\nself-reference a package using its name.
{\n \"main\": \"./index.js\"\n}\n
\nThe \"main\"
field defines the entry point of a package when imported by name\nvia a node_modules
lookup. Its value is a path.
When a package has an \"exports\"
field, this will take precedence over the\n\"main\"
field when importing the package by name.
It also defines the script that is used when the package directory is loaded\nvia require()
.
// This resolves to ./path/to/directory/index.js.\nrequire('./path/to/directory');\n
",
"type": "module",
"displayName": "`\"main\"`"
},
{
"textRaw": "`\"packageManager\"`",
"name": "`\"packagemanager\"`",
"meta": {
"added": [
"v16.9.0",
"v14.19.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "{\n \"packageManager\": \"<package manager name>@<version>\"\n}\n
\nThe \"packageManager\"
field defines which package manager is expected to be\nused when working on the current project. It can be set to any of the\nsupported package managers, and will ensure that your teams use the exact\nsame package manager versions without having to install anything else other than\nNode.js.
This field is currently experimental and needs to be opted-in; check the\nCorepack page for details about the procedure.
", "type": "module", "displayName": "`\"packageManager\"`" }, { "textRaw": "`\"type\"`", "name": "`\"type\"`", "meta": { "added": [ "v12.0.0" ], "changes": [ { "version": [ "v13.2.0", "v12.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/29866", "description": "Unflag `--experimental-modules`." } ] }, "desc": "The \"type\"
field defines the module format that Node.js uses for all\n.js
files that have that package.json
file as their nearest parent.
Files ending with .js
are loaded as ES modules when the nearest parent\npackage.json
file contains a top-level field \"type\"
with a value of\n\"module\"
.
The nearest parent package.json
is defined as the first package.json
found\nwhen searching in the current folder, that folder's parent, and so on up\nuntil a node_modules folder or the volume root is reached.
// package.json\n{\n \"type\": \"module\"\n}\n
\n# In same folder as preceding package.json\nnode my-app.js # Runs as ES module\n
\nIf the nearest parent package.json
lacks a \"type\"
field, or contains\n\"type\": \"commonjs\"
, .js
files are treated as CommonJS. If the volume\nroot is reached and no package.json
is found, .js
files are treated as\nCommonJS.
import
statements of .js
files are treated as ES modules if the nearest\nparent package.json
contains \"type\": \"module\"
.
// my-app.js, part of the same example as above\nimport './startup.js'; // Loaded as ES module because of package.json\n
\nRegardless of the value of the \"type\"
field, .mjs
files are always treated\nas ES modules and .cjs
files are always treated as CommonJS.
{\n \"exports\": \"./index.js\"\n}\n
\nThe \"exports\"
field allows defining the entry points of a package when\nimported by name loaded either via a node_modules
lookup or a\nself-reference to its own name. It is supported in Node.js 12+ as an\nalternative to the \"main\"
that can support defining subpath exports\nand conditional exports while encapsulating internal unexported modules.
Conditional Exports can also be used within \"exports\"
to define different\npackage entry points per environment, including whether the package is\nreferenced via require
or via import
.
All paths defined in the \"exports\"
must be relative file URLs starting with\n./
.
// package.json\n{\n \"imports\": {\n \"#dep\": {\n \"node\": \"dep-node-native\",\n \"default\": \"./dep-polyfill.js\"\n }\n },\n \"dependencies\": {\n \"dep-node-native\": \"^1.0.0\"\n }\n}\n
\nEntries in the imports field must be strings starting with #
.
Package imports permit mapping to external packages.
\nThis field defines subpath imports for the current package.
", "type": "module", "displayName": "`\"imports\"`" } ], "type": "misc", "displayName": "Node.js `package.json` field definitions" } ], "source": "doc/api/packages.md" }, { "textRaw": "Diagnostic report", "name": "report", "introduced_in": "v11.8.0", "type": "misc", "stability": 2, "stabilityText": "Stable", "desc": "Delivers a JSON-formatted diagnostic summary, written to a file.
\nThe report is intended for development, test, and production use, to capture\nand preserve information for problem determination. It includes JavaScript\nand native stack traces, heap statistics, platform information, resource\nusage etc. With the report option enabled, diagnostic reports can be triggered\non unhandled exceptions, fatal errors and user signals, in addition to\ntriggering programmatically through API calls.
\nA complete example report that was generated on an uncaught exception\nis provided below for reference.
\n{\n \"header\": {\n \"reportVersion\": 3,\n \"event\": \"exception\",\n \"trigger\": \"Exception\",\n \"filename\": \"report.20181221.005011.8974.0.001.json\",\n \"dumpEventTime\": \"2018-12-21T00:50:11Z\",\n \"dumpEventTimeStamp\": \"1545371411331\",\n \"processId\": 8974,\n \"cwd\": \"/home/nodeuser/project/node\",\n \"commandLine\": [\n \"/home/nodeuser/project/node/out/Release/node\",\n \"--report-uncaught-exception\",\n \"/home/nodeuser/project/node/test/report/test-exception.js\",\n \"child\"\n ],\n \"nodejsVersion\": \"v12.0.0-pre\",\n \"glibcVersionRuntime\": \"2.17\",\n \"glibcVersionCompiler\": \"2.17\",\n \"wordSize\": \"64 bit\",\n \"arch\": \"x64\",\n \"platform\": \"linux\",\n \"componentVersions\": {\n \"node\": \"12.0.0-pre\",\n \"v8\": \"7.1.302.28-node.5\",\n \"uv\": \"1.24.1\",\n \"zlib\": \"1.2.11\",\n \"ares\": \"1.15.0\",\n \"modules\": \"68\",\n \"nghttp2\": \"1.34.0\",\n \"napi\": \"3\",\n \"llhttp\": \"1.0.1\",\n \"openssl\": \"1.1.0j\"\n },\n \"release\": {\n \"name\": \"node\"\n },\n \"osName\": \"Linux\",\n \"osRelease\": \"3.10.0-862.el7.x86_64\",\n \"osVersion\": \"#1 SMP Wed Mar 21 18:14:51 EDT 2018\",\n \"osMachine\": \"x86_64\",\n \"cpus\": [\n {\n \"model\": \"Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz\",\n \"speed\": 2700,\n \"user\": 88902660,\n \"nice\": 0,\n \"sys\": 50902570,\n \"idle\": 241732220,\n \"irq\": 0\n },\n {\n \"model\": \"Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz\",\n \"speed\": 2700,\n \"user\": 88902660,\n \"nice\": 0,\n \"sys\": 50902570,\n \"idle\": 241732220,\n \"irq\": 0\n }\n ],\n \"networkInterfaces\": [\n {\n \"name\": \"en0\",\n \"internal\": false,\n \"mac\": \"13:10:de:ad:be:ef\",\n \"address\": \"10.0.0.37\",\n \"netmask\": \"255.255.255.0\",\n \"family\": \"IPv4\"\n }\n ],\n \"host\": \"test_machine\"\n },\n \"javascriptStack\": {\n \"message\": \"Error: *** test-exception.js: throwing uncaught Error\",\n \"stack\": [\n \"at myException (/home/nodeuser/project/node/test/report/test-exception.js:9:11)\",\n \"at Object.<anonymous> (/home/nodeuser/project/node/test/report/test-exception.js:12:3)\",\n \"at Module._compile (internal/modules/cjs/loader.js:718:30)\",\n \"at Object.Module._extensions..js (internal/modules/cjs/loader.js:729:10)\",\n \"at Module.load (internal/modules/cjs/loader.js:617:32)\",\n \"at tryModuleLoad (internal/modules/cjs/loader.js:560:12)\",\n \"at Function.Module._load (internal/modules/cjs/loader.js:552:3)\",\n \"at Function.Module.runMain (internal/modules/cjs/loader.js:771:12)\",\n \"at executeUserCode (internal/bootstrap/node.js:332:15)\"\n ]\n },\n \"nativeStack\": [\n {\n \"pc\": \"0x000055b57f07a9ef\",\n \"symbol\": \"report::GetNodeReport(v8::Isolate*, node::Environment*, char const*, char const*, v8::Local<v8::String>, std::ostream&) [./node]\"\n },\n {\n \"pc\": \"0x000055b57f07cf03\",\n \"symbol\": \"report::GetReport(v8::FunctionCallbackInfo<v8::Value> const&) [./node]\"\n },\n {\n \"pc\": \"0x000055b57f1bccfd\",\n \"symbol\": \" [./node]\"\n },\n {\n \"pc\": \"0x000055b57f1be048\",\n \"symbol\": \"v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*) [./node]\"\n },\n {\n \"pc\": \"0x000055b57feeda0e\",\n \"symbol\": \" [./node]\"\n }\n ],\n \"javascriptHeap\": {\n \"totalMemory\": 5660672,\n \"executableMemory\": 524288,\n \"totalCommittedMemory\": 5488640,\n \"availableMemory\": 4341379928,\n \"totalGlobalHandlesMemory\": 8192,\n \"usedGlobalHandlesMemory\": 3136,\n \"usedMemory\": 4816432,\n \"memoryLimit\": 4345298944,\n \"mallocedMemory\": 254128,\n \"externalMemory\": 315644,\n \"peakMallocedMemory\": 98752,\n \"nativeContextCount\": 1,\n \"detachedContextCount\": 0,\n \"doesZapGarbage\": 0,\n \"heapSpaces\": {\n \"read_only_space\": {\n \"memorySize\": 524288,\n \"committedMemory\": 39208,\n \"capacity\": 515584,\n \"used\": 30504,\n \"available\": 485080\n },\n \"new_space\": {\n \"memorySize\": 2097152,\n \"committedMemory\": 2019312,\n \"capacity\": 1031168,\n \"used\": 985496,\n \"available\": 45672\n },\n \"old_space\": {\n \"memorySize\": 2273280,\n \"committedMemory\": 1769008,\n \"capacity\": 1974640,\n \"used\": 1725488,\n \"available\": 249152\n },\n \"code_space\": {\n \"memorySize\": 696320,\n \"committedMemory\": 184896,\n \"capacity\": 152128,\n \"used\": 152128,\n \"available\": 0\n },\n \"map_space\": {\n \"memorySize\": 536576,\n \"committedMemory\": 344928,\n \"capacity\": 327520,\n \"used\": 327520,\n \"available\": 0\n },\n \"large_object_space\": {\n \"memorySize\": 0,\n \"committedMemory\": 0,\n \"capacity\": 1520590336,\n \"used\": 0,\n \"available\": 1520590336\n },\n \"new_large_object_space\": {\n \"memorySize\": 0,\n \"committedMemory\": 0,\n \"capacity\": 0,\n \"used\": 0,\n \"available\": 0\n }\n }\n },\n \"resourceUsage\": {\n \"rss\": \"35766272\",\n \"free_memory\": \"1598337024\",\n \"total_memory\": \"17179869184\",\n \"available_memory\": \"1598337024\",\n \"maxRss\": \"36624662528\",\n \"constrained_memory\": \"36624662528\",\n \"userCpuSeconds\": 0.040072,\n \"kernelCpuSeconds\": 0.016029,\n \"cpuConsumptionPercent\": 5.6101,\n \"userCpuConsumptionPercent\": 4.0072,\n \"kernelCpuConsumptionPercent\": 1.6029,\n \"pageFaults\": {\n \"IORequired\": 0,\n \"IONotRequired\": 4610\n },\n \"fsActivity\": {\n \"reads\": 0,\n \"writes\": 0\n }\n },\n \"uvthreadResourceUsage\": {\n \"userCpuSeconds\": 0.039843,\n \"kernelCpuSeconds\": 0.015937,\n \"cpuConsumptionPercent\": 5.578,\n \"userCpuConsumptionPercent\": 3.9843,\n \"kernelCpuConsumptionPercent\": 1.5937,\n \"fsActivity\": {\n \"reads\": 0,\n \"writes\": 0\n }\n },\n \"libuv\": [\n {\n \"type\": \"async\",\n \"is_active\": true,\n \"is_referenced\": false,\n \"address\": \"0x0000000102910900\",\n \"details\": \"\"\n },\n {\n \"type\": \"timer\",\n \"is_active\": false,\n \"is_referenced\": false,\n \"address\": \"0x00007fff5fbfeab0\",\n \"repeat\": 0,\n \"firesInMsFromNow\": 94403548320796,\n \"expired\": true\n },\n {\n \"type\": \"check\",\n \"is_active\": true,\n \"is_referenced\": false,\n \"address\": \"0x00007fff5fbfeb48\"\n },\n {\n \"type\": \"idle\",\n \"is_active\": false,\n \"is_referenced\": true,\n \"address\": \"0x00007fff5fbfebc0\"\n },\n {\n \"type\": \"prepare\",\n \"is_active\": false,\n \"is_referenced\": false,\n \"address\": \"0x00007fff5fbfec38\"\n },\n {\n \"type\": \"check\",\n \"is_active\": false,\n \"is_referenced\": false,\n \"address\": \"0x00007fff5fbfecb0\"\n },\n {\n \"type\": \"async\",\n \"is_active\": true,\n \"is_referenced\": false,\n \"address\": \"0x000000010188f2e0\"\n },\n {\n \"type\": \"tty\",\n \"is_active\": false,\n \"is_referenced\": true,\n \"address\": \"0x000055b581db0e18\",\n \"width\": 204,\n \"height\": 55,\n \"fd\": 17,\n \"writeQueueSize\": 0,\n \"readable\": true,\n \"writable\": true\n },\n {\n \"type\": \"signal\",\n \"is_active\": true,\n \"is_referenced\": false,\n \"address\": \"0x000055b581d80010\",\n \"signum\": 28,\n \"signal\": \"SIGWINCH\"\n },\n {\n \"type\": \"tty\",\n \"is_active\": true,\n \"is_referenced\": true,\n \"address\": \"0x000055b581df59f8\",\n \"width\": 204,\n \"height\": 55,\n \"fd\": 19,\n \"writeQueueSize\": 0,\n \"readable\": true,\n \"writable\": true\n },\n {\n \"type\": \"loop\",\n \"is_active\": true,\n \"address\": \"0x000055fc7b2cb180\",\n \"loopIdleTimeSeconds\": 22644.8\n }\n ],\n \"workers\": [],\n \"environmentVariables\": {\n \"REMOTEHOST\": \"REMOVED\",\n \"MANPATH\": \"/opt/rh/devtoolset-3/root/usr/share/man:\",\n \"XDG_SESSION_ID\": \"66126\",\n \"HOSTNAME\": \"test_machine\",\n \"HOST\": \"test_machine\",\n \"TERM\": \"xterm-256color\",\n \"SHELL\": \"/bin/csh\",\n \"SSH_CLIENT\": \"REMOVED\",\n \"PERL5LIB\": \"/opt/rh/devtoolset-3/root//usr/lib64/perl5/vendor_perl:/opt/rh/devtoolset-3/root/usr/lib/perl5:/opt/rh/devtoolset-3/root//usr/share/perl5/vendor_perl\",\n \"OLDPWD\": \"/home/nodeuser/project/node/src\",\n \"JAVACONFDIRS\": \"/opt/rh/devtoolset-3/root/etc/java:/etc/java\",\n \"SSH_TTY\": \"/dev/pts/0\",\n \"PCP_DIR\": \"/opt/rh/devtoolset-3/root\",\n \"GROUP\": \"normaluser\",\n \"USER\": \"nodeuser\",\n \"LD_LIBRARY_PATH\": \"/opt/rh/devtoolset-3/root/usr/lib64:/opt/rh/devtoolset-3/root/usr/lib\",\n \"HOSTTYPE\": \"x86_64-linux\",\n \"XDG_CONFIG_DIRS\": \"/opt/rh/devtoolset-3/root/etc/xdg:/etc/xdg\",\n \"MAIL\": \"/var/spool/mail/nodeuser\",\n \"PATH\": \"/home/nodeuser/project/node:/opt/rh/devtoolset-3/root/usr/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin\",\n \"PWD\": \"/home/nodeuser/project/node\",\n \"LANG\": \"en_US.UTF-8\",\n \"PS1\": \"\\\\u@\\\\h : \\\\[\\\\e[31m\\\\]\\\\w\\\\[\\\\e[m\\\\] > \",\n \"SHLVL\": \"2\",\n \"HOME\": \"/home/nodeuser\",\n \"OSTYPE\": \"linux\",\n \"VENDOR\": \"unknown\",\n \"PYTHONPATH\": \"/opt/rh/devtoolset-3/root/usr/lib64/python2.7/site-packages:/opt/rh/devtoolset-3/root/usr/lib/python2.7/site-packages\",\n \"MACHTYPE\": \"x86_64\",\n \"LOGNAME\": \"nodeuser\",\n \"XDG_DATA_DIRS\": \"/opt/rh/devtoolset-3/root/usr/share:/usr/local/share:/usr/share\",\n \"LESSOPEN\": \"||/usr/bin/lesspipe.sh %s\",\n \"INFOPATH\": \"/opt/rh/devtoolset-3/root/usr/share/info\",\n \"XDG_RUNTIME_DIR\": \"/run/user/50141\",\n \"_\": \"./node\"\n },\n \"userLimits\": {\n \"core_file_size_blocks\": {\n \"soft\": \"\",\n \"hard\": \"unlimited\"\n },\n \"data_seg_size_kbytes\": {\n \"soft\": \"unlimited\",\n \"hard\": \"unlimited\"\n },\n \"file_size_blocks\": {\n \"soft\": \"unlimited\",\n \"hard\": \"unlimited\"\n },\n \"max_locked_memory_bytes\": {\n \"soft\": \"unlimited\",\n \"hard\": 65536\n },\n \"max_memory_size_kbytes\": {\n \"soft\": \"unlimited\",\n \"hard\": \"unlimited\"\n },\n \"open_files\": {\n \"soft\": \"unlimited\",\n \"hard\": 4096\n },\n \"stack_size_bytes\": {\n \"soft\": \"unlimited\",\n \"hard\": \"unlimited\"\n },\n \"cpu_time_seconds\": {\n \"soft\": \"unlimited\",\n \"hard\": \"unlimited\"\n },\n \"max_user_processes\": {\n \"soft\": \"unlimited\",\n \"hard\": 4127290\n },\n \"virtual_memory_kbytes\": {\n \"soft\": \"unlimited\",\n \"hard\": \"unlimited\"\n }\n },\n \"sharedObjects\": [\n \"/lib64/libdl.so.2\",\n \"/lib64/librt.so.1\",\n \"/lib64/libstdc++.so.6\",\n \"/lib64/libm.so.6\",\n \"/lib64/libgcc_s.so.1\",\n \"/lib64/libpthread.so.0\",\n \"/lib64/libc.so.6\",\n \"/lib64/ld-linux-x86-64.so.2\"\n ]\n}\n
",
"miscs": [
{
"textRaw": "Usage",
"name": "usage",
"desc": "node --report-uncaught-exception --report-on-signal \\\n--report-on-fatalerror app.js\n
\n--report-uncaught-exception
Enables report to be generated on\nun-caught exceptions. Useful when inspecting JavaScript stack in conjunction\nwith native stack and other runtime environment data.
--report-on-signal
Enables report to be generated upon receiving\nthe specified (or predefined) signal to the running Node.js process. (See\nbelow on how to modify the signal that triggers the report.) Default signal is\nSIGUSR2
. Useful when a report needs to be triggered from another program.\nApplication monitors may leverage this feature to collect report at regular\nintervals and plot rich set of internal runtime data to their views.
Signal based report generation is not supported in Windows.
\nUnder normal circumstances, there is no need to modify the report triggering\nsignal. However, if SIGUSR2
is already used for other purposes, then this\nflag helps to change the signal for report generation and preserve the original\nmeaning of SIGUSR2
for the said purposes.
--report-on-fatalerror
Enables the report to be triggered on fatal errors\n(internal errors within the Node.js runtime, such as out of memory)\nthat leads to termination of the application. Useful to inspect various\ndiagnostic data elements such as heap, stack, event loop state, resource\nconsumption etc. to reason about the fatal error.
--report-compact
Write reports in a compact format, single-line JSON, more\neasily consumable by log processing systems than the default multi-line format\ndesigned for human consumption.
--report-directory
Location at which the report will be\ngenerated.
--report-filename
Name of the file to which the report will be\nwritten.
--report-signal
Sets or resets the signal for report generation\n(not supported on Windows). Default signal is SIGUSR2
.
A report can also be triggered via an API call from a JavaScript application:
\nprocess.report.writeReport();\n
\nThis function takes an optional additional argument filename
, which is\nthe name of a file into which the report is written.
process.report.writeReport('./foo.json');\n
\nThis function takes an optional additional argument err
which is an Error
\nobject that will be used as the context for the JavaScript stack printed in the\nreport. When using report to handle errors in a callback or an exception\nhandler, this allows the report to include the location of the original error as\nwell as where it was handled.
try {\n process.chdir('/non-existent-path');\n} catch (err) {\n process.report.writeReport(err);\n}\n// Any other code\n
\nIf both filename and error object are passed to writeReport()
the\nerror object must be the second parameter.
try {\n process.chdir('/non-existent-path');\n} catch (err) {\n process.report.writeReport(filename, err);\n}\n// Any other code\n
\nThe content of the diagnostic report can be returned as a JavaScript Object\nvia an API call from a JavaScript application:
\nconst report = process.report.getReport();\nconsole.log(typeof report === 'object'); // true\n\n// Similar to process.report.writeReport() output\nconsole.log(JSON.stringify(report, null, 2));\n
\nThis function takes an optional additional argument err
, which is an Error
\nobject that will be used as the context for the JavaScript stack printed in the\nreport.
const report = process.report.getReport(new Error('custom error'));\nconsole.log(typeof report === 'object'); // true\n
\nThe API versions are useful when inspecting the runtime state from within\nthe application, in expectation of self-adjusting the resource consumption,\nload balancing, monitoring etc.
\nThe content of the report consists of a header section containing the event\ntype, date, time, PID, and Node.js version, sections containing JavaScript and\nnative stack traces, a section containing V8 heap information, a section\ncontaining libuv
handle information, and an OS platform information section\nshowing CPU and memory usage and system limits. An example report can be\ntriggered using the Node.js REPL:
$ node\n> process.report.writeReport();\nWriting Node.js report to file: report.20181126.091102.8480.0.001.json\nNode.js report completed\n>\n
\nWhen a report is written, start and end messages are issued to stderr\nand the filename of the report is returned to the caller. The default filename\nincludes the date, time, PID, and a sequence number. The sequence number helps\nin associating the report dump with the runtime state if generated multiple\ntimes for the same Node.js process.
\nDiagnostic report has an associated single-digit version number (report.header.reportVersion
),\nuniquely representing the report format. The version number is bumped\nwhen new key is added or removed, or the data type of a value is changed.\nReport version definitions are consistent across LTS releases.
Additional runtime configuration of report generation is available via\nthe following properties of process.report
:
reportOnFatalError
triggers diagnostic reporting on fatal errors when true
.\nDefaults to false
.
reportOnSignal
triggers diagnostic reporting on signal when true
. This is\nnot supported on Windows. Defaults to false
.
reportOnUncaughtException
triggers diagnostic reporting on uncaught exception\nwhen true
. Defaults to false
.
signal
specifies the POSIX signal identifier that will be used\nto intercept external triggers for report generation. Defaults to\n'SIGUSR2'
.
filename
specifies the name of the output file in the file system.\nSpecial meaning is attached to stdout
and stderr
. Usage of these\nwill result in report being written to the associated standard streams.\nIn cases where standard streams are used, the value in directory
is ignored.\nURLs are not supported. Defaults to a composite filename that contains\ntimestamp, PID, and sequence number.
directory
specifies the file system directory where the report will be\nwritten. URLs are not supported. Defaults to the current working directory of\nthe Node.js process.
// Trigger report only on uncaught exceptions.\nprocess.report.reportOnFatalError = false;\nprocess.report.reportOnSignal = false;\nprocess.report.reportOnUncaughtException = true;\n\n// Trigger report for both internal errors as well as external signal.\nprocess.report.reportOnFatalError = true;\nprocess.report.reportOnSignal = true;\nprocess.report.reportOnUncaughtException = false;\n\n// Change the default signal to 'SIGQUIT' and enable it.\nprocess.report.reportOnFatalError = false;\nprocess.report.reportOnUncaughtException = false;\nprocess.report.reportOnSignal = true;\nprocess.report.signal = 'SIGQUIT';\n
\nConfiguration on module initialization is also available via\nenvironment variables:
\nNODE_OPTIONS=\"--report-uncaught-exception \\\n --report-on-fatalerror --report-on-signal \\\n --report-signal=SIGUSR2 --report-filename=./report.json \\\n --report-directory=/home/nodeuser\"\n
\nSpecific API documentation can be found under\nprocess API documentation
section.
Worker
threads can create reports in the same way that the main thread\ndoes.
Reports will include information on any Workers that are children of the current\nthread as part of the workers
section, with each Worker generating a report\nin the standard report format.
The thread which is generating the report will wait for the reports from Worker\nthreads to finish. However, the latency for this will usually be low, as both\nrunning JavaScript and the event loop are interrupted to generate the report.
", "type": "misc", "displayName": "Interaction with workers" } ], "source": "doc/api/report.md" } ], "modules": [ { "textRaw": "Usage and example", "name": "usage_and_example", "introduced_in": "v0.10.0", "miscs": [ { "textRaw": "Usage", "name": "Usage", "introduced_in": "v0.10.0", "type": "misc", "desc": "node [options] [V8 options] [script.js | -e \"script\" | - ] [arguments]
Please see the Command-line options document for more information.
\nAn example of a web server written with Node.js which responds with\n'Hello, World!'
:
Commands in this document start with $
or >
to replicate how they would\nappear in a user's terminal. Do not include the $
and >
characters. They are\nthere to show the start of each command.
Lines that don't start with $
or >
character show the output of the previous\ncommand.
First, make sure to have downloaded and installed Node.js. See\nInstalling Node.js via package manager for further install information.
\nNow, create an empty project folder called projects
, then navigate into it.
Linux and Mac:
\nmkdir ~/projects\ncd ~/projects\n
\nWindows CMD:
\nmkdir %USERPROFILE%\\projects\ncd %USERPROFILE%\\projects\n
\nWindows PowerShell:
\nmkdir $env:USERPROFILE\\projects\ncd $env:USERPROFILE\\projects\n
\nNext, create a new source file in the projects
\nfolder and call it hello-world.js
.
Open hello-world.js
in any preferred text editor and\npaste in the following content:
const http = require('node:http');\n\nconst hostname = '127.0.0.1';\nconst port = 3000;\n\nconst server = http.createServer((req, res) => {\n res.statusCode = 200;\n res.setHeader('Content-Type', 'text/plain');\n res.end('Hello, World!\\n');\n});\n\nserver.listen(port, hostname, () => {\n console.log(`Server running at http://${hostname}:${port}/`);\n});\n
\nSave the file. Then, in the terminal window, to run the hello-world.js
file,\nenter:
node hello-world.js\n
\nOutput like this should appear in the terminal:
\nServer running at http://127.0.0.1:3000/\n
\nNow, open any preferred web browser and visit http://127.0.0.1:3000
.
If the browser displays the string Hello, World!
, that indicates\nthe server is working.
Source Code: lib/assert.js
\nThe node:assert
module provides a set of assertion functions for verifying\ninvariants.
In strict assertion mode, non-strict methods behave like their corresponding\nstrict methods. For example, assert.deepEqual()
will behave like\nassert.deepStrictEqual()
.
In strict assertion mode, error messages for objects display a diff. In legacy\nassertion mode, error messages for objects display the objects, often truncated.
\nTo use strict assertion mode:
\nimport { strict as assert } from 'node:assert';\n
\nconst assert = require('node:assert').strict;\n
\nimport assert from 'node:assert/strict';\n
\nconst assert = require('node:assert/strict');\n
\nExample error diff:
\nimport { strict as assert } from 'node:assert';\n\nassert.deepEqual([[[1, 2, 3]], 4, 5], [[[1, 2, '3']], 4, 5]);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected ... Lines skipped\n//\n// [\n// [\n// ...\n// 2,\n// + 3\n// - '3'\n// ],\n// ...\n// 5\n// ]\n
\nconst assert = require('node:assert/strict');\n\nassert.deepEqual([[[1, 2, 3]], 4, 5], [[[1, 2, '3']], 4, 5]);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected ... Lines skipped\n//\n// [\n// [\n// ...\n// 2,\n// + 3\n// - '3'\n// ],\n// ...\n// 5\n// ]\n
\nTo deactivate the colors, use the NO_COLOR
or NODE_DISABLE_COLORS
\nenvironment variables. This will also deactivate the colors in the REPL. For\nmore on color support in terminal environments, read the tty\ngetColorDepth()
documentation.
Legacy assertion mode uses the ==
operator in:
To use legacy assertion mode:
\nimport assert from 'node:assert';\n
\nconst assert = require('node:assert');\n
\nLegacy assertion mode may have surprising results, especially when using\nassert.deepEqual()
:
// WARNING: This does not throw an AssertionError in legacy assertion mode!\nassert.deepEqual(/a/gi, new Date());\n
",
"type": "module",
"displayName": "Legacy assertion mode"
}
],
"classes": [
{
"textRaw": "Class: assert.AssertionError",
"type": "class",
"name": "assert.AssertionError",
"desc": "Indicates the failure of an assertion. All errors thrown by the node:assert
\nmodule will be instances of the AssertionError
class.
A subclass of Error
that indicates the failure of an assertion.
All instances contain the built-in Error
properties (message
and name
)\nand:
actual
<any> Set to the actual
argument for methods such as\nassert.strictEqual()
.expected
<any> Set to the expected
value for methods such as\nassert.strictEqual()
.generatedMessage
<boolean> Indicates if the message was auto-generated\n(true
) or not.code
<string> Value is always ERR_ASSERTION
to show that the error is an\nassertion error.operator
<string> Set to the passed in operator value.import assert from 'node:assert';\n\n// Generate an AssertionError to compare the error message later:\nconst { message } = new assert.AssertionError({\n actual: 1,\n expected: 2,\n operator: 'strictEqual',\n});\n\n// Verify error output:\ntry {\n assert.strictEqual(1, 2);\n} catch (err) {\n assert(err instanceof assert.AssertionError);\n assert.strictEqual(err.message, message);\n assert.strictEqual(err.name, 'AssertionError');\n assert.strictEqual(err.actual, 1);\n assert.strictEqual(err.expected, 2);\n assert.strictEqual(err.code, 'ERR_ASSERTION');\n assert.strictEqual(err.operator, 'strictEqual');\n assert.strictEqual(err.generatedMessage, true);\n}\n
\nconst assert = require('node:assert');\n\n// Generate an AssertionError to compare the error message later:\nconst { message } = new assert.AssertionError({\n actual: 1,\n expected: 2,\n operator: 'strictEqual',\n});\n\n// Verify error output:\ntry {\n assert.strictEqual(1, 2);\n} catch (err) {\n assert(err instanceof assert.AssertionError);\n assert.strictEqual(err.message, message);\n assert.strictEqual(err.name, 'AssertionError');\n assert.strictEqual(err.actual, 1);\n assert.strictEqual(err.expected, 2);\n assert.strictEqual(err.code, 'ERR_ASSERTION');\n assert.strictEqual(err.operator, 'strictEqual');\n assert.strictEqual(err.generatedMessage, true);\n}\n
"
}
]
},
{
"textRaw": "Class: `assert.CallTracker`",
"type": "class",
"name": "assert.CallTracker",
"meta": {
"added": [
"v14.2.0",
"v12.19.0"
],
"changes": [
{
"version": "v20.1.0",
"pr-url": "https://github.com/nodejs/node/pull/47740",
"description": "the `assert.CallTracker` class has been deprecated and will be removed in a future version."
}
]
},
"stability": 0,
"stabilityText": "Deprecated",
"desc": "This feature is deprecated and will be removed in a future version.\nPlease consider using alternatives such as the\nmock
helper function.
The wrapper function is expected to be called exactly exact
times. If the\nfunction has not been called exactly exact
times when\ntracker.verify()
is called, then tracker.verify()
will throw an\nerror.
import assert from 'node:assert';\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// Returns a function that wraps func() that must be called exact times\n// before tracker.verify().\nconst callsfunc = tracker.calls(func);\n
\nconst assert = require('node:assert');\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// Returns a function that wraps func() that must be called exact times\n// before tracker.verify().\nconst callsfunc = tracker.calls(func);\n
"
},
{
"textRaw": "`tracker.getCalls(fn)`",
"type": "method",
"name": "getCalls",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Array} An array with all the calls to a tracked function.",
"name": "return",
"type": "Array",
"desc": "An array with all the calls to a tracked function."
},
"params": [
{
"textRaw": "`fn` {Function}",
"name": "fn",
"type": "Function"
},
{
"textRaw": "Object {Object}",
"name": "Object",
"type": "Object",
"options": [
{
"textRaw": "`thisArg` {Object}",
"name": "thisArg",
"type": "Object"
},
{
"textRaw": "`arguments` {Array} the arguments passed to the tracked function",
"name": "arguments",
"type": "Array",
"desc": "the arguments passed to the tracked function"
}
]
}
]
}
],
"desc": "import assert from 'node:assert';\n\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\nconst callsfunc = tracker.calls(func);\ncallsfunc(1, 2, 3);\n\nassert.deepStrictEqual(tracker.getCalls(callsfunc),\n [{ thisArg: undefined, arguments: [1, 2, 3] }]);\n
\nconst assert = require('node:assert');\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\nconst callsfunc = tracker.calls(func);\ncallsfunc(1, 2, 3);\n\nassert.deepStrictEqual(tracker.getCalls(callsfunc),\n [{ thisArg: undefined, arguments: [1, 2, 3] }]);\n
"
},
{
"textRaw": "`tracker.report()`",
"type": "method",
"name": "report",
"meta": {
"added": [
"v14.2.0",
"v12.19.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Array} An array of objects containing information about the wrapper functions returned by [`tracker.calls()`][].",
"name": "return",
"type": "Array",
"desc": "An array of objects containing information about the wrapper functions returned by [`tracker.calls()`][]."
},
"params": [
{
"textRaw": "Object {Object}",
"name": "Object",
"type": "Object",
"options": [
{
"textRaw": "`message` {string}",
"name": "message",
"type": "string"
},
{
"textRaw": "`actual` {number} The actual number of times the function was called.",
"name": "actual",
"type": "number",
"desc": "The actual number of times the function was called."
},
{
"textRaw": "`expected` {number} The number of times the function was expected to be called.",
"name": "expected",
"type": "number",
"desc": "The number of times the function was expected to be called."
},
{
"textRaw": "`operator` {string} The name of the function that is wrapped.",
"name": "operator",
"type": "string",
"desc": "The name of the function that is wrapped."
},
{
"textRaw": "`stack` {Object} A stack trace of the function.",
"name": "stack",
"type": "Object",
"desc": "A stack trace of the function."
}
]
}
]
}
],
"desc": "The arrays contains information about the expected and actual number of calls of\nthe functions that have not been called the expected number of times.
\nimport assert from 'node:assert';\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// Returns a function that wraps func() that must be called exact times\n// before tracker.verify().\nconst callsfunc = tracker.calls(func, 2);\n\n// Returns an array containing information on callsfunc()\nconsole.log(tracker.report());\n// [\n// {\n// message: 'Expected the func function to be executed 2 time(s) but was\n// executed 0 time(s).',\n// actual: 0,\n// expected: 2,\n// operator: 'func',\n// stack: stack trace\n// }\n// ]\n
\nconst assert = require('node:assert');\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// Returns a function that wraps func() that must be called exact times\n// before tracker.verify().\nconst callsfunc = tracker.calls(func, 2);\n\n// Returns an array containing information on callsfunc()\nconsole.log(tracker.report());\n// [\n// {\n// message: 'Expected the func function to be executed 2 time(s) but was\n// executed 0 time(s).',\n// actual: 0,\n// expected: 2,\n// operator: 'func',\n// stack: stack trace\n// }\n// ]\n
"
},
{
"textRaw": "`tracker.reset([fn])`",
"type": "method",
"name": "reset",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function} a tracked function to reset.",
"name": "fn",
"type": "Function",
"desc": "a tracked function to reset."
}
]
}
],
"desc": "Reset calls of the call tracker.\nIf a tracked function is passed as an argument, the calls will be reset for it.\nIf no arguments are passed, all tracked functions will be reset.
\nimport assert from 'node:assert';\n\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\nconst callsfunc = tracker.calls(func);\n\ncallsfunc();\n// Tracker was called once\nassert.strictEqual(tracker.getCalls(callsfunc).length, 1);\n\ntracker.reset(callsfunc);\nassert.strictEqual(tracker.getCalls(callsfunc).length, 0);\n
\nconst assert = require('node:assert');\n\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\nconst callsfunc = tracker.calls(func);\n\ncallsfunc();\n// Tracker was called once\nassert.strictEqual(tracker.getCalls(callsfunc).length, 1);\n\ntracker.reset(callsfunc);\nassert.strictEqual(tracker.getCalls(callsfunc).length, 0);\n
"
},
{
"textRaw": "`tracker.verify()`",
"type": "method",
"name": "verify",
"meta": {
"added": [
"v14.2.0",
"v12.19.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Iterates through the list of functions passed to\ntracker.calls()
and will throw an error for functions that\nhave not been called the expected number of times.
import assert from 'node:assert';\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// Returns a function that wraps func() that must be called exact times\n// before tracker.verify().\nconst callsfunc = tracker.calls(func, 2);\n\ncallsfunc();\n\n// Will throw an error since callsfunc() was only called once.\ntracker.verify();\n
\nconst assert = require('node:assert');\n\n// Creates call tracker.\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// Returns a function that wraps func() that must be called exact times\n// before tracker.verify().\nconst callsfunc = tracker.calls(func, 2);\n\ncallsfunc();\n\n// Will throw an error since callsfunc() was only called once.\ntracker.verify();\n
"
}
],
"signatures": [
{
"params": [],
"desc": "Creates a new CallTracker
object which can be used to track if functions\nwere called a specific number of times. The tracker.verify()
must be called\nfor the verification to take place. The usual pattern would be to call it in a\nprocess.on('exit')
handler.
import assert from 'node:assert';\nimport process from 'node:process';\n\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// callsfunc() must be called exactly 1 time before tracker.verify().\nconst callsfunc = tracker.calls(func, 1);\n\ncallsfunc();\n\n// Calls tracker.verify() and verifies if all tracker.calls() functions have\n// been called exact times.\nprocess.on('exit', () => {\n tracker.verify();\n});\n
\nconst assert = require('node:assert');\n\nconst tracker = new assert.CallTracker();\n\nfunction func() {}\n\n// callsfunc() must be called exactly 1 time before tracker.verify().\nconst callsfunc = tracker.calls(func, 1);\n\ncallsfunc();\n\n// Calls tracker.verify() and verifies if all tracker.calls() functions have\n// been called exact times.\nprocess.on('exit', () => {\n tracker.verify();\n});\n
"
}
]
}
],
"methods": [
{
"textRaw": "`assert(value[, message])`",
"type": "method",
"name": "assert",
"meta": {
"added": [
"v0.5.9"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`value` {any} The input that is checked for being truthy.",
"name": "value",
"type": "any",
"desc": "The input that is checked for being truthy."
},
{
"textRaw": "`message` {string|Error}",
"name": "message",
"type": "string|Error"
}
]
}
],
"desc": "An alias of assert.ok()
.
Strict assertion mode
\nAn alias of assert.deepStrictEqual()
.
Legacy assertion mode
\n\n\nStability: 3 - Legacy: Use
\nassert.deepStrictEqual()
instead.
Tests for deep equality between the actual
and expected
parameters. Consider\nusing assert.deepStrictEqual()
instead. assert.deepEqual()
can have\nsurprising results.
Deep equality means that the enumerable \"own\" properties of child objects\nare also recursively evaluated by the following rules.
", "modules": [ { "textRaw": "Comparison details", "name": "comparison_details", "desc": "==
operator,\nwith the exception of NaN
. It is treated as being identical in case\nboth sides are NaN
.Error
names and messages are always compared, even if these are not\nenumerable properties.Object
properties are compared unordered.Map
keys and Set
items are compared unordered.[[Prototype]]
of\nobjects.Symbol
properties are not compared.WeakMap
and WeakSet
comparison does not rely on their values.RegExp
lastIndex, flags, and source are always compared, even if these\nare not enumerable properties.The following example does not throw an AssertionError
because the\nprimitives are compared using the ==
operator.
import assert from 'node:assert';\n// WARNING: This does not throw an AssertionError!\n\nassert.deepEqual('+00000000', false);\n
\nconst assert = require('node:assert');\n// WARNING: This does not throw an AssertionError!\n\nassert.deepEqual('+00000000', false);\n
\n\"Deep\" equality means that the enumerable \"own\" properties of child objects\nare evaluated also:
\nimport assert from 'node:assert';\n\nconst obj1 = {\n a: {\n b: 1,\n },\n};\nconst obj2 = {\n a: {\n b: 2,\n },\n};\nconst obj3 = {\n a: {\n b: 1,\n },\n};\nconst obj4 = { __proto__: obj1 };\n\nassert.deepEqual(obj1, obj1);\n// OK\n\n// Values of b are different:\nassert.deepEqual(obj1, obj2);\n// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }\n\nassert.deepEqual(obj1, obj3);\n// OK\n\n// Prototypes are ignored:\nassert.deepEqual(obj1, obj4);\n// AssertionError: { a: { b: 1 } } deepEqual {}\n
\nconst assert = require('node:assert');\n\nconst obj1 = {\n a: {\n b: 1,\n },\n};\nconst obj2 = {\n a: {\n b: 2,\n },\n};\nconst obj3 = {\n a: {\n b: 1,\n },\n};\nconst obj4 = { __proto__: obj1 };\n\nassert.deepEqual(obj1, obj1);\n// OK\n\n// Values of b are different:\nassert.deepEqual(obj1, obj2);\n// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }\n\nassert.deepEqual(obj1, obj3);\n// OK\n\n// Prototypes are ignored:\nassert.deepEqual(obj1, obj4);\n// AssertionError: { a: { b: 1 } } deepEqual {}\n
\nIf the values are not equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned. If the message
\nparameter is an instance of an Error
then it will be thrown instead of the\nAssertionError
.
Tests for deep equality between the actual
and expected
parameters.\n\"Deep\" equality means that the enumerable \"own\" properties of child objects\nare recursively evaluated also by the following rules.
Object.is()
.[[Prototype]]
of objects are compared using\nthe ===
operator.Error
names and messages are always compared, even if these are not\nenumerable properties.Symbol
properties are compared as well.Object
properties are compared unordered.Map
keys and Set
items are compared unordered.WeakMap
and WeakSet
comparison does not rely on their values. See\nbelow for further details.RegExp
lastIndex, flags, and source are always compared, even if these\nare not enumerable properties.import assert from 'node:assert/strict';\n\n// This fails because 1 !== '1'.\nassert.deepStrictEqual({ a: 1 }, { a: '1' });\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// {\n// + a: 1\n// - a: '1'\n// }\n\n// The following objects don't have own properties\nconst date = new Date();\nconst object = {};\nconst fakeDate = {};\nObject.setPrototypeOf(fakeDate, Date.prototype);\n\n// Different [[Prototype]]:\nassert.deepStrictEqual(object, fakeDate);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + {}\n// - Date {}\n\n// Different type tags:\nassert.deepStrictEqual(date, fakeDate);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + 2018-04-26T00:49:08.604Z\n// - Date {}\n\nassert.deepStrictEqual(NaN, NaN);\n// OK because Object.is(NaN, NaN) is true.\n\n// Different unwrapped numbers:\nassert.deepStrictEqual(new Number(1), new Number(2));\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + [Number: 1]\n// - [Number: 2]\n\nassert.deepStrictEqual(new String('foo'), Object('foo'));\n// OK because the object and the string are identical when unwrapped.\n\nassert.deepStrictEqual(-0, -0);\n// OK\n\n// Different zeros:\nassert.deepStrictEqual(0, -0);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + 0\n// - -0\n\nconst symbol1 = Symbol();\nconst symbol2 = Symbol();\nassert.deepStrictEqual({ [symbol1]: 1 }, { [symbol1]: 1 });\n// OK, because it is the same symbol on both objects.\n\nassert.deepStrictEqual({ [symbol1]: 1 }, { [symbol2]: 1 });\n// AssertionError [ERR_ASSERTION]: Inputs identical but not reference equal:\n//\n// {\n// [Symbol()]: 1\n// }\n\nconst weakMap1 = new WeakMap();\nconst weakMap2 = new WeakMap([[{}, {}]]);\nconst weakMap3 = new WeakMap();\nweakMap3.unequal = true;\n\nassert.deepStrictEqual(weakMap1, weakMap2);\n// OK, because it is impossible to compare the entries\n\n// Fails because weakMap3 has a property that weakMap1 does not contain:\nassert.deepStrictEqual(weakMap1, weakMap3);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// WeakMap {\n// + [items unknown]\n// - [items unknown],\n// - unequal: true\n// }\n
\nconst assert = require('node:assert/strict');\n\n// This fails because 1 !== '1'.\nassert.deepStrictEqual({ a: 1 }, { a: '1' });\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// {\n// + a: 1\n// - a: '1'\n// }\n\n// The following objects don't have own properties\nconst date = new Date();\nconst object = {};\nconst fakeDate = {};\nObject.setPrototypeOf(fakeDate, Date.prototype);\n\n// Different [[Prototype]]:\nassert.deepStrictEqual(object, fakeDate);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + {}\n// - Date {}\n\n// Different type tags:\nassert.deepStrictEqual(date, fakeDate);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + 2018-04-26T00:49:08.604Z\n// - Date {}\n\nassert.deepStrictEqual(NaN, NaN);\n// OK because Object.is(NaN, NaN) is true.\n\n// Different unwrapped numbers:\nassert.deepStrictEqual(new Number(1), new Number(2));\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + [Number: 1]\n// - [Number: 2]\n\nassert.deepStrictEqual(new String('foo'), Object('foo'));\n// OK because the object and the string are identical when unwrapped.\n\nassert.deepStrictEqual(-0, -0);\n// OK\n\n// Different zeros:\nassert.deepStrictEqual(0, -0);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// + 0\n// - -0\n\nconst symbol1 = Symbol();\nconst symbol2 = Symbol();\nassert.deepStrictEqual({ [symbol1]: 1 }, { [symbol1]: 1 });\n// OK, because it is the same symbol on both objects.\n\nassert.deepStrictEqual({ [symbol1]: 1 }, { [symbol2]: 1 });\n// AssertionError [ERR_ASSERTION]: Inputs identical but not reference equal:\n//\n// {\n// [Symbol()]: 1\n// }\n\nconst weakMap1 = new WeakMap();\nconst weakMap2 = new WeakMap([[{}, {}]]);\nconst weakMap3 = new WeakMap();\nweakMap3.unequal = true;\n\nassert.deepStrictEqual(weakMap1, weakMap2);\n// OK, because it is impossible to compare the entries\n\n// Fails because weakMap3 has a property that weakMap1 does not contain:\nassert.deepStrictEqual(weakMap1, weakMap3);\n// AssertionError: Expected inputs to be strictly deep-equal:\n// + actual - expected\n//\n// WeakMap {\n// + [items unknown]\n// - [items unknown],\n// - unequal: true\n// }\n
\nIf the values are not equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned. If the message
\nparameter is an instance of an Error
then it will be thrown instead of the\nAssertionError
.
Expects the string
input not to match the regular expression.
import assert from 'node:assert/strict';\n\nassert.doesNotMatch('I will fail', /fail/);\n// AssertionError [ERR_ASSERTION]: The input was expected to not match the ...\n\nassert.doesNotMatch(123, /pass/);\n// AssertionError [ERR_ASSERTION]: The \"string\" argument must be of type string.\n\nassert.doesNotMatch('I will pass', /different/);\n// OK\n
\nconst assert = require('node:assert/strict');\n\nassert.doesNotMatch('I will fail', /fail/);\n// AssertionError [ERR_ASSERTION]: The input was expected to not match the ...\n\nassert.doesNotMatch(123, /pass/);\n// AssertionError [ERR_ASSERTION]: The \"string\" argument must be of type string.\n\nassert.doesNotMatch('I will pass', /different/);\n// OK\n
\nIf the values do match, or if the string
argument is of another type than\nstring
, an AssertionError
is thrown with a message
property set equal\nto the value of the message
parameter. If the message
parameter is\nundefined, a default error message is assigned. If the message
parameter is an\ninstance of an Error
then it will be thrown instead of the\nAssertionError
.
Awaits the asyncFn
promise or, if asyncFn
is a function, immediately\ncalls the function and awaits the returned promise to complete. It will then\ncheck that the promise is not rejected.
If asyncFn
is a function and it throws an error synchronously,\nassert.doesNotReject()
will return a rejected Promise
with that error. If\nthe function does not return a promise, assert.doesNotReject()
will return a\nrejected Promise
with an ERR_INVALID_RETURN_VALUE
error. In both cases\nthe error handler is skipped.
Using assert.doesNotReject()
is actually not useful because there is little\nbenefit in catching a rejection and then rejecting it again. Instead, consider\nadding a comment next to the specific code path that should not reject and keep\nerror messages as expressive as possible.
If specified, error
can be a Class
, RegExp
, or a validation\nfunction. See assert.throws()
for more details.
Besides the async nature to await the completion behaves identically to\nassert.doesNotThrow()
.
import assert from 'node:assert/strict';\n\nawait assert.doesNotReject(\n async () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError,\n);\n
\nconst assert = require('node:assert/strict');\n\n(async () => {\n await assert.doesNotReject(\n async () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError,\n );\n})();\n
\nimport assert from 'node:assert/strict';\n\nassert.doesNotReject(Promise.reject(new TypeError('Wrong value')))\n .then(() => {\n // ...\n });\n
\nconst assert = require('node:assert/strict');\n\nassert.doesNotReject(Promise.reject(new TypeError('Wrong value')))\n .then(() => {\n // ...\n });\n
"
},
{
"textRaw": "`assert.doesNotThrow(fn[, error][, message])`",
"type": "method",
"name": "doesNotThrow",
"meta": {
"added": [
"v0.1.21"
],
"changes": [
{
"version": [
"v5.11.0",
"v4.4.5"
],
"pr-url": "https://github.com/nodejs/node/pull/2407",
"description": "The `message` parameter is respected now."
},
{
"version": "v4.2.0",
"pr-url": "https://github.com/nodejs/node/pull/3276",
"description": "The `error` parameter can now be an arrow function."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function}",
"name": "fn",
"type": "Function"
},
{
"textRaw": "`error` {RegExp|Function}",
"name": "error",
"type": "RegExp|Function"
},
{
"textRaw": "`message` {string}",
"name": "message",
"type": "string"
}
]
}
],
"desc": "Asserts that the function fn
does not throw an error.
Using assert.doesNotThrow()
is actually not useful because there\nis no benefit in catching an error and then rethrowing it. Instead, consider\nadding a comment next to the specific code path that should not throw and keep\nerror messages as expressive as possible.
When assert.doesNotThrow()
is called, it will immediately call the fn
\nfunction.
If an error is thrown and it is the same type as that specified by the error
\nparameter, then an AssertionError
is thrown. If the error is of a\ndifferent type, or if the error
parameter is undefined, the error is\npropagated back to the caller.
If specified, error
can be a Class
, RegExp
, or a validation\nfunction. See assert.throws()
for more details.
The following, for instance, will throw the TypeError
because there is no\nmatching error type in the assertion:
import assert from 'node:assert/strict';\n\nassert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError,\n);\n
\nconst assert = require('node:assert/strict');\n\nassert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError,\n);\n
\nHowever, the following will result in an AssertionError
with the message\n'Got unwanted exception...':
import assert from 'node:assert/strict';\n\nassert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n TypeError,\n);\n
\nconst assert = require('node:assert/strict');\n\nassert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n TypeError,\n);\n
\nIf an AssertionError
is thrown and a value is provided for the message
\nparameter, the value of message
will be appended to the AssertionError
\nmessage:
import assert from 'node:assert/strict';\n\nassert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n /Wrong value/,\n 'Whoops',\n);\n// Throws: AssertionError: Got unwanted exception: Whoops\n
\nconst assert = require('node:assert/strict');\n\nassert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n /Wrong value/,\n 'Whoops',\n);\n// Throws: AssertionError: Got unwanted exception: Whoops\n
"
},
{
"textRaw": "`assert.equal(actual, expected[, message])`",
"type": "method",
"name": "equal",
"meta": {
"added": [
"v0.1.21"
],
"changes": [
{
"version": [
"v16.0.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/38113",
"description": "In Legacy assertion mode, changed status from Deprecated to Legacy."
},
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/30766",
"description": "NaN is now treated as being identical if both sides are NaN."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`actual` {any}",
"name": "actual",
"type": "any"
},
{
"textRaw": "`expected` {any}",
"name": "expected",
"type": "any"
},
{
"textRaw": "`message` {string|Error}",
"name": "message",
"type": "string|Error"
}
]
}
],
"desc": "Strict assertion mode
\nAn alias of assert.strictEqual()
.
Legacy assertion mode
\n\n\nStability: 3 - Legacy: Use
\nassert.strictEqual()
instead.
Tests shallow, coercive equality between the actual
and expected
parameters\nusing the ==
operator. NaN
is specially handled\nand treated as being identical if both sides are NaN
.
import assert from 'node:assert';\n\nassert.equal(1, 1);\n// OK, 1 == 1\nassert.equal(1, '1');\n// OK, 1 == '1'\nassert.equal(NaN, NaN);\n// OK\n\nassert.equal(1, 2);\n// AssertionError: 1 == 2\nassert.equal({ a: { b: 1 } }, { a: { b: 1 } });\n// AssertionError: { a: { b: 1 } } == { a: { b: 1 } }\n
\nconst assert = require('node:assert');\n\nassert.equal(1, 1);\n// OK, 1 == 1\nassert.equal(1, '1');\n// OK, 1 == '1'\nassert.equal(NaN, NaN);\n// OK\n\nassert.equal(1, 2);\n// AssertionError: 1 == 2\nassert.equal({ a: { b: 1 } }, { a: { b: 1 } });\n// AssertionError: { a: { b: 1 } } == { a: { b: 1 } }\n
\nIf the values are not equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned. If the message
\nparameter is an instance of an Error
then it will be thrown instead of the\nAssertionError
.
Throws an AssertionError
with the provided error message or a default\nerror message. If the message
parameter is an instance of an Error
then\nit will be thrown instead of the AssertionError
.
import assert from 'node:assert/strict';\n\nassert.fail();\n// AssertionError [ERR_ASSERTION]: Failed\n\nassert.fail('boom');\n// AssertionError [ERR_ASSERTION]: boom\n\nassert.fail(new TypeError('need array'));\n// TypeError: need array\n
\nconst assert = require('node:assert/strict');\n\nassert.fail();\n// AssertionError [ERR_ASSERTION]: Failed\n\nassert.fail('boom');\n// AssertionError [ERR_ASSERTION]: boom\n\nassert.fail(new TypeError('need array'));\n// TypeError: need array\n
\nUsing assert.fail()
with more than two arguments is possible but deprecated.\nSee below for further details.
If message
is falsy, the error message is set as the values of actual
and\nexpected
separated by the provided operator
. If just the two actual
and\nexpected
arguments are provided, operator
will default to '!='
. If\nmessage
is provided as third argument it will be used as the error message and\nthe other arguments will be stored as properties on the thrown object. If\nstackStartFn
is provided, all stack frames above that function will be\nremoved from stacktrace (see Error.captureStackTrace
). If no arguments are\ngiven, the default message Failed
will be used.
import assert from 'node:assert/strict';\n\nassert.fail('a', 'b');\n// AssertionError [ERR_ASSERTION]: 'a' != 'b'\n\nassert.fail(1, 2, undefined, '>');\n// AssertionError [ERR_ASSERTION]: 1 > 2\n\nassert.fail(1, 2, 'fail');\n// AssertionError [ERR_ASSERTION]: fail\n\nassert.fail(1, 2, 'whoops', '>');\n// AssertionError [ERR_ASSERTION]: whoops\n\nassert.fail(1, 2, new TypeError('need array'));\n// TypeError: need array\n
\nconst assert = require('node:assert/strict');\n\nassert.fail('a', 'b');\n// AssertionError [ERR_ASSERTION]: 'a' != 'b'\n\nassert.fail(1, 2, undefined, '>');\n// AssertionError [ERR_ASSERTION]: 1 > 2\n\nassert.fail(1, 2, 'fail');\n// AssertionError [ERR_ASSERTION]: fail\n\nassert.fail(1, 2, 'whoops', '>');\n// AssertionError [ERR_ASSERTION]: whoops\n\nassert.fail(1, 2, new TypeError('need array'));\n// TypeError: need array\n
\nIn the last three cases actual
, expected
, and operator
have no\ninfluence on the error message.
Example use of stackStartFn
for truncating the exception's stacktrace:
import assert from 'node:assert/strict';\n\nfunction suppressFrame() {\n assert.fail('a', 'b', undefined, '!==', suppressFrame);\n}\nsuppressFrame();\n// AssertionError [ERR_ASSERTION]: 'a' !== 'b'\n// at repl:1:1\n// at ContextifyScript.Script.runInThisContext (vm.js:44:33)\n// ...\n
\nconst assert = require('node:assert/strict');\n\nfunction suppressFrame() {\n assert.fail('a', 'b', undefined, '!==', suppressFrame);\n}\nsuppressFrame();\n// AssertionError [ERR_ASSERTION]: 'a' !== 'b'\n// at repl:1:1\n// at ContextifyScript.Script.runInThisContext (vm.js:44:33)\n// ...\n
"
},
{
"textRaw": "`assert.ifError(value)`",
"type": "method",
"name": "ifError",
"meta": {
"added": [
"v0.1.97"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18247",
"description": "Instead of throwing the original error it is now wrapped into an [`AssertionError`][] that contains the full stack trace."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18247",
"description": "Value may now only be `undefined` or `null`. Before all falsy values were handled the same as `null` and did not throw."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Throws value
if value
is not undefined
or null
. This is useful when\ntesting the error
argument in callbacks. The stack trace contains all frames\nfrom the error passed to ifError()
including the potential new frames for\nifError()
itself.
import assert from 'node:assert/strict';\n\nassert.ifError(null);\n// OK\nassert.ifError(0);\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0\nassert.ifError('error');\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'\nassert.ifError(new Error());\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Error\n\n// Create some random error frames.\nlet err;\n(function errorFrame() {\n err = new Error('test error');\n})();\n\n(function ifErrorFrame() {\n assert.ifError(err);\n})();\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: test error\n// at ifErrorFrame\n// at errorFrame\n
\nconst assert = require('node:assert/strict');\n\nassert.ifError(null);\n// OK\nassert.ifError(0);\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0\nassert.ifError('error');\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'\nassert.ifError(new Error());\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Error\n\n// Create some random error frames.\nlet err;\n(function errorFrame() {\n err = new Error('test error');\n})();\n\n(function ifErrorFrame() {\n assert.ifError(err);\n})();\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: test error\n// at ifErrorFrame\n// at errorFrame\n
"
},
{
"textRaw": "`assert.match(string, regexp[, message])`",
"type": "method",
"name": "match",
"meta": {
"added": [
"v13.6.0",
"v12.16.0"
],
"changes": [
{
"version": "v16.0.0",
"pr-url": "https://github.com/nodejs/node/pull/38111",
"description": "This API is no longer experimental."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`string` {string}",
"name": "string",
"type": "string"
},
{
"textRaw": "`regexp` {RegExp}",
"name": "regexp",
"type": "RegExp"
},
{
"textRaw": "`message` {string|Error}",
"name": "message",
"type": "string|Error"
}
]
}
],
"desc": "Expects the string
input to match the regular expression.
import assert from 'node:assert/strict';\n\nassert.match('I will fail', /pass/);\n// AssertionError [ERR_ASSERTION]: The input did not match the regular ...\n\nassert.match(123, /pass/);\n// AssertionError [ERR_ASSERTION]: The \"string\" argument must be of type string.\n\nassert.match('I will pass', /pass/);\n// OK\n
\nconst assert = require('node:assert/strict');\n\nassert.match('I will fail', /pass/);\n// AssertionError [ERR_ASSERTION]: The input did not match the regular ...\n\nassert.match(123, /pass/);\n// AssertionError [ERR_ASSERTION]: The \"string\" argument must be of type string.\n\nassert.match('I will pass', /pass/);\n// OK\n
\nIf the values do not match, or if the string
argument is of another type than\nstring
, an AssertionError
is thrown with a message
property set equal\nto the value of the message
parameter. If the message
parameter is\nundefined, a default error message is assigned. If the message
parameter is an\ninstance of an Error
then it will be thrown instead of the\nAssertionError
.
Strict assertion mode
\nAn alias of assert.notDeepStrictEqual()
.
Legacy assertion mode
\n\n\nStability: 3 - Legacy: Use
\nassert.notDeepStrictEqual()
instead.
Tests for any deep inequality. Opposite of assert.deepEqual()
.
import assert from 'node:assert';\n\nconst obj1 = {\n a: {\n b: 1,\n },\n};\nconst obj2 = {\n a: {\n b: 2,\n },\n};\nconst obj3 = {\n a: {\n b: 1,\n },\n};\nconst obj4 = { __proto__: obj1 };\n\nassert.notDeepEqual(obj1, obj1);\n// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj2);\n// OK\n\nassert.notDeepEqual(obj1, obj3);\n// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj4);\n// OK\n
\nconst assert = require('node:assert');\n\nconst obj1 = {\n a: {\n b: 1,\n },\n};\nconst obj2 = {\n a: {\n b: 2,\n },\n};\nconst obj3 = {\n a: {\n b: 1,\n },\n};\nconst obj4 = { __proto__: obj1 };\n\nassert.notDeepEqual(obj1, obj1);\n// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj2);\n// OK\n\nassert.notDeepEqual(obj1, obj3);\n// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj4);\n// OK\n
\nIf the values are deeply equal, an AssertionError
is thrown with a\nmessage
property set equal to the value of the message
parameter. If the\nmessage
parameter is undefined, a default error message is assigned. If the\nmessage
parameter is an instance of an Error
then it will be thrown\ninstead of the AssertionError
.
Tests for deep strict inequality. Opposite of assert.deepStrictEqual()
.
import assert from 'node:assert/strict';\n\nassert.notDeepStrictEqual({ a: 1 }, { a: '1' });\n// OK\n
\nconst assert = require('node:assert/strict');\n\nassert.notDeepStrictEqual({ a: 1 }, { a: '1' });\n// OK\n
\nIf the values are deeply and strictly equal, an AssertionError
is thrown\nwith a message
property set equal to the value of the message
parameter. If\nthe message
parameter is undefined, a default error message is assigned. If\nthe message
parameter is an instance of an Error
then it will be thrown\ninstead of the AssertionError
.
Strict assertion mode
\nAn alias of assert.notStrictEqual()
.
Legacy assertion mode
\n\n\nStability: 3 - Legacy: Use
\nassert.notStrictEqual()
instead.
Tests shallow, coercive inequality with the !=
operator. NaN
is\nspecially handled and treated as being identical if both sides are NaN
.
import assert from 'node:assert';\n\nassert.notEqual(1, 2);\n// OK\n\nassert.notEqual(1, 1);\n// AssertionError: 1 != 1\n\nassert.notEqual(1, '1');\n// AssertionError: 1 != '1'\n
\nconst assert = require('node:assert');\n\nassert.notEqual(1, 2);\n// OK\n\nassert.notEqual(1, 1);\n// AssertionError: 1 != 1\n\nassert.notEqual(1, '1');\n// AssertionError: 1 != '1'\n
\nIf the values are equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned. If the message
\nparameter is an instance of an Error
then it will be thrown instead of the\nAssertionError
.
Tests strict inequality between the actual
and expected
parameters as\ndetermined by Object.is()
.
import assert from 'node:assert/strict';\n\nassert.notStrictEqual(1, 2);\n// OK\n\nassert.notStrictEqual(1, 1);\n// AssertionError [ERR_ASSERTION]: Expected \"actual\" to be strictly unequal to:\n//\n// 1\n\nassert.notStrictEqual(1, '1');\n// OK\n
\nconst assert = require('node:assert/strict');\n\nassert.notStrictEqual(1, 2);\n// OK\n\nassert.notStrictEqual(1, 1);\n// AssertionError [ERR_ASSERTION]: Expected \"actual\" to be strictly unequal to:\n//\n// 1\n\nassert.notStrictEqual(1, '1');\n// OK\n
\nIf the values are strictly equal, an AssertionError
is thrown with a\nmessage
property set equal to the value of the message
parameter. If the\nmessage
parameter is undefined, a default error message is assigned. If the\nmessage
parameter is an instance of an Error
then it will be thrown\ninstead of the AssertionError
.
Tests if value
is truthy. It is equivalent to\nassert.equal(!!value, true, message)
.
If value
is not truthy, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined
, a default error message is assigned. If the message
\nparameter is an instance of an Error
then it will be thrown instead of the\nAssertionError
.\nIf no arguments are passed in at all message
will be set to the string:\n'No value argument passed to `assert.ok()`'
.
Be aware that in the repl
the error message will be different to the one\nthrown in a file! See below for further details.
import assert from 'node:assert/strict';\n\nassert.ok(true);\n// OK\nassert.ok(1);\n// OK\n\nassert.ok();\n// AssertionError: No value argument passed to `assert.ok()`\n\nassert.ok(false, 'it\\'s false');\n// AssertionError: it's false\n\n// In the repl:\nassert.ok(typeof 123 === 'string');\n// AssertionError: false == true\n\n// In a file (e.g. test.js):\nassert.ok(typeof 123 === 'string');\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(typeof 123 === 'string')\n\nassert.ok(false);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(false)\n\nassert.ok(0);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(0)\n
\nconst assert = require('node:assert/strict');\n\nassert.ok(true);\n// OK\nassert.ok(1);\n// OK\n\nassert.ok();\n// AssertionError: No value argument passed to `assert.ok()`\n\nassert.ok(false, 'it\\'s false');\n// AssertionError: it's false\n\n// In the repl:\nassert.ok(typeof 123 === 'string');\n// AssertionError: false == true\n\n// In a file (e.g. test.js):\nassert.ok(typeof 123 === 'string');\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(typeof 123 === 'string')\n\nassert.ok(false);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(false)\n\nassert.ok(0);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(0)\n
\nimport assert from 'node:assert/strict';\n\n// Using `assert()` works the same:\nassert(0);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert(0)\n
\nconst assert = require('node:assert');\n\n// Using `assert()` works the same:\nassert(0);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert(0)\n
"
},
{
"textRaw": "`assert.rejects(asyncFn[, error][, message])`",
"type": "method",
"name": "rejects",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`asyncFn` {Function|Promise}",
"name": "asyncFn",
"type": "Function|Promise"
},
{
"textRaw": "`error` {RegExp|Function|Object|Error}",
"name": "error",
"type": "RegExp|Function|Object|Error"
},
{
"textRaw": "`message` {string}",
"name": "message",
"type": "string"
}
]
}
],
"desc": "Awaits the asyncFn
promise or, if asyncFn
is a function, immediately\ncalls the function and awaits the returned promise to complete. It will then\ncheck that the promise is rejected.
If asyncFn
is a function and it throws an error synchronously,\nassert.rejects()
will return a rejected Promise
with that error. If the\nfunction does not return a promise, assert.rejects()
will return a rejected\nPromise
with an ERR_INVALID_RETURN_VALUE
error. In both cases the error\nhandler is skipped.
Besides the async nature to await the completion behaves identically to\nassert.throws()
.
If specified, error
can be a Class
, RegExp
, a validation function,\nan object where each property will be tested for, or an instance of error where\neach property will be tested for including the non-enumerable message
and\nname
properties.
If specified, message
will be the message provided by the AssertionError
\nif the asyncFn
fails to reject.
import assert from 'node:assert/strict';\n\nawait assert.rejects(\n async () => {\n throw new TypeError('Wrong value');\n },\n {\n name: 'TypeError',\n message: 'Wrong value',\n },\n);\n
\nconst assert = require('node:assert/strict');\n\n(async () => {\n await assert.rejects(\n async () => {\n throw new TypeError('Wrong value');\n },\n {\n name: 'TypeError',\n message: 'Wrong value',\n },\n );\n})();\n
\nimport assert from 'node:assert/strict';\n\nawait assert.rejects(\n async () => {\n throw new TypeError('Wrong value');\n },\n (err) => {\n assert.strictEqual(err.name, 'TypeError');\n assert.strictEqual(err.message, 'Wrong value');\n return true;\n },\n);\n
\nconst assert = require('node:assert/strict');\n\n(async () => {\n await assert.rejects(\n async () => {\n throw new TypeError('Wrong value');\n },\n (err) => {\n assert.strictEqual(err.name, 'TypeError');\n assert.strictEqual(err.message, 'Wrong value');\n return true;\n },\n );\n})();\n
\nimport assert from 'node:assert/strict';\n\nassert.rejects(\n Promise.reject(new Error('Wrong value')),\n Error,\n).then(() => {\n // ...\n});\n
\nconst assert = require('node:assert/strict');\n\nassert.rejects(\n Promise.reject(new Error('Wrong value')),\n Error,\n).then(() => {\n // ...\n});\n
\nerror
cannot be a string. If a string is provided as the second\nargument, then error
is assumed to be omitted and the string will be used for\nmessage
instead. This can lead to easy-to-miss mistakes. Please read the\nexample in assert.throws()
carefully if using a string as the second\nargument gets considered.
Tests strict equality between the actual
and expected
parameters as\ndetermined by Object.is()
.
import assert from 'node:assert/strict';\n\nassert.strictEqual(1, 2);\n// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:\n//\n// 1 !== 2\n\nassert.strictEqual(1, 1);\n// OK\n\nassert.strictEqual('Hello foobar', 'Hello World!');\n// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:\n// + actual - expected\n//\n// + 'Hello foobar'\n// - 'Hello World!'\n// ^\n\nconst apples = 1;\nconst oranges = 2;\nassert.strictEqual(apples, oranges, `apples ${apples} !== oranges ${oranges}`);\n// AssertionError [ERR_ASSERTION]: apples 1 !== oranges 2\n\nassert.strictEqual(1, '1', new TypeError('Inputs are not identical'));\n// TypeError: Inputs are not identical\n
\nconst assert = require('node:assert/strict');\n\nassert.strictEqual(1, 2);\n// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:\n//\n// 1 !== 2\n\nassert.strictEqual(1, 1);\n// OK\n\nassert.strictEqual('Hello foobar', 'Hello World!');\n// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:\n// + actual - expected\n//\n// + 'Hello foobar'\n// - 'Hello World!'\n// ^\n\nconst apples = 1;\nconst oranges = 2;\nassert.strictEqual(apples, oranges, `apples ${apples} !== oranges ${oranges}`);\n// AssertionError [ERR_ASSERTION]: apples 1 !== oranges 2\n\nassert.strictEqual(1, '1', new TypeError('Inputs are not identical'));\n// TypeError: Inputs are not identical\n
\nIf the values are not strictly equal, an AssertionError
is thrown with a\nmessage
property set equal to the value of the message
parameter. If the\nmessage
parameter is undefined, a default error message is assigned. If the\nmessage
parameter is an instance of an Error
then it will be thrown\ninstead of the AssertionError
.
Expects the function fn
to throw an error.
If specified, error
can be a Class
, RegExp
, a validation function,\na validation object where each property will be tested for strict deep equality,\nor an instance of error where each property will be tested for strict deep\nequality including the non-enumerable message
and name
properties. When\nusing an object, it is also possible to use a regular expression, when\nvalidating against a string property. See below for examples.
If specified, message
will be appended to the message provided by the\nAssertionError
if the fn
call fails to throw or in case the error validation\nfails.
Custom validation object/error instance:
\nimport assert from 'node:assert/strict';\n\nconst err = new TypeError('Wrong value');\nerr.code = 404;\nerr.foo = 'bar';\nerr.info = {\n nested: true,\n baz: 'text',\n};\nerr.reg = /abc/i;\n\nassert.throws(\n () => {\n throw err;\n },\n {\n name: 'TypeError',\n message: 'Wrong value',\n info: {\n nested: true,\n baz: 'text',\n },\n // Only properties on the validation object will be tested for.\n // Using nested objects requires all properties to be present. Otherwise\n // the validation is going to fail.\n },\n);\n\n// Using regular expressions to validate error properties:\nassert.throws(\n () => {\n throw err;\n },\n {\n // The `name` and `message` properties are strings and using regular\n // expressions on those will match against the string. If they fail, an\n // error is thrown.\n name: /^TypeError$/,\n message: /Wrong/,\n foo: 'bar',\n info: {\n nested: true,\n // It is not possible to use regular expressions for nested properties!\n baz: 'text',\n },\n // The `reg` property contains a regular expression and only if the\n // validation object contains an identical regular expression, it is going\n // to pass.\n reg: /abc/i,\n },\n);\n\n// Fails due to the different `message` and `name` properties:\nassert.throws(\n () => {\n const otherErr = new Error('Not found');\n // Copy all enumerable properties from `err` to `otherErr`.\n for (const [key, value] of Object.entries(err)) {\n otherErr[key] = value;\n }\n throw otherErr;\n },\n // The error's `message` and `name` properties will also be checked when using\n // an error as validation object.\n err,\n);\n
\nconst assert = require('node:assert/strict');\n\nconst err = new TypeError('Wrong value');\nerr.code = 404;\nerr.foo = 'bar';\nerr.info = {\n nested: true,\n baz: 'text',\n};\nerr.reg = /abc/i;\n\nassert.throws(\n () => {\n throw err;\n },\n {\n name: 'TypeError',\n message: 'Wrong value',\n info: {\n nested: true,\n baz: 'text',\n },\n // Only properties on the validation object will be tested for.\n // Using nested objects requires all properties to be present. Otherwise\n // the validation is going to fail.\n },\n);\n\n// Using regular expressions to validate error properties:\nassert.throws(\n () => {\n throw err;\n },\n {\n // The `name` and `message` properties are strings and using regular\n // expressions on those will match against the string. If they fail, an\n // error is thrown.\n name: /^TypeError$/,\n message: /Wrong/,\n foo: 'bar',\n info: {\n nested: true,\n // It is not possible to use regular expressions for nested properties!\n baz: 'text',\n },\n // The `reg` property contains a regular expression and only if the\n // validation object contains an identical regular expression, it is going\n // to pass.\n reg: /abc/i,\n },\n);\n\n// Fails due to the different `message` and `name` properties:\nassert.throws(\n () => {\n const otherErr = new Error('Not found');\n // Copy all enumerable properties from `err` to `otherErr`.\n for (const [key, value] of Object.entries(err)) {\n otherErr[key] = value;\n }\n throw otherErr;\n },\n // The error's `message` and `name` properties will also be checked when using\n // an error as validation object.\n err,\n);\n
\nValidate instanceof using constructor:
\nimport assert from 'node:assert/strict';\n\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n Error,\n);\n
\nconst assert = require('node:assert/strict');\n\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n Error,\n);\n
\nValidate error message using RegExp
:
Using a regular expression runs .toString
on the error object, and will\ntherefore also include the error name.
import assert from 'node:assert/strict';\n\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n /^Error: Wrong value$/,\n);\n
\nconst assert = require('node:assert/strict');\n\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n /^Error: Wrong value$/,\n);\n
\nCustom error validation:
\nThe function must return true
to indicate all internal validations passed.\nIt will otherwise fail with an AssertionError
.
import assert from 'node:assert/strict';\n\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n (err) => {\n assert(err instanceof Error);\n assert(/value/.test(err));\n // Avoid returning anything from validation functions besides `true`.\n // Otherwise, it's not clear what part of the validation failed. Instead,\n // throw an error about the specific validation that failed (as done in this\n // example) and add as much helpful debugging information to that error as\n // possible.\n return true;\n },\n 'unexpected error',\n);\n
\nconst assert = require('node:assert/strict');\n\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n (err) => {\n assert(err instanceof Error);\n assert(/value/.test(err));\n // Avoid returning anything from validation functions besides `true`.\n // Otherwise, it's not clear what part of the validation failed. Instead,\n // throw an error about the specific validation that failed (as done in this\n // example) and add as much helpful debugging information to that error as\n // possible.\n return true;\n },\n 'unexpected error',\n);\n
\nerror
cannot be a string. If a string is provided as the second\nargument, then error
is assumed to be omitted and the string will be used for\nmessage
instead. This can lead to easy-to-miss mistakes. Using the same\nmessage as the thrown error message is going to result in an\nERR_AMBIGUOUS_ARGUMENT
error. Please read the example below carefully if using\na string as the second argument gets considered:
import assert from 'node:assert/strict';\n\nfunction throwingFirst() {\n throw new Error('First');\n}\n\nfunction throwingSecond() {\n throw new Error('Second');\n}\n\nfunction notThrowing() {}\n\n// The second argument is a string and the input function threw an Error.\n// The first case will not throw as it does not match for the error message\n// thrown by the input function!\nassert.throws(throwingFirst, 'Second');\n// In the next example the message has no benefit over the message from the\n// error and since it is not clear if the user intended to actually match\n// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.\nassert.throws(throwingSecond, 'Second');\n// TypeError [ERR_AMBIGUOUS_ARGUMENT]\n\n// The string is only used (as message) in case the function does not throw:\nassert.throws(notThrowing, 'Second');\n// AssertionError [ERR_ASSERTION]: Missing expected exception: Second\n\n// If it was intended to match for the error message do this instead:\n// It does not throw because the error messages match.\nassert.throws(throwingSecond, /Second$/);\n\n// If the error message does not match, an AssertionError is thrown.\nassert.throws(throwingFirst, /Second$/);\n// AssertionError [ERR_ASSERTION]\n
\nconst assert = require('node:assert/strict');\n\nfunction throwingFirst() {\n throw new Error('First');\n}\n\nfunction throwingSecond() {\n throw new Error('Second');\n}\n\nfunction notThrowing() {}\n\n// The second argument is a string and the input function threw an Error.\n// The first case will not throw as it does not match for the error message\n// thrown by the input function!\nassert.throws(throwingFirst, 'Second');\n// In the next example the message has no benefit over the message from the\n// error and since it is not clear if the user intended to actually match\n// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.\nassert.throws(throwingSecond, 'Second');\n// TypeError [ERR_AMBIGUOUS_ARGUMENT]\n\n// The string is only used (as message) in case the function does not throw:\nassert.throws(notThrowing, 'Second');\n// AssertionError [ERR_ASSERTION]: Missing expected exception: Second\n\n// If it was intended to match for the error message do this instead:\n// It does not throw because the error messages match.\nassert.throws(throwingSecond, /Second$/);\n\n// If the error message does not match, an AssertionError is thrown.\nassert.throws(throwingFirst, /Second$/);\n// AssertionError [ERR_ASSERTION]\n
\nDue to the confusing error-prone notation, avoid a string as the second\nargument.
" } ], "type": "module", "displayName": "Assert", "source": "doc/api/assert.md" }, { "textRaw": "Asynchronous context tracking", "name": "asynchronous_context_tracking", "introduced_in": "v16.4.0", "stability": 2, "stabilityText": "Stable", "desc": "Source Code: lib/async_hooks.js
", "modules": [ { "textRaw": "Introduction", "name": "introduction", "desc": "These classes are used to associate state and propagate it throughout\ncallbacks and promise chains.\nThey allow storing data throughout the lifetime of a web request\nor any other asynchronous duration. It is similar to thread-local storage\nin other languages.
\nThe AsyncLocalStorage
and AsyncResource
classes are part of the\nnode:async_hooks
module:
import { AsyncLocalStorage, AsyncResource } from 'node:async_hooks';\n
\nconst { AsyncLocalStorage, AsyncResource } = require('node:async_hooks');\n
",
"type": "module",
"displayName": "Introduction"
}
],
"classes": [
{
"textRaw": "Class: `AsyncLocalStorage`",
"type": "class",
"name": "AsyncLocalStorage",
"meta": {
"added": [
"v13.10.0",
"v12.17.0"
],
"changes": [
{
"version": "v16.4.0",
"pr-url": "https://github.com/nodejs/node/pull/37675",
"description": "AsyncLocalStorage is now Stable. Previously, it had been Experimental."
}
]
},
"desc": "This class creates stores that stay coherent through asynchronous operations.
\nWhile you can create your own implementation on top of the node:async_hooks
\nmodule, AsyncLocalStorage
should be preferred as it is a performant and memory\nsafe implementation that involves significant optimizations that are non-obvious\nto implement.
The following example uses AsyncLocalStorage
to build a simple logger\nthat assigns IDs to incoming HTTP requests and includes them in messages\nlogged within each request.
import http from 'node:http';\nimport { AsyncLocalStorage } from 'node:async_hooks';\n\nconst asyncLocalStorage = new AsyncLocalStorage();\n\nfunction logWithId(msg) {\n const id = asyncLocalStorage.getStore();\n console.log(`${id !== undefined ? id : '-'}:`, msg);\n}\n\nlet idSeq = 0;\nhttp.createServer((req, res) => {\n asyncLocalStorage.run(idSeq++, () => {\n logWithId('start');\n // Imagine any chain of async operations here\n setImmediate(() => {\n logWithId('finish');\n res.end();\n });\n });\n}).listen(8080);\n\nhttp.get('http://localhost:8080');\nhttp.get('http://localhost:8080');\n// Prints:\n// 0: start\n// 1: start\n// 0: finish\n// 1: finish\n
\nconst http = require('node:http');\nconst { AsyncLocalStorage } = require('node:async_hooks');\n\nconst asyncLocalStorage = new AsyncLocalStorage();\n\nfunction logWithId(msg) {\n const id = asyncLocalStorage.getStore();\n console.log(`${id !== undefined ? id : '-'}:`, msg);\n}\n\nlet idSeq = 0;\nhttp.createServer((req, res) => {\n asyncLocalStorage.run(idSeq++, () => {\n logWithId('start');\n // Imagine any chain of async operations here\n setImmediate(() => {\n logWithId('finish');\n res.end();\n });\n });\n}).listen(8080);\n\nhttp.get('http://localhost:8080');\nhttp.get('http://localhost:8080');\n// Prints:\n// 0: start\n// 1: start\n// 0: finish\n// 1: finish\n
\nEach instance of AsyncLocalStorage
maintains an independent storage context.\nMultiple instances can safely exist simultaneously without risk of interfering\nwith each other's data.
Binds the given function to the current execution context.
" }, { "textRaw": "Static method: `AsyncLocalStorage.snapshot()`", "type": "classMethod", "name": "snapshot", "meta": { "added": [ "v19.8.0", "v18.16.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {Function} A new function with the signature `(fn: (...args) : R, ...args) : R`.", "name": "return", "type": "Function", "desc": "A new function with the signature `(fn: (...args) : R, ...args) : R`." }, "params": [] } ], "desc": "Captures the current execution context and returns a function that accepts a\nfunction as an argument. Whenever the returned function is called, it\ncalls the function passed to it within the captured context.
\nconst asyncLocalStorage = new AsyncLocalStorage();\nconst runInAsyncScope = asyncLocalStorage.run(123, () => AsyncLocalStorage.snapshot());\nconst result = asyncLocalStorage.run(321, () => runInAsyncScope(() => asyncLocalStorage.getStore()));\nconsole.log(result); // returns 123\n
\nAsyncLocalStorage.snapshot() can replace the use of AsyncResource for simple\nasync context tracking purposes, for example:
\nclass Foo {\n #runInAsyncScope = AsyncLocalStorage.snapshot();\n\n get() { return this.#runInAsyncScope(() => asyncLocalStorage.getStore()); }\n}\n\nconst foo = asyncLocalStorage.run(123, () => new Foo());\nconsole.log(asyncLocalStorage.run(321, () => foo.get())); // returns 123\n
"
}
],
"methods": [
{
"textRaw": "`asyncLocalStorage.disable()`",
"type": "method",
"name": "disable",
"meta": {
"added": [
"v13.10.0",
"v12.17.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": []
}
],
"desc": "Disables the instance of AsyncLocalStorage
. All subsequent calls\nto asyncLocalStorage.getStore()
will return undefined
until\nasyncLocalStorage.run()
or asyncLocalStorage.enterWith()
is called again.
When calling asyncLocalStorage.disable()
, all current contexts linked to the\ninstance will be exited.
Calling asyncLocalStorage.disable()
is required before the\nasyncLocalStorage
can be garbage collected. This does not apply to stores\nprovided by the asyncLocalStorage
, as those objects are garbage collected\nalong with the corresponding async resources.
Use this method when the asyncLocalStorage
is not in use anymore\nin the current process.
Returns the current store.\nIf called outside of an asynchronous context initialized by\ncalling asyncLocalStorage.run()
or asyncLocalStorage.enterWith()
, it\nreturns undefined
.
Transitions into the context for the remainder of the current\nsynchronous execution and then persists the store through any following\nasynchronous calls.
\nExample:
\nconst store = { id: 1 };\n// Replaces previous store with the given store object\nasyncLocalStorage.enterWith(store);\nasyncLocalStorage.getStore(); // Returns the store object\nsomeAsyncOperation(() => {\n asyncLocalStorage.getStore(); // Returns the same object\n});\n
\nThis transition will continue for the entire synchronous execution.\nThis means that if, for example, the context is entered within an event\nhandler subsequent event handlers will also run within that context unless\nspecifically bound to another context with an AsyncResource
. That is why\nrun()
should be preferred over enterWith()
unless there are strong reasons\nto use the latter method.
const store = { id: 1 };\n\nemitter.on('my-event', () => {\n asyncLocalStorage.enterWith(store);\n});\nemitter.on('my-event', () => {\n asyncLocalStorage.getStore(); // Returns the same object\n});\n\nasyncLocalStorage.getStore(); // Returns undefined\nemitter.emit('my-event');\nasyncLocalStorage.getStore(); // Returns the same object\n
"
},
{
"textRaw": "`asyncLocalStorage.run(store, callback[, ...args])`",
"type": "method",
"name": "run",
"meta": {
"added": [
"v13.10.0",
"v12.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`store` {any}",
"name": "store",
"type": "any"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any"
}
]
}
],
"desc": "Runs a function synchronously within a context and returns its\nreturn value. The store is not accessible outside of the callback function.\nThe store is accessible to any asynchronous operations created within the\ncallback.
\nThe optional args
are passed to the callback function.
If the callback function throws an error, the error is thrown by run()
too.\nThe stacktrace is not impacted by this call and the context is exited.
Example:
\nconst store = { id: 2 };\ntry {\n asyncLocalStorage.run(store, () => {\n asyncLocalStorage.getStore(); // Returns the store object\n setTimeout(() => {\n asyncLocalStorage.getStore(); // Returns the store object\n }, 200);\n throw new Error();\n });\n} catch (e) {\n asyncLocalStorage.getStore(); // Returns undefined\n // The error will be caught here\n}\n
"
},
{
"textRaw": "`asyncLocalStorage.exit(callback[, ...args])`",
"type": "method",
"name": "exit",
"meta": {
"added": [
"v13.10.0",
"v12.17.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": [
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any"
}
]
}
],
"desc": "Runs a function synchronously outside of a context and returns its\nreturn value. The store is not accessible within the callback function or\nthe asynchronous operations created within the callback. Any getStore()
\ncall done within the callback function will always return undefined
.
The optional args
are passed to the callback function.
If the callback function throws an error, the error is thrown by exit()
too.\nThe stacktrace is not impacted by this call and the context is re-entered.
Example:
\n// Within a call to run\ntry {\n asyncLocalStorage.getStore(); // Returns the store object or value\n asyncLocalStorage.exit(() => {\n asyncLocalStorage.getStore(); // Returns undefined\n throw new Error();\n });\n} catch (e) {\n asyncLocalStorage.getStore(); // Returns the same object or value\n // The error will be caught here\n}\n
"
}
],
"modules": [
{
"textRaw": "Usage with `async/await`",
"name": "usage_with_`async/await`",
"desc": "If, within an async function, only one await
call is to run within a context,\nthe following pattern should be used:
async function fn() {\n await asyncLocalStorage.run(new Map(), () => {\n asyncLocalStorage.getStore().set('key', value);\n return foo(); // The return value of foo will be awaited\n });\n}\n
\nIn this example, the store is only available in the callback function and the\nfunctions called by foo
. Outside of run
, calling getStore
will return\nundefined
.
In most cases, AsyncLocalStorage
works without issues. In rare situations, the\ncurrent store is lost in one of the asynchronous operations.
If your code is callback-based, it is enough to promisify it with\nutil.promisify()
so it starts working with native promises.
If you need to use a callback-based API or your code assumes\na custom thenable implementation, use the AsyncResource
class\nto associate the asynchronous operation with the correct execution context.\nFind the function call responsible for the context loss by logging the content\nof asyncLocalStorage.getStore()
after the calls you suspect are responsible\nfor the loss. When the code logs undefined
, the last callback called is\nprobably responsible for the context loss.
Creates a new instance of AsyncLocalStorage
. Store is only provided within a\nrun()
call or after an enterWith()
call.
The class AsyncResource
is designed to be extended by the embedder's async\nresources. Using this, users can easily trigger the lifetime events of their\nown resources.
The init
hook will trigger when an AsyncResource
is instantiated.
The following is an overview of the AsyncResource
API.
import { AsyncResource, executionAsyncId } from 'node:async_hooks';\n\n// AsyncResource() is meant to be extended. Instantiating a\n// new AsyncResource() also triggers init. If triggerAsyncId is omitted then\n// async_hook.executionAsyncId() is used.\nconst asyncResource = new AsyncResource(\n type, { triggerAsyncId: executionAsyncId(), requireManualDestroy: false },\n);\n\n// Run a function in the execution context of the resource. This will\n// * establish the context of the resource\n// * trigger the AsyncHooks before callbacks\n// * call the provided function `fn` with the supplied arguments\n// * trigger the AsyncHooks after callbacks\n// * restore the original execution context\nasyncResource.runInAsyncScope(fn, thisArg, ...args);\n\n// Call AsyncHooks destroy callbacks.\nasyncResource.emitDestroy();\n\n// Return the unique ID assigned to the AsyncResource instance.\nasyncResource.asyncId();\n\n// Return the trigger ID for the AsyncResource instance.\nasyncResource.triggerAsyncId();\n
\nconst { AsyncResource, executionAsyncId } = require('node:async_hooks');\n\n// AsyncResource() is meant to be extended. Instantiating a\n// new AsyncResource() also triggers init. If triggerAsyncId is omitted then\n// async_hook.executionAsyncId() is used.\nconst asyncResource = new AsyncResource(\n type, { triggerAsyncId: executionAsyncId(), requireManualDestroy: false },\n);\n\n// Run a function in the execution context of the resource. This will\n// * establish the context of the resource\n// * trigger the AsyncHooks before callbacks\n// * call the provided function `fn` with the supplied arguments\n// * trigger the AsyncHooks after callbacks\n// * restore the original execution context\nasyncResource.runInAsyncScope(fn, thisArg, ...args);\n\n// Call AsyncHooks destroy callbacks.\nasyncResource.emitDestroy();\n\n// Return the unique ID assigned to the AsyncResource instance.\nasyncResource.asyncId();\n\n// Return the trigger ID for the AsyncResource instance.\nasyncResource.triggerAsyncId();\n
",
"classMethods": [
{
"textRaw": "Static method: `AsyncResource.bind(fn[, type[, thisArg]])`",
"type": "classMethod",
"name": "bind",
"meta": {
"added": [
"v14.8.0",
"v12.19.0"
],
"changes": [
{
"version": "v20.0.0",
"pr-url": "https://github.com/nodejs/node/pull/46432",
"description": "The `asyncResource` property added to the bound function has been deprecated and will be removed in a future version."
},
{
"version": [
"v17.8.0",
"v16.15.0"
],
"pr-url": "https://github.com/nodejs/node/pull/42177",
"description": "Changed the default when `thisArg` is undefined to use `this` from the caller."
},
{
"version": "v16.0.0",
"pr-url": "https://github.com/nodejs/node/pull/36782",
"description": "Added optional thisArg."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function} The function to bind to the current execution context.",
"name": "fn",
"type": "Function",
"desc": "The function to bind to the current execution context."
},
{
"textRaw": "`type` {string} An optional name to associate with the underlying `AsyncResource`.",
"name": "type",
"type": "string",
"desc": "An optional name to associate with the underlying `AsyncResource`."
},
{
"textRaw": "`thisArg` {any}",
"name": "thisArg",
"type": "any"
}
]
}
],
"desc": "Binds the given function to the current execution context.
" } ], "methods": [ { "textRaw": "`asyncResource.bind(fn[, thisArg])`", "type": "method", "name": "bind", "meta": { "added": [ "v14.8.0", "v12.19.0" ], "changes": [ { "version": "v20.0.0", "pr-url": "https://github.com/nodejs/node/pull/46432", "description": "The `asyncResource` property added to the bound function has been deprecated and will be removed in a future version." }, { "version": [ "v17.8.0", "v16.15.0" ], "pr-url": "https://github.com/nodejs/node/pull/42177", "description": "Changed the default when `thisArg` is undefined to use `this` from the caller." }, { "version": "v16.0.0", "pr-url": "https://github.com/nodejs/node/pull/36782", "description": "Added optional thisArg." } ] }, "signatures": [ { "params": [ { "textRaw": "`fn` {Function} The function to bind to the current `AsyncResource`.", "name": "fn", "type": "Function", "desc": "The function to bind to the current `AsyncResource`." }, { "textRaw": "`thisArg` {any}", "name": "thisArg", "type": "any" } ] } ], "desc": "Binds the given function to execute to this AsyncResource
's scope.
Call the provided function with the provided arguments in the execution context\nof the async resource. This will establish the context, trigger the AsyncHooks\nbefore callbacks, call the function, trigger the AsyncHooks after callbacks, and\nthen restore the original execution context.
" }, { "textRaw": "`asyncResource.emitDestroy()`", "type": "method", "name": "emitDestroy", "signatures": [ { "return": { "textRaw": "Returns: {AsyncResource} A reference to `asyncResource`.", "name": "return", "type": "AsyncResource", "desc": "A reference to `asyncResource`." }, "params": [] } ], "desc": "Call all destroy
hooks. This should only ever be called once. An error will\nbe thrown if it is called more than once. This must be manually called. If\nthe resource is left to be collected by the GC then the destroy
hooks will\nnever be called.
The following example shows how to use the AsyncResource
class to properly\nprovide async tracking for a Worker
pool. Other resource pools, such as\ndatabase connection pools, can follow a similar model.
Assuming that the task is adding two numbers, using a file named\ntask_processor.js
with the following content:
import { parentPort } from 'node:worker_threads';\nparentPort.on('message', (task) => {\n parentPort.postMessage(task.a + task.b);\n});\n
\nconst { parentPort } = require('node:worker_threads');\nparentPort.on('message', (task) => {\n parentPort.postMessage(task.a + task.b);\n});\n
\na Worker pool around it could use the following structure:
\nimport { AsyncResource } from 'node:async_hooks';\nimport { EventEmitter } from 'node:events';\nimport path from 'node:path';\nimport { Worker } from 'node:worker_threads';\n\nconst kTaskInfo = Symbol('kTaskInfo');\nconst kWorkerFreedEvent = Symbol('kWorkerFreedEvent');\n\nclass WorkerPoolTaskInfo extends AsyncResource {\n constructor(callback) {\n super('WorkerPoolTaskInfo');\n this.callback = callback;\n }\n\n done(err, result) {\n this.runInAsyncScope(this.callback, null, err, result);\n this.emitDestroy(); // `TaskInfo`s are used only once.\n }\n}\n\nexport default class WorkerPool extends EventEmitter {\n constructor(numThreads) {\n super();\n this.numThreads = numThreads;\n this.workers = [];\n this.freeWorkers = [];\n this.tasks = [];\n\n for (let i = 0; i < numThreads; i++)\n this.addNewWorker();\n\n // Any time the kWorkerFreedEvent is emitted, dispatch\n // the next task pending in the queue, if any.\n this.on(kWorkerFreedEvent, () => {\n if (this.tasks.length > 0) {\n const { task, callback } = this.tasks.shift();\n this.runTask(task, callback);\n }\n });\n }\n\n addNewWorker() {\n const worker = new Worker(new URL('task_processor.js', import.meta.url));\n worker.on('message', (result) => {\n // In case of success: Call the callback that was passed to `runTask`,\n // remove the `TaskInfo` associated with the Worker, and mark it as free\n // again.\n worker[kTaskInfo].done(null, result);\n worker[kTaskInfo] = null;\n this.freeWorkers.push(worker);\n this.emit(kWorkerFreedEvent);\n });\n worker.on('error', (err) => {\n // In case of an uncaught exception: Call the callback that was passed to\n // `runTask` with the error.\n if (worker[kTaskInfo])\n worker[kTaskInfo].done(err, null);\n else\n this.emit('error', err);\n // Remove the worker from the list and start a new Worker to replace the\n // current one.\n this.workers.splice(this.workers.indexOf(worker), 1);\n this.addNewWorker();\n });\n this.workers.push(worker);\n this.freeWorkers.push(worker);\n this.emit(kWorkerFreedEvent);\n }\n\n runTask(task, callback) {\n if (this.freeWorkers.length === 0) {\n // No free threads, wait until a worker thread becomes free.\n this.tasks.push({ task, callback });\n return;\n }\n\n const worker = this.freeWorkers.pop();\n worker[kTaskInfo] = new WorkerPoolTaskInfo(callback);\n worker.postMessage(task);\n }\n\n close() {\n for (const worker of this.workers) worker.terminate();\n }\n}\n
\nconst { AsyncResource } = require('node:async_hooks');\nconst { EventEmitter } = require('node:events');\nconst path = require('node:path');\nconst { Worker } = require('node:worker_threads');\n\nconst kTaskInfo = Symbol('kTaskInfo');\nconst kWorkerFreedEvent = Symbol('kWorkerFreedEvent');\n\nclass WorkerPoolTaskInfo extends AsyncResource {\n constructor(callback) {\n super('WorkerPoolTaskInfo');\n this.callback = callback;\n }\n\n done(err, result) {\n this.runInAsyncScope(this.callback, null, err, result);\n this.emitDestroy(); // `TaskInfo`s are used only once.\n }\n}\n\nclass WorkerPool extends EventEmitter {\n constructor(numThreads) {\n super();\n this.numThreads = numThreads;\n this.workers = [];\n this.freeWorkers = [];\n this.tasks = [];\n\n for (let i = 0; i < numThreads; i++)\n this.addNewWorker();\n\n // Any time the kWorkerFreedEvent is emitted, dispatch\n // the next task pending in the queue, if any.\n this.on(kWorkerFreedEvent, () => {\n if (this.tasks.length > 0) {\n const { task, callback } = this.tasks.shift();\n this.runTask(task, callback);\n }\n });\n }\n\n addNewWorker() {\n const worker = new Worker(path.resolve(__dirname, 'task_processor.js'));\n worker.on('message', (result) => {\n // In case of success: Call the callback that was passed to `runTask`,\n // remove the `TaskInfo` associated with the Worker, and mark it as free\n // again.\n worker[kTaskInfo].done(null, result);\n worker[kTaskInfo] = null;\n this.freeWorkers.push(worker);\n this.emit(kWorkerFreedEvent);\n });\n worker.on('error', (err) => {\n // In case of an uncaught exception: Call the callback that was passed to\n // `runTask` with the error.\n if (worker[kTaskInfo])\n worker[kTaskInfo].done(err, null);\n else\n this.emit('error', err);\n // Remove the worker from the list and start a new Worker to replace the\n // current one.\n this.workers.splice(this.workers.indexOf(worker), 1);\n this.addNewWorker();\n });\n this.workers.push(worker);\n this.freeWorkers.push(worker);\n this.emit(kWorkerFreedEvent);\n }\n\n runTask(task, callback) {\n if (this.freeWorkers.length === 0) {\n // No free threads, wait until a worker thread becomes free.\n this.tasks.push({ task, callback });\n return;\n }\n\n const worker = this.freeWorkers.pop();\n worker[kTaskInfo] = new WorkerPoolTaskInfo(callback);\n worker.postMessage(task);\n }\n\n close() {\n for (const worker of this.workers) worker.terminate();\n }\n}\n\nmodule.exports = WorkerPool;\n
\nWithout the explicit tracking added by the WorkerPoolTaskInfo
objects,\nit would appear that the callbacks are associated with the individual Worker
\nobjects. However, the creation of the Worker
s is not associated with the\ncreation of the tasks and does not provide information about when tasks\nwere scheduled.
This pool could be used as follows:
\nimport WorkerPool from './worker_pool.js';\nimport os from 'node:os';\n\nconst pool = new WorkerPool(os.availableParallelism());\n\nlet finished = 0;\nfor (let i = 0; i < 10; i++) {\n pool.runTask({ a: 42, b: 100 }, (err, result) => {\n console.log(i, err, result);\n if (++finished === 10)\n pool.close();\n });\n}\n
\nconst WorkerPool = require('./worker_pool.js');\nconst os = require('node:os');\n\nconst pool = new WorkerPool(os.availableParallelism());\n\nlet finished = 0;\nfor (let i = 0; i < 10; i++) {\n pool.runTask({ a: 42, b: 100 }, (err, result) => {\n console.log(i, err, result);\n if (++finished === 10)\n pool.close();\n });\n}\n
",
"type": "module",
"displayName": "Using `AsyncResource` for a `Worker` thread pool"
},
{
"textRaw": "Integrating `AsyncResource` with `EventEmitter`",
"name": "integrating_`asyncresource`_with_`eventemitter`",
"desc": "Event listeners triggered by an EventEmitter
may be run in a different\nexecution context than the one that was active when eventEmitter.on()
was\ncalled.
The following example shows how to use the AsyncResource
class to properly\nassociate an event listener with the correct execution context. The same\napproach can be applied to a Stream
or a similar event-driven class.
import { createServer } from 'node:http';\nimport { AsyncResource, executionAsyncId } from 'node:async_hooks';\n\nconst server = createServer((req, res) => {\n req.on('close', AsyncResource.bind(() => {\n // Execution context is bound to the current outer scope.\n }));\n req.on('close', () => {\n // Execution context is bound to the scope that caused 'close' to emit.\n });\n res.end();\n}).listen(3000);\n
\nconst { createServer } = require('node:http');\nconst { AsyncResource, executionAsyncId } = require('node:async_hooks');\n\nconst server = createServer((req, res) => {\n req.on('close', AsyncResource.bind(() => {\n // Execution context is bound to the current outer scope.\n }));\n req.on('close', () => {\n // Execution context is bound to the scope that caused 'close' to emit.\n });\n res.end();\n}).listen(3000);\n
",
"type": "module",
"displayName": "Integrating `AsyncResource` with `EventEmitter`"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`type` {string} The type of async event.",
"name": "type",
"type": "string",
"desc": "The type of async event."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`triggerAsyncId` {number} The ID of the execution context that created this async event. **Default:** `executionAsyncId()`.",
"name": "triggerAsyncId",
"type": "number",
"default": "`executionAsyncId()`",
"desc": "The ID of the execution context that created this async event."
},
{
"textRaw": "`requireManualDestroy` {boolean} If set to `true`, disables `emitDestroy` when the object is garbage collected. This usually does not need to be set (even if `emitDestroy` is called manually), unless the resource's `asyncId` is retrieved and the sensitive API's `emitDestroy` is called with it. When set to `false`, the `emitDestroy` call on garbage collection will only take place if there is at least one active `destroy` hook. **Default:** `false`.",
"name": "requireManualDestroy",
"type": "boolean",
"default": "`false`",
"desc": "If set to `true`, disables `emitDestroy` when the object is garbage collected. This usually does not need to be set (even if `emitDestroy` is called manually), unless the resource's `asyncId` is retrieved and the sensitive API's `emitDestroy` is called with it. When set to `false`, the `emitDestroy` call on garbage collection will only take place if there is at least one active `destroy` hook."
}
]
}
],
"desc": "Example usage:
\nclass DBQuery extends AsyncResource {\n constructor(db) {\n super('DBQuery');\n this.db = db;\n }\n\n getInfo(query, callback) {\n this.db.get(query, (err, data) => {\n this.runInAsyncScope(callback, null, err, data);\n });\n }\n\n close() {\n this.db = null;\n this.emitDestroy();\n }\n}\n
"
}
]
}
],
"type": "module",
"displayName": "Asynchronous context tracking",
"source": "doc/api/async_context.md"
},
{
"textRaw": "Async hooks",
"name": "async_hooks",
"introduced_in": "v8.1.0",
"stability": 1,
"stabilityText": "Experimental. Please migrate away from this API, if you can. We do not recommend using the [`createHook`][], [`AsyncHook`][], and [`executionAsyncResource`][] APIs as they have usability issues, safety risks, and performance implications. Async context tracking use cases are better served by the stable [`AsyncLocalStorage`][] API. If you have a use case for `createHook`, `AsyncHook`, or `executionAsyncResource` beyond the context tracking need solved by [`AsyncLocalStorage`][] or diagnostics data currently provided by [Diagnostics Channel][], please open an issue at https://github.com/nodejs/node/issues describing your use case so we can create a more purpose-focused API.",
"desc": "Source Code: lib/async_hooks.js
\nWe strongly discourage the use of the async_hooks
API.\nOther APIs that can cover most of its use cases include:
AsyncLocalStorage
tracks async contextprocess.getActiveResourcesInfo()
tracks active resourcesThe node:async_hooks
module provides an API to track asynchronous resources.\nIt can be accessed using:
import async_hooks from 'node:async_hooks';\n
\nconst async_hooks = require('node:async_hooks');\n
",
"modules": [
{
"textRaw": "Terminology",
"name": "terminology",
"desc": "An asynchronous resource represents an object with an associated callback.\nThis callback may be called multiple times, such as the 'connection'
\nevent in net.createServer()
, or just a single time like in fs.open()
.\nA resource can also be closed before the callback is called. AsyncHook
does\nnot explicitly distinguish between these different cases but will represent them\nas the abstract concept that is a resource.
If Worker
s are used, each thread has an independent async_hooks
\ninterface, and each thread will use a new set of async IDs.
Following is a simple overview of the public API.
\nimport async_hooks from 'node:async_hooks';\n\n// Return the ID of the current execution context.\nconst eid = async_hooks.executionAsyncId();\n\n// Return the ID of the handle responsible for triggering the callback of the\n// current execution scope to call.\nconst tid = async_hooks.triggerAsyncId();\n\n// Create a new AsyncHook instance. All of these callbacks are optional.\nconst asyncHook =\n async_hooks.createHook({ init, before, after, destroy, promiseResolve });\n\n// Allow callbacks of this AsyncHook instance to call. This is not an implicit\n// action after running the constructor, and must be explicitly run to begin\n// executing callbacks.\nasyncHook.enable();\n\n// Disable listening for new asynchronous events.\nasyncHook.disable();\n\n//\n// The following are the callbacks that can be passed to createHook().\n//\n\n// init() is called during object construction. The resource may not have\n// completed construction when this callback runs. Therefore, all fields of the\n// resource referenced by \"asyncId\" may not have been populated.\nfunction init(asyncId, type, triggerAsyncId, resource) { }\n\n// before() is called just before the resource's callback is called. It can be\n// called 0-N times for handles (such as TCPWrap), and will be called exactly 1\n// time for requests (such as FSReqCallback).\nfunction before(asyncId) { }\n\n// after() is called just after the resource's callback has finished.\nfunction after(asyncId) { }\n\n// destroy() is called when the resource is destroyed.\nfunction destroy(asyncId) { }\n\n// promiseResolve() is called only for promise resources, when the\n// resolve() function passed to the Promise constructor is invoked\n// (either directly or through other means of resolving a promise).\nfunction promiseResolve(asyncId) { }\n
\nconst async_hooks = require('node:async_hooks');\n\n// Return the ID of the current execution context.\nconst eid = async_hooks.executionAsyncId();\n\n// Return the ID of the handle responsible for triggering the callback of the\n// current execution scope to call.\nconst tid = async_hooks.triggerAsyncId();\n\n// Create a new AsyncHook instance. All of these callbacks are optional.\nconst asyncHook =\n async_hooks.createHook({ init, before, after, destroy, promiseResolve });\n\n// Allow callbacks of this AsyncHook instance to call. This is not an implicit\n// action after running the constructor, and must be explicitly run to begin\n// executing callbacks.\nasyncHook.enable();\n\n// Disable listening for new asynchronous events.\nasyncHook.disable();\n\n//\n// The following are the callbacks that can be passed to createHook().\n//\n\n// init() is called during object construction. The resource may not have\n// completed construction when this callback runs. Therefore, all fields of the\n// resource referenced by \"asyncId\" may not have been populated.\nfunction init(asyncId, type, triggerAsyncId, resource) { }\n\n// before() is called just before the resource's callback is called. It can be\n// called 0-N times for handles (such as TCPWrap), and will be called exactly 1\n// time for requests (such as FSReqCallback).\nfunction before(asyncId) { }\n\n// after() is called just after the resource's callback has finished.\nfunction after(asyncId) { }\n\n// destroy() is called when the resource is destroyed.\nfunction destroy(asyncId) { }\n\n// promiseResolve() is called only for promise resources, when the\n// resolve() function passed to the Promise constructor is invoked\n// (either directly or through other means of resolving a promise).\nfunction promiseResolve(asyncId) { }\n
",
"type": "module",
"displayName": "Overview"
},
{
"textRaw": "Promise execution tracking",
"name": "promise_execution_tracking",
"desc": "By default, promise executions are not assigned asyncId
s due to the relatively\nexpensive nature of the promise introspection API provided by\nV8. This means that programs using promises or async
/await
will not get\ncorrect execution and trigger ids for promise callback contexts by default.
import { executionAsyncId, triggerAsyncId } from 'node:async_hooks';\n\nPromise.resolve(1729).then(() => {\n console.log(`eid ${executionAsyncId()} tid ${triggerAsyncId()}`);\n});\n// produces:\n// eid 1 tid 0\n
\nconst { executionAsyncId, triggerAsyncId } = require('node:async_hooks');\n\nPromise.resolve(1729).then(() => {\n console.log(`eid ${executionAsyncId()} tid ${triggerAsyncId()}`);\n});\n// produces:\n// eid 1 tid 0\n
\nObserve that the then()
callback claims to have executed in the context of the\nouter scope even though there was an asynchronous hop involved. Also,\nthe triggerAsyncId
value is 0
, which means that we are missing context about\nthe resource that caused (triggered) the then()
callback to be executed.
Installing async hooks via async_hooks.createHook
enables promise execution\ntracking:
import { createHook, executionAsyncId, triggerAsyncId } from 'node:async_hooks';\ncreateHook({ init() {} }).enable(); // forces PromiseHooks to be enabled.\nPromise.resolve(1729).then(() => {\n console.log(`eid ${executionAsyncId()} tid ${triggerAsyncId()}`);\n});\n// produces:\n// eid 7 tid 6\n
\nconst { createHook, executionAsyncId, triggerAsyncId } = require('node:async_hooks');\n\ncreateHook({ init() {} }).enable(); // forces PromiseHooks to be enabled.\nPromise.resolve(1729).then(() => {\n console.log(`eid ${executionAsyncId()} tid ${triggerAsyncId()}`);\n});\n// produces:\n// eid 7 tid 6\n
\nIn this example, adding any actual hook function enabled the tracking of\npromises. There are two promises in the example above; the promise created by\nPromise.resolve()
and the promise returned by the call to then()
. In the\nexample above, the first promise got the asyncId
6
and the latter got\nasyncId
7
. During the execution of the then()
callback, we are executing\nin the context of promise with asyncId
7
. This promise was triggered by\nasync resource 6
.
Another subtlety with promises is that before
and after
callbacks are run\nonly on chained promises. That means promises not created by then()
/catch()
\nwill not have the before
and after
callbacks fired on them. For more details\nsee the details of the V8 PromiseHooks API.
Library developers that handle their own asynchronous resources performing tasks\nlike I/O, connection pooling, or managing callback queues may use the\nAsyncResource
JavaScript API so that all the appropriate callbacks are called.
The documentation for this class has moved AsyncResource
.
Registers functions to be called for different lifetime events of each async\noperation.
\nThe callbacks init()
/before()
/after()
/destroy()
are called for the\nrespective asynchronous event during a resource's lifetime.
All callbacks are optional. For example, if only resource cleanup needs to\nbe tracked, then only the destroy
callback needs to be passed. The\nspecifics of all functions that can be passed to callbacks
is in the\nHook Callbacks section.
import { createHook } from 'node:async_hooks';\n\nconst asyncHook = createHook({\n init(asyncId, type, triggerAsyncId, resource) { },\n destroy(asyncId) { },\n});\n
\nconst async_hooks = require('node:async_hooks');\n\nconst asyncHook = async_hooks.createHook({\n init(asyncId, type, triggerAsyncId, resource) { },\n destroy(asyncId) { },\n});\n
\nThe callbacks will be inherited via the prototype chain:
\nclass MyAsyncCallbacks {\n init(asyncId, type, triggerAsyncId, resource) { }\n destroy(asyncId) {}\n}\n\nclass MyAddedCallbacks extends MyAsyncCallbacks {\n before(asyncId) { }\n after(asyncId) { }\n}\n\nconst asyncHook = async_hooks.createHook(new MyAddedCallbacks());\n
\nBecause promises are asynchronous resources whose lifecycle is tracked\nvia the async hooks mechanism, the init()
, before()
, after()
, and\ndestroy()
callbacks must not be async functions that return promises.
If any AsyncHook
callbacks throw, the application will print the stack trace\nand exit. The exit path does follow that of an uncaught exception, but\nall 'uncaughtException'
listeners are removed, thus forcing the process to\nexit. The 'exit'
callbacks will still be called unless the application is run\nwith --abort-on-uncaught-exception
, in which case a stack trace will be\nprinted and the application exits, leaving a core file.
The reason for this error handling behavior is that these callbacks are running\nat potentially volatile points in an object's lifetime, for example during\nclass construction and destruction. Because of this, it is deemed necessary to\nbring down the process quickly in order to prevent an unintentional abort in the\nfuture. This is subject to change in the future if a comprehensive analysis is\nperformed to ensure an exception can follow the normal control flow without\nunintentional side effects.
", "type": "module", "displayName": "Error handling" }, { "textRaw": "Printing in `AsyncHook` callbacks", "name": "printing_in_`asynchook`_callbacks", "desc": "Because printing to the console is an asynchronous operation, console.log()
\nwill cause AsyncHook
callbacks to be called. Using console.log()
or\nsimilar asynchronous operations inside an AsyncHook
callback function will\ncause an infinite recursion. An easy solution to this when debugging is to use a\nsynchronous logging operation such as fs.writeFileSync(file, msg, flag)
.\nThis will print to the file and will not invoke AsyncHook
recursively because\nit is synchronous.
import { writeFileSync } from 'node:fs';\nimport { format } from 'node:util';\n\nfunction debug(...args) {\n // Use a function like this one when debugging inside an AsyncHook callback\n writeFileSync('log.out', `${format(...args)}\\n`, { flag: 'a' });\n}\n
\nconst fs = require('node:fs');\nconst util = require('node:util');\n\nfunction debug(...args) {\n // Use a function like this one when debugging inside an AsyncHook callback\n fs.writeFileSync('log.out', `${util.format(...args)}\\n`, { flag: 'a' });\n}\n
\nIf an asynchronous operation is needed for logging, it is possible to keep\ntrack of what caused the asynchronous operation using the information\nprovided by AsyncHook
itself. The logging should then be skipped when\nit was the logging itself that caused the AsyncHook
callback to be called. By\ndoing this, the otherwise infinite recursion is broken.
The class AsyncHook
exposes an interface for tracking lifetime events\nof asynchronous operations.
Enable the callbacks for a given AsyncHook
instance. If no callbacks are\nprovided, enabling is a no-op.
The AsyncHook
instance is disabled by default. If the AsyncHook
instance\nshould be enabled immediately after creation, the following pattern can be used.
import { createHook } from 'node:async_hooks';\n\nconst hook = createHook(callbacks).enable();\n
\nconst async_hooks = require('node:async_hooks');\n\nconst hook = async_hooks.createHook(callbacks).enable();\n
"
},
{
"textRaw": "`asyncHook.disable()`",
"type": "method",
"name": "disable",
"signatures": [
{
"return": {
"textRaw": "Returns: {AsyncHook} A reference to `asyncHook`.",
"name": "return",
"type": "AsyncHook",
"desc": "A reference to `asyncHook`."
},
"params": []
}
],
"desc": "Disable the callbacks for a given AsyncHook
instance from the global pool of\nAsyncHook
callbacks to be executed. Once a hook has been disabled it will not\nbe called again until enabled.
For API consistency disable()
also returns the AsyncHook
instance.
Resource objects returned by executionAsyncResource()
are most often internal\nNode.js handle objects with undocumented APIs. Using any functions or properties\non the object is likely to crash your application and should be avoided.
Using executionAsyncResource()
in the top-level execution context will\nreturn an empty object as there is no handle or request object to use,\nbut having an object representing the top-level can be helpful.
import { open } from 'node:fs';\nimport { executionAsyncId, executionAsyncResource } from 'node:async_hooks';\n\nconsole.log(executionAsyncId(), executionAsyncResource()); // 1 {}\nopen(new URL(import.meta.url), 'r', (err, fd) => {\n console.log(executionAsyncId(), executionAsyncResource()); // 7 FSReqWrap\n});\n
\nconst { open } = require('node:fs');\nconst { executionAsyncId, executionAsyncResource } = require('node:async_hooks');\n\nconsole.log(executionAsyncId(), executionAsyncResource()); // 1 {}\nopen(__filename, 'r', (err, fd) => {\n console.log(executionAsyncId(), executionAsyncResource()); // 7 FSReqWrap\n});\n
\nThis can be used to implement continuation local storage without the\nuse of a tracking Map
to store the metadata:
import { createServer } from 'node:http';\nimport {\n executionAsyncId,\n executionAsyncResource,\n createHook,\n} from 'async_hooks';\nconst sym = Symbol('state'); // Private symbol to avoid pollution\n\ncreateHook({\n init(asyncId, type, triggerAsyncId, resource) {\n const cr = executionAsyncResource();\n if (cr) {\n resource[sym] = cr[sym];\n }\n },\n}).enable();\n\nconst server = createServer((req, res) => {\n executionAsyncResource()[sym] = { state: req.url };\n setTimeout(function() {\n res.end(JSON.stringify(executionAsyncResource()[sym]));\n }, 100);\n}).listen(3000);\n
\nconst { createServer } = require('node:http');\nconst {\n executionAsyncId,\n executionAsyncResource,\n createHook,\n} = require('node:async_hooks');\nconst sym = Symbol('state'); // Private symbol to avoid pollution\n\ncreateHook({\n init(asyncId, type, triggerAsyncId, resource) {\n const cr = executionAsyncResource();\n if (cr) {\n resource[sym] = cr[sym];\n }\n },\n}).enable();\n\nconst server = createServer((req, res) => {\n executionAsyncResource()[sym] = { state: req.url };\n setTimeout(function() {\n res.end(JSON.stringify(executionAsyncResource()[sym]));\n }, 100);\n}).listen(3000);\n
"
},
{
"textRaw": "`async_hooks.executionAsyncId()`",
"type": "method",
"name": "executionAsyncId",
"meta": {
"added": [
"v8.1.0"
],
"changes": [
{
"version": "v8.2.0",
"pr-url": "https://github.com/nodejs/node/pull/13490",
"description": "Renamed from `currentId`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number} The `asyncId` of the current execution context. Useful to track when something calls.",
"name": "return",
"type": "number",
"desc": "The `asyncId` of the current execution context. Useful to track when something calls."
},
"params": []
}
],
"desc": "import { executionAsyncId } from 'node:async_hooks';\nimport fs from 'node:fs';\n\nconsole.log(executionAsyncId()); // 1 - bootstrap\nconst path = '.';\nfs.open(path, 'r', (err, fd) => {\n console.log(executionAsyncId()); // 6 - open()\n});\n
\nconst async_hooks = require('node:async_hooks');\nconst fs = require('node:fs');\n\nconsole.log(async_hooks.executionAsyncId()); // 1 - bootstrap\nconst path = '.';\nfs.open(path, 'r', (err, fd) => {\n console.log(async_hooks.executionAsyncId()); // 6 - open()\n});\n
\nThe ID returned from executionAsyncId()
is related to execution timing, not\ncausality (which is covered by triggerAsyncId()
):
const server = net.createServer((conn) => {\n // Returns the ID of the server, not of the new connection, because the\n // callback runs in the execution scope of the server's MakeCallback().\n async_hooks.executionAsyncId();\n\n}).listen(port, () => {\n // Returns the ID of a TickObject (process.nextTick()) because all\n // callbacks passed to .listen() are wrapped in a nextTick().\n async_hooks.executionAsyncId();\n});\n
\nPromise contexts may not get precise executionAsyncIds
by default.\nSee the section on promise execution tracking.
const server = net.createServer((conn) => {\n // The resource that caused (or triggered) this callback to be called\n // was that of the new connection. Thus the return value of triggerAsyncId()\n // is the asyncId of \"conn\".\n async_hooks.triggerAsyncId();\n\n}).listen(port, () => {\n // Even though all callbacks passed to .listen() are wrapped in a nextTick()\n // the callback itself exists because the call to the server's .listen()\n // was made. So the return value would be the ID of the server.\n async_hooks.triggerAsyncId();\n});\n
\nPromise contexts may not get valid triggerAsyncId
s by default. See\nthe section on promise execution tracking.
Key events in the lifetime of asynchronous events have been categorized into\nfour areas: instantiation, before/after the callback is called, and when the\ninstance is destroyed.
", "methods": [ { "textRaw": "`init(asyncId, type, triggerAsyncId, resource)`", "type": "method", "name": "init", "signatures": [ { "params": [ { "textRaw": "`asyncId` {number} A unique ID for the async resource.", "name": "asyncId", "type": "number", "desc": "A unique ID for the async resource." }, { "textRaw": "`type` {string} The type of the async resource.", "name": "type", "type": "string", "desc": "The type of the async resource." }, { "textRaw": "`triggerAsyncId` {number} The unique ID of the async resource in whose execution context this async resource was created.", "name": "triggerAsyncId", "type": "number", "desc": "The unique ID of the async resource in whose execution context this async resource was created." }, { "textRaw": "`resource` {Object} Reference to the resource representing the async operation, needs to be released during _destroy_.", "name": "resource", "type": "Object", "desc": "Reference to the resource representing the async operation, needs to be released during _destroy_." } ] } ], "desc": "Called when a class is constructed that has the possibility to emit an\nasynchronous event. This does not mean the instance must call\nbefore
/after
before destroy
is called, only that the possibility\nexists.
This behavior can be observed by doing something like opening a resource then\nclosing it before the resource can be used. The following snippet demonstrates\nthis.
\nimport { createServer } from 'node:net';\n\ncreateServer().listen(function() { this.close(); });\n// OR\nclearTimeout(setTimeout(() => {}, 10));\n
\nrequire('node:net').createServer().listen(function() { this.close(); });\n// OR\nclearTimeout(setTimeout(() => {}, 10));\n
\nEvery new resource is assigned an ID that is unique within the scope of the\ncurrent Node.js instance.
", "modules": [ { "textRaw": "`type`", "name": "`type`", "desc": "The type
is a string identifying the type of resource that caused\ninit
to be called. Generally, it will correspond to the name of the\nresource's constructor.
The type
of resources created by Node.js itself can change in any Node.js\nrelease. Valid values include TLSWRAP
,\nTCPWRAP
, TCPSERVERWRAP
, GETADDRINFOREQWRAP
, FSREQCALLBACK
,\nMicrotask
, and Timeout
. Inspect the source code of the Node.js version used\nto get the full list.
Furthermore users of AsyncResource
create async resources independent\nof Node.js itself.
There is also the PROMISE
resource type, which is used to track Promise
\ninstances and asynchronous work scheduled by them.
Users are able to define their own type
when using the public embedder API.
It is possible to have type name collisions. Embedders are encouraged to use\nunique prefixes, such as the npm package name, to prevent collisions when\nlistening to the hooks.
", "type": "module", "displayName": "`type`" }, { "textRaw": "`triggerAsyncId`", "name": "`triggerasyncid`", "desc": "triggerAsyncId
is the asyncId
of the resource that caused (or \"triggered\")\nthe new resource to initialize and that caused init
to call. This is different\nfrom async_hooks.executionAsyncId()
that only shows when a resource was\ncreated, while triggerAsyncId
shows why a resource was created.
The following is a simple demonstration of triggerAsyncId
:
import { createHook, executionAsyncId } from 'node:async_hooks';\nimport { stdout } from 'node:process';\nimport net from 'node:net';\nimport fs from 'node:fs';\n\ncreateHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = executionAsyncId();\n fs.writeSync(\n stdout.fd,\n `${type}(${asyncId}): trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n },\n}).enable();\n\nnet.createServer((conn) => {}).listen(8080);\n
\nconst { createHook, executionAsyncId } = require('node:async_hooks');\nconst { stdout } = require('node:process');\nconst net = require('node:net');\nconst fs = require('node:fs');\n\ncreateHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = executionAsyncId();\n fs.writeSync(\n stdout.fd,\n `${type}(${asyncId}): trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n },\n}).enable();\n\nnet.createServer((conn) => {}).listen(8080);\n
\nOutput when hitting the server with nc localhost 8080
:
TCPSERVERWRAP(5): trigger: 1 execution: 1\nTCPWRAP(7): trigger: 5 execution: 0\n
\nThe TCPSERVERWRAP
is the server which receives the connections.
The TCPWRAP
is the new connection from the client. When a new\nconnection is made, the TCPWrap
instance is immediately constructed. This\nhappens outside of any JavaScript stack. (An executionAsyncId()
of 0
means\nthat it is being executed from C++ with no JavaScript stack above it.) With only\nthat information, it would be impossible to link resources together in\nterms of what caused them to be created, so triggerAsyncId
is given the task\nof propagating what resource is responsible for the new resource's existence.
resource
is an object that represents the actual async resource that has\nbeen initialized. The API to access the object may be specified by the\ncreator of the resource. Resources created by Node.js itself are internal\nand may change at any time. Therefore no API is specified for these.
In some cases the resource object is reused for performance reasons, it is\nthus not safe to use it as a key in a WeakMap
or add properties to it.
The context tracking use case is covered by the stable API AsyncLocalStorage
.\nThis example only illustrates async hooks operation but AsyncLocalStorage
\nfits better to this use case.
The following is an example with additional information about the calls to\ninit
between the before
and after
calls, specifically what the\ncallback to listen()
will look like. The output formatting is slightly more\nelaborate to make calling context easier to see.
import async_hooks from 'node:async_hooks';\nimport fs from 'node:fs';\nimport net from 'node:net';\nimport { stdout } from 'node:process';\nconst { fd } = stdout;\n\nlet indent = 0;\nasync_hooks.createHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = async_hooks.executionAsyncId();\n const indentStr = ' '.repeat(indent);\n fs.writeSync(\n fd,\n `${indentStr}${type}(${asyncId}):` +\n ` trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n },\n before(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeSync(fd, `${indentStr}before: ${asyncId}\\n`);\n indent += 2;\n },\n after(asyncId) {\n indent -= 2;\n const indentStr = ' '.repeat(indent);\n fs.writeSync(fd, `${indentStr}after: ${asyncId}\\n`);\n },\n destroy(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeSync(fd, `${indentStr}destroy: ${asyncId}\\n`);\n },\n}).enable();\n\nnet.createServer(() => {}).listen(8080, () => {\n // Let's wait 10ms before logging the server started.\n setTimeout(() => {\n console.log('>>>', async_hooks.executionAsyncId());\n }, 10);\n});\n
\nconst async_hooks = require('node:async_hooks');\nconst fs = require('node:fs');\nconst net = require('node:net');\nconst { fd } = process.stdout;\n\nlet indent = 0;\nasync_hooks.createHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = async_hooks.executionAsyncId();\n const indentStr = ' '.repeat(indent);\n fs.writeSync(\n fd,\n `${indentStr}${type}(${asyncId}):` +\n ` trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n },\n before(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeSync(fd, `${indentStr}before: ${asyncId}\\n`);\n indent += 2;\n },\n after(asyncId) {\n indent -= 2;\n const indentStr = ' '.repeat(indent);\n fs.writeSync(fd, `${indentStr}after: ${asyncId}\\n`);\n },\n destroy(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeSync(fd, `${indentStr}destroy: ${asyncId}\\n`);\n },\n}).enable();\n\nnet.createServer(() => {}).listen(8080, () => {\n // Let's wait 10ms before logging the server started.\n setTimeout(() => {\n console.log('>>>', async_hooks.executionAsyncId());\n }, 10);\n});\n
\nOutput from only starting the server:
\nTCPSERVERWRAP(5): trigger: 1 execution: 1\nTickObject(6): trigger: 5 execution: 1\nbefore: 6\n Timeout(7): trigger: 6 execution: 6\nafter: 6\ndestroy: 6\nbefore: 7\n>>> 7\n TickObject(8): trigger: 7 execution: 7\nafter: 7\nbefore: 8\nafter: 8\n
\nAs illustrated in the example, executionAsyncId()
and execution
each specify\nthe value of the current execution context; which is delineated by calls to\nbefore
and after
.
Only using execution
to graph resource allocation results in the following:
root(1)\n ^\n |\nTickObject(6)\n ^\n |\n Timeout(7)\n
\nThe TCPSERVERWRAP
is not part of this graph, even though it was the reason for\nconsole.log()
being called. This is because binding to a port without a host\nname is a synchronous operation, but to maintain a completely asynchronous\nAPI the user's callback is placed in a process.nextTick()
. Which is why\nTickObject
is present in the output and is a 'parent' for .listen()
\ncallback.
The graph only shows when a resource was created, not why, so to track\nthe why use triggerAsyncId
. Which can be represented with the following\ngraph:
bootstrap(1)\n |\n ˅\nTCPSERVERWRAP(5)\n |\n ˅\n TickObject(6)\n |\n ˅\n Timeout(7)\n
",
"type": "module",
"displayName": "Asynchronous context example"
}
]
},
{
"textRaw": "`before(asyncId)`",
"type": "method",
"name": "before",
"signatures": [
{
"params": [
{
"textRaw": "`asyncId` {number}",
"name": "asyncId",
"type": "number"
}
]
}
],
"desc": "When an asynchronous operation is initiated (such as a TCP server receiving a\nnew connection) or completes (such as writing data to disk) a callback is\ncalled to notify the user. The before
callback is called just before said\ncallback is executed. asyncId
is the unique identifier assigned to the\nresource about to execute the callback.
The before
callback will be called 0 to N times. The before
callback\nwill typically be called 0 times if the asynchronous operation was cancelled\nor, for example, if no connections are received by a TCP server. Persistent\nasynchronous resources like a TCP server will typically call the before
\ncallback multiple times, while other operations like fs.open()
will call\nit only once.
Called immediately after the callback specified in before
is completed.
If an uncaught exception occurs during execution of the callback, then after
\nwill run after the 'uncaughtException'
event is emitted or a domain
's\nhandler runs.
Called after the resource corresponding to asyncId
is destroyed. It is also\ncalled asynchronously from the embedder API emitDestroy()
.
Some resources depend on garbage collection for cleanup, so if a reference is\nmade to the resource
object passed to init
it is possible that destroy
\nwill never be called, causing a memory leak in the application. If the resource\ndoes not depend on garbage collection, then this will not be an issue.
Using the destroy hook results in additional overhead because it enables\ntracking of Promise
instances via the garbage collector.
Called when the resolve
function passed to the Promise
constructor is\ninvoked (either directly or through other means of resolving a promise).
resolve()
does not do any observable synchronous work.
The Promise
is not necessarily fulfilled or rejected at this point if the\nPromise
was resolved by assuming the state of another Promise
.
new Promise((resolve) => resolve(true)).then((a) => {});\n
\ncalls the following callbacks:
\ninit for PROMISE with id 5, trigger id: 1\n promise resolve 5 # corresponds to resolve(true)\ninit for PROMISE with id 6, trigger id: 5 # the Promise returned by then()\n before 6 # the then() callback is entered\n promise resolve 6 # the then() callback resolves the promise by returning\n after 6\n
"
}
],
"type": "module",
"displayName": "Hook callbacks"
}
],
"properties": [
{
"textRaw": "`asyncWrapProviders` Returns: A map of provider types to the corresponding numeric id. This map contains all the event types that might be emitted by the `async_hooks.init()` event.",
"name": "return",
"meta": {
"added": [
"v17.2.0",
"v16.14.0"
],
"changes": []
},
"desc": "This feature suppresses the deprecated usage of process.binding('async_wrap').Providers
.\nSee: DEP0111
The documentation for this class has moved AsyncLocalStorage
.
Source Code: lib/buffer.js
\nBuffer
objects are used to represent a fixed-length sequence of bytes. Many\nNode.js APIs support Buffer
s.
The Buffer
class is a subclass of JavaScript's Uint8Array
class and\nextends it with methods that cover additional use cases. Node.js APIs accept\nplain Uint8Array
s wherever Buffer
s are supported as well.
While the Buffer
class is available within the global scope, it is still\nrecommended to explicitly reference it via an import or require statement.
import { Buffer } from 'node:buffer';\n\n// Creates a zero-filled Buffer of length 10.\nconst buf1 = Buffer.alloc(10);\n\n// Creates a Buffer of length 10,\n// filled with bytes which all have the value `1`.\nconst buf2 = Buffer.alloc(10, 1);\n\n// Creates an uninitialized buffer of length 10.\n// This is faster than calling Buffer.alloc() but the returned\n// Buffer instance might contain old data that needs to be\n// overwritten using fill(), write(), or other functions that fill the Buffer's\n// contents.\nconst buf3 = Buffer.allocUnsafe(10);\n\n// Creates a Buffer containing the bytes [1, 2, 3].\nconst buf4 = Buffer.from([1, 2, 3]);\n\n// Creates a Buffer containing the bytes [1, 1, 1, 1] – the entries\n// are all truncated using `(value & 255)` to fit into the range 0–255.\nconst buf5 = Buffer.from([257, 257.5, -255, '1']);\n\n// Creates a Buffer containing the UTF-8-encoded bytes for the string 'tést':\n// [0x74, 0xc3, 0xa9, 0x73, 0x74] (in hexadecimal notation)\n// [116, 195, 169, 115, 116] (in decimal notation)\nconst buf6 = Buffer.from('tést');\n\n// Creates a Buffer containing the Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].\nconst buf7 = Buffer.from('tést', 'latin1');\n
\nconst { Buffer } = require('node:buffer');\n\n// Creates a zero-filled Buffer of length 10.\nconst buf1 = Buffer.alloc(10);\n\n// Creates a Buffer of length 10,\n// filled with bytes which all have the value `1`.\nconst buf2 = Buffer.alloc(10, 1);\n\n// Creates an uninitialized buffer of length 10.\n// This is faster than calling Buffer.alloc() but the returned\n// Buffer instance might contain old data that needs to be\n// overwritten using fill(), write(), or other functions that fill the Buffer's\n// contents.\nconst buf3 = Buffer.allocUnsafe(10);\n\n// Creates a Buffer containing the bytes [1, 2, 3].\nconst buf4 = Buffer.from([1, 2, 3]);\n\n// Creates a Buffer containing the bytes [1, 1, 1, 1] – the entries\n// are all truncated using `(value & 255)` to fit into the range 0–255.\nconst buf5 = Buffer.from([257, 257.5, -255, '1']);\n\n// Creates a Buffer containing the UTF-8-encoded bytes for the string 'tést':\n// [0x74, 0xc3, 0xa9, 0x73, 0x74] (in hexadecimal notation)\n// [116, 195, 169, 115, 116] (in decimal notation)\nconst buf6 = Buffer.from('tést');\n\n// Creates a Buffer containing the Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].\nconst buf7 = Buffer.from('tést', 'latin1');\n
",
"modules": [
{
"textRaw": "Buffers and character encodings",
"name": "buffers_and_character_encodings",
"meta": {
"changes": [
{
"version": [
"v15.7.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/36952",
"description": "Introduced `base64url` encoding."
},
{
"version": "v6.4.0",
"pr-url": "https://github.com/nodejs/node/pull/7111",
"description": "Introduced `latin1` as an alias for `binary`."
},
{
"version": "v5.0.0",
"pr-url": "https://github.com/nodejs/node/pull/2859",
"description": "Removed the deprecated `raw` and `raws` encodings."
}
]
},
"desc": "When converting between Buffer
s and strings, a character encoding may be\nspecified. If no character encoding is specified, UTF-8 will be used as the\ndefault.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('hello world', 'utf8');\n\nconsole.log(buf.toString('hex'));\n// Prints: 68656c6c6f20776f726c64\nconsole.log(buf.toString('base64'));\n// Prints: aGVsbG8gd29ybGQ=\n\nconsole.log(Buffer.from('fhqwhgads', 'utf8'));\n// Prints: <Buffer 66 68 71 77 68 67 61 64 73>\nconsole.log(Buffer.from('fhqwhgads', 'utf16le'));\n// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('hello world', 'utf8');\n\nconsole.log(buf.toString('hex'));\n// Prints: 68656c6c6f20776f726c64\nconsole.log(buf.toString('base64'));\n// Prints: aGVsbG8gd29ybGQ=\n\nconsole.log(Buffer.from('fhqwhgads', 'utf8'));\n// Prints: <Buffer 66 68 71 77 68 67 61 64 73>\nconsole.log(Buffer.from('fhqwhgads', 'utf16le'));\n// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>\n
\nNode.js buffers accept all case variations of encoding strings that they\nreceive. For example, UTF-8 can be specified as 'utf8'
, 'UTF8'
, or 'uTf8'
.
The character encodings currently supported by Node.js are the following:
\n'utf8'
(alias: 'utf-8'
): Multi-byte encoded Unicode characters. Many web\npages and other document formats use UTF-8. This is the default character\nencoding. When decoding a Buffer
into a string that does not exclusively\ncontain valid UTF-8 data, the Unicode replacement character U+FFFD
� will be\nused to represent those errors.
'utf16le'
(alias: 'utf-16le'
): Multi-byte encoded Unicode characters.\nUnlike 'utf8'
, each character in the string will be encoded using either 2\nor 4 bytes. Node.js only supports the little-endian variant of\nUTF-16.
'latin1'
: Latin-1 stands for ISO-8859-1. This character encoding only\nsupports the Unicode characters from U+0000
to U+00FF
. Each character is\nencoded using a single byte. Characters that do not fit into that range are\ntruncated and will be mapped to characters in that range.
Converting a Buffer
into a string using one of the above is referred to as\ndecoding, and converting a string into a Buffer
is referred to as encoding.
Node.js also supports the following binary-to-text encodings. For\nbinary-to-text encodings, the naming convention is reversed: Converting a\nBuffer
into a string is typically referred to as encoding, and converting a\nstring into a Buffer
as decoding.
'base64'
: Base64 encoding. When creating a Buffer
from a string,\nthis encoding will also correctly accept \"URL and Filename Safe Alphabet\" as\nspecified in RFC 4648, Section 5. Whitespace characters such as spaces,\ntabs, and new lines contained within the base64-encoded string are ignored.
'base64url'
: base64url encoding as specified in\nRFC 4648, Section 5. When creating a Buffer
from a string, this\nencoding will also correctly accept regular base64-encoded strings. When\nencoding a Buffer
to a string, this encoding will omit padding.
'hex'
: Encode each byte as two hexadecimal characters. Data truncation\nmay occur when decoding strings that do not exclusively consist of an even\nnumber of hexadecimal characters. See below for an example.
The following legacy character encodings are also supported:
\n'ascii'
: For 7-bit ASCII data only. When encoding a string into a\nBuffer
, this is equivalent to using 'latin1'
. When decoding a Buffer
\ninto a string, using this encoding will additionally unset the highest bit of\neach byte before decoding as 'latin1'
.\nGenerally, there should be no reason to use this encoding, as 'utf8'
\n(or, if the data is known to always be ASCII-only, 'latin1'
) will be a\nbetter choice when encoding or decoding ASCII-only text. It is only provided\nfor legacy compatibility.
'binary'
: Alias for 'latin1'
.\nThe name of this encoding can be very misleading, as all of the\nencodings listed here convert between strings and binary data. For converting\nbetween strings and Buffer
s, typically 'utf8'
is the right choice.
'ucs2'
, 'ucs-2'
: Aliases of 'utf16le'
. UCS-2 used to refer to a variant\nof UTF-16 that did not support characters that had code points larger than\nU+FFFF. In Node.js, these code points are always supported.
import { Buffer } from 'node:buffer';\n\nBuffer.from('1ag123', 'hex');\n// Prints <Buffer 1a>, data truncated when first non-hexadecimal value\n// ('g') encountered.\n\nBuffer.from('1a7', 'hex');\n// Prints <Buffer 1a>, data truncated when data ends in single digit ('7').\n\nBuffer.from('1634', 'hex');\n// Prints <Buffer 16 34>, all data represented.\n
\nconst { Buffer } = require('node:buffer');\n\nBuffer.from('1ag123', 'hex');\n// Prints <Buffer 1a>, data truncated when first non-hexadecimal value\n// ('g') encountered.\n\nBuffer.from('1a7', 'hex');\n// Prints <Buffer 1a>, data truncated when data ends in single digit ('7').\n\nBuffer.from('1634', 'hex');\n// Prints <Buffer 16 34>, all data represented.\n
\nModern Web browsers follow the WHATWG Encoding Standard which aliases\nboth 'latin1'
and 'ISO-8859-1'
to 'win-1252'
. This means that while doing\nsomething like http.get()
, if the returned charset is one of those listed in\nthe WHATWG specification it is possible that the server actually returned\n'win-1252'
-encoded data, and using 'latin1'
encoding may incorrectly decode\nthe characters.
Buffer
instances are also JavaScript Uint8Array
and TypedArray
\ninstances. All TypedArray
methods are available on Buffer
s. There are,\nhowever, subtle incompatibilities between the Buffer
API and the\nTypedArray
API.
In particular:
\nTypedArray.prototype.slice()
creates a copy of part of the TypedArray
,\nBuffer.prototype.slice()
creates a view over the existing Buffer
\nwithout copying. This behavior can be surprising, and only exists for legacy\ncompatibility. TypedArray.prototype.subarray()
can be used to achieve\nthe behavior of Buffer.prototype.slice()
on both Buffer
s\nand other TypedArray
s and should be preferred.buf.toString()
is incompatible with its TypedArray
equivalent.buf.indexOf()
, support additional arguments.There are two ways to create new TypedArray
instances from a Buffer
:
Buffer
to a TypedArray
constructor will copy the Buffer
s\ncontents, interpreted as an array of integers, and not as a byte sequence\nof the target type.import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, 2, 3, 4]);\nconst uint32array = new Uint32Array(buf);\n\nconsole.log(uint32array);\n\n// Prints: Uint32Array(4) [ 1, 2, 3, 4 ]\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, 2, 3, 4]);\nconst uint32array = new Uint32Array(buf);\n\nconsole.log(uint32array);\n\n// Prints: Uint32Array(4) [ 1, 2, 3, 4 ]\n
\nBuffer
s underlying ArrayBuffer
will create a\nTypedArray
that shares its memory with the Buffer
.import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('hello', 'utf16le');\nconst uint16array = new Uint16Array(\n buf.buffer,\n buf.byteOffset,\n buf.length / Uint16Array.BYTES_PER_ELEMENT);\n\nconsole.log(uint16array);\n\n// Prints: Uint16Array(5) [ 104, 101, 108, 108, 111 ]\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('hello', 'utf16le');\nconst uint16array = new Uint16Array(\n buf.buffer,\n buf.byteOffset,\n buf.length / Uint16Array.BYTES_PER_ELEMENT);\n\nconsole.log(uint16array);\n\n// Prints: Uint16Array(5) [ 104, 101, 108, 108, 111 ]\n
\nIt is possible to create a new Buffer
that shares the same allocated\nmemory as a TypedArray
instance by using the TypedArray
object's\n.buffer
property in the same way. Buffer.from()
\nbehaves like new Uint8Array()
in this context.
import { Buffer } from 'node:buffer';\n\nconst arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Copies the contents of `arr`.\nconst buf1 = Buffer.from(arr);\n\n// Shares memory with `arr`.\nconst buf2 = Buffer.from(arr.buffer);\n\nconsole.log(buf1);\n// Prints: <Buffer 88 a0>\nconsole.log(buf2);\n// Prints: <Buffer 88 13 a0 0f>\n\narr[1] = 6000;\n\nconsole.log(buf1);\n// Prints: <Buffer 88 a0>\nconsole.log(buf2);\n// Prints: <Buffer 88 13 70 17>\n
\nconst { Buffer } = require('node:buffer');\n\nconst arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Copies the contents of `arr`.\nconst buf1 = Buffer.from(arr);\n\n// Shares memory with `arr`.\nconst buf2 = Buffer.from(arr.buffer);\n\nconsole.log(buf1);\n// Prints: <Buffer 88 a0>\nconsole.log(buf2);\n// Prints: <Buffer 88 13 a0 0f>\n\narr[1] = 6000;\n\nconsole.log(buf1);\n// Prints: <Buffer 88 a0>\nconsole.log(buf2);\n// Prints: <Buffer 88 13 70 17>\n
\nWhen creating a Buffer
using a TypedArray
's .buffer
, it is\npossible to use only a portion of the underlying ArrayBuffer
by passing in\nbyteOffset
and length
parameters.
import { Buffer } from 'node:buffer';\n\nconst arr = new Uint16Array(20);\nconst buf = Buffer.from(arr.buffer, 0, 16);\n\nconsole.log(buf.length);\n// Prints: 16\n
\nconst { Buffer } = require('node:buffer');\n\nconst arr = new Uint16Array(20);\nconst buf = Buffer.from(arr.buffer, 0, 16);\n\nconsole.log(buf.length);\n// Prints: 16\n
\nThe Buffer.from()
and TypedArray.from()
have different signatures and\nimplementations. Specifically, the TypedArray
variants accept a second\nargument that is a mapping function that is invoked on every element of the\ntyped array:
TypedArray.from(source[, mapFn[, thisArg]])
The Buffer.from()
method, however, does not support the use of a mapping\nfunction:
Buffer.from(array)
Buffer.from(buffer)
Buffer.from(arrayBuffer[, byteOffset[, length]])
Buffer.from(string[, encoding])
Buffer
instances can be iterated over using for..of
syntax:
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, 2, 3]);\n\nfor (const b of buf) {\n console.log(b);\n}\n// Prints:\n// 1\n// 2\n// 3\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, 2, 3]);\n\nfor (const b of buf) {\n console.log(b);\n}\n// Prints:\n// 1\n// 2\n// 3\n
\nAdditionally, the buf.values()
, buf.keys()
, and\nbuf.entries()
methods can be used to create iterators.
While, the Buffer
object is available as a global, there are additional\nBuffer
-related APIs that are available only via the node:buffer
module\naccessed using require('node:buffer')
.
Decodes a string of Base64-encoded data into bytes, and encodes those bytes\ninto a string using Latin-1 (ISO-8859-1).
\nThe data
may be any JavaScript-value that can be coerced into a string.
This function is only provided for compatibility with legacy web platform APIs\nand should never be used in new code, because they use strings to represent\nbinary data and predate the introduction of typed arrays in JavaScript.\nFor code running using Node.js APIs, converting between base64-encoded strings\nand binary data should be performed using Buffer.from(str, 'base64')
and\nbuf.toString('base64')
.
Decodes a string into bytes using Latin-1 (ISO-8859), and encodes those bytes\ninto a string using Base64.
\nThe data
may be any JavaScript-value that can be coerced into a string.
This function is only provided for compatibility with legacy web platform APIs\nand should never be used in new code, because they use strings to represent\nbinary data and predate the introduction of typed arrays in JavaScript.\nFor code running using Node.js APIs, converting between base64-encoded strings\nand binary data should be performed using Buffer.from(str, 'base64')
and\nbuf.toString('base64')
.
This function returns true
if input
contains only valid ASCII-encoded data,\nincluding the case in which input
is empty.
Throws if the input
is a detached array buffer.
This function returns true
if input
contains only valid UTF-8-encoded data,\nincluding the case in which input
is empty.
Throws if the input
is a detached array buffer.
Resolves a 'blob:nodedata:...'
an associated <Blob> object registered using\na prior call to URL.createObjectURL()
.
Re-encodes the given Buffer
or Uint8Array
instance from one character\nencoding to another. Returns a new Buffer
instance.
Throws if the fromEnc
or toEnc
specify invalid character encodings or if\nconversion from fromEnc
to toEnc
is not permitted.
Encodings supported by buffer.transcode()
are: 'ascii'
, 'utf8'
,\n'utf16le'
, 'ucs2'
, 'latin1'
, and 'binary'
.
The transcoding process will use substitution characters if a given byte\nsequence cannot be adequately represented in the target encoding. For instance:
\nimport { Buffer, transcode } from 'node:buffer';\n\nconst newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');\nconsole.log(newBuf.toString('ascii'));\n// Prints: '?'\n
\nconst { Buffer, transcode } = require('node:buffer');\n\nconst newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');\nconsole.log(newBuf.toString('ascii'));\n// Prints: '?'\n
\nBecause the Euro (€
) sign is not representable in US-ASCII, it is replaced\nwith ?
in the transcoded Buffer
.
Returns the maximum number of bytes that will be returned when\nbuf.inspect()
is called. This can be overridden by user modules. See\nutil.inspect()
for more details on buf.inspect()
behavior.
An alias for buffer.constants.MAX_LENGTH
.
An alias for buffer.constants.MAX_STRING_LENGTH
.
See Buffer.allocUnsafeSlow()
. This was never a class in the sense that\nthe constructor always returned a Buffer
instance, rather than a SlowBuffer
\ninstance.
On 32-bit architectures, this value currently is 230 - 1 (about 1\nGiB).
\nOn 64-bit architectures, this value currently is 232 (about 4 GiB).
\nIt reflects v8::TypedArray::kMaxLength
under the hood.
This value is also available as buffer.kMaxLength
.
Represents the largest length
that a string
primitive can have, counted\nin UTF-16 code units.
This value may depend on the JS engine that is being used.
", "shortDesc": "The largest length allowed for a single `string` instance." } ], "type": "module", "displayName": "Buffer constants" } ], "type": "module", "displayName": "`node:buffer` module APIs" }, { "textRaw": "`Buffer.from()`, `Buffer.alloc()`, and `Buffer.allocUnsafe()`", "name": "`buffer.from()`,_`buffer.alloc()`,_and_`buffer.allocunsafe()`", "desc": "In versions of Node.js prior to 6.0.0, Buffer
instances were created using the\nBuffer
constructor function, which allocates the returned Buffer
\ndifferently based on what arguments are provided:
Buffer()
(e.g. new Buffer(10)
)\nallocates a new Buffer
object of the specified size. Prior to Node.js 8.0.0,\nthe memory allocated for such Buffer
instances is not initialized and\ncan contain sensitive data. Such Buffer
instances must be subsequently\ninitialized by using either buf.fill(0)
or by writing to the\nentire Buffer
before reading data from the Buffer
.\nWhile this behavior is intentional to improve performance,\ndevelopment experience has demonstrated that a more explicit distinction is\nrequired between creating a fast-but-uninitialized Buffer
versus creating a\nslower-but-safer Buffer
. Since Node.js 8.0.0, Buffer(num)
and new Buffer(num)
return a Buffer
with initialized memory.Buffer
as the first argument copies the\npassed object's data into the Buffer
.ArrayBuffer
or a SharedArrayBuffer
returns a Buffer
\nthat shares allocated memory with the given array buffer.Because the behavior of new Buffer()
is different depending on the type of the\nfirst argument, security and reliability issues can be inadvertently introduced\ninto applications when argument validation or Buffer
initialization is not\nperformed.
For example, if an attacker can cause an application to receive a number where\na string is expected, the application may call new Buffer(100)
\ninstead of new Buffer(\"100\")
, leading it to allocate a 100 byte buffer instead\nof allocating a 3 byte buffer with content \"100\"
. This is commonly possible\nusing JSON API calls. Since JSON distinguishes between numeric and string types,\nit allows injection of numbers where a naively written application that does not\nvalidate its input sufficiently might expect to always receive a string.\nBefore Node.js 8.0.0, the 100 byte buffer might contain\narbitrary pre-existing in-memory data, so may be used to expose in-memory\nsecrets to a remote attacker. Since Node.js 8.0.0, exposure of memory cannot\noccur because the data is zero-filled. However, other attacks are still\npossible, such as causing very large buffers to be allocated by the server,\nleading to performance degradation or crashing on memory exhaustion.
To make the creation of Buffer
instances more reliable and less error-prone,\nthe various forms of the new Buffer()
constructor have been deprecated\nand replaced by separate Buffer.from()
, Buffer.alloc()
, and\nBuffer.allocUnsafe()
methods.
Developers should migrate all existing uses of the new Buffer()
constructors\nto one of these new APIs.
Buffer.from(array)
returns a new Buffer
that contains a copy of the\nprovided octets.Buffer.from(arrayBuffer[, byteOffset[, length]])
\nreturns a new Buffer
that shares the same allocated memory as the given\nArrayBuffer
.Buffer.from(buffer)
returns a new Buffer
that contains a copy of the\ncontents of the given Buffer
.Buffer.from(string[, encoding])
returns a new\nBuffer
that contains a copy of the provided string.Buffer.alloc(size[, fill[, encoding]])
returns a new\ninitialized Buffer
of the specified size. This method is slower than\nBuffer.allocUnsafe(size)
but guarantees that newly\ncreated Buffer
instances never contain old data that is potentially\nsensitive. A TypeError
will be thrown if size
is not a number.Buffer.allocUnsafe(size)
and\nBuffer.allocUnsafeSlow(size)
each return a\nnew uninitialized Buffer
of the specified size
. Because the Buffer
is\nuninitialized, the allocated segment of memory might contain old data that is\npotentially sensitive.Buffer
instances returned by Buffer.allocUnsafe()
and\nBuffer.from(array)
may be allocated off a shared internal memory pool\nif size
is less than or equal to half Buffer.poolSize
. Instances\nreturned by Buffer.allocUnsafeSlow()
never use the shared internal\nmemory pool.
Node.js can be started using the --zero-fill-buffers
command-line option to\ncause all newly-allocated Buffer
instances to be zero-filled upon creation by\ndefault. Without the option, buffers created with Buffer.allocUnsafe()
,\nBuffer.allocUnsafeSlow()
, and new SlowBuffer(size)
are not zero-filled.\nUse of this flag can have a measurable negative impact on performance. Use the\n--zero-fill-buffers
option only when necessary to enforce that newly allocated\nBuffer
instances cannot contain old data that is potentially sensitive.
$ node --zero-fill-buffers\n> Buffer.allocUnsafe(5);\n<Buffer 00 00 00 00 00>\n
",
"type": "module",
"displayName": "The `--zero-fill-buffers` command-line option"
},
{
"textRaw": "What makes `Buffer.allocUnsafe()` and `Buffer.allocUnsafeSlow()` \"unsafe\"?",
"name": "what_makes_`buffer.allocunsafe()`_and_`buffer.allocunsafeslow()`_\"unsafe\"?",
"desc": "When calling Buffer.allocUnsafe()
and Buffer.allocUnsafeSlow()
, the\nsegment of allocated memory is uninitialized (it is not zeroed-out). While\nthis design makes the allocation of memory quite fast, the allocated segment of\nmemory might contain old data that is potentially sensitive. Using a Buffer
\ncreated by Buffer.allocUnsafe()
without completely overwriting the\nmemory can allow this old data to be leaked when the Buffer
memory is read.
While there are clear performance advantages to using\nBuffer.allocUnsafe()
, extra care must be taken in order to avoid\nintroducing security vulnerabilities into an application.
A Blob
encapsulates immutable, raw data that can be safely shared across\nmultiple worker threads.
Returns a promise that fulfills with an <ArrayBuffer> containing a copy of\nthe Blob
data.
Creates and returns a new Blob
containing a subset of this Blob
objects\ndata. The original Blob
is not altered.
Returns a new ReadableStream
that allows the content of the Blob
to be read.
Returns a promise that fulfills with the contents of the Blob
decoded as a\nUTF-8 string.
The total size of the Blob
in bytes.
The content-type of the Blob
.
Once a <Blob> object is created, it can be sent via MessagePort
to multiple\ndestinations without transferring or immediately copying the data. The data\ncontained by the Blob
is copied only when the arrayBuffer()
or text()
\nmethods are called.
import { Blob } from 'node:buffer';\nimport { setTimeout as delay } from 'node:timers/promises';\n\nconst blob = new Blob(['hello there']);\n\nconst mc1 = new MessageChannel();\nconst mc2 = new MessageChannel();\n\nmc1.port1.onmessage = async ({ data }) => {\n console.log(await data.arrayBuffer());\n mc1.port1.close();\n};\n\nmc2.port1.onmessage = async ({ data }) => {\n await delay(1000);\n console.log(await data.arrayBuffer());\n mc2.port1.close();\n};\n\nmc1.port2.postMessage(blob);\nmc2.port2.postMessage(blob);\n\n// The Blob is still usable after posting.\nblob.text().then(console.log);\n
\nconst { Blob } = require('node:buffer');\nconst { setTimeout: delay } = require('node:timers/promises');\n\nconst blob = new Blob(['hello there']);\n\nconst mc1 = new MessageChannel();\nconst mc2 = new MessageChannel();\n\nmc1.port1.onmessage = async ({ data }) => {\n console.log(await data.arrayBuffer());\n mc1.port1.close();\n};\n\nmc2.port1.onmessage = async ({ data }) => {\n await delay(1000);\n console.log(await data.arrayBuffer());\n mc2.port1.close();\n};\n\nmc1.port2.postMessage(blob);\nmc2.port2.postMessage(blob);\n\n// The Blob is still usable after posting.\nblob.text().then(console.log);\n
",
"type": "module",
"displayName": "`Blob` objects and `MessageChannel`"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`sources` {string\\[]|ArrayBuffer\\[]|TypedArray\\[]|DataView\\[]|Blob\\[]} An array of string, {ArrayBuffer}, {TypedArray}, {DataView}, or {Blob} objects, or any mix of such objects, that will be stored within the `Blob`.",
"name": "sources",
"type": "string\\[]|ArrayBuffer\\[]|TypedArray\\[]|DataView\\[]|Blob\\[]",
"desc": "An array of string, {ArrayBuffer}, {TypedArray}, {DataView}, or {Blob} objects, or any mix of such objects, that will be stored within the `Blob`."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`endings` {string} One of either `'transparent'` or `'native'`. When set to `'native'`, line endings in string source parts will be converted to the platform native line-ending as specified by `require('node:os').EOL`.",
"name": "endings",
"type": "string",
"desc": "One of either `'transparent'` or `'native'`. When set to `'native'`, line endings in string source parts will be converted to the platform native line-ending as specified by `require('node:os').EOL`."
},
{
"textRaw": "`type` {string} The Blob content-type. The intent is for `type` to convey the MIME media type of the data, however no validation of the type format is performed.",
"name": "type",
"type": "string",
"desc": "The Blob content-type. The intent is for `type` to convey the MIME media type of the data, however no validation of the type format is performed."
}
]
}
],
"desc": "Creates a new Blob
object containing a concatenation of the given sources.
<ArrayBuffer>, <TypedArray>, <DataView>, and <Buffer> sources are copied into\nthe 'Blob' and can therefore be safely modified after the 'Blob' is created.
\nString sources are encoded as UTF-8 byte sequences and copied into the Blob.\nUnmatched surrogate pairs within each string part will be replaced by Unicode\nU+FFFD replacement characters.
" } ] }, { "textRaw": "Class: `Buffer`", "type": "class", "name": "Buffer", "desc": "The Buffer
class is a global type for dealing with binary data directly.\nIt can be constructed in a variety of ways.
Allocates a new Buffer
of size
bytes. If fill
is undefined
, the\nBuffer
will be zero-filled.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.alloc(5);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.alloc(5);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00>\n
\nIf size
is larger than\nbuffer.constants.MAX_LENGTH
or smaller than 0, ERR_OUT_OF_RANGE
\nis thrown.
If fill
is specified, the allocated Buffer
will be initialized by calling\nbuf.fill(fill)
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.alloc(5, 'a');\n\nconsole.log(buf);\n// Prints: <Buffer 61 61 61 61 61>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.alloc(5, 'a');\n\nconsole.log(buf);\n// Prints: <Buffer 61 61 61 61 61>\n
\nIf both fill
and encoding
are specified, the allocated Buffer
will be\ninitialized by calling buf.fill(fill, encoding)
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');\n\nconsole.log(buf);\n// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');\n\nconsole.log(buf);\n// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>\n
\nCalling Buffer.alloc()
can be measurably slower than the alternative\nBuffer.allocUnsafe()
but ensures that the newly created Buffer
instance\ncontents will never contain sensitive data from previous allocations, including\ndata that might not have been allocated for Buffer
s.
A TypeError
will be thrown if size
is not a number.
Allocates a new Buffer
of size
bytes. If size
is larger than\nbuffer.constants.MAX_LENGTH
or smaller than 0, ERR_OUT_OF_RANGE
\nis thrown.
The underlying memory for Buffer
instances created in this way is not\ninitialized. The contents of the newly created Buffer
are unknown and\nmay contain sensitive data. Use Buffer.alloc()
instead to initialize\nBuffer
instances with zeroes.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(10);\n\nconsole.log(buf);\n// Prints (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>\n\nbuf.fill(0);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(10);\n\nconsole.log(buf);\n// Prints (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>\n\nbuf.fill(0);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>\n
\nA TypeError
will be thrown if size
is not a number.
The Buffer
module pre-allocates an internal Buffer
instance of\nsize Buffer.poolSize
that is used as a pool for the fast allocation of new\nBuffer
instances created using Buffer.allocUnsafe()
, Buffer.from(array)
,\nand Buffer.concat()
only when size
is less than\nBuffer.poolSize >>> 1
(floor of Buffer.poolSize
divided by two).
Use of this pre-allocated internal memory pool is a key difference between\ncalling Buffer.alloc(size, fill)
vs. Buffer.allocUnsafe(size).fill(fill)
.\nSpecifically, Buffer.alloc(size, fill)
will never use the internal Buffer
\npool, while Buffer.allocUnsafe(size).fill(fill)
will use the internal\nBuffer
pool if size
is less than or equal to half Buffer.poolSize
. The\ndifference is subtle but can be important when an application requires the\nadditional performance that Buffer.allocUnsafe()
provides.
Allocates a new Buffer
of size
bytes. If size
is larger than\nbuffer.constants.MAX_LENGTH
or smaller than 0, ERR_OUT_OF_RANGE
\nis thrown. A zero-length Buffer
is created if size
is 0.
The underlying memory for Buffer
instances created in this way is not\ninitialized. The contents of the newly created Buffer
are unknown and\nmay contain sensitive data. Use buf.fill(0)
to initialize\nsuch Buffer
instances with zeroes.
When using Buffer.allocUnsafe()
to allocate new Buffer
instances,\nallocations under 4 KiB are sliced from a single pre-allocated Buffer
. This\nallows applications to avoid the garbage collection overhead of creating many\nindividually allocated Buffer
instances. This approach improves both\nperformance and memory usage by eliminating the need to track and clean up as\nmany individual ArrayBuffer
objects.
However, in the case where a developer may need to retain a small chunk of\nmemory from a pool for an indeterminate amount of time, it may be appropriate\nto create an un-pooled Buffer
instance using Buffer.allocUnsafeSlow()
and\nthen copying out the relevant bits.
import { Buffer } from 'node:buffer';\n\n// Need to keep around a few small chunks of memory.\nconst store = [];\n\nsocket.on('readable', () => {\n let data;\n while (null !== (data = readable.read())) {\n // Allocate for retained data.\n const sb = Buffer.allocUnsafeSlow(10);\n\n // Copy the data into the new allocation.\n data.copy(sb, 0, 0, 10);\n\n store.push(sb);\n }\n});\n
\nconst { Buffer } = require('node:buffer');\n\n// Need to keep around a few small chunks of memory.\nconst store = [];\n\nsocket.on('readable', () => {\n let data;\n while (null !== (data = readable.read())) {\n // Allocate for retained data.\n const sb = Buffer.allocUnsafeSlow(10);\n\n // Copy the data into the new allocation.\n data.copy(sb, 0, 0, 10);\n\n store.push(sb);\n }\n});\n
\nA TypeError
will be thrown if size
is not a number.
Returns the byte length of a string when encoded using encoding
.\nThis is not the same as String.prototype.length
, which does not account\nfor the encoding that is used to convert the string into bytes.
For 'base64'
, 'base64url'
, and 'hex'
, this function assumes valid input.\nFor strings that contain non-base64/hex-encoded data (e.g. whitespace), the\nreturn value might be greater than the length of a Buffer
created from the\nstring.
import { Buffer } from 'node:buffer';\n\nconst str = '\\u00bd + \\u00bc = \\u00be';\n\nconsole.log(`${str}: ${str.length} characters, ` +\n `${Buffer.byteLength(str, 'utf8')} bytes`);\n// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes\n
\nconst { Buffer } = require('node:buffer');\n\nconst str = '\\u00bd + \\u00bc = \\u00be';\n\nconsole.log(`${str}: ${str.length} characters, ` +\n `${Buffer.byteLength(str, 'utf8')} bytes`);\n// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes\n
\nWhen string
is a Buffer
/DataView
/TypedArray
/ArrayBuffer
/\nSharedArrayBuffer
, the byte length as reported by .byteLength
\nis returned.
Compares buf1
to buf2
, typically for the purpose of sorting arrays of\nBuffer
instances. This is equivalent to calling\nbuf1.compare(buf2)
.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from('1234');\nconst buf2 = Buffer.from('0123');\nconst arr = [buf1, buf2];\n\nconsole.log(arr.sort(Buffer.compare));\n// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]\n// (This result is equal to: [buf2, buf1].)\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from('1234');\nconst buf2 = Buffer.from('0123');\nconst arr = [buf1, buf2];\n\nconsole.log(arr.sort(Buffer.compare));\n// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]\n// (This result is equal to: [buf2, buf1].)\n
"
},
{
"textRaw": "Static method: `Buffer.concat(list[, totalLength])`",
"type": "classMethod",
"name": "concat",
"meta": {
"added": [
"v0.7.11"
],
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/10236",
"description": "The elements of `list` can now be `Uint8Array`s."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer}",
"name": "return",
"type": "Buffer"
},
"params": [
{
"textRaw": "`list` {Buffer\\[] | Uint8Array\\[]} List of `Buffer` or [`Uint8Array`][] instances to concatenate.",
"name": "list",
"type": "Buffer\\[] | Uint8Array\\[]",
"desc": "List of `Buffer` or [`Uint8Array`][] instances to concatenate."
},
{
"textRaw": "`totalLength` {integer} Total length of the `Buffer` instances in `list` when concatenated.",
"name": "totalLength",
"type": "integer",
"desc": "Total length of the `Buffer` instances in `list` when concatenated."
}
]
}
],
"desc": "Returns a new Buffer
which is the result of concatenating all the Buffer
\ninstances in the list
together.
If the list has no items, or if the totalLength
is 0, then a new zero-length\nBuffer
is returned.
If totalLength
is not provided, it is calculated from the Buffer
instances\nin list
by adding their lengths.
If totalLength
is provided, it is coerced to an unsigned integer. If the\ncombined length of the Buffer
s in list
exceeds totalLength
, the result is\ntruncated to totalLength
.
import { Buffer } from 'node:buffer';\n\n// Create a single `Buffer` from a list of three `Buffer` instances.\n\nconst buf1 = Buffer.alloc(10);\nconst buf2 = Buffer.alloc(14);\nconst buf3 = Buffer.alloc(18);\nconst totalLength = buf1.length + buf2.length + buf3.length;\n\nconsole.log(totalLength);\n// Prints: 42\n\nconst bufA = Buffer.concat([buf1, buf2, buf3], totalLength);\n\nconsole.log(bufA);\n// Prints: <Buffer 00 00 00 00 ...>\nconsole.log(bufA.length);\n// Prints: 42\n
\nconst { Buffer } = require('node:buffer');\n\n// Create a single `Buffer` from a list of three `Buffer` instances.\n\nconst buf1 = Buffer.alloc(10);\nconst buf2 = Buffer.alloc(14);\nconst buf3 = Buffer.alloc(18);\nconst totalLength = buf1.length + buf2.length + buf3.length;\n\nconsole.log(totalLength);\n// Prints: 42\n\nconst bufA = Buffer.concat([buf1, buf2, buf3], totalLength);\n\nconsole.log(bufA);\n// Prints: <Buffer 00 00 00 00 ...>\nconsole.log(bufA.length);\n// Prints: 42\n
\nBuffer.concat()
may also use the internal Buffer
pool like\nBuffer.allocUnsafe()
does.
Copies the underlying memory of view
into a new Buffer
.
const u16 = new Uint16Array([0, 0xffff]);\nconst buf = Buffer.copyBytesFrom(u16, 1, 1);\nu16[1] = 0;\nconsole.log(buf.length); // 2\nconsole.log(buf[0]); // 255\nconsole.log(buf[1]); // 255\n
"
},
{
"textRaw": "Static method: `Buffer.from(array)`",
"type": "classMethod",
"name": "from",
"meta": {
"added": [
"v5.10.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`array` {integer\\[]}",
"name": "array",
"type": "integer\\[]"
}
]
}
],
"desc": "Allocates a new Buffer
using an array
of bytes in the range 0
– 255
.\nArray entries outside that range will be truncated to fit into it.
import { Buffer } from 'node:buffer';\n\n// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'.\nconst buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);\n
\nconst { Buffer } = require('node:buffer');\n\n// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'.\nconst buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);\n
\nIf array
is an Array
-like object (that is, one with a length
property of\ntype number
), it is treated as if it is an array, unless it is a Buffer
or\na Uint8Array
. This means all other TypedArray
variants get treated as an\nArray
. To create a Buffer
from the bytes backing a TypedArray
, use\nBuffer.copyBytesFrom()
.
A TypeError
will be thrown if array
is not an Array
or another type\nappropriate for Buffer.from()
variants.
Buffer.from(array)
and Buffer.from(string)
may also use the internal\nBuffer
pool like Buffer.allocUnsafe()
does.
This creates a view of the ArrayBuffer
without copying the underlying\nmemory. For example, when passed a reference to the .buffer
property of a\nTypedArray
instance, the newly created Buffer
will share the same\nallocated memory as the TypedArray
's underlying ArrayBuffer
.
import { Buffer } from 'node:buffer';\n\nconst arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Shares memory with `arr`.\nconst buf = Buffer.from(arr.buffer);\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 a0 0f>\n\n// Changing the original Uint16Array changes the Buffer also.\narr[1] = 6000;\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 70 17>\n
\nconst { Buffer } = require('node:buffer');\n\nconst arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Shares memory with `arr`.\nconst buf = Buffer.from(arr.buffer);\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 a0 0f>\n\n// Changing the original Uint16Array changes the Buffer also.\narr[1] = 6000;\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 70 17>\n
\nThe optional byteOffset
and length
arguments specify a memory range within\nthe arrayBuffer
that will be shared by the Buffer
.
import { Buffer } from 'node:buffer';\n\nconst ab = new ArrayBuffer(10);\nconst buf = Buffer.from(ab, 0, 2);\n\nconsole.log(buf.length);\n// Prints: 2\n
\nconst { Buffer } = require('node:buffer');\n\nconst ab = new ArrayBuffer(10);\nconst buf = Buffer.from(ab, 0, 2);\n\nconsole.log(buf.length);\n// Prints: 2\n
\nA TypeError
will be thrown if arrayBuffer
is not an ArrayBuffer
or a\nSharedArrayBuffer
or another type appropriate for Buffer.from()
\nvariants.
It is important to remember that a backing ArrayBuffer
can cover a range\nof memory that extends beyond the bounds of a TypedArray
view. A new\nBuffer
created using the buffer
property of a TypedArray
may extend\nbeyond the range of the TypedArray
:
import { Buffer } from 'node:buffer';\n\nconst arrA = Uint8Array.from([0x63, 0x64, 0x65, 0x66]); // 4 elements\nconst arrB = new Uint8Array(arrA.buffer, 1, 2); // 2 elements\nconsole.log(arrA.buffer === arrB.buffer); // true\n\nconst buf = Buffer.from(arrB.buffer);\nconsole.log(buf);\n// Prints: <Buffer 63 64 65 66>\n
\nconst { Buffer } = require('node:buffer');\n\nconst arrA = Uint8Array.from([0x63, 0x64, 0x65, 0x66]); // 4 elements\nconst arrB = new Uint8Array(arrA.buffer, 1, 2); // 2 elements\nconsole.log(arrA.buffer === arrB.buffer); // true\n\nconst buf = Buffer.from(arrB.buffer);\nconsole.log(buf);\n// Prints: <Buffer 63 64 65 66>\n
"
},
{
"textRaw": "Static method: `Buffer.from(buffer)`",
"type": "classMethod",
"name": "from",
"meta": {
"added": [
"v5.10.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`buffer` {Buffer|Uint8Array} An existing `Buffer` or [`Uint8Array`][] from which to copy data.",
"name": "buffer",
"type": "Buffer|Uint8Array",
"desc": "An existing `Buffer` or [`Uint8Array`][] from which to copy data."
}
]
}
],
"desc": "Copies the passed buffer
data onto a new Buffer
instance.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from('buffer');\nconst buf2 = Buffer.from(buf1);\n\nbuf1[0] = 0x61;\n\nconsole.log(buf1.toString());\n// Prints: auffer\nconsole.log(buf2.toString());\n// Prints: buffer\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from('buffer');\nconst buf2 = Buffer.from(buf1);\n\nbuf1[0] = 0x61;\n\nconsole.log(buf1.toString());\n// Prints: auffer\nconsole.log(buf2.toString());\n// Prints: buffer\n
\nA TypeError
will be thrown if buffer
is not a Buffer
or another type\nappropriate for Buffer.from()
variants.
For objects whose valueOf()
function returns a value not strictly equal to\nobject
, returns Buffer.from(object.valueOf(), offsetOrEncoding, length)
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from(new String('this is a test'));\n// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from(new String('this is a test'));\n// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>\n
\nFor objects that support Symbol.toPrimitive
, returns\nBuffer.from(object[Symbol.toPrimitive]('string'), offsetOrEncoding)
.
import { Buffer } from 'node:buffer';\n\nclass Foo {\n [Symbol.toPrimitive]() {\n return 'this is a test';\n }\n}\n\nconst buf = Buffer.from(new Foo(), 'utf8');\n// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>\n
\nconst { Buffer } = require('node:buffer');\n\nclass Foo {\n [Symbol.toPrimitive]() {\n return 'this is a test';\n }\n}\n\nconst buf = Buffer.from(new Foo(), 'utf8');\n// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>\n
\nA TypeError
will be thrown if object
does not have the mentioned methods or\nis not of another type appropriate for Buffer.from()
variants.
Creates a new Buffer
containing string
. The encoding
parameter identifies\nthe character encoding to be used when converting string
into bytes.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from('this is a tést');\nconst buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');\n\nconsole.log(buf1.toString());\n// Prints: this is a tést\nconsole.log(buf2.toString());\n// Prints: this is a tést\nconsole.log(buf1.toString('latin1'));\n// Prints: this is a tést\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from('this is a tést');\nconst buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');\n\nconsole.log(buf1.toString());\n// Prints: this is a tést\nconsole.log(buf2.toString());\n// Prints: this is a tést\nconsole.log(buf1.toString('latin1'));\n// Prints: this is a tést\n
\nA TypeError
will be thrown if string
is not a string or another type\nappropriate for Buffer.from()
variants.
Returns true
if obj
is a Buffer
, false
otherwise.
import { Buffer } from 'node:buffer';\n\nBuffer.isBuffer(Buffer.alloc(10)); // true\nBuffer.isBuffer(Buffer.from('foo')); // true\nBuffer.isBuffer('a string'); // false\nBuffer.isBuffer([]); // false\nBuffer.isBuffer(new Uint8Array(1024)); // false\n
\nconst { Buffer } = require('node:buffer');\n\nBuffer.isBuffer(Buffer.alloc(10)); // true\nBuffer.isBuffer(Buffer.from('foo')); // true\nBuffer.isBuffer('a string'); // false\nBuffer.isBuffer([]); // false\nBuffer.isBuffer(new Uint8Array(1024)); // false\n
"
},
{
"textRaw": "Static method: `Buffer.isEncoding(encoding)`",
"type": "classMethod",
"name": "isEncoding",
"meta": {
"added": [
"v0.9.1"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`encoding` {string} A character encoding name to check.",
"name": "encoding",
"type": "string",
"desc": "A character encoding name to check."
}
]
}
],
"desc": "Returns true
if encoding
is the name of a supported character encoding,\nor false
otherwise.
import { Buffer } from 'node:buffer';\n\nconsole.log(Buffer.isEncoding('utf8'));\n// Prints: true\n\nconsole.log(Buffer.isEncoding('hex'));\n// Prints: true\n\nconsole.log(Buffer.isEncoding('utf/8'));\n// Prints: false\n\nconsole.log(Buffer.isEncoding(''));\n// Prints: false\n
\nconst { Buffer } = require('node:buffer');\n\nconsole.log(Buffer.isEncoding('utf8'));\n// Prints: true\n\nconsole.log(Buffer.isEncoding('hex'));\n// Prints: true\n\nconsole.log(Buffer.isEncoding('utf/8'));\n// Prints: false\n\nconsole.log(Buffer.isEncoding(''));\n// Prints: false\n
"
}
],
"properties": [
{
"textRaw": "`poolSize` {integer} **Default:** `8192`",
"type": "integer",
"name": "poolSize",
"meta": {
"added": [
"v0.11.3"
],
"changes": []
},
"default": "`8192`",
"desc": "This is the size (in bytes) of pre-allocated internal Buffer
instances used\nfor pooling. This value may be modified.
The index operator [index]
can be used to get and set the octet at position\nindex
in buf
. The values refer to individual bytes, so the legal value\nrange is between 0x00
and 0xFF
(hex) or 0
and 255
(decimal).
This operator is inherited from Uint8Array
, so its behavior on out-of-bounds\naccess is the same as Uint8Array
. In other words, buf[index]
returns\nundefined
when index
is negative or greater or equal to buf.length
, and\nbuf[index] = value
does not modify the buffer if index
is negative or\n>= buf.length
.
import { Buffer } from 'node:buffer';\n\n// Copy an ASCII string into a `Buffer` one byte at a time.\n// (This only works for ASCII-only strings. In general, one should use\n// `Buffer.from()` to perform this conversion.)\n\nconst str = 'Node.js';\nconst buf = Buffer.allocUnsafe(str.length);\n\nfor (let i = 0; i < str.length; i++) {\n buf[i] = str.charCodeAt(i);\n}\n\nconsole.log(buf.toString('utf8'));\n// Prints: Node.js\n
\nconst { Buffer } = require('node:buffer');\n\n// Copy an ASCII string into a `Buffer` one byte at a time.\n// (This only works for ASCII-only strings. In general, one should use\n// `Buffer.from()` to perform this conversion.)\n\nconst str = 'Node.js';\nconst buf = Buffer.allocUnsafe(str.length);\n\nfor (let i = 0; i < str.length; i++) {\n buf[i] = str.charCodeAt(i);\n}\n\nconsole.log(buf.toString('utf8'));\n// Prints: Node.js\n
"
},
{
"textRaw": "`buffer` {ArrayBuffer} The underlying `ArrayBuffer` object based on which this `Buffer` object is created.",
"type": "ArrayBuffer",
"name": "buffer",
"desc": "This ArrayBuffer
is not guaranteed to correspond exactly to the original\nBuffer
. See the notes on buf.byteOffset
for details.
import { Buffer } from 'node:buffer';\n\nconst arrayBuffer = new ArrayBuffer(16);\nconst buffer = Buffer.from(arrayBuffer);\n\nconsole.log(buffer.buffer === arrayBuffer);\n// Prints: true\n
\nconst { Buffer } = require('node:buffer');\n\nconst arrayBuffer = new ArrayBuffer(16);\nconst buffer = Buffer.from(arrayBuffer);\n\nconsole.log(buffer.buffer === arrayBuffer);\n// Prints: true\n
",
"shortDesc": "The underlying `ArrayBuffer` object based on which this `Buffer` object is created."
},
{
"textRaw": "`byteOffset` {integer} The `byteOffset` of the `Buffer`s underlying `ArrayBuffer` object.",
"type": "integer",
"name": "byteOffset",
"desc": "When setting byteOffset
in Buffer.from(ArrayBuffer, byteOffset, length)
,\nor sometimes when allocating a Buffer
smaller than Buffer.poolSize
, the\nbuffer does not start from a zero offset on the underlying ArrayBuffer
.
This can cause problems when accessing the underlying ArrayBuffer
directly\nusing buf.buffer
, as other parts of the ArrayBuffer
may be unrelated\nto the Buffer
object itself.
A common issue when creating a TypedArray
object that shares its memory with\na Buffer
is that in this case one needs to specify the byteOffset
correctly:
import { Buffer } from 'node:buffer';\n\n// Create a buffer smaller than `Buffer.poolSize`.\nconst nodeBuffer = Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);\n\n// When casting the Node.js Buffer to an Int8Array, use the byteOffset\n// to refer only to the part of `nodeBuffer.buffer` that contains the memory\n// for `nodeBuffer`.\nnew Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);\n
\nconst { Buffer } = require('node:buffer');\n\n// Create a buffer smaller than `Buffer.poolSize`.\nconst nodeBuffer = Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);\n\n// When casting the Node.js Buffer to an Int8Array, use the byteOffset\n// to refer only to the part of `nodeBuffer.buffer` that contains the memory\n// for `nodeBuffer`.\nnew Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);\n
",
"shortDesc": "The `byteOffset` of the `Buffer`s underlying `ArrayBuffer` object."
},
{
"textRaw": "`length` {integer}",
"type": "integer",
"name": "length",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"desc": "Returns the number of bytes in buf
.
import { Buffer } from 'node:buffer';\n\n// Create a `Buffer` and write a shorter string to it using UTF-8.\n\nconst buf = Buffer.alloc(1234);\n\nconsole.log(buf.length);\n// Prints: 1234\n\nbuf.write('some string', 0, 'utf8');\n\nconsole.log(buf.length);\n// Prints: 1234\n
\nconst { Buffer } = require('node:buffer');\n\n// Create a `Buffer` and write a shorter string to it using UTF-8.\n\nconst buf = Buffer.alloc(1234);\n\nconsole.log(buf.length);\n// Prints: 1234\n\nbuf.write('some string', 0, 'utf8');\n\nconsole.log(buf.length);\n// Prints: 1234\n
"
},
{
"textRaw": "`buf.parent`",
"name": "parent",
"meta": {
"deprecated": [
"v8.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`buf.buffer`][] instead.",
"desc": "The buf.parent
property is a deprecated alias for buf.buffer
.
Compares buf
with target
and returns a number indicating whether buf
\ncomes before, after, or is the same as target
in sort order.\nComparison is based on the actual sequence of bytes in each Buffer
.
0
is returned if target
is the same as buf
1
is returned if target
should come before buf
when sorted.-1
is returned if target
should come after buf
when sorted.import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('BCD');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.compare(buf1));\n// Prints: 0\nconsole.log(buf1.compare(buf2));\n// Prints: -1\nconsole.log(buf1.compare(buf3));\n// Prints: -1\nconsole.log(buf2.compare(buf1));\n// Prints: 1\nconsole.log(buf2.compare(buf3));\n// Prints: 1\nconsole.log([buf1, buf2, buf3].sort(Buffer.compare));\n// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]\n// (This result is equal to: [buf1, buf3, buf2].)\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('BCD');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.compare(buf1));\n// Prints: 0\nconsole.log(buf1.compare(buf2));\n// Prints: -1\nconsole.log(buf1.compare(buf3));\n// Prints: -1\nconsole.log(buf2.compare(buf1));\n// Prints: 1\nconsole.log(buf2.compare(buf3));\n// Prints: 1\nconsole.log([buf1, buf2, buf3].sort(Buffer.compare));\n// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]\n// (This result is equal to: [buf1, buf3, buf2].)\n
\nThe optional targetStart
, targetEnd
, sourceStart
, and sourceEnd
\narguments can be used to limit the comparison to specific ranges within target
\nand buf
respectively.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);\nconst buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);\n\nconsole.log(buf1.compare(buf2, 5, 9, 0, 4));\n// Prints: 0\nconsole.log(buf1.compare(buf2, 0, 6, 4));\n// Prints: -1\nconsole.log(buf1.compare(buf2, 5, 6, 5));\n// Prints: 1\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);\nconst buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);\n\nconsole.log(buf1.compare(buf2, 5, 9, 0, 4));\n// Prints: 0\nconsole.log(buf1.compare(buf2, 0, 6, 4));\n// Prints: -1\nconsole.log(buf1.compare(buf2, 5, 6, 5));\n// Prints: 1\n
\nERR_OUT_OF_RANGE
is thrown if targetStart < 0
, sourceStart < 0
,\ntargetEnd > target.byteLength
, or sourceEnd > source.byteLength
.
Copies data from a region of buf
to a region in target
, even if the target
\nmemory region overlaps with buf
.
TypedArray.prototype.set()
performs the same operation, and is available\nfor all TypedArrays, including Node.js Buffer
s, although it takes\ndifferent function arguments.
import { Buffer } from 'node:buffer';\n\n// Create two `Buffer` instances.\nconst buf1 = Buffer.allocUnsafe(26);\nconst buf2 = Buffer.allocUnsafe(26).fill('!');\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf1[i] = i + 97;\n}\n\n// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.\nbuf1.copy(buf2, 8, 16, 20);\n// This is equivalent to:\n// buf2.set(buf1.subarray(16, 20), 8);\n\nconsole.log(buf2.toString('ascii', 0, 25));\n// Prints: !!!!!!!!qrst!!!!!!!!!!!!!\n
\nconst { Buffer } = require('node:buffer');\n\n// Create two `Buffer` instances.\nconst buf1 = Buffer.allocUnsafe(26);\nconst buf2 = Buffer.allocUnsafe(26).fill('!');\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf1[i] = i + 97;\n}\n\n// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.\nbuf1.copy(buf2, 8, 16, 20);\n// This is equivalent to:\n// buf2.set(buf1.subarray(16, 20), 8);\n\nconsole.log(buf2.toString('ascii', 0, 25));\n// Prints: !!!!!!!!qrst!!!!!!!!!!!!!\n
\nimport { Buffer } from 'node:buffer';\n\n// Create a `Buffer` and copy data from one region to an overlapping region\n// within the same `Buffer`.\n\nconst buf = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf[i] = i + 97;\n}\n\nbuf.copy(buf, 0, 4, 10);\n\nconsole.log(buf.toString());\n// Prints: efghijghijklmnopqrstuvwxyz\n
\nconst { Buffer } = require('node:buffer');\n\n// Create a `Buffer` and copy data from one region to an overlapping region\n// within the same `Buffer`.\n\nconst buf = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf[i] = i + 97;\n}\n\nbuf.copy(buf, 0, 4, 10);\n\nconsole.log(buf.toString());\n// Prints: efghijghijklmnopqrstuvwxyz\n
"
},
{
"textRaw": "`buf.entries()`",
"type": "method",
"name": "entries",
"meta": {
"added": [
"v1.1.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Iterator}",
"name": "return",
"type": "Iterator"
},
"params": []
}
],
"desc": "Creates and returns an iterator of [index, byte]
pairs from the contents\nof buf
.
import { Buffer } from 'node:buffer';\n\n// Log the entire contents of a `Buffer`.\n\nconst buf = Buffer.from('buffer');\n\nfor (const pair of buf.entries()) {\n console.log(pair);\n}\n// Prints:\n// [0, 98]\n// [1, 117]\n// [2, 102]\n// [3, 102]\n// [4, 101]\n// [5, 114]\n
\nconst { Buffer } = require('node:buffer');\n\n// Log the entire contents of a `Buffer`.\n\nconst buf = Buffer.from('buffer');\n\nfor (const pair of buf.entries()) {\n console.log(pair);\n}\n// Prints:\n// [0, 98]\n// [1, 117]\n// [2, 102]\n// [3, 102]\n// [4, 101]\n// [5, 114]\n
"
},
{
"textRaw": "`buf.equals(otherBuffer)`",
"type": "method",
"name": "equals",
"meta": {
"added": [
"v0.11.13"
],
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/10236",
"description": "The arguments can now be `Uint8Array`s."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`otherBuffer` {Buffer|Uint8Array} A `Buffer` or [`Uint8Array`][] with which to compare `buf`.",
"name": "otherBuffer",
"type": "Buffer|Uint8Array",
"desc": "A `Buffer` or [`Uint8Array`][] with which to compare `buf`."
}
]
}
],
"desc": "Returns true
if both buf
and otherBuffer
have exactly the same bytes,\nfalse
otherwise. Equivalent to\nbuf.compare(otherBuffer) === 0
.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('414243', 'hex');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.equals(buf2));\n// Prints: true\nconsole.log(buf1.equals(buf3));\n// Prints: false\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('414243', 'hex');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.equals(buf2));\n// Prints: true\nconsole.log(buf1.equals(buf3));\n// Prints: false\n
"
},
{
"textRaw": "`buf.fill(value[, offset[, end]][, encoding])`",
"type": "method",
"name": "fill",
"meta": {
"added": [
"v0.5.0"
],
"changes": [
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/22969",
"description": "Throws `ERR_OUT_OF_RANGE` instead of `ERR_INDEX_OUT_OF_RANGE`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18790",
"description": "Negative `end` values throw an `ERR_INDEX_OUT_OF_RANGE` error."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18129",
"description": "Attempting to fill a non-zero length buffer with a zero length buffer triggers a thrown exception."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/17427",
"description": "Specifying an invalid string for `value` triggers a thrown exception."
},
{
"version": "v5.7.0",
"pr-url": "https://github.com/nodejs/node/pull/4935",
"description": "The `encoding` parameter is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} A reference to `buf`.",
"name": "return",
"type": "Buffer",
"desc": "A reference to `buf`."
},
"params": [
{
"textRaw": "`value` {string|Buffer|Uint8Array|integer} The value with which to fill `buf`. Empty value (string, Uint8Array, Buffer) is coerced to `0`.",
"name": "value",
"type": "string|Buffer|Uint8Array|integer",
"desc": "The value with which to fill `buf`. Empty value (string, Uint8Array, Buffer) is coerced to `0`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to fill `buf`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to fill `buf`."
},
{
"textRaw": "`end` {integer} Where to stop filling `buf` (not inclusive). **Default:** [`buf.length`][].",
"name": "end",
"type": "integer",
"default": "[`buf.length`][]",
"desc": "Where to stop filling `buf` (not inclusive)."
},
{
"textRaw": "`encoding` {string} The encoding for `value` if `value` is a string. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "The encoding for `value` if `value` is a string."
}
]
}
],
"desc": "Fills buf
with the specified value
. If the offset
and end
are not given,\nthe entire buf
will be filled:
import { Buffer } from 'node:buffer';\n\n// Fill a `Buffer` with the ASCII character 'h'.\n\nconst b = Buffer.allocUnsafe(50).fill('h');\n\nconsole.log(b.toString());\n// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh\n\n// Fill a buffer with empty string\nconst c = Buffer.allocUnsafe(5).fill('');\n\nconsole.log(c.fill(''));\n// Prints: <Buffer 00 00 00 00 00>\n
\nconst { Buffer } = require('node:buffer');\n\n// Fill a `Buffer` with the ASCII character 'h'.\n\nconst b = Buffer.allocUnsafe(50).fill('h');\n\nconsole.log(b.toString());\n// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh\n\n// Fill a buffer with empty string\nconst c = Buffer.allocUnsafe(5).fill('');\n\nconsole.log(c.fill(''));\n// Prints: <Buffer 00 00 00 00 00>\n
\nvalue
is coerced to a uint32
value if it is not a string, Buffer
, or\ninteger. If the resulting integer is greater than 255
(decimal), buf
will be\nfilled with value & 255
.
If the final write of a fill()
operation falls on a multi-byte character,\nthen only the bytes of that character that fit into buf
are written:
import { Buffer } from 'node:buffer';\n\n// Fill a `Buffer` with character that takes up two bytes in UTF-8.\n\nconsole.log(Buffer.allocUnsafe(5).fill('\\u0222'));\n// Prints: <Buffer c8 a2 c8 a2 c8>\n
\nconst { Buffer } = require('node:buffer');\n\n// Fill a `Buffer` with character that takes up two bytes in UTF-8.\n\nconsole.log(Buffer.allocUnsafe(5).fill('\\u0222'));\n// Prints: <Buffer c8 a2 c8 a2 c8>\n
\nIf value
contains invalid characters, it is truncated; if no valid\nfill data remains, an exception is thrown:
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(5);\n\nconsole.log(buf.fill('a'));\n// Prints: <Buffer 61 61 61 61 61>\nconsole.log(buf.fill('aazz', 'hex'));\n// Prints: <Buffer aa aa aa aa aa>\nconsole.log(buf.fill('zz', 'hex'));\n// Throws an exception.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(5);\n\nconsole.log(buf.fill('a'));\n// Prints: <Buffer 61 61 61 61 61>\nconsole.log(buf.fill('aazz', 'hex'));\n// Prints: <Buffer aa aa aa aa aa>\nconsole.log(buf.fill('zz', 'hex'));\n// Throws an exception.\n
"
},
{
"textRaw": "`buf.includes(value[, byteOffset][, encoding])`",
"type": "method",
"name": "includes",
"meta": {
"added": [
"v5.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if `value` was found in `buf`, `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if `value` was found in `buf`, `false` otherwise."
},
"params": [
{
"textRaw": "`value` {string|Buffer|Uint8Array|integer} What to search for.",
"name": "value",
"type": "string|Buffer|Uint8Array|integer",
"desc": "What to search for."
},
{
"textRaw": "`byteOffset` {integer} Where to begin searching in `buf`. If negative, then offset is calculated from the end of `buf`. **Default:** `0`.",
"name": "byteOffset",
"type": "integer",
"default": "`0`",
"desc": "Where to begin searching in `buf`. If negative, then offset is calculated from the end of `buf`."
},
{
"textRaw": "`encoding` {string} If `value` is a string, this is its encoding. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "If `value` is a string, this is its encoding."
}
]
}
],
"desc": "Equivalent to buf.indexOf() !== -1
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('this is a buffer');\n\nconsole.log(buf.includes('this'));\n// Prints: true\nconsole.log(buf.includes('is'));\n// Prints: true\nconsole.log(buf.includes(Buffer.from('a buffer')));\n// Prints: true\nconsole.log(buf.includes(97));\n// Prints: true (97 is the decimal ASCII value for 'a')\nconsole.log(buf.includes(Buffer.from('a buffer example')));\n// Prints: false\nconsole.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));\n// Prints: true\nconsole.log(buf.includes('this', 4));\n// Prints: false\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('this is a buffer');\n\nconsole.log(buf.includes('this'));\n// Prints: true\nconsole.log(buf.includes('is'));\n// Prints: true\nconsole.log(buf.includes(Buffer.from('a buffer')));\n// Prints: true\nconsole.log(buf.includes(97));\n// Prints: true (97 is the decimal ASCII value for 'a')\nconsole.log(buf.includes(Buffer.from('a buffer example')));\n// Prints: false\nconsole.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));\n// Prints: true\nconsole.log(buf.includes('this', 4));\n// Prints: false\n
"
},
{
"textRaw": "`buf.indexOf(value[, byteOffset][, encoding])`",
"type": "method",
"name": "indexOf",
"meta": {
"added": [
"v1.5.0"
],
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/10236",
"description": "The `value` can now be a `Uint8Array`."
},
{
"version": [
"v5.7.0",
"v4.4.0"
],
"pr-url": "https://github.com/nodejs/node/pull/4803",
"description": "When `encoding` is being passed, the `byteOffset` parameter is no longer required."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} The index of the first occurrence of `value` in `buf`, or `-1` if `buf` does not contain `value`.",
"name": "return",
"type": "integer",
"desc": "The index of the first occurrence of `value` in `buf`, or `-1` if `buf` does not contain `value`."
},
"params": [
{
"textRaw": "`value` {string|Buffer|Uint8Array|integer} What to search for.",
"name": "value",
"type": "string|Buffer|Uint8Array|integer",
"desc": "What to search for."
},
{
"textRaw": "`byteOffset` {integer} Where to begin searching in `buf`. If negative, then offset is calculated from the end of `buf`. **Default:** `0`.",
"name": "byteOffset",
"type": "integer",
"default": "`0`",
"desc": "Where to begin searching in `buf`. If negative, then offset is calculated from the end of `buf`."
},
{
"textRaw": "`encoding` {string} If `value` is a string, this is the encoding used to determine the binary representation of the string that will be searched for in `buf`. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "If `value` is a string, this is the encoding used to determine the binary representation of the string that will be searched for in `buf`."
}
]
}
],
"desc": "If value
is:
value
is interpreted according to the character encoding in\nencoding
.Buffer
or Uint8Array
, value
will be used in its entirety.\nTo compare a partial Buffer
, use buf.subarray
.value
will be interpreted as an unsigned 8-bit integer\nvalue between 0
and 255
.import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('this is a buffer');\n\nconsole.log(buf.indexOf('this'));\n// Prints: 0\nconsole.log(buf.indexOf('is'));\n// Prints: 2\nconsole.log(buf.indexOf(Buffer.from('a buffer')));\n// Prints: 8\nconsole.log(buf.indexOf(97));\n// Prints: 8 (97 is the decimal ASCII value for 'a')\nconsole.log(buf.indexOf(Buffer.from('a buffer example')));\n// Prints: -1\nconsole.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));\n// Prints: 8\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'utf16le');\n\nconsole.log(utf16Buffer.indexOf('\\u03a3', 0, 'utf16le'));\n// Prints: 4\nconsole.log(utf16Buffer.indexOf('\\u03a3', -4, 'utf16le'));\n// Prints: 6\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('this is a buffer');\n\nconsole.log(buf.indexOf('this'));\n// Prints: 0\nconsole.log(buf.indexOf('is'));\n// Prints: 2\nconsole.log(buf.indexOf(Buffer.from('a buffer')));\n// Prints: 8\nconsole.log(buf.indexOf(97));\n// Prints: 8 (97 is the decimal ASCII value for 'a')\nconsole.log(buf.indexOf(Buffer.from('a buffer example')));\n// Prints: -1\nconsole.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));\n// Prints: 8\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'utf16le');\n\nconsole.log(utf16Buffer.indexOf('\\u03a3', 0, 'utf16le'));\n// Prints: 4\nconsole.log(utf16Buffer.indexOf('\\u03a3', -4, 'utf16le'));\n// Prints: 6\n
\nIf value
is not a string, number, or Buffer
, this method will throw a\nTypeError
. If value
is a number, it will be coerced to a valid byte value,\nan integer between 0 and 255.
If byteOffset
is not a number, it will be coerced to a number. If the result\nof coercion is NaN
or 0
, then the entire buffer will be searched. This\nbehavior matches String.prototype.indexOf()
.
import { Buffer } from 'node:buffer';\n\nconst b = Buffer.from('abcdef');\n\n// Passing a value that's a number, but not a valid byte.\n// Prints: 2, equivalent to searching for 99 or 'c'.\nconsole.log(b.indexOf(99.9));\nconsole.log(b.indexOf(256 + 99));\n\n// Passing a byteOffset that coerces to NaN or 0.\n// Prints: 1, searching the whole buffer.\nconsole.log(b.indexOf('b', undefined));\nconsole.log(b.indexOf('b', {}));\nconsole.log(b.indexOf('b', null));\nconsole.log(b.indexOf('b', []));\n
\nconst { Buffer } = require('node:buffer');\n\nconst b = Buffer.from('abcdef');\n\n// Passing a value that's a number, but not a valid byte.\n// Prints: 2, equivalent to searching for 99 or 'c'.\nconsole.log(b.indexOf(99.9));\nconsole.log(b.indexOf(256 + 99));\n\n// Passing a byteOffset that coerces to NaN or 0.\n// Prints: 1, searching the whole buffer.\nconsole.log(b.indexOf('b', undefined));\nconsole.log(b.indexOf('b', {}));\nconsole.log(b.indexOf('b', null));\nconsole.log(b.indexOf('b', []));\n
\nIf value
is an empty string or empty Buffer
and byteOffset
is less\nthan buf.length
, byteOffset
will be returned. If value
is empty and\nbyteOffset
is at least buf.length
, buf.length
will be returned.
Creates and returns an iterator of buf
keys (indices).
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('buffer');\n\nfor (const key of buf.keys()) {\n console.log(key);\n}\n// Prints:\n// 0\n// 1\n// 2\n// 3\n// 4\n// 5\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('buffer');\n\nfor (const key of buf.keys()) {\n console.log(key);\n}\n// Prints:\n// 0\n// 1\n// 2\n// 3\n// 4\n// 5\n
"
},
{
"textRaw": "`buf.lastIndexOf(value[, byteOffset][, encoding])`",
"type": "method",
"name": "lastIndexOf",
"meta": {
"added": [
"v6.0.0"
],
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/10236",
"description": "The `value` can now be a `Uint8Array`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} The index of the last occurrence of `value` in `buf`, or `-1` if `buf` does not contain `value`.",
"name": "return",
"type": "integer",
"desc": "The index of the last occurrence of `value` in `buf`, or `-1` if `buf` does not contain `value`."
},
"params": [
{
"textRaw": "`value` {string|Buffer|Uint8Array|integer} What to search for.",
"name": "value",
"type": "string|Buffer|Uint8Array|integer",
"desc": "What to search for."
},
{
"textRaw": "`byteOffset` {integer} Where to begin searching in `buf`. If negative, then offset is calculated from the end of `buf`. **Default:** `buf.length - 1`.",
"name": "byteOffset",
"type": "integer",
"default": "`buf.length - 1`",
"desc": "Where to begin searching in `buf`. If negative, then offset is calculated from the end of `buf`."
},
{
"textRaw": "`encoding` {string} If `value` is a string, this is the encoding used to determine the binary representation of the string that will be searched for in `buf`. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "If `value` is a string, this is the encoding used to determine the binary representation of the string that will be searched for in `buf`."
}
]
}
],
"desc": "Identical to buf.indexOf()
, except the last occurrence of value
is found\nrather than the first occurrence.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('this buffer is a buffer');\n\nconsole.log(buf.lastIndexOf('this'));\n// Prints: 0\nconsole.log(buf.lastIndexOf('buffer'));\n// Prints: 17\nconsole.log(buf.lastIndexOf(Buffer.from('buffer')));\n// Prints: 17\nconsole.log(buf.lastIndexOf(97));\n// Prints: 15 (97 is the decimal ASCII value for 'a')\nconsole.log(buf.lastIndexOf(Buffer.from('yolo')));\n// Prints: -1\nconsole.log(buf.lastIndexOf('buffer', 5));\n// Prints: 5\nconsole.log(buf.lastIndexOf('buffer', 4));\n// Prints: -1\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'utf16le');\n\nconsole.log(utf16Buffer.lastIndexOf('\\u03a3', undefined, 'utf16le'));\n// Prints: 6\nconsole.log(utf16Buffer.lastIndexOf('\\u03a3', -5, 'utf16le'));\n// Prints: 4\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('this buffer is a buffer');\n\nconsole.log(buf.lastIndexOf('this'));\n// Prints: 0\nconsole.log(buf.lastIndexOf('buffer'));\n// Prints: 17\nconsole.log(buf.lastIndexOf(Buffer.from('buffer')));\n// Prints: 17\nconsole.log(buf.lastIndexOf(97));\n// Prints: 15 (97 is the decimal ASCII value for 'a')\nconsole.log(buf.lastIndexOf(Buffer.from('yolo')));\n// Prints: -1\nconsole.log(buf.lastIndexOf('buffer', 5));\n// Prints: 5\nconsole.log(buf.lastIndexOf('buffer', 4));\n// Prints: -1\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'utf16le');\n\nconsole.log(utf16Buffer.lastIndexOf('\\u03a3', undefined, 'utf16le'));\n// Prints: 6\nconsole.log(utf16Buffer.lastIndexOf('\\u03a3', -5, 'utf16le'));\n// Prints: 4\n
\nIf value
is not a string, number, or Buffer
, this method will throw a\nTypeError
. If value
is a number, it will be coerced to a valid byte value,\nan integer between 0 and 255.
If byteOffset
is not a number, it will be coerced to a number. Any arguments\nthat coerce to NaN
, like {}
or undefined
, will search the whole buffer.\nThis behavior matches String.prototype.lastIndexOf()
.
import { Buffer } from 'node:buffer';\n\nconst b = Buffer.from('abcdef');\n\n// Passing a value that's a number, but not a valid byte.\n// Prints: 2, equivalent to searching for 99 or 'c'.\nconsole.log(b.lastIndexOf(99.9));\nconsole.log(b.lastIndexOf(256 + 99));\n\n// Passing a byteOffset that coerces to NaN.\n// Prints: 1, searching the whole buffer.\nconsole.log(b.lastIndexOf('b', undefined));\nconsole.log(b.lastIndexOf('b', {}));\n\n// Passing a byteOffset that coerces to 0.\n// Prints: -1, equivalent to passing 0.\nconsole.log(b.lastIndexOf('b', null));\nconsole.log(b.lastIndexOf('b', []));\n
\nconst { Buffer } = require('node:buffer');\n\nconst b = Buffer.from('abcdef');\n\n// Passing a value that's a number, but not a valid byte.\n// Prints: 2, equivalent to searching for 99 or 'c'.\nconsole.log(b.lastIndexOf(99.9));\nconsole.log(b.lastIndexOf(256 + 99));\n\n// Passing a byteOffset that coerces to NaN.\n// Prints: 1, searching the whole buffer.\nconsole.log(b.lastIndexOf('b', undefined));\nconsole.log(b.lastIndexOf('b', {}));\n\n// Passing a byteOffset that coerces to 0.\n// Prints: -1, equivalent to passing 0.\nconsole.log(b.lastIndexOf('b', null));\nconsole.log(b.lastIndexOf('b', []));\n
\nIf value
is an empty string or empty Buffer
, byteOffset
will be returned.
Reads a signed, big-endian 64-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed\nvalues.
Reads a signed, little-endian 64-bit integer from buf
at the specified\noffset
.
Integers read from a Buffer
are interpreted as two's complement signed\nvalues.
Reads an unsigned, big-endian 64-bit integer from buf
at the specified\noffset
.
This function is also available under the readBigUint64BE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);\n\nconsole.log(buf.readBigUInt64BE(0));\n// Prints: 4294967295n\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);\n\nconsole.log(buf.readBigUInt64BE(0));\n// Prints: 4294967295n\n
"
},
{
"textRaw": "`buf.readBigUInt64LE([offset])`",
"type": "method",
"name": "readBigUInt64LE",
"meta": {
"added": [
"v12.0.0",
"v10.20.0"
],
"changes": [
{
"version": [
"v14.10.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34960",
"description": "This function is also available as `buf.readBigUint64LE()`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {bigint}",
"name": "return",
"type": "bigint"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy: `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Reads an unsigned, little-endian 64-bit integer from buf
at the specified\noffset
.
This function is also available under the readBigUint64LE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);\n\nconsole.log(buf.readBigUInt64LE(0));\n// Prints: 18446744069414584320n\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);\n\nconsole.log(buf.readBigUInt64LE(0));\n// Prints: 18446744069414584320n\n
"
},
{
"textRaw": "`buf.readDoubleBE([offset])`",
"type": "method",
"name": "readDoubleBE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Reads a 64-bit, big-endian double from buf
at the specified offset
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleBE(0));\n// Prints: 8.20788039913184e-304\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleBE(0));\n// Prints: 8.20788039913184e-304\n
"
},
{
"textRaw": "`buf.readDoubleLE([offset])`",
"type": "method",
"name": "readDoubleLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Reads a 64-bit, little-endian double from buf
at the specified offset
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleLE(0));\n// Prints: 5.447603722011605e-270\nconsole.log(buf.readDoubleLE(1));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleLE(0));\n// Prints: 5.447603722011605e-270\nconsole.log(buf.readDoubleLE(1));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readFloatBE([offset])`",
"type": "method",
"name": "readFloatBE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a 32-bit, big-endian float from buf
at the specified offset
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatBE(0));\n// Prints: 2.387939260590663e-38\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatBE(0));\n// Prints: 2.387939260590663e-38\n
"
},
{
"textRaw": "`buf.readFloatLE([offset])`",
"type": "method",
"name": "readFloatLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a 32-bit, little-endian float from buf
at the specified offset
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatLE(0));\n// Prints: 1.539989614439558e-36\nconsole.log(buf.readFloatLE(1));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatLE(0));\n// Prints: 1.539989614439558e-36\nconsole.log(buf.readFloatLE(1));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readInt8([offset])`",
"type": "method",
"name": "readInt8",
"meta": {
"added": [
"v0.5.0"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 1`."
}
]
}
],
"desc": "Reads a signed 8-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([-1, 5]);\n\nconsole.log(buf.readInt8(0));\n// Prints: -1\nconsole.log(buf.readInt8(1));\n// Prints: 5\nconsole.log(buf.readInt8(2));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([-1, 5]);\n\nconsole.log(buf.readInt8(0));\n// Prints: -1\nconsole.log(buf.readInt8(1));\n// Prints: 5\nconsole.log(buf.readInt8(2));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readInt16BE([offset])`",
"type": "method",
"name": "readInt16BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads a signed, big-endian 16-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16BE(0));\n// Prints: 5\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16BE(0));\n// Prints: 5\n
"
},
{
"textRaw": "`buf.readInt16LE([offset])`",
"type": "method",
"name": "readInt16LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads a signed, little-endian 16-bit integer from buf
at the specified\noffset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16LE(0));\n// Prints: 1280\nconsole.log(buf.readInt16LE(1));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16LE(0));\n// Prints: 1280\nconsole.log(buf.readInt16LE(1));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readInt32BE([offset])`",
"type": "method",
"name": "readInt32BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a signed, big-endian 32-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32BE(0));\n// Prints: 5\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32BE(0));\n// Prints: 5\n
"
},
{
"textRaw": "`buf.readInt32LE([offset])`",
"type": "method",
"name": "readInt32LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a signed, little-endian 32-bit integer from buf
at the specified\noffset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32LE(0));\n// Prints: 83886080\nconsole.log(buf.readInt32LE(1));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32LE(0));\n// Prints: 83886080\nconsole.log(buf.readInt32LE(1));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readIntBE(offset, byteLength)`",
"type": "method",
"name": "readIntBE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to read. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to read. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Reads byteLength
number of bytes from buf
at the specified offset
\nand interprets the result as a big-endian, two's complement signed value\nsupporting up to 48 bits of accuracy.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE.\nconsole.log(buf.readIntBE(1, 0).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE.\nconsole.log(buf.readIntBE(1, 0).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readIntLE(offset, byteLength)`",
"type": "method",
"name": "readIntLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to read. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to read. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Reads byteLength
number of bytes from buf
at the specified offset
\nand interprets the result as a little-endian, two's complement signed value\nsupporting up to 48 bits of accuracy.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntLE(0, 6).toString(16));\n// Prints: -546f87a9cbee\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntLE(0, 6).toString(16));\n// Prints: -546f87a9cbee\n
"
},
{
"textRaw": "`buf.readUInt8([offset])`",
"type": "method",
"name": "readUInt8",
"meta": {
"added": [
"v0.5.0"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUint8()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 1`."
}
]
}
],
"desc": "Reads an unsigned 8-bit integer from buf
at the specified offset
.
This function is also available under the readUint8
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([1, -2]);\n\nconsole.log(buf.readUInt8(0));\n// Prints: 1\nconsole.log(buf.readUInt8(1));\n// Prints: 254\nconsole.log(buf.readUInt8(2));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([1, -2]);\n\nconsole.log(buf.readUInt8(0));\n// Prints: 1\nconsole.log(buf.readUInt8(1));\n// Prints: 254\nconsole.log(buf.readUInt8(2));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readUInt16BE([offset])`",
"type": "method",
"name": "readUInt16BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUint16BE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads an unsigned, big-endian 16-bit integer from buf
at the specified\noffset
.
This function is also available under the readUint16BE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16BE(0).toString(16));\n// Prints: 1234\nconsole.log(buf.readUInt16BE(1).toString(16));\n// Prints: 3456\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16BE(0).toString(16));\n// Prints: 1234\nconsole.log(buf.readUInt16BE(1).toString(16));\n// Prints: 3456\n
"
},
{
"textRaw": "`buf.readUInt16LE([offset])`",
"type": "method",
"name": "readUInt16LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUint16LE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads an unsigned, little-endian 16-bit integer from buf
at the specified\noffset
.
This function is also available under the readUint16LE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16LE(0).toString(16));\n// Prints: 3412\nconsole.log(buf.readUInt16LE(1).toString(16));\n// Prints: 5634\nconsole.log(buf.readUInt16LE(2).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16LE(0).toString(16));\n// Prints: 3412\nconsole.log(buf.readUInt16LE(1).toString(16));\n// Prints: 5634\nconsole.log(buf.readUInt16LE(2).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readUInt32BE([offset])`",
"type": "method",
"name": "readUInt32BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUint32BE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads an unsigned, big-endian 32-bit integer from buf
at the specified\noffset
.
This function is also available under the readUint32BE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32BE(0).toString(16));\n// Prints: 12345678\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32BE(0).toString(16));\n// Prints: 12345678\n
"
},
{
"textRaw": "`buf.readUInt32LE([offset])`",
"type": "method",
"name": "readUInt32LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUint32LE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads an unsigned, little-endian 32-bit integer from buf
at the specified\noffset
.
This function is also available under the readUint32LE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32LE(0).toString(16));\n// Prints: 78563412\nconsole.log(buf.readUInt32LE(1).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32LE(0).toString(16));\n// Prints: 78563412\nconsole.log(buf.readUInt32LE(1).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readUIntBE(offset, byteLength)`",
"type": "method",
"name": "readUIntBE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUintBE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to read. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to read. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Reads byteLength
number of bytes from buf
at the specified offset
\nand interprets the result as an unsigned big-endian integer supporting\nup to 48 bits of accuracy.
This function is also available under the readUintBE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readUIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readUIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE.\n
"
},
{
"textRaw": "`buf.readUIntLE(offset, byteLength)`",
"type": "method",
"name": "readUIntLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.readUintLE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to read. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to read. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Reads byteLength
number of bytes from buf
at the specified offset
\nand interprets the result as an unsigned, little-endian integer supporting\nup to 48 bits of accuracy.
This function is also available under the readUintLE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntLE(0, 6).toString(16));\n// Prints: ab9078563412\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntLE(0, 6).toString(16));\n// Prints: ab9078563412\n
"
},
{
"textRaw": "`buf.subarray([start[, end]])`",
"type": "method",
"name": "subarray",
"meta": {
"added": [
"v3.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer}",
"name": "return",
"type": "Buffer"
},
"params": [
{
"textRaw": "`start` {integer} Where the new `Buffer` will start. **Default:** `0`.",
"name": "start",
"type": "integer",
"default": "`0`",
"desc": "Where the new `Buffer` will start."
},
{
"textRaw": "`end` {integer} Where the new `Buffer` will end (not inclusive). **Default:** [`buf.length`][].",
"name": "end",
"type": "integer",
"default": "[`buf.length`][]",
"desc": "Where the new `Buffer` will end (not inclusive)."
}
]
}
],
"desc": "Returns a new Buffer
that references the same memory as the original, but\noffset and cropped by the start
and end
indices.
Specifying end
greater than buf.length
will return the same result as\nthat of end
equal to buf.length
.
This method is inherited from TypedArray.prototype.subarray()
.
Modifying the new Buffer
slice will modify the memory in the original Buffer
\nbecause the allocated memory of the two objects overlap.
import { Buffer } from 'node:buffer';\n\n// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte\n// from the original `Buffer`.\n\nconst buf1 = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf1[i] = i + 97;\n}\n\nconst buf2 = buf1.subarray(0, 3);\n\nconsole.log(buf2.toString('ascii', 0, buf2.length));\n// Prints: abc\n\nbuf1[0] = 33;\n\nconsole.log(buf2.toString('ascii', 0, buf2.length));\n// Prints: !bc\n
\nconst { Buffer } = require('node:buffer');\n\n// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte\n// from the original `Buffer`.\n\nconst buf1 = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf1[i] = i + 97;\n}\n\nconst buf2 = buf1.subarray(0, 3);\n\nconsole.log(buf2.toString('ascii', 0, buf2.length));\n// Prints: abc\n\nbuf1[0] = 33;\n\nconsole.log(buf2.toString('ascii', 0, buf2.length));\n// Prints: !bc\n
\nSpecifying negative indexes causes the slice to be generated relative to the\nend of buf
rather than the beginning.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('buffer');\n\nconsole.log(buf.subarray(-6, -1).toString());\n// Prints: buffe\n// (Equivalent to buf.subarray(0, 5).)\n\nconsole.log(buf.subarray(-6, -2).toString());\n// Prints: buff\n// (Equivalent to buf.subarray(0, 4).)\n\nconsole.log(buf.subarray(-5, -2).toString());\n// Prints: uff\n// (Equivalent to buf.subarray(1, 4).)\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('buffer');\n\nconsole.log(buf.subarray(-6, -1).toString());\n// Prints: buffe\n// (Equivalent to buf.subarray(0, 5).)\n\nconsole.log(buf.subarray(-6, -2).toString());\n// Prints: buff\n// (Equivalent to buf.subarray(0, 4).)\n\nconsole.log(buf.subarray(-5, -2).toString());\n// Prints: uff\n// (Equivalent to buf.subarray(1, 4).)\n
"
},
{
"textRaw": "`buf.slice([start[, end]])`",
"type": "method",
"name": "slice",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"version": [
"v17.5.0",
"v16.15.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41596",
"description": "The buf.slice() method has been deprecated."
},
{
"version": [
"v7.1.0",
"v6.9.2"
],
"pr-url": "https://github.com/nodejs/node/pull/9341",
"description": "Coercing the offsets to integers now handles values outside the 32-bit integer range properly."
},
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/9101",
"description": "All offsets are now coerced to integers before doing any calculations with them."
}
]
},
"stability": 0,
"stabilityText": "Deprecated: Use [`buf.subarray`][] instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer}",
"name": "return",
"type": "Buffer"
},
"params": [
{
"textRaw": "`start` {integer} Where the new `Buffer` will start. **Default:** `0`.",
"name": "start",
"type": "integer",
"default": "`0`",
"desc": "Where the new `Buffer` will start."
},
{
"textRaw": "`end` {integer} Where the new `Buffer` will end (not inclusive). **Default:** [`buf.length`][].",
"name": "end",
"type": "integer",
"default": "[`buf.length`][]",
"desc": "Where the new `Buffer` will end (not inclusive)."
}
]
}
],
"desc": "Returns a new Buffer
that references the same memory as the original, but\noffset and cropped by the start
and end
indices.
This method is not compatible with the Uint8Array.prototype.slice()
,\nwhich is a superclass of Buffer
. To copy the slice, use\nUint8Array.prototype.slice()
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('buffer');\n\nconst copiedBuf = Uint8Array.prototype.slice.call(buf);\ncopiedBuf[0]++;\nconsole.log(copiedBuf.toString());\n// Prints: cuffer\n\nconsole.log(buf.toString());\n// Prints: buffer\n\n// With buf.slice(), the original buffer is modified.\nconst notReallyCopiedBuf = buf.slice();\nnotReallyCopiedBuf[0]++;\nconsole.log(notReallyCopiedBuf.toString());\n// Prints: cuffer\nconsole.log(buf.toString());\n// Also prints: cuffer (!)\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('buffer');\n\nconst copiedBuf = Uint8Array.prototype.slice.call(buf);\ncopiedBuf[0]++;\nconsole.log(copiedBuf.toString());\n// Prints: cuffer\n\nconsole.log(buf.toString());\n// Prints: buffer\n\n// With buf.slice(), the original buffer is modified.\nconst notReallyCopiedBuf = buf.slice();\nnotReallyCopiedBuf[0]++;\nconsole.log(notReallyCopiedBuf.toString());\n// Prints: cuffer\nconsole.log(buf.toString());\n// Also prints: cuffer (!)\n
"
},
{
"textRaw": "`buf.swap16()`",
"type": "method",
"name": "swap16",
"meta": {
"added": [
"v5.10.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} A reference to `buf`.",
"name": "return",
"type": "Buffer",
"desc": "A reference to `buf`."
},
"params": []
}
],
"desc": "Interprets buf
as an array of unsigned 16-bit integers and swaps the\nbyte order in-place. Throws ERR_INVALID_BUFFER_SIZE
if buf.length
\nis not a multiple of 2.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap16();\n\nconsole.log(buf1);\n// Prints: <Buffer 02 01 04 03 06 05 08 07>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap16();\n// Throws ERR_INVALID_BUFFER_SIZE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap16();\n\nconsole.log(buf1);\n// Prints: <Buffer 02 01 04 03 06 05 08 07>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap16();\n// Throws ERR_INVALID_BUFFER_SIZE.\n
\nOne convenient use of buf.swap16()
is to perform a fast in-place conversion\nbetween UTF-16 little-endian and UTF-16 big-endian:
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('This is little-endian UTF-16', 'utf16le');\nbuf.swap16(); // Convert to big-endian UTF-16 text.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('This is little-endian UTF-16', 'utf16le');\nbuf.swap16(); // Convert to big-endian UTF-16 text.\n
"
},
{
"textRaw": "`buf.swap32()`",
"type": "method",
"name": "swap32",
"meta": {
"added": [
"v5.10.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} A reference to `buf`.",
"name": "return",
"type": "Buffer",
"desc": "A reference to `buf`."
},
"params": []
}
],
"desc": "Interprets buf
as an array of unsigned 32-bit integers and swaps the\nbyte order in-place. Throws ERR_INVALID_BUFFER_SIZE
if buf.length
\nis not a multiple of 4.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap32();\n\nconsole.log(buf1);\n// Prints: <Buffer 04 03 02 01 08 07 06 05>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap32();\n// Throws ERR_INVALID_BUFFER_SIZE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap32();\n\nconsole.log(buf1);\n// Prints: <Buffer 04 03 02 01 08 07 06 05>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap32();\n// Throws ERR_INVALID_BUFFER_SIZE.\n
"
},
{
"textRaw": "`buf.swap64()`",
"type": "method",
"name": "swap64",
"meta": {
"added": [
"v6.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} A reference to `buf`.",
"name": "return",
"type": "Buffer",
"desc": "A reference to `buf`."
},
"params": []
}
],
"desc": "Interprets buf
as an array of 64-bit numbers and swaps byte order in-place.\nThrows ERR_INVALID_BUFFER_SIZE
if buf.length
is not a multiple of 8.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap64();\n\nconsole.log(buf1);\n// Prints: <Buffer 08 07 06 05 04 03 02 01>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap64();\n// Throws ERR_INVALID_BUFFER_SIZE.\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap64();\n\nconsole.log(buf1);\n// Prints: <Buffer 08 07 06 05 04 03 02 01>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap64();\n// Throws ERR_INVALID_BUFFER_SIZE.\n
"
},
{
"textRaw": "`buf.toJSON()`",
"type": "method",
"name": "toJSON",
"meta": {
"added": [
"v0.9.2"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Returns a JSON representation of buf
. JSON.stringify()
implicitly calls\nthis function when stringifying a Buffer
instance.
Buffer.from()
accepts objects in the format returned from this method.\nIn particular, Buffer.from(buf.toJSON())
works like Buffer.from(buf)
.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);\nconst json = JSON.stringify(buf);\n\nconsole.log(json);\n// Prints: {\"type\":\"Buffer\",\"data\":[1,2,3,4,5]}\n\nconst copy = JSON.parse(json, (key, value) => {\n return value && value.type === 'Buffer' ?\n Buffer.from(value) :\n value;\n});\n\nconsole.log(copy);\n// Prints: <Buffer 01 02 03 04 05>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);\nconst json = JSON.stringify(buf);\n\nconsole.log(json);\n// Prints: {\"type\":\"Buffer\",\"data\":[1,2,3,4,5]}\n\nconst copy = JSON.parse(json, (key, value) => {\n return value && value.type === 'Buffer' ?\n Buffer.from(value) :\n value;\n});\n\nconsole.log(copy);\n// Prints: <Buffer 01 02 03 04 05>\n
"
},
{
"textRaw": "`buf.toString([encoding[, start[, end]]])`",
"type": "method",
"name": "toString",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`encoding` {string} The character encoding to use. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "The character encoding to use."
},
{
"textRaw": "`start` {integer} The byte offset to start decoding at. **Default:** `0`.",
"name": "start",
"type": "integer",
"default": "`0`",
"desc": "The byte offset to start decoding at."
},
{
"textRaw": "`end` {integer} The byte offset to stop decoding at (not inclusive). **Default:** [`buf.length`][].",
"name": "end",
"type": "integer",
"default": "[`buf.length`][]",
"desc": "The byte offset to stop decoding at (not inclusive)."
}
]
}
],
"desc": "Decodes buf
to a string according to the specified character encoding in\nencoding
. start
and end
may be passed to decode only a subset of buf
.
If encoding
is 'utf8'
and a byte sequence in the input is not valid UTF-8,\nthen each invalid byte is replaced with the replacement character U+FFFD
.
The maximum length of a string instance (in UTF-16 code units) is available\nas buffer.constants.MAX_STRING_LENGTH
.
import { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf1[i] = i + 97;\n}\n\nconsole.log(buf1.toString('utf8'));\n// Prints: abcdefghijklmnopqrstuvwxyz\nconsole.log(buf1.toString('utf8', 0, 5));\n// Prints: abcde\n\nconst buf2 = Buffer.from('tést');\n\nconsole.log(buf2.toString('hex'));\n// Prints: 74c3a97374\nconsole.log(buf2.toString('utf8', 0, 3));\n// Prints: té\nconsole.log(buf2.toString(undefined, 0, 3));\n// Prints: té\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'.\n buf1[i] = i + 97;\n}\n\nconsole.log(buf1.toString('utf8'));\n// Prints: abcdefghijklmnopqrstuvwxyz\nconsole.log(buf1.toString('utf8', 0, 5));\n// Prints: abcde\n\nconst buf2 = Buffer.from('tést');\n\nconsole.log(buf2.toString('hex'));\n// Prints: 74c3a97374\nconsole.log(buf2.toString('utf8', 0, 3));\n// Prints: té\nconsole.log(buf2.toString(undefined, 0, 3));\n// Prints: té\n
"
},
{
"textRaw": "`buf.values()`",
"type": "method",
"name": "values",
"meta": {
"added": [
"v1.1.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Iterator}",
"name": "return",
"type": "Iterator"
},
"params": []
}
],
"desc": "Creates and returns an iterator for buf
values (bytes). This function is\ncalled automatically when a Buffer
is used in a for..of
statement.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.from('buffer');\n\nfor (const value of buf.values()) {\n console.log(value);\n}\n// Prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\n\nfor (const value of buf) {\n console.log(value);\n}\n// Prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.from('buffer');\n\nfor (const value of buf.values()) {\n console.log(value);\n}\n// Prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\n\nfor (const value of buf) {\n console.log(value);\n}\n// Prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\n
"
},
{
"textRaw": "`buf.write(string[, offset[, length]][, encoding])`",
"type": "method",
"name": "write",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} Number of bytes written.",
"name": "return",
"type": "integer",
"desc": "Number of bytes written."
},
"params": [
{
"textRaw": "`string` {string} String to write to `buf`.",
"name": "string",
"type": "string",
"desc": "String to write to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write `string`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write `string`."
},
{
"textRaw": "`length` {integer} Maximum number of bytes to write (written bytes will not exceed `buf.length - offset`). **Default:** `buf.length - offset`.",
"name": "length",
"type": "integer",
"default": "`buf.length - offset`",
"desc": "Maximum number of bytes to write (written bytes will not exceed `buf.length - offset`)."
},
{
"textRaw": "`encoding` {string} The character encoding of `string`. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "The character encoding of `string`."
}
]
}
],
"desc": "Writes string
to buf
at offset
according to the character encoding in\nencoding
. The length
parameter is the number of bytes to write. If buf
did\nnot contain enough space to fit the entire string, only part of string
will be\nwritten. However, partially encoded characters will not be written.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.alloc(256);\n\nconst len = buf.write('\\u00bd + \\u00bc = \\u00be', 0);\n\nconsole.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);\n// Prints: 12 bytes: ½ + ¼ = ¾\n\nconst buffer = Buffer.alloc(10);\n\nconst length = buffer.write('abcd', 8);\n\nconsole.log(`${length} bytes: ${buffer.toString('utf8', 8, 10)}`);\n// Prints: 2 bytes : ab\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.alloc(256);\n\nconst len = buf.write('\\u00bd + \\u00bc = \\u00be', 0);\n\nconsole.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);\n// Prints: 12 bytes: ½ + ¼ = ¾\n\nconst buffer = Buffer.alloc(10);\n\nconst length = buffer.write('abcd', 8);\n\nconsole.log(`${length} bytes: ${buffer.toString('utf8', 8, 10)}`);\n// Prints: 2 bytes : ab\n
"
},
{
"textRaw": "`buf.writeBigInt64BE(value[, offset])`",
"type": "method",
"name": "writeBigInt64BE",
"meta": {
"added": [
"v12.0.0",
"v10.20.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {bigint} Number to be written to `buf`.",
"name": "value",
"type": "bigint",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian.
value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigInt64BE(0x0102030405060708n, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigInt64BE(0x0102030405060708n, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n
"
},
{
"textRaw": "`buf.writeBigInt64LE(value[, offset])`",
"type": "method",
"name": "writeBigInt64LE",
"meta": {
"added": [
"v12.0.0",
"v10.20.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {bigint} Number to be written to `buf`.",
"name": "value",
"type": "bigint",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian.
value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigInt64LE(0x0102030405060708n, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 08 07 06 05 04 03 02 01>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigInt64LE(0x0102030405060708n, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 08 07 06 05 04 03 02 01>\n
"
},
{
"textRaw": "`buf.writeBigUInt64BE(value[, offset])`",
"type": "method",
"name": "writeBigUInt64BE",
"meta": {
"added": [
"v12.0.0",
"v10.20.0"
],
"changes": [
{
"version": [
"v14.10.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34960",
"description": "This function is also available as `buf.writeBigUint64BE()`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {bigint} Number to be written to `buf`.",
"name": "value",
"type": "bigint",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian.
This function is also available under the writeBigUint64BE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigUInt64BE(0xdecafafecacefaden, 0);\n\nconsole.log(buf);\n// Prints: <Buffer de ca fa fe ca ce fa de>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigUInt64BE(0xdecafafecacefaden, 0);\n\nconsole.log(buf);\n// Prints: <Buffer de ca fa fe ca ce fa de>\n
"
},
{
"textRaw": "`buf.writeBigUInt64LE(value[, offset])`",
"type": "method",
"name": "writeBigUInt64LE",
"meta": {
"added": [
"v12.0.0",
"v10.20.0"
],
"changes": [
{
"version": [
"v14.10.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34960",
"description": "This function is also available as `buf.writeBigUint64LE()`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {bigint} Number to be written to `buf`.",
"name": "value",
"type": "bigint",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy: `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigUInt64LE(0xdecafafecacefaden, 0);\n\nconsole.log(buf);\n// Prints: <Buffer de fa ce ca fe fa ca de>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeBigUInt64LE(0xdecafafecacefaden, 0);\n\nconsole.log(buf);\n// Prints: <Buffer de fa ce ca fe fa ca de>\n
\nThis function is also available under the writeBigUint64LE
alias.
Writes value
to buf
at the specified offset
as big-endian. The value
\nmust be a JavaScript number. Behavior is undefined when value
is anything\nother than a JavaScript number.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeDoubleBE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeDoubleBE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>\n
"
},
{
"textRaw": "`buf.writeDoubleLE(value[, offset])`",
"type": "method",
"name": "writeDoubleLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {number} Number to be written to `buf`.",
"name": "value",
"type": "number",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 8`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian. The value
\nmust be a JavaScript number. Behavior is undefined when value
is anything\nother than a JavaScript number.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeDoubleLE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(8);\n\nbuf.writeDoubleLE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>\n
"
},
{
"textRaw": "`buf.writeFloatBE(value[, offset])`",
"type": "method",
"name": "writeFloatBE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {number} Number to be written to `buf`.",
"name": "value",
"type": "number",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian. Behavior is\nundefined when value
is anything other than a JavaScript number.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 4f 4a fe bb>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 4f 4a fe bb>\n
"
},
{
"textRaw": "`buf.writeFloatLE(value[, offset])`",
"type": "method",
"name": "writeFloatLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {number} Number to be written to `buf`.",
"name": "value",
"type": "number",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian. Behavior is\nundefined when value
is anything other than a JavaScript number.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer bb fe 4a 4f>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer bb fe 4a 4f>\n
"
},
{
"textRaw": "`buf.writeInt8(value[, offset])`",
"type": "method",
"name": "writeInt8",
"meta": {
"added": [
"v0.5.0"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 1`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
. value
must be a valid\nsigned 8-bit integer. Behavior is undefined when value
is anything other than\na signed 8-bit integer.
value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt8(2, 0);\nbuf.writeInt8(-2, 1);\n\nconsole.log(buf);\n// Prints: <Buffer 02 fe>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt8(2, 0);\nbuf.writeInt8(-2, 1);\n\nconsole.log(buf);\n// Prints: <Buffer 02 fe>\n
"
},
{
"textRaw": "`buf.writeInt16BE(value[, offset])`",
"type": "method",
"name": "writeInt16BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian. The value
\nmust be a valid signed 16-bit integer. Behavior is undefined when value
is\nanything other than a signed 16-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt16BE(0x0102, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt16BE(0x0102, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02>\n
"
},
{
"textRaw": "`buf.writeInt16LE(value[, offset])`",
"type": "method",
"name": "writeInt16LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian. The value
\nmust be a valid signed 16-bit integer. Behavior is undefined when value
is\nanything other than a signed 16-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt16LE(0x0304, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 04 03>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt16LE(0x0304, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 04 03>\n
"
},
{
"textRaw": "`buf.writeInt32BE(value[, offset])`",
"type": "method",
"name": "writeInt32BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian. The value
\nmust be a valid signed 32-bit integer. Behavior is undefined when value
is\nanything other than a signed 32-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt32BE(0x01020304, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt32BE(0x01020304, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04>\n
"
},
{
"textRaw": "`buf.writeInt32LE(value[, offset])`",
"type": "method",
"name": "writeInt32LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian. The value
\nmust be a valid signed 32-bit integer. Behavior is undefined when value
is\nanything other than a signed 32-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt32LE(0x05060708, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 08 07 06 05>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt32LE(0x05060708, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 08 07 06 05>\n
"
},
{
"textRaw": "`buf.writeIntBE(value, offset, byteLength)`",
"type": "method",
"name": "writeIntBE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to write. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to write. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Writes byteLength
bytes of value
to buf
at the specified offset
\nas big-endian. Supports up to 48 bits of accuracy. Behavior is undefined when\nvalue
is anything other than a signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n
"
},
{
"textRaw": "`buf.writeIntLE(value, offset, byteLength)`",
"type": "method",
"name": "writeIntLE",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to write. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to write. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Writes byteLength
bytes of value
to buf
at the specified offset
\nas little-endian. Supports up to 48 bits of accuracy. Behavior is undefined\nwhen value
is anything other than a signed integer.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\n
"
},
{
"textRaw": "`buf.writeUInt8(value[, offset])`",
"type": "method",
"name": "writeUInt8",
"meta": {
"added": [
"v0.5.0"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUint8()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 1`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 1`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
. value
must be a\nvalid unsigned 8-bit integer. Behavior is undefined when value
is anything\nother than an unsigned 8-bit integer.
This function is also available under the writeUint8
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt8(0x3, 0);\nbuf.writeUInt8(0x4, 1);\nbuf.writeUInt8(0x23, 2);\nbuf.writeUInt8(0x42, 3);\n\nconsole.log(buf);\n// Prints: <Buffer 03 04 23 42>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt8(0x3, 0);\nbuf.writeUInt8(0x4, 1);\nbuf.writeUInt8(0x23, 2);\nbuf.writeUInt8(0x42, 3);\n\nconsole.log(buf);\n// Prints: <Buffer 03 04 23 42>\n
"
},
{
"textRaw": "`buf.writeUInt16BE(value[, offset])`",
"type": "method",
"name": "writeUInt16BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUint16BE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian. The value
\nmust be a valid unsigned 16-bit integer. Behavior is undefined when value
\nis anything other than an unsigned 16-bit integer.
This function is also available under the writeUint16BE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt16BE(0xdead, 0);\nbuf.writeUInt16BE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer de ad be ef>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt16BE(0xdead, 0);\nbuf.writeUInt16BE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer de ad be ef>\n
"
},
{
"textRaw": "`buf.writeUInt16LE(value[, offset])`",
"type": "method",
"name": "writeUInt16LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUint16LE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian. The value
\nmust be a valid unsigned 16-bit integer. Behavior is undefined when value
is\nanything other than an unsigned 16-bit integer.
This function is also available under the writeUint16LE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer ad de ef be>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer ad de ef be>\n
"
},
{
"textRaw": "`buf.writeUInt32BE(value[, offset])`",
"type": "method",
"name": "writeUInt32BE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUint32BE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as big-endian. The value
\nmust be a valid unsigned 32-bit integer. Behavior is undefined when value
\nis anything other than an unsigned 32-bit integer.
This function is also available under the writeUint32BE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer fe ed fa ce>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer fe ed fa ce>\n
"
},
{
"textRaw": "`buf.writeUInt32LE(value[, offset])`",
"type": "method",
"name": "writeUInt32LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUint32LE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`. **Default:** `0`.",
"name": "offset",
"type": "integer",
"default": "`0`",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Writes value
to buf
at the specified offset
as little-endian. The value
\nmust be a valid unsigned 32-bit integer. Behavior is undefined when value
is\nanything other than an unsigned 32-bit integer.
This function is also available under the writeUint32LE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer ce fa ed fe>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer ce fa ed fe>\n
"
},
{
"textRaw": "`buf.writeUIntBE(value, offset, byteLength)`",
"type": "method",
"name": "writeUIntBE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUintBE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to write. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to write. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Writes byteLength
bytes of value
to buf
at the specified offset
\nas big-endian. Supports up to 48 bits of accuracy. Behavior is undefined\nwhen value
is anything other than an unsigned integer.
This function is also available under the writeUintBE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n
"
},
{
"textRaw": "`buf.writeUIntLE(value, offset, byteLength)`",
"type": "method",
"name": "writeUIntLE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": [
"v14.9.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34729",
"description": "This function is also available as `buf.writeUintLE()`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18395",
"description": "Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer} `offset` plus the number of bytes written.",
"name": "return",
"type": "integer",
"desc": "`offset` plus the number of bytes written."
},
"params": [
{
"textRaw": "`value` {integer} Number to be written to `buf`.",
"name": "value",
"type": "integer",
"desc": "Number to be written to `buf`."
},
{
"textRaw": "`offset` {integer} Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to write. Must satisfy `0 <= offset <= buf.length - byteLength`."
},
{
"textRaw": "`byteLength` {integer} Number of bytes to write. Must satisfy `0 < byteLength <= 6`.",
"name": "byteLength",
"type": "integer",
"desc": "Number of bytes to write. Must satisfy `0 < byteLength <= 6`."
}
]
}
],
"desc": "Writes byteLength
bytes of value
to buf
at the specified offset
\nas little-endian. Supports up to 48 bits of accuracy. Behavior is undefined\nwhen value
is anything other than an unsigned integer.
This function is also available under the writeUintLE
alias.
import { Buffer } from 'node:buffer';\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\n
\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`array` {integer\\[]} An array of bytes to copy from.",
"name": "array",
"type": "integer\\[]",
"desc": "An array of bytes to copy from."
}
],
"desc": "See Buffer.from(array)
.
See\nBuffer.from(arrayBuffer[, byteOffset[, length]])
.
See Buffer.from(buffer)
.
See Buffer.alloc()
and Buffer.allocUnsafe()
. This variant of the\nconstructor is equivalent to Buffer.alloc()
.
See Buffer.from(string[, encoding])
.
A File
provides information about files.
The name of the File
.
The last modified date of the File
.
Node.js provides a number of C++ APIs that can be used to execute JavaScript\nin a Node.js environment from other C++ software.
\nThe documentation for these APIs can be found in src/node.h in the Node.js\nsource tree. In addition to the APIs exposed by Node.js, some required concepts\nare provided by the V8 embedder API.
\nBecause using Node.js as an embedded library is different from writing code\nthat is executed by Node.js, breaking changes do not follow typical Node.js\ndeprecation policy and may occur on each semver-major release without prior\nwarning.
\nThe following sections will provide an overview over how to use these APIs\nto create an application from scratch that will perform the equivalent of\nnode -e <code>
, i.e. that will take a piece of JavaScript and run it in\na Node.js-specific environment.
The full code can be found in the Node.js source tree.
", "modules": [ { "textRaw": "Setting up per-process state", "name": "setting_up_per-process_state", "desc": "Node.js requires some per-process state management in order to run:
\nv8::Platform
instance.The following example shows how these can be set up. Some class names are from\nthe node
and v8
C++ namespaces, respectively.
int main(int argc, char** argv) {\n argv = uv_setup_args(argc, argv);\n std::vector<std::string> args(argv, argv + argc);\n // Parse Node.js CLI options, and print any errors that have occurred while\n // trying to parse them.\n std::unique_ptr<node::InitializationResult> result =\n node::InitializeOncePerProcess(args, {\n node::ProcessInitializationFlags::kNoInitializeV8,\n node::ProcessInitializationFlags::kNoInitializeNodeV8Platform\n });\n\n for (const std::string& error : result->errors())\n fprintf(stderr, \"%s: %s\\n\", args[0].c_str(), error.c_str());\n if (result->early_return() != 0) {\n return result->exit_code();\n }\n\n // Create a v8::Platform instance. `MultiIsolatePlatform::Create()` is a way\n // to create a v8::Platform instance that Node.js can use when creating\n // Worker threads. When no `MultiIsolatePlatform` instance is present,\n // Worker threads are disabled.\n std::unique_ptr<MultiIsolatePlatform> platform =\n MultiIsolatePlatform::Create(4);\n V8::InitializePlatform(platform.get());\n V8::Initialize();\n\n // See below for the contents of this function.\n int ret = RunNodeInstance(\n platform.get(), result->args(), result->exec_args());\n\n V8::Dispose();\n V8::DisposePlatform();\n\n node::TearDownOncePerProcess();\n return ret;\n}\n
",
"type": "module",
"displayName": "Setting up per-process state"
},
{
"textRaw": "Per-instance state",
"name": "per-instance_state",
"meta": {
"changes": [
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35597",
"description": "The `CommonEnvironmentSetup` and `SpinEventLoop` utilities were added."
}
]
},
"desc": "Node.js has a concept of a “Node.js instance”, that is commonly being referred\nto as node::Environment
. Each node::Environment
is associated with:
v8::Isolate
, i.e. one JS Engine instance,uv_loop_t
, i.e. one event loop, andv8::Context
s, but exactly one main v8::Context
.node::IsolateData
instance that contains information that could be\nshared by multiple node::Environment
s that use the same v8::Isolate
.\nCurrently, no testing if performed for this scenario.In order to set up a v8::Isolate
, an v8::ArrayBuffer::Allocator
needs\nto be provided. One possible choice is the default Node.js allocator, which\ncan be created through node::ArrayBufferAllocator::Create()
. Using the Node.js\nallocator allows minor performance optimizations when addons use the Node.js\nC++ Buffer
API, and is required in order to track ArrayBuffer
memory in\nprocess.memoryUsage()
.
Additionally, each v8::Isolate
that is used for a Node.js instance needs to\nbe registered and unregistered with the MultiIsolatePlatform
instance, if one\nis being used, in order for the platform to know which event loop to use\nfor tasks scheduled by the v8::Isolate
.
The node::NewIsolate()
helper function creates a v8::Isolate
,\nsets it up with some Node.js-specific hooks (e.g. the Node.js error handler),\nand registers it with the platform automatically.
int RunNodeInstance(MultiIsolatePlatform* platform,\n const std::vector<std::string>& args,\n const std::vector<std::string>& exec_args) {\n int exit_code = 0;\n\n // Setup up a libuv event loop, v8::Isolate, and Node.js Environment.\n std::vector<std::string> errors;\n std::unique_ptr<CommonEnvironmentSetup> setup =\n CommonEnvironmentSetup::Create(platform, &errors, args, exec_args);\n if (!setup) {\n for (const std::string& err : errors)\n fprintf(stderr, \"%s: %s\\n\", args[0].c_str(), err.c_str());\n return 1;\n }\n\n Isolate* isolate = setup->isolate();\n Environment* env = setup->env();\n\n {\n Locker locker(isolate);\n Isolate::Scope isolate_scope(isolate);\n HandleScope handle_scope(isolate);\n // The v8::Context needs to be entered when node::CreateEnvironment() and\n // node::LoadEnvironment() are being called.\n Context::Scope context_scope(setup->context());\n\n // Set up the Node.js instance for execution, and run code inside of it.\n // There is also a variant that takes a callback and provides it with\n // the `require` and `process` objects, so that it can manually compile\n // and run scripts as needed.\n // The `require` function inside this script does *not* access the file\n // system, and can only load built-in Node.js modules.\n // `module.createRequire()` is being used to create one that is able to\n // load files from the disk, and uses the standard CommonJS file loader\n // instead of the internal-only `require` function.\n MaybeLocal<Value> loadenv_ret = node::LoadEnvironment(\n env,\n \"const publicRequire =\"\n \" require('node:module').createRequire(process.cwd() + '/');\"\n \"globalThis.require = publicRequire;\"\n \"require('node:vm').runInThisContext(process.argv[1]);\");\n\n if (loadenv_ret.IsEmpty()) // There has been a JS exception.\n return 1;\n\n exit_code = node::SpinEventLoop(env).FromMaybe(1);\n\n // node::Stop() can be used to explicitly stop the event loop and keep\n // further JavaScript from running. It can be called from any thread,\n // and will act like worker.terminate() if called from another thread.\n node::Stop(env);\n }\n\n return exit_code;\n}\n
",
"type": "module",
"displayName": "Per-instance state"
}
],
"type": "module",
"displayName": "C++ embedder API",
"source": "doc/api/embedding.md"
},
{
"textRaw": "Child process",
"name": "child_process",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/child_process.js
\nThe node:child_process
module provides the ability to spawn subprocesses in\na manner that is similar, but not identical, to popen(3)
. This capability\nis primarily provided by the child_process.spawn()
function:
const { spawn } = require('node:child_process');\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.stderr.on('data', (data) => {\n console.error(`stderr: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process exited with code ${code}`);\n});\n
\nBy default, pipes for stdin
, stdout
, and stderr
are established between\nthe parent Node.js process and the spawned subprocess. These pipes have\nlimited (and platform-specific) capacity. If the subprocess writes to\nstdout in excess of that limit without the output being captured, the\nsubprocess blocks waiting for the pipe buffer to accept more data. This is\nidentical to the behavior of pipes in the shell. Use the { stdio: 'ignore' }
\noption if the output will not be consumed.
The command lookup is performed using the options.env.PATH
environment\nvariable if env
is in the options
object. Otherwise, process.env.PATH
is\nused. If options.env
is set without PATH
, lookup on Unix is performed\non a default search path search of /usr/bin:/bin
(see your operating system's\nmanual for execvpe/execvp), on Windows the current processes environment\nvariable PATH
is used.
On Windows, environment variables are case-insensitive. Node.js\nlexicographically sorts the env
keys and uses the first one that\ncase-insensitively matches. Only first (in lexicographic order) entry will be\npassed to the subprocess. This might lead to issues on Windows when passing\nobjects to the env
option that have multiple variants of the same key, such as\nPATH
and Path
.
The child_process.spawn()
method spawns the child process asynchronously,\nwithout blocking the Node.js event loop. The child_process.spawnSync()
\nfunction provides equivalent functionality in a synchronous manner that blocks\nthe event loop until the spawned process either exits or is terminated.
For convenience, the node:child_process
module provides a handful of\nsynchronous and asynchronous alternatives to child_process.spawn()
and\nchild_process.spawnSync()
. Each of these alternatives are implemented on\ntop of child_process.spawn()
or child_process.spawnSync()
.
child_process.exec()
: spawns a shell and runs a command within that\nshell, passing the stdout
and stderr
to a callback function when\ncomplete.child_process.execFile()
: similar to child_process.exec()
except\nthat it spawns the command directly without first spawning a shell by\ndefault.child_process.fork()
: spawns a new Node.js process and invokes a\nspecified module with an IPC communication channel established that allows\nsending messages between parent and child.child_process.execSync()
: a synchronous version of\nchild_process.exec()
that will block the Node.js event loop.child_process.execFileSync()
: a synchronous version of\nchild_process.execFile()
that will block the Node.js event loop.For certain use cases, such as automating shell scripts, the\nsynchronous counterparts may be more convenient. In many cases, however,\nthe synchronous methods can have significant impact on performance due to\nstalling the event loop while spawned processes complete.
", "modules": [ { "textRaw": "Asynchronous process creation", "name": "asynchronous_process_creation", "desc": "The child_process.spawn()
, child_process.fork()
, child_process.exec()
,\nand child_process.execFile()
methods all follow the idiomatic asynchronous\nprogramming pattern typical of other Node.js APIs.
Each of the methods returns a ChildProcess
instance. These objects\nimplement the Node.js EventEmitter
API, allowing the parent process to\nregister listener functions that are called when certain events occur during\nthe life cycle of the child process.
The child_process.exec()
and child_process.execFile()
methods\nadditionally allow for an optional callback
function to be specified that is\ninvoked when the child process terminates.
The importance of the distinction between child_process.exec()
and\nchild_process.execFile()
can vary based on platform. On Unix-type\noperating systems (Unix, Linux, macOS) child_process.execFile()
can be\nmore efficient because it does not spawn a shell by default. On Windows,\nhowever, .bat
and .cmd
files are not executable on their own without a\nterminal, and therefore cannot be launched using child_process.execFile()
.\nWhen running on Windows, .bat
and .cmd
files can be invoked using\nchild_process.spawn()
with the shell
option set, with\nchild_process.exec()
, or by spawning cmd.exe
and passing the .bat
or\n.cmd
file as an argument (which is what the shell
option and\nchild_process.exec()
do). In any case, if the script filename contains\nspaces it needs to be quoted.
// On Windows Only...\nconst { spawn } = require('node:child_process');\nconst bat = spawn('cmd.exe', ['/c', 'my.bat']);\n\nbat.stdout.on('data', (data) => {\n console.log(data.toString());\n});\n\nbat.stderr.on('data', (data) => {\n console.error(data.toString());\n});\n\nbat.on('exit', (code) => {\n console.log(`Child exited with code ${code}`);\n});\n
\n// OR...\nconst { exec, spawn } = require('node:child_process');\nexec('my.bat', (err, stdout, stderr) => {\n if (err) {\n console.error(err);\n return;\n }\n console.log(stdout);\n});\n\n// Script with spaces in the filename:\nconst bat = spawn('\"my script.cmd\"', ['a', 'b'], { shell: true });\n// or:\nexec('\"my script.cmd\" a b', (err, stdout, stderr) => {\n // ...\n});\n
",
"type": "module",
"displayName": "Spawning `.bat` and `.cmd` files on Windows"
}
],
"methods": [
{
"textRaw": "`child_process.exec(command[, options][, callback])`",
"type": "method",
"name": "exec",
"meta": {
"added": [
"v0.1.90"
],
"changes": [
{
"version": [
"v16.4.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/38862",
"description": "The `cwd` option can be a WHATWG `URL` object using `file:` protocol."
},
{
"version": "v15.4.0",
"pr-url": "https://github.com/nodejs/node/pull/36308",
"description": "AbortSignal support was added."
},
{
"version": "v8.8.0",
"pr-url": "https://github.com/nodejs/node/pull/15380",
"description": "The `windowsHide` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {ChildProcess}",
"name": "return",
"type": "ChildProcess"
},
"params": [
{
"textRaw": "`command` {string} The command to run, with space-separated arguments.",
"name": "command",
"type": "string",
"desc": "The command to run, with space-separated arguments."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`cwd` {string|URL} Current working directory of the child process. **Default:** `process.cwd()`.",
"name": "cwd",
"type": "string|URL",
"default": "`process.cwd()`",
"desc": "Current working directory of the child process."
},
{
"textRaw": "`env` {Object} Environment key-value pairs. **Default:** `process.env`.",
"name": "env",
"type": "Object",
"default": "`process.env`",
"desc": "Environment key-value pairs."
},
{
"textRaw": "`encoding` {string} **Default:** `'utf8'`",
"name": "encoding",
"type": "string",
"default": "`'utf8'`"
},
{
"textRaw": "`shell` {string} Shell to execute the command with. See [Shell requirements][] and [Default Windows shell][]. **Default:** `'/bin/sh'` on Unix, `process.env.ComSpec` on Windows.",
"name": "shell",
"type": "string",
"default": "`'/bin/sh'` on Unix, `process.env.ComSpec` on Windows",
"desc": "Shell to execute the command with. See [Shell requirements][] and [Default Windows shell][]."
},
{
"textRaw": "`signal` {AbortSignal} allows aborting the child process using an AbortSignal.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows aborting the child process using an AbortSignal."
},
{
"textRaw": "`timeout` {number} **Default:** `0`",
"name": "timeout",
"type": "number",
"default": "`0`"
},
{
"textRaw": "`maxBuffer` {number} Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]. **Default:** `1024 * 1024`.",
"name": "maxBuffer",
"type": "number",
"default": "`1024 * 1024`",
"desc": "Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]."
},
{
"textRaw": "`killSignal` {string|integer} **Default:** `'SIGTERM'`",
"name": "killSignal",
"type": "string|integer",
"default": "`'SIGTERM'`"
},
{
"textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).",
"name": "uid",
"type": "number",
"desc": "Sets the user identity of the process (see setuid(2))."
},
{
"textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).",
"name": "gid",
"type": "number",
"desc": "Sets the group identity of the process (see setgid(2))."
},
{
"textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.",
"name": "windowsHide",
"type": "boolean",
"default": "`false`",
"desc": "Hide the subprocess console window that would normally be created on Windows systems."
}
]
},
{
"textRaw": "`callback` {Function} called with the output when process terminates.",
"name": "callback",
"type": "Function",
"desc": "called with the output when process terminates.",
"options": [
{
"textRaw": "`error` {Error}",
"name": "error",
"type": "Error"
},
{
"textRaw": "`stdout` {string|Buffer}",
"name": "stdout",
"type": "string|Buffer"
},
{
"textRaw": "`stderr` {string|Buffer}",
"name": "stderr",
"type": "string|Buffer"
}
]
}
]
}
],
"desc": "Spawns a shell then executes the command
within that shell, buffering any\ngenerated output. The command
string passed to the exec function is processed\ndirectly by the shell and special characters (vary based on\nshell)\nneed to be dealt with accordingly:
const { exec } = require('node:child_process');\n\nexec('\"/path/to/test file/test.sh\" arg1 arg2');\n// Double quotes are used so that the space in the path is not interpreted as\n// a delimiter of multiple arguments.\n\nexec('echo \"The \\\\$HOME variable is $HOME\"');\n// The $HOME variable is escaped in the first instance, but not in the second.\n
\nNever pass unsanitized user input to this function. Any input containing shell\nmetacharacters may be used to trigger arbitrary command execution.
\nIf a callback
function is provided, it is called with the arguments\n(error, stdout, stderr)
. On success, error
will be null
. On error,\nerror
will be an instance of Error
. The error.code
property will be\nthe exit code of the process. By convention, any exit code other than 0
\nindicates an error. error.signal
will be the signal that terminated the\nprocess.
The stdout
and stderr
arguments passed to the callback will contain the\nstdout and stderr output of the child process. By default, Node.js will decode\nthe output as UTF-8 and pass strings to the callback. The encoding
option\ncan be used to specify the character encoding used to decode the stdout and\nstderr output. If encoding
is 'buffer'
, or an unrecognized character\nencoding, Buffer
objects will be passed to the callback instead.
const { exec } = require('node:child_process');\nexec('cat *.js missing_file | wc -l', (error, stdout, stderr) => {\n if (error) {\n console.error(`exec error: ${error}`);\n return;\n }\n console.log(`stdout: ${stdout}`);\n console.error(`stderr: ${stderr}`);\n});\n
\nIf timeout
is greater than 0
, the parent will send the signal\nidentified by the killSignal
property (the default is 'SIGTERM'
) if the\nchild runs longer than timeout
milliseconds.
Unlike the exec(3)
POSIX system call, child_process.exec()
does not replace\nthe existing process and uses a shell to execute the command.
If this method is invoked as its util.promisify()
ed version, it returns\na Promise
for an Object
with stdout
and stderr
properties. The returned\nChildProcess
instance is attached to the Promise
as a child
property. In\ncase of an error (including any error resulting in an exit code other than 0), a\nrejected promise is returned, with the same error
object given in the\ncallback, but with two additional properties stdout
and stderr
.
const util = require('node:util');\nconst exec = util.promisify(require('node:child_process').exec);\n\nasync function lsExample() {\n const { stdout, stderr } = await exec('ls');\n console.log('stdout:', stdout);\n console.error('stderr:', stderr);\n}\nlsExample();\n
\nIf the signal
option is enabled, calling .abort()
on the corresponding\nAbortController
is similar to calling .kill()
on the child process except\nthe error passed to the callback will be an AbortError
:
const { exec } = require('node:child_process');\nconst controller = new AbortController();\nconst { signal } = controller;\nconst child = exec('grep ssh', { signal }, (error) => {\n console.error(error); // an AbortError\n});\ncontroller.abort();\n
"
},
{
"textRaw": "`child_process.execFile(file[, args][, options][, callback])`",
"type": "method",
"name": "execFile",
"meta": {
"added": [
"v0.1.91"
],
"changes": [
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"signatures": [
{
"return": {
"textRaw": "Returns: {ChildProcess}",
"name": "return",
"type": "ChildProcess"
},
"params": [
{
"textRaw": "`file` {string} The name or path of the executable file to run.",
"name": "file",
"type": "string",
"desc": "The name or path of the executable file to run."
},
{
"textRaw": "`args` {string\\[]} List of string arguments.",
"name": "args",
"type": "string\\[]",
"desc": "List of string arguments."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`cwd` {string|URL} Current working directory of the child process.",
"name": "cwd",
"type": "string|URL",
"desc": "Current working directory of the child process."
},
{
"textRaw": "`env` {Object} Environment key-value pairs. **Default:** `process.env`.",
"name": "env",
"type": "Object",
"default": "`process.env`",
"desc": "Environment key-value pairs."
},
{
"textRaw": "`encoding` {string} **Default:** `'utf8'`",
"name": "encoding",
"type": "string",
"default": "`'utf8'`"
},
{
"textRaw": "`timeout` {number} **Default:** `0`",
"name": "timeout",
"type": "number",
"default": "`0`"
},
{
"textRaw": "`maxBuffer` {number} Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]. **Default:** `1024 * 1024`.",
"name": "maxBuffer",
"type": "number",
"default": "`1024 * 1024`",
"desc": "Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]."
},
{
"textRaw": "`killSignal` {string|integer} **Default:** `'SIGTERM'`",
"name": "killSignal",
"type": "string|integer",
"default": "`'SIGTERM'`"
},
{
"textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).",
"name": "uid",
"type": "number",
"desc": "Sets the user identity of the process (see setuid(2))."
},
{
"textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).",
"name": "gid",
"type": "number",
"desc": "Sets the group identity of the process (see setgid(2))."
},
{
"textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.",
"name": "windowsHide",
"type": "boolean",
"default": "`false`",
"desc": "Hide the subprocess console window that would normally be created on Windows systems."
},
{
"textRaw": "`windowsVerbatimArguments` {boolean} No quoting or escaping of arguments is done on Windows. Ignored on Unix. **Default:** `false`.",
"name": "windowsVerbatimArguments",
"type": "boolean",
"default": "`false`",
"desc": "No quoting or escaping of arguments is done on Windows. Ignored on Unix."
},
{
"textRaw": "`shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]. **Default:** `false` (no shell).",
"name": "shell",
"type": "boolean|string",
"default": "`false` (no shell)",
"desc": "If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]."
},
{
"textRaw": "`signal` {AbortSignal} allows aborting the child process using an AbortSignal.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows aborting the child process using an AbortSignal."
}
]
},
{
"textRaw": "`callback` {Function} Called with the output when process terminates.",
"name": "callback",
"type": "Function",
"desc": "Called with the output when process terminates.",
"options": [
{
"textRaw": "`error` {Error}",
"name": "error",
"type": "Error"
},
{
"textRaw": "`stdout` {string|Buffer}",
"name": "stdout",
"type": "string|Buffer"
},
{
"textRaw": "`stderr` {string|Buffer}",
"name": "stderr",
"type": "string|Buffer"
}
]
}
]
}
],
"desc": "The child_process.execFile()
function is similar to child_process.exec()
\nexcept that it does not spawn a shell by default. Rather, the specified\nexecutable file
is spawned directly as a new process making it slightly more\nefficient than child_process.exec()
.
The same options as child_process.exec()
are supported. Since a shell is\nnot spawned, behaviors such as I/O redirection and file globbing are not\nsupported.
const { execFile } = require('node:child_process');\nconst child = execFile('node', ['--version'], (error, stdout, stderr) => {\n if (error) {\n throw error;\n }\n console.log(stdout);\n});\n
\nThe stdout
and stderr
arguments passed to the callback will contain the\nstdout and stderr output of the child process. By default, Node.js will decode\nthe output as UTF-8 and pass strings to the callback. The encoding
option\ncan be used to specify the character encoding used to decode the stdout and\nstderr output. If encoding
is 'buffer'
, or an unrecognized character\nencoding, Buffer
objects will be passed to the callback instead.
If this method is invoked as its util.promisify()
ed version, it returns\na Promise
for an Object
with stdout
and stderr
properties. The returned\nChildProcess
instance is attached to the Promise
as a child
property. In\ncase of an error (including any error resulting in an exit code other than 0), a\nrejected promise is returned, with the same error
object given in the\ncallback, but with two additional properties stdout
and stderr
.
const util = require('node:util');\nconst execFile = util.promisify(require('node:child_process').execFile);\nasync function getVersion() {\n const { stdout } = await execFile('node', ['--version']);\n console.log(stdout);\n}\ngetVersion();\n
\nIf the shell
option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
If the signal
option is enabled, calling .abort()
on the corresponding\nAbortController
is similar to calling .kill()
on the child process except\nthe error passed to the callback will be an AbortError
:
const { execFile } = require('node:child_process');\nconst controller = new AbortController();\nconst { signal } = controller;\nconst child = execFile('node', ['--version'], { signal }, (error) => {\n console.error(error); // an AbortError\n});\ncontroller.abort();\n
"
},
{
"textRaw": "`child_process.fork(modulePath[, args][, options])`",
"type": "method",
"name": "fork",
"meta": {
"added": [
"v0.5.0"
],
"changes": [
{
"version": [
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{
"version": [
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"version": [
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"description": "The `serialization` option is supported now."
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"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/10866",
"description": "The `stdio` option can now be a string."
},
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},
"signatures": [
{
"return": {
"textRaw": "Returns: {ChildProcess}",
"name": "return",
"type": "ChildProcess"
},
"params": [
{
"textRaw": "`modulePath` {string|URL} The module to run in the child.",
"name": "modulePath",
"type": "string|URL",
"desc": "The module to run in the child."
},
{
"textRaw": "`args` {string\\[]} List of string arguments.",
"name": "args",
"type": "string\\[]",
"desc": "List of string arguments."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`cwd` {string|URL} Current working directory of the child process.",
"name": "cwd",
"type": "string|URL",
"desc": "Current working directory of the child process."
},
{
"textRaw": "`detached` {boolean} Prepare child to run independently of its parent process. Specific behavior depends on the platform, see [`options.detached`][]).",
"name": "detached",
"type": "boolean",
"desc": "Prepare child to run independently of its parent process. Specific behavior depends on the platform, see [`options.detached`][])."
},
{
"textRaw": "`env` {Object} Environment key-value pairs. **Default:** `process.env`.",
"name": "env",
"type": "Object",
"default": "`process.env`",
"desc": "Environment key-value pairs."
},
{
"textRaw": "`execPath` {string} Executable used to create the child process.",
"name": "execPath",
"type": "string",
"desc": "Executable used to create the child process."
},
{
"textRaw": "`execArgv` {string\\[]} List of string arguments passed to the executable. **Default:** `process.execArgv`.",
"name": "execArgv",
"type": "string\\[]",
"default": "`process.execArgv`",
"desc": "List of string arguments passed to the executable."
},
{
"textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).",
"name": "gid",
"type": "number",
"desc": "Sets the group identity of the process (see setgid(2))."
},
{
"textRaw": "`serialization` {string} Specify the kind of serialization used for sending messages between processes. Possible values are `'json'` and `'advanced'`. See [Advanced serialization][] for more details. **Default:** `'json'`.",
"name": "serialization",
"type": "string",
"default": "`'json'`",
"desc": "Specify the kind of serialization used for sending messages between processes. Possible values are `'json'` and `'advanced'`. See [Advanced serialization][] for more details."
},
{
"textRaw": "`signal` {AbortSignal} Allows closing the child process using an AbortSignal.",
"name": "signal",
"type": "AbortSignal",
"desc": "Allows closing the child process using an AbortSignal."
},
{
"textRaw": "`killSignal` {string|integer} The signal value to be used when the spawned process will be killed by timeout or abort signal. **Default:** `'SIGTERM'`.",
"name": "killSignal",
"type": "string|integer",
"default": "`'SIGTERM'`",
"desc": "The signal value to be used when the spawned process will be killed by timeout or abort signal."
},
{
"textRaw": "`silent` {boolean} If `true`, stdin, stdout, and stderr of the child will be piped to the parent, otherwise they will be inherited from the parent, see the `'pipe'` and `'inherit'` options for [`child_process.spawn()`][]'s [`stdio`][] for more details. **Default:** `false`.",
"name": "silent",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, stdin, stdout, and stderr of the child will be piped to the parent, otherwise they will be inherited from the parent, see the `'pipe'` and `'inherit'` options for [`child_process.spawn()`][]'s [`stdio`][] for more details."
},
{
"textRaw": "`stdio` {Array|string} See [`child_process.spawn()`][]'s [`stdio`][]. When this option is provided, it overrides `silent`. If the array variant is used, it must contain exactly one item with value `'ipc'` or an error will be thrown. For instance `[0, 1, 2, 'ipc']`.",
"name": "stdio",
"type": "Array|string",
"desc": "See [`child_process.spawn()`][]'s [`stdio`][]. When this option is provided, it overrides `silent`. If the array variant is used, it must contain exactly one item with value `'ipc'` or an error will be thrown. For instance `[0, 1, 2, 'ipc']`."
},
{
"textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).",
"name": "uid",
"type": "number",
"desc": "Sets the user identity of the process (see setuid(2))."
},
{
"textRaw": "`windowsVerbatimArguments` {boolean} No quoting or escaping of arguments is done on Windows. Ignored on Unix. **Default:** `false`.",
"name": "windowsVerbatimArguments",
"type": "boolean",
"default": "`false`",
"desc": "No quoting or escaping of arguments is done on Windows. Ignored on Unix."
},
{
"textRaw": "`timeout` {number} In milliseconds the maximum amount of time the process is allowed to run. **Default:** `undefined`.",
"name": "timeout",
"type": "number",
"default": "`undefined`",
"desc": "In milliseconds the maximum amount of time the process is allowed to run."
}
]
}
]
}
],
"desc": "The child_process.fork()
method is a special case of\nchild_process.spawn()
used specifically to spawn new Node.js processes.\nLike child_process.spawn()
, a ChildProcess
object is returned. The\nreturned ChildProcess
will have an additional communication channel\nbuilt-in that allows messages to be passed back and forth between the parent and\nchild. See subprocess.send()
for details.
Keep in mind that spawned Node.js child processes are\nindependent of the parent with exception of the IPC communication channel\nthat is established between the two. Each process has its own memory, with\ntheir own V8 instances. Because of the additional resource allocations\nrequired, spawning a large number of child Node.js processes is not\nrecommended.
\nBy default, child_process.fork()
will spawn new Node.js instances using the\nprocess.execPath
of the parent process. The execPath
property in the\noptions
object allows for an alternative execution path to be used.
Node.js processes launched with a custom execPath
will communicate with the\nparent process using the file descriptor (fd) identified using the\nenvironment variable NODE_CHANNEL_FD
on the child process.
Unlike the fork(2)
POSIX system call, child_process.fork()
does not clone the\ncurrent process.
The shell
option available in child_process.spawn()
is not supported by\nchild_process.fork()
and will be ignored if set.
If the signal
option is enabled, calling .abort()
on the corresponding\nAbortController
is similar to calling .kill()
on the child process except\nthe error passed to the callback will be an AbortError
:
if (process.argv[2] === 'child') {\n setTimeout(() => {\n console.log(`Hello from ${process.argv[2]}!`);\n }, 1_000);\n} else {\n const { fork } = require('node:child_process');\n const controller = new AbortController();\n const { signal } = controller;\n const child = fork(__filename, ['child'], { signal });\n child.on('error', (err) => {\n // This will be called with err being an AbortError if the controller aborts\n });\n controller.abort(); // Stops the child process\n}\n
"
},
{
"textRaw": "`child_process.spawn(command[, args][, options])`",
"type": "method",
"name": "spawn",
"meta": {
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"signatures": [
{
"return": {
"textRaw": "Returns: {ChildProcess}",
"name": "return",
"type": "ChildProcess"
},
"params": [
{
"textRaw": "`command` {string} The command to run.",
"name": "command",
"type": "string",
"desc": "The command to run."
},
{
"textRaw": "`args` {string\\[]} List of string arguments.",
"name": "args",
"type": "string\\[]",
"desc": "List of string arguments."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`cwd` {string|URL} Current working directory of the child process.",
"name": "cwd",
"type": "string|URL",
"desc": "Current working directory of the child process."
},
{
"textRaw": "`env` {Object} Environment key-value pairs. **Default:** `process.env`.",
"name": "env",
"type": "Object",
"default": "`process.env`",
"desc": "Environment key-value pairs."
},
{
"textRaw": "`argv0` {string} Explicitly set the value of `argv[0]` sent to the child process. This will be set to `command` if not specified.",
"name": "argv0",
"type": "string",
"desc": "Explicitly set the value of `argv[0]` sent to the child process. This will be set to `command` if not specified."
},
{
"textRaw": "`stdio` {Array|string} Child's stdio configuration (see [`options.stdio`][`stdio`]).",
"name": "stdio",
"type": "Array|string",
"desc": "Child's stdio configuration (see [`options.stdio`][`stdio`])."
},
{
"textRaw": "`detached` {boolean} Prepare child to run independently of its parent process. Specific behavior depends on the platform, see [`options.detached`][]).",
"name": "detached",
"type": "boolean",
"desc": "Prepare child to run independently of its parent process. Specific behavior depends on the platform, see [`options.detached`][])."
},
{
"textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).",
"name": "uid",
"type": "number",
"desc": "Sets the user identity of the process (see setuid(2))."
},
{
"textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).",
"name": "gid",
"type": "number",
"desc": "Sets the group identity of the process (see setgid(2))."
},
{
"textRaw": "`serialization` {string} Specify the kind of serialization used for sending messages between processes. Possible values are `'json'` and `'advanced'`. See [Advanced serialization][] for more details. **Default:** `'json'`.",
"name": "serialization",
"type": "string",
"default": "`'json'`",
"desc": "Specify the kind of serialization used for sending messages between processes. Possible values are `'json'` and `'advanced'`. See [Advanced serialization][] for more details."
},
{
"textRaw": "`shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]. **Default:** `false` (no shell).",
"name": "shell",
"type": "boolean|string",
"default": "`false` (no shell)",
"desc": "If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]."
},
{
"textRaw": "`windowsVerbatimArguments` {boolean} No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to `true` automatically when `shell` is specified and is CMD. **Default:** `false`.",
"name": "windowsVerbatimArguments",
"type": "boolean",
"default": "`false`",
"desc": "No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to `true` automatically when `shell` is specified and is CMD."
},
{
"textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.",
"name": "windowsHide",
"type": "boolean",
"default": "`false`",
"desc": "Hide the subprocess console window that would normally be created on Windows systems."
},
{
"textRaw": "`signal` {AbortSignal} allows aborting the child process using an AbortSignal.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows aborting the child process using an AbortSignal."
},
{
"textRaw": "`timeout` {number} In milliseconds the maximum amount of time the process is allowed to run. **Default:** `undefined`.",
"name": "timeout",
"type": "number",
"default": "`undefined`",
"desc": "In milliseconds the maximum amount of time the process is allowed to run."
},
{
"textRaw": "`killSignal` {string|integer} The signal value to be used when the spawned process will be killed by timeout or abort signal. **Default:** `'SIGTERM'`.",
"name": "killSignal",
"type": "string|integer",
"default": "`'SIGTERM'`",
"desc": "The signal value to be used when the spawned process will be killed by timeout or abort signal."
}
]
}
]
}
],
"desc": "The child_process.spawn()
method spawns a new process using the given\ncommand
, with command-line arguments in args
. If omitted, args
defaults\nto an empty array.
If the shell
option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
A third argument may be used to specify additional options, with these defaults:
\nconst defaults = {\n cwd: undefined,\n env: process.env,\n};\n
\nUse cwd
to specify the working directory from which the process is spawned.\nIf not given, the default is to inherit the current working directory. If given,\nbut the path does not exist, the child process emits an ENOENT
error\nand exits immediately. ENOENT
is also emitted when the command\ndoes not exist.
Use env
to specify environment variables that will be visible to the new\nprocess, the default is process.env
.
undefined
values in env
will be ignored.
Example of running ls -lh /usr
, capturing stdout
, stderr
, and the\nexit code:
const { spawn } = require('node:child_process');\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.stderr.on('data', (data) => {\n console.error(`stderr: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process exited with code ${code}`);\n});\n
\nExample: A very elaborate way to run ps ax | grep ssh
const { spawn } = require('node:child_process');\nconst ps = spawn('ps', ['ax']);\nconst grep = spawn('grep', ['ssh']);\n\nps.stdout.on('data', (data) => {\n grep.stdin.write(data);\n});\n\nps.stderr.on('data', (data) => {\n console.error(`ps stderr: ${data}`);\n});\n\nps.on('close', (code) => {\n if (code !== 0) {\n console.log(`ps process exited with code ${code}`);\n }\n grep.stdin.end();\n});\n\ngrep.stdout.on('data', (data) => {\n console.log(data.toString());\n});\n\ngrep.stderr.on('data', (data) => {\n console.error(`grep stderr: ${data}`);\n});\n\ngrep.on('close', (code) => {\n if (code !== 0) {\n console.log(`grep process exited with code ${code}`);\n }\n});\n
\nExample of checking for failed spawn
:
const { spawn } = require('node:child_process');\nconst subprocess = spawn('bad_command');\n\nsubprocess.on('error', (err) => {\n console.error('Failed to start subprocess.');\n});\n
\nCertain platforms (macOS, Linux) will use the value of argv[0]
for the process\ntitle while others (Windows, SunOS) will use command
.
Node.js overwrites argv[0]
with process.execPath
on startup, so\nprocess.argv[0]
in a Node.js child process will not match the argv0
\nparameter passed to spawn
from the parent. Retrieve it with the\nprocess.argv0
property instead.
If the signal
option is enabled, calling .abort()
on the corresponding\nAbortController
is similar to calling .kill()
on the child process except\nthe error passed to the callback will be an AbortError
:
const { spawn } = require('node:child_process');\nconst controller = new AbortController();\nconst { signal } = controller;\nconst grep = spawn('grep', ['ssh'], { signal });\ngrep.on('error', (err) => {\n // This will be called with err being an AbortError if the controller aborts\n});\ncontroller.abort(); // Stops the child process\n
",
"properties": [
{
"textRaw": "`options.detached`",
"name": "detached",
"meta": {
"added": [
"v0.7.10"
],
"changes": []
},
"desc": "On Windows, setting options.detached
to true
makes it possible for the\nchild process to continue running after the parent exits. The child will have\nits own console window. Once enabled for a child process, it cannot be\ndisabled.
On non-Windows platforms, if options.detached
is set to true
, the child\nprocess will be made the leader of a new process group and session. Child\nprocesses may continue running after the parent exits regardless of whether\nthey are detached or not. See setsid(2)
for more information.
By default, the parent will wait for the detached child to exit. To prevent the\nparent from waiting for a given subprocess
to exit, use the\nsubprocess.unref()
method. Doing so will cause the parent's event loop to not\ninclude the child in its reference count, allowing the parent to exit\nindependently of the child, unless there is an established IPC channel between\nthe child and the parent.
When using the detached
option to start a long-running process, the process\nwill not stay running in the background after the parent exits unless it is\nprovided with a stdio
configuration that is not connected to the parent.\nIf the parent's stdio
is inherited, the child will remain attached to the\ncontrolling terminal.
Example of a long-running process, by detaching and also ignoring its parent\nstdio
file descriptors, in order to ignore the parent's termination:
const { spawn } = require('node:child_process');\n\nconst subprocess = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: 'ignore',\n});\n\nsubprocess.unref();\n
\nAlternatively one can redirect the child process' output into files:
\nconst fs = require('node:fs');\nconst { spawn } = require('node:child_process');\nconst out = fs.openSync('./out.log', 'a');\nconst err = fs.openSync('./out.log', 'a');\n\nconst subprocess = spawn('prg', [], {\n detached: true,\n stdio: [ 'ignore', out, err ],\n});\n\nsubprocess.unref();\n
"
},
{
"textRaw": "`options.stdio`",
"name": "stdio",
"meta": {
"added": [
"v0.7.10"
],
"changes": [
{
"version": [
"v15.6.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/29412",
"description": "Added the `overlapped` stdio flag."
},
{
"version": "v3.3.1",
"pr-url": "https://github.com/nodejs/node/pull/2727",
"description": "The value `0` is now accepted as a file descriptor."
}
]
},
"desc": "The options.stdio
option is used to configure the pipes that are established\nbetween the parent and child process. By default, the child's stdin, stdout,\nand stderr are redirected to corresponding subprocess.stdin
,\nsubprocess.stdout
, and subprocess.stderr
streams on the\nChildProcess
object. This is equivalent to setting the options.stdio
\nequal to ['pipe', 'pipe', 'pipe']
.
For convenience, options.stdio
may be one of the following strings:
'pipe'
: equivalent to ['pipe', 'pipe', 'pipe']
(the default)'overlapped'
: equivalent to ['overlapped', 'overlapped', 'overlapped']
'ignore'
: equivalent to ['ignore', 'ignore', 'ignore']
'inherit'
: equivalent to ['inherit', 'inherit', 'inherit']
or [0, 1, 2]
Otherwise, the value of options.stdio
is an array where each index corresponds\nto an fd in the child. The fds 0, 1, and 2 correspond to stdin, stdout,\nand stderr, respectively. Additional fds can be specified to create additional\npipes between the parent and child. The value is one of the following:
'pipe'
: Create a pipe between the child process and the parent process.\nThe parent end of the pipe is exposed to the parent as a property on the\nchild_process
object as subprocess.stdio[fd]
. Pipes\ncreated for fds 0, 1, and 2 are also available as subprocess.stdin
,\nsubprocess.stdout
and subprocess.stderr
, respectively.\nThese are not actual Unix pipes and therefore the child process\ncan not use them by their descriptor files,\ne.g. /dev/fd/2
or /dev/stdout
.
'overlapped'
: Same as 'pipe'
except that the FILE_FLAG_OVERLAPPED
flag\nis set on the handle. This is necessary for overlapped I/O on the child\nprocess's stdio handles. See the\ndocs\nfor more details. This is exactly the same as 'pipe'
on non-Windows\nsystems.
'ipc'
: Create an IPC channel for passing messages/file descriptors\nbetween parent and child. A ChildProcess
may have at most one IPC\nstdio file descriptor. Setting this option enables the\nsubprocess.send()
method. If the child is a Node.js process, the\npresence of an IPC channel will enable process.send()
and\nprocess.disconnect()
methods, as well as 'disconnect'
and\n'message'
events within the child.
Accessing the IPC channel fd in any way other than process.send()
\nor using the IPC channel with a child process that is not a Node.js instance\nis not supported.
'ignore'
: Instructs Node.js to ignore the fd in the child. While Node.js\nwill always open fds 0, 1, and 2 for the processes it spawns, setting the fd\nto 'ignore'
will cause Node.js to open /dev/null
and attach it to the\nchild's fd.
'inherit'
: Pass through the corresponding stdio stream to/from the\nparent process. In the first three positions, this is equivalent to\nprocess.stdin
, process.stdout
, and process.stderr
, respectively. In\nany other position, equivalent to 'ignore'
.
<Stream> object: Share a readable or writable stream that refers to a tty,\nfile, socket, or a pipe with the child process. The stream's underlying\nfile descriptor is duplicated in the child process to the fd that\ncorresponds to the index in the stdio
array. The stream must have an\nunderlying descriptor (file streams do not start until the 'open'
event has\noccurred).
Positive integer: The integer value is interpreted as a file descriptor\nthat is open in the parent process. It is shared with the child\nprocess, similar to how <Stream> objects can be shared. Passing sockets\nis not supported on Windows.
\nnull
, undefined
: Use default value. For stdio fds 0, 1, and 2 (in other\nwords, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the\ndefault is 'ignore'
.
const { spawn } = require('node:child_process');\n\n// Child will use parent's stdios.\nspawn('prg', [], { stdio: 'inherit' });\n\n// Spawn child sharing only stderr.\nspawn('prg', [], { stdio: ['pipe', 'pipe', process.stderr] });\n\n// Open an extra fd=4, to interact with programs presenting a\n// startd-style interface.\nspawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });\n
\nIt is worth noting that when an IPC channel is established between the\nparent and child processes, and the child is a Node.js process, the child\nis launched with the IPC channel unreferenced (using unref()
) until the\nchild registers an event handler for the 'disconnect'
event\nor the 'message'
event. This allows the child to exit\nnormally without the process being held open by the open IPC channel.
See also: child_process.exec()
and child_process.fork()
.
The child_process.spawnSync()
, child_process.execSync()
, and\nchild_process.execFileSync()
methods are synchronous and will block the\nNode.js event loop, pausing execution of any additional code until the spawned\nprocess exits.
Blocking calls like these are mostly useful for simplifying general-purpose\nscripting tasks and for simplifying the loading/processing of application\nconfiguration at startup.
", "methods": [ { "textRaw": "`child_process.execFileSync(file[, args][, options])`", "type": "method", "name": "execFileSync", "meta": { "added": [ "v0.11.12" ], "changes": [ { "version": [ "v16.4.0", "v14.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/38862", "description": "The `cwd` option can be a WHATWG `URL` object using `file:` protocol." }, { "version": "v10.10.0", "pr-url": "https://github.com/nodejs/node/pull/22409", "description": "The `input` option can now be any `TypedArray` or a `DataView`." }, { "version": "v8.8.0", "pr-url": "https://github.com/nodejs/node/pull/15380", "description": "The `windowsHide` option is supported now." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/10653", "description": "The `input` option can now be a `Uint8Array`." }, { "version": [ "v6.2.1", "v4.5.0" ], "pr-url": "https://github.com/nodejs/node/pull/6939", "description": "The `encoding` option can now explicitly be set to `buffer`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer|string} The stdout from the command.", "name": "return", "type": "Buffer|string", "desc": "The stdout from the command." }, "params": [ { "textRaw": "`file` {string} The name or path of the executable file to run.", "name": "file", "type": "string", "desc": "The name or path of the executable file to run." }, { "textRaw": "`args` {string\\[]} List of string arguments.", "name": "args", "type": "string\\[]", "desc": "List of string arguments." }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cwd` {string|URL} Current working directory of the child process.", "name": "cwd", "type": "string|URL", "desc": "Current working directory of the child process." }, { "textRaw": "`input` {string|Buffer|TypedArray|DataView} The value which will be passed as stdin to the spawned process. If `stdio[0]` is set to `'pipe'`, Supplying this value will override `stdio[0]`.", "name": "input", "type": "string|Buffer|TypedArray|DataView", "desc": "The value which will be passed as stdin to the spawned process. If `stdio[0]` is set to `'pipe'`, Supplying this value will override `stdio[0]`." }, { "textRaw": "`stdio` {string|Array} Child's stdio configuration. `stderr` by default will be output to the parent process' stderr unless `stdio` is specified. **Default:** `'pipe'`.", "name": "stdio", "type": "string|Array", "default": "`'pipe'`", "desc": "Child's stdio configuration. `stderr` by default will be output to the parent process' stderr unless `stdio` is specified." }, { "textRaw": "`env` {Object} Environment key-value pairs. **Default:** `process.env`.", "name": "env", "type": "Object", "default": "`process.env`", "desc": "Environment key-value pairs." }, { "textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).", "name": "uid", "type": "number", "desc": "Sets the user identity of the process (see setuid(2))." }, { "textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).", "name": "gid", "type": "number", "desc": "Sets the group identity of the process (see setgid(2))." }, { "textRaw": "`timeout` {number} In milliseconds the maximum amount of time the process is allowed to run. **Default:** `undefined`.", "name": "timeout", "type": "number", "default": "`undefined`", "desc": "In milliseconds the maximum amount of time the process is allowed to run." }, { "textRaw": "`killSignal` {string|integer} The signal value to be used when the spawned process will be killed. **Default:** `'SIGTERM'`.", "name": "killSignal", "type": "string|integer", "default": "`'SIGTERM'`", "desc": "The signal value to be used when the spawned process will be killed." }, { "textRaw": "`maxBuffer` {number} Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated. See caveat at [`maxBuffer` and Unicode][]. **Default:** `1024 * 1024`.", "name": "maxBuffer", "type": "number", "default": "`1024 * 1024`", "desc": "Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated. See caveat at [`maxBuffer` and Unicode][]." }, { "textRaw": "`encoding` {string} The encoding used for all stdio inputs and outputs. **Default:** `'buffer'`.", "name": "encoding", "type": "string", "default": "`'buffer'`", "desc": "The encoding used for all stdio inputs and outputs." }, { "textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.", "name": "windowsHide", "type": "boolean", "default": "`false`", "desc": "Hide the subprocess console window that would normally be created on Windows systems." }, { "textRaw": "`shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]. **Default:** `false` (no shell).", "name": "shell", "type": "boolean|string", "default": "`false` (no shell)", "desc": "If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]." } ] } ] } ], "desc": "The child_process.execFileSync()
method is generally identical to\nchild_process.execFile()
with the exception that the method will not\nreturn until the child process has fully closed. When a timeout has been\nencountered and killSignal
is sent, the method won't return until the process\nhas completely exited.
If the child process intercepts and handles the SIGTERM
signal and\ndoes not exit, the parent process will still wait until the child process has\nexited.
If the process times out or has a non-zero exit code, this method will throw an\nError
that will include the full result of the underlying\nchild_process.spawnSync()
.
If the shell
option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
The child_process.execSync()
method is generally identical to\nchild_process.exec()
with the exception that the method will not return\nuntil the child process has fully closed. When a timeout has been encountered\nand killSignal
is sent, the method won't return until the process has\ncompletely exited. If the child process intercepts and handles the SIGTERM
\nsignal and doesn't exit, the parent process will wait until the child process\nhas exited.
If the process times out or has a non-zero exit code, this method will throw.\nThe Error
object will contain the entire result from\nchild_process.spawnSync()
.
Never pass unsanitized user input to this function. Any input containing shell\nmetacharacters may be used to trigger arbitrary command execution.
" }, { "textRaw": "`child_process.spawnSync(command[, args][, options])`", "type": "method", "name": "spawnSync", "meta": { "added": [ "v0.11.12" ], "changes": [ { "version": [ "v16.4.0", "v14.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/38862", "description": "The `cwd` option can be a WHATWG `URL` object using `file:` protocol." }, { "version": "v10.10.0", "pr-url": "https://github.com/nodejs/node/pull/22409", "description": "The `input` option can now be any `TypedArray` or a `DataView`." }, { "version": "v8.8.0", "pr-url": "https://github.com/nodejs/node/pull/15380", "description": "The `windowsHide` option is supported now." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/10653", "description": "The `input` option can now be a `Uint8Array`." }, { "version": [ "v6.2.1", "v4.5.0" ], "pr-url": "https://github.com/nodejs/node/pull/6939", "description": "The `encoding` option can now explicitly be set to `buffer`." }, { "version": "v5.7.0", "pr-url": "https://github.com/nodejs/node/pull/4598", "description": "The `shell` option is supported now." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object", "options": [ { "textRaw": "`pid` {number} Pid of the child process.", "name": "pid", "type": "number", "desc": "Pid of the child process." }, { "textRaw": "`output` {Array} Array of results from stdio output.", "name": "output", "type": "Array", "desc": "Array of results from stdio output." }, { "textRaw": "`stdout` {Buffer|string} The contents of `output[1]`.", "name": "stdout", "type": "Buffer|string", "desc": "The contents of `output[1]`." }, { "textRaw": "`stderr` {Buffer|string} The contents of `output[2]`.", "name": "stderr", "type": "Buffer|string", "desc": "The contents of `output[2]`." }, { "textRaw": "`status` {number|null} The exit code of the subprocess, or `null` if the subprocess terminated due to a signal.", "name": "status", "type": "number|null", "desc": "The exit code of the subprocess, or `null` if the subprocess terminated due to a signal." }, { "textRaw": "`signal` {string|null} The signal used to kill the subprocess, or `null` if the subprocess did not terminate due to a signal.", "name": "signal", "type": "string|null", "desc": "The signal used to kill the subprocess, or `null` if the subprocess did not terminate due to a signal." }, { "textRaw": "`error` {Error} The error object if the child process failed or timed out.", "name": "error", "type": "Error", "desc": "The error object if the child process failed or timed out." } ] }, "params": [ { "textRaw": "`command` {string} The command to run.", "name": "command", "type": "string", "desc": "The command to run." }, { "textRaw": "`args` {string\\[]} List of string arguments.", "name": "args", "type": "string\\[]", "desc": "List of string arguments." }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cwd` {string|URL} Current working directory of the child process.", "name": "cwd", "type": "string|URL", "desc": "Current working directory of the child process." }, { "textRaw": "`input` {string|Buffer|TypedArray|DataView} The value which will be passed as stdin to the spawned process. If `stdio[0]` is set to `'pipe'`, Supplying this value will override `stdio[0]`.", "name": "input", "type": "string|Buffer|TypedArray|DataView", "desc": "The value which will be passed as stdin to the spawned process. If `stdio[0]` is set to `'pipe'`, Supplying this value will override `stdio[0]`." }, { "textRaw": "`argv0` {string} Explicitly set the value of `argv[0]` sent to the child process. This will be set to `command` if not specified.", "name": "argv0", "type": "string", "desc": "Explicitly set the value of `argv[0]` sent to the child process. This will be set to `command` if not specified." }, { "textRaw": "`stdio` {string|Array} Child's stdio configuration. **Default:** `'pipe'`.", "name": "stdio", "type": "string|Array", "default": "`'pipe'`", "desc": "Child's stdio configuration." }, { "textRaw": "`env` {Object} Environment key-value pairs. **Default:** `process.env`.", "name": "env", "type": "Object", "default": "`process.env`", "desc": "Environment key-value pairs." }, { "textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).", "name": "uid", "type": "number", "desc": "Sets the user identity of the process (see setuid(2))." }, { "textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).", "name": "gid", "type": "number", "desc": "Sets the group identity of the process (see setgid(2))." }, { "textRaw": "`timeout` {number} In milliseconds the maximum amount of time the process is allowed to run. **Default:** `undefined`.", "name": "timeout", "type": "number", "default": "`undefined`", "desc": "In milliseconds the maximum amount of time the process is allowed to run." }, { "textRaw": "`killSignal` {string|integer} The signal value to be used when the spawned process will be killed. **Default:** `'SIGTERM'`.", "name": "killSignal", "type": "string|integer", "default": "`'SIGTERM'`", "desc": "The signal value to be used when the spawned process will be killed." }, { "textRaw": "`maxBuffer` {number} Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]. **Default:** `1024 * 1024`.", "name": "maxBuffer", "type": "number", "default": "`1024 * 1024`", "desc": "Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]." }, { "textRaw": "`encoding` {string} The encoding used for all stdio inputs and outputs. **Default:** `'buffer'`.", "name": "encoding", "type": "string", "default": "`'buffer'`", "desc": "The encoding used for all stdio inputs and outputs." }, { "textRaw": "`shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]. **Default:** `false` (no shell).", "name": "shell", "type": "boolean|string", "default": "`false` (no shell)", "desc": "If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on Unix, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell requirements][] and [Default Windows shell][]." }, { "textRaw": "`windowsVerbatimArguments` {boolean} No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to `true` automatically when `shell` is specified and is CMD. **Default:** `false`.", "name": "windowsVerbatimArguments", "type": "boolean", "default": "`false`", "desc": "No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to `true` automatically when `shell` is specified and is CMD." }, { "textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.", "name": "windowsHide", "type": "boolean", "default": "`false`", "desc": "Hide the subprocess console window that would normally be created on Windows systems." } ] } ] } ], "desc": "The child_process.spawnSync()
method is generally identical to\nchild_process.spawn()
with the exception that the function will not return\nuntil the child process has fully closed. When a timeout has been encountered\nand killSignal
is sent, the method won't return until the process has\ncompletely exited. If the process intercepts and handles the SIGTERM
signal\nand doesn't exit, the parent process will wait until the child process has\nexited.
If the shell
option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
The maxBuffer
option specifies the largest number of bytes allowed on stdout
\nor stderr
. If this value is exceeded, then the child process is terminated.\nThis impacts output that includes multibyte character encodings such as UTF-8 or\nUTF-16. For instance, console.log('中文测试')
will send 13 UTF-8 encoded bytes\nto stdout
although there are only 4 characters.
The shell should understand the -c
switch. If the shell is 'cmd.exe'
, it\nshould understand the /d /s /c
switches and command-line parsing should be\ncompatible.
Although Microsoft specifies %COMSPEC%
must contain the path to\n'cmd.exe'
in the root environment, child processes are not always subject to\nthe same requirement. Thus, in child_process
functions where a shell can be\nspawned, 'cmd.exe'
is used as a fallback if process.env.ComSpec
is\nunavailable.
Child processes support a serialization mechanism for IPC that is based on the\nserialization API of the node:v8
module, based on the\nHTML structured clone algorithm. This is generally more powerful and\nsupports more built-in JavaScript object types, such as BigInt
, Map
\nand Set
, ArrayBuffer
and TypedArray
, Buffer
, Error
, RegExp
etc.
However, this format is not a full superset of JSON, and e.g. properties set on\nobjects of such built-in types will not be passed on through the serialization\nstep. Additionally, performance may not be equivalent to that of JSON, depending\non the structure of the passed data.\nTherefore, this feature requires opting in by setting the\nserialization
option to 'advanced'
when calling child_process.spawn()
\nor child_process.fork()
.
Instances of the ChildProcess
represent spawned child processes.
Instances of ChildProcess
are not intended to be created directly. Rather,\nuse the child_process.spawn()
, child_process.exec()
,\nchild_process.execFile()
, or child_process.fork()
methods to create\ninstances of ChildProcess
.
The 'close'
event is emitted after a process has ended and the stdio\nstreams of a child process have been closed. This is distinct from the\n'exit'
event, since multiple processes might share the same stdio\nstreams. The 'close'
event will always emit after 'exit'
was\nalready emitted, or 'error'
if the child failed to spawn.
const { spawn } = require('node:child_process');\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process close all stdio with code ${code}`);\n});\n\nls.on('exit', (code) => {\n console.log(`child process exited with code ${code}`);\n});\n
"
},
{
"textRaw": "Event: `'disconnect'`",
"type": "event",
"name": "disconnect",
"meta": {
"added": [
"v0.7.2"
],
"changes": []
},
"params": [],
"desc": "The 'disconnect'
event is emitted after calling the\nsubprocess.disconnect()
method in parent process or\nprocess.disconnect()
in child process. After disconnecting it is no longer\npossible to send or receive messages, and the subprocess.connected
\nproperty is false
.
The 'error'
event is emitted whenever:
signal
option.The 'exit'
event may or may not fire after an error has occurred. When\nlistening to both the 'exit'
and 'error'
events, guard\nagainst accidentally invoking handler functions multiple times.
See also subprocess.kill()
and subprocess.send()
.
The 'exit'
event is emitted after the child process ends. If the process\nexited, code
is the final exit code of the process, otherwise null
. If the\nprocess terminated due to receipt of a signal, signal
is the string name of\nthe signal, otherwise null
. One of the two will always be non-null
.
When the 'exit'
event is triggered, child process stdio streams might still be\nopen.
Node.js establishes signal handlers for SIGINT
and SIGTERM
and Node.js\nprocesses will not terminate immediately due to receipt of those signals.\nRather, Node.js will perform a sequence of cleanup actions and then will\nre-raise the handled signal.
See waitpid(2)
.
The 'message'
event is triggered when a child process uses\nprocess.send()
to send messages.
The message goes through serialization and parsing. The resulting\nmessage might not be the same as what is originally sent.
\nIf the serialization
option was set to 'advanced'
used when spawning the\nchild process, the message
argument can contain data that JSON is not able\nto represent.\nSee Advanced serialization for more details.
The 'spawn'
event is emitted once the child process has spawned successfully.\nIf the child process does not spawn successfully, the 'spawn'
event is not\nemitted and the 'error'
event is emitted instead.
If emitted, the 'spawn'
event comes before all other events and before any\ndata is received via stdout
or stderr
.
The 'spawn'
event will fire regardless of whether an error occurs within\nthe spawned process. For example, if bash some-command
spawns successfully,\nthe 'spawn'
event will fire, though bash
may fail to spawn some-command
.\nThis caveat also applies when using { shell: true }
.
The subprocess.channel
property is a reference to the child's IPC channel. If\nno IPC channel exists, this property is undefined
.
This method makes the IPC channel keep the event loop of the parent process\nrunning if .unref()
has been called before.
This method makes the IPC channel not keep the event loop of the parent process\nrunning, and lets it finish even while the channel is open.
" } ] }, { "textRaw": "`connected` {boolean} Set to `false` after `subprocess.disconnect()` is called.", "type": "boolean", "name": "connected", "meta": { "added": [ "v0.7.2" ], "changes": [] }, "desc": "The subprocess.connected
property indicates whether it is still possible to\nsend and receive messages from a child process. When subprocess.connected
is\nfalse
, it is no longer possible to send or receive messages.
The subprocess.exitCode
property indicates the exit code of the child process.\nIf the child process is still running, the field will be null
.
The subprocess.killed
property indicates whether the child process\nsuccessfully received a signal from subprocess.kill()
. The killed
property\ndoes not indicate that the child process has been terminated.
Returns the process identifier (PID) of the child process. If the child process\nfails to spawn due to errors, then the value is undefined
and error
is\nemitted.
const { spawn } = require('node:child_process');\nconst grep = spawn('grep', ['ssh']);\n\nconsole.log(`Spawned child pid: ${grep.pid}`);\ngrep.stdin.end();\n
"
},
{
"textRaw": "`signalCode` {string|null}",
"type": "string|null",
"name": "signalCode",
"desc": "The subprocess.signalCode
property indicates the signal received by\nthe child process if any, else null
.
The subprocess.spawnargs
property represents the full list of command-line\narguments the child process was launched with.
The subprocess.spawnfile
property indicates the executable file name of\nthe child process that is launched.
For child_process.fork()
, its value will be equal to\nprocess.execPath
.\nFor child_process.spawn()
, its value will be the name of\nthe executable file.\nFor child_process.exec()
, its value will be the name of the shell\nin which the child process is launched.
A Readable Stream
that represents the child process's stderr
.
If the child was spawned with stdio[2]
set to anything other than 'pipe'
,\nthen this will be null
.
subprocess.stderr
is an alias for subprocess.stdio[2]
. Both properties will\nrefer to the same value.
The subprocess.stderr
property can be null
or undefined
\nif the child process could not be successfully spawned.
A Writable Stream
that represents the child process's stdin
.
If a child process waits to read all of its input, the child will not continue\nuntil this stream has been closed via end()
.
If the child was spawned with stdio[0]
set to anything other than 'pipe'
,\nthen this will be null
.
subprocess.stdin
is an alias for subprocess.stdio[0]
. Both properties will\nrefer to the same value.
The subprocess.stdin
property can be null
or undefined
\nif the child process could not be successfully spawned.
A sparse array of pipes to the child process, corresponding with positions in\nthe stdio
option passed to child_process.spawn()
that have been set\nto the value 'pipe'
. subprocess.stdio[0]
, subprocess.stdio[1]
, and\nsubprocess.stdio[2]
are also available as subprocess.stdin
,\nsubprocess.stdout
, and subprocess.stderr
, respectively.
In the following example, only the child's fd 1
(stdout) is configured as a\npipe, so only the parent's subprocess.stdio[1]
is a stream, all other values\nin the array are null
.
const assert = require('node:assert');\nconst fs = require('node:fs');\nconst child_process = require('node:child_process');\n\nconst subprocess = child_process.spawn('ls', {\n stdio: [\n 0, // Use parent's stdin for child.\n 'pipe', // Pipe child's stdout to parent.\n fs.openSync('err.out', 'w'), // Direct child's stderr to a file.\n ],\n});\n\nassert.strictEqual(subprocess.stdio[0], null);\nassert.strictEqual(subprocess.stdio[0], subprocess.stdin);\n\nassert(subprocess.stdout);\nassert.strictEqual(subprocess.stdio[1], subprocess.stdout);\n\nassert.strictEqual(subprocess.stdio[2], null);\nassert.strictEqual(subprocess.stdio[2], subprocess.stderr);\n
\nThe subprocess.stdio
property can be undefined
if the child process could\nnot be successfully spawned.
A Readable Stream
that represents the child process's stdout
.
If the child was spawned with stdio[1]
set to anything other than 'pipe'
,\nthen this will be null
.
subprocess.stdout
is an alias for subprocess.stdio[1]
. Both properties will\nrefer to the same value.
const { spawn } = require('node:child_process');\n\nconst subprocess = spawn('ls');\n\nsubprocess.stdout.on('data', (data) => {\n console.log(`Received chunk ${data}`);\n});\n
\nThe subprocess.stdout
property can be null
or undefined
\nif the child process could not be successfully spawned.
Closes the IPC channel between parent and child, allowing the child to exit\ngracefully once there are no other connections keeping it alive. After calling\nthis method the subprocess.connected
and process.connected
properties in\nboth the parent and child (respectively) will be set to false
, and it will be\nno longer possible to pass messages between the processes.
The 'disconnect'
event will be emitted when there are no messages in the\nprocess of being received. This will most often be triggered immediately after\ncalling subprocess.disconnect()
.
When the child process is a Node.js instance (e.g. spawned using\nchild_process.fork()
), the process.disconnect()
method can be invoked\nwithin the child process to close the IPC channel as well.
The subprocess.kill()
method sends a signal to the child process. If no\nargument is given, the process will be sent the 'SIGTERM'
signal. See\nsignal(7)
for a list of available signals. This function returns true
if\nkill(2)
succeeds, and false
otherwise.
const { spawn } = require('node:child_process');\nconst grep = spawn('grep', ['ssh']);\n\ngrep.on('close', (code, signal) => {\n console.log(\n `child process terminated due to receipt of signal ${signal}`);\n});\n\n// Send SIGHUP to process.\ngrep.kill('SIGHUP');\n
\nThe ChildProcess
object may emit an 'error'
event if the signal\ncannot be delivered. Sending a signal to a child process that has already exited\nis not an error but may have unforeseen consequences. Specifically, if the\nprocess identifier (PID) has been reassigned to another process, the signal will\nbe delivered to that process instead which can have unexpected results.
While the function is called kill
, the signal delivered to the child process\nmay not actually terminate the process.
See kill(2)
for reference.
On Windows, where POSIX signals do not exist, the signal
argument will be\nignored, and the process will be killed forcefully and abruptly (similar to\n'SIGKILL'
).\nSee Signal Events for more details.
On Linux, child processes of child processes will not be terminated\nwhen attempting to kill their parent. This is likely to happen when running a\nnew process in a shell or with the use of the shell
option of ChildProcess
:
'use strict';\nconst { spawn } = require('node:child_process');\n\nconst subprocess = spawn(\n 'sh',\n [\n '-c',\n `node -e \"setInterval(() => {\n console.log(process.pid, 'is alive')\n }, 500);\"`,\n ], {\n stdio: ['inherit', 'inherit', 'inherit'],\n },\n);\n\nsetTimeout(() => {\n subprocess.kill(); // Does not terminate the Node.js process in the shell.\n}, 2000);\n
"
},
{
"textRaw": "`subprocess[Symbol.dispose]()`",
"type": "method",
"name": "[Symbol.dispose]",
"meta": {
"added": [
"v20.5.0",
"v18.18.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": []
}
],
"desc": "Calls subprocess.kill()
with 'SIGTERM'
.
Calling subprocess.ref()
after making a call to subprocess.unref()
will\nrestore the removed reference count for the child process, forcing the parent\nto wait for the child to exit before exiting itself.
const { spawn } = require('node:child_process');\n\nconst subprocess = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: 'ignore',\n});\n\nsubprocess.unref();\nsubprocess.ref();\n
"
},
{
"textRaw": "`subprocess.send(message[, sendHandle[, options]][, callback])`",
"type": "method",
"name": "send",
"meta": {
"added": [
"v0.5.9"
],
"changes": [
{
"version": "v5.8.0",
"pr-url": "https://github.com/nodejs/node/pull/5283",
"description": "The `options` parameter, and the `keepOpen` option in particular, is supported now."
},
{
"version": "v5.0.0",
"pr-url": "https://github.com/nodejs/node/pull/3516",
"description": "This method returns a boolean for flow control now."
},
{
"version": "v4.0.0",
"pr-url": "https://github.com/nodejs/node/pull/2620",
"description": "The `callback` parameter is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`message` {Object}",
"name": "message",
"type": "Object"
},
{
"textRaw": "`sendHandle` {Handle}",
"name": "sendHandle",
"type": "Handle"
},
{
"textRaw": "`options` {Object} The `options` argument, if present, is an object used to parameterize the sending of certain types of handles. `options` supports the following properties:",
"name": "options",
"type": "Object",
"desc": "The `options` argument, if present, is an object used to parameterize the sending of certain types of handles. `options` supports the following properties:",
"options": [
{
"textRaw": "`keepOpen` {boolean} A value that can be used when passing instances of `net.Socket`. When `true`, the socket is kept open in the sending process. **Default:** `false`.",
"name": "keepOpen",
"type": "boolean",
"default": "`false`",
"desc": "A value that can be used when passing instances of `net.Socket`. When `true`, the socket is kept open in the sending process."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "When an IPC channel has been established between the parent and child (\ni.e. when using child_process.fork()
), the subprocess.send()
method can\nbe used to send messages to the child process. When the child process is a\nNode.js instance, these messages can be received via the 'message'
event.
The message goes through serialization and parsing. The resulting\nmessage might not be the same as what is originally sent.
\nFor example, in the parent script:
\nconst cp = require('node:child_process');\nconst n = cp.fork(`${__dirname}/sub.js`);\n\nn.on('message', (m) => {\n console.log('PARENT got message:', m);\n});\n\n// Causes the child to print: CHILD got message: { hello: 'world' }\nn.send({ hello: 'world' });\n
\nAnd then the child script, 'sub.js'
might look like this:
process.on('message', (m) => {\n console.log('CHILD got message:', m);\n});\n\n// Causes the parent to print: PARENT got message: { foo: 'bar', baz: null }\nprocess.send({ foo: 'bar', baz: NaN });\n
\nChild Node.js processes will have a process.send()
method of their own\nthat allows the child to send messages back to the parent.
There is a special case when sending a {cmd: 'NODE_foo'}
message. Messages\ncontaining a NODE_
prefix in the cmd
property are reserved for use within\nNode.js core and will not be emitted in the child's 'message'
\nevent. Rather, such messages are emitted using the\n'internalMessage'
event and are consumed internally by Node.js.\nApplications should avoid using such messages or listening for\n'internalMessage'
events as it is subject to change without notice.
The optional sendHandle
argument that may be passed to subprocess.send()
is\nfor passing a TCP server or socket object to the child process. The child will\nreceive the object as the second argument passed to the callback function\nregistered on the 'message'
event. Any data that is received\nand buffered in the socket will not be sent to the child.
The optional callback
is a function that is invoked after the message is\nsent but before the child may have received it. The function is called with a\nsingle argument: null
on success, or an Error
object on failure.
If no callback
function is provided and the message cannot be sent, an\n'error'
event will be emitted by the ChildProcess
object. This can\nhappen, for instance, when the child process has already exited.
subprocess.send()
will return false
if the channel has closed or when the\nbacklog of unsent messages exceeds a threshold that makes it unwise to send\nmore. Otherwise, the method returns true
. The callback
function can be\nused to implement flow control.
The sendHandle
argument can be used, for instance, to pass the handle of\na TCP server object to the child process as illustrated in the example below:
const subprocess = require('node:child_process').fork('subprocess.js');\n\n// Open up the server object and send the handle.\nconst server = require('node:net').createServer();\nserver.on('connection', (socket) => {\n socket.end('handled by parent');\n});\nserver.listen(1337, () => {\n subprocess.send('server', server);\n});\n
\nThe child would then receive the server object as:
\nprocess.on('message', (m, server) => {\n if (m === 'server') {\n server.on('connection', (socket) => {\n socket.end('handled by child');\n });\n }\n});\n
\nOnce the server is now shared between the parent and child, some connections\ncan be handled by the parent and some by the child.
\nWhile the example above uses a server created using the node:net
module,\nnode:dgram
module servers use exactly the same workflow with the exceptions of\nlistening on a 'message'
event instead of 'connection'
and using\nserver.bind()
instead of server.listen()
. This is, however, only\nsupported on Unix platforms.
Similarly, the sendHandler
argument can be used to pass the handle of a\nsocket to the child process. The example below spawns two children that each\nhandle connections with \"normal\" or \"special\" priority:
const { fork } = require('node:child_process');\nconst normal = fork('subprocess.js', ['normal']);\nconst special = fork('subprocess.js', ['special']);\n\n// Open up the server and send sockets to child. Use pauseOnConnect to prevent\n// the sockets from being read before they are sent to the child process.\nconst server = require('node:net').createServer({ pauseOnConnect: true });\nserver.on('connection', (socket) => {\n\n // If this is special priority...\n if (socket.remoteAddress === '74.125.127.100') {\n special.send('socket', socket);\n return;\n }\n // This is normal priority.\n normal.send('socket', socket);\n});\nserver.listen(1337);\n
\nThe subprocess.js
would receive the socket handle as the second argument\npassed to the event callback function:
process.on('message', (m, socket) => {\n if (m === 'socket') {\n if (socket) {\n // Check that the client socket exists.\n // It is possible for the socket to be closed between the time it is\n // sent and the time it is received in the child process.\n socket.end(`Request handled with ${process.argv[2]} priority`);\n }\n }\n});\n
\nDo not use .maxConnections
on a socket that has been passed to a subprocess.\nThe parent cannot track when the socket is destroyed.
Any 'message'
handlers in the subprocess should verify that socket
exists,\nas the connection may have been closed during the time it takes to send the\nconnection to the child.
By default, the parent will wait for the detached child to exit. To prevent the\nparent from waiting for a given subprocess
to exit, use the\nsubprocess.unref()
method. Doing so will cause the parent's event loop to not\ninclude the child in its reference count, allowing the parent to exit\nindependently of the child, unless there is an established IPC channel between\nthe child and the parent.
const { spawn } = require('node:child_process');\n\nconst subprocess = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: 'ignore',\n});\n\nsubprocess.unref();\n
"
}
]
}
],
"type": "module",
"displayName": "Child process",
"source": "doc/api/child_process.md"
},
{
"textRaw": "Cluster",
"name": "cluster",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/cluster.js
\nClusters of Node.js processes can be used to run multiple instances of Node.js\nthat can distribute workloads among their application threads. When process\nisolation is not needed, use the worker_threads
module instead, which\nallows running multiple application threads within a single Node.js instance.
The cluster module allows easy creation of child processes that all share\nserver ports.
\nimport cluster from 'node:cluster';\nimport http from 'node:http';\nimport { availableParallelism } from 'node:os';\nimport process from 'node:process';\n\nconst numCPUs = availableParallelism();\n\nif (cluster.isPrimary) {\n console.log(`Primary ${process.pid} is running`);\n\n // Fork workers.\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n cluster.on('exit', (worker, code, signal) => {\n console.log(`worker ${worker.process.pid} died`);\n });\n} else {\n // Workers can share any TCP connection\n // In this case it is an HTTP server\n http.createServer((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n }).listen(8000);\n\n console.log(`Worker ${process.pid} started`);\n}\n
\nconst cluster = require('node:cluster');\nconst http = require('node:http');\nconst numCPUs = require('node:os').availableParallelism();\nconst process = require('node:process');\n\nif (cluster.isPrimary) {\n console.log(`Primary ${process.pid} is running`);\n\n // Fork workers.\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n cluster.on('exit', (worker, code, signal) => {\n console.log(`worker ${worker.process.pid} died`);\n });\n} else {\n // Workers can share any TCP connection\n // In this case it is an HTTP server\n http.createServer((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n }).listen(8000);\n\n console.log(`Worker ${process.pid} started`);\n}\n
\nRunning Node.js will now share port 8000 between the workers:
\n$ node server.js\nPrimary 3596 is running\nWorker 4324 started\nWorker 4520 started\nWorker 6056 started\nWorker 5644 started\n
\nOn Windows, it is not yet possible to set up a named pipe server in a worker.
", "miscs": [ { "textRaw": "How it works", "name": "How it works", "type": "misc", "desc": "The worker processes are spawned using the child_process.fork()
method,\nso that they can communicate with the parent via IPC and pass server\nhandles back and forth.
The cluster module supports two methods of distributing incoming\nconnections.
\nThe first one (and the default one on all platforms except Windows)\nis the round-robin approach, where the primary process listens on a\nport, accepts new connections and distributes them across the workers\nin a round-robin fashion, with some built-in smarts to avoid\noverloading a worker process.
\nThe second approach is where the primary process creates the listen\nsocket and sends it to interested workers. The workers then accept\nincoming connections directly.
\nThe second approach should, in theory, give the best performance.\nIn practice however, distribution tends to be very unbalanced due\nto operating system scheduler vagaries. Loads have been observed\nwhere over 70% of all connections ended up in just two processes,\nout of a total of eight.
\nBecause server.listen()
hands off most of the work to the primary\nprocess, there are three cases where the behavior between a normal\nNode.js process and a cluster worker differs:
server.listen({fd: 7})
Because the message is passed to the primary,\nfile descriptor 7 in the parent will be listened on, and the\nhandle passed to the worker, rather than listening to the worker's\nidea of what the number 7 file descriptor references.server.listen(handle)
Listening on handles explicitly will cause\nthe worker to use the supplied handle, rather than talk to the primary\nprocess.server.listen(0)
Normally, this will cause servers to listen on a\nrandom port. However, in a cluster, each worker will receive the\nsame \"random\" port each time they do listen(0)
. In essence, the\nport is random the first time, but predictable thereafter. To listen\non a unique port, generate a port number based on the cluster worker ID.Node.js does not provide routing logic. It is therefore important to design an\napplication such that it does not rely too heavily on in-memory data objects for\nthings like sessions and login.
\nBecause workers are all separate processes, they can be killed or\nre-spawned depending on a program's needs, without affecting other\nworkers. As long as there are some workers still alive, the server will\ncontinue to accept connections. If no workers are alive, existing connections\nwill be dropped and new connections will be refused. Node.js does not\nautomatically manage the number of workers, however. It is the application's\nresponsibility to manage the worker pool based on its own needs.
\nAlthough a primary use case for the node:cluster
module is networking, it can\nalso be used for other use cases requiring worker processes.
A Worker
object contains all public information and method about a worker.\nIn the primary it can be obtained using cluster.workers
. In a worker\nit can be obtained using cluster.worker
.
Similar to the cluster.on('disconnect')
event, but specific to this worker.
cluster.fork().on('disconnect', () => {\n // Worker has disconnected\n});\n
"
},
{
"textRaw": "Event: `'error'`",
"type": "event",
"name": "error",
"meta": {
"added": [
"v0.7.3"
],
"changes": []
},
"params": [],
"desc": "This event is the same as the one provided by child_process.fork()
.
Within a worker, process.on('error')
may also be used.
Similar to the cluster.on('exit')
event, but specific to this worker.
import cluster from 'node:cluster';\n\nif (cluster.isPrimary) {\n const worker = cluster.fork();\n worker.on('exit', (code, signal) => {\n if (signal) {\n console.log(`worker was killed by signal: ${signal}`);\n } else if (code !== 0) {\n console.log(`worker exited with error code: ${code}`);\n } else {\n console.log('worker success!');\n }\n });\n}\n
\nconst cluster = require('node:cluster');\n\nif (cluster.isPrimary) {\n const worker = cluster.fork();\n worker.on('exit', (code, signal) => {\n if (signal) {\n console.log(`worker was killed by signal: ${signal}`);\n } else if (code !== 0) {\n console.log(`worker exited with error code: ${code}`);\n } else {\n console.log('worker success!');\n }\n });\n}\n
"
},
{
"textRaw": "Event: `'listening'`",
"type": "event",
"name": "listening",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"params": [
{
"textRaw": "`address` {Object}",
"name": "address",
"type": "Object"
}
],
"desc": "Similar to the cluster.on('listening')
event, but specific to this worker.
cluster.fork().on('listening', (address) => {\n // Worker is listening\n});\n
\ncluster.fork().on('listening', (address) => {\n // Worker is listening\n});\n
\nIt is not emitted in the worker.
" }, { "textRaw": "Event: `'message'`", "type": "event", "name": "message", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "params": [ { "textRaw": "`message` {Object}", "name": "message", "type": "Object" }, { "textRaw": "`handle` {undefined|Object}", "name": "handle", "type": "undefined|Object" } ], "desc": "Similar to the 'message'
event of cluster
, but specific to this worker.
Within a worker, process.on('message')
may also be used.
Here is an example using the message system. It keeps a count in the primary\nprocess of the number of HTTP requests received by the workers:
\nimport cluster from 'node:cluster';\nimport http from 'node:http';\nimport { availableParallelism } from 'node:os';\nimport process from 'node:process';\n\nif (cluster.isPrimary) {\n\n // Keep track of http requests\n let numReqs = 0;\n setInterval(() => {\n console.log(`numReqs = ${numReqs}`);\n }, 1000);\n\n // Count requests\n function messageHandler(msg) {\n if (msg.cmd && msg.cmd === 'notifyRequest') {\n numReqs += 1;\n }\n }\n\n // Start workers and listen for messages containing notifyRequest\n const numCPUs = availableParallelism();\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n for (const id in cluster.workers) {\n cluster.workers[id].on('message', messageHandler);\n }\n\n} else {\n\n // Worker processes have a http server.\n http.Server((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n\n // Notify primary about the request\n process.send({ cmd: 'notifyRequest' });\n }).listen(8000);\n}\n
\nconst cluster = require('node:cluster');\nconst http = require('node:http');\nconst process = require('node:process');\n\nif (cluster.isPrimary) {\n\n // Keep track of http requests\n let numReqs = 0;\n setInterval(() => {\n console.log(`numReqs = ${numReqs}`);\n }, 1000);\n\n // Count requests\n function messageHandler(msg) {\n if (msg.cmd && msg.cmd === 'notifyRequest') {\n numReqs += 1;\n }\n }\n\n // Start workers and listen for messages containing notifyRequest\n const numCPUs = require('node:os').availableParallelism();\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n for (const id in cluster.workers) {\n cluster.workers[id].on('message', messageHandler);\n }\n\n} else {\n\n // Worker processes have a http server.\n http.Server((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n\n // Notify primary about the request\n process.send({ cmd: 'notifyRequest' });\n }).listen(8000);\n}\n
"
},
{
"textRaw": "Event: `'online'`",
"type": "event",
"name": "online",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"params": [],
"desc": "Similar to the cluster.on('online')
event, but specific to this worker.
cluster.fork().on('online', () => {\n // Worker is online\n});\n
\nIt is not emitted in the worker.
" } ], "methods": [ { "textRaw": "`worker.disconnect()`", "type": "method", "name": "disconnect", "meta": { "added": [ "v0.7.7" ], "changes": [ { "version": "v7.3.0", "pr-url": "https://github.com/nodejs/node/pull/10019", "description": "This method now returns a reference to `worker`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {cluster.Worker} A reference to `worker`.", "name": "return", "type": "cluster.Worker", "desc": "A reference to `worker`." }, "params": [] } ], "desc": "In a worker, this function will close all servers, wait for the 'close'
event\non those servers, and then disconnect the IPC channel.
In the primary, an internal message is sent to the worker causing it to call\n.disconnect()
on itself.
Causes .exitedAfterDisconnect
to be set.
After a server is closed, it will no longer accept new connections,\nbut connections may be accepted by any other listening worker. Existing\nconnections will be allowed to close as usual. When no more connections exist,\nsee server.close()
, the IPC channel to the worker will close allowing it\nto die gracefully.
The above applies only to server connections, client connections are not\nautomatically closed by workers, and disconnect does not wait for them to close\nbefore exiting.
\nIn a worker, process.disconnect
exists, but it is not this function;\nit is disconnect()
.
Because long living server connections may block workers from disconnecting, it\nmay be useful to send a message, so application specific actions may be taken to\nclose them. It also may be useful to implement a timeout, killing a worker if\nthe 'disconnect'
event has not been emitted after some time.
if (cluster.isPrimary) {\n const worker = cluster.fork();\n let timeout;\n\n worker.on('listening', (address) => {\n worker.send('shutdown');\n worker.disconnect();\n timeout = setTimeout(() => {\n worker.kill();\n }, 2000);\n });\n\n worker.on('disconnect', () => {\n clearTimeout(timeout);\n });\n\n} else if (cluster.isWorker) {\n const net = require('node:net');\n const server = net.createServer((socket) => {\n // Connections never end\n });\n\n server.listen(8000);\n\n process.on('message', (msg) => {\n if (msg === 'shutdown') {\n // Initiate graceful close of any connections to server\n }\n });\n}\n
"
},
{
"textRaw": "`worker.isConnected()`",
"type": "method",
"name": "isConnected",
"meta": {
"added": [
"v0.11.14"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "This function returns true
if the worker is connected to its primary via its\nIPC channel, false
otherwise. A worker is connected to its primary after it\nhas been created. It is disconnected after the 'disconnect'
event is emitted.
This function returns true
if the worker's process has terminated (either\nbecause of exiting or being signaled). Otherwise, it returns false
.
import cluster from 'node:cluster';\nimport http from 'node:http';\nimport { availableParallelism } from 'node:os';\nimport process from 'node:process';\n\nconst numCPUs = availableParallelism();\n\nif (cluster.isPrimary) {\n console.log(`Primary ${process.pid} is running`);\n\n // Fork workers.\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n cluster.on('fork', (worker) => {\n console.log('worker is dead:', worker.isDead());\n });\n\n cluster.on('exit', (worker, code, signal) => {\n console.log('worker is dead:', worker.isDead());\n });\n} else {\n // Workers can share any TCP connection. In this case, it is an HTTP server.\n http.createServer((req, res) => {\n res.writeHead(200);\n res.end(`Current process\\n ${process.pid}`);\n process.kill(process.pid);\n }).listen(8000);\n}\n
\nconst cluster = require('node:cluster');\nconst http = require('node:http');\nconst numCPUs = require('node:os').availableParallelism();\nconst process = require('node:process');\n\nif (cluster.isPrimary) {\n console.log(`Primary ${process.pid} is running`);\n\n // Fork workers.\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n cluster.on('fork', (worker) => {\n console.log('worker is dead:', worker.isDead());\n });\n\n cluster.on('exit', (worker, code, signal) => {\n console.log('worker is dead:', worker.isDead());\n });\n} else {\n // Workers can share any TCP connection. In this case, it is an HTTP server.\n http.createServer((req, res) => {\n res.writeHead(200);\n res.end(`Current process\\n ${process.pid}`);\n process.kill(process.pid);\n }).listen(8000);\n}\n
"
},
{
"textRaw": "`worker.kill([signal])`",
"type": "method",
"name": "kill",
"meta": {
"added": [
"v0.9.12"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`signal` {string} Name of the kill signal to send to the worker process. **Default:** `'SIGTERM'`",
"name": "signal",
"type": "string",
"default": "`'SIGTERM'`",
"desc": "Name of the kill signal to send to the worker process."
}
]
}
],
"desc": "This function will kill the worker. In the primary worker, it does this by\ndisconnecting the worker.process
, and once disconnected, killing with\nsignal
. In the worker, it does it by killing the process with signal
.
The kill()
function kills the worker process without waiting for a graceful\ndisconnect, it has the same behavior as worker.process.kill()
.
This method is aliased as worker.destroy()
for backwards compatibility.
In a worker, process.kill()
exists, but it is not this function;\nit is kill()
.
Send a message to a worker or primary, optionally with a handle.
\nIn the primary, this sends a message to a specific worker. It is identical to\nChildProcess.send()
.
In a worker, this sends a message to the primary. It is identical to\nprocess.send()
.
This example will echo back all messages from the primary:
\nif (cluster.isPrimary) {\n const worker = cluster.fork();\n worker.send('hi there');\n\n} else if (cluster.isWorker) {\n process.on('message', (msg) => {\n process.send(msg);\n });\n}\n
"
}
],
"properties": [
{
"textRaw": "`exitedAfterDisconnect` {boolean}",
"type": "boolean",
"name": "exitedAfterDisconnect",
"meta": {
"added": [
"v6.0.0"
],
"changes": []
},
"desc": "This property is true
if the worker exited due to .disconnect()
.\nIf the worker exited any other way, it is false
. If the\nworker has not exited, it is undefined
.
The boolean worker.exitedAfterDisconnect
allows distinguishing between\nvoluntary and accidental exit, the primary may choose not to respawn a worker\nbased on this value.
cluster.on('exit', (worker, code, signal) => {\n if (worker.exitedAfterDisconnect === true) {\n console.log('Oh, it was just voluntary – no need to worry');\n }\n});\n\n// kill worker\nworker.kill();\n
"
},
{
"textRaw": "`id` {integer}",
"type": "integer",
"name": "id",
"meta": {
"added": [
"v0.8.0"
],
"changes": []
},
"desc": "Each new worker is given its own unique id, this id is stored in the\nid
.
While a worker is alive, this is the key that indexes it in\ncluster.workers
.
All workers are created using child_process.fork()
, the returned object\nfrom this function is stored as .process
. In a worker, the global process
\nis stored.
See: Child Process module.
\nWorkers will call process.exit(0)
if the 'disconnect'
event occurs\non process
and .exitedAfterDisconnect
is not true
. This protects against\naccidental disconnection.
Emitted after the worker IPC channel has disconnected. This can occur when a\nworker exits gracefully, is killed, or is disconnected manually (such as with\nworker.disconnect()
).
There may be a delay between the 'disconnect'
and 'exit'
events. These\nevents can be used to detect if the process is stuck in a cleanup or if there\nare long-living connections.
cluster.on('disconnect', (worker) => {\n console.log(`The worker #${worker.id} has disconnected`);\n});\n
"
},
{
"textRaw": "Event: `'exit'`",
"type": "event",
"name": "exit",
"meta": {
"added": [
"v0.7.9"
],
"changes": []
},
"params": [
{
"textRaw": "`worker` {cluster.Worker}",
"name": "worker",
"type": "cluster.Worker"
},
{
"textRaw": "`code` {number} The exit code, if it exited normally.",
"name": "code",
"type": "number",
"desc": "The exit code, if it exited normally."
},
{
"textRaw": "`signal` {string} The name of the signal (e.g. `'SIGHUP'`) that caused the process to be killed.",
"name": "signal",
"type": "string",
"desc": "The name of the signal (e.g. `'SIGHUP'`) that caused the process to be killed."
}
],
"desc": "When any of the workers die the cluster module will emit the 'exit'
event.
This can be used to restart the worker by calling .fork()
again.
cluster.on('exit', (worker, code, signal) => {\n console.log('worker %d died (%s). restarting...',\n worker.process.pid, signal || code);\n cluster.fork();\n});\n
\nSee child_process
event: 'exit'
.
When a new worker is forked the cluster module will emit a 'fork'
event.\nThis can be used to log worker activity, and create a custom timeout.
const timeouts = [];\nfunction errorMsg() {\n console.error('Something must be wrong with the connection ...');\n}\n\ncluster.on('fork', (worker) => {\n timeouts[worker.id] = setTimeout(errorMsg, 2000);\n});\ncluster.on('listening', (worker, address) => {\n clearTimeout(timeouts[worker.id]);\n});\ncluster.on('exit', (worker, code, signal) => {\n clearTimeout(timeouts[worker.id]);\n errorMsg();\n});\n
"
},
{
"textRaw": "Event: `'listening'`",
"type": "event",
"name": "listening",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"params": [
{
"textRaw": "`worker` {cluster.Worker}",
"name": "worker",
"type": "cluster.Worker"
},
{
"textRaw": "`address` {Object}",
"name": "address",
"type": "Object"
}
],
"desc": "After calling listen()
from a worker, when the 'listening'
event is emitted\non the server, a 'listening'
event will also be emitted on cluster
in the\nprimary.
The event handler is executed with two arguments, the worker
contains the\nworker object and the address
object contains the following connection\nproperties: address
, port
, and addressType
. This is very useful if the\nworker is listening on more than one address.
cluster.on('listening', (worker, address) => {\n console.log(\n `A worker is now connected to ${address.address}:${address.port}`);\n});\n
\nThe addressType
is one of:
4
(TCPv4)6
(TCPv6)-1
(Unix domain socket)'udp4'
or 'udp6'
(UDPv4 or UDPv6)Emitted when the cluster primary receives a message from any worker.
\nSee child_process
event: 'message'
.
After forking a new worker, the worker should respond with an online message.\nWhen the primary receives an online message it will emit this event.\nThe difference between 'fork'
and 'online'
is that fork is emitted when the\nprimary forks a worker, and 'online'
is emitted when the worker is running.
cluster.on('online', (worker) => {\n console.log('Yay, the worker responded after it was forked');\n});\n
"
},
{
"textRaw": "Event: `'setup'`",
"type": "event",
"name": "setup",
"meta": {
"added": [
"v0.7.1"
],
"changes": []
},
"params": [
{
"textRaw": "`settings` {Object}",
"name": "settings",
"type": "Object"
}
],
"desc": "Emitted every time .setupPrimary()
is called.
The settings
object is the cluster.settings
object at the time\n.setupPrimary()
was called and is advisory only, since multiple calls to\n.setupPrimary()
can be made in a single tick.
If accuracy is important, use cluster.settings
.
Calls .disconnect()
on each worker in cluster.workers
.
When they are disconnected all internal handles will be closed, allowing the\nprimary process to die gracefully if no other event is waiting.
\nThe method takes an optional callback argument which will be called when\nfinished.
\nThis can only be called from the primary process.
" }, { "textRaw": "`cluster.fork([env])`", "type": "method", "name": "fork", "meta": { "added": [ "v0.6.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {cluster.Worker}", "name": "return", "type": "cluster.Worker" }, "params": [ { "textRaw": "`env` {Object} Key/value pairs to add to worker process environment.", "name": "env", "type": "Object", "desc": "Key/value pairs to add to worker process environment." } ] } ], "desc": "Spawn a new worker process.
\nThis can only be called from the primary process.
" }, { "textRaw": "`cluster.setupMaster([settings])`", "type": "method", "name": "setupMaster", "meta": { "added": [ "v0.7.1" ], "deprecated": [ "v16.0.0" ], "changes": [ { "version": "v6.4.0", "pr-url": "https://github.com/nodejs/node/pull/7838", "description": "The `stdio` option is supported now." } ] }, "stability": 0, "stabilityText": "Deprecated", "signatures": [ { "params": [] } ], "desc": "Deprecated alias for .setupPrimary()
.
setupPrimary
is used to change the default 'fork' behavior. Once called,\nthe settings will be present in cluster.settings
.
Any settings changes only affect future calls to .fork()
and have no\neffect on workers that are already running.
The only attribute of a worker that cannot be set via .setupPrimary()
is\nthe env
passed to .fork()
.
The defaults above apply to the first call only; the defaults for later\ncalls are the current values at the time of cluster.setupPrimary()
is called.
import cluster from 'node:cluster';\n\ncluster.setupPrimary({\n exec: 'worker.js',\n args: ['--use', 'https'],\n silent: true,\n});\ncluster.fork(); // https worker\ncluster.setupPrimary({\n exec: 'worker.js',\n args: ['--use', 'http'],\n});\ncluster.fork(); // http worker\n
\nconst cluster = require('node:cluster');\n\ncluster.setupPrimary({\n exec: 'worker.js',\n args: ['--use', 'https'],\n silent: true,\n});\ncluster.fork(); // https worker\ncluster.setupPrimary({\n exec: 'worker.js',\n args: ['--use', 'http'],\n});\ncluster.fork(); // http worker\n
\nThis can only be called from the primary process.
" } ], "properties": [ { "textRaw": "`cluster.isMaster`", "name": "isMaster", "meta": { "added": [ "v0.8.1" ], "deprecated": [ "v16.0.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated", "desc": "Deprecated alias for cluster.isPrimary
.
True if the process is a primary. This is determined\nby the process.env.NODE_UNIQUE_ID
. If process.env.NODE_UNIQUE_ID
is\nundefined, then isPrimary
is true
.
True if the process is not a primary (it is the negation of cluster.isPrimary
).
The scheduling policy, either cluster.SCHED_RR
for round-robin or\ncluster.SCHED_NONE
to leave it to the operating system. This is a\nglobal setting and effectively frozen once either the first worker is spawned,\nor .setupPrimary()
is called, whichever comes first.
SCHED_RR
is the default on all operating systems except Windows.\nWindows will change to SCHED_RR
once libuv is able to effectively\ndistribute IOCP handles without incurring a large performance hit.
cluster.schedulingPolicy
can also be set through the\nNODE_CLUSTER_SCHED_POLICY
environment variable. Valid\nvalues are 'rr'
and 'none'
.
After calling .setupPrimary()
(or .fork()
) this settings object will\ncontain the settings, including the default values.
This object is not intended to be changed or set manually.
" }, { "textRaw": "`worker` {Object}", "type": "Object", "name": "worker", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "desc": "A reference to the current worker object. Not available in the primary process.
\nimport cluster from 'node:cluster';\n\nif (cluster.isPrimary) {\n console.log('I am primary');\n cluster.fork();\n cluster.fork();\n} else if (cluster.isWorker) {\n console.log(`I am worker #${cluster.worker.id}`);\n}\n
\nconst cluster = require('node:cluster');\n\nif (cluster.isPrimary) {\n console.log('I am primary');\n cluster.fork();\n cluster.fork();\n} else if (cluster.isWorker) {\n console.log(`I am worker #${cluster.worker.id}`);\n}\n
"
},
{
"textRaw": "`workers` {Object}",
"type": "Object",
"name": "workers",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"desc": "A hash that stores the active worker objects, keyed by id
field. This makes it\neasy to loop through all the workers. It is only available in the primary\nprocess.
A worker is removed from cluster.workers
after the worker has disconnected\nand exited. The order between these two events cannot be determined in\nadvance. However, it is guaranteed that the removal from the cluster.workers
\nlist happens before the last 'disconnect'
or 'exit'
event is emitted.
import cluster from 'node:cluster';\n\nfor (const worker of Object.values(cluster.workers)) {\n worker.send('big announcement to all workers');\n}\n
\nconst cluster = require('node:cluster');\n\nfor (const worker of Object.values(cluster.workers)) {\n worker.send('big announcement to all workers');\n}\n
"
}
],
"type": "module",
"displayName": "Cluster",
"source": "doc/api/cluster.md"
},
{
"textRaw": "Console",
"name": "console",
"introduced_in": "v0.10.13",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/console.js
\nThe node:console
module provides a simple debugging console that is similar to\nthe JavaScript console mechanism provided by web browsers.
The module exports two specific components:
\nConsole
class with methods such as console.log()
, console.error()
, and\nconsole.warn()
that can be used to write to any Node.js stream.console
instance configured to write to process.stdout
and\nprocess.stderr
. The global console
can be used without calling\nrequire('node:console')
.Warning: The global console object's methods are neither consistently\nsynchronous like the browser APIs they resemble, nor are they consistently\nasynchronous like all other Node.js streams. See the note on process I/O for\nmore information.
\nExample using the global console
:
console.log('hello world');\n// Prints: hello world, to stdout\nconsole.log('hello %s', 'world');\n// Prints: hello world, to stdout\nconsole.error(new Error('Whoops, something bad happened'));\n// Prints error message and stack trace to stderr:\n// Error: Whoops, something bad happened\n// at [eval]:5:15\n// at Script.runInThisContext (node:vm:132:18)\n// at Object.runInThisContext (node:vm:309:38)\n// at node:internal/process/execution:77:19\n// at [eval]-wrapper:6:22\n// at evalScript (node:internal/process/execution:76:60)\n// at node:internal/main/eval_string:23:3\n\nconst name = 'Will Robinson';\nconsole.warn(`Danger ${name}! Danger!`);\n// Prints: Danger Will Robinson! Danger!, to stderr\n
\nExample using the Console
class:
const out = getStreamSomehow();\nconst err = getStreamSomehow();\nconst myConsole = new console.Console(out, err);\n\nmyConsole.log('hello world');\n// Prints: hello world, to out\nmyConsole.log('hello %s', 'world');\n// Prints: hello world, to out\nmyConsole.error(new Error('Whoops, something bad happened'));\n// Prints: [Error: Whoops, something bad happened], to err\n\nconst name = 'Will Robinson';\nmyConsole.warn(`Danger ${name}! Danger!`);\n// Prints: Danger Will Robinson! Danger!, to err\n
",
"classes": [
{
"textRaw": "Class: `Console`",
"type": "class",
"name": "Console",
"meta": {
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/9744",
"description": "Errors that occur while writing to the underlying streams will now be ignored by default."
}
]
},
"desc": "The Console
class can be used to create a simple logger with configurable\noutput streams and can be accessed using either require('node:console').Console
\nor console.Console
(or their destructured counterparts):
const { Console } = require('node:console');\n
\nconst { Console } = console;\n
",
"methods": [
{
"textRaw": "`console.assert(value[, ...message])`",
"type": "method",
"name": "assert",
"meta": {
"added": [
"v0.1.101"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/17706",
"description": "The implementation is now spec compliant and does not throw anymore."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`value` {any} The value tested for being truthy.",
"name": "value",
"type": "any",
"desc": "The value tested for being truthy."
},
{
"textRaw": "`...message` {any} All arguments besides `value` are used as error message.",
"name": "...message",
"type": "any",
"desc": "All arguments besides `value` are used as error message."
}
]
}
],
"desc": "console.assert()
writes a message if value
is falsy or omitted. It only\nwrites a message and does not otherwise affect execution. The output always\nstarts with \"Assertion failed\"
. If provided, message
is formatted using\nutil.format()
.
If value
is truthy, nothing happens.
console.assert(true, 'does nothing');\n\nconsole.assert(false, 'Whoops %s work', 'didn\\'t');\n// Assertion failed: Whoops didn't work\n\nconsole.assert();\n// Assertion failed\n
"
},
{
"textRaw": "`console.clear()`",
"type": "method",
"name": "clear",
"meta": {
"added": [
"v8.3.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "When stdout
is a TTY, calling console.clear()
will attempt to clear the\nTTY. When stdout
is not a TTY, this method does nothing.
The specific operation of console.clear()
can vary across operating systems\nand terminal types. For most Linux operating systems, console.clear()
\noperates similarly to the clear
shell command. On Windows, console.clear()
\nwill clear only the output in the current terminal viewport for the Node.js\nbinary.
Maintains an internal counter specific to label
and outputs to stdout
the\nnumber of times console.count()
has been called with the given label
.
> console.count()\ndefault: 1\nundefined\n> console.count('default')\ndefault: 2\nundefined\n> console.count('abc')\nabc: 1\nundefined\n> console.count('xyz')\nxyz: 1\nundefined\n> console.count('abc')\nabc: 2\nundefined\n> console.count()\ndefault: 3\nundefined\n>\n
"
},
{
"textRaw": "`console.countReset([label])`",
"type": "method",
"name": "countReset",
"meta": {
"added": [
"v8.3.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`label` {string} The display label for the counter. **Default:** `'default'`.",
"name": "label",
"type": "string",
"default": "`'default'`",
"desc": "The display label for the counter."
}
]
}
],
"desc": "Resets the internal counter specific to label
.
> console.count('abc');\nabc: 1\nundefined\n> console.countReset('abc');\nundefined\n> console.count('abc');\nabc: 1\nundefined\n>\n
"
},
{
"textRaw": "`console.debug(data[, ...args])`",
"type": "method",
"name": "debug",
"meta": {
"added": [
"v8.0.0"
],
"changes": [
{
"version": "v8.10.0",
"pr-url": "https://github.com/nodejs/node/pull/17033",
"description": "`console.debug` is now an alias for `console.log`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`data` {any}",
"name": "data",
"type": "any"
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any"
}
]
}
],
"desc": "The console.debug()
function is an alias for console.log()
.
Uses util.inspect()
on obj
and prints the resulting string to stdout
.\nThis function bypasses any custom inspect()
function defined on obj
.
This method calls console.log()
passing it the arguments received.\nThis method does not produce any XML formatting.
Prints to stderr
with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to printf(3)
(the arguments are all passed to\nutil.format()
).
const code = 5;\nconsole.error('error #%d', code);\n// Prints: error #5, to stderr\nconsole.error('error', code);\n// Prints: error 5, to stderr\n
\nIf formatting elements (e.g. %d
) are not found in the first string then\nutil.inspect()
is called on each argument and the resulting string\nvalues are concatenated. See util.format()
for more information.
Increases indentation of subsequent lines by spaces for groupIndentation
\nlength.
If one or more label
s are provided, those are printed first without the\nadditional indentation.
An alias for console.group()
.
Decreases indentation of subsequent lines by spaces for groupIndentation
\nlength.
The console.info()
function is an alias for console.log()
.
Prints to stdout
with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to printf(3)
(the arguments are all passed to\nutil.format()
).
const count = 5;\nconsole.log('count: %d', count);\n// Prints: count: 5, to stdout\nconsole.log('count:', count);\n// Prints: count: 5, to stdout\n
\nSee util.format()
for more information.
Try to construct a table with the columns of the properties of tabularData
\n(or use properties
) and rows of tabularData
and log it. Falls back to just\nlogging the argument if it can't be parsed as tabular.
// These can't be parsed as tabular data\nconsole.table(Symbol());\n// Symbol()\n\nconsole.table(undefined);\n// undefined\n\nconsole.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }]);\n// ┌─────────┬─────┬─────┐\n// │ (index) │ a │ b │\n// ├─────────┼─────┼─────┤\n// │ 0 │ 1 │ 'Y' │\n// │ 1 │ 'Z' │ 2 │\n// └─────────┴─────┴─────┘\n\nconsole.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }], ['a']);\n// ┌─────────┬─────┐\n// │ (index) │ a │\n// ├─────────┼─────┤\n// │ 0 │ 1 │\n// │ 1 │ 'Z' │\n// └─────────┴─────┘\n
"
},
{
"textRaw": "`console.time([label])`",
"type": "method",
"name": "time",
"meta": {
"added": [
"v0.1.104"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`label` {string} **Default:** `'default'`",
"name": "label",
"type": "string",
"default": "`'default'`"
}
]
}
],
"desc": "Starts a timer that can be used to compute the duration of an operation. Timers\nare identified by a unique label
. Use the same label
when calling\nconsole.timeEnd()
to stop the timer and output the elapsed time in\nsuitable time units to stdout
. For example, if the elapsed\ntime is 3869ms, console.timeEnd()
displays \"3.869s\".
Stops a timer that was previously started by calling console.time()
and\nprints the result to stdout
:
console.time('bunch-of-stuff');\n// Do a bunch of stuff.\nconsole.timeEnd('bunch-of-stuff');\n// Prints: bunch-of-stuff: 225.438ms\n
"
},
{
"textRaw": "`console.timeLog([label][, ...data])`",
"type": "method",
"name": "timeLog",
"meta": {
"added": [
"v10.7.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`label` {string} **Default:** `'default'`",
"name": "label",
"type": "string",
"default": "`'default'`"
},
{
"textRaw": "`...data` {any}",
"name": "...data",
"type": "any"
}
]
}
],
"desc": "For a timer that was previously started by calling console.time()
, prints\nthe elapsed time and other data
arguments to stdout
:
console.time('process');\nconst value = expensiveProcess1(); // Returns 42\nconsole.timeLog('process', value);\n// Prints \"process: 365.227ms 42\".\ndoExpensiveProcess2(value);\nconsole.timeEnd('process');\n
"
},
{
"textRaw": "`console.trace([message][, ...args])`",
"type": "method",
"name": "trace",
"meta": {
"added": [
"v0.1.104"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`message` {any}",
"name": "message",
"type": "any"
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any"
}
]
}
],
"desc": "Prints to stderr
the string 'Trace: '
, followed by the util.format()
\nformatted message and stack trace to the current position in the code.
console.trace('Show me');\n// Prints: (stack trace will vary based on where trace is called)\n// Trace: Show me\n// at repl:2:9\n// at REPLServer.defaultEval (repl.js:248:27)\n// at bound (domain.js:287:14)\n// at REPLServer.runBound [as eval] (domain.js:300:12)\n// at REPLServer.<anonymous> (repl.js:412:12)\n// at emitOne (events.js:82:20)\n// at REPLServer.emit (events.js:169:7)\n// at REPLServer.Interface._onLine (readline.js:210:10)\n// at REPLServer.Interface._line (readline.js:549:8)\n// at REPLServer.Interface._ttyWrite (readline.js:826:14)\n
"
},
{
"textRaw": "`console.warn([data][, ...args])`",
"type": "method",
"name": "warn",
"meta": {
"added": [
"v0.1.100"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`data` {any}",
"name": "data",
"type": "any"
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any"
}
]
}
],
"desc": "The console.warn()
function is an alias for console.error()
.
Creates a new Console
with one or two writable stream instances. stdout
is a\nwritable stream to print log or info output. stderr
is used for warning or\nerror output. If stderr
is not provided, stdout
is used for stderr
.
const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// Custom simple logger\nconst logger = new Console({ stdout: output, stderr: errorOutput });\n// use it like console\nconst count = 5;\nlogger.log('count: %d', count);\n// In stdout.log: count 5\n
\nThe global console
is a special Console
whose output is sent to\nprocess.stdout
and process.stderr
. It is equivalent to calling:
new Console({ stdout: process.stdout, stderr: process.stderr });\n
"
},
{
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`stdout` {stream.Writable}",
"name": "stdout",
"type": "stream.Writable"
},
{
"textRaw": "`stderr` {stream.Writable}",
"name": "stderr",
"type": "stream.Writable"
},
{
"textRaw": "`ignoreErrors` {boolean} Ignore errors when writing to the underlying streams. **Default:** `true`.",
"name": "ignoreErrors",
"type": "boolean",
"default": "`true`",
"desc": "Ignore errors when writing to the underlying streams."
},
{
"textRaw": "`colorMode` {boolean|string} Set color support for this `Console` instance. Setting to `true` enables coloring while inspecting values. Setting to `false` disables coloring while inspecting values. Setting to `'auto'` makes color support depend on the value of the `isTTY` property and the value returned by `getColorDepth()` on the respective stream. This option can not be used, if `inspectOptions.colors` is set as well. **Default:** `'auto'`.",
"name": "colorMode",
"type": "boolean|string",
"default": "`'auto'`",
"desc": "Set color support for this `Console` instance. Setting to `true` enables coloring while inspecting values. Setting to `false` disables coloring while inspecting values. Setting to `'auto'` makes color support depend on the value of the `isTTY` property and the value returned by `getColorDepth()` on the respective stream. This option can not be used, if `inspectOptions.colors` is set as well."
},
{
"textRaw": "`inspectOptions` {Object} Specifies options that are passed along to [`util.inspect()`][].",
"name": "inspectOptions",
"type": "Object",
"desc": "Specifies options that are passed along to [`util.inspect()`][]."
},
{
"textRaw": "`groupIndentation` {number} Set group indentation. **Default:** `2`.",
"name": "groupIndentation",
"type": "number",
"default": "`2`",
"desc": "Set group indentation."
}
]
}
],
"desc": "Creates a new Console
with one or two writable stream instances. stdout
is a\nwritable stream to print log or info output. stderr
is used for warning or\nerror output. If stderr
is not provided, stdout
is used for stderr
.
const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// Custom simple logger\nconst logger = new Console({ stdout: output, stderr: errorOutput });\n// use it like console\nconst count = 5;\nlogger.log('count: %d', count);\n// In stdout.log: count 5\n
\nThe global console
is a special Console
whose output is sent to\nprocess.stdout
and process.stderr
. It is equivalent to calling:
new Console({ stdout: process.stdout, stderr: process.stderr });\n
"
}
]
}
],
"modules": [
{
"textRaw": "Inspector only methods",
"name": "inspector_only_methods",
"desc": "The following methods are exposed by the V8 engine in the general API but do\nnot display anything unless used in conjunction with the inspector\n(--inspect
flag).
This method does not display anything unless used in the inspector. The\nconsole.profile()
method starts a JavaScript CPU profile with an optional\nlabel until console.profileEnd()
is called. The profile is then added to\nthe Profile panel of the inspector.
console.profile('MyLabel');\n// Some code\nconsole.profileEnd('MyLabel');\n// Adds the profile 'MyLabel' to the Profiles panel of the inspector.\n
"
},
{
"textRaw": "`console.profileEnd([label])`",
"type": "method",
"name": "profileEnd",
"meta": {
"added": [
"v8.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`label` {string}",
"name": "label",
"type": "string"
}
]
}
],
"desc": "This method does not display anything unless used in the inspector. Stops the\ncurrent JavaScript CPU profiling session if one has been started and prints\nthe report to the Profiles panel of the inspector. See\nconsole.profile()
for an example.
If this method is called without a label, the most recently started profile is\nstopped.
" }, { "textRaw": "`console.timeStamp([label])`", "type": "method", "name": "timeStamp", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string}", "name": "label", "type": "string" } ] } ], "desc": "This method does not display anything unless used in the inspector. The\nconsole.timeStamp()
method adds an event with the label 'label'
to the\nTimeline panel of the inspector.
Source Code: lib/crypto.js
\nThe node:crypto
module provides cryptographic functionality that includes a\nset of wrappers for OpenSSL's hash, HMAC, cipher, decipher, sign, and verify\nfunctions.
const { createHmac } = await import('node:crypto');\n\nconst secret = 'abcdefg';\nconst hash = createHmac('sha256', secret)\n .update('I love cupcakes')\n .digest('hex');\nconsole.log(hash);\n// Prints:\n// c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e\n
\nconst { createHmac } = require('node:crypto');\n\nconst secret = 'abcdefg';\nconst hash = createHmac('sha256', secret)\n .update('I love cupcakes')\n .digest('hex');\nconsole.log(hash);\n// Prints:\n// c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e\n
",
"modules": [
{
"textRaw": "Determining if crypto support is unavailable",
"name": "determining_if_crypto_support_is_unavailable",
"desc": "It is possible for Node.js to be built without including support for the\nnode:crypto
module. In such cases, attempting to import
from crypto
or\ncalling require('node:crypto')
will result in an error being thrown.
When using CommonJS, the error thrown can be caught using try/catch:
\n\nlet crypto;\ntry {\n crypto = require('node:crypto');\n} catch (err) {\n console.error('crypto support is disabled!');\n}\n
\n\nWhen using the lexical ESM import
keyword, the error can only be\ncaught if a handler for process.on('uncaughtException')
is registered\nbefore any attempt to load the module is made (using, for instance,\na preload module).
When using ESM, if there is a chance that the code may be run on a build\nof Node.js where crypto support is not enabled, consider using the\nimport()
function instead of the lexical import
keyword:
let crypto;\ntry {\n crypto = await import('node:crypto');\n} catch (err) {\n console.error('crypto support is disabled!');\n}\n
",
"type": "module",
"displayName": "Determining if crypto support is unavailable"
},
{
"textRaw": "`node:crypto` module methods and properties",
"name": "`node:crypto`_module_methods_and_properties",
"properties": [
{
"textRaw": "`constants` {Object}",
"type": "Object",
"name": "constants",
"meta": {
"added": [
"v6.3.0"
],
"changes": []
},
"desc": "An object containing commonly used constants for crypto and security related\noperations. The specific constants currently defined are described in\nCrypto constants.
" }, { "textRaw": "`crypto.fips`", "name": "fips", "meta": { "added": [ "v6.0.0" ], "deprecated": [ "v10.0.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated", "desc": "Property for checking and controlling whether a FIPS compliant crypto provider\nis currently in use. Setting to true requires a FIPS build of Node.js.
\nThis property is deprecated. Please use crypto.setFips()
and\ncrypto.getFips()
instead.
A convenient alias for crypto.webcrypto.subtle
.
Type: <Crypto> An implementation of the Web Crypto API standard.
\nSee the Web Crypto API documentation for details.
" } ], "methods": [ { "textRaw": "`crypto.checkPrime(candidate[, options], callback)`", "type": "method", "name": "checkPrime", "meta": { "added": [ "v15.8.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." } ] }, "signatures": [ { "params": [ { "textRaw": "`candidate` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint} A possible prime encoded as a sequence of big endian octets of arbitrary length.", "name": "candidate", "type": "ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint", "desc": "A possible prime encoded as a sequence of big endian octets of arbitrary length." }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`checks` {number} The number of Miller-Rabin probabilistic primality iterations to perform. When the value is `0` (zero), a number of checks is used that yields a false positive rate of at most 2-64 for random input. Care must be used when selecting a number of checks. Refer to the OpenSSL documentation for the [`BN_is_prime_ex`][] function `nchecks` options for more details. **Default:** `0`", "name": "checks", "type": "number", "default": "`0`", "desc": "The number of Miller-Rabin probabilistic primality iterations to perform. When the value is `0` (zero), a number of checks is used that yields a false positive rate of at most 2-64 for random input. Care must be used when selecting a number of checks. Refer to the OpenSSL documentation for the [`BN_is_prime_ex`][] function `nchecks` options for more details." } ] }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error} Set to an {Error} object if an error occurred during check.", "name": "err", "type": "Error", "desc": "Set to an {Error} object if an error occurred during check." }, { "textRaw": "`result` {boolean} `true` if the candidate is a prime with an error probability less than `0.25 ** options.checks`.", "name": "result", "type": "boolean", "desc": "`true` if the candidate is a prime with an error probability less than `0.25 ** options.checks`." } ] } ] } ], "desc": "Checks the primality of the candidate
.
Checks the primality of the candidate
.
Creates and returns a Cipher
object that uses the given algorithm
and\npassword
.
The options
argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode (e.g. 'aes-128-ccm'
) is used. In that case, the\nauthTagLength
option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode. In GCM mode, the authTagLength
\noption is not required but can be used to set the length of the authentication\ntag that will be returned by getAuthTag()
and defaults to 16 bytes.\nFor chacha20-poly1305
, the authTagLength
option defaults to 16 bytes.
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms
will\ndisplay the available cipher algorithms.
The password
is used to derive the cipher key and initialization vector (IV).\nThe value must be either a 'latin1'
encoded string, a Buffer
, a\nTypedArray
, or a DataView
.
This function is semantically insecure for all\nsupported ciphers and fatally flawed for ciphers in counter mode (such as CTR,\nGCM, or CCM).
\nThe implementation of crypto.createCipher()
derives keys using the OpenSSL\nfunction EVP_BytesToKey
with the digest algorithm set to MD5, one\niteration, and no salt. The lack of salt allows dictionary attacks as the same\npassword always creates the same key. The low iteration count and\nnon-cryptographically secure hash algorithm allow passwords to be tested very\nrapidly.
In line with OpenSSL's recommendation to use a more modern algorithm instead of\nEVP_BytesToKey
it is recommended that developers derive a key and IV on\ntheir own using crypto.scrypt()
and to use crypto.createCipheriv()
\nto create the Cipher
object. Users should not use ciphers with counter mode\n(e.g. CTR, GCM, or CCM) in crypto.createCipher()
. A warning is emitted when\nthey are used in order to avoid the risk of IV reuse that causes\nvulnerabilities. For the case when IV is reused in GCM, see Nonce-Disrespecting\nAdversaries for details.
Creates and returns a Cipher
object, with the given algorithm
, key
and\ninitialization vector (iv
).
The options
argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode (e.g. 'aes-128-ccm'
) is used. In that case, the\nauthTagLength
option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode. In GCM mode, the authTagLength
\noption is not required but can be used to set the length of the authentication\ntag that will be returned by getAuthTag()
and defaults to 16 bytes.\nFor chacha20-poly1305
, the authTagLength
option defaults to 16 bytes.
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms
will\ndisplay the available cipher algorithms.
The key
is the raw key used by the algorithm
and iv
is an\ninitialization vector. Both arguments must be 'utf8'
encoded strings,\nBuffers, TypedArray
, or DataView
s. The key
may optionally be\na KeyObject
of type secret
. If the cipher does not need\nan initialization vector, iv
may be null
.
When passing strings for key
or iv
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
Initialization vectors should be unpredictable and unique; ideally, they will be\ncryptographically random. They do not have to be secret: IVs are typically just\nadded to ciphertext messages unencrypted. It may sound contradictory that\nsomething has to be unpredictable and unique, but does not have to be secret;\nremember that an attacker must not be able to predict ahead of time what a\ngiven IV will be.
" }, { "textRaw": "`crypto.createDecipher(algorithm, password[, options])`", "type": "method", "name": "createDecipher", "meta": { "added": [ "v0.1.94" ], "deprecated": [ "v10.0.0" ], "changes": [ { "version": [ "v17.9.0", "v16.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/42427", "description": "The `authTagLength` option is now optional when using the `chacha20-poly1305` cipher and defaults to 16 bytes." }, { "version": "v10.10.0", "pr-url": "https://github.com/nodejs/node/pull/21447", "description": "Ciphers in OCB mode are now supported." } ] }, "stability": 0, "stabilityText": "Deprecated: Use [`crypto.createDecipheriv()`][] instead.", "signatures": [ { "return": { "textRaw": "Returns: {Decipher}", "name": "return", "type": "Decipher" }, "params": [ { "textRaw": "`algorithm` {string}", "name": "algorithm", "type": "string" }, { "textRaw": "`password` {string|ArrayBuffer|Buffer|TypedArray|DataView}", "name": "password", "type": "string|ArrayBuffer|Buffer|TypedArray|DataView" }, { "textRaw": "`options` {Object} [`stream.transform` options][]", "name": "options", "type": "Object", "desc": "[`stream.transform` options][]" } ] } ], "desc": "Creates and returns a Decipher
object that uses the given algorithm
and\npassword
(key).
The options
argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode (e.g. 'aes-128-ccm'
) is used. In that case, the\nauthTagLength
option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode.\nFor chacha20-poly1305
, the authTagLength
option defaults to 16 bytes.
This function is semantically insecure for all\nsupported ciphers and fatally flawed for ciphers in counter mode (such as CTR,\nGCM, or CCM).
\nThe implementation of crypto.createDecipher()
derives keys using the OpenSSL\nfunction EVP_BytesToKey
with the digest algorithm set to MD5, one\niteration, and no salt. The lack of salt allows dictionary attacks as the same\npassword always creates the same key. The low iteration count and\nnon-cryptographically secure hash algorithm allow passwords to be tested very\nrapidly.
In line with OpenSSL's recommendation to use a more modern algorithm instead of\nEVP_BytesToKey
it is recommended that developers derive a key and IV on\ntheir own using crypto.scrypt()
and to use crypto.createDecipheriv()
\nto create the Decipher
object.
Creates and returns a Decipher
object that uses the given algorithm
, key
\nand initialization vector (iv
).
The options
argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode (e.g. 'aes-128-ccm'
) is used. In that case, the\nauthTagLength
option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode. In GCM mode, the authTagLength
\noption is not required but can be used to restrict accepted authentication tags\nto those with the specified length.\nFor chacha20-poly1305
, the authTagLength
option defaults to 16 bytes.
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms
will\ndisplay the available cipher algorithms.
The key
is the raw key used by the algorithm
and iv
is an\ninitialization vector. Both arguments must be 'utf8'
encoded strings,\nBuffers, TypedArray
, or DataView
s. The key
may optionally be\na KeyObject
of type secret
. If the cipher does not need\nan initialization vector, iv
may be null
.
When passing strings for key
or iv
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
Initialization vectors should be unpredictable and unique; ideally, they will be\ncryptographically random. They do not have to be secret: IVs are typically just\nadded to ciphertext messages unencrypted. It may sound contradictory that\nsomething has to be unpredictable and unique, but does not have to be secret;\nremember that an attacker must not be able to predict ahead of time what a given\nIV will be.
" }, { "textRaw": "`crypto.createDiffieHellman(prime[, primeEncoding][, generator][, generatorEncoding])`", "type": "method", "name": "createDiffieHellman", "meta": { "added": [ "v0.11.12" ], "changes": [ { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/12223", "description": "The `prime` argument can be any `TypedArray` or `DataView` now." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11983", "description": "The `prime` argument can be a `Uint8Array` now." }, { "version": "v6.0.0", "pr-url": "https://github.com/nodejs/node/pull/5522", "description": "The default for the encoding parameters changed from `binary` to `utf8`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {DiffieHellman}", "name": "return", "type": "DiffieHellman" }, "params": [ { "textRaw": "`prime` {string|ArrayBuffer|Buffer|TypedArray|DataView}", "name": "prime", "type": "string|ArrayBuffer|Buffer|TypedArray|DataView" }, { "textRaw": "`primeEncoding` {string} The [encoding][] of the `prime` string.", "name": "primeEncoding", "type": "string", "desc": "The [encoding][] of the `prime` string." }, { "textRaw": "`generator` {number|string|ArrayBuffer|Buffer|TypedArray|DataView} **Default:** `2`", "name": "generator", "type": "number|string|ArrayBuffer|Buffer|TypedArray|DataView", "default": "`2`" }, { "textRaw": "`generatorEncoding` {string} The [encoding][] of the `generator` string.", "name": "generatorEncoding", "type": "string", "desc": "The [encoding][] of the `generator` string." } ] } ], "desc": "Creates a DiffieHellman
key exchange object using the supplied prime
and an\noptional specific generator
.
The generator
argument can be a number, string, or Buffer
. If\ngenerator
is not specified, the value 2
is used.
If primeEncoding
is specified, prime
is expected to be a string; otherwise\na Buffer
, TypedArray
, or DataView
is expected.
If generatorEncoding
is specified, generator
is expected to be a string;\notherwise a number, Buffer
, TypedArray
, or DataView
is expected.
Creates a DiffieHellman
key exchange object and generates a prime of\nprimeLength
bits using an optional specific numeric generator
.\nIf generator
is not specified, the value 2
is used.
An alias for crypto.getDiffieHellman()
Creates an Elliptic Curve Diffie-Hellman (ECDH
) key exchange object using a\npredefined curve specified by the curveName
string. Use\ncrypto.getCurves()
to obtain a list of available curve names. On recent\nOpenSSL releases, openssl ecparam -list_curves
will also display the name\nand description of each available elliptic curve.
Creates and returns a Hash
object that can be used to generate hash digests\nusing the given algorithm
. Optional options
argument controls stream\nbehavior. For XOF hash functions such as 'shake256'
, the outputLength
option\ncan be used to specify the desired output length in bytes.
The algorithm
is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256'
, 'sha512'
, etc.\nOn recent releases of OpenSSL, openssl list -digest-algorithms
will\ndisplay the available digest algorithms.
Example: generating the sha256 sum of a file
\nimport {\n createReadStream,\n} from 'node:fs';\nimport { argv } from 'node:process';\nconst {\n createHash,\n} = await import('node:crypto');\n\nconst filename = argv[2];\n\nconst hash = createHash('sha256');\n\nconst input = createReadStream(filename);\ninput.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = input.read();\n if (data)\n hash.update(data);\n else {\n console.log(`${hash.digest('hex')} ${filename}`);\n }\n});\n
\nconst {\n createReadStream,\n} = require('node:fs');\nconst {\n createHash,\n} = require('node:crypto');\nconst { argv } = require('node:process');\n\nconst filename = argv[2];\n\nconst hash = createHash('sha256');\n\nconst input = createReadStream(filename);\ninput.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = input.read();\n if (data)\n hash.update(data);\n else {\n console.log(`${hash.digest('hex')} ${filename}`);\n }\n});\n
"
},
{
"textRaw": "`crypto.createHmac(algorithm, key[, options])`",
"type": "method",
"name": "createHmac",
"meta": {
"added": [
"v0.1.94"
],
"changes": [
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35093",
"description": "The key can also be an ArrayBuffer or CryptoKey. The encoding option was added. The key cannot contain more than 2 ** 32 - 1 bytes."
},
{
"version": "v11.6.0",
"pr-url": "https://github.com/nodejs/node/pull/24234",
"description": "The `key` argument can now be a `KeyObject`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Hmac}",
"name": "return",
"type": "Hmac"
},
"params": [
{
"textRaw": "`algorithm` {string}",
"name": "algorithm",
"type": "string"
},
{
"textRaw": "`key` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}",
"name": "key",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey"
},
{
"textRaw": "`options` {Object} [`stream.transform` options][]",
"name": "options",
"type": "Object",
"desc": "[`stream.transform` options][]",
"options": [
{
"textRaw": "`encoding` {string} The string encoding to use when `key` is a string.",
"name": "encoding",
"type": "string",
"desc": "The string encoding to use when `key` is a string."
}
]
}
]
}
],
"desc": "Creates and returns an Hmac
object that uses the given algorithm
and key
.\nOptional options
argument controls stream behavior.
The algorithm
is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256'
, 'sha512'
, etc.\nOn recent releases of OpenSSL, openssl list -digest-algorithms
will\ndisplay the available digest algorithms.
The key
is the HMAC key used to generate the cryptographic HMAC hash. If it is\na KeyObject
, its type must be secret
. If it is a string, please consider\ncaveats when using strings as inputs to cryptographic APIs. If it was\nobtained from a cryptographically secure source of entropy, such as\ncrypto.randomBytes()
or crypto.generateKey()
, its length should not\nexceed the block size of algorithm
(e.g., 512 bits for SHA-256).
Example: generating the sha256 HMAC of a file
\nimport {\n createReadStream,\n} from 'node:fs';\nimport { argv } from 'node:process';\nconst {\n createHmac,\n} = await import('node:crypto');\n\nconst filename = argv[2];\n\nconst hmac = createHmac('sha256', 'a secret');\n\nconst input = createReadStream(filename);\ninput.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = input.read();\n if (data)\n hmac.update(data);\n else {\n console.log(`${hmac.digest('hex')} ${filename}`);\n }\n});\n
\nconst {\n createReadStream,\n} = require('node:fs');\nconst {\n createHmac,\n} = require('node:crypto');\nconst { argv } = require('node:process');\n\nconst filename = argv[2];\n\nconst hmac = createHmac('sha256', 'a secret');\n\nconst input = createReadStream(filename);\ninput.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = input.read();\n if (data)\n hmac.update(data);\n else {\n console.log(`${hmac.digest('hex')} ${filename}`);\n }\n});\n
"
},
{
"textRaw": "`crypto.createPrivateKey(key)`",
"type": "method",
"name": "createPrivateKey",
"meta": {
"added": [
"v11.6.0"
],
"changes": [
{
"version": "v15.12.0",
"pr-url": "https://github.com/nodejs/node/pull/37254",
"description": "The key can also be a JWK object."
},
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35093",
"description": "The key can also be an ArrayBuffer. The encoding option was added. The key cannot contain more than 2 ** 32 - 1 bytes."
}
]
},
"signatures": [
{
"params": []
}
],
"desc": "\nkey
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>\nkey
: <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <Object> The key\nmaterial, either in PEM, DER, or JWK format.format
: <string> Must be 'pem'
, 'der'
, or ''jwk'
.\nDefault: 'pem'
.type
: <string> Must be 'pkcs1'
, 'pkcs8'
or 'sec1'
. This option is\nrequired only if the format
is 'der'
and ignored otherwise.passphrase
: <string> | <Buffer> The passphrase to use for decryption.encoding
: <string> The string encoding to use when key
is a string.Creates and returns a new key object containing a private key. If key
is a\nstring or Buffer
, format
is assumed to be 'pem'
; otherwise, key
\nmust be an object with the properties described above.
If the private key is encrypted, a passphrase
must be specified. The length\nof the passphrase is limited to 1024 bytes.
key
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>\nkey
: <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <Object> The key\nmaterial, either in PEM, DER, or JWK format.format
: <string> Must be 'pem'
, 'der'
, or 'jwk'
.\nDefault: 'pem'
.type
: <string> Must be 'pkcs1'
or 'spki'
. This option is\nrequired only if the format
is 'der'
and ignored otherwise.encoding
<string> The string encoding to use when key
is a string.Creates and returns a new key object containing a public key. If key
is a\nstring or Buffer
, format
is assumed to be 'pem'
; if key
is a KeyObject
\nwith type 'private'
, the public key is derived from the given private key;\notherwise, key
must be an object with the properties described above.
If the format is 'pem'
, the 'key'
may also be an X.509 certificate.
Because public keys can be derived from private keys, a private key may be\npassed instead of a public key. In that case, this function behaves as if\ncrypto.createPrivateKey()
had been called, except that the type of the\nreturned KeyObject
will be 'public'
and that the private key cannot be\nextracted from the returned KeyObject
. Similarly, if a KeyObject
with type\n'private'
is given, a new KeyObject
with type 'public'
will be returned\nand it will be impossible to extract the private key from the returned object.
Creates and returns a new key object containing a secret key for symmetric\nencryption or Hmac
.
Creates and returns a Sign
object that uses the given algorithm
. Use\ncrypto.getHashes()
to obtain the names of the available digest algorithms.\nOptional options
argument controls the stream.Writable
behavior.
In some cases, a Sign
instance can be created using the name of a signature\nalgorithm, such as 'RSA-SHA256'
, instead of a digest algorithm. This will use\nthe corresponding digest algorithm. This does not work for all signature\nalgorithms, such as 'ecdsa-with-SHA256'
, so it is best to always use digest\nalgorithm names.
Creates and returns a Verify
object that uses the given algorithm.\nUse crypto.getHashes()
to obtain an array of names of the available\nsigning algorithms. Optional options
argument controls the\nstream.Writable
behavior.
In some cases, a Verify
instance can be created using the name of a signature\nalgorithm, such as 'RSA-SHA256'
, instead of a digest algorithm. This will use\nthe corresponding digest algorithm. This does not work for all signature\nalgorithms, such as 'ecdsa-with-SHA256'
, so it is best to always use digest\nalgorithm names.
Computes the Diffie-Hellman secret based on a privateKey
and a publicKey
.\nBoth keys must have the same asymmetricKeyType
, which must be one of 'dh'
\n(for Diffie-Hellman), 'ec'
(for ECDH), 'x448'
, or 'x25519'
(for ECDH-ES).
A utility for creating one-shot hash digests of data. It can be faster than\nthe object-based crypto.createHash()
when hashing a smaller amount of data\n(<= 5MB) that's readily available. If the data can be big or if it is streamed,\nit's still recommended to use crypto.createHash()
instead.
The algorithm
is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256'
, 'sha512'
, etc.\nOn recent releases of OpenSSL, openssl list -digest-algorithms
will\ndisplay the available digest algorithms.
Example:
\nconst crypto = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\n// Hashing a string and return the result as a hex-encoded string.\nconst string = 'Node.js';\n// 10b3493287f831e81a438811a1ffba01f8cec4b7\nconsole.log(crypto.hash('sha1', string));\n\n// Encode a base64-encoded string into a Buffer, hash it and return\n// the result as a buffer.\nconst base64 = 'Tm9kZS5qcw==';\n// <Buffer 10 b3 49 32 87 f8 31 e8 1a 43 88 11 a1 ff ba 01 f8 ce c4 b7>\nconsole.log(crypto.hash('sha1', Buffer.from(base64, 'base64'), 'buffer'));\n
\nimport crypto from 'node:crypto';\nimport { Buffer } from 'node:buffer';\n\n// Hashing a string and return the result as a hex-encoded string.\nconst string = 'Node.js';\n// 10b3493287f831e81a438811a1ffba01f8cec4b7\nconsole.log(crypto.hash('sha1', string));\n\n// Encode a base64-encoded string into a Buffer, hash it and return\n// the result as a buffer.\nconst base64 = 'Tm9kZS5qcw==';\n// <Buffer 10 b3 49 32 87 f8 31 e8 1a 43 88 11 a1 ff ba 01 f8 ce c4 b7>\nconsole.log(crypto.hash('sha1', Buffer.from(base64, 'base64'), 'buffer'));\n
"
},
{
"textRaw": "`crypto.generateKey(type, options, callback)`",
"type": "method",
"name": "generateKey",
"meta": {
"added": [
"v15.0.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`type`: {string} The intended use of the generated secret key. Currently accepted values are `'hmac'` and `'aes'`.",
"name": "type",
"type": "string",
"desc": "The intended use of the generated secret key. Currently accepted values are `'hmac'` and `'aes'`."
},
{
"textRaw": "`options`: {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`length`: {number} The bit length of the key to generate. This must be a value greater than 0.",
"name": "length",
"type": "number",
"desc": "The bit length of the key to generate. This must be a value greater than 0.",
"options": [
{
"textRaw": "If `type` is `'hmac'`, the minimum is 8, and the maximum length is 231-1. If the value is not a multiple of 8, the generated key will be truncated to `Math.floor(length / 8)`.",
"name": "If",
"desc": "`type` is `'hmac'`, the minimum is 8, and the maximum length is 231-1. If the value is not a multiple of 8, the generated key will be truncated to `Math.floor(length / 8)`."
},
{
"textRaw": "If `type` is `'aes'`, the length must be one of `128`, `192`, or `256`.",
"name": "If",
"desc": "`type` is `'aes'`, the length must be one of `128`, `192`, or `256`."
}
]
}
]
},
{
"textRaw": "`callback`: {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err`: {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`key`: {KeyObject}",
"name": "key",
"type": "KeyObject"
}
]
}
]
}
],
"desc": "Asynchronously generates a new random secret key of the given length
. The\ntype
will determine which validations will be performed on the length
.
const {\n generateKey,\n} = await import('node:crypto');\n\ngenerateKey('hmac', { length: 512 }, (err, key) => {\n if (err) throw err;\n console.log(key.export().toString('hex')); // 46e..........620\n});\n
\nconst {\n generateKey,\n} = require('node:crypto');\n\ngenerateKey('hmac', { length: 512 }, (err, key) => {\n if (err) throw err;\n console.log(key.export().toString('hex')); // 46e..........620\n});\n
\nThe size of a generated HMAC key should not exceed the block size of the\nunderlying hash function. See crypto.createHmac()
for more information.
Generates a new asymmetric key pair of the given type
. RSA, RSA-PSS, DSA, EC,\nEd25519, Ed448, X25519, X448, and DH are currently supported.
If a publicKeyEncoding
or privateKeyEncoding
was specified, this function\nbehaves as if keyObject.export()
had been called on its result. Otherwise,\nthe respective part of the key is returned as a KeyObject
.
It is recommended to encode public keys as 'spki'
and private keys as\n'pkcs8'
with encryption for long-term storage:
const {\n generateKeyPair,\n} = await import('node:crypto');\n\ngenerateKeyPair('rsa', {\n modulusLength: 4096,\n publicKeyEncoding: {\n type: 'spki',\n format: 'pem',\n },\n privateKeyEncoding: {\n type: 'pkcs8',\n format: 'pem',\n cipher: 'aes-256-cbc',\n passphrase: 'top secret',\n },\n}, (err, publicKey, privateKey) => {\n // Handle errors and use the generated key pair.\n});\n
\nconst {\n generateKeyPair,\n} = require('node:crypto');\n\ngenerateKeyPair('rsa', {\n modulusLength: 4096,\n publicKeyEncoding: {\n type: 'spki',\n format: 'pem',\n },\n privateKeyEncoding: {\n type: 'pkcs8',\n format: 'pem',\n cipher: 'aes-256-cbc',\n passphrase: 'top secret',\n },\n}, (err, publicKey, privateKey) => {\n // Handle errors and use the generated key pair.\n});\n
\nOn completion, callback
will be called with err
set to undefined
and\npublicKey
/ privateKey
representing the generated key pair.
If this method is invoked as its util.promisify()
ed version, it returns\na Promise
for an Object
with publicKey
and privateKey
properties.
Generates a new asymmetric key pair of the given type
. RSA, RSA-PSS, DSA, EC,\nEd25519, Ed448, X25519, X448, and DH are currently supported.
If a publicKeyEncoding
or privateKeyEncoding
was specified, this function\nbehaves as if keyObject.export()
had been called on its result. Otherwise,\nthe respective part of the key is returned as a KeyObject
.
When encoding public keys, it is recommended to use 'spki'
. When encoding\nprivate keys, it is recommended to use 'pkcs8'
with a strong passphrase,\nand to keep the passphrase confidential.
const {\n generateKeyPairSync,\n} = await import('node:crypto');\n\nconst {\n publicKey,\n privateKey,\n} = generateKeyPairSync('rsa', {\n modulusLength: 4096,\n publicKeyEncoding: {\n type: 'spki',\n format: 'pem',\n },\n privateKeyEncoding: {\n type: 'pkcs8',\n format: 'pem',\n cipher: 'aes-256-cbc',\n passphrase: 'top secret',\n },\n});\n
\nconst {\n generateKeyPairSync,\n} = require('node:crypto');\n\nconst {\n publicKey,\n privateKey,\n} = generateKeyPairSync('rsa', {\n modulusLength: 4096,\n publicKeyEncoding: {\n type: 'spki',\n format: 'pem',\n },\n privateKeyEncoding: {\n type: 'pkcs8',\n format: 'pem',\n cipher: 'aes-256-cbc',\n passphrase: 'top secret',\n },\n});\n
\nThe return value { publicKey, privateKey }
represents the generated key pair.\nWhen PEM encoding was selected, the respective key will be a string, otherwise\nit will be a buffer containing the data encoded as DER.
Synchronously generates a new random secret key of the given length
. The\ntype
will determine which validations will be performed on the length
.
const {\n generateKeySync,\n} = await import('node:crypto');\n\nconst key = generateKeySync('hmac', { length: 512 });\nconsole.log(key.export().toString('hex')); // e89..........41e\n
\nconst {\n generateKeySync,\n} = require('node:crypto');\n\nconst key = generateKeySync('hmac', { length: 512 });\nconsole.log(key.export().toString('hex')); // e89..........41e\n
\nThe size of a generated HMAC key should not exceed the block size of the\nunderlying hash function. See crypto.createHmac()
for more information.
Generates a pseudorandom prime of size
bits.
If options.safe
is true
, the prime will be a safe prime -- that is,\n(prime - 1) / 2
will also be a prime.
The options.add
and options.rem
parameters can be used to enforce additional\nrequirements, e.g., for Diffie-Hellman:
options.add
and options.rem
are both set, the prime will satisfy the\ncondition that prime % add = rem
.options.add
is set and options.safe
is not true
, the prime will\nsatisfy the condition that prime % add = 1
.options.add
is set and options.safe
is set to true
, the prime\nwill instead satisfy the condition that prime % add = 3
. This is necessary\nbecause prime % add = 1
for options.add > 2
would contradict the condition\nenforced by options.safe
.options.rem
is ignored if options.add
is not given.Both options.add
and options.rem
must be encoded as big-endian sequences\nif given as an ArrayBuffer
, SharedArrayBuffer
, TypedArray
, Buffer
, or\nDataView
.
By default, the prime is encoded as a big-endian sequence of octets\nin an <ArrayBuffer>. If the bigint
option is true
, then a <bigint>\nis provided.
Generates a pseudorandom prime of size
bits.
If options.safe
is true
, the prime will be a safe prime -- that is,\n(prime - 1) / 2
will also be a prime.
The options.add
and options.rem
parameters can be used to enforce additional\nrequirements, e.g., for Diffie-Hellman:
options.add
and options.rem
are both set, the prime will satisfy the\ncondition that prime % add = rem
.options.add
is set and options.safe
is not true
, the prime will\nsatisfy the condition that prime % add = 1
.options.add
is set and options.safe
is set to true
, the prime\nwill instead satisfy the condition that prime % add = 3
. This is necessary\nbecause prime % add = 1
for options.add > 2
would contradict the condition\nenforced by options.safe
.options.rem
is ignored if options.add
is not given.Both options.add
and options.rem
must be encoded as big-endian sequences\nif given as an ArrayBuffer
, SharedArrayBuffer
, TypedArray
, Buffer
, or\nDataView
.
By default, the prime is encoded as a big-endian sequence of octets\nin an <ArrayBuffer>. If the bigint
option is true
, then a <bigint>\nis provided.
Returns information about a given cipher.
\nSome ciphers accept variable length keys and initialization vectors. By default,\nthe crypto.getCipherInfo()
method will return the default values for these\nciphers. To test if a given key length or iv length is acceptable for given\ncipher, use the keyLength
and ivLength
options. If the given values are\nunacceptable, undefined
will be returned.
const {\n getCiphers,\n} = await import('node:crypto');\n\nconsole.log(getCiphers()); // ['aes-128-cbc', 'aes-128-ccm', ...]\n
\nconst {\n getCiphers,\n} = require('node:crypto');\n\nconsole.log(getCiphers()); // ['aes-128-cbc', 'aes-128-ccm', ...]\n
"
},
{
"textRaw": "`crypto.getCurves()`",
"type": "method",
"name": "getCurves",
"meta": {
"added": [
"v2.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string\\[]} An array with the names of the supported elliptic curves.",
"name": "return",
"type": "string\\[]",
"desc": "An array with the names of the supported elliptic curves."
},
"params": []
}
],
"desc": "const {\n getCurves,\n} = await import('node:crypto');\n\nconsole.log(getCurves()); // ['Oakley-EC2N-3', 'Oakley-EC2N-4', ...]\n
\nconst {\n getCurves,\n} = require('node:crypto');\n\nconsole.log(getCurves()); // ['Oakley-EC2N-3', 'Oakley-EC2N-4', ...]\n
"
},
{
"textRaw": "`crypto.getDiffieHellman(groupName)`",
"type": "method",
"name": "getDiffieHellman",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {DiffieHellmanGroup}",
"name": "return",
"type": "DiffieHellmanGroup"
},
"params": [
{
"textRaw": "`groupName` {string}",
"name": "groupName",
"type": "string"
}
]
}
],
"desc": "Creates a predefined DiffieHellmanGroup
key exchange object. The\nsupported groups are listed in the documentation for DiffieHellmanGroup
.
The returned object mimics the interface of objects created by\ncrypto.createDiffieHellman()
, but will not allow changing\nthe keys (with diffieHellman.setPublicKey()
, for example). The\nadvantage of using this method is that the parties do not have to\ngenerate nor exchange a group modulus beforehand, saving both processor\nand communication time.
Example (obtaining a shared secret):
\nconst {\n getDiffieHellman,\n} = await import('node:crypto');\nconst alice = getDiffieHellman('modp14');\nconst bob = getDiffieHellman('modp14');\n\nalice.generateKeys();\nbob.generateKeys();\n\nconst aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n/* aliceSecret and bobSecret should be the same */\nconsole.log(aliceSecret === bobSecret);\n
\nconst {\n getDiffieHellman,\n} = require('node:crypto');\n\nconst alice = getDiffieHellman('modp14');\nconst bob = getDiffieHellman('modp14');\n\nalice.generateKeys();\nbob.generateKeys();\n\nconst aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n/* aliceSecret and bobSecret should be the same */\nconsole.log(aliceSecret === bobSecret);\n
"
},
{
"textRaw": "`crypto.getFips()`",
"type": "method",
"name": "getFips",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number} `1` if and only if a FIPS compliant crypto provider is currently in use, `0` otherwise. A future semver-major release may change the return type of this API to a {boolean}.",
"name": "return",
"type": "number",
"desc": "`1` if and only if a FIPS compliant crypto provider is currently in use, `0` otherwise. A future semver-major release may change the return type of this API to a {boolean}."
},
"params": []
}
]
},
{
"textRaw": "`crypto.getHashes()`",
"type": "method",
"name": "getHashes",
"meta": {
"added": [
"v0.9.3"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string\\[]} An array of the names of the supported hash algorithms, such as `'RSA-SHA256'`. Hash algorithms are also called \"digest\" algorithms.",
"name": "return",
"type": "string\\[]",
"desc": "An array of the names of the supported hash algorithms, such as `'RSA-SHA256'`. Hash algorithms are also called \"digest\" algorithms."
},
"params": []
}
],
"desc": "const {\n getHashes,\n} = await import('node:crypto');\n\nconsole.log(getHashes()); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]\n
\nconst {\n getHashes,\n} = require('node:crypto');\n\nconsole.log(getHashes()); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]\n
"
},
{
"textRaw": "`crypto.getRandomValues(typedArray)`",
"type": "method",
"name": "getRandomValues",
"meta": {
"added": [
"v17.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer|TypedArray|DataView|ArrayBuffer} Returns `typedArray`.",
"name": "return",
"type": "Buffer|TypedArray|DataView|ArrayBuffer",
"desc": "Returns `typedArray`."
},
"params": [
{
"textRaw": "`typedArray` {Buffer|TypedArray|DataView|ArrayBuffer}",
"name": "typedArray",
"type": "Buffer|TypedArray|DataView|ArrayBuffer"
}
]
}
],
"desc": "A convenient alias for crypto.webcrypto.getRandomValues()
. This\nimplementation is not compliant with the Web Crypto spec, to write\nweb-compatible code use crypto.webcrypto.getRandomValues()
instead.
HKDF is a simple key derivation function defined in RFC 5869. The given ikm
,\nsalt
and info
are used with the digest
to derive a key of keylen
bytes.
The supplied callback
function is called with two arguments: err
and\nderivedKey
. If an errors occurs while deriving the key, err
will be set;\notherwise err
will be null
. The successfully generated derivedKey
will\nbe passed to the callback as an <ArrayBuffer>. An error will be thrown if any\nof the input arguments specify invalid values or types.
import { Buffer } from 'node:buffer';\nconst {\n hkdf,\n} = await import('node:crypto');\n\nhkdf('sha512', 'key', 'salt', 'info', 64, (err, derivedKey) => {\n if (err) throw err;\n console.log(Buffer.from(derivedKey).toString('hex')); // '24156e2...5391653'\n});\n
\nconst {\n hkdf,\n} = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nhkdf('sha512', 'key', 'salt', 'info', 64, (err, derivedKey) => {\n if (err) throw err;\n console.log(Buffer.from(derivedKey).toString('hex')); // '24156e2...5391653'\n});\n
"
},
{
"textRaw": "`crypto.hkdfSync(digest, ikm, salt, info, keylen)`",
"type": "method",
"name": "hkdfSync",
"meta": {
"added": [
"v15.0.0"
],
"changes": [
{
"version": [
"v18.8.0",
"v16.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/44201",
"description": "The input keying material can now be zero-length."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {ArrayBuffer}",
"name": "return",
"type": "ArrayBuffer"
},
"params": [
{
"textRaw": "`digest` {string} The digest algorithm to use.",
"name": "digest",
"type": "string",
"desc": "The digest algorithm to use."
},
{
"textRaw": "`ikm` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject} The input keying material. Must be provided but can be zero-length.",
"name": "ikm",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject",
"desc": "The input keying material. Must be provided but can be zero-length."
},
{
"textRaw": "`salt` {string|ArrayBuffer|Buffer|TypedArray|DataView} The salt value. Must be provided but can be zero-length.",
"name": "salt",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView",
"desc": "The salt value. Must be provided but can be zero-length."
},
{
"textRaw": "`info` {string|ArrayBuffer|Buffer|TypedArray|DataView} Additional info value. Must be provided but can be zero-length, and cannot be more than 1024 bytes.",
"name": "info",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView",
"desc": "Additional info value. Must be provided but can be zero-length, and cannot be more than 1024 bytes."
},
{
"textRaw": "`keylen` {number} The length of the key to generate. Must be greater than 0. The maximum allowable value is `255` times the number of bytes produced by the selected digest function (e.g. `sha512` generates 64-byte hashes, making the maximum HKDF output 16320 bytes).",
"name": "keylen",
"type": "number",
"desc": "The length of the key to generate. Must be greater than 0. The maximum allowable value is `255` times the number of bytes produced by the selected digest function (e.g. `sha512` generates 64-byte hashes, making the maximum HKDF output 16320 bytes)."
}
]
}
],
"desc": "Provides a synchronous HKDF key derivation function as defined in RFC 5869. The\ngiven ikm
, salt
and info
are used with the digest
to derive a key of\nkeylen
bytes.
The successfully generated derivedKey
will be returned as an <ArrayBuffer>.
An error will be thrown if any of the input arguments specify invalid values or\ntypes, or if the derived key cannot be generated.
\nimport { Buffer } from 'node:buffer';\nconst {\n hkdfSync,\n} = await import('node:crypto');\n\nconst derivedKey = hkdfSync('sha512', 'key', 'salt', 'info', 64);\nconsole.log(Buffer.from(derivedKey).toString('hex')); // '24156e2...5391653'\n
\nconst {\n hkdfSync,\n} = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst derivedKey = hkdfSync('sha512', 'key', 'salt', 'info', 64);\nconsole.log(Buffer.from(derivedKey).toString('hex')); // '24156e2...5391653'\n
"
},
{
"textRaw": "`crypto.pbkdf2(password, salt, iterations, keylen, digest, callback)`",
"type": "method",
"name": "pbkdf2",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35093",
"description": "The password and salt arguments can also be ArrayBuffer instances."
},
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/30578",
"description": "The `iterations` parameter is now restricted to positive values. Earlier releases treated other values as one."
},
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/11305",
"description": "The `digest` parameter is always required now."
},
{
"version": "v6.0.0",
"pr-url": "https://github.com/nodejs/node/pull/4047",
"description": "Calling this function without passing the `digest` parameter is deprecated now and will emit a warning."
},
{
"version": "v6.0.0",
"pr-url": "https://github.com/nodejs/node/pull/5522",
"description": "The default encoding for `password` if it is a string changed from `binary` to `utf8`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`password` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "password",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`salt` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "salt",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`iterations` {number}",
"name": "iterations",
"type": "number"
},
{
"textRaw": "`keylen` {number}",
"name": "keylen",
"type": "number"
},
{
"textRaw": "`digest` {string}",
"name": "digest",
"type": "string"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`derivedKey` {Buffer}",
"name": "derivedKey",
"type": "Buffer"
}
]
}
]
}
],
"desc": "Provides an asynchronous Password-Based Key Derivation Function 2 (PBKDF2)\nimplementation. A selected HMAC digest algorithm specified by digest
is\napplied to derive a key of the requested byte length (keylen
) from the\npassword
, salt
and iterations
.
The supplied callback
function is called with two arguments: err
and\nderivedKey
. If an error occurs while deriving the key, err
will be set;\notherwise err
will be null
. By default, the successfully generated\nderivedKey
will be passed to the callback as a Buffer
. An error will be\nthrown if any of the input arguments specify invalid values or types.
The iterations
argument must be a number set as high as possible. The\nhigher the number of iterations, the more secure the derived key will be,\nbut will take a longer amount of time to complete.
The salt
should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
When passing strings for password
or salt
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
const {\n pbkdf2,\n} = await import('node:crypto');\n\npbkdf2('secret', 'salt', 100000, 64, 'sha512', (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\n
\nconst {\n pbkdf2,\n} = require('node:crypto');\n\npbkdf2('secret', 'salt', 100000, 64, 'sha512', (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\n
\nAn array of supported digest functions can be retrieved using\ncrypto.getHashes()
.
This API uses libuv's threadpool, which can have surprising and\nnegative performance implications for some applications; see the\nUV_THREADPOOL_SIZE
documentation for more information.
Provides a synchronous Password-Based Key Derivation Function 2 (PBKDF2)\nimplementation. A selected HMAC digest algorithm specified by digest
is\napplied to derive a key of the requested byte length (keylen
) from the\npassword
, salt
and iterations
.
If an error occurs an Error
will be thrown, otherwise the derived key will be\nreturned as a Buffer
.
The iterations
argument must be a number set as high as possible. The\nhigher the number of iterations, the more secure the derived key will be,\nbut will take a longer amount of time to complete.
The salt
should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
When passing strings for password
or salt
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
const {\n pbkdf2Sync,\n} = await import('node:crypto');\n\nconst key = pbkdf2Sync('secret', 'salt', 100000, 64, 'sha512');\nconsole.log(key.toString('hex')); // '3745e48...08d59ae'\n
\nconst {\n pbkdf2Sync,\n} = require('node:crypto');\n\nconst key = pbkdf2Sync('secret', 'salt', 100000, 64, 'sha512');\nconsole.log(key.toString('hex')); // '3745e48...08d59ae'\n
\nAn array of supported digest functions can be retrieved using\ncrypto.getHashes()
.
privateKey
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\noaepHash
<string> The hash function to use for OAEP padding and MGF1.\nDefault: 'sha1'
oaepLabel
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> The label to\nuse for OAEP padding. If not specified, no label is used.padding
<crypto.constants> An optional padding value defined in\ncrypto.constants
, which may be: crypto.constants.RSA_NO_PADDING
,\ncrypto.constants.RSA_PKCS1_PADDING
, or\ncrypto.constants.RSA_PKCS1_OAEP_PADDING
.buffer
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>Buffer
with the decrypted content.Decrypts buffer
with privateKey
. buffer
was previously encrypted using\nthe corresponding public key, for example using crypto.publicEncrypt()
.
If privateKey
is not a KeyObject
, this function behaves as if\nprivateKey
had been passed to crypto.createPrivateKey()
. If it is an\nobject, the padding
property can be passed. Otherwise, this function uses\nRSA_PKCS1_OAEP_PADDING
.
Using crypto.constants.RSA_PKCS1_PADDING
in crypto.privateDecrypt()
\nrequires OpenSSL to support implicit rejection (rsa_pkcs1_implicit_rejection
).\nIf the version of OpenSSL used by Node.js does not support this feature,\nattempting to use RSA_PKCS1_PADDING
will fail.
privateKey
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\nkey
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\nA PEM encoded private key.passphrase
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> An optional\npassphrase for the private key.padding
<crypto.constants> An optional padding value defined in\ncrypto.constants
, which may be: crypto.constants.RSA_NO_PADDING
or\ncrypto.constants.RSA_PKCS1_PADDING
.encoding
<string> The string encoding to use when buffer
, key
,\nor passphrase
are strings.buffer
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>Buffer
with the encrypted content.Encrypts buffer
with privateKey
. The returned data can be decrypted using\nthe corresponding public key, for example using crypto.publicDecrypt()
.
If privateKey
is not a KeyObject
, this function behaves as if\nprivateKey
had been passed to crypto.createPrivateKey()
. If it is an\nobject, the padding
property can be passed. Otherwise, this function uses\nRSA_PKCS1_PADDING
.
key
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\npassphrase
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> An optional\npassphrase for the private key.padding
<crypto.constants> An optional padding value defined in\ncrypto.constants
, which may be: crypto.constants.RSA_NO_PADDING
or\ncrypto.constants.RSA_PKCS1_PADDING
.encoding
<string> The string encoding to use when buffer
, key
,\nor passphrase
are strings.buffer
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>Buffer
with the decrypted content.Decrypts buffer
with key
.buffer
was previously encrypted using\nthe corresponding private key, for example using crypto.privateEncrypt()
.
If key
is not a KeyObject
, this function behaves as if\nkey
had been passed to crypto.createPublicKey()
. If it is an\nobject, the padding
property can be passed. Otherwise, this function uses\nRSA_PKCS1_PADDING
.
Because RSA public keys can be derived from private keys, a private key may\nbe passed instead of a public key.
" }, { "textRaw": "`crypto.publicEncrypt(key, buffer)`", "type": "method", "name": "publicEncrypt", "meta": { "added": [ "v0.11.14" ], "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/35093", "description": "Added string, ArrayBuffer, and CryptoKey as allowable key types. The oaepLabel and passphrase can be ArrayBuffers. The buffer can be a string or ArrayBuffer. All types that accept buffers are limited to a maximum of 2 ** 31 - 1 bytes." }, { "version": "v12.11.0", "pr-url": "https://github.com/nodejs/node/pull/29489", "description": "The `oaepLabel` option was added." }, { "version": "v12.9.0", "pr-url": "https://github.com/nodejs/node/pull/28335", "description": "The `oaepHash` option was added." }, { "version": "v11.6.0", "pr-url": "https://github.com/nodejs/node/pull/24234", "description": "This function now supports key objects." } ] }, "signatures": [ { "params": [] } ], "desc": "\nkey
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\nkey
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\nA PEM encoded public or private key, <KeyObject>, or <CryptoKey>.oaepHash
<string> The hash function to use for OAEP padding and MGF1.\nDefault: 'sha1'
oaepLabel
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> The label to\nuse for OAEP padding. If not specified, no label is used.passphrase
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> An optional\npassphrase for the private key.padding
<crypto.constants> An optional padding value defined in\ncrypto.constants
, which may be: crypto.constants.RSA_NO_PADDING
,\ncrypto.constants.RSA_PKCS1_PADDING
, or\ncrypto.constants.RSA_PKCS1_OAEP_PADDING
.encoding
<string> The string encoding to use when buffer
, key
,\noaepLabel
, or passphrase
are strings.buffer
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>Buffer
with the encrypted content.Encrypts the content of buffer
with key
and returns a new\nBuffer
with encrypted content. The returned data can be decrypted using\nthe corresponding private key, for example using crypto.privateDecrypt()
.
If key
is not a KeyObject
, this function behaves as if\nkey
had been passed to crypto.createPublicKey()
. If it is an\nobject, the padding
property can be passed. Otherwise, this function uses\nRSA_PKCS1_OAEP_PADDING
.
Because RSA public keys can be derived from private keys, a private key may\nbe passed instead of a public key.
" }, { "textRaw": "`crypto.randomBytes(size[, callback])`", "type": "method", "name": "randomBytes", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/16454", "description": "Passing `null` as the `callback` argument now throws `ERR_INVALID_CALLBACK`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer} if the `callback` function is not provided.", "name": "return", "type": "Buffer", "desc": "if the `callback` function is not provided." }, "params": [ { "textRaw": "`size` {number} The number of bytes to generate. The `size` must not be larger than `2**31 - 1`.", "name": "size", "type": "number", "desc": "The number of bytes to generate. The `size` must not be larger than `2**31 - 1`." }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`buf` {Buffer}", "name": "buf", "type": "Buffer" } ] } ] } ], "desc": "Generates cryptographically strong pseudorandom data. The size
argument\nis a number indicating the number of bytes to generate.
If a callback
function is provided, the bytes are generated asynchronously\nand the callback
function is invoked with two arguments: err
and buf
.\nIf an error occurs, err
will be an Error
object; otherwise it is null
. The\nbuf
argument is a Buffer
containing the generated bytes.
// Asynchronous\nconst {\n randomBytes,\n} = await import('node:crypto');\n\nrandomBytes(256, (err, buf) => {\n if (err) throw err;\n console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);\n});\n
\n// Asynchronous\nconst {\n randomBytes,\n} = require('node:crypto');\n\nrandomBytes(256, (err, buf) => {\n if (err) throw err;\n console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);\n});\n
\nIf the callback
function is not provided, the random bytes are generated\nsynchronously and returned as a Buffer
. An error will be thrown if\nthere is a problem generating the bytes.
// Synchronous\nconst {\n randomBytes,\n} = await import('node:crypto');\n\nconst buf = randomBytes(256);\nconsole.log(\n `${buf.length} bytes of random data: ${buf.toString('hex')}`);\n
\n// Synchronous\nconst {\n randomBytes,\n} = require('node:crypto');\n\nconst buf = randomBytes(256);\nconsole.log(\n `${buf.length} bytes of random data: ${buf.toString('hex')}`);\n
\nThe crypto.randomBytes()
method will not complete until there is\nsufficient entropy available.\nThis should normally never take longer than a few milliseconds. The only time\nwhen generating the random bytes may conceivably block for a longer period of\ntime is right after boot, when the whole system is still low on entropy.
This API uses libuv's threadpool, which can have surprising and\nnegative performance implications for some applications; see the\nUV_THREADPOOL_SIZE
documentation for more information.
The asynchronous version of crypto.randomBytes()
is carried out in a single\nthreadpool request. To minimize threadpool task length variation, partition\nlarge randomBytes
requests when doing so as part of fulfilling a client\nrequest.
Synchronous version of crypto.randomFill()
.
import { Buffer } from 'node:buffer';\nconst { randomFillSync } = await import('node:crypto');\n\nconst buf = Buffer.alloc(10);\nconsole.log(randomFillSync(buf).toString('hex'));\n\nrandomFillSync(buf, 5);\nconsole.log(buf.toString('hex'));\n\n// The above is equivalent to the following:\nrandomFillSync(buf, 5, 5);\nconsole.log(buf.toString('hex'));\n
\nconst { randomFillSync } = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.alloc(10);\nconsole.log(randomFillSync(buf).toString('hex'));\n\nrandomFillSync(buf, 5);\nconsole.log(buf.toString('hex'));\n\n// The above is equivalent to the following:\nrandomFillSync(buf, 5, 5);\nconsole.log(buf.toString('hex'));\n
\nAny ArrayBuffer
, TypedArray
or DataView
instance may be passed as\nbuffer
.
import { Buffer } from 'node:buffer';\nconst { randomFillSync } = await import('node:crypto');\n\nconst a = new Uint32Array(10);\nconsole.log(Buffer.from(randomFillSync(a).buffer,\n a.byteOffset, a.byteLength).toString('hex'));\n\nconst b = new DataView(new ArrayBuffer(10));\nconsole.log(Buffer.from(randomFillSync(b).buffer,\n b.byteOffset, b.byteLength).toString('hex'));\n\nconst c = new ArrayBuffer(10);\nconsole.log(Buffer.from(randomFillSync(c)).toString('hex'));\n
\nconst { randomFillSync } = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst a = new Uint32Array(10);\nconsole.log(Buffer.from(randomFillSync(a).buffer,\n a.byteOffset, a.byteLength).toString('hex'));\n\nconst b = new DataView(new ArrayBuffer(10));\nconsole.log(Buffer.from(randomFillSync(b).buffer,\n b.byteOffset, b.byteLength).toString('hex'));\n\nconst c = new ArrayBuffer(10);\nconsole.log(Buffer.from(randomFillSync(c)).toString('hex'));\n
"
},
{
"textRaw": "`crypto.randomFill(buffer[, offset][, size], callback)`",
"type": "method",
"name": "randomFill",
"meta": {
"added": [
"v7.10.0",
"v6.13.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v9.0.0",
"pr-url": "https://github.com/nodejs/node/pull/15231",
"description": "The `buffer` argument may be any `TypedArray` or `DataView`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`buffer` {ArrayBuffer|Buffer|TypedArray|DataView} Must be supplied. The size of the provided `buffer` must not be larger than `2**31 - 1`.",
"name": "buffer",
"type": "ArrayBuffer|Buffer|TypedArray|DataView",
"desc": "Must be supplied. The size of the provided `buffer` must not be larger than `2**31 - 1`."
},
{
"textRaw": "`offset` {number} **Default:** `0`",
"name": "offset",
"type": "number",
"default": "`0`"
},
{
"textRaw": "`size` {number} **Default:** `buffer.length - offset`. The `size` must not be larger than `2**31 - 1`.",
"name": "size",
"type": "number",
"default": "`buffer.length - offset`. The `size` must not be larger than `2**31 - 1`"
},
{
"textRaw": "`callback` {Function} `function(err, buf) {}`.",
"name": "callback",
"type": "Function",
"desc": "`function(err, buf) {}`."
}
]
}
],
"desc": "This function is similar to crypto.randomBytes()
but requires the first\nargument to be a Buffer
that will be filled. It also\nrequires that a callback is passed in.
If the callback
function is not provided, an error will be thrown.
import { Buffer } from 'node:buffer';\nconst { randomFill } = await import('node:crypto');\n\nconst buf = Buffer.alloc(10);\nrandomFill(buf, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\nrandomFill(buf, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\n// The above is equivalent to the following:\nrandomFill(buf, 5, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n
\nconst { randomFill } = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst buf = Buffer.alloc(10);\nrandomFill(buf, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\nrandomFill(buf, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\n// The above is equivalent to the following:\nrandomFill(buf, 5, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n
\nAny ArrayBuffer
, TypedArray
, or DataView
instance may be passed as\nbuffer
.
While this includes instances of Float32Array
and Float64Array
, this\nfunction should not be used to generate random floating-point numbers. The\nresult may contain +Infinity
, -Infinity
, and NaN
, and even if the array\ncontains finite numbers only, they are not drawn from a uniform random\ndistribution and have no meaningful lower or upper bounds.
import { Buffer } from 'node:buffer';\nconst { randomFill } = await import('node:crypto');\n\nconst a = new Uint32Array(10);\nrandomFill(a, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n\nconst b = new DataView(new ArrayBuffer(10));\nrandomFill(b, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n\nconst c = new ArrayBuffer(10);\nrandomFill(c, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf).toString('hex'));\n});\n
\nconst { randomFill } = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst a = new Uint32Array(10);\nrandomFill(a, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n\nconst b = new DataView(new ArrayBuffer(10));\nrandomFill(b, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n\nconst c = new ArrayBuffer(10);\nrandomFill(c, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf).toString('hex'));\n});\n
\nThis API uses libuv's threadpool, which can have surprising and\nnegative performance implications for some applications; see the\nUV_THREADPOOL_SIZE
documentation for more information.
The asynchronous version of crypto.randomFill()
is carried out in a single\nthreadpool request. To minimize threadpool task length variation, partition\nlarge randomFill
requests when doing so as part of fulfilling a client\nrequest.
Return a random integer n
such that min <= n < max
. This\nimplementation avoids modulo bias.
The range (max - min
) must be less than 248. min
and max
must\nbe safe integers.
If the callback
function is not provided, the random integer is\ngenerated synchronously.
// Asynchronous\nconst {\n randomInt,\n} = await import('node:crypto');\n\nrandomInt(3, (err, n) => {\n if (err) throw err;\n console.log(`Random number chosen from (0, 1, 2): ${n}`);\n});\n
\n// Asynchronous\nconst {\n randomInt,\n} = require('node:crypto');\n\nrandomInt(3, (err, n) => {\n if (err) throw err;\n console.log(`Random number chosen from (0, 1, 2): ${n}`);\n});\n
\n// Synchronous\nconst {\n randomInt,\n} = await import('node:crypto');\n\nconst n = randomInt(3);\nconsole.log(`Random number chosen from (0, 1, 2): ${n}`);\n
\n// Synchronous\nconst {\n randomInt,\n} = require('node:crypto');\n\nconst n = randomInt(3);\nconsole.log(`Random number chosen from (0, 1, 2): ${n}`);\n
\n// With `min` argument\nconst {\n randomInt,\n} = await import('node:crypto');\n\nconst n = randomInt(1, 7);\nconsole.log(`The dice rolled: ${n}`);\n
\n// With `min` argument\nconst {\n randomInt,\n} = require('node:crypto');\n\nconst n = randomInt(1, 7);\nconsole.log(`The dice rolled: ${n}`);\n
"
},
{
"textRaw": "`crypto.randomUUID([options])`",
"type": "method",
"name": "randomUUID",
"meta": {
"added": [
"v15.6.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`disableEntropyCache` {boolean} By default, to improve performance, Node.js generates and caches enough random data to generate up to 128 random UUIDs. To generate a UUID without using the cache, set `disableEntropyCache` to `true`. **Default:** `false`.",
"name": "disableEntropyCache",
"type": "boolean",
"default": "`false`",
"desc": "By default, to improve performance, Node.js generates and caches enough random data to generate up to 128 random UUIDs. To generate a UUID without using the cache, set `disableEntropyCache` to `true`."
}
]
}
]
}
],
"desc": "Generates a random RFC 4122 version 4 UUID. The UUID is generated using a\ncryptographic pseudorandom number generator.
" }, { "textRaw": "`crypto.scrypt(password, salt, keylen[, options], callback)`", "type": "method", "name": "scrypt", "meta": { "added": [ "v10.5.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/35093", "description": "The password and salt arguments can also be ArrayBuffer instances." }, { "version": [ "v12.8.0", "v10.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/28799", "description": "The `maxmem` value can now be any safe integer." }, { "version": "v10.9.0", "pr-url": "https://github.com/nodejs/node/pull/21525", "description": "The `cost`, `blockSize` and `parallelization` option names have been added." } ] }, "signatures": [ { "params": [ { "textRaw": "`password` {string|ArrayBuffer|Buffer|TypedArray|DataView}", "name": "password", "type": "string|ArrayBuffer|Buffer|TypedArray|DataView" }, { "textRaw": "`salt` {string|ArrayBuffer|Buffer|TypedArray|DataView}", "name": "salt", "type": "string|ArrayBuffer|Buffer|TypedArray|DataView" }, { "textRaw": "`keylen` {number}", "name": "keylen", "type": "number" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cost` {number} CPU/memory cost parameter. Must be a power of two greater than one. **Default:** `16384`.", "name": "cost", "type": "number", "default": "`16384`", "desc": "CPU/memory cost parameter. Must be a power of two greater than one." }, { "textRaw": "`blockSize` {number} Block size parameter. **Default:** `8`.", "name": "blockSize", "type": "number", "default": "`8`", "desc": "Block size parameter." }, { "textRaw": "`parallelization` {number} Parallelization parameter. **Default:** `1`.", "name": "parallelization", "type": "number", "default": "`1`", "desc": "Parallelization parameter." }, { "textRaw": "`N` {number} Alias for `cost`. Only one of both may be specified.", "name": "N", "type": "number", "desc": "Alias for `cost`. Only one of both may be specified." }, { "textRaw": "`r` {number} Alias for `blockSize`. Only one of both may be specified.", "name": "r", "type": "number", "desc": "Alias for `blockSize`. Only one of both may be specified." }, { "textRaw": "`p` {number} Alias for `parallelization`. Only one of both may be specified.", "name": "p", "type": "number", "desc": "Alias for `parallelization`. Only one of both may be specified." }, { "textRaw": "`maxmem` {number} Memory upper bound. It is an error when (approximately) `128 * N * r > maxmem`. **Default:** `32 * 1024 * 1024`.", "name": "maxmem", "type": "number", "default": "`32 * 1024 * 1024`", "desc": "Memory upper bound. It is an error when (approximately) `128 * N * r > maxmem`." } ] }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`derivedKey` {Buffer}", "name": "derivedKey", "type": "Buffer" } ] } ] } ], "desc": "Provides an asynchronous scrypt implementation. Scrypt is a password-based\nkey derivation function that is designed to be expensive computationally and\nmemory-wise in order to make brute-force attacks unrewarding.
\nThe salt
should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
When passing strings for password
or salt
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
The callback
function is called with two arguments: err
and derivedKey
.\nerr
is an exception object when key derivation fails, otherwise err
is\nnull
. derivedKey
is passed to the callback as a Buffer
.
An exception is thrown when any of the input arguments specify invalid values\nor types.
\nconst {\n scrypt,\n} = await import('node:crypto');\n\n// Using the factory defaults.\nscrypt('password', 'salt', 64, (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\n// Using a custom N parameter. Must be a power of two.\nscrypt('password', 'salt', 64, { N: 1024 }, (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...aa39b34'\n});\n
\nconst {\n scrypt,\n} = require('node:crypto');\n\n// Using the factory defaults.\nscrypt('password', 'salt', 64, (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\n// Using a custom N parameter. Must be a power of two.\nscrypt('password', 'salt', 64, { N: 1024 }, (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...aa39b34'\n});\n
"
},
{
"textRaw": "`crypto.scryptSync(password, salt, keylen[, options])`",
"type": "method",
"name": "scryptSync",
"meta": {
"added": [
"v10.5.0"
],
"changes": [
{
"version": [
"v12.8.0",
"v10.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/28799",
"description": "The `maxmem` value can now be any safe integer."
},
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21525",
"description": "The `cost`, `blockSize` and `parallelization` option names have been added."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer}",
"name": "return",
"type": "Buffer"
},
"params": [
{
"textRaw": "`password` {string|Buffer|TypedArray|DataView}",
"name": "password",
"type": "string|Buffer|TypedArray|DataView"
},
{
"textRaw": "`salt` {string|Buffer|TypedArray|DataView}",
"name": "salt",
"type": "string|Buffer|TypedArray|DataView"
},
{
"textRaw": "`keylen` {number}",
"name": "keylen",
"type": "number"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`cost` {number} CPU/memory cost parameter. Must be a power of two greater than one. **Default:** `16384`.",
"name": "cost",
"type": "number",
"default": "`16384`",
"desc": "CPU/memory cost parameter. Must be a power of two greater than one."
},
{
"textRaw": "`blockSize` {number} Block size parameter. **Default:** `8`.",
"name": "blockSize",
"type": "number",
"default": "`8`",
"desc": "Block size parameter."
},
{
"textRaw": "`parallelization` {number} Parallelization parameter. **Default:** `1`.",
"name": "parallelization",
"type": "number",
"default": "`1`",
"desc": "Parallelization parameter."
},
{
"textRaw": "`N` {number} Alias for `cost`. Only one of both may be specified.",
"name": "N",
"type": "number",
"desc": "Alias for `cost`. Only one of both may be specified."
},
{
"textRaw": "`r` {number} Alias for `blockSize`. Only one of both may be specified.",
"name": "r",
"type": "number",
"desc": "Alias for `blockSize`. Only one of both may be specified."
},
{
"textRaw": "`p` {number} Alias for `parallelization`. Only one of both may be specified.",
"name": "p",
"type": "number",
"desc": "Alias for `parallelization`. Only one of both may be specified."
},
{
"textRaw": "`maxmem` {number} Memory upper bound. It is an error when (approximately) `128 * N * r > maxmem`. **Default:** `32 * 1024 * 1024`.",
"name": "maxmem",
"type": "number",
"default": "`32 * 1024 * 1024`",
"desc": "Memory upper bound. It is an error when (approximately) `128 * N * r > maxmem`."
}
]
}
]
}
],
"desc": "Provides a synchronous scrypt implementation. Scrypt is a password-based\nkey derivation function that is designed to be expensive computationally and\nmemory-wise in order to make brute-force attacks unrewarding.
\nThe salt
should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
When passing strings for password
or salt
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
An exception is thrown when key derivation fails, otherwise the derived key is\nreturned as a Buffer
.
An exception is thrown when any of the input arguments specify invalid values\nor types.
\nconst {\n scryptSync,\n} = await import('node:crypto');\n// Using the factory defaults.\n\nconst key1 = scryptSync('password', 'salt', 64);\nconsole.log(key1.toString('hex')); // '3745e48...08d59ae'\n// Using a custom N parameter. Must be a power of two.\nconst key2 = scryptSync('password', 'salt', 64, { N: 1024 });\nconsole.log(key2.toString('hex')); // '3745e48...aa39b34'\n
\nconst {\n scryptSync,\n} = require('node:crypto');\n// Using the factory defaults.\n\nconst key1 = scryptSync('password', 'salt', 64);\nconsole.log(key1.toString('hex')); // '3745e48...08d59ae'\n// Using a custom N parameter. Must be a power of two.\nconst key2 = scryptSync('password', 'salt', 64, { N: 1024 });\nconsole.log(key2.toString('hex')); // '3745e48...aa39b34'\n
"
},
{
"textRaw": "`crypto.secureHeapUsed()`",
"type": "method",
"name": "secureHeapUsed",
"meta": {
"added": [
"v15.6.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object",
"options": [
{
"textRaw": "`total` {number} The total allocated secure heap size as specified using the `--secure-heap=n` command-line flag.",
"name": "total",
"type": "number",
"desc": "The total allocated secure heap size as specified using the `--secure-heap=n` command-line flag."
},
{
"textRaw": "`min` {number} The minimum allocation from the secure heap as specified using the `--secure-heap-min` command-line flag.",
"name": "min",
"type": "number",
"desc": "The minimum allocation from the secure heap as specified using the `--secure-heap-min` command-line flag."
},
{
"textRaw": "`used` {number} The total number of bytes currently allocated from the secure heap.",
"name": "used",
"type": "number",
"desc": "The total number of bytes currently allocated from the secure heap."
},
{
"textRaw": "`utilization` {number} The calculated ratio of `used` to `total` allocated bytes.",
"name": "utilization",
"type": "number",
"desc": "The calculated ratio of `used` to `total` allocated bytes."
}
]
},
"params": []
}
]
},
{
"textRaw": "`crypto.setEngine(engine[, flags])`",
"type": "method",
"name": "setEngine",
"meta": {
"added": [
"v0.11.11"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`engine` {string}",
"name": "engine",
"type": "string"
},
{
"textRaw": "`flags` {crypto.constants} **Default:** `crypto.constants.ENGINE_METHOD_ALL`",
"name": "flags",
"type": "crypto.constants",
"default": "`crypto.constants.ENGINE_METHOD_ALL`"
}
]
}
],
"desc": "Load and set the engine
for some or all OpenSSL functions (selected by flags).
engine
could be either an id or a path to the engine's shared library.
The optional flags
argument uses ENGINE_METHOD_ALL
by default. The flags
\nis a bit field taking one of or a mix of the following flags (defined in\ncrypto.constants
):
crypto.constants.ENGINE_METHOD_RSA
crypto.constants.ENGINE_METHOD_DSA
crypto.constants.ENGINE_METHOD_DH
crypto.constants.ENGINE_METHOD_RAND
crypto.constants.ENGINE_METHOD_EC
crypto.constants.ENGINE_METHOD_CIPHERS
crypto.constants.ENGINE_METHOD_DIGESTS
crypto.constants.ENGINE_METHOD_PKEY_METHS
crypto.constants.ENGINE_METHOD_PKEY_ASN1_METHS
crypto.constants.ENGINE_METHOD_ALL
crypto.constants.ENGINE_METHOD_NONE
Enables the FIPS compliant crypto provider in a FIPS-enabled Node.js build.\nThrows an error if FIPS mode is not available.
" }, { "textRaw": "`crypto.sign(algorithm, data, key[, callback])`", "type": "method", "name": "sign", "meta": { "added": [ "v12.0.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v15.12.0", "pr-url": "https://github.com/nodejs/node/pull/37500", "description": "Optional callback argument added." }, { "version": [ "v13.2.0", "v12.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/29292", "description": "This function now supports IEEE-P1363 DSA and ECDSA signatures." } ] }, "signatures": [ { "params": [] } ], "desc": "\nalgorithm
<string> | <null> | <undefined>data
<ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>key
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>callback
<Function>\n\ncallback
function is not provided.Calculates and returns the signature for data
using the given private key and\nalgorithm. If algorithm
is null
or undefined
, then the algorithm is\ndependent upon the key type (especially Ed25519 and Ed448).
If key
is not a KeyObject
, this function behaves as if key
had been\npassed to crypto.createPrivateKey()
. If it is an object, the following\nadditional properties can be passed:
dsaEncoding
<string> For DSA and ECDSA, this option specifies the\nformat of the generated signature. It can be one of the following:
'der'
(default): DER-encoded ASN.1 signature structure encoding (r, s)
.'ieee-p1363'
: Signature format r || s
as proposed in IEEE-P1363.padding
<integer> Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING
(default)crypto.constants.RSA_PKCS1_PSS_PADDING
RSA_PKCS1_PSS_PADDING
will use MGF1 with the same hash function\nused to sign the message as specified in section 3.1 of RFC 4055.
saltLength
<integer> Salt length for when padding is\nRSA_PKCS1_PSS_PADDING
. The special value\ncrypto.constants.RSA_PSS_SALTLEN_DIGEST
sets the salt length to the digest\nsize, crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN
(default) sets it to the\nmaximum permissible value.
If the callback
function is provided this function uses libuv's threadpool.
This function compares the underlying bytes that represent the given\nArrayBuffer
, TypedArray
, or DataView
instances using a constant-time\nalgorithm.
This function does not leak timing information that\nwould allow an attacker to guess one of the values. This is suitable for\ncomparing HMAC digests or secret values like authentication cookies or\ncapability urls.
\na
and b
must both be Buffer
s, TypedArray
s, or DataView
s, and they\nmust have the same byte length. An error is thrown if a
and b
have\ndifferent byte lengths.
If at least one of a
and b
is a TypedArray
with more than one byte per\nentry, such as Uint16Array
, the result will be computed using the platform\nbyte order.
When both of the inputs are Float32Array
s or\nFloat64Array
s, this function might return unexpected results due to IEEE 754\nencoding of floating-point numbers. In particular, neither x === y
nor\nObject.is(x, y)
implies that the byte representations of two floating-point\nnumbers x
and y
are equal.
Use of crypto.timingSafeEqual
does not guarantee that the surrounding code\nis timing-safe. Care should be taken to ensure that the surrounding code does\nnot introduce timing vulnerabilities.
algorithm
<string> | <null> | <undefined>data
<ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>key
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>signature
<ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>callback
<Function>\n\ntrue
or false
depending on the validity of the\nsignature for the data and public key if the callback
function is not\nprovided.Verifies the given signature for data
using the given key and algorithm. If\nalgorithm
is null
or undefined
, then the algorithm is dependent upon the\nkey type (especially Ed25519 and Ed448).
If key
is not a KeyObject
, this function behaves as if key
had been\npassed to crypto.createPublicKey()
. If it is an object, the following\nadditional properties can be passed:
dsaEncoding
<string> For DSA and ECDSA, this option specifies the\nformat of the signature. It can be one of the following:
'der'
(default): DER-encoded ASN.1 signature structure encoding (r, s)
.'ieee-p1363'
: Signature format r || s
as proposed in IEEE-P1363.padding
<integer> Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING
(default)crypto.constants.RSA_PKCS1_PSS_PADDING
RSA_PKCS1_PSS_PADDING
will use MGF1 with the same hash function\nused to sign the message as specified in section 3.1 of RFC 4055.
saltLength
<integer> Salt length for when padding is\nRSA_PKCS1_PSS_PADDING
. The special value\ncrypto.constants.RSA_PSS_SALTLEN_DIGEST
sets the salt length to the digest\nsize, crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN
(default) sets it to the\nmaximum permissible value.
The signature
argument is the previously calculated signature for the data
.
Because public keys can be derived from private keys, a private key or a public\nkey may be passed for key
.
If the callback
function is provided this function uses libuv's threadpool.
For historical reasons, many cryptographic APIs provided by Node.js accept\nstrings as inputs where the underlying cryptographic algorithm works on byte\nsequences. These instances include plaintexts, ciphertexts, symmetric keys,\ninitialization vectors, passphrases, salts, authentication tags,\nand additional authenticated data.
\nWhen passing strings to cryptographic APIs, consider the following factors.
\nNot all byte sequences are valid UTF-8 strings. Therefore, when a byte\nsequence of length n
is derived from a string, its entropy is generally\nlower than the entropy of a random or pseudorandom n
byte sequence.\nFor example, no UTF-8 string will result in the byte sequence c0 af
. Secret\nkeys should almost exclusively be random or pseudorandom byte sequences.
Similarly, when converting random or pseudorandom byte sequences to UTF-8\nstrings, subsequences that do not represent valid code points may be replaced\nby the Unicode replacement character (U+FFFD
). The byte representation of\nthe resulting Unicode string may, therefore, not be equal to the byte sequence\nthat the string was created from.
const original = [0xc0, 0xaf];\nconst bytesAsString = Buffer.from(original).toString('utf8');\nconst stringAsBytes = Buffer.from(bytesAsString, 'utf8');\nconsole.log(stringAsBytes);\n// Prints '<Buffer ef bf bd ef bf bd>'.\n
\nThe outputs of ciphers, hash functions, signature algorithms, and key\nderivation functions are pseudorandom byte sequences and should not be\nused as Unicode strings.
\nWhen strings are obtained from user input, some Unicode characters can be\nrepresented in multiple equivalent ways that result in different byte\nsequences. For example, when passing a user passphrase to a key derivation\nfunction, such as PBKDF2 or scrypt, the result of the key derivation function\ndepends on whether the string uses composed or decomposed characters. Node.js\ndoes not normalize character representations. Developers should consider using\nString.prototype.normalize()
on user inputs before passing them to\ncryptographic APIs.
The Crypto module was added to Node.js before there was the concept of a\nunified Stream API, and before there were Buffer
objects for handling\nbinary data. As such, many crypto
classes have methods not\ntypically found on other Node.js classes that implement the streams\nAPI (e.g. update()
, final()
, or digest()
). Also, many methods accepted\nand returned 'latin1'
encoded strings by default rather than Buffer
s. This\ndefault was changed after Node.js v0.8 to use Buffer
objects by default\ninstead.
The node:crypto
module still supports some algorithms which are already\ncompromised and are not recommended for use. The API also allows\nthe use of ciphers and hashes with a small key size that are too weak for safe\nuse.
Users should take full responsibility for selecting the crypto\nalgorithm and key size according to their security requirements.
\nBased on the recommendations of NIST SP 800-131A:
\nmodp1
, modp2
and modp5
have a key size\nsmaller than 2048 bits and are not recommended.See the reference for other recommendations and details.
\nSome algorithms that have known weaknesses and are of little relevance in\npractice are only available through the legacy provider, which is not\nenabled by default.
", "type": "module", "displayName": "Support for weak or compromised algorithms" }, { "textRaw": "CCM mode", "name": "ccm_mode", "desc": "CCM is one of the supported AEAD algorithms. Applications which use this\nmode must adhere to certain restrictions when using the cipher API:
\nauthTagLength
option and must be one of 4, 6, 8, 10, 12, 14 or\n16 bytes.N
must be between 7 and 13\nbytes (7 ≤ N ≤ 13
).2 ** (8 * (15 - N))
bytes.setAuthTag()
before\ncalling update()
.\nOtherwise, decryption will fail and final()
will throw an error in\ncompliance with section 2.6 of RFC 3610.write(data)
, end(data)
or pipe()
in CCM\nmode might fail as CCM cannot handle more than one chunk of data per instance.setAAD()
via the plaintextLength
\noption.\nMany crypto libraries include the authentication tag in the ciphertext,\nwhich means that they produce ciphertexts of the length\nplaintextLength + authTagLength
. Node.js does not include the authentication\ntag, so the ciphertext length is always plaintextLength
.\nThis is not necessary if no AAD is used.update()
must be called exactly\nonce.update()
is sufficient to encrypt/decrypt the message,\napplications must call final()
to compute or verify the\nauthentication tag.import { Buffer } from 'node:buffer';\nconst {\n createCipheriv,\n createDecipheriv,\n randomBytes,\n} = await import('node:crypto');\n\nconst key = 'keykeykeykeykeykeykeykey';\nconst nonce = randomBytes(12);\n\nconst aad = Buffer.from('0123456789', 'hex');\n\nconst cipher = createCipheriv('aes-192-ccm', key, nonce, {\n authTagLength: 16,\n});\nconst plaintext = 'Hello world';\ncipher.setAAD(aad, {\n plaintextLength: Buffer.byteLength(plaintext),\n});\nconst ciphertext = cipher.update(plaintext, 'utf8');\ncipher.final();\nconst tag = cipher.getAuthTag();\n\n// Now transmit { ciphertext, nonce, tag }.\n\nconst decipher = createDecipheriv('aes-192-ccm', key, nonce, {\n authTagLength: 16,\n});\ndecipher.setAuthTag(tag);\ndecipher.setAAD(aad, {\n plaintextLength: ciphertext.length,\n});\nconst receivedPlaintext = decipher.update(ciphertext, null, 'utf8');\n\ntry {\n decipher.final();\n} catch (err) {\n throw new Error('Authentication failed!', { cause: err });\n}\n\nconsole.log(receivedPlaintext);\n
\nconst { Buffer } = require('node:buffer');\nconst {\n createCipheriv,\n createDecipheriv,\n randomBytes,\n} = require('node:crypto');\n\nconst key = 'keykeykeykeykeykeykeykey';\nconst nonce = randomBytes(12);\n\nconst aad = Buffer.from('0123456789', 'hex');\n\nconst cipher = createCipheriv('aes-192-ccm', key, nonce, {\n authTagLength: 16,\n});\nconst plaintext = 'Hello world';\ncipher.setAAD(aad, {\n plaintextLength: Buffer.byteLength(plaintext),\n});\nconst ciphertext = cipher.update(plaintext, 'utf8');\ncipher.final();\nconst tag = cipher.getAuthTag();\n\n// Now transmit { ciphertext, nonce, tag }.\n\nconst decipher = createDecipheriv('aes-192-ccm', key, nonce, {\n authTagLength: 16,\n});\ndecipher.setAuthTag(tag);\ndecipher.setAAD(aad, {\n plaintextLength: ciphertext.length,\n});\nconst receivedPlaintext = decipher.update(ciphertext, null, 'utf8');\n\ntry {\n decipher.final();\n} catch (err) {\n throw new Error('Authentication failed!', { cause: err });\n}\n\nconsole.log(receivedPlaintext);\n
",
"type": "module",
"displayName": "CCM mode"
},
{
"textRaw": "FIPS mode",
"name": "fips_mode",
"desc": "When using OpenSSL 3, Node.js supports FIPS 140-2 when used with an appropriate\nOpenSSL 3 provider, such as the FIPS provider from OpenSSL 3 which can be\ninstalled by following the instructions in OpenSSL's FIPS README file.
\nFor FIPS support in Node.js you will need:
\nNode.js will need to be configured with an OpenSSL configuration file that\npoints to the FIPS provider. An example configuration file looks like this:
\nnodejs_conf = nodejs_init\n\n.include /<absolute path>/fipsmodule.cnf\n\n[nodejs_init]\nproviders = provider_sect\n\n[provider_sect]\ndefault = default_sect\n# The fips section name should match the section name inside the\n# included fipsmodule.cnf.\nfips = fips_sect\n\n[default_sect]\nactivate = 1\n
\nwhere fipsmodule.cnf
is the FIPS module configuration file generated from the\nFIPS provider installation step:
openssl fipsinstall\n
\nSet the OPENSSL_CONF
environment variable to point to\nyour configuration file and OPENSSL_MODULES
to the location of the FIPS\nprovider dynamic library. e.g.
export OPENSSL_CONF=/<path to configuration file>/nodejs.cnf\nexport OPENSSL_MODULES=/<path to openssl lib>/ossl-modules\n
\nFIPS mode can then be enabled in Node.js either by:
\n--enable-fips
or --force-fips
command line flags.crypto.setFips(true)
.Optionally FIPS mode can be enabled in Node.js via the OpenSSL configuration\nfile. e.g.
\nnodejs_conf = nodejs_init\n\n.include /<absolute path>/fipsmodule.cnf\n\n[nodejs_init]\nproviders = provider_sect\nalg_section = algorithm_sect\n\n[provider_sect]\ndefault = default_sect\n# The fips section name should match the section name inside the\n# included fipsmodule.cnf.\nfips = fips_sect\n\n[default_sect]\nactivate = 1\n\n[algorithm_sect]\ndefault_properties = fips=yes\n
",
"type": "module",
"displayName": "FIPS mode"
}
],
"type": "module",
"displayName": "Notes"
},
{
"textRaw": "Crypto constants",
"name": "crypto_constants",
"desc": "The following constants exported by crypto.constants
apply to various uses of\nthe node:crypto
, node:tls
, and node:https
modules and are generally\nspecific to OpenSSL.
See the list of SSL OP Flags for details.
\nConstant | \nDescription | \n
---|---|
SSL_OP_ALL | \n Applies multiple bug workarounds within OpenSSL. See\n https://www.openssl.org/docs/man3.0/man3/SSL_CTX_set_options.html\n for detail. | \n
SSL_OP_ALLOW_NO_DHE_KEX | \n Instructs OpenSSL to allow a non-[EC]DHE-based key exchange mode\n for TLS v1.3 | \n
SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION | \n Allows legacy insecure renegotiation between OpenSSL and unpatched\n clients or servers. See\n https://www.openssl.org/docs/man3.0/man3/SSL_CTX_set_options.html. | \n
SSL_OP_CIPHER_SERVER_PREFERENCE | \n Attempts to use the server's preferences instead of the client's when\n selecting a cipher. Behavior depends on protocol version. See\n https://www.openssl.org/docs/man3.0/man3/SSL_CTX_set_options.html. | \n
SSL_OP_CISCO_ANYCONNECT | \n Instructs OpenSSL to use Cisco's \"speshul\" version of DTLS_BAD_VER. | \n
SSL_OP_COOKIE_EXCHANGE | \n Instructs OpenSSL to turn on cookie exchange. | \n
SSL_OP_CRYPTOPRO_TLSEXT_BUG | \n Instructs OpenSSL to add server-hello extension from an early version\n of the cryptopro draft. | \n
SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS | \n Instructs OpenSSL to disable a SSL 3.0/TLS 1.0 vulnerability\n workaround added in OpenSSL 0.9.6d. | \n
SSL_OP_LEGACY_SERVER_CONNECT | \n Allows initial connection to servers that do not support RI. | \n
SSL_OP_NO_COMPRESSION | \n Instructs OpenSSL to disable support for SSL/TLS compression. | \n
SSL_OP_NO_ENCRYPT_THEN_MAC | \n Instructs OpenSSL to disable encrypt-then-MAC. | \n
SSL_OP_NO_QUERY_MTU | \n \n |
SSL_OP_NO_RENEGOTIATION | \n Instructs OpenSSL to disable renegotiation. | \n
SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION | \n Instructs OpenSSL to always start a new session when performing\n renegotiation. | \n
SSL_OP_NO_SSLv2 | \n Instructs OpenSSL to turn off SSL v2 | \n
SSL_OP_NO_SSLv3 | \n Instructs OpenSSL to turn off SSL v3 | \n
SSL_OP_NO_TICKET | \n Instructs OpenSSL to disable use of RFC4507bis tickets. | \n
SSL_OP_NO_TLSv1 | \n Instructs OpenSSL to turn off TLS v1 | \n
SSL_OP_NO_TLSv1_1 | \n Instructs OpenSSL to turn off TLS v1.1 | \n
SSL_OP_NO_TLSv1_2 | \n Instructs OpenSSL to turn off TLS v1.2 | \n
SSL_OP_NO_TLSv1_3 | \n Instructs OpenSSL to turn off TLS v1.3 | \n
SSL_OP_PRIORITIZE_CHACHA | \n Instructs OpenSSL server to prioritize ChaCha20-Poly1305\n when the client does.\n This option has no effect if\n SSL_OP_CIPHER_SERVER_PREFERENCE \n is not enabled. | \n
SSL_OP_TLS_ROLLBACK_BUG | \n Instructs OpenSSL to disable version rollback attack detection. | \n
Constant | \nDescription | \n
---|---|
ENGINE_METHOD_RSA | \n Limit engine usage to RSA | \n
ENGINE_METHOD_DSA | \n Limit engine usage to DSA | \n
ENGINE_METHOD_DH | \n Limit engine usage to DH | \n
ENGINE_METHOD_RAND | \n Limit engine usage to RAND | \n
ENGINE_METHOD_EC | \n Limit engine usage to EC | \n
ENGINE_METHOD_CIPHERS | \n Limit engine usage to CIPHERS | \n
ENGINE_METHOD_DIGESTS | \n Limit engine usage to DIGESTS | \n
ENGINE_METHOD_PKEY_METHS | \n Limit engine usage to PKEY_METHDS | \n
ENGINE_METHOD_PKEY_ASN1_METHS | \n Limit engine usage to PKEY_ASN1_METHS | \n
ENGINE_METHOD_ALL | \n \n |
ENGINE_METHOD_NONE | \n \n |
Constant | \nDescription | \n
---|---|
DH_CHECK_P_NOT_SAFE_PRIME | \n \n |
DH_CHECK_P_NOT_PRIME | \n \n |
DH_UNABLE_TO_CHECK_GENERATOR | \n \n |
DH_NOT_SUITABLE_GENERATOR | \n \n |
RSA_PKCS1_PADDING | \n \n |
RSA_SSLV23_PADDING | \n \n |
RSA_NO_PADDING | \n \n |
RSA_PKCS1_OAEP_PADDING | \n \n |
RSA_X931_PADDING | \n \n |
RSA_PKCS1_PSS_PADDING | \n \n |
RSA_PSS_SALTLEN_DIGEST | \n Sets the salt length for RSA_PKCS1_PSS_PADDING to the\n digest size when signing or verifying. | \n
RSA_PSS_SALTLEN_MAX_SIGN | \n Sets the salt length for RSA_PKCS1_PSS_PADDING to the\n maximum permissible value when signing data. | \n
RSA_PSS_SALTLEN_AUTO | \n Causes the salt length for RSA_PKCS1_PSS_PADDING to be\n determined automatically when verifying a signature. | \n
POINT_CONVERSION_COMPRESSED | \n \n |
POINT_CONVERSION_UNCOMPRESSED | \n \n |
POINT_CONVERSION_HYBRID | \n \n |
Constant | \nDescription | \n
---|---|
defaultCoreCipherList | \n Specifies the built-in default cipher list used by Node.js. | \n
defaultCipherList | \n Specifies the active default cipher list used by the current Node.js\n process. | \n
SPKAC is a Certificate Signing Request mechanism originally implemented by\nNetscape and was specified formally as part of HTML5's keygen
element.
<keygen>
is deprecated since HTML 5.2 and new projects\nshould not use this element anymore.
The node:crypto
module provides the Certificate
class for working with SPKAC\ndata. The most common usage is handling output generated by the HTML5\n<keygen>
element. Node.js uses OpenSSL's SPKAC implementation internally.
const { Certificate } = await import('node:crypto');\nconst spkac = getSpkacSomehow();\nconst challenge = Certificate.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n// Prints: the challenge as a UTF8 string\n
\nconst { Certificate } = require('node:crypto');\nconst spkac = getSpkacSomehow();\nconst challenge = Certificate.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n// Prints: the challenge as a UTF8 string\n
"
},
{
"textRaw": "Static method: `Certificate.exportPublicKey(spkac[, encoding])`",
"type": "classMethod",
"name": "exportPublicKey",
"meta": {
"added": [
"v9.0.0"
],
"changes": [
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35093",
"description": "The spkac argument can be an ArrayBuffer. Limited the size of the spkac argument to a maximum of 2**31 - 1 bytes."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} The public key component of the `spkac` data structure, which includes a public key and a challenge.",
"name": "return",
"type": "Buffer",
"desc": "The public key component of the `spkac` data structure, which includes a public key and a challenge."
},
"params": [
{
"textRaw": "`spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "spkac",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`encoding` {string} The [encoding][] of the `spkac` string.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the `spkac` string."
}
]
}
],
"desc": "const { Certificate } = await import('node:crypto');\nconst spkac = getSpkacSomehow();\nconst publicKey = Certificate.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\n
\nconst { Certificate } = require('node:crypto');\nconst spkac = getSpkacSomehow();\nconst publicKey = Certificate.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\n
"
},
{
"textRaw": "Static method: `Certificate.verifySpkac(spkac[, encoding])`",
"type": "classMethod",
"name": "verifySpkac",
"meta": {
"added": [
"v9.0.0"
],
"changes": [
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35093",
"description": "The spkac argument can be an ArrayBuffer. Added encoding. Limited the size of the spkac argument to a maximum of 2**31 - 1 bytes."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if the given `spkac` data structure is valid, `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if the given `spkac` data structure is valid, `false` otherwise."
},
"params": [
{
"textRaw": "`spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "spkac",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`encoding` {string} The [encoding][] of the `spkac` string.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the `spkac` string."
}
]
}
],
"desc": "import { Buffer } from 'node:buffer';\nconst { Certificate } = await import('node:crypto');\n\nconst spkac = getSpkacSomehow();\nconsole.log(Certificate.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\n
\nconst { Buffer } = require('node:buffer');\nconst { Certificate } = require('node:crypto');\n\nconst spkac = getSpkacSomehow();\nconsole.log(Certificate.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\n
"
}
],
"modules": [
{
"textRaw": "Legacy API",
"name": "legacy_api",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "As a legacy interface, it is possible to create new instances of\nthe crypto.Certificate
class as illustrated in the examples below.
Instances of the Certificate
class can be created using the new
keyword\nor by calling crypto.Certificate()
as a function:
const { Certificate } = await import('node:crypto');\n\nconst cert1 = new Certificate();\nconst cert2 = Certificate();\n
\nconst { Certificate } = require('node:crypto');\n\nconst cert1 = new Certificate();\nconst cert2 = Certificate();\n
"
}
],
"methods": [
{
"textRaw": "`certificate.exportChallenge(spkac[, encoding])`",
"type": "method",
"name": "exportChallenge",
"meta": {
"added": [
"v0.11.8"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} The challenge component of the `spkac` data structure, which includes a public key and a challenge.",
"name": "return",
"type": "Buffer",
"desc": "The challenge component of the `spkac` data structure, which includes a public key and a challenge."
},
"params": [
{
"textRaw": "`spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "spkac",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`encoding` {string} The [encoding][] of the `spkac` string.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the `spkac` string."
}
]
}
],
"desc": "const { Certificate } = await import('node:crypto');\nconst cert = Certificate();\nconst spkac = getSpkacSomehow();\nconst challenge = cert.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n// Prints: the challenge as a UTF8 string\n
\nconst { Certificate } = require('node:crypto');\nconst cert = Certificate();\nconst spkac = getSpkacSomehow();\nconst challenge = cert.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n// Prints: the challenge as a UTF8 string\n
"
},
{
"textRaw": "`certificate.exportPublicKey(spkac[, encoding])`",
"type": "method",
"name": "exportPublicKey",
"meta": {
"added": [
"v0.11.8"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer} The public key component of the `spkac` data structure, which includes a public key and a challenge.",
"name": "return",
"type": "Buffer",
"desc": "The public key component of the `spkac` data structure, which includes a public key and a challenge."
},
"params": [
{
"textRaw": "`spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "spkac",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`encoding` {string} The [encoding][] of the `spkac` string.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the `spkac` string."
}
]
}
],
"desc": "const { Certificate } = await import('node:crypto');\nconst cert = Certificate();\nconst spkac = getSpkacSomehow();\nconst publicKey = cert.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\n
\nconst { Certificate } = require('node:crypto');\nconst cert = Certificate();\nconst spkac = getSpkacSomehow();\nconst publicKey = cert.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\n
"
},
{
"textRaw": "`certificate.verifySpkac(spkac[, encoding])`",
"type": "method",
"name": "verifySpkac",
"meta": {
"added": [
"v0.11.8"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if the given `spkac` data structure is valid, `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if the given `spkac` data structure is valid, `false` otherwise."
},
"params": [
{
"textRaw": "`spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "spkac",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`encoding` {string} The [encoding][] of the `spkac` string.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the `spkac` string."
}
]
}
],
"desc": "import { Buffer } from 'node:buffer';\nconst { Certificate } = await import('node:crypto');\n\nconst cert = Certificate();\nconst spkac = getSpkacSomehow();\nconsole.log(cert.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\n
\nconst { Buffer } = require('node:buffer');\nconst { Certificate } = require('node:crypto');\n\nconst cert = Certificate();\nconst spkac = getSpkacSomehow();\nconsole.log(cert.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\n
"
}
],
"type": "module",
"displayName": "Legacy API"
}
]
},
{
"textRaw": "Class: `Cipher`",
"type": "class",
"name": "Cipher",
"meta": {
"added": [
"v0.1.94"
],
"changes": []
},
"desc": "Instances of the Cipher
class are used to encrypt data. The class can be\nused in one of two ways:
cipher.update()
and cipher.final()
methods to produce\nthe encrypted data.The crypto.createCipher()
or crypto.createCipheriv()
methods are\nused to create Cipher
instances. Cipher
objects are not to be created\ndirectly using the new
keyword.
Example: Using Cipher
objects as streams:
const {\n scrypt,\n randomFill,\n createCipheriv,\n} = await import('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n\n// First, we'll generate the key. The key length is dependent on the algorithm.\n// In this case for aes192, it is 24 bytes (192 bits).\nscrypt(password, 'salt', 24, (err, key) => {\n if (err) throw err;\n // Then, we'll generate a random initialization vector\n randomFill(new Uint8Array(16), (err, iv) => {\n if (err) throw err;\n\n // Once we have the key and iv, we can create and use the cipher...\n const cipher = createCipheriv(algorithm, key, iv);\n\n let encrypted = '';\n cipher.setEncoding('hex');\n\n cipher.on('data', (chunk) => encrypted += chunk);\n cipher.on('end', () => console.log(encrypted));\n\n cipher.write('some clear text data');\n cipher.end();\n });\n});\n
\nconst {\n scrypt,\n randomFill,\n createCipheriv,\n} = require('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n\n// First, we'll generate the key. The key length is dependent on the algorithm.\n// In this case for aes192, it is 24 bytes (192 bits).\nscrypt(password, 'salt', 24, (err, key) => {\n if (err) throw err;\n // Then, we'll generate a random initialization vector\n randomFill(new Uint8Array(16), (err, iv) => {\n if (err) throw err;\n\n // Once we have the key and iv, we can create and use the cipher...\n const cipher = createCipheriv(algorithm, key, iv);\n\n let encrypted = '';\n cipher.setEncoding('hex');\n\n cipher.on('data', (chunk) => encrypted += chunk);\n cipher.on('end', () => console.log(encrypted));\n\n cipher.write('some clear text data');\n cipher.end();\n });\n});\n
\nExample: Using Cipher
and piped streams:
import {\n createReadStream,\n createWriteStream,\n} from 'node:fs';\n\nimport {\n pipeline,\n} from 'node:stream';\n\nconst {\n scrypt,\n randomFill,\n createCipheriv,\n} = await import('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n\n// First, we'll generate the key. The key length is dependent on the algorithm.\n// In this case for aes192, it is 24 bytes (192 bits).\nscrypt(password, 'salt', 24, (err, key) => {\n if (err) throw err;\n // Then, we'll generate a random initialization vector\n randomFill(new Uint8Array(16), (err, iv) => {\n if (err) throw err;\n\n const cipher = createCipheriv(algorithm, key, iv);\n\n const input = createReadStream('test.js');\n const output = createWriteStream('test.enc');\n\n pipeline(input, cipher, output, (err) => {\n if (err) throw err;\n });\n });\n});\n
\nconst {\n createReadStream,\n createWriteStream,\n} = require('node:fs');\n\nconst {\n pipeline,\n} = require('node:stream');\n\nconst {\n scrypt,\n randomFill,\n createCipheriv,\n} = require('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n\n// First, we'll generate the key. The key length is dependent on the algorithm.\n// In this case for aes192, it is 24 bytes (192 bits).\nscrypt(password, 'salt', 24, (err, key) => {\n if (err) throw err;\n // Then, we'll generate a random initialization vector\n randomFill(new Uint8Array(16), (err, iv) => {\n if (err) throw err;\n\n const cipher = createCipheriv(algorithm, key, iv);\n\n const input = createReadStream('test.js');\n const output = createWriteStream('test.enc');\n\n pipeline(input, cipher, output, (err) => {\n if (err) throw err;\n });\n });\n});\n
\nExample: Using the cipher.update()
and cipher.final()
methods:
const {\n scrypt,\n randomFill,\n createCipheriv,\n} = await import('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n\n// First, we'll generate the key. The key length is dependent on the algorithm.\n// In this case for aes192, it is 24 bytes (192 bits).\nscrypt(password, 'salt', 24, (err, key) => {\n if (err) throw err;\n // Then, we'll generate a random initialization vector\n randomFill(new Uint8Array(16), (err, iv) => {\n if (err) throw err;\n\n const cipher = createCipheriv(algorithm, key, iv);\n\n let encrypted = cipher.update('some clear text data', 'utf8', 'hex');\n encrypted += cipher.final('hex');\n console.log(encrypted);\n });\n});\n
\nconst {\n scrypt,\n randomFill,\n createCipheriv,\n} = require('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n\n// First, we'll generate the key. The key length is dependent on the algorithm.\n// In this case for aes192, it is 24 bytes (192 bits).\nscrypt(password, 'salt', 24, (err, key) => {\n if (err) throw err;\n // Then, we'll generate a random initialization vector\n randomFill(new Uint8Array(16), (err, iv) => {\n if (err) throw err;\n\n const cipher = createCipheriv(algorithm, key, iv);\n\n let encrypted = cipher.update('some clear text data', 'utf8', 'hex');\n encrypted += cipher.final('hex');\n console.log(encrypted);\n });\n});\n
",
"methods": [
{
"textRaw": "`cipher.final([outputEncoding])`",
"type": "method",
"name": "final",
"meta": {
"added": [
"v0.1.94"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string} Any remaining enciphered contents. If `outputEncoding` is specified, a string is returned. If an `outputEncoding` is not provided, a [`Buffer`][] is returned.",
"name": "return",
"type": "Buffer | string",
"desc": "Any remaining enciphered contents. If `outputEncoding` is specified, a string is returned. If an `outputEncoding` is not provided, a [`Buffer`][] is returned."
},
"params": [
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value."
}
]
}
],
"desc": "Once the cipher.final()
method has been called, the Cipher
object can no\nlonger be used to encrypt data. Attempts to call cipher.final()
more than\nonce will result in an error being thrown.
The cipher.getAuthTag()
method should only be called after encryption has\nbeen completed using the cipher.final()
method.
If the authTagLength
option was set during the cipher
instance's creation,\nthis function will return exactly authTagLength
bytes.
When using an authenticated encryption mode (GCM
, CCM
, OCB
, and\nchacha20-poly1305
are\ncurrently supported), the cipher.setAAD()
method sets the value used for the\nadditional authenticated data (AAD) input parameter.
The plaintextLength
option is optional for GCM
and OCB
. When using CCM
,\nthe plaintextLength
option must be specified and its value must match the\nlength of the plaintext in bytes. See CCM mode.
The cipher.setAAD()
method must be called before cipher.update()
.
When using block encryption algorithms, the Cipher
class will automatically\nadd padding to the input data to the appropriate block size. To disable the\ndefault padding call cipher.setAutoPadding(false)
.
When autoPadding
is false
, the length of the entire input data must be a\nmultiple of the cipher's block size or cipher.final()
will throw an error.\nDisabling automatic padding is useful for non-standard padding, for instance\nusing 0x0
instead of PKCS padding.
The cipher.setAutoPadding()
method must be called before\ncipher.final()
.
Updates the cipher with data
. If the inputEncoding
argument is given,\nthe data
\nargument is a string using the specified encoding. If the inputEncoding
\nargument is not given, data
must be a Buffer
, TypedArray
, or\nDataView
. If data
is a Buffer
, TypedArray
, or DataView
, then\ninputEncoding
is ignored.
The outputEncoding
specifies the output format of the enciphered\ndata. If the outputEncoding
\nis specified, a string using the specified encoding is returned. If no\noutputEncoding
is provided, a Buffer
is returned.
The cipher.update()
method can be called multiple times with new data until\ncipher.final()
is called. Calling cipher.update()
after\ncipher.final()
will result in an error being thrown.
Instances of the Decipher
class are used to decrypt data. The class can be\nused in one of two ways:
decipher.update()
and decipher.final()
methods to\nproduce the unencrypted data.The crypto.createDecipher()
or crypto.createDecipheriv()
methods are\nused to create Decipher
instances. Decipher
objects are not to be created\ndirectly using the new
keyword.
Example: Using Decipher
objects as streams:
import { Buffer } from 'node:buffer';\nconst {\n scryptSync,\n createDecipheriv,\n} = await import('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Key length is dependent on the algorithm. In this case for aes192, it is\n// 24 bytes (192 bits).\n// Use the async `crypto.scrypt()` instead.\nconst key = scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = createDecipheriv(algorithm, key, iv);\n\nlet decrypted = '';\ndecipher.on('readable', () => {\n let chunk;\n while (null !== (chunk = decipher.read())) {\n decrypted += chunk.toString('utf8');\n }\n});\ndecipher.on('end', () => {\n console.log(decrypted);\n // Prints: some clear text data\n});\n\n// Encrypted with same algorithm, key and iv.\nconst encrypted =\n 'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';\ndecipher.write(encrypted, 'hex');\ndecipher.end();\n
\nconst {\n scryptSync,\n createDecipheriv,\n} = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Key length is dependent on the algorithm. In this case for aes192, it is\n// 24 bytes (192 bits).\n// Use the async `crypto.scrypt()` instead.\nconst key = scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = createDecipheriv(algorithm, key, iv);\n\nlet decrypted = '';\ndecipher.on('readable', () => {\n let chunk;\n while (null !== (chunk = decipher.read())) {\n decrypted += chunk.toString('utf8');\n }\n});\ndecipher.on('end', () => {\n console.log(decrypted);\n // Prints: some clear text data\n});\n\n// Encrypted with same algorithm, key and iv.\nconst encrypted =\n 'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';\ndecipher.write(encrypted, 'hex');\ndecipher.end();\n
\nExample: Using Decipher
and piped streams:
import {\n createReadStream,\n createWriteStream,\n} from 'node:fs';\nimport { Buffer } from 'node:buffer';\nconst {\n scryptSync,\n createDecipheriv,\n} = await import('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = createDecipheriv(algorithm, key, iv);\n\nconst input = createReadStream('test.enc');\nconst output = createWriteStream('test.js');\n\ninput.pipe(decipher).pipe(output);\n
\nconst {\n createReadStream,\n createWriteStream,\n} = require('node:fs');\nconst {\n scryptSync,\n createDecipheriv,\n} = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = createDecipheriv(algorithm, key, iv);\n\nconst input = createReadStream('test.enc');\nconst output = createWriteStream('test.js');\n\ninput.pipe(decipher).pipe(output);\n
\nExample: Using the decipher.update()
and decipher.final()
methods:
import { Buffer } from 'node:buffer';\nconst {\n scryptSync,\n createDecipheriv,\n} = await import('node:crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = createDecipheriv(algorithm, key, iv);\n\n// Encrypted using same algorithm, key and iv.\nconst encrypted =\n 'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';\nlet decrypted = decipher.update(encrypted, 'hex', 'utf8');\ndecrypted += decipher.final('utf8');\nconsole.log(decrypted);\n// Prints: some clear text data\n
\nconst {\n scryptSync,\n createDecipheriv,\n} = require('node:crypto');\nconst { Buffer } = require('node:buffer');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = createDecipheriv(algorithm, key, iv);\n\n// Encrypted using same algorithm, key and iv.\nconst encrypted =\n 'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';\nlet decrypted = decipher.update(encrypted, 'hex', 'utf8');\ndecrypted += decipher.final('utf8');\nconsole.log(decrypted);\n// Prints: some clear text data\n
",
"methods": [
{
"textRaw": "`decipher.final([outputEncoding])`",
"type": "method",
"name": "final",
"meta": {
"added": [
"v0.1.94"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string} Any remaining deciphered contents. If `outputEncoding` is specified, a string is returned. If an `outputEncoding` is not provided, a [`Buffer`][] is returned.",
"name": "return",
"type": "Buffer | string",
"desc": "Any remaining deciphered contents. If `outputEncoding` is specified, a string is returned. If an `outputEncoding` is not provided, a [`Buffer`][] is returned."
},
"params": [
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value."
}
]
}
],
"desc": "Once the decipher.final()
method has been called, the Decipher
object can\nno longer be used to decrypt data. Attempts to call decipher.final()
more\nthan once will result in an error being thrown.
When using an authenticated encryption mode (GCM
, CCM
, OCB
, and\nchacha20-poly1305
are\ncurrently supported), the decipher.setAAD()
method sets the value used for the\nadditional authenticated data (AAD) input parameter.
The options
argument is optional for GCM
. When using CCM
, the\nplaintextLength
option must be specified and its value must match the length\nof the ciphertext in bytes. See CCM mode.
The decipher.setAAD()
method must be called before decipher.update()
.
When passing a string as the buffer
, please consider\ncaveats when using strings as inputs to cryptographic APIs.
When using an authenticated encryption mode (GCM
, CCM
, OCB
, and\nchacha20-poly1305
are\ncurrently supported), the decipher.setAuthTag()
method is used to pass in the\nreceived authentication tag. If no tag is provided, or if the cipher text\nhas been tampered with, decipher.final()
will throw, indicating that the\ncipher text should be discarded due to failed authentication. If the tag length\nis invalid according to NIST SP 800-38D or does not match the value of the\nauthTagLength
option, decipher.setAuthTag()
will throw an error.
The decipher.setAuthTag()
method must be called before decipher.update()
\nfor CCM
mode or before decipher.final()
for GCM
and OCB
modes and\nchacha20-poly1305
.\ndecipher.setAuthTag()
can only be called once.
When passing a string as the authentication tag, please consider\ncaveats when using strings as inputs to cryptographic APIs.
" }, { "textRaw": "`decipher.setAutoPadding([autoPadding])`", "type": "method", "name": "setAutoPadding", "meta": { "added": [ "v0.7.1" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Decipher} The same Decipher for method chaining.", "name": "return", "type": "Decipher", "desc": "The same Decipher for method chaining." }, "params": [ { "textRaw": "`autoPadding` {boolean} **Default:** `true`", "name": "autoPadding", "type": "boolean", "default": "`true`" } ] } ], "desc": "When data has been encrypted without standard block padding, calling\ndecipher.setAutoPadding(false)
will disable automatic padding to prevent\ndecipher.final()
from checking for and removing padding.
Turning auto padding off will only work if the input data's length is a\nmultiple of the ciphers block size.
\nThe decipher.setAutoPadding()
method must be called before\ndecipher.final()
.
Updates the decipher with data
. If the inputEncoding
argument is given,\nthe data
\nargument is a string using the specified encoding. If the inputEncoding
\nargument is not given, data
must be a Buffer
. If data
is a\nBuffer
then inputEncoding
is ignored.
The outputEncoding
specifies the output format of the enciphered\ndata. If the outputEncoding
\nis specified, a string using the specified encoding is returned. If no\noutputEncoding
is provided, a Buffer
is returned.
The decipher.update()
method can be called multiple times with new data until\ndecipher.final()
is called. Calling decipher.update()
after\ndecipher.final()
will result in an error being thrown.
The DiffieHellman
class is a utility for creating Diffie-Hellman key\nexchanges.
Instances of the DiffieHellman
class can be created using the\ncrypto.createDiffieHellman()
function.
import assert from 'node:assert';\n\nconst {\n createDiffieHellman,\n} = await import('node:crypto');\n\n// Generate Alice's keys...\nconst alice = createDiffieHellman(2048);\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = createDiffieHellman(alice.getPrime(), alice.getGenerator());\nconst bobKey = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst aliceSecret = alice.computeSecret(bobKey);\nconst bobSecret = bob.computeSecret(aliceKey);\n\n// OK\nassert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));\n
\nconst assert = require('node:assert');\n\nconst {\n createDiffieHellman,\n} = require('node:crypto');\n\n// Generate Alice's keys...\nconst alice = createDiffieHellman(2048);\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = createDiffieHellman(alice.getPrime(), alice.getGenerator());\nconst bobKey = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst aliceSecret = alice.computeSecret(bobKey);\nconst bobSecret = bob.computeSecret(aliceKey);\n\n// OK\nassert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));\n
",
"methods": [
{
"textRaw": "`diffieHellman.computeSecret(otherPublicKey[, inputEncoding][, outputEncoding])`",
"type": "method",
"name": "computeSecret",
"meta": {
"added": [
"v0.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`otherPublicKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "otherPublicKey",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`inputEncoding` {string} The [encoding][] of an `otherPublicKey` string.",
"name": "inputEncoding",
"type": "string",
"desc": "The [encoding][] of an `otherPublicKey` string."
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value."
}
]
}
],
"desc": "Computes the shared secret using otherPublicKey
as the other\nparty's public key and returns the computed shared secret. The supplied\nkey is interpreted using the specified inputEncoding
, and secret is\nencoded using specified outputEncoding
.\nIf the inputEncoding
is not\nprovided, otherPublicKey
is expected to be a Buffer
,\nTypedArray
, or DataView
.
If outputEncoding
is given a string is returned; otherwise, a\nBuffer
is returned.
Generates private and public Diffie-Hellman key values unless they have been\ngenerated or computed already, and returns\nthe public key in the specified encoding
. This key should be\ntransferred to the other party.\nIf encoding
is provided a string is returned; otherwise a\nBuffer
is returned.
This function is a thin wrapper around DH_generate_key()
. In particular,\nonce a private key has been generated or set, calling this function only updates\nthe public key but does not generate a new private key.
Returns the Diffie-Hellman generator in the specified encoding
.\nIf encoding
is provided a string is\nreturned; otherwise a Buffer
is returned.
Returns the Diffie-Hellman prime in the specified encoding
.\nIf encoding
is provided a string is\nreturned; otherwise a Buffer
is returned.
Returns the Diffie-Hellman private key in the specified encoding
.\nIf encoding
is provided a\nstring is returned; otherwise a Buffer
is returned.
Returns the Diffie-Hellman public key in the specified encoding
.\nIf encoding
is provided a\nstring is returned; otherwise a Buffer
is returned.
Sets the Diffie-Hellman private key. If the encoding
argument is provided,\nprivateKey
is expected\nto be a string. If no encoding
is provided, privateKey
is expected\nto be a Buffer
, TypedArray
, or DataView
.
This function does not automatically compute the associated public key. Either\ndiffieHellman.setPublicKey()
or diffieHellman.generateKeys()
can be\nused to manually provide the public key or to automatically derive it.
Sets the Diffie-Hellman public key. If the encoding
argument is provided,\npublicKey
is expected\nto be a string. If no encoding
is provided, publicKey
is expected\nto be a Buffer
, TypedArray
, or DataView
.
A bit field containing any warnings and/or errors resulting from a check\nperformed during initialization of the DiffieHellman
object.
The following values are valid for this property (as defined in node:constants
module):
DH_CHECK_P_NOT_SAFE_PRIME
DH_CHECK_P_NOT_PRIME
DH_UNABLE_TO_CHECK_GENERATOR
DH_NOT_SUITABLE_GENERATOR
The DiffieHellmanGroup
class takes a well-known modp group as its argument.\nIt works the same as DiffieHellman
, except that it does not allow changing\nits keys after creation. In other words, it does not implement setPublicKey()
\nor setPrivateKey()
methods.
const { createDiffieHellmanGroup } = await import('node:crypto');\nconst dh = createDiffieHellmanGroup('modp16');\n
\nconst { createDiffieHellmanGroup } = require('node:crypto');\nconst dh = createDiffieHellmanGroup('modp16');\n
\nThe following groups are supported:
\n'modp14'
(2048 bits, RFC 3526 Section 3)'modp15'
(3072 bits, RFC 3526 Section 4)'modp16'
(4096 bits, RFC 3526 Section 5)'modp17'
(6144 bits, RFC 3526 Section 6)'modp18'
(8192 bits, RFC 3526 Section 7)The following groups are still supported but deprecated (see Caveats):
\n'modp1'
(768 bits, RFC 2409 Section 6.1) 'modp2'
(1024 bits, RFC 2409 Section 6.2) 'modp5'
(1536 bits, RFC 3526 Section 2) These deprecated groups might be removed in future versions of Node.js.
" }, { "textRaw": "Class: `ECDH`", "type": "class", "name": "ECDH", "meta": { "added": [ "v0.11.14" ], "changes": [] }, "desc": "The ECDH
class is a utility for creating Elliptic Curve Diffie-Hellman (ECDH)\nkey exchanges.
Instances of the ECDH
class can be created using the\ncrypto.createECDH()
function.
import assert from 'node:assert';\n\nconst {\n createECDH,\n} = await import('node:crypto');\n\n// Generate Alice's keys...\nconst alice = createECDH('secp521r1');\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = createECDH('secp521r1');\nconst bobKey = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst aliceSecret = alice.computeSecret(bobKey);\nconst bobSecret = bob.computeSecret(aliceKey);\n\nassert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));\n// OK\n
\nconst assert = require('node:assert');\n\nconst {\n createECDH,\n} = require('node:crypto');\n\n// Generate Alice's keys...\nconst alice = createECDH('secp521r1');\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = createECDH('secp521r1');\nconst bobKey = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst aliceSecret = alice.computeSecret(bobKey);\nconst bobSecret = bob.computeSecret(aliceKey);\n\nassert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));\n// OK\n
",
"classMethods": [
{
"textRaw": "Static method: `ECDH.convertKey(key, curve[, inputEncoding[, outputEncoding[, format]]])`",
"type": "classMethod",
"name": "convertKey",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`key` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "key",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`curve` {string}",
"name": "curve",
"type": "string"
},
{
"textRaw": "`inputEncoding` {string} The [encoding][] of the `key` string.",
"name": "inputEncoding",
"type": "string",
"desc": "The [encoding][] of the `key` string."
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value."
},
{
"textRaw": "`format` {string} **Default:** `'uncompressed'`",
"name": "format",
"type": "string",
"default": "`'uncompressed'`"
}
]
}
],
"desc": "Converts the EC Diffie-Hellman public key specified by key
and curve
to the\nformat specified by format
. The format
argument specifies point encoding\nand can be 'compressed'
, 'uncompressed'
or 'hybrid'
. The supplied key is\ninterpreted using the specified inputEncoding
, and the returned key is encoded\nusing the specified outputEncoding
.
Use crypto.getCurves()
to obtain a list of available curve names.\nOn recent OpenSSL releases, openssl ecparam -list_curves
will also display\nthe name and description of each available elliptic curve.
If format
is not specified the point will be returned in 'uncompressed'
\nformat.
If the inputEncoding
is not provided, key
is expected to be a Buffer
,\nTypedArray
, or DataView
.
Example (uncompressing a key):
\nconst {\n createECDH,\n ECDH,\n} = await import('node:crypto');\n\nconst ecdh = createECDH('secp256k1');\necdh.generateKeys();\n\nconst compressedKey = ecdh.getPublicKey('hex', 'compressed');\n\nconst uncompressedKey = ECDH.convertKey(compressedKey,\n 'secp256k1',\n 'hex',\n 'hex',\n 'uncompressed');\n\n// The converted key and the uncompressed public key should be the same\nconsole.log(uncompressedKey === ecdh.getPublicKey('hex'));\n
\nconst {\n createECDH,\n ECDH,\n} = require('node:crypto');\n\nconst ecdh = createECDH('secp256k1');\necdh.generateKeys();\n\nconst compressedKey = ecdh.getPublicKey('hex', 'compressed');\n\nconst uncompressedKey = ECDH.convertKey(compressedKey,\n 'secp256k1',\n 'hex',\n 'hex',\n 'uncompressed');\n\n// The converted key and the uncompressed public key should be the same\nconsole.log(uncompressedKey === ecdh.getPublicKey('hex'));\n
"
}
],
"methods": [
{
"textRaw": "`ecdh.computeSecret(otherPublicKey[, inputEncoding][, outputEncoding])`",
"type": "method",
"name": "computeSecret",
"meta": {
"added": [
"v0.11.14"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/16849",
"description": "Changed error format to better support invalid public key error."
},
{
"version": "v6.0.0",
"pr-url": "https://github.com/nodejs/node/pull/5522",
"description": "The default `inputEncoding` changed from `binary` to `utf8`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`otherPublicKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}",
"name": "otherPublicKey",
"type": "string|ArrayBuffer|Buffer|TypedArray|DataView"
},
{
"textRaw": "`inputEncoding` {string} The [encoding][] of the `otherPublicKey` string.",
"name": "inputEncoding",
"type": "string",
"desc": "The [encoding][] of the `otherPublicKey` string."
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value."
}
]
}
],
"desc": "Computes the shared secret using otherPublicKey
as the other\nparty's public key and returns the computed shared secret. The supplied\nkey is interpreted using specified inputEncoding
, and the returned secret\nis encoded using the specified outputEncoding
.\nIf the inputEncoding
is not\nprovided, otherPublicKey
is expected to be a Buffer
, TypedArray
, or\nDataView
.
If outputEncoding
is given a string will be returned; otherwise a\nBuffer
is returned.
ecdh.computeSecret
will throw an\nERR_CRYPTO_ECDH_INVALID_PUBLIC_KEY
error when otherPublicKey
\nlies outside of the elliptic curve. Since otherPublicKey
is\nusually supplied from a remote user over an insecure network,\nbe sure to handle this exception accordingly.
Generates private and public EC Diffie-Hellman key values, and returns\nthe public key in the specified format
and encoding
. This key should be\ntransferred to the other party.
The format
argument specifies point encoding and can be 'compressed'
or\n'uncompressed'
. If format
is not specified, the point will be returned in\n'uncompressed'
format.
If encoding
is provided a string is returned; otherwise a Buffer
\nis returned.
If encoding
is specified, a string is returned; otherwise a Buffer
is\nreturned.
The format
argument specifies point encoding and can be 'compressed'
or\n'uncompressed'
. If format
is not specified the point will be returned in\n'uncompressed'
format.
If encoding
is specified, a string is returned; otherwise a Buffer
is\nreturned.
Sets the EC Diffie-Hellman private key.\nIf encoding
is provided, privateKey
is expected\nto be a string; otherwise privateKey
is expected to be a Buffer
,\nTypedArray
, or DataView
.
If privateKey
is not valid for the curve specified when the ECDH
object was\ncreated, an error is thrown. Upon setting the private key, the associated\npublic point (key) is also generated and set in the ECDH
object.
Sets the EC Diffie-Hellman public key.\nIf encoding
is provided publicKey
is expected to\nbe a string; otherwise a Buffer
, TypedArray
, or DataView
is expected.
There is not normally a reason to call this method because ECDH
\nonly requires a private key and the other party's public key to compute the\nshared secret. Typically either ecdh.generateKeys()
or\necdh.setPrivateKey()
will be called. The ecdh.setPrivateKey()
method\nattempts to generate the public point/key associated with the private key being\nset.
Example (obtaining a shared secret):
\nconst {\n createECDH,\n createHash,\n} = await import('node:crypto');\n\nconst alice = createECDH('secp256k1');\nconst bob = createECDH('secp256k1');\n\n// This is a shortcut way of specifying one of Alice's previous private\n// keys. It would be unwise to use such a predictable private key in a real\n// application.\nalice.setPrivateKey(\n createHash('sha256').update('alice', 'utf8').digest(),\n);\n\n// Bob uses a newly generated cryptographically strong\n// pseudorandom key pair\nbob.generateKeys();\n\nconst aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n// aliceSecret and bobSecret should be the same shared secret value\nconsole.log(aliceSecret === bobSecret);\n
\nconst {\n createECDH,\n createHash,\n} = require('node:crypto');\n\nconst alice = createECDH('secp256k1');\nconst bob = createECDH('secp256k1');\n\n// This is a shortcut way of specifying one of Alice's previous private\n// keys. It would be unwise to use such a predictable private key in a real\n// application.\nalice.setPrivateKey(\n createHash('sha256').update('alice', 'utf8').digest(),\n);\n\n// Bob uses a newly generated cryptographically strong\n// pseudorandom key pair\nbob.generateKeys();\n\nconst aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n// aliceSecret and bobSecret should be the same shared secret value\nconsole.log(aliceSecret === bobSecret);\n
"
}
]
},
{
"textRaw": "Class: `Hash`",
"type": "class",
"name": "Hash",
"meta": {
"added": [
"v0.1.92"
],
"changes": []
},
"desc": "The Hash
class is a utility for creating hash digests of data. It can be\nused in one of two ways:
hash.update()
and hash.digest()
methods to produce the\ncomputed hash.The crypto.createHash()
method is used to create Hash
instances. Hash
\nobjects are not to be created directly using the new
keyword.
Example: Using Hash
objects as streams:
const {\n createHash,\n} = await import('node:crypto');\n\nconst hash = createHash('sha256');\n\nhash.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = hash.read();\n if (data) {\n console.log(data.toString('hex'));\n // Prints:\n // 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n }\n});\n\nhash.write('some data to hash');\nhash.end();\n
\nconst {\n createHash,\n} = require('node:crypto');\n\nconst hash = createHash('sha256');\n\nhash.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = hash.read();\n if (data) {\n console.log(data.toString('hex'));\n // Prints:\n // 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n }\n});\n\nhash.write('some data to hash');\nhash.end();\n
\nExample: Using Hash
and piped streams:
import { createReadStream } from 'node:fs';\nimport { stdout } from 'node:process';\nconst { createHash } = await import('node:crypto');\n\nconst hash = createHash('sha256');\n\nconst input = createReadStream('test.js');\ninput.pipe(hash).setEncoding('hex').pipe(stdout);\n
\nconst { createReadStream } = require('node:fs');\nconst { createHash } = require('node:crypto');\nconst { stdout } = require('node:process');\n\nconst hash = createHash('sha256');\n\nconst input = createReadStream('test.js');\ninput.pipe(hash).setEncoding('hex').pipe(stdout);\n
\nExample: Using the hash.update()
and hash.digest()
methods:
const {\n createHash,\n} = await import('node:crypto');\n\nconst hash = createHash('sha256');\n\nhash.update('some data to hash');\nconsole.log(hash.digest('hex'));\n// Prints:\n// 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n
\nconst {\n createHash,\n} = require('node:crypto');\n\nconst hash = createHash('sha256');\n\nhash.update('some data to hash');\nconsole.log(hash.digest('hex'));\n// Prints:\n// 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n
",
"methods": [
{
"textRaw": "`hash.copy([options])`",
"type": "method",
"name": "copy",
"meta": {
"added": [
"v13.1.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Hash}",
"name": "return",
"type": "Hash"
},
"params": [
{
"textRaw": "`options` {Object} [`stream.transform` options][]",
"name": "options",
"type": "Object",
"desc": "[`stream.transform` options][]"
}
]
}
],
"desc": "Creates a new Hash
object that contains a deep copy of the internal state\nof the current Hash
object.
The optional options
argument controls stream behavior. For XOF hash\nfunctions such as 'shake256'
, the outputLength
option can be used to\nspecify the desired output length in bytes.
An error is thrown when an attempt is made to copy the Hash
object after\nits hash.digest()
method has been called.
// Calculate a rolling hash.\nconst {\n createHash,\n} = await import('node:crypto');\n\nconst hash = createHash('sha256');\n\nhash.update('one');\nconsole.log(hash.copy().digest('hex'));\n\nhash.update('two');\nconsole.log(hash.copy().digest('hex'));\n\nhash.update('three');\nconsole.log(hash.copy().digest('hex'));\n\n// Etc.\n
\n// Calculate a rolling hash.\nconst {\n createHash,\n} = require('node:crypto');\n\nconst hash = createHash('sha256');\n\nhash.update('one');\nconsole.log(hash.copy().digest('hex'));\n\nhash.update('two');\nconsole.log(hash.copy().digest('hex'));\n\nhash.update('three');\nconsole.log(hash.copy().digest('hex'));\n\n// Etc.\n
"
},
{
"textRaw": "`hash.digest([encoding])`",
"type": "method",
"name": "digest",
"meta": {
"added": [
"v0.1.92"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`encoding` {string} The [encoding][] of the return value.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the return value."
}
]
}
],
"desc": "Calculates the digest of all of the data passed to be hashed (using the\nhash.update()
method).\nIf encoding
is provided a string will be returned; otherwise\na Buffer
is returned.
The Hash
object can not be used again after hash.digest()
method has been\ncalled. Multiple calls will cause an error to be thrown.
Updates the hash content with the given data
, the encoding of which\nis given in inputEncoding
.\nIf encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a Buffer
, TypedArray
, or\nDataView
, then inputEncoding
is ignored.
This can be called many times with new data as it is streamed.
" } ] }, { "textRaw": "Class: `Hmac`", "type": "class", "name": "Hmac", "meta": { "added": [ "v0.1.94" ], "changes": [] }, "desc": "The Hmac
class is a utility for creating cryptographic HMAC digests. It can\nbe used in one of two ways:
hmac.update()
and hmac.digest()
methods to produce the\ncomputed HMAC digest.The crypto.createHmac()
method is used to create Hmac
instances. Hmac
\nobjects are not to be created directly using the new
keyword.
Example: Using Hmac
objects as streams:
const {\n createHmac,\n} = await import('node:crypto');\n\nconst hmac = createHmac('sha256', 'a secret');\n\nhmac.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = hmac.read();\n if (data) {\n console.log(data.toString('hex'));\n // Prints:\n // 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\n }\n});\n\nhmac.write('some data to hash');\nhmac.end();\n
\nconst {\n createHmac,\n} = require('node:crypto');\n\nconst hmac = createHmac('sha256', 'a secret');\n\nhmac.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = hmac.read();\n if (data) {\n console.log(data.toString('hex'));\n // Prints:\n // 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\n }\n});\n\nhmac.write('some data to hash');\nhmac.end();\n
\nExample: Using Hmac
and piped streams:
import { createReadStream } from 'node:fs';\nimport { stdout } from 'node:process';\nconst {\n createHmac,\n} = await import('node:crypto');\n\nconst hmac = createHmac('sha256', 'a secret');\n\nconst input = createReadStream('test.js');\ninput.pipe(hmac).pipe(stdout);\n
\nconst {\n createReadStream,\n} = require('node:fs');\nconst {\n createHmac,\n} = require('node:crypto');\nconst { stdout } = require('node:process');\n\nconst hmac = createHmac('sha256', 'a secret');\n\nconst input = createReadStream('test.js');\ninput.pipe(hmac).pipe(stdout);\n
\nExample: Using the hmac.update()
and hmac.digest()
methods:
const {\n createHmac,\n} = await import('node:crypto');\n\nconst hmac = createHmac('sha256', 'a secret');\n\nhmac.update('some data to hash');\nconsole.log(hmac.digest('hex'));\n// Prints:\n// 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\n
\nconst {\n createHmac,\n} = require('node:crypto');\n\nconst hmac = createHmac('sha256', 'a secret');\n\nhmac.update('some data to hash');\nconsole.log(hmac.digest('hex'));\n// Prints:\n// 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\n
",
"methods": [
{
"textRaw": "`hmac.digest([encoding])`",
"type": "method",
"name": "digest",
"meta": {
"added": [
"v0.1.94"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`encoding` {string} The [encoding][] of the return value.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the return value."
}
]
}
],
"desc": "Calculates the HMAC digest of all of the data passed using hmac.update()
.\nIf encoding
is\nprovided a string is returned; otherwise a Buffer
is returned;
The Hmac
object can not be used again after hmac.digest()
has been\ncalled. Multiple calls to hmac.digest()
will result in an error being thrown.
Updates the Hmac
content with the given data
, the encoding of which\nis given in inputEncoding
.\nIf encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a Buffer
, TypedArray
, or\nDataView
, then inputEncoding
is ignored.
This can be called many times with new data as it is streamed.
" } ] }, { "textRaw": "Class: `KeyObject`", "type": "class", "name": "KeyObject", "meta": { "added": [ "v11.6.0" ], "changes": [ { "version": [ "v14.5.0", "v12.19.0" ], "pr-url": "https://github.com/nodejs/node/pull/33360", "description": "Instances of this class can now be passed to worker threads using `postMessage`." }, { "version": "v11.13.0", "pr-url": "https://github.com/nodejs/node/pull/26438", "description": "This class is now exported." } ] }, "desc": "Node.js uses a KeyObject
class to represent a symmetric or asymmetric key,\nand each kind of key exposes different functions. The\ncrypto.createSecretKey()
, crypto.createPublicKey()
and\ncrypto.createPrivateKey()
methods are used to create KeyObject
\ninstances. KeyObject
objects are not to be created directly using the new
\nkeyword.
Most applications should consider using the new KeyObject
API instead of\npassing keys as strings or Buffer
s due to improved security features.
KeyObject
instances can be passed to other threads via postMessage()
.\nThe receiver obtains a cloned KeyObject
, and the KeyObject
does not need to\nbe listed in the transferList
argument.
Example: Converting a CryptoKey
instance to a KeyObject
:
const { KeyObject } = await import('node:crypto');\nconst { subtle } = globalThis.crypto;\n\nconst key = await subtle.generateKey({\n name: 'HMAC',\n hash: 'SHA-256',\n length: 256,\n}, true, ['sign', 'verify']);\n\nconst keyObject = KeyObject.from(key);\nconsole.log(keyObject.symmetricKeySize);\n// Prints: 32 (symmetric key size in bytes)\n
\nconst { KeyObject } = require('node:crypto');\nconst { subtle } = globalThis.crypto;\n\n(async function() {\n const key = await subtle.generateKey({\n name: 'HMAC',\n hash: 'SHA-256',\n length: 256,\n }, true, ['sign', 'verify']);\n\n const keyObject = KeyObject.from(key);\n console.log(keyObject.symmetricKeySize);\n // Prints: 32 (symmetric key size in bytes)\n})();\n
"
}
],
"properties": [
{
"textRaw": "`asymmetricKeyDetails` {Object}",
"type": "Object",
"name": "asymmetricKeyDetails",
"meta": {
"added": [
"v15.7.0"
],
"changes": [
{
"version": "v16.9.0",
"pr-url": "https://github.com/nodejs/node/pull/39851",
"description": "Expose `RSASSA-PSS-params` sequence parameters for RSA-PSS keys."
}
]
},
"options": [
{
"textRaw": "`modulusLength`: {number} Key size in bits (RSA, DSA).",
"name": "modulusLength",
"type": "number",
"desc": "Key size in bits (RSA, DSA)."
},
{
"textRaw": "`publicExponent`: {bigint} Public exponent (RSA).",
"name": "publicExponent",
"type": "bigint",
"desc": "Public exponent (RSA)."
},
{
"textRaw": "`hashAlgorithm`: {string} Name of the message digest (RSA-PSS).",
"name": "hashAlgorithm",
"type": "string",
"desc": "Name of the message digest (RSA-PSS)."
},
{
"textRaw": "`mgf1HashAlgorithm`: {string} Name of the message digest used by MGF1 (RSA-PSS).",
"name": "mgf1HashAlgorithm",
"type": "string",
"desc": "Name of the message digest used by MGF1 (RSA-PSS)."
},
{
"textRaw": "`saltLength`: {number} Minimal salt length in bytes (RSA-PSS).",
"name": "saltLength",
"type": "number",
"desc": "Minimal salt length in bytes (RSA-PSS)."
},
{
"textRaw": "`divisorLength`: {number} Size of `q` in bits (DSA).",
"name": "divisorLength",
"type": "number",
"desc": "Size of `q` in bits (DSA)."
},
{
"textRaw": "`namedCurve`: {string} Name of the curve (EC).",
"name": "namedCurve",
"type": "string",
"desc": "Name of the curve (EC)."
}
],
"desc": "This property exists only on asymmetric keys. Depending on the type of the key,\nthis object contains information about the key. None of the information obtained\nthrough this property can be used to uniquely identify a key or to compromise\nthe security of the key.
\nFor RSA-PSS keys, if the key material contains a RSASSA-PSS-params
sequence,\nthe hashAlgorithm
, mgf1HashAlgorithm
, and saltLength
properties will be\nset.
Other key details might be exposed via this API using additional attributes.
" }, { "textRaw": "`asymmetricKeyType` {string}", "type": "string", "name": "asymmetricKeyType", "meta": { "added": [ "v11.6.0" ], "changes": [ { "version": [ "v13.9.0", "v12.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/31178", "description": "Added support for `'dh'`." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26960", "description": "Added support for `'rsa-pss'`." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26786", "description": "This property now returns `undefined` for KeyObject instances of unrecognized type instead of aborting." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26774", "description": "Added support for `'x25519'` and `'x448'`." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26319", "description": "Added support for `'ed25519'` and `'ed448'`." } ] }, "desc": "For asymmetric keys, this property represents the type of the key. Supported key\ntypes are:
\n'rsa'
(OID 1.2.840.113549.1.1.1)'rsa-pss'
(OID 1.2.840.113549.1.1.10)'dsa'
(OID 1.2.840.10040.4.1)'ec'
(OID 1.2.840.10045.2.1)'x25519'
(OID 1.3.101.110)'x448'
(OID 1.3.101.111)'ed25519'
(OID 1.3.101.112)'ed448'
(OID 1.3.101.113)'dh'
(OID 1.2.840.113549.1.3.1)This property is undefined
for unrecognized KeyObject
types and symmetric\nkeys.
For secret keys, this property represents the size of the key in bytes. This\nproperty is undefined
for asymmetric keys.
Depending on the type of this KeyObject
, this property is either\n'secret'
for secret (symmetric) keys, 'public'
for public (asymmetric) keys\nor 'private'
for private (asymmetric) keys.
For symmetric keys, the following encoding options can be used:
\nformat
: <string> Must be 'buffer'
(default) or 'jwk'
.For public keys, the following encoding options can be used:
\ntype
: <string> Must be one of 'pkcs1'
(RSA only) or 'spki'
.format
: <string> Must be 'pem'
, 'der'
, or 'jwk'
.For private keys, the following encoding options can be used:
\ntype
: <string> Must be one of 'pkcs1'
(RSA only), 'pkcs8'
or\n'sec1'
(EC only).format
: <string> Must be 'pem'
, 'der'
, or 'jwk'
.cipher
: <string> If specified, the private key will be encrypted with\nthe given cipher
and passphrase
using PKCS#5 v2.0 password based\nencryption.passphrase
: <string> | <Buffer> The passphrase to use for encryption, see\ncipher
.The result type depends on the selected encoding format, when PEM the\nresult is a string, when DER it will be a buffer containing the data\nencoded as DER, when JWK it will be an object.
\nWhen JWK encoding format was selected, all other encoding options are\nignored.
\nPKCS#1, SEC1, and PKCS#8 type keys can be encrypted by using a combination of\nthe cipher
and format
options. The PKCS#8 type
can be used with any\nformat
to encrypt any key algorithm (RSA, EC, or DH) by specifying a\ncipher
. PKCS#1 and SEC1 can only be encrypted by specifying a cipher
\nwhen the PEM format
is used. For maximum compatibility, use PKCS#8 for\nencrypted private keys. Since PKCS#8 defines its own\nencryption mechanism, PEM-level encryption is not supported when encrypting\na PKCS#8 key. See RFC 5208 for PKCS#8 encryption and RFC 1421 for\nPKCS#1 and SEC1 encryption.
Returns true
or false
depending on whether the keys have exactly the same\ntype, value, and parameters. This method is not\nconstant time.
The Sign
class is a utility for generating signatures. It can be used in one\nof two ways:
sign.sign()
method is used to generate and return the signature, orsign.update()
and sign.sign()
methods to produce the\nsignature.The crypto.createSign()
method is used to create Sign
instances. The\nargument is the string name of the hash function to use. Sign
objects are not\nto be created directly using the new
keyword.
Example: Using Sign
and Verify
objects as streams:
const {\n generateKeyPairSync,\n createSign,\n createVerify,\n} = await import('node:crypto');\n\nconst { privateKey, publicKey } = generateKeyPairSync('ec', {\n namedCurve: 'sect239k1',\n});\n\nconst sign = createSign('SHA256');\nsign.write('some data to sign');\nsign.end();\nconst signature = sign.sign(privateKey, 'hex');\n\nconst verify = createVerify('SHA256');\nverify.write('some data to sign');\nverify.end();\nconsole.log(verify.verify(publicKey, signature, 'hex'));\n// Prints: true\n
\nconst {\n generateKeyPairSync,\n createSign,\n createVerify,\n} = require('node:crypto');\n\nconst { privateKey, publicKey } = generateKeyPairSync('ec', {\n namedCurve: 'sect239k1',\n});\n\nconst sign = createSign('SHA256');\nsign.write('some data to sign');\nsign.end();\nconst signature = sign.sign(privateKey, 'hex');\n\nconst verify = createVerify('SHA256');\nverify.write('some data to sign');\nverify.end();\nconsole.log(verify.verify(publicKey, signature, 'hex'));\n// Prints: true\n
\nExample: Using the sign.update()
and verify.update()
methods:
const {\n generateKeyPairSync,\n createSign,\n createVerify,\n} = await import('node:crypto');\n\nconst { privateKey, publicKey } = generateKeyPairSync('rsa', {\n modulusLength: 2048,\n});\n\nconst sign = createSign('SHA256');\nsign.update('some data to sign');\nsign.end();\nconst signature = sign.sign(privateKey);\n\nconst verify = createVerify('SHA256');\nverify.update('some data to sign');\nverify.end();\nconsole.log(verify.verify(publicKey, signature));\n// Prints: true\n
\nconst {\n generateKeyPairSync,\n createSign,\n createVerify,\n} = require('node:crypto');\n\nconst { privateKey, publicKey } = generateKeyPairSync('rsa', {\n modulusLength: 2048,\n});\n\nconst sign = createSign('SHA256');\nsign.update('some data to sign');\nsign.end();\nconst signature = sign.sign(privateKey);\n\nconst verify = createVerify('SHA256');\nverify.update('some data to sign');\nverify.end();\nconsole.log(verify.verify(publicKey, signature));\n// Prints: true\n
",
"methods": [
{
"textRaw": "`sign.sign(privateKey[, outputEncoding])`",
"type": "method",
"name": "sign",
"meta": {
"added": [
"v0.1.92"
],
"changes": [
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/35093",
"description": "The privateKey can also be an ArrayBuffer and CryptoKey."
},
{
"version": [
"v13.2.0",
"v12.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/29292",
"description": "This function now supports IEEE-P1363 DSA and ECDSA signatures."
},
{
"version": "v12.0.0",
"pr-url": "https://github.com/nodejs/node/pull/26960",
"description": "This function now supports RSA-PSS keys."
},
{
"version": "v11.6.0",
"pr-url": "https://github.com/nodejs/node/pull/24234",
"description": "This function now supports key objects."
},
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/11705",
"description": "Support for RSASSA-PSS and additional options was added."
}
]
},
"signatures": [
{
"params": []
}
],
"desc": "\nprivateKey
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\n\noutputEncoding
<string> The encoding of the return value.Calculates the signature on all the data passed through using either\nsign.update()
or sign.write()
.
If privateKey
is not a KeyObject
, this function behaves as if\nprivateKey
had been passed to crypto.createPrivateKey()
. If it is an\nobject, the following additional properties can be passed:
dsaEncoding
<string> For DSA and ECDSA, this option specifies the\nformat of the generated signature. It can be one of the following:
'der'
(default): DER-encoded ASN.1 signature structure encoding (r, s)
.'ieee-p1363'
: Signature format r || s
as proposed in IEEE-P1363.padding
<integer> Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING
(default)crypto.constants.RSA_PKCS1_PSS_PADDING
RSA_PKCS1_PSS_PADDING
will use MGF1 with the same hash function\nused to sign the message as specified in section 3.1 of RFC 4055, unless\nan MGF1 hash function has been specified as part of the key in compliance with\nsection 3.3 of RFC 4055.
saltLength
<integer> Salt length for when padding is\nRSA_PKCS1_PSS_PADDING
. The special value\ncrypto.constants.RSA_PSS_SALTLEN_DIGEST
sets the salt length to the digest\nsize, crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN
(default) sets it to the\nmaximum permissible value.
If outputEncoding
is provided a string is returned; otherwise a Buffer
\nis returned.
The Sign
object can not be again used after sign.sign()
method has been\ncalled. Multiple calls to sign.sign()
will result in an error being thrown.
Updates the Sign
content with the given data
, the encoding of which\nis given in inputEncoding
.\nIf encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a Buffer
, TypedArray
, or\nDataView
, then inputEncoding
is ignored.
This can be called many times with new data as it is streamed.
" } ] }, { "textRaw": "Class: `Verify`", "type": "class", "name": "Verify", "meta": { "added": [ "v0.1.92" ], "changes": [] }, "desc": "The Verify
class is a utility for verifying signatures. It can be used in one\nof two ways:
verify.update()
and verify.verify()
methods to verify\nthe signature.The crypto.createVerify()
method is used to create Verify
instances.\nVerify
objects are not to be created directly using the new
keyword.
See Sign
for examples.
Updates the Verify
content with the given data
, the encoding of which\nis given in inputEncoding
.\nIf inputEncoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a Buffer
, TypedArray
, or\nDataView
, then inputEncoding
is ignored.
This can be called many times with new data as it is streamed.
" }, { "textRaw": "`verify.verify(object, signature[, signatureEncoding])`", "type": "method", "name": "verify", "meta": { "added": [ "v0.1.92" ], "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/35093", "description": "The object can also be an ArrayBuffer and CryptoKey." }, { "version": [ "v13.2.0", "v12.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/29292", "description": "This function now supports IEEE-P1363 DSA and ECDSA signatures." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26960", "description": "This function now supports RSA-PSS keys." }, { "version": "v11.7.0", "pr-url": "https://github.com/nodejs/node/pull/25217", "description": "The key can now be a private key." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11705", "description": "Support for RSASSA-PSS and additional options was added." } ] }, "signatures": [ { "params": [] } ], "desc": "\nobject
<Object> | <string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView> | <KeyObject> | <CryptoKey>\n\nsignature
<string> | <ArrayBuffer> | <Buffer> | <TypedArray> | <DataView>signatureEncoding
<string> The encoding of the signature
string.true
or false
depending on the validity of the\nsignature for the data and public key.Verifies the provided data using the given object
and signature
.
If object
is not a KeyObject
, this function behaves as if\nobject
had been passed to crypto.createPublicKey()
. If it is an\nobject, the following additional properties can be passed:
dsaEncoding
<string> For DSA and ECDSA, this option specifies the\nformat of the signature. It can be one of the following:
'der'
(default): DER-encoded ASN.1 signature structure encoding (r, s)
.'ieee-p1363'
: Signature format r || s
as proposed in IEEE-P1363.padding
<integer> Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING
(default)crypto.constants.RSA_PKCS1_PSS_PADDING
RSA_PKCS1_PSS_PADDING
will use MGF1 with the same hash function\nused to verify the message as specified in section 3.1 of RFC 4055, unless\nan MGF1 hash function has been specified as part of the key in compliance with\nsection 3.3 of RFC 4055.
saltLength
<integer> Salt length for when padding is\nRSA_PKCS1_PSS_PADDING
. The special value\ncrypto.constants.RSA_PSS_SALTLEN_DIGEST
sets the salt length to the digest\nsize, crypto.constants.RSA_PSS_SALTLEN_AUTO
(default) causes it to be\ndetermined automatically.
The signature
argument is the previously calculated signature for the data, in\nthe signatureEncoding
.\nIf a signatureEncoding
is specified, the signature
is expected to be a\nstring; otherwise signature
is expected to be a Buffer
,\nTypedArray
, or DataView
.
The verify
object can not be used again after verify.verify()
has been\ncalled. Multiple calls to verify.verify()
will result in an error being\nthrown.
Because public keys can be derived from private keys, a private key may\nbe passed instead of a public key.
" } ] }, { "textRaw": "Class: `X509Certificate`", "type": "class", "name": "X509Certificate", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "desc": "Encapsulates an X509 certificate and provides read-only access to\nits information.
\nconst { X509Certificate } = await import('node:crypto');\n\nconst x509 = new X509Certificate('{... pem encoded cert ...}');\n\nconsole.log(x509.subject);\n
\nconst { X509Certificate } = require('node:crypto');\n\nconst x509 = new X509Certificate('{... pem encoded cert ...}');\n\nconsole.log(x509.subject);\n
",
"properties": [
{
"textRaw": "`ca` Type: {boolean} Will be `true` if this is a Certificate Authority (CA) certificate.",
"type": "boolean",
"name": "Type",
"meta": {
"added": [
"v15.6.0"
],
"changes": []
},
"desc": "Will be `true` if this is a Certificate Authority (CA) certificate."
},
{
"textRaw": "`fingerprint` Type: {string}",
"type": "string",
"name": "Type",
"meta": {
"added": [
"v15.6.0"
],
"changes": []
},
"desc": "The SHA-1 fingerprint of this certificate.
\nBecause SHA-1 is cryptographically broken and because the security of SHA-1 is\nsignificantly worse than that of algorithms that are commonly used to sign\ncertificates, consider using x509.fingerprint256
instead.
The SHA-256 fingerprint of this certificate.
" }, { "textRaw": "`fingerprint512` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v17.2.0", "v16.14.0" ], "changes": [] }, "desc": "The SHA-512 fingerprint of this certificate.
\nBecause computing the SHA-256 fingerprint is usually faster and because it is\nonly half the size of the SHA-512 fingerprint, x509.fingerprint256
may be\na better choice. While SHA-512 presumably provides a higher level of security in\ngeneral, the security of SHA-256 matches that of most algorithms that are\ncommonly used to sign certificates.
A textual representation of the certificate's authority information access\nextension.
\nThis is a line feed separated list of access descriptions. Each line begins with\nthe access method and the kind of the access location, followed by a colon and\nthe value associated with the access location.
\nAfter the prefix denoting the access method and the kind of the access location,\nthe remainder of each line might be enclosed in quotes to indicate that the\nvalue is a JSON string literal. For backward compatibility, Node.js only uses\nJSON string literals within this property when necessary to avoid ambiguity.\nThird-party code should be prepared to handle both possible entry formats.
" }, { "textRaw": "`issuer` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "desc": "The issuer identification included in this certificate.
" }, { "textRaw": "`issuerCertificate` Type: {X509Certificate}", "type": "X509Certificate", "name": "Type", "meta": { "added": [ "v15.9.0" ], "changes": [] }, "desc": "The issuer certificate or undefined
if the issuer certificate is not\navailable.
An array detailing the key extended usages for this certificate.
" }, { "textRaw": "`publicKey` Type: {KeyObject}", "type": "KeyObject", "name": "Type", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "desc": "The public key <KeyObject> for this certificate.
" }, { "textRaw": "`raw` Type: {Buffer}", "type": "Buffer", "name": "Type", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "desc": "A Buffer
containing the DER encoding of this certificate.
The serial number of this certificate.
\nSerial numbers are assigned by certificate authorities and do not uniquely\nidentify certificates. Consider using x509.fingerprint256
as a unique\nidentifier instead.
The complete subject of this certificate.
" }, { "textRaw": "`subjectAltName` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v15.6.0" ], "changes": [ { "version": [ "v17.3.1", "v16.13.2" ], "pr-url": "https://github.com/nodejs-private/node-private/pull/300", "description": "Parts of this string may be encoded as JSON string literals in response to CVE-2021-44532." } ] }, "desc": "The subject alternative name specified for this certificate.
\nThis is a comma-separated list of subject alternative names. Each entry begins\nwith a string identifying the kind of the subject alternative name followed by\na colon and the value associated with the entry.
\nEarlier versions of Node.js incorrectly assumed that it is safe to split this\nproperty at the two-character sequence ', '
(see CVE-2021-44532). However,\nboth malicious and legitimate certificates can contain subject alternative names\nthat include this sequence when represented as a string.
After the prefix denoting the type of the entry, the remainder of each entry\nmight be enclosed in quotes to indicate that the value is a JSON string literal.\nFor backward compatibility, Node.js only uses JSON string literals within this\nproperty when necessary to avoid ambiguity. Third-party code should be prepared\nto handle both possible entry formats.
" }, { "textRaw": "`validFrom` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "desc": "The date/time from which this certificate is valid.
" }, { "textRaw": "`validTo` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "desc": "The date/time until which this certificate is valid.
" } ], "methods": [ { "textRaw": "`x509.checkEmail(email[, options])`", "type": "method", "name": "checkEmail", "meta": { "added": [ "v15.6.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41600", "description": "The subject option now defaults to `'default'`." }, { "version": [ "v17.5.0", "v16.14.1" ], "pr-url": "https://github.com/nodejs/node/pull/41599", "description": "The `wildcards`, `partialWildcards`, `multiLabelWildcards`, and `singleLabelSubdomains` options have been removed since they had no effect." }, { "version": [ "v17.5.0", "v16.15.0" ], "pr-url": "https://github.com/nodejs/node/pull/41569", "description": "The subject option can now be set to `'default'`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {string|undefined} Returns `email` if the certificate matches, `undefined` if it does not.", "name": "return", "type": "string|undefined", "desc": "Returns `email` if the certificate matches, `undefined` if it does not." }, "params": [ { "textRaw": "`email` {string}", "name": "email", "type": "string" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`subject` {string} `'default'`, `'always'`, or `'never'`. **Default:** `'default'`.", "name": "subject", "type": "string", "default": "`'default'`", "desc": "`'default'`, `'always'`, or `'never'`." } ] } ] } ], "desc": "Checks whether the certificate matches the given email address.
\nIf the 'subject'
option is undefined or set to 'default'
, the certificate\nsubject is only considered if the subject alternative name extension either does\nnot exist or does not contain any email addresses.
If the 'subject'
option is set to 'always'
and if the subject alternative\nname extension either does not exist or does not contain a matching email\naddress, the certificate subject is considered.
If the 'subject'
option is set to 'never'
, the certificate subject is never\nconsidered, even if the certificate contains no subject alternative names.
Checks whether the certificate matches the given host name.
\nIf the certificate matches the given host name, the matching subject name is\nreturned. The returned name might be an exact match (e.g., foo.example.com
)\nor it might contain wildcards (e.g., *.example.com
). Because host name\ncomparisons are case-insensitive, the returned subject name might also differ\nfrom the given name
in capitalization.
If the 'subject'
option is undefined or set to 'default'
, the certificate\nsubject is only considered if the subject alternative name extension either does\nnot exist or does not contain any DNS names. This behavior is consistent with\nRFC 2818 (\"HTTP Over TLS\").
If the 'subject'
option is set to 'always'
and if the subject alternative\nname extension either does not exist or does not contain a matching DNS name,\nthe certificate subject is considered.
If the 'subject'
option is set to 'never'
, the certificate subject is never\nconsidered, even if the certificate contains no subject alternative names.
Checks whether the certificate matches the given IP address (IPv4 or IPv6).
\nOnly RFC 5280 iPAddress
subject alternative names are considered, and they\nmust match the given ip
address exactly. Other subject alternative names as\nwell as the subject field of the certificate are ignored.
Checks whether this certificate was issued by the given otherCert
.
Checks whether the public key for this certificate is consistent with\nthe given private key.
" }, { "textRaw": "`x509.toJSON()`", "type": "method", "name": "toJSON", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "Type: {string}", "name": "Type", "type": "string" } ] } ], "desc": "There is no standard JSON encoding for X509 certificates. The\ntoJSON()
method returns a string containing the PEM encoded\ncertificate.
Returns information about this certificate using the legacy\ncertificate object encoding.
" }, { "textRaw": "`x509.toString()`", "type": "method", "name": "toString", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "Type: {string}", "name": "Type", "type": "string" } ] } ], "desc": "Returns the PEM-encoded certificate.
" }, { "textRaw": "`x509.verify(publicKey)`", "type": "method", "name": "verify", "meta": { "added": [ "v15.6.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`publicKey` {KeyObject} A public key.", "name": "publicKey", "type": "KeyObject", "desc": "A public key." } ] } ], "desc": "Verifies that this certificate was signed by the given public key.\nDoes not perform any other validation checks on the certificate.
" } ], "signatures": [ { "params": [ { "textRaw": "`buffer` {string|TypedArray|Buffer|DataView} A PEM or DER encoded X509 Certificate.", "name": "buffer", "type": "string|TypedArray|Buffer|DataView", "desc": "A PEM or DER encoded X509 Certificate." } ] } ] } ], "type": "module", "displayName": "Crypto", "source": "doc/api/crypto.md" }, { "textRaw": "Diagnostics Channel", "name": "diagnostics_channel", "meta": { "added": [ "v15.1.0", "v14.17.0" ], "changes": [ { "version": [ "v19.2.0", "v18.13.0" ], "pr-url": "https://github.com/nodejs/node/pull/45290", "description": "diagnostics_channel is now Stable." } ] }, "introduced_in": "v15.1.0", "stability": 2, "stabilityText": "Stable", "desc": "Source Code: lib/diagnostics_channel.js
\nThe node:diagnostics_channel
module provides an API to create named channels\nto report arbitrary message data for diagnostics purposes.
It can be accessed using:
\nimport diagnostics_channel from 'node:diagnostics_channel';\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n
\nIt is intended that a module writer wanting to report diagnostics messages\nwill create one or many top-level channels to report messages through.\nChannels may also be acquired at runtime but it is not encouraged\ndue to the additional overhead of doing so. Channels may be exported for\nconvenience, but as long as the name is known it can be acquired anywhere.
\nIf you intend for your module to produce diagnostics data for others to\nconsume it is recommended that you include documentation of what named\nchannels are used along with the shape of the message data. Channel names\nshould generally include the module name to avoid collisions with data from\nother modules.
", "modules": [ { "textRaw": "Public API", "name": "public_api", "modules": [ { "textRaw": "Overview", "name": "overview", "desc": "Following is a simple overview of the public API.
\nimport diagnostics_channel from 'node:diagnostics_channel';\n\n// Get a reusable channel object\nconst channel = diagnostics_channel.channel('my-channel');\n\nfunction onMessage(message, name) {\n // Received data\n}\n\n// Subscribe to the channel\ndiagnostics_channel.subscribe('my-channel', onMessage);\n\n// Check if the channel has an active subscriber\nif (channel.hasSubscribers) {\n // Publish data to the channel\n channel.publish({\n some: 'data',\n });\n}\n\n// Unsubscribe from the channel\ndiagnostics_channel.unsubscribe('my-channel', onMessage);\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\n// Get a reusable channel object\nconst channel = diagnostics_channel.channel('my-channel');\n\nfunction onMessage(message, name) {\n // Received data\n}\n\n// Subscribe to the channel\ndiagnostics_channel.subscribe('my-channel', onMessage);\n\n// Check if the channel has an active subscriber\nif (channel.hasSubscribers) {\n // Publish data to the channel\n channel.publish({\n some: 'data',\n });\n}\n\n// Unsubscribe from the channel\ndiagnostics_channel.unsubscribe('my-channel', onMessage);\n
",
"methods": [
{
"textRaw": "`diagnostics_channel.hasSubscribers(name)`",
"type": "method",
"name": "hasSubscribers",
"meta": {
"added": [
"v15.1.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} If there are active subscribers",
"name": "return",
"type": "boolean",
"desc": "If there are active subscribers"
},
"params": [
{
"textRaw": "`name` {string|symbol} The channel name",
"name": "name",
"type": "string|symbol",
"desc": "The channel name"
}
]
}
],
"desc": "Check if there are active subscribers to the named channel. This is helpful if\nthe message you want to send might be expensive to prepare.
\nThis API is optional but helpful when trying to publish messages from very\nperformance-sensitive code.
\nimport diagnostics_channel from 'node:diagnostics_channel';\n\nif (diagnostics_channel.hasSubscribers('my-channel')) {\n // There are subscribers, prepare and publish message\n}\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nif (diagnostics_channel.hasSubscribers('my-channel')) {\n // There are subscribers, prepare and publish message\n}\n
"
},
{
"textRaw": "`diagnostics_channel.channel(name)`",
"type": "method",
"name": "channel",
"meta": {
"added": [
"v15.1.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Channel} The named channel object",
"name": "return",
"type": "Channel",
"desc": "The named channel object"
},
"params": [
{
"textRaw": "`name` {string|symbol} The channel name",
"name": "name",
"type": "string|symbol",
"desc": "The channel name"
}
]
}
],
"desc": "This is the primary entry-point for anyone wanting to publish to a named\nchannel. It produces a channel object which is optimized to reduce overhead at\npublish time as much as possible.
\nimport diagnostics_channel from 'node:diagnostics_channel';\n\nconst channel = diagnostics_channel.channel('my-channel');\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channel = diagnostics_channel.channel('my-channel');\n
"
},
{
"textRaw": "`diagnostics_channel.subscribe(name, onMessage)`",
"type": "method",
"name": "subscribe",
"meta": {
"added": [
"v18.7.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string|symbol} The channel name",
"name": "name",
"type": "string|symbol",
"desc": "The channel name"
},
{
"textRaw": "`onMessage` {Function} The handler to receive channel messages",
"name": "onMessage",
"type": "Function",
"desc": "The handler to receive channel messages",
"options": [
{
"textRaw": "`message` {any} The message data",
"name": "message",
"type": "any",
"desc": "The message data"
},
{
"textRaw": "`name` {string|symbol} The name of the channel",
"name": "name",
"type": "string|symbol",
"desc": "The name of the channel"
}
]
}
]
}
],
"desc": "Register a message handler to subscribe to this channel. This message handler\nwill be run synchronously whenever a message is published to the channel. Any\nerrors thrown in the message handler will trigger an 'uncaughtException'
.
import diagnostics_channel from 'node:diagnostics_channel';\n\ndiagnostics_channel.subscribe('my-channel', (message, name) => {\n // Received data\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\ndiagnostics_channel.subscribe('my-channel', (message, name) => {\n // Received data\n});\n
"
},
{
"textRaw": "`diagnostics_channel.unsubscribe(name, onMessage)`",
"type": "method",
"name": "unsubscribe",
"meta": {
"added": [
"v18.7.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if the handler was found, `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if the handler was found, `false` otherwise."
},
"params": [
{
"textRaw": "`name` {string|symbol} The channel name",
"name": "name",
"type": "string|symbol",
"desc": "The channel name"
},
{
"textRaw": "`onMessage` {Function} The previous subscribed handler to remove",
"name": "onMessage",
"type": "Function",
"desc": "The previous subscribed handler to remove"
}
]
}
],
"desc": "Remove a message handler previously registered to this channel with\ndiagnostics_channel.subscribe(name, onMessage)
.
import diagnostics_channel from 'node:diagnostics_channel';\n\nfunction onMessage(message, name) {\n // Received data\n}\n\ndiagnostics_channel.subscribe('my-channel', onMessage);\n\ndiagnostics_channel.unsubscribe('my-channel', onMessage);\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nfunction onMessage(message, name) {\n // Received data\n}\n\ndiagnostics_channel.subscribe('my-channel', onMessage);\n\ndiagnostics_channel.unsubscribe('my-channel', onMessage);\n
"
},
{
"textRaw": "`diagnostics_channel.tracingChannel(nameOrChannels)`",
"type": "method",
"name": "tracingChannel",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {TracingChannel} Collection of channels to trace with",
"name": "return",
"type": "TracingChannel",
"desc": "Collection of channels to trace with"
},
"params": [
{
"textRaw": "`nameOrChannels` {string|TracingChannel} Channel name or object containing all the [TracingChannel Channels][]",
"name": "nameOrChannels",
"type": "string|TracingChannel",
"desc": "Channel name or object containing all the [TracingChannel Channels][]"
}
]
}
],
"desc": "Creates a TracingChannel
wrapper for the given\nTracingChannel Channels. If a name is given, the corresponding tracing\nchannels will be created in the form of tracing:${name}:${eventType}
where\neventType
corresponds to the types of TracingChannel Channels.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channelsByName = diagnostics_channel.tracingChannel('my-channel');\n\n// or...\n\nconst channelsByCollection = diagnostics_channel.tracingChannel({\n start: diagnostics_channel.channel('tracing:my-channel:start'),\n end: diagnostics_channel.channel('tracing:my-channel:end'),\n asyncStart: diagnostics_channel.channel('tracing:my-channel:asyncStart'),\n asyncEnd: diagnostics_channel.channel('tracing:my-channel:asyncEnd'),\n error: diagnostics_channel.channel('tracing:my-channel:error'),\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channelsByName = diagnostics_channel.tracingChannel('my-channel');\n\n// or...\n\nconst channelsByCollection = diagnostics_channel.tracingChannel({\n start: diagnostics_channel.channel('tracing:my-channel:start'),\n end: diagnostics_channel.channel('tracing:my-channel:end'),\n asyncStart: diagnostics_channel.channel('tracing:my-channel:asyncStart'),\n asyncEnd: diagnostics_channel.channel('tracing:my-channel:asyncEnd'),\n error: diagnostics_channel.channel('tracing:my-channel:error'),\n});\n
"
}
],
"type": "module",
"displayName": "Overview"
},
{
"textRaw": "TracingChannel Channels",
"name": "tracingchannel_channels",
"desc": "A TracingChannel is a collection of several diagnostics_channels representing\nspecific points in the execution lifecycle of a single traceable action. The\nbehavior is split into five diagnostics_channels consisting of start
,\nend
, asyncStart
, asyncEnd
, and error
. A single traceable action will\nshare the same event object between all events, this can be helpful for\nmanaging correlation through a weakmap.
These event objects will be extended with result
or error
values when\nthe task \"completes\". In the case of a synchronous task the result
will be\nthe return value and the error
will be anything thrown from the function.\nWith callback-based async functions the result
will be the second argument\nof the callback while the error
will either be a thrown error visible in the\nend
event or the first callback argument in either of the asyncStart
or\nasyncEnd
events.
Tracing channels should follow a naming pattern of:
\ntracing:module.class.method:start
or tracing:module.function:start
tracing:module.class.method:end
or tracing:module.function:end
tracing:module.class.method:asyncStart
or tracing:module.function:asyncStart
tracing:module.class.method:asyncEnd
or tracing:module.function:asyncEnd
tracing:module.class.method:error
or tracing:module.function:error
The start
event represents the point at which a function is called. At this\npoint the event data may contain function arguments or anything else available\nat the very start of the execution of the function.
The end
event represents the point at which a function call returns a value.\nIn the case of an async function this is when the promise returned not when the\nfunction itself makes a return statement internally. At this point, if the\ntraced function was synchronous the result
field will be set to the return\nvalue of the function. Alternatively, the error
field may be present to\nrepresent any thrown errors.
It is recommended to listen specifically to the error
event to track errors\nas it may be possible for a traceable action to produce multiple errors. For\nexample, an async task which fails may be started internally before the sync\npart of the task then throws an error.
The asyncStart
event represents the callback or continuation of a traceable\nfunction being reached. At this point things like callback arguments may be\navailable, or anything else expressing the \"result\" of the action.
For callbacks-based functions, the first argument of the callback will be\nassigned to the error
field, if not undefined
or null
, and the second\nargument will be assigned to the result
field.
For promises, the argument to the resolve
path will be assigned to result
\nor the argument to the reject
path will be assign to error
.
It is recommended to listen specifically to the error
event to track errors\nas it may be possible for a traceable action to produce multiple errors. For\nexample, an async task which fails may be started internally before the sync\npart of the task then throws an error.
The asyncEnd
event represents the callback of an asynchronous function\nreturning. It's not likely event data will change after the asyncStart
event,\nhowever it may be useful to see the point where the callback completes.
The error
event represents any error produced by the traceable function\neither synchronously or asynchronously. If an error is thrown in the\nsynchronous portion of the traced function the error will be assigned to the\nerror
field of the event and the error
event will be triggered. If an error\nis received asynchronously through a callback or promise rejection it will also\nbe assigned to the error
field of the event and trigger the error
event.
It is possible for a single traceable function call to produce errors multiple\ntimes so this should be considered when consuming this event. For example, if\nanother async task is triggered internally which fails and then the sync part\nof the function then throws and error two error
events will be emitted, one\nfor the sync error and one for the async error.
While the diagnostics_channel API is now considered stable, the built-in\nchannels currently available are not. Each channel must be declared stable\nindependently.
", "modules": [ { "textRaw": "HTTP", "name": "http", "desc": "http.client.request.start
request
<http.ClientRequest>Emitted when client starts a request.
\nhttp.client.response.finish
request
<http.ClientRequest>response
<http.IncomingMessage>Emitted when client receives a response.
\nhttp.server.request.start
request
<http.IncomingMessage>response
<http.ServerResponse>socket
<net.Socket>server
<http.Server>Emitted when server receives a request.
\nhttp.server.response.finish
request
<http.IncomingMessage>response
<http.ServerResponse>socket
<net.Socket>server
<http.Server>Emitted when server sends a response.
", "type": "module", "displayName": "HTTP" }, { "textRaw": "NET", "name": "net", "desc": "net.client.socket
socket
<net.Socket>Emitted when a new TCP or pipe client socket is created.
\nnet.server.socket
socket
<net.Socket>Emitted when a new TCP or pipe connection is received.
", "type": "module", "displayName": "NET" }, { "textRaw": "UDP", "name": "udp", "desc": "udp.socket
socket
<dgram.Socket>Emitted when a new UDP socket is created.
", "type": "module", "displayName": "UDP" }, { "textRaw": "Process", "name": "process", "meta": { "added": [ "v16.18.0" ], "changes": [] }, "desc": "child_process
process
<ChildProcess>Emitted when a new process is created.
", "type": "module", "displayName": "Process" }, { "textRaw": "Worker Thread", "name": "worker_thread", "meta": { "added": [ "v16.18.0" ], "changes": [] }, "desc": "worker_threads
worker
Worker
Emitted when a new thread is created.
", "type": "module", "displayName": "Worker Thread" } ], "type": "module", "displayName": "Built-in Channels" } ], "classes": [ { "textRaw": "Class: `Channel`", "type": "class", "name": "Channel", "meta": { "added": [ "v15.1.0", "v14.17.0" ], "changes": [] }, "desc": "The class Channel
represents an individual named channel within the data\npipeline. It is used to track subscribers and to publish messages when there\nare subscribers present. It exists as a separate object to avoid channel\nlookups at publish time, enabling very fast publish speeds and allowing\nfor heavy use while incurring very minimal cost. Channels are created with\ndiagnostics_channel.channel(name)
, constructing a channel directly\nwith new Channel(name)
is not supported.
Check if there are active subscribers to this channel. This is helpful if\nthe message you want to send might be expensive to prepare.
\nThis API is optional but helpful when trying to publish messages from very\nperformance-sensitive code.
\nimport diagnostics_channel from 'node:diagnostics_channel';\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nif (channel.hasSubscribers) {\n // There are subscribers, prepare and publish message\n}\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nif (channel.hasSubscribers) {\n // There are subscribers, prepare and publish message\n}\n
",
"shortDesc": "If there are active subscribers"
}
],
"methods": [
{
"textRaw": "`channel.publish(message)`",
"type": "method",
"name": "publish",
"meta": {
"added": [
"v15.1.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`message` {any} The message to send to the channel subscribers",
"name": "message",
"type": "any",
"desc": "The message to send to the channel subscribers"
}
]
}
],
"desc": "Publish a message to any subscribers to the channel. This will trigger\nmessage handlers synchronously so they will execute within the same context.
\nimport diagnostics_channel from 'node:diagnostics_channel';\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.publish({\n some: 'message',\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.publish({\n some: 'message',\n});\n
"
},
{
"textRaw": "`channel.subscribe(onMessage)`",
"type": "method",
"name": "subscribe",
"meta": {
"added": [
"v15.1.0",
"v14.17.0"
],
"deprecated": [
"v18.7.0",
"v16.17.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`diagnostics_channel.subscribe(name, onMessage)`][]",
"signatures": [
{
"params": [
{
"textRaw": "`onMessage` {Function} The handler to receive channel messages",
"name": "onMessage",
"type": "Function",
"desc": "The handler to receive channel messages",
"options": [
{
"textRaw": "`message` {any} The message data",
"name": "message",
"type": "any",
"desc": "The message data"
},
{
"textRaw": "`name` {string|symbol} The name of the channel",
"name": "name",
"type": "string|symbol",
"desc": "The name of the channel"
}
]
}
]
}
],
"desc": "Register a message handler to subscribe to this channel. This message handler\nwill be run synchronously whenever a message is published to the channel. Any\nerrors thrown in the message handler will trigger an 'uncaughtException'
.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.subscribe((message, name) => {\n // Received data\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.subscribe((message, name) => {\n // Received data\n});\n
"
},
{
"textRaw": "`channel.unsubscribe(onMessage)`",
"type": "method",
"name": "unsubscribe",
"meta": {
"added": [
"v15.1.0",
"v14.17.0"
],
"deprecated": [
"v18.7.0",
"v16.17.0"
],
"changes": [
{
"version": [
"v17.1.0",
"v16.14.0",
"v14.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40433",
"description": "Added return value. Added to channels without subscribers."
}
]
},
"stability": 0,
"stabilityText": "Deprecated: Use [`diagnostics_channel.unsubscribe(name, onMessage)`][]",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if the handler was found, `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if the handler was found, `false` otherwise."
},
"params": [
{
"textRaw": "`onMessage` {Function} The previous subscribed handler to remove",
"name": "onMessage",
"type": "Function",
"desc": "The previous subscribed handler to remove"
}
]
}
],
"desc": "Remove a message handler previously registered to this channel with\nchannel.subscribe(onMessage)
.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nfunction onMessage(message, name) {\n // Received data\n}\n\nchannel.subscribe(onMessage);\n\nchannel.unsubscribe(onMessage);\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nfunction onMessage(message, name) {\n // Received data\n}\n\nchannel.subscribe(onMessage);\n\nchannel.unsubscribe(onMessage);\n
"
},
{
"textRaw": "`channel.bindStore(store[, transform])`",
"type": "method",
"name": "bindStore",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": [
{
"textRaw": "`store` {AsyncLocalStorage} The store to which to bind the context data",
"name": "store",
"type": "AsyncLocalStorage",
"desc": "The store to which to bind the context data"
},
{
"textRaw": "`transform` {Function} Transform context data before setting the store context",
"name": "transform",
"type": "Function",
"desc": "Transform context data before setting the store context"
}
]
}
],
"desc": "When channel.runStores(context, ...)
is called, the given context data\nwill be applied to any store bound to the channel. If the store has already been\nbound the previous transform
function will be replaced with the new one.\nThe transform
function may be omitted to set the given context data as the\ncontext directly.
import diagnostics_channel from 'node:diagnostics_channel';\nimport { AsyncLocalStorage } from 'node:async_hooks';\n\nconst store = new AsyncLocalStorage();\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.bindStore(store, (data) => {\n return { data };\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\nconst { AsyncLocalStorage } = require('node:async_hooks');\n\nconst store = new AsyncLocalStorage();\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.bindStore(store, (data) => {\n return { data };\n});\n
"
},
{
"textRaw": "`channel.unbindStore(store)`",
"type": "method",
"name": "unbindStore",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if the store was found, `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if the store was found, `false` otherwise."
},
"params": [
{
"textRaw": "`store` {AsyncLocalStorage} The store to unbind from the channel.",
"name": "store",
"type": "AsyncLocalStorage",
"desc": "The store to unbind from the channel."
}
]
}
],
"desc": "Remove a message handler previously registered to this channel with\nchannel.bindStore(store)
.
import diagnostics_channel from 'node:diagnostics_channel';\nimport { AsyncLocalStorage } from 'node:async_hooks';\n\nconst store = new AsyncLocalStorage();\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.bindStore(store);\nchannel.unbindStore(store);\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\nconst { AsyncLocalStorage } = require('node:async_hooks');\n\nconst store = new AsyncLocalStorage();\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.bindStore(store);\nchannel.unbindStore(store);\n
"
},
{
"textRaw": "`channel.runStores(context, fn[, thisArg[, ...args]])`",
"type": "method",
"name": "runStores",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": [
{
"textRaw": "`context` {any} Message to send to subscribers and bind to stores",
"name": "context",
"type": "any",
"desc": "Message to send to subscribers and bind to stores"
},
{
"textRaw": "`fn` {Function} Handler to run within the entered storage context",
"name": "fn",
"type": "Function",
"desc": "Handler to run within the entered storage context"
},
{
"textRaw": "`thisArg` {any} The receiver to be used for the function call.",
"name": "thisArg",
"type": "any",
"desc": "The receiver to be used for the function call."
},
{
"textRaw": "`...args` {any} Optional arguments to pass to the function.",
"name": "...args",
"type": "any",
"desc": "Optional arguments to pass to the function."
}
]
}
],
"desc": "Applies the given data to any AsyncLocalStorage instances bound to the channel\nfor the duration of the given function, then publishes to the channel within\nthe scope of that data is applied to the stores.
\nIf a transform function was given to channel.bindStore(store)
it will be\napplied to transform the message data before it becomes the context value for\nthe store. The prior storage context is accessible from within the transform\nfunction in cases where context linking is required.
The context applied to the store should be accessible in any async code which\ncontinues from execution which began during the given function, however\nthere are some situations in which context loss may occur.
\nimport diagnostics_channel from 'node:diagnostics_channel';\nimport { AsyncLocalStorage } from 'node:async_hooks';\n\nconst store = new AsyncLocalStorage();\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.bindStore(store, (message) => {\n const parent = store.getStore();\n return new Span(message, parent);\n});\nchannel.runStores({ some: 'message' }, () => {\n store.getStore(); // Span({ some: 'message' })\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\nconst { AsyncLocalStorage } = require('node:async_hooks');\n\nconst store = new AsyncLocalStorage();\n\nconst channel = diagnostics_channel.channel('my-channel');\n\nchannel.bindStore(store, (message) => {\n const parent = store.getStore();\n return new Span(message, parent);\n});\nchannel.runStores({ some: 'message' }, () => {\n store.getStore(); // Span({ some: 'message' })\n});\n
"
}
]
},
{
"textRaw": "Class: `TracingChannel`",
"type": "class",
"name": "TracingChannel",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "The class TracingChannel
is a collection of TracingChannel Channels which\ntogether express a single traceable action. It is used to formalize and\nsimplify the process of producing events for tracing application flow.\ndiagnostics_channel.tracingChannel()
is used to construct a\nTracingChannel
. As with Channel
it is recommended to create and reuse a\nsingle TracingChannel
at the top-level of the file rather than creating them\ndynamically.
Helper to subscribe a collection of functions to the corresponding channels.\nThis is the same as calling channel.subscribe(onMessage)
on each channel\nindividually.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.subscribe({\n start(message) {\n // Handle start message\n },\n end(message) {\n // Handle end message\n },\n asyncStart(message) {\n // Handle asyncStart message\n },\n asyncEnd(message) {\n // Handle asyncEnd message\n },\n error(message) {\n // Handle error message\n },\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.subscribe({\n start(message) {\n // Handle start message\n },\n end(message) {\n // Handle end message\n },\n asyncStart(message) {\n // Handle asyncStart message\n },\n asyncEnd(message) {\n // Handle asyncEnd message\n },\n error(message) {\n // Handle error message\n },\n});\n
"
},
{
"textRaw": "`tracingChannel.unsubscribe(subscribers)`",
"type": "method",
"name": "unsubscribe",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if all handlers were successfully unsubscribed, and `false` otherwise.",
"name": "return",
"type": "boolean",
"desc": "`true` if all handlers were successfully unsubscribed, and `false` otherwise."
},
"params": [
{
"textRaw": "`subscribers` {Object} Set of [TracingChannel Channels][] subscribers",
"name": "subscribers",
"type": "Object",
"desc": "Set of [TracingChannel Channels][] subscribers",
"options": [
{
"textRaw": "`start` {Function} The [`start` event][] subscriber",
"name": "start",
"type": "Function",
"desc": "The [`start` event][] subscriber"
},
{
"textRaw": "`end` {Function} The [`end` event][] subscriber",
"name": "end",
"type": "Function",
"desc": "The [`end` event][] subscriber"
},
{
"textRaw": "`asyncStart` {Function} The [`asyncStart` event][] subscriber",
"name": "asyncStart",
"type": "Function",
"desc": "The [`asyncStart` event][] subscriber"
},
{
"textRaw": "`asyncEnd` {Function} The [`asyncEnd` event][] subscriber",
"name": "asyncEnd",
"type": "Function",
"desc": "The [`asyncEnd` event][] subscriber"
},
{
"textRaw": "`error` {Function} The [`error` event][] subscriber",
"name": "error",
"type": "Function",
"desc": "The [`error` event][] subscriber"
}
]
}
]
}
],
"desc": "Helper to unsubscribe a collection of functions from the corresponding channels.\nThis is the same as calling channel.unsubscribe(onMessage)
on each channel\nindividually.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.unsubscribe({\n start(message) {\n // Handle start message\n },\n end(message) {\n // Handle end message\n },\n asyncStart(message) {\n // Handle asyncStart message\n },\n asyncEnd(message) {\n // Handle asyncEnd message\n },\n error(message) {\n // Handle error message\n },\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.unsubscribe({\n start(message) {\n // Handle start message\n },\n end(message) {\n // Handle end message\n },\n asyncStart(message) {\n // Handle asyncStart message\n },\n asyncEnd(message) {\n // Handle asyncEnd message\n },\n error(message) {\n // Handle error message\n },\n});\n
"
},
{
"textRaw": "`tracingChannel.traceSync(fn[, context[, thisArg[, ...args]]])`",
"type": "method",
"name": "traceSync",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {any} The return value of the given function",
"name": "return",
"type": "any",
"desc": "The return value of the given function"
},
"params": [
{
"textRaw": "`fn` {Function} Function to wrap a trace around",
"name": "fn",
"type": "Function",
"desc": "Function to wrap a trace around"
},
{
"textRaw": "`context` {Object} Shared object to correlate events through",
"name": "context",
"type": "Object",
"desc": "Shared object to correlate events through"
},
{
"textRaw": "`thisArg` {any} The receiver to be used for the function call",
"name": "thisArg",
"type": "any",
"desc": "The receiver to be used for the function call"
},
{
"textRaw": "`...args` {any} Optional arguments to pass to the function",
"name": "...args",
"type": "any",
"desc": "Optional arguments to pass to the function"
}
]
}
],
"desc": "Trace a synchronous function call. This will always produce a start
event\nand end
event around the execution and may produce an error
event\nif the given function throws an error. This will run the given function using\nchannel.runStores(context, ...)
on the start
channel which ensures all\nevents should have any bound stores set to match this trace context.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.traceSync(() => {\n // Do something\n}, {\n some: 'thing',\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.traceSync(() => {\n // Do something\n}, {\n some: 'thing',\n});\n
"
},
{
"textRaw": "`tracingChannel.tracePromise(fn[, context[, thisArg[, ...args]]])`",
"type": "method",
"name": "tracePromise",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Chained from promise returned by the given function",
"name": "return",
"type": "Promise",
"desc": "Chained from promise returned by the given function"
},
"params": [
{
"textRaw": "`fn` {Function} Promise-returning function to wrap a trace around",
"name": "fn",
"type": "Function",
"desc": "Promise-returning function to wrap a trace around"
},
{
"textRaw": "`context` {Object} Shared object to correlate trace events through",
"name": "context",
"type": "Object",
"desc": "Shared object to correlate trace events through"
},
{
"textRaw": "`thisArg` {any} The receiver to be used for the function call",
"name": "thisArg",
"type": "any",
"desc": "The receiver to be used for the function call"
},
{
"textRaw": "`...args` {any} Optional arguments to pass to the function",
"name": "...args",
"type": "any",
"desc": "Optional arguments to pass to the function"
}
]
}
],
"desc": "Trace a promise-returning function call. This will always produce a\nstart
event and end
event around the synchronous portion of the\nfunction execution, and will produce an asyncStart
event and\nasyncEnd
event when a promise continuation is reached. It may also\nproduce an error
event if the given function throws an error or the\nreturned promise rejects. This will run the given function using\nchannel.runStores(context, ...)
on the start
channel which ensures all\nevents should have any bound stores set to match this trace context.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.tracePromise(async () => {\n // Do something\n}, {\n some: 'thing',\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.tracePromise(async () => {\n // Do something\n}, {\n some: 'thing',\n});\n
"
},
{
"textRaw": "`tracingChannel.traceCallback(fn, position, context, thisArg, ...args)`",
"type": "method",
"name": "traceCallback",
"meta": {
"added": [
"v19.9.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {any} The return value of the given function",
"name": "return",
"type": "any",
"desc": "The return value of the given function"
},
"params": [
{
"textRaw": "`fn` {Function} callback using function to wrap a trace around",
"name": "fn",
"type": "Function",
"desc": "callback using function to wrap a trace around"
},
{
"textRaw": "`position` {number} Zero-indexed argument position of expected callback (defaults to last argument if `undefined` is passed)",
"name": "position",
"type": "number",
"desc": "Zero-indexed argument position of expected callback (defaults to last argument if `undefined` is passed)"
},
{
"textRaw": "`context` {Object} Shared object to correlate trace events through (defaults to `{}` if `undefined` is passed)",
"name": "context",
"type": "Object",
"desc": "Shared object to correlate trace events through (defaults to `{}` if `undefined` is passed)"
},
{
"textRaw": "`thisArg` {any} The receiver to be used for the function call",
"name": "thisArg",
"type": "any",
"desc": "The receiver to be used for the function call"
},
{
"textRaw": "`...args` {any} arguments to pass to the function (must include the callback)",
"name": "...args",
"type": "any",
"desc": "arguments to pass to the function (must include the callback)"
}
]
}
],
"desc": "Trace a callback-receiving function call. The callback is expected to follow\nthe error as first arg convention typically used. This will always produce a\nstart
event and end
event around the synchronous portion of the\nfunction execution, and will produce a asyncStart
event and\nasyncEnd
event around the callback execution. It may also produce an\nerror
event if the given function throws or the first argument passed to\nthe callback is set. This will run the given function using\nchannel.runStores(context, ...)
on the start
channel which ensures all\nevents should have any bound stores set to match this trace context.
import diagnostics_channel from 'node:diagnostics_channel';\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.traceCallback((arg1, callback) => {\n // Do something\n callback(null, 'result');\n}, 1, {\n some: 'thing',\n}, thisArg, arg1, callback);\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\n\nchannels.traceCallback((arg1, callback) => {\n // Do something\n callback(null, 'result');\n}, {\n some: 'thing',\n}, thisArg, arg1, callback);\n
\nThe callback will also be run with channel.runStores(context, ...)
which\nenables context loss recovery in some cases.
import diagnostics_channel from 'node:diagnostics_channel';\nimport { AsyncLocalStorage } from 'node:async_hooks';\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\nconst myStore = new AsyncLocalStorage();\n\n// The start channel sets the initial store data to something\n// and stores that store data value on the trace context object\nchannels.start.bindStore(myStore, (data) => {\n const span = new Span(data);\n data.span = span;\n return span;\n});\n\n// Then asyncStart can restore from that data it stored previously\nchannels.asyncStart.bindStore(myStore, (data) => {\n return data.span;\n});\n
\nconst diagnostics_channel = require('node:diagnostics_channel');\nconst { AsyncLocalStorage } = require('node:async_hooks');\n\nconst channels = diagnostics_channel.tracingChannel('my-channel');\nconst myStore = new AsyncLocalStorage();\n\n// The start channel sets the initial store data to something\n// and stores that store data value on the trace context object\nchannels.start.bindStore(myStore, (data) => {\n const span = new Span(data);\n data.span = span;\n return span;\n});\n\n// Then asyncStart can restore from that data it stored previously\nchannels.asyncStart.bindStore(myStore, (data) => {\n return data.span;\n});\n
"
}
]
}
],
"type": "module",
"displayName": "Public API"
}
],
"type": "module",
"displayName": "Diagnostics Channel",
"source": "doc/api/diagnostics_channel.md"
},
{
"textRaw": "DNS",
"name": "dns",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/dns.js
\nThe node:dns
module enables name resolution. For example, use it to look up IP\naddresses of host names.
Although named for the Domain Name System (DNS), it does not always use the\nDNS protocol for lookups. dns.lookup()
uses the operating system\nfacilities to perform name resolution. It may not need to perform any network\ncommunication. To perform name resolution the way other applications on the same\nsystem do, use dns.lookup()
.
const dns = require('node:dns');\n\ndns.lookup('example.org', (err, address, family) => {\n console.log('address: %j family: IPv%s', address, family);\n});\n// address: \"93.184.216.34\" family: IPv4\n
\nAll other functions in the node:dns
module connect to an actual DNS server to\nperform name resolution. They will always use the network to perform DNS\nqueries. These functions do not use the same set of configuration files used by\ndns.lookup()
(e.g. /etc/hosts
). Use these functions to always perform\nDNS queries, bypassing other name-resolution facilities.
const dns = require('node:dns');\n\ndns.resolve4('archive.org', (err, addresses) => {\n if (err) throw err;\n\n console.log(`addresses: ${JSON.stringify(addresses)}`);\n\n addresses.forEach((a) => {\n dns.reverse(a, (err, hostnames) => {\n if (err) {\n throw err;\n }\n console.log(`reverse for ${a}: ${JSON.stringify(hostnames)}`);\n });\n });\n});\n
\nSee the Implementation considerations section for more information.
", "classes": [ { "textRaw": "Class: `dns.Resolver`", "type": "class", "name": "dns.Resolver", "meta": { "added": [ "v8.3.0" ], "changes": [] }, "desc": "An independent resolver for DNS requests.
\nCreating a new resolver uses the default server settings. Setting\nthe servers used for a resolver using\nresolver.setServers()
does not affect\nother resolvers:
const { Resolver } = require('node:dns');\nconst resolver = new Resolver();\nresolver.setServers(['4.4.4.4']);\n\n// This request will use the server at 4.4.4.4, independent of global settings.\nresolver.resolve4('example.org', (err, addresses) => {\n // ...\n});\n
\nThe following methods from the node:dns
module are available:
resolver.getServers()
resolver.resolve()
resolver.resolve4()
resolver.resolve6()
resolver.resolveAny()
resolver.resolveCaa()
resolver.resolveCname()
resolver.resolveMx()
resolver.resolveNaptr()
resolver.resolveNs()
resolver.resolvePtr()
resolver.resolveSoa()
resolver.resolveSrv()
resolver.resolveTxt()
resolver.reverse()
resolver.setServers()
Create a new resolver.
\noptions
<Object>\n\nCancel all outstanding DNS queries made by this resolver. The corresponding\ncallbacks will be called with an error with code ECANCELLED
.
The resolver instance will send its requests from the specified IP address.\nThis allows programs to specify outbound interfaces when used on multi-homed\nsystems.
\nIf a v4 or v6 address is not specified, it is set to the default and the\noperating system will choose a local address automatically.
\nThe resolver will use the v4 local address when making requests to IPv4 DNS\nservers, and the v6 local address when making requests to IPv6 DNS servers.\nThe rrtype
of resolution requests has no impact on the local address used.
Returns an array of IP address strings, formatted according to RFC 5952,\nthat are currently configured for DNS resolution. A string will include a port\nsection if a custom port is used.
\n\n[\n '8.8.8.8',\n '2001:4860:4860::8888',\n '8.8.8.8:1053',\n '[2001:4860:4860::8888]:1053',\n]\n
"
},
{
"textRaw": "`dns.lookup(hostname[, options], callback)`",
"type": "method",
"name": "lookup",
"meta": {
"added": [
"v0.1.90"
],
"changes": [
{
"version": "v18.4.0",
"pr-url": "https://github.com/nodejs/node/pull/43054",
"description": "For compatibility with `node:net`, when passing an option object the `family` option can be the string `'IPv4'` or the string `'IPv6'`."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v17.0.0",
"pr-url": "https://github.com/nodejs/node/pull/39987",
"description": "The `verbatim` options defaults to `true` now."
},
{
"version": "v8.5.0",
"pr-url": "https://github.com/nodejs/node/pull/14731",
"description": "The `verbatim` option is supported now."
},
{
"version": "v1.2.0",
"pr-url": "https://github.com/nodejs/node/pull/744",
"description": "The `all` option is supported now."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
},
{
"textRaw": "`options` {integer | Object}",
"name": "options",
"type": "integer | Object",
"options": [
{
"textRaw": "`family` {integer|string} The record family. Must be `4`, `6`, or `0`. For backward compatibility reasons,`'IPv4'` and `'IPv6'` are interpreted as `4` and `6` respectively. The value `0` indicates that either an IPv4 or IPv6 address is returned. If the value `0` is used with `{ all: true } (see below)`, both IPv4 and IPv6 addresses are returned. **Default:** `0`.",
"name": "family",
"type": "integer|string",
"default": "`0`",
"desc": "The record family. Must be `4`, `6`, or `0`. For backward compatibility reasons,`'IPv4'` and `'IPv6'` are interpreted as `4` and `6` respectively. The value `0` indicates that either an IPv4 or IPv6 address is returned. If the value `0` is used with `{ all: true } (see below)`, both IPv4 and IPv6 addresses are returned."
},
{
"textRaw": "`hints` {number} One or more [supported `getaddrinfo` flags][]. Multiple flags may be passed by bitwise `OR`ing their values.",
"name": "hints",
"type": "number",
"desc": "One or more [supported `getaddrinfo` flags][]. Multiple flags may be passed by bitwise `OR`ing their values."
},
{
"textRaw": "`all` {boolean} When `true`, the callback returns all resolved addresses in an array. Otherwise, returns a single address. **Default:** `false`.",
"name": "all",
"type": "boolean",
"default": "`false`",
"desc": "When `true`, the callback returns all resolved addresses in an array. Otherwise, returns a single address."
},
{
"textRaw": "`verbatim` {boolean} When `true`, the callback receives IPv4 and IPv6 addresses in the order the DNS resolver returned them. When `false`, IPv4 addresses are placed before IPv6 addresses. **Default:** `true` (addresses are not reordered). Default value is configurable using [`dns.setDefaultResultOrder()`][] or [`--dns-result-order`][].",
"name": "verbatim",
"type": "boolean",
"default": "`true` (addresses are not reordered). Default value is configurable using [`dns.setDefaultResultOrder()`][] or [`--dns-result-order`][]",
"desc": "When `true`, the callback receives IPv4 and IPv6 addresses in the order the DNS resolver returned them. When `false`, IPv4 addresses are placed before IPv6 addresses."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`address` {string} A string representation of an IPv4 or IPv6 address.",
"name": "address",
"type": "string",
"desc": "A string representation of an IPv4 or IPv6 address."
},
{
"textRaw": "`family` {integer} `4` or `6`, denoting the family of `address`, or `0` if the address is not an IPv4 or IPv6 address. `0` is a likely indicator of a bug in the name resolution service used by the operating system.",
"name": "family",
"type": "integer",
"desc": "`4` or `6`, denoting the family of `address`, or `0` if the address is not an IPv4 or IPv6 address. `0` is a likely indicator of a bug in the name resolution service used by the operating system."
}
]
}
]
}
],
"desc": "Resolves a host name (e.g. 'nodejs.org'
) into the first found A (IPv4) or\nAAAA (IPv6) record. All option
properties are optional. If options
is an\ninteger, then it must be 4
or 6
– if options
is 0
or not provided, then\nIPv4 and IPv6 addresses are both returned if found.
With the all
option set to true
, the arguments for callback
change to\n(err, addresses)
, with addresses
being an array of objects with the\nproperties address
and family
.
On error, err
is an Error
object, where err.code
is the error code.\nKeep in mind that err.code
will be set to 'ENOTFOUND'
not only when\nthe host name does not exist but also when the lookup fails in other ways\nsuch as no available file descriptors.
dns.lookup()
does not necessarily have anything to do with the DNS protocol.\nThe implementation uses an operating system facility that can associate names\nwith addresses and vice versa. This implementation can have subtle but\nimportant consequences on the behavior of any Node.js program. Please take some\ntime to consult the Implementation considerations section before using\ndns.lookup()
.
Example usage:
\nconst dns = require('node:dns');\nconst options = {\n family: 6,\n hints: dns.ADDRCONFIG | dns.V4MAPPED,\n};\ndns.lookup('example.com', options, (err, address, family) =>\n console.log('address: %j family: IPv%s', address, family));\n// address: \"2606:2800:220:1:248:1893:25c8:1946\" family: IPv6\n\n// When options.all is true, the result will be an Array.\noptions.all = true;\ndns.lookup('example.com', options, (err, addresses) =>\n console.log('addresses: %j', addresses));\n// addresses: [{\"address\":\"2606:2800:220:1:248:1893:25c8:1946\",\"family\":6}]\n
\nIf this method is invoked as its util.promisify()
ed version, and all
\nis not set to true
, it returns a Promise
for an Object
with address
and\nfamily
properties.
The following flags can be passed as hints to dns.lookup()
.
dns.ADDRCONFIG
: Limits returned address types to the types of non-loopback\naddresses configured on the system. For example, IPv4 addresses are only\nreturned if the current system has at least one IPv4 address configured.dns.V4MAPPED
: If the IPv6 family was specified, but no IPv6 addresses were\nfound, then return IPv4 mapped IPv6 addresses. It is not supported\non some operating systems (e.g. FreeBSD 10.1).dns.ALL
: If dns.V4MAPPED
is specified, return resolved IPv6 addresses as\nwell as IPv4 mapped IPv6 addresses.Resolves the given address
and port
into a host name and service using\nthe operating system's underlying getnameinfo
implementation.
If address
is not a valid IP address, a TypeError
will be thrown.\nThe port
will be coerced to a number. If it is not a legal port, a TypeError
\nwill be thrown.
On an error, err
is an Error
object, where err.code
is the error code.
const dns = require('node:dns');\ndns.lookupService('127.0.0.1', 22, (err, hostname, service) => {\n console.log(hostname, service);\n // Prints: localhost ssh\n});\n
\nIf this method is invoked as its util.promisify()
ed version, it returns a\nPromise
for an Object
with hostname
and service
properties.
Uses the DNS protocol to resolve a host name (e.g. 'nodejs.org'
) into an array\nof the resource records. The callback
function has arguments\n(err, records)
. When successful, records
will be an array of resource\nrecords. The type and structure of individual results varies based on rrtype
:
rrtype | \nrecords contains | \nResult type | \nShorthand method | \n
---|---|---|---|
'A' | \nIPv4 addresses (default) | \n<string> | \ndns.resolve4() | \n
'AAAA' | \nIPv6 addresses | \n<string> | \ndns.resolve6() | \n
'ANY' | \nany records | \n<Object> | \ndns.resolveAny() | \n
'CAA' | \nCA authorization records | \n<Object> | \ndns.resolveCaa() | \n
'CNAME' | \ncanonical name records | \n<string> | \ndns.resolveCname() | \n
'MX' | \nmail exchange records | \n<Object> | \ndns.resolveMx() | \n
'NAPTR' | \nname authority pointer records | \n<Object> | \ndns.resolveNaptr() | \n
'NS' | \nname server records | \n<string> | \ndns.resolveNs() | \n
'PTR' | \npointer records | \n<string> | \ndns.resolvePtr() | \n
'SOA' | \nstart of authority records | \n<Object> | \ndns.resolveSoa() | \n
'SRV' | \nservice records | \n<Object> | \ndns.resolveSrv() | \n
'TXT' | \ntext records | \n<string[]> | \ndns.resolveTxt() | \n
On error, err
is an Error
object, where err.code
is one of the\nDNS error codes.
Uses the DNS protocol to resolve a IPv4 addresses (A
records) for the\nhostname
. The addresses
argument passed to the callback
function\nwill contain an array of IPv4 addresses (e.g.\n['74.125.79.104', '74.125.79.105', '74.125.79.106']
).
Uses the DNS protocol to resolve IPv6 addresses (AAAA
records) for the\nhostname
. The addresses
argument passed to the callback
function\nwill contain an array of IPv6 addresses.
Uses the DNS protocol to resolve all records (also known as ANY
or *
query).\nThe ret
argument passed to the callback
function will be an array containing\nvarious types of records. Each object has a property type
that indicates the\ntype of the current record. And depending on the type
, additional properties\nwill be present on the object:
Type | \nProperties | \n
---|---|
'A' | \naddress /ttl | \n
'AAAA' | \naddress /ttl | \n
'CNAME' | \nvalue | \n
'MX' | \nRefer to dns.resolveMx() | \n
'NAPTR' | \nRefer to dns.resolveNaptr() | \n
'NS' | \nvalue | \n
'PTR' | \nvalue | \n
'SOA' | \nRefer to dns.resolveSoa() | \n
'SRV' | \nRefer to dns.resolveSrv() | \n
'TXT' | \nThis type of record contains an array property called entries which refers to dns.resolveTxt() , e.g. { entries: ['...'], type: 'TXT' } | \n
Here is an example of the ret
object passed to the callback:
[ { type: 'A', address: '127.0.0.1', ttl: 299 },\n { type: 'CNAME', value: 'example.com' },\n { type: 'MX', exchange: 'alt4.aspmx.l.example.com', priority: 50 },\n { type: 'NS', value: 'ns1.example.com' },\n { type: 'TXT', entries: [ 'v=spf1 include:_spf.example.com ~all' ] },\n { type: 'SOA',\n nsname: 'ns1.example.com',\n hostmaster: 'admin.example.com',\n serial: 156696742,\n refresh: 900,\n retry: 900,\n expire: 1800,\n minttl: 60 } ]\n
\nDNS server operators may choose not to respond to ANY
\nqueries. It may be better to call individual methods like dns.resolve4()
,\ndns.resolveMx()
, and so on. For more details, see RFC 8482.
Uses the DNS protocol to resolve CNAME
records for the hostname
. The\naddresses
argument passed to the callback
function\nwill contain an array of canonical name records available for the hostname
\n(e.g. ['bar.example.com']
).
Uses the DNS protocol to resolve CAA
records for the hostname
. The\naddresses
argument passed to the callback
function\nwill contain an array of certification authority authorization records\navailable for the hostname
(e.g. [{critical: 0, iodef: 'mailto:pki@example.com'}, {critical: 128, issue: 'pki.example.com'}]
).
Uses the DNS protocol to resolve mail exchange records (MX
records) for the\nhostname
. The addresses
argument passed to the callback
function will\ncontain an array of objects containing both a priority
and exchange
\nproperty (e.g. [{priority: 10, exchange: 'mx.example.com'}, ...]
).
Uses the DNS protocol to resolve regular expression-based records (NAPTR
\nrecords) for the hostname
. The addresses
argument passed to the callback
\nfunction will contain an array of objects with the following properties:
flags
service
regexp
replacement
order
preference
{\n flags: 's',\n service: 'SIP+D2U',\n regexp: '',\n replacement: '_sip._udp.example.com',\n order: 30,\n preference: 100\n}\n
"
},
{
"textRaw": "`dns.resolveNs(hostname, callback)`",
"type": "method",
"name": "resolveNs",
"meta": {
"added": [
"v0.1.90"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`addresses` {string\\[]}",
"name": "addresses",
"type": "string\\[]"
}
]
}
]
}
],
"desc": "Uses the DNS protocol to resolve name server records (NS
records) for the\nhostname
. The addresses
argument passed to the callback
function will\ncontain an array of name server records available for hostname
\n(e.g. ['ns1.example.com', 'ns2.example.com']
).
Uses the DNS protocol to resolve pointer records (PTR
records) for the\nhostname
. The addresses
argument passed to the callback
function will\nbe an array of strings containing the reply records.
Uses the DNS protocol to resolve a start of authority record (SOA
record) for\nthe hostname
. The address
argument passed to the callback
function will\nbe an object with the following properties:
nsname
hostmaster
serial
refresh
retry
expire
minttl
{\n nsname: 'ns.example.com',\n hostmaster: 'root.example.com',\n serial: 2013101809,\n refresh: 10000,\n retry: 2400,\n expire: 604800,\n minttl: 3600\n}\n
"
},
{
"textRaw": "`dns.resolveSrv(hostname, callback)`",
"type": "method",
"name": "resolveSrv",
"meta": {
"added": [
"v0.1.27"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`addresses` {Object\\[]}",
"name": "addresses",
"type": "Object\\[]"
}
]
}
]
}
],
"desc": "Uses the DNS protocol to resolve service records (SRV
records) for the\nhostname
. The addresses
argument passed to the callback
function will\nbe an array of objects with the following properties:
priority
weight
port
name
{\n priority: 10,\n weight: 5,\n port: 21223,\n name: 'service.example.com'\n}\n
"
},
{
"textRaw": "`dns.resolveTxt(hostname, callback)`",
"type": "method",
"name": "resolveTxt",
"meta": {
"added": [
"v0.1.27"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
}
]
},
"signatures": [
{
"params": []
}
],
"desc": "\nhostname
<string>callback
<Function>\nerr
<Error>records
<string[][]>Uses the DNS protocol to resolve text queries (TXT
records) for the\nhostname
. The records
argument passed to the callback
function is a\ntwo-dimensional array of the text records available for hostname
(e.g.\n[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]
). Each sub-array contains TXT chunks of\none record. Depending on the use case, these could be either joined together or\ntreated separately.
Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an\narray of host names.
\nOn error, err
is an Error
object, where err.code
is\none of the DNS error codes.
Set the default value of verbatim
in dns.lookup()
and\ndnsPromises.lookup()
. The value could be:
ipv4first
: sets default verbatim
false
.verbatim
: sets default verbatim
true
.The default is verbatim
and dns.setDefaultResultOrder()
have higher\npriority than --dns-result-order
. When using worker threads,\ndns.setDefaultResultOrder()
from the main thread won't affect the default\ndns orders in workers.
Get the default value for verbatim
in dns.lookup()
and\ndnsPromises.lookup()
. The value could be:
ipv4first
: for verbatim
defaulting to false
.verbatim
: for verbatim
defaulting to true
.Sets the IP address and port of servers to be used when performing DNS\nresolution. The servers
argument is an array of RFC 5952 formatted\naddresses. If the port is the IANA default DNS port (53) it can be omitted.
dns.setServers([\n '8.8.8.8',\n '[2001:4860:4860::8888]',\n '8.8.8.8:1053',\n '[2001:4860:4860::8888]:1053',\n]);\n
\nAn error will be thrown if an invalid address is provided.
\nThe dns.setServers()
method must not be called while a DNS query is in\nprogress.
The dns.setServers()
method affects only dns.resolve()
,\ndns.resolve*()
and dns.reverse()
(and specifically not\ndns.lookup()
).
This method works much like\nresolve.conf.\nThat is, if attempting to resolve with the first server provided results in a\nNOTFOUND
error, the resolve()
method will not attempt to resolve with\nsubsequent servers provided. Fallback DNS servers will only be used if the\nearlier ones time out or result in some other error.
The dns.promises
API provides an alternative set of asynchronous DNS methods\nthat return Promise
objects rather than using callbacks. The API is accessible\nvia require('node:dns').promises
or require('node:dns/promises')
.
An independent resolver for DNS requests.
\nCreating a new resolver uses the default server settings. Setting\nthe servers used for a resolver using\nresolver.setServers()
does not affect\nother resolvers:
const { Resolver } = require('node:dns').promises;\nconst resolver = new Resolver();\nresolver.setServers(['4.4.4.4']);\n\n// This request will use the server at 4.4.4.4, independent of global settings.\nresolver.resolve4('example.org').then((addresses) => {\n // ...\n});\n\n// Alternatively, the same code can be written using async-await style.\n(async function() {\n const addresses = await resolver.resolve4('example.org');\n})();\n
\nThe following methods from the dnsPromises
API are available:
resolver.getServers()
resolver.resolve()
resolver.resolve4()
resolver.resolve6()
resolver.resolveAny()
resolver.resolveCaa()
resolver.resolveCname()
resolver.resolveMx()
resolver.resolveNaptr()
resolver.resolveNs()
resolver.resolvePtr()
resolver.resolveSoa()
resolver.resolveSrv()
resolver.resolveTxt()
resolver.reverse()
resolver.setServers()
Cancel all outstanding DNS queries made by this resolver. The corresponding\npromises will be rejected with an error with the code ECANCELLED
.
Returns an array of IP address strings, formatted according to RFC 5952,\nthat are currently configured for DNS resolution. A string will include a port\nsection if a custom port is used.
\n\n[\n '8.8.8.8',\n '2001:4860:4860::8888',\n '8.8.8.8:1053',\n '[2001:4860:4860::8888]:1053',\n]\n
"
},
{
"textRaw": "`dnsPromises.lookup(hostname[, options])`",
"type": "method",
"name": "lookup",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
},
{
"textRaw": "`options` {integer | Object}",
"name": "options",
"type": "integer | Object",
"options": [
{
"textRaw": "`family` {integer} The record family. Must be `4`, `6`, or `0`. The value `0` indicates that either an IPv4 or IPv6 address is returned. If the value `0` is used with `{ all: true }` (see below), both IPv4 and IPv6 addresses are returned. **Default:** `0`.",
"name": "family",
"type": "integer",
"default": "`0`",
"desc": "The record family. Must be `4`, `6`, or `0`. The value `0` indicates that either an IPv4 or IPv6 address is returned. If the value `0` is used with `{ all: true }` (see below), both IPv4 and IPv6 addresses are returned."
},
{
"textRaw": "`hints` {number} One or more [supported `getaddrinfo` flags][]. Multiple flags may be passed by bitwise `OR`ing their values.",
"name": "hints",
"type": "number",
"desc": "One or more [supported `getaddrinfo` flags][]. Multiple flags may be passed by bitwise `OR`ing their values."
},
{
"textRaw": "`all` {boolean} When `true`, the `Promise` is resolved with all addresses in an array. Otherwise, returns a single address. **Default:** `false`.",
"name": "all",
"type": "boolean",
"default": "`false`",
"desc": "When `true`, the `Promise` is resolved with all addresses in an array. Otherwise, returns a single address."
},
{
"textRaw": "`verbatim` {boolean} When `true`, the `Promise` is resolved with IPv4 and IPv6 addresses in the order the DNS resolver returned them. When `false`, IPv4 addresses are placed before IPv6 addresses. **Default:** currently `false` (addresses are reordered) but this is expected to change in the not too distant future. Default value is configurable using [`dns.setDefaultResultOrder()`][] or [`--dns-result-order`][]. New code should use `{ verbatim: true }`.",
"name": "verbatim",
"type": "boolean",
"default": "currently `false` (addresses are reordered) but this is expected to change in the not too distant future. Default value is configurable using [`dns.setDefaultResultOrder()`][] or [`--dns-result-order`][]. New code should use `{ verbatim: true }`",
"desc": "When `true`, the `Promise` is resolved with IPv4 and IPv6 addresses in the order the DNS resolver returned them. When `false`, IPv4 addresses are placed before IPv6 addresses."
}
]
}
]
}
],
"desc": "Resolves a host name (e.g. 'nodejs.org'
) into the first found A (IPv4) or\nAAAA (IPv6) record. All option
properties are optional. If options
is an\ninteger, then it must be 4
or 6
– if options
is not provided, then IPv4\nand IPv6 addresses are both returned if found.
With the all
option set to true
, the Promise
is resolved with addresses
\nbeing an array of objects with the properties address
and family
.
On error, the Promise
is rejected with an Error
object, where err.code
\nis the error code.\nKeep in mind that err.code
will be set to 'ENOTFOUND'
not only when\nthe host name does not exist but also when the lookup fails in other ways\nsuch as no available file descriptors.
dnsPromises.lookup()
does not necessarily have anything to do with the DNS\nprotocol. The implementation uses an operating system facility that can\nassociate names with addresses and vice versa. This implementation can have\nsubtle but important consequences on the behavior of any Node.js program. Please\ntake some time to consult the Implementation considerations section before\nusing dnsPromises.lookup()
.
Example usage:
\nconst dns = require('node:dns');\nconst dnsPromises = dns.promises;\nconst options = {\n family: 6,\n hints: dns.ADDRCONFIG | dns.V4MAPPED,\n};\n\ndnsPromises.lookup('example.com', options).then((result) => {\n console.log('address: %j family: IPv%s', result.address, result.family);\n // address: \"2606:2800:220:1:248:1893:25c8:1946\" family: IPv6\n});\n\n// When options.all is true, the result will be an Array.\noptions.all = true;\ndnsPromises.lookup('example.com', options).then((result) => {\n console.log('addresses: %j', result);\n // addresses: [{\"address\":\"2606:2800:220:1:248:1893:25c8:1946\",\"family\":6}]\n});\n
"
},
{
"textRaw": "`dnsPromises.lookupService(address, port)`",
"type": "method",
"name": "lookupService",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`address` {string}",
"name": "address",
"type": "string"
},
{
"textRaw": "`port` {number}",
"name": "port",
"type": "number"
}
]
}
],
"desc": "Resolves the given address
and port
into a host name and service using\nthe operating system's underlying getnameinfo
implementation.
If address
is not a valid IP address, a TypeError
will be thrown.\nThe port
will be coerced to a number. If it is not a legal port, a TypeError
\nwill be thrown.
On error, the Promise
is rejected with an Error
object, where err.code
\nis the error code.
const dnsPromises = require('node:dns').promises;\ndnsPromises.lookupService('127.0.0.1', 22).then((result) => {\n console.log(result.hostname, result.service);\n // Prints: localhost ssh\n});\n
"
},
{
"textRaw": "`dnsPromises.resolve(hostname[, rrtype])`",
"type": "method",
"name": "resolve",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string} Host name to resolve.",
"name": "hostname",
"type": "string",
"desc": "Host name to resolve."
},
{
"textRaw": "`rrtype` {string} Resource record type. **Default:** `'A'`.",
"name": "rrtype",
"type": "string",
"default": "`'A'`",
"desc": "Resource record type."
}
]
}
],
"desc": "Uses the DNS protocol to resolve a host name (e.g. 'nodejs.org'
) into an array\nof the resource records. When successful, the Promise
is resolved with an\narray of resource records. The type and structure of individual results vary\nbased on rrtype
:
rrtype | \nrecords contains | \nResult type | \nShorthand method | \n
---|---|---|---|
'A' | \nIPv4 addresses (default) | \n<string> | \ndnsPromises.resolve4() | \n
'AAAA' | \nIPv6 addresses | \n<string> | \ndnsPromises.resolve6() | \n
'ANY' | \nany records | \n<Object> | \ndnsPromises.resolveAny() | \n
'CAA' | \nCA authorization records | \n<Object> | \ndnsPromises.resolveCaa() | \n
'CNAME' | \ncanonical name records | \n<string> | \ndnsPromises.resolveCname() | \n
'MX' | \nmail exchange records | \n<Object> | \ndnsPromises.resolveMx() | \n
'NAPTR' | \nname authority pointer records | \n<Object> | \ndnsPromises.resolveNaptr() | \n
'NS' | \nname server records | \n<string> | \ndnsPromises.resolveNs() | \n
'PTR' | \npointer records | \n<string> | \ndnsPromises.resolvePtr() | \n
'SOA' | \nstart of authority records | \n<Object> | \ndnsPromises.resolveSoa() | \n
'SRV' | \nservice records | \n<Object> | \ndnsPromises.resolveSrv() | \n
'TXT' | \ntext records | \n<string[]> | \ndnsPromises.resolveTxt() | \n
On error, the Promise
is rejected with an Error
object, where err.code
\nis one of the DNS error codes.
Uses the DNS protocol to resolve IPv4 addresses (A
records) for the\nhostname
. On success, the Promise
is resolved with an array of IPv4\naddresses (e.g. ['74.125.79.104', '74.125.79.105', '74.125.79.106']
).
Uses the DNS protocol to resolve IPv6 addresses (AAAA
records) for the\nhostname
. On success, the Promise
is resolved with an array of IPv6\naddresses.
Uses the DNS protocol to resolve all records (also known as ANY
or *
query).\nOn success, the Promise
is resolved with an array containing various types of\nrecords. Each object has a property type
that indicates the type of the\ncurrent record. And depending on the type
, additional properties will be\npresent on the object:
Type | \nProperties | \n
---|---|
'A' | \naddress /ttl | \n
'AAAA' | \naddress /ttl | \n
'CNAME' | \nvalue | \n
'MX' | \nRefer to dnsPromises.resolveMx() | \n
'NAPTR' | \nRefer to dnsPromises.resolveNaptr() | \n
'NS' | \nvalue | \n
'PTR' | \nvalue | \n
'SOA' | \nRefer to dnsPromises.resolveSoa() | \n
'SRV' | \nRefer to dnsPromises.resolveSrv() | \n
'TXT' | \nThis type of record contains an array property called entries which refers to dnsPromises.resolveTxt() , e.g. { entries: ['...'], type: 'TXT' } | \n
Here is an example of the result object:
\n\n[ { type: 'A', address: '127.0.0.1', ttl: 299 },\n { type: 'CNAME', value: 'example.com' },\n { type: 'MX', exchange: 'alt4.aspmx.l.example.com', priority: 50 },\n { type: 'NS', value: 'ns1.example.com' },\n { type: 'TXT', entries: [ 'v=spf1 include:_spf.example.com ~all' ] },\n { type: 'SOA',\n nsname: 'ns1.example.com',\n hostmaster: 'admin.example.com',\n serial: 156696742,\n refresh: 900,\n retry: 900,\n expire: 1800,\n minttl: 60 } ]\n
"
},
{
"textRaw": "`dnsPromises.resolveCaa(hostname)`",
"type": "method",
"name": "resolveCaa",
"meta": {
"added": [
"v15.0.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
}
]
}
],
"desc": "Uses the DNS protocol to resolve CAA
records for the hostname
. On success,\nthe Promise
is resolved with an array of objects containing available\ncertification authority authorization records available for the hostname
\n(e.g. [{critical: 0, iodef: 'mailto:pki@example.com'},{critical: 128, issue: 'pki.example.com'}]
).
Uses the DNS protocol to resolve CNAME
records for the hostname
. On success,\nthe Promise
is resolved with an array of canonical name records available for\nthe hostname
(e.g. ['bar.example.com']
).
Uses the DNS protocol to resolve mail exchange records (MX
records) for the\nhostname
. On success, the Promise
is resolved with an array of objects\ncontaining both a priority
and exchange
property (e.g.\n[{priority: 10, exchange: 'mx.example.com'}, ...]
).
Uses the DNS protocol to resolve regular expression-based records (NAPTR
\nrecords) for the hostname
. On success, the Promise
is resolved with an array\nof objects with the following properties:
flags
service
regexp
replacement
order
preference
{\n flags: 's',\n service: 'SIP+D2U',\n regexp: '',\n replacement: '_sip._udp.example.com',\n order: 30,\n preference: 100\n}\n
"
},
{
"textRaw": "`dnsPromises.resolveNs(hostname)`",
"type": "method",
"name": "resolveNs",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
}
]
}
],
"desc": "Uses the DNS protocol to resolve name server records (NS
records) for the\nhostname
. On success, the Promise
is resolved with an array of name server\nrecords available for hostname
(e.g.\n['ns1.example.com', 'ns2.example.com']
).
Uses the DNS protocol to resolve pointer records (PTR
records) for the\nhostname
. On success, the Promise
is resolved with an array of strings\ncontaining the reply records.
Uses the DNS protocol to resolve a start of authority record (SOA
record) for\nthe hostname
. On success, the Promise
is resolved with an object with the\nfollowing properties:
nsname
hostmaster
serial
refresh
retry
expire
minttl
{\n nsname: 'ns.example.com',\n hostmaster: 'root.example.com',\n serial: 2013101809,\n refresh: 10000,\n retry: 2400,\n expire: 604800,\n minttl: 3600\n}\n
"
},
{
"textRaw": "`dnsPromises.resolveSrv(hostname)`",
"type": "method",
"name": "resolveSrv",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
}
]
}
],
"desc": "Uses the DNS protocol to resolve service records (SRV
records) for the\nhostname
. On success, the Promise
is resolved with an array of objects with\nthe following properties:
priority
weight
port
name
{\n priority: 10,\n weight: 5,\n port: 21223,\n name: 'service.example.com'\n}\n
"
},
{
"textRaw": "`dnsPromises.resolveTxt(hostname)`",
"type": "method",
"name": "resolveTxt",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
}
]
}
],
"desc": "Uses the DNS protocol to resolve text queries (TXT
records) for the\nhostname
. On success, the Promise
is resolved with a two-dimensional array\nof the text records available for hostname
(e.g.\n[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]
). Each sub-array contains TXT chunks of\none record. Depending on the use case, these could be either joined together or\ntreated separately.
Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an\narray of host names.
\nOn error, the Promise
is rejected with an Error
object, where err.code
\nis one of the DNS error codes.
Set the default value of verbatim
in dns.lookup()
and\ndnsPromises.lookup()
. The value could be:
ipv4first
: sets default verbatim
false
.verbatim
: sets default verbatim
true
.The default is verbatim
and dnsPromises.setDefaultResultOrder()
have\nhigher priority than --dns-result-order
. When using worker threads,\ndnsPromises.setDefaultResultOrder()
from the main thread won't affect the\ndefault dns orders in workers.
Get the value of dnsOrder
.
Sets the IP address and port of servers to be used when performing DNS\nresolution. The servers
argument is an array of RFC 5952 formatted\naddresses. If the port is the IANA default DNS port (53) it can be omitted.
dnsPromises.setServers([\n '8.8.8.8',\n '[2001:4860:4860::8888]',\n '8.8.8.8:1053',\n '[2001:4860:4860::8888]:1053',\n]);\n
\nAn error will be thrown if an invalid address is provided.
\nThe dnsPromises.setServers()
method must not be called while a DNS query is in\nprogress.
This method works much like\nresolve.conf.\nThat is, if attempting to resolve with the first server provided results in a\nNOTFOUND
error, the resolve()
method will not attempt to resolve with\nsubsequent servers provided. Fallback DNS servers will only be used if the\nearlier ones time out or result in some other error.
Each DNS query can return one of the following error codes:
\ndns.NODATA
: DNS server returned an answer with no data.dns.FORMERR
: DNS server claims query was misformatted.dns.SERVFAIL
: DNS server returned general failure.dns.NOTFOUND
: Domain name not found.dns.NOTIMP
: DNS server does not implement the requested operation.dns.REFUSED
: DNS server refused query.dns.BADQUERY
: Misformatted DNS query.dns.BADNAME
: Misformatted host name.dns.BADFAMILY
: Unsupported address family.dns.BADRESP
: Misformatted DNS reply.dns.CONNREFUSED
: Could not contact DNS servers.dns.TIMEOUT
: Timeout while contacting DNS servers.dns.EOF
: End of file.dns.FILE
: Error reading file.dns.NOMEM
: Out of memory.dns.DESTRUCTION
: Channel is being destroyed.dns.BADSTR
: Misformatted string.dns.BADFLAGS
: Illegal flags specified.dns.NONAME
: Given host name is not numeric.dns.BADHINTS
: Illegal hints flags specified.dns.NOTINITIALIZED
: c-ares library initialization not yet performed.dns.LOADIPHLPAPI
: Error loading iphlpapi.dll
.dns.ADDRGETNETWORKPARAMS
: Could not find GetNetworkParams
function.dns.CANCELLED
: DNS query cancelled.The dnsPromises
API also exports the above error codes, e.g., dnsPromises.NODATA
.
Although dns.lookup()
and the various dns.resolve*()/dns.reverse()
\nfunctions have the same goal of associating a network name with a network\naddress (or vice versa), their behavior is quite different. These differences\ncan have subtle but significant consequences on the behavior of Node.js\nprograms.
Under the hood, dns.lookup()
uses the same operating system facilities\nas most other programs. For instance, dns.lookup()
will almost always\nresolve a given name the same way as the ping
command. On most POSIX-like\noperating systems, the behavior of the dns.lookup()
function can be\nmodified by changing settings in nsswitch.conf(5)
and/or resolv.conf(5)
,\nbut changing these files will change the behavior of all other\nprograms running on the same operating system.
Though the call to dns.lookup()
will be asynchronous from JavaScript's\nperspective, it is implemented as a synchronous call to getaddrinfo(3)
that runs\non libuv's threadpool. This can have surprising negative performance\nimplications for some applications, see the UV_THREADPOOL_SIZE
\ndocumentation for more information.
Various networking APIs will call dns.lookup()
internally to resolve\nhost names. If that is an issue, consider resolving the host name to an address\nusing dns.resolve()
and using the address instead of a host name. Also, some\nnetworking APIs (such as socket.connect()
and dgram.createSocket()
)\nallow the default resolver, dns.lookup()
, to be replaced.
These functions are implemented quite differently than dns.lookup()
. They\ndo not use getaddrinfo(3)
and they always perform a DNS query on the\nnetwork. This network communication is always done asynchronously and does not\nuse libuv's threadpool.
As a result, these functions cannot have the same negative impact on other\nprocessing that happens on libuv's threadpool that dns.lookup()
can have.
They do not use the same set of configuration files that dns.lookup()
\nuses. For instance, they do not use the configuration from /etc/hosts
.
Source Code: lib/domain.js
\nThis module is pending deprecation. Once a replacement API has been\nfinalized, this module will be fully deprecated. Most developers should\nnot have cause to use this module. Users who absolutely must have\nthe functionality that domains provide may rely on it for the time being\nbut should expect to have to migrate to a different solution\nin the future.
\nDomains provide a way to handle multiple different IO operations as a\nsingle group. If any of the event emitters or callbacks registered to a\ndomain emit an 'error'
event, or throw an error, then the domain object\nwill be notified, rather than losing the context of the error in the\nprocess.on('uncaughtException')
handler, or causing the program to\nexit immediately with an error code.
Domain error handlers are not a substitute for closing down a\nprocess when an error occurs.
\nBy the very nature of how throw
works in JavaScript, there is almost\nnever any way to safely \"pick up where it left off\", without leaking\nreferences, or creating some other sort of undefined brittle state.
The safest way to respond to a thrown error is to shut down the\nprocess. Of course, in a normal web server, there may be many\nopen connections, and it is not reasonable to abruptly shut those down\nbecause an error was triggered by someone else.
\nThe better approach is to send an error response to the request that\ntriggered the error, while letting the others finish in their normal\ntime, and stop listening for new requests in that worker.
\nIn this way, domain
usage goes hand-in-hand with the cluster module,\nsince the primary process can fork a new worker when a worker\nencounters an error. For Node.js programs that scale to multiple\nmachines, the terminating proxy or service registry can take note of\nthe failure, and react accordingly.
For example, this is not a good idea:
\n// XXX WARNING! BAD IDEA!\n\nconst d = require('node:domain').create();\nd.on('error', (er) => {\n // The error won't crash the process, but what it does is worse!\n // Though we've prevented abrupt process restarting, we are leaking\n // a lot of resources if this ever happens.\n // This is no better than process.on('uncaughtException')!\n console.log(`error, but oh well ${er.message}`);\n});\nd.run(() => {\n require('node:http').createServer((req, res) => {\n handleRequest(req, res);\n }).listen(PORT);\n});\n
\nBy using the context of a domain, and the resilience of separating our\nprogram into multiple worker processes, we can react more\nappropriately, and handle errors with much greater safety.
\n// Much better!\n\nconst cluster = require('node:cluster');\nconst PORT = +process.env.PORT || 1337;\n\nif (cluster.isPrimary) {\n // A more realistic scenario would have more than 2 workers,\n // and perhaps not put the primary and worker in the same file.\n //\n // It is also possible to get a bit fancier about logging, and\n // implement whatever custom logic is needed to prevent DoS\n // attacks and other bad behavior.\n //\n // See the options in the cluster documentation.\n //\n // The important thing is that the primary does very little,\n // increasing our resilience to unexpected errors.\n\n cluster.fork();\n cluster.fork();\n\n cluster.on('disconnect', (worker) => {\n console.error('disconnect!');\n cluster.fork();\n });\n\n} else {\n // the worker\n //\n // This is where we put our bugs!\n\n const domain = require('node:domain');\n\n // See the cluster documentation for more details about using\n // worker processes to serve requests. How it works, caveats, etc.\n\n const server = require('node:http').createServer((req, res) => {\n const d = domain.create();\n d.on('error', (er) => {\n console.error(`error ${er.stack}`);\n\n // We're in dangerous territory!\n // By definition, something unexpected occurred,\n // which we probably didn't want.\n // Anything can happen now! Be very careful!\n\n try {\n // Make sure we close down within 30 seconds\n const killtimer = setTimeout(() => {\n process.exit(1);\n }, 30000);\n // But don't keep the process open just for that!\n killtimer.unref();\n\n // Stop taking new requests.\n server.close();\n\n // Let the primary know we're dead. This will trigger a\n // 'disconnect' in the cluster primary, and then it will fork\n // a new worker.\n cluster.worker.disconnect();\n\n // Try to send an error to the request that triggered the problem\n res.statusCode = 500;\n res.setHeader('content-type', 'text/plain');\n res.end('Oops, there was a problem!\\n');\n } catch (er2) {\n // Oh well, not much we can do at this point.\n console.error(`Error sending 500! ${er2.stack}`);\n }\n });\n\n // Because req and res were created before this domain existed,\n // we need to explicitly add them.\n // See the explanation of implicit vs explicit binding below.\n d.add(req);\n d.add(res);\n\n // Now run the handler function in the domain.\n d.run(() => {\n handleRequest(req, res);\n });\n });\n server.listen(PORT);\n}\n\n// This part is not important. Just an example routing thing.\n// Put fancy application logic here.\nfunction handleRequest(req, res) {\n switch (req.url) {\n case '/error':\n // We do some async stuff, and then...\n setTimeout(() => {\n // Whoops!\n flerb.bark();\n }, timeout);\n break;\n default:\n res.end('ok');\n }\n}\n
"
},
{
"textRaw": "Additions to `Error` objects",
"name": "Additions to `Error` objects",
"type": "misc",
"desc": "Any time an Error
object is routed through a domain, a few extra fields\nare added to it.
error.domain
The domain that first handled the error.error.domainEmitter
The event emitter that emitted an 'error'
event\nwith the error object.error.domainBound
The callback function which was bound to the\ndomain, and passed an error as its first argument.error.domainThrown
A boolean indicating whether the error was\nthrown, emitted, or passed to a bound callback function.If domains are in use, then all new EventEmitter
objects (including\nStream objects, requests, responses, etc.) will be implicitly bound to\nthe active domain at the time of their creation.
Additionally, callbacks passed to low-level event loop requests (such as\nto fs.open()
, or other callback-taking methods) will automatically be\nbound to the active domain. If they throw, then the domain will catch\nthe error.
In order to prevent excessive memory usage, Domain
objects themselves\nare not implicitly added as children of the active domain. If they\nwere, then it would be too easy to prevent request and response objects\nfrom being properly garbage collected.
To nest Domain
objects as children of a parent Domain
they must be\nexplicitly added.
Implicit binding routes thrown errors and 'error'
events to the\nDomain
's 'error'
event, but does not register the EventEmitter
on the\nDomain
.\nImplicit binding only takes care of thrown errors and 'error'
events.
Sometimes, the domain in use is not the one that ought to be used for a\nspecific event emitter. Or, the event emitter could have been created\nin the context of one domain, but ought to instead be bound to some\nother domain.
\nFor example, there could be one domain in use for an HTTP server, but\nperhaps we would like to have a separate domain to use for each request.
\nThat is possible via explicit binding.
\n// Create a top-level domain for the server\nconst domain = require('node:domain');\nconst http = require('node:http');\nconst serverDomain = domain.create();\n\nserverDomain.run(() => {\n // Server is created in the scope of serverDomain\n http.createServer((req, res) => {\n // Req and res are also created in the scope of serverDomain\n // however, we'd prefer to have a separate domain for each request.\n // create it first thing, and add req and res to it.\n const reqd = domain.create();\n reqd.add(req);\n reqd.add(res);\n reqd.on('error', (er) => {\n console.error('Error', er, req.url);\n try {\n res.writeHead(500);\n res.end('Error occurred, sorry.');\n } catch (er2) {\n console.error('Error sending 500', er2, req.url);\n }\n });\n }).listen(1337);\n});\n
"
}
],
"methods": [
{
"textRaw": "`domain.create()`",
"type": "method",
"name": "create",
"signatures": [
{
"return": {
"textRaw": "Returns: {Domain}",
"name": "return",
"type": "Domain"
},
"params": []
}
]
}
],
"classes": [
{
"textRaw": "Class: `Domain`",
"type": "class",
"name": "Domain",
"desc": "The Domain
class encapsulates the functionality of routing errors and\nuncaught exceptions to the active Domain
object.
To handle the errors that it catches, listen to its 'error'
event.
An array of timers and event emitters that have been explicitly added\nto the domain.
" } ], "methods": [ { "textRaw": "`domain.add(emitter)`", "type": "method", "name": "add", "signatures": [ { "params": [ { "textRaw": "`emitter` {EventEmitter|Timer} emitter or timer to be added to the domain", "name": "emitter", "type": "EventEmitter|Timer", "desc": "emitter or timer to be added to the domain" } ] } ], "desc": "Explicitly adds an emitter to the domain. If any event handlers called by\nthe emitter throw an error, or if the emitter emits an 'error'
event, it\nwill be routed to the domain's 'error'
event, just like with implicit\nbinding.
This also works with timers that are returned from setInterval()
and\nsetTimeout()
. If their callback function throws, it will be caught by\nthe domain 'error'
handler.
If the Timer or EventEmitter
was already bound to a domain, it is removed\nfrom that one, and bound to this one instead.
The returned function will be a wrapper around the supplied callback\nfunction. When the returned function is called, any errors that are\nthrown will be routed to the domain's 'error'
event.
const d = domain.create();\n\nfunction readSomeFile(filename, cb) {\n fs.readFile(filename, 'utf8', d.bind((er, data) => {\n // If this throws, it will also be passed to the domain.\n return cb(er, data ? JSON.parse(data) : null);\n }));\n}\n\nd.on('error', (er) => {\n // An error occurred somewhere. If we throw it now, it will crash the program\n // with the normal line number and stack message.\n});\n
"
},
{
"textRaw": "`domain.enter()`",
"type": "method",
"name": "enter",
"signatures": [
{
"params": []
}
],
"desc": "The enter()
method is plumbing used by the run()
, bind()
, and\nintercept()
methods to set the active domain. It sets domain.active
and\nprocess.domain
to the domain, and implicitly pushes the domain onto the domain\nstack managed by the domain module (see domain.exit()
for details on the\ndomain stack). The call to enter()
delimits the beginning of a chain of\nasynchronous calls and I/O operations bound to a domain.
Calling enter()
changes only the active domain, and does not alter the domain\nitself. enter()
and exit()
can be called an arbitrary number of times on a\nsingle domain.
The exit()
method exits the current domain, popping it off the domain stack.\nAny time execution is going to switch to the context of a different chain of\nasynchronous calls, it's important to ensure that the current domain is exited.\nThe call to exit()
delimits either the end of or an interruption to the chain\nof asynchronous calls and I/O operations bound to a domain.
If there are multiple, nested domains bound to the current execution context,\nexit()
will exit any domains nested within this domain.
Calling exit()
changes only the active domain, and does not alter the domain\nitself. enter()
and exit()
can be called an arbitrary number of times on a\nsingle domain.
This method is almost identical to domain.bind(callback)
. However, in\naddition to catching thrown errors, it will also intercept Error
\nobjects sent as the first argument to the function.
In this way, the common if (err) return callback(err);
pattern can be replaced\nwith a single error handler in a single place.
const d = domain.create();\n\nfunction readSomeFile(filename, cb) {\n fs.readFile(filename, 'utf8', d.intercept((data) => {\n // Note, the first argument is never passed to the\n // callback since it is assumed to be the 'Error' argument\n // and thus intercepted by the domain.\n\n // If this throws, it will also be passed to the domain\n // so the error-handling logic can be moved to the 'error'\n // event on the domain instead of being repeated throughout\n // the program.\n return cb(null, JSON.parse(data));\n }));\n}\n\nd.on('error', (er) => {\n // An error occurred somewhere. If we throw it now, it will crash the program\n // with the normal line number and stack message.\n});\n
"
},
{
"textRaw": "`domain.remove(emitter)`",
"type": "method",
"name": "remove",
"signatures": [
{
"params": [
{
"textRaw": "`emitter` {EventEmitter|Timer} emitter or timer to be removed from the domain",
"name": "emitter",
"type": "EventEmitter|Timer",
"desc": "emitter or timer to be removed from the domain"
}
]
}
],
"desc": "The opposite of domain.add(emitter)
. Removes domain handling from the\nspecified emitter.
Run the supplied function in the context of the domain, implicitly\nbinding all event emitters, timers, and low-level requests that are\ncreated in that context. Optionally, arguments can be passed to\nthe function.
\nThis is the most basic way to use a domain.
\nconst domain = require('node:domain');\nconst fs = require('node:fs');\nconst d = domain.create();\nd.on('error', (er) => {\n console.error('Caught error!', er);\n});\nd.run(() => {\n process.nextTick(() => {\n setTimeout(() => { // Simulating some various async stuff\n fs.open('non-existent file', 'r', (er, fd) => {\n if (er) throw er;\n // proceed...\n });\n }, 100);\n });\n});\n
\nIn this example, the d.on('error')
handler will be triggered, rather\nthan crashing the program.
As of Node.js 8.0.0, the handlers of promises are run inside the domain in\nwhich the call to .then()
or .catch()
itself was made:
const d1 = domain.create();\nconst d2 = domain.create();\n\nlet p;\nd1.run(() => {\n p = Promise.resolve(42);\n});\n\nd2.run(() => {\n p.then((v) => {\n // running in d2\n });\n});\n
\nA callback may be bound to a specific domain using domain.bind(callback)
:
const d1 = domain.create();\nconst d2 = domain.create();\n\nlet p;\nd1.run(() => {\n p = Promise.resolve(42);\n});\n\nd2.run(() => {\n p.then(p.domain.bind((v) => {\n // running in d1\n }));\n});\n
\nDomains will not interfere with the error handling mechanisms for\npromises. In other words, no 'error'
event will be emitted for unhandled\nPromise
rejections.
Source Code: lib/events.js
\nMuch of the Node.js core API is built around an idiomatic asynchronous\nevent-driven architecture in which certain kinds of objects (called \"emitters\")\nemit named events that cause Function
objects (\"listeners\") to be called.
For instance: a net.Server
object emits an event each time a peer\nconnects to it; a fs.ReadStream
emits an event when the file is opened;\na stream emits an event whenever data is available to be read.
All objects that emit events are instances of the EventEmitter
class. These\nobjects expose an eventEmitter.on()
function that allows one or more\nfunctions to be attached to named events emitted by the object. Typically,\nevent names are camel-cased strings but any valid JavaScript property key\ncan be used.
When the EventEmitter
object emits an event, all of the functions attached\nto that specific event are called synchronously. Any values returned by the\ncalled listeners are ignored and discarded.
The following example shows a simple EventEmitter
instance with a single\nlistener. The eventEmitter.on()
method is used to register listeners, while\nthe eventEmitter.emit()
method is used to trigger the event.
import { EventEmitter } from 'node:events';\n\nclass MyEmitter extends EventEmitter {}\n\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {\n console.log('an event occurred!');\n});\nmyEmitter.emit('event');\n
\nconst EventEmitter = require('node:events');\n\nclass MyEmitter extends EventEmitter {}\n\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {\n console.log('an event occurred!');\n});\nmyEmitter.emit('event');\n
",
"modules": [
{
"textRaw": "Passing arguments and `this` to listeners",
"name": "passing_arguments_and_`this`_to_listeners",
"desc": "The eventEmitter.emit()
method allows an arbitrary set of arguments to be\npassed to the listener functions. Keep in mind that when\nan ordinary listener function is called, the standard this
keyword\nis intentionally set to reference the EventEmitter
instance to which the\nlistener is attached.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', function(a, b) {\n console.log(a, b, this, this === myEmitter);\n // Prints:\n // a b MyEmitter {\n // _events: [Object: null prototype] { event: [Function (anonymous)] },\n // _eventsCount: 1,\n // _maxListeners: undefined,\n // [Symbol(shapeMode)]: false,\n // [Symbol(kCapture)]: false\n // } true\n});\nmyEmitter.emit('event', 'a', 'b');\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', function(a, b) {\n console.log(a, b, this, this === myEmitter);\n // Prints:\n // a b MyEmitter {\n // _events: [Object: null prototype] { event: [Function (anonymous)] },\n // _eventsCount: 1,\n // _maxListeners: undefined,\n // [Symbol(shapeMode)]: false,\n // [Symbol(kCapture)]: false\n // } true\n});\nmyEmitter.emit('event', 'a', 'b');\n
\nIt is possible to use ES6 Arrow Functions as listeners, however, when doing so,\nthe this
keyword will no longer reference the EventEmitter
instance:
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n console.log(a, b, this);\n // Prints: a b undefined\n});\nmyEmitter.emit('event', 'a', 'b');\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n console.log(a, b, this);\n // Prints: a b {}\n});\nmyEmitter.emit('event', 'a', 'b');\n
",
"type": "module",
"displayName": "Passing arguments and `this` to listeners"
},
{
"textRaw": "Asynchronous vs. synchronous",
"name": "asynchronous_vs._synchronous",
"desc": "The EventEmitter
calls all listeners synchronously in the order in which\nthey were registered. This ensures the proper sequencing of\nevents and helps avoid race conditions and logic errors. When appropriate,\nlistener functions can switch to an asynchronous mode of operation using\nthe setImmediate()
or process.nextTick()
methods:
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n setImmediate(() => {\n console.log('this happens asynchronously');\n });\n});\nmyEmitter.emit('event', 'a', 'b');\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n setImmediate(() => {\n console.log('this happens asynchronously');\n });\n});\nmyEmitter.emit('event', 'a', 'b');\n
",
"type": "module",
"displayName": "Asynchronous vs. synchronous"
},
{
"textRaw": "Handling events only once",
"name": "handling_events_only_once",
"desc": "When a listener is registered using the eventEmitter.on()
method, that\nlistener is invoked every time the named event is emitted.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nlet m = 0;\nmyEmitter.on('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n// Prints: 1\nmyEmitter.emit('event');\n// Prints: 2\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nlet m = 0;\nmyEmitter.on('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n// Prints: 1\nmyEmitter.emit('event');\n// Prints: 2\n
\nUsing the eventEmitter.once()
method, it is possible to register a listener\nthat is called at most once for a particular event. Once the event is emitted,\nthe listener is unregistered and then called.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nlet m = 0;\nmyEmitter.once('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n// Prints: 1\nmyEmitter.emit('event');\n// Ignored\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nlet m = 0;\nmyEmitter.once('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n// Prints: 1\nmyEmitter.emit('event');\n// Ignored\n
",
"type": "module",
"displayName": "Handling events only once"
},
{
"textRaw": "Error events",
"name": "error_events",
"desc": "When an error occurs within an EventEmitter
instance, the typical action is\nfor an 'error'
event to be emitted. These are treated as special cases\nwithin Node.js.
If an EventEmitter
does not have at least one listener registered for the\n'error'
event, and an 'error'
event is emitted, the error is thrown, a\nstack trace is printed, and the Node.js process exits.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.emit('error', new Error('whoops!'));\n// Throws and crashes Node.js\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.emit('error', new Error('whoops!'));\n// Throws and crashes Node.js\n
\nTo guard against crashing the Node.js process the domain
module can be\nused. (Note, however, that the node:domain
module is deprecated.)
As a best practice, listeners should always be added for the 'error'
events.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('error', (err) => {\n console.error('whoops! there was an error');\n});\nmyEmitter.emit('error', new Error('whoops!'));\n// Prints: whoops! there was an error\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\nmyEmitter.on('error', (err) => {\n console.error('whoops! there was an error');\n});\nmyEmitter.emit('error', new Error('whoops!'));\n// Prints: whoops! there was an error\n
\nIt is possible to monitor 'error'
events without consuming the emitted error\nby installing a listener using the symbol events.errorMonitor
.
import { EventEmitter, errorMonitor } from 'node:events';\n\nconst myEmitter = new EventEmitter();\nmyEmitter.on(errorMonitor, (err) => {\n MyMonitoringTool.log(err);\n});\nmyEmitter.emit('error', new Error('whoops!'));\n// Still throws and crashes Node.js\n
\nconst { EventEmitter, errorMonitor } = require('node:events');\n\nconst myEmitter = new EventEmitter();\nmyEmitter.on(errorMonitor, (err) => {\n MyMonitoringTool.log(err);\n});\nmyEmitter.emit('error', new Error('whoops!'));\n// Still throws and crashes Node.js\n
",
"type": "module",
"displayName": "Error events"
},
{
"textRaw": "Capture rejections of promises",
"name": "capture_rejections_of_promises",
"desc": "Using async
functions with event handlers is problematic, because it\ncan lead to an unhandled rejection in case of a thrown exception:
import { EventEmitter } from 'node:events';\nconst ee = new EventEmitter();\nee.on('something', async (value) => {\n throw new Error('kaboom');\n});\n
\nconst EventEmitter = require('node:events');\nconst ee = new EventEmitter();\nee.on('something', async (value) => {\n throw new Error('kaboom');\n});\n
\nThe captureRejections
option in the EventEmitter
constructor or the global\nsetting change this behavior, installing a .then(undefined, handler)
\nhandler on the Promise
. This handler routes the exception\nasynchronously to the Symbol.for('nodejs.rejection')
method\nif there is one, or to 'error'
event handler if there is none.
import { EventEmitter } from 'node:events';\nconst ee1 = new EventEmitter({ captureRejections: true });\nee1.on('something', async (value) => {\n throw new Error('kaboom');\n});\n\nee1.on('error', console.log);\n\nconst ee2 = new EventEmitter({ captureRejections: true });\nee2.on('something', async (value) => {\n throw new Error('kaboom');\n});\n\nee2[Symbol.for('nodejs.rejection')] = console.log;\n
\nconst EventEmitter = require('node:events');\nconst ee1 = new EventEmitter({ captureRejections: true });\nee1.on('something', async (value) => {\n throw new Error('kaboom');\n});\n\nee1.on('error', console.log);\n\nconst ee2 = new EventEmitter({ captureRejections: true });\nee2.on('something', async (value) => {\n throw new Error('kaboom');\n});\n\nee2[Symbol.for('nodejs.rejection')] = console.log;\n
\nSetting events.captureRejections = true
will change the default for all\nnew instances of EventEmitter
.
import { EventEmitter } from 'node:events';\n\nEventEmitter.captureRejections = true;\nconst ee1 = new EventEmitter();\nee1.on('something', async (value) => {\n throw new Error('kaboom');\n});\n\nee1.on('error', console.log);\n
\nconst events = require('node:events');\nevents.captureRejections = true;\nconst ee1 = new events.EventEmitter();\nee1.on('something', async (value) => {\n throw new Error('kaboom');\n});\n\nee1.on('error', console.log);\n
\nThe 'error'
events that are generated by the captureRejections
behavior\ndo not have a catch handler to avoid infinite error loops: the\nrecommendation is to not use async
functions as 'error'
event handlers.
The EventTarget
and Event
objects are a Node.js-specific implementation\nof the EventTarget
Web API that are exposed by some Node.js core APIs.
const target = new EventTarget();\n\ntarget.addEventListener('foo', (event) => {\n console.log('foo event happened!');\n});\n
",
"modules": [
{
"textRaw": "Node.js `EventTarget` vs. DOM `EventTarget`",
"name": "node.js_`eventtarget`_vs._dom_`eventtarget`",
"desc": "There are two key differences between the Node.js EventTarget
and the\nEventTarget
Web API:
EventTarget
instances may be hierarchical, there is no\nconcept of hierarchy and event propagation in Node.js. That is, an event\ndispatched to an EventTarget
does not propagate through a hierarchy of\nnested target objects that may each have their own set of handlers for the\nevent.EventTarget
, if an event listener is an async function\nor returns a Promise
, and the returned Promise
rejects, the rejection\nis automatically captured and handled the same way as a listener that\nthrows synchronously (see EventTarget
error handling for details).The NodeEventTarget
object implements a modified subset of the\nEventEmitter
API that allows it to closely emulate an EventEmitter
in\ncertain situations. A NodeEventTarget
is not an instance of EventEmitter
\nand cannot be used in place of an EventEmitter
in most cases.
EventEmitter
, any given listener
can be registered at most once\nper event type
. Attempts to register a listener
multiple times are\nignored.NodeEventTarget
does not emulate the full EventEmitter
API.\nSpecifically the prependListener()
, prependOnceListener()
,\nrawListeners()
, and errorMonitor
APIs are not emulated.\nThe 'newListener'
and 'removeListener'
events will also not be emitted.NodeEventTarget
does not implement any special default behavior\nfor events with type 'error'
.NodeEventTarget
supports EventListener
objects as well as\nfunctions as handlers for all event types.Event listeners registered for an event type
may either be JavaScript\nfunctions or objects with a handleEvent
property whose value is a function.
In either case, the handler function is invoked with the event
argument\npassed to the eventTarget.dispatchEvent()
function.
Async functions may be used as event listeners. If an async handler function\nrejects, the rejection is captured and handled as described in\nEventTarget
error handling.
An error thrown by one handler function does not prevent the other handlers\nfrom being invoked.
\nThe return value of a handler function is ignored.
\nHandlers are always invoked in the order they were added.
\nHandler functions may mutate the event
object.
function handler1(event) {\n console.log(event.type); // Prints 'foo'\n event.a = 1;\n}\n\nasync function handler2(event) {\n console.log(event.type); // Prints 'foo'\n console.log(event.a); // Prints 1\n}\n\nconst handler3 = {\n handleEvent(event) {\n console.log(event.type); // Prints 'foo'\n },\n};\n\nconst handler4 = {\n async handleEvent(event) {\n console.log(event.type); // Prints 'foo'\n },\n};\n\nconst target = new EventTarget();\n\ntarget.addEventListener('foo', handler1);\ntarget.addEventListener('foo', handler2);\ntarget.addEventListener('foo', handler3);\ntarget.addEventListener('foo', handler4, { once: true });\n
",
"type": "module",
"displayName": "Event listener"
},
{
"textRaw": "`EventTarget` error handling",
"name": "`eventtarget`_error_handling",
"desc": "When a registered event listener throws (or returns a Promise that rejects),\nby default the error is treated as an uncaught exception on\nprocess.nextTick()
. This means uncaught exceptions in EventTarget
s will\nterminate the Node.js process by default.
Throwing within an event listener will not stop the other registered handlers\nfrom being invoked.
\nThe EventTarget
does not implement any special default handling for 'error'
\ntype events like EventEmitter
.
Currently errors are first forwarded to the process.on('error')
event\nbefore reaching process.on('uncaughtException')
. This behavior is\ndeprecated and will change in a future release to align EventTarget
with\nother Node.js APIs. Any code relying on the process.on('error')
event should\nbe aligned with the new behavior.
The Event
object is an adaptation of the Event
Web API. Instances\nare created internally by Node.js.
This is not used in Node.js and is provided purely for completeness.
", "shortDesc": "Always returns `false`." }, { "textRaw": "`cancelBubble` Type: {boolean}", "type": "boolean", "name": "Type", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "stability": 3, "stabilityText": "Legacy: Use [`event.stopPropagation()`][] instead.", "desc": "Alias for event.stopPropagation()
if set to true
. This is not used\nin Node.js and is provided purely for completeness.
This is not used in Node.js and is provided purely for completeness.
", "shortDesc": "Always returns `false`." }, { "textRaw": "`currentTarget` Type: {EventTarget} The `EventTarget` dispatching the event.", "type": "EventTarget", "name": "Type", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "desc": "Alias for event.target
.
Is true
if cancelable
is true
and event.preventDefault()
has been\ncalled.
This is not used in Node.js and is provided purely for completeness.
", "shortDesc": "Returns `0` while an event is not being dispatched, `2` while it is being dispatched." }, { "textRaw": "`isTrusted` Type: {boolean}", "type": "boolean", "name": "Type", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "desc": "The <AbortSignal> \"abort\"
event is emitted with isTrusted
set to true
. The\nvalue is false
in all other cases.
The value of event.returnValue
is always the opposite of event.defaultPrevented
.\nThis is not used in Node.js and is provided purely for completeness.
Alias for event.target
.
The millisecond timestamp when the Event
object was created.
The event type identifier.
" } ], "methods": [ { "textRaw": "`event.composedPath()`", "type": "method", "name": "composedPath", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Returns an array containing the current EventTarget
as the only entry or\nempty if the event is not being dispatched. This is not used in\nNode.js and is provided purely for completeness.
Redundant with event constructors and incapable of setting composed
.\nThis is not used in Node.js and is provided purely for completeness.
Sets the defaultPrevented
property to true
if cancelable
is true
.
Stops the invocation of event listeners after the current one completes.
" }, { "textRaw": "`event.stopPropagation()`", "type": "method", "name": "stopPropagation", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "This is not used in Node.js and is provided purely for completeness.
" } ] }, { "textRaw": "Class: `EventTarget`", "type": "class", "name": "EventTarget", "meta": { "added": [ "v14.5.0" ], "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/35496", "description": "The `EventTarget` class is now available through the global object." } ] }, "methods": [ { "textRaw": "`eventTarget.addEventListener(type, listener[, options])`", "type": "method", "name": "addEventListener", "meta": { "added": [ "v14.5.0" ], "changes": [ { "version": "v15.4.0", "pr-url": "https://github.com/nodejs/node/pull/36258", "description": "add support for `signal` option." } ] }, "signatures": [ { "params": [ { "textRaw": "`type` {string}", "name": "type", "type": "string" }, { "textRaw": "`listener` {Function|EventListener}", "name": "listener", "type": "Function|EventListener" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`once` {boolean} When `true`, the listener is automatically removed when it is first invoked. **Default:** `false`.", "name": "once", "type": "boolean", "default": "`false`", "desc": "When `true`, the listener is automatically removed when it is first invoked." }, { "textRaw": "`passive` {boolean} When `true`, serves as a hint that the listener will not call the `Event` object's `preventDefault()` method. **Default:** `false`.", "name": "passive", "type": "boolean", "default": "`false`", "desc": "When `true`, serves as a hint that the listener will not call the `Event` object's `preventDefault()` method." }, { "textRaw": "`capture` {boolean} Not directly used by Node.js. Added for API completeness. **Default:** `false`.", "name": "capture", "type": "boolean", "default": "`false`", "desc": "Not directly used by Node.js. Added for API completeness." }, { "textRaw": "`signal` {AbortSignal} The listener will be removed when the given AbortSignal object's `abort()` method is called.", "name": "signal", "type": "AbortSignal", "desc": "The listener will be removed when the given AbortSignal object's `abort()` method is called." } ] } ] } ], "desc": "Adds a new handler for the type
event. Any given listener
is added\nonly once per type
and per capture
option value.
If the once
option is true
, the listener
is removed after the\nnext time a type
event is dispatched.
The capture
option is not used by Node.js in any functional way other than\ntracking registered event listeners per the EventTarget
specification.\nSpecifically, the capture
option is used as part of the key when registering\na listener
. Any individual listener
may be added once with\ncapture = false
, and once with capture = true
.
function handler(event) {}\n\nconst target = new EventTarget();\ntarget.addEventListener('foo', handler, { capture: true }); // first\ntarget.addEventListener('foo', handler, { capture: false }); // second\n\n// Removes the second instance of handler\ntarget.removeEventListener('foo', handler);\n\n// Removes the first instance of handler\ntarget.removeEventListener('foo', handler, { capture: true });\n
"
},
{
"textRaw": "`eventTarget.dispatchEvent(event)`",
"type": "method",
"name": "dispatchEvent",
"meta": {
"added": [
"v14.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `true` if either event's `cancelable` attribute value is false or its `preventDefault()` method was not invoked, otherwise `false`.",
"name": "return",
"type": "boolean",
"desc": "`true` if either event's `cancelable` attribute value is false or its `preventDefault()` method was not invoked, otherwise `false`."
},
"params": [
{
"textRaw": "`event` {Event}",
"name": "event",
"type": "Event"
}
]
}
],
"desc": "Dispatches the event
to the list of handlers for event.type
.
The registered event listeners is synchronously invoked in the order they\nwere registered.
" }, { "textRaw": "`eventTarget.removeEventListener(type, listener[, options])`", "type": "method", "name": "removeEventListener", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`type` {string}", "name": "type", "type": "string" }, { "textRaw": "`listener` {Function|EventListener}", "name": "listener", "type": "Function|EventListener" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`capture` {boolean}", "name": "capture", "type": "boolean" } ] } ] } ], "desc": "Removes the listener
from the list of handlers for event type
.
The CustomEvent
object is an adaptation of the CustomEvent
Web API.\nInstances are created internally by Node.js.
Read-only.
", "shortDesc": "Returns custom data passed when initializing." } ] }, { "textRaw": "Class: `NodeEventTarget`", "type": "class", "name": "NodeEventTarget", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "desc": "The NodeEventTarget
is a Node.js-specific extension to EventTarget
\nthat emulates a subset of the EventEmitter
API.
Node.js-specific extension to the EventTarget
class that emulates the\nequivalent EventEmitter
API. The only difference between addListener()
and\naddEventListener()
is that addListener()
will return a reference to the\nEventTarget
.
Node.js-specific extension to the EventTarget
class that dispatches the\narg
to the list of handlers for type
.
Node.js-specific extension to the EventTarget
class that returns an array\nof event type
names for which event listeners are registered.
Node.js-specific extension to the EventTarget
class that returns the number\nof event listeners registered for the type
.
Node.js-specific extension to the EventTarget
class that sets the number\nof max event listeners as n
.
Node.js-specific extension to the EventTarget
class that returns the number\nof max event listeners.
Node.js-specific alias for eventTarget.removeEventListener()
.
Node.js-specific alias for eventTarget.addEventListener()
.
Node.js-specific extension to the EventTarget
class that adds a once
\nlistener for the given event type
. This is equivalent to calling on
\nwith the once
option set to true
.
Node.js-specific extension to the EventTarget
class. If type
is specified,\nremoves all registered listeners for type
, otherwise removes all registered\nlisteners.
Node.js-specific extension to the EventTarget
class that removes the\nlistener
for the given type
. The only difference between removeListener()
\nand removeEventListener()
is that removeListener()
will return a reference\nto the EventTarget
.
The EventEmitter
class is defined and exposed by the node:events
module:
import { EventEmitter } from 'node:events';\n
\nconst EventEmitter = require('node:events');\n
\nAll EventEmitter
s emit the event 'newListener'
when new listeners are\nadded and 'removeListener'
when existing listeners are removed.
It supports the following option:
\ncaptureRejections
<boolean> It enables\nautomatic capturing of promise rejection.\nDefault: false
.The EventEmitter
instance will emit its own 'newListener'
event before\na listener is added to its internal array of listeners.
Listeners registered for the 'newListener'
event are passed the event\nname and a reference to the listener being added.
The fact that the event is triggered before adding the listener has a subtle\nbut important side effect: any additional listeners registered to the same\nname
within the 'newListener'
callback are inserted before the\nlistener that is in the process of being added.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\n\nconst myEmitter = new MyEmitter();\n// Only do this once so we don't loop forever\nmyEmitter.once('newListener', (event, listener) => {\n if (event === 'event') {\n // Insert a new listener in front\n myEmitter.on('event', () => {\n console.log('B');\n });\n }\n});\nmyEmitter.on('event', () => {\n console.log('A');\n});\nmyEmitter.emit('event');\n// Prints:\n// B\n// A\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\n\nconst myEmitter = new MyEmitter();\n// Only do this once so we don't loop forever\nmyEmitter.once('newListener', (event, listener) => {\n if (event === 'event') {\n // Insert a new listener in front\n myEmitter.on('event', () => {\n console.log('B');\n });\n }\n});\nmyEmitter.on('event', () => {\n console.log('A');\n});\nmyEmitter.emit('event');\n// Prints:\n// B\n// A\n
"
},
{
"textRaw": "Event: `'removeListener'`",
"type": "event",
"name": "removeListener",
"meta": {
"added": [
"v0.9.3"
],
"changes": [
{
"version": [
"v6.1.0",
"v4.7.0"
],
"pr-url": "https://github.com/nodejs/node/pull/6394",
"description": "For listeners attached using `.once()`, the `listener` argument now yields the original listener function."
}
]
},
"params": [
{
"textRaw": "`eventName` {string|symbol} The event name",
"name": "eventName",
"type": "string|symbol",
"desc": "The event name"
},
{
"textRaw": "`listener` {Function} The event handler function",
"name": "listener",
"type": "Function",
"desc": "The event handler function"
}
],
"desc": "The 'removeListener'
event is emitted after the listener
is removed.
Alias for emitter.on(eventName, listener)
.
Synchronously calls each of the listeners registered for the event named\neventName
, in the order they were registered, passing the supplied arguments\nto each.
Returns true
if the event had listeners, false
otherwise.
import { EventEmitter } from 'node:events';\nconst myEmitter = new EventEmitter();\n\n// First listener\nmyEmitter.on('event', function firstListener() {\n console.log('Helloooo! first listener');\n});\n// Second listener\nmyEmitter.on('event', function secondListener(arg1, arg2) {\n console.log(`event with parameters ${arg1}, ${arg2} in second listener`);\n});\n// Third listener\nmyEmitter.on('event', function thirdListener(...args) {\n const parameters = args.join(', ');\n console.log(`event with parameters ${parameters} in third listener`);\n});\n\nconsole.log(myEmitter.listeners('event'));\n\nmyEmitter.emit('event', 1, 2, 3, 4, 5);\n\n// Prints:\n// [\n// [Function: firstListener],\n// [Function: secondListener],\n// [Function: thirdListener]\n// ]\n// Helloooo! first listener\n// event with parameters 1, 2 in second listener\n// event with parameters 1, 2, 3, 4, 5 in third listener\n
\nconst EventEmitter = require('node:events');\nconst myEmitter = new EventEmitter();\n\n// First listener\nmyEmitter.on('event', function firstListener() {\n console.log('Helloooo! first listener');\n});\n// Second listener\nmyEmitter.on('event', function secondListener(arg1, arg2) {\n console.log(`event with parameters ${arg1}, ${arg2} in second listener`);\n});\n// Third listener\nmyEmitter.on('event', function thirdListener(...args) {\n const parameters = args.join(', ');\n console.log(`event with parameters ${parameters} in third listener`);\n});\n\nconsole.log(myEmitter.listeners('event'));\n\nmyEmitter.emit('event', 1, 2, 3, 4, 5);\n\n// Prints:\n// [\n// [Function: firstListener],\n// [Function: secondListener],\n// [Function: thirdListener]\n// ]\n// Helloooo! first listener\n// event with parameters 1, 2 in second listener\n// event with parameters 1, 2, 3, 4, 5 in third listener\n
"
},
{
"textRaw": "`emitter.eventNames()`",
"type": "method",
"name": "eventNames",
"meta": {
"added": [
"v6.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Array}",
"name": "return",
"type": "Array"
},
"params": []
}
],
"desc": "Returns an array listing the events for which the emitter has registered\nlisteners. The values in the array are strings or Symbol
s.
import { EventEmitter } from 'node:events';\n\nconst myEE = new EventEmitter();\nmyEE.on('foo', () => {});\nmyEE.on('bar', () => {});\n\nconst sym = Symbol('symbol');\nmyEE.on(sym, () => {});\n\nconsole.log(myEE.eventNames());\n// Prints: [ 'foo', 'bar', Symbol(symbol) ]\n
\nconst EventEmitter = require('node:events');\n\nconst myEE = new EventEmitter();\nmyEE.on('foo', () => {});\nmyEE.on('bar', () => {});\n\nconst sym = Symbol('symbol');\nmyEE.on(sym, () => {});\n\nconsole.log(myEE.eventNames());\n// Prints: [ 'foo', 'bar', Symbol(symbol) ]\n
"
},
{
"textRaw": "`emitter.getMaxListeners()`",
"type": "method",
"name": "getMaxListeners",
"meta": {
"added": [
"v1.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": []
}
],
"desc": "Returns the current max listener value for the EventEmitter
which is either\nset by emitter.setMaxListeners(n)
or defaults to\nevents.defaultMaxListeners
.
Returns the number of listeners listening for the event named eventName
.\nIf listener
is provided, it will return how many times the listener is found\nin the list of the listeners of the event.
Returns a copy of the array of listeners for the event named eventName
.
server.on('connection', (stream) => {\n console.log('someone connected!');\n});\nconsole.log(util.inspect(server.listeners('connection')));\n// Prints: [ [Function] ]\n
"
},
{
"textRaw": "`emitter.off(eventName, listener)`",
"type": "method",
"name": "off",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {EventEmitter}",
"name": "return",
"type": "EventEmitter"
},
"params": [
{
"textRaw": "`eventName` {string|symbol}",
"name": "eventName",
"type": "string|symbol"
},
{
"textRaw": "`listener` {Function}",
"name": "listener",
"type": "Function"
}
]
}
],
"desc": "Alias for emitter.removeListener()
.
Adds the listener
function to the end of the listeners array for the\nevent named eventName
. No checks are made to see if the listener
has\nalready been added. Multiple calls passing the same combination of eventName
\nand listener
will result in the listener
being added, and called, multiple\ntimes.
server.on('connection', (stream) => {\n console.log('someone connected!');\n});\n
\nReturns a reference to the EventEmitter
, so that calls can be chained.
By default, event listeners are invoked in the order they are added. The\nemitter.prependListener()
method can be used as an alternative to add the\nevent listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';\nconst myEE = new EventEmitter();\nmyEE.on('foo', () => console.log('a'));\nmyEE.prependListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n// Prints:\n// b\n// a\n
\nconst EventEmitter = require('node:events');\nconst myEE = new EventEmitter();\nmyEE.on('foo', () => console.log('a'));\nmyEE.prependListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n// Prints:\n// b\n// a\n
"
},
{
"textRaw": "`emitter.once(eventName, listener)`",
"type": "method",
"name": "once",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {EventEmitter}",
"name": "return",
"type": "EventEmitter"
},
"params": [
{
"textRaw": "`eventName` {string|symbol} The name of the event.",
"name": "eventName",
"type": "string|symbol",
"desc": "The name of the event."
},
{
"textRaw": "`listener` {Function} The callback function",
"name": "listener",
"type": "Function",
"desc": "The callback function"
}
]
}
],
"desc": "Adds a one-time listener
function for the event named eventName
. The\nnext time eventName
is triggered, this listener is removed and then invoked.
server.once('connection', (stream) => {\n console.log('Ah, we have our first user!');\n});\n
\nReturns a reference to the EventEmitter
, so that calls can be chained.
By default, event listeners are invoked in the order they are added. The\nemitter.prependOnceListener()
method can be used as an alternative to add the\nevent listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';\nconst myEE = new EventEmitter();\nmyEE.once('foo', () => console.log('a'));\nmyEE.prependOnceListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n// Prints:\n// b\n// a\n
\nconst EventEmitter = require('node:events');\nconst myEE = new EventEmitter();\nmyEE.once('foo', () => console.log('a'));\nmyEE.prependOnceListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n// Prints:\n// b\n// a\n
"
},
{
"textRaw": "`emitter.prependListener(eventName, listener)`",
"type": "method",
"name": "prependListener",
"meta": {
"added": [
"v6.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {EventEmitter}",
"name": "return",
"type": "EventEmitter"
},
"params": [
{
"textRaw": "`eventName` {string|symbol} The name of the event.",
"name": "eventName",
"type": "string|symbol",
"desc": "The name of the event."
},
{
"textRaw": "`listener` {Function} The callback function",
"name": "listener",
"type": "Function",
"desc": "The callback function"
}
]
}
],
"desc": "Adds the listener
function to the beginning of the listeners array for the\nevent named eventName
. No checks are made to see if the listener
has\nalready been added. Multiple calls passing the same combination of eventName
\nand listener
will result in the listener
being added, and called, multiple\ntimes.
server.prependListener('connection', (stream) => {\n console.log('someone connected!');\n});\n
\nReturns a reference to the EventEmitter
, so that calls can be chained.
Adds a one-time listener
function for the event named eventName
to the\nbeginning of the listeners array. The next time eventName
is triggered, this\nlistener is removed, and then invoked.
server.prependOnceListener('connection', (stream) => {\n console.log('Ah, we have our first user!');\n});\n
\nReturns a reference to the EventEmitter
, so that calls can be chained.
Removes all listeners, or those of the specified eventName
.
It is bad practice to remove listeners added elsewhere in the code,\nparticularly when the EventEmitter
instance was created by some other\ncomponent or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter
, so that calls can be chained.
Removes the specified listener
from the listener array for the event named\neventName
.
const callback = (stream) => {\n console.log('someone connected!');\n};\nserver.on('connection', callback);\n// ...\nserver.removeListener('connection', callback);\n
\nremoveListener()
will remove, at most, one instance of a listener from the\nlistener array. If any single listener has been added multiple times to the\nlistener array for the specified eventName
, then removeListener()
must be\ncalled multiple times to remove each instance.
Once an event is emitted, all listeners attached to it at the\ntime of emitting are called in order. This implies that any\nremoveListener()
or removeAllListeners()
calls after emitting and\nbefore the last listener finishes execution will not remove them from\nemit()
in progress. Subsequent events behave as expected.
import { EventEmitter } from 'node:events';\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\n\nconst callbackA = () => {\n console.log('A');\n myEmitter.removeListener('event', callbackB);\n};\n\nconst callbackB = () => {\n console.log('B');\n};\n\nmyEmitter.on('event', callbackA);\n\nmyEmitter.on('event', callbackB);\n\n// callbackA removes listener callbackB but it will still be called.\n// Internal listener array at time of emit [callbackA, callbackB]\nmyEmitter.emit('event');\n// Prints:\n// A\n// B\n\n// callbackB is now removed.\n// Internal listener array [callbackA]\nmyEmitter.emit('event');\n// Prints:\n// A\n
\nconst EventEmitter = require('node:events');\nclass MyEmitter extends EventEmitter {}\nconst myEmitter = new MyEmitter();\n\nconst callbackA = () => {\n console.log('A');\n myEmitter.removeListener('event', callbackB);\n};\n\nconst callbackB = () => {\n console.log('B');\n};\n\nmyEmitter.on('event', callbackA);\n\nmyEmitter.on('event', callbackB);\n\n// callbackA removes listener callbackB but it will still be called.\n// Internal listener array at time of emit [callbackA, callbackB]\nmyEmitter.emit('event');\n// Prints:\n// A\n// B\n\n// callbackB is now removed.\n// Internal listener array [callbackA]\nmyEmitter.emit('event');\n// Prints:\n// A\n
\nBecause listeners are managed using an internal array, calling this will\nchange the position indices of any listener registered after the listener\nbeing removed. This will not impact the order in which listeners are called,\nbut it means that any copies of the listener array as returned by\nthe emitter.listeners()
method will need to be recreated.
When a single function has been added as a handler multiple times for a single\nevent (as in the example below), removeListener()
will remove the most\nrecently added instance. In the example the once('ping')
\nlistener is removed:
import { EventEmitter } from 'node:events';\nconst ee = new EventEmitter();\n\nfunction pong() {\n console.log('pong');\n}\n\nee.on('ping', pong);\nee.once('ping', pong);\nee.removeListener('ping', pong);\n\nee.emit('ping');\nee.emit('ping');\n
\nconst EventEmitter = require('node:events');\nconst ee = new EventEmitter();\n\nfunction pong() {\n console.log('pong');\n}\n\nee.on('ping', pong);\nee.once('ping', pong);\nee.removeListener('ping', pong);\n\nee.emit('ping');\nee.emit('ping');\n
\nReturns a reference to the EventEmitter
, so that calls can be chained.
By default EventEmitter
s will print a warning if more than 10
listeners are\nadded for a particular event. This is a useful default that helps finding\nmemory leaks. The emitter.setMaxListeners()
method allows the limit to be\nmodified for this specific EventEmitter
instance. The value can be set to\nInfinity
(or 0
) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter
, so that calls can be chained.
Returns a copy of the array of listeners for the event named eventName
,\nincluding any wrappers (such as those created by .once()
).
import { EventEmitter } from 'node:events';\nconst emitter = new EventEmitter();\nemitter.once('log', () => console.log('log once'));\n\n// Returns a new Array with a function `onceWrapper` which has a property\n// `listener` which contains the original listener bound above\nconst listeners = emitter.rawListeners('log');\nconst logFnWrapper = listeners[0];\n\n// Logs \"log once\" to the console and does not unbind the `once` event\nlogFnWrapper.listener();\n\n// Logs \"log once\" to the console and removes the listener\nlogFnWrapper();\n\nemitter.on('log', () => console.log('log persistently'));\n// Will return a new Array with a single function bound by `.on()` above\nconst newListeners = emitter.rawListeners('log');\n\n// Logs \"log persistently\" twice\nnewListeners[0]();\nemitter.emit('log');\n
\nconst EventEmitter = require('node:events');\nconst emitter = new EventEmitter();\nemitter.once('log', () => console.log('log once'));\n\n// Returns a new Array with a function `onceWrapper` which has a property\n// `listener` which contains the original listener bound above\nconst listeners = emitter.rawListeners('log');\nconst logFnWrapper = listeners[0];\n\n// Logs \"log once\" to the console and does not unbind the `once` event\nlogFnWrapper.listener();\n\n// Logs \"log once\" to the console and removes the listener\nlogFnWrapper();\n\nemitter.on('log', () => console.log('log persistently'));\n// Will return a new Array with a single function bound by `.on()` above\nconst newListeners = emitter.rawListeners('log');\n\n// Logs \"log persistently\" twice\nnewListeners[0]();\nemitter.emit('log');\n
"
}
],
"modules": [
{
"textRaw": "`emitter[Symbol.for('nodejs.rejection')](err, eventName[, ...args])`",
"name": "`emitter[symbol.for('nodejs.rejection')](err,_eventname[,_...args])`",
"meta": {
"added": [
"v13.4.0",
"v12.16.0"
],
"changes": [
{
"version": [
"v17.4.0",
"v16.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41267",
"description": "No longer experimental."
}
]
},
"desc": "\nThe Symbol.for('nodejs.rejection')
method is called in case a\npromise rejection happens when emitting an event and\ncaptureRejections
is enabled on the emitter.\nIt is possible to use events.captureRejectionSymbol
in\nplace of Symbol.for('nodejs.rejection')
.
import { EventEmitter, captureRejectionSymbol } from 'node:events';\n\nclass MyClass extends EventEmitter {\n constructor() {\n super({ captureRejections: true });\n }\n\n [captureRejectionSymbol](err, event, ...args) {\n console.log('rejection happened for', event, 'with', err, ...args);\n this.destroy(err);\n }\n\n destroy(err) {\n // Tear the resource down here.\n }\n}\n
\nconst { EventEmitter, captureRejectionSymbol } = require('node:events');\n\nclass MyClass extends EventEmitter {\n constructor() {\n super({ captureRejections: true });\n }\n\n [captureRejectionSymbol](err, event, ...args) {\n console.log('rejection happened for', event, 'with', err, ...args);\n this.destroy(err);\n }\n\n destroy(err) {\n // Tear the resource down here.\n }\n}\n
",
"type": "module",
"displayName": "`emitter[Symbol.for('nodejs.rejection')](err, eventName[, ...args])`"
}
]
},
{
"textRaw": "Class: `events.EventEmitterAsyncResource extends EventEmitter`",
"type": "class",
"name": "events.EventEmitterAsyncResource",
"meta": {
"added": [
"v17.4.0",
"v16.14.0"
],
"changes": []
},
"desc": "Integrates EventEmitter
with <AsyncResource> for EventEmitter
s that\nrequire manual async tracking. Specifically, all events emitted by instances\nof events.EventEmitterAsyncResource
will run within its async context.
import { EventEmitterAsyncResource, EventEmitter } from 'node:events';\nimport { notStrictEqual, strictEqual } from 'node:assert';\nimport { executionAsyncId, triggerAsyncId } from 'node:async_hooks';\n\n// Async tracking tooling will identify this as 'Q'.\nconst ee1 = new EventEmitterAsyncResource({ name: 'Q' });\n\n// 'foo' listeners will run in the EventEmitters async context.\nee1.on('foo', () => {\n strictEqual(executionAsyncId(), ee1.asyncId);\n strictEqual(triggerAsyncId(), ee1.triggerAsyncId);\n});\n\nconst ee2 = new EventEmitter();\n\n// 'foo' listeners on ordinary EventEmitters that do not track async\n// context, however, run in the same async context as the emit().\nee2.on('foo', () => {\n notStrictEqual(executionAsyncId(), ee2.asyncId);\n notStrictEqual(triggerAsyncId(), ee2.triggerAsyncId);\n});\n\nPromise.resolve().then(() => {\n ee1.emit('foo');\n ee2.emit('foo');\n});\n
\nconst { EventEmitterAsyncResource, EventEmitter } = require('node:events');\nconst { notStrictEqual, strictEqual } = require('node:assert');\nconst { executionAsyncId, triggerAsyncId } = require('node:async_hooks');\n\n// Async tracking tooling will identify this as 'Q'.\nconst ee1 = new EventEmitterAsyncResource({ name: 'Q' });\n\n// 'foo' listeners will run in the EventEmitters async context.\nee1.on('foo', () => {\n strictEqual(executionAsyncId(), ee1.asyncId);\n strictEqual(triggerAsyncId(), ee1.triggerAsyncId);\n});\n\nconst ee2 = new EventEmitter();\n\n// 'foo' listeners on ordinary EventEmitters that do not track async\n// context, however, run in the same async context as the emit().\nee2.on('foo', () => {\n notStrictEqual(executionAsyncId(), ee2.asyncId);\n notStrictEqual(triggerAsyncId(), ee2.triggerAsyncId);\n});\n\nPromise.resolve().then(() => {\n ee1.emit('foo');\n ee2.emit('foo');\n});\n
\nThe EventEmitterAsyncResource
class has the same methods and takes the\nsame options as EventEmitter
and AsyncResource
themselves.
The returned AsyncResource
object has an additional eventEmitter
property\nthat provides a reference to this EventEmitterAsyncResource
.
Call all destroy
hooks. This should only ever be called once. An error will\nbe thrown if it is called more than once. This must be manually called. If\nthe resource is left to be collected by the GC then the destroy
hooks will\nnever be called.
By default, a maximum of 10
listeners can be registered for any single\nevent. This limit can be changed for individual EventEmitter
instances\nusing the emitter.setMaxListeners(n)
method. To change the default\nfor all EventEmitter
instances, the events.defaultMaxListeners
\nproperty can be used. If this value is not a positive number, a RangeError
\nis thrown.
Take caution when setting the events.defaultMaxListeners
because the\nchange affects all EventEmitter
instances, including those created before\nthe change is made. However, calling emitter.setMaxListeners(n)
still has\nprecedence over events.defaultMaxListeners
.
This is not a hard limit. The EventEmitter
instance will allow\nmore listeners to be added but will output a trace warning to stderr indicating\nthat a \"possible EventEmitter memory leak\" has been detected. For any single\nEventEmitter
, the emitter.getMaxListeners()
and emitter.setMaxListeners()
\nmethods can be used to temporarily avoid this warning:
import { EventEmitter } from 'node:events';\nconst emitter = new EventEmitter();\nemitter.setMaxListeners(emitter.getMaxListeners() + 1);\nemitter.once('event', () => {\n // do stuff\n emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));\n});\n
\nconst EventEmitter = require('node:events');\nconst emitter = new EventEmitter();\nemitter.setMaxListeners(emitter.getMaxListeners() + 1);\nemitter.once('event', () => {\n // do stuff\n emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));\n});\n
\nThe --trace-warnings
command-line flag can be used to display the\nstack trace for such warnings.
The emitted warning can be inspected with process.on('warning')
and will\nhave the additional emitter
, type
, and count
properties, referring to\nthe event emitter instance, the event's name and the number of attached\nlisteners, respectively.\nIts name
property is set to 'MaxListenersExceededWarning'
.
This symbol shall be used to install a listener for only monitoring 'error'
\nevents. Listeners installed using this symbol are called before the regular\n'error'
listeners are called.
Installing a listener using this symbol does not change the behavior once an\n'error'
event is emitted. Therefore, the process will still crash if no\nregular 'error'
listener is installed.
Value: <boolean>
\nChange the default captureRejections
option on all new EventEmitter
objects.
Value: Symbol.for('nodejs.rejection')
See how to write a custom rejection handler.
" } ], "methods": [ { "textRaw": "`events.getEventListeners(emitterOrTarget, eventName)`", "type": "method", "name": "getEventListeners", "meta": { "added": [ "v15.2.0", "v14.17.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Function\\[]}", "name": "return", "type": "Function\\[]" }, "params": [ { "textRaw": "`emitterOrTarget` {EventEmitter|EventTarget}", "name": "emitterOrTarget", "type": "EventEmitter|EventTarget" }, { "textRaw": "`eventName` {string|symbol}", "name": "eventName", "type": "string|symbol" } ] } ], "desc": "Returns a copy of the array of listeners for the event named eventName
.
For EventEmitter
s this behaves exactly the same as calling .listeners
on\nthe emitter.
For EventTarget
s this is the only way to get the event listeners for the\nevent target. This is useful for debugging and diagnostic purposes.
import { getEventListeners, EventEmitter } from 'node:events';\n\n{\n const ee = new EventEmitter();\n const listener = () => console.log('Events are fun');\n ee.on('foo', listener);\n console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]\n}\n{\n const et = new EventTarget();\n const listener = () => console.log('Events are fun');\n et.addEventListener('foo', listener);\n console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]\n}\n
\nconst { getEventListeners, EventEmitter } = require('node:events');\n\n{\n const ee = new EventEmitter();\n const listener = () => console.log('Events are fun');\n ee.on('foo', listener);\n console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]\n}\n{\n const et = new EventTarget();\n const listener = () => console.log('Events are fun');\n et.addEventListener('foo', listener);\n console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]\n}\n
"
},
{
"textRaw": "`events.getMaxListeners(emitterOrTarget)`",
"type": "method",
"name": "getMaxListeners",
"meta": {
"added": [
"v19.9.0",
"v18.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
},
"params": [
{
"textRaw": "`emitterOrTarget` {EventEmitter|EventTarget}",
"name": "emitterOrTarget",
"type": "EventEmitter|EventTarget"
}
]
}
],
"desc": "Returns the currently set max amount of listeners.
\nFor EventEmitter
s this behaves exactly the same as calling .getMaxListeners
on\nthe emitter.
For EventTarget
s this is the only way to get the max event listeners for the\nevent target. If the number of event handlers on a single EventTarget exceeds\nthe max set, the EventTarget will print a warning.
import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';\n\n{\n const ee = new EventEmitter();\n console.log(getMaxListeners(ee)); // 10\n setMaxListeners(11, ee);\n console.log(getMaxListeners(ee)); // 11\n}\n{\n const et = new EventTarget();\n console.log(getMaxListeners(et)); // 10\n setMaxListeners(11, et);\n console.log(getMaxListeners(et)); // 11\n}\n
\nconst { getMaxListeners, setMaxListeners, EventEmitter } = require('node:events');\n\n{\n const ee = new EventEmitter();\n console.log(getMaxListeners(ee)); // 10\n setMaxListeners(11, ee);\n console.log(getMaxListeners(ee)); // 11\n}\n{\n const et = new EventTarget();\n console.log(getMaxListeners(et)); // 10\n setMaxListeners(11, et);\n console.log(getMaxListeners(et)); // 11\n}\n
"
},
{
"textRaw": "`events.once(emitter, name[, options])`",
"type": "method",
"name": "once",
"meta": {
"added": [
"v11.13.0",
"v10.16.0"
],
"changes": [
{
"version": "v15.0.0",
"pr-url": "https://github.com/nodejs/node/pull/34912",
"description": "The `signal` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise}",
"name": "return",
"type": "Promise"
},
"params": [
{
"textRaw": "`emitter` {EventEmitter}",
"name": "emitter",
"type": "EventEmitter"
},
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} Can be used to cancel waiting for the event.",
"name": "signal",
"type": "AbortSignal",
"desc": "Can be used to cancel waiting for the event."
}
]
}
]
}
],
"desc": "Creates a Promise
that is fulfilled when the EventEmitter
emits the given\nevent or that is rejected if the EventEmitter
emits 'error'
while waiting.\nThe Promise
will resolve with an array of all the arguments emitted to the\ngiven event.
This method is intentionally generic and works with the web platform\nEventTarget interface, which has no special\n'error'
event semantics and does not listen to the 'error'
event.
import { once, EventEmitter } from 'node:events';\nimport process from 'node:process';\n\nconst ee = new EventEmitter();\n\nprocess.nextTick(() => {\n ee.emit('myevent', 42);\n});\n\nconst [value] = await once(ee, 'myevent');\nconsole.log(value);\n\nconst err = new Error('kaboom');\nprocess.nextTick(() => {\n ee.emit('error', err);\n});\n\ntry {\n await once(ee, 'myevent');\n} catch (err) {\n console.error('error happened', err);\n}\n
\nconst { once, EventEmitter } = require('node:events');\n\nasync function run() {\n const ee = new EventEmitter();\n\n process.nextTick(() => {\n ee.emit('myevent', 42);\n });\n\n const [value] = await once(ee, 'myevent');\n console.log(value);\n\n const err = new Error('kaboom');\n process.nextTick(() => {\n ee.emit('error', err);\n });\n\n try {\n await once(ee, 'myevent');\n } catch (err) {\n console.error('error happened', err);\n }\n}\n\nrun();\n
\nThe special handling of the 'error'
event is only used when events.once()
\nis used to wait for another event. If events.once()
is used to wait for the\n'error'
event itself, then it is treated as any other kind of event without\nspecial handling:
import { EventEmitter, once } from 'node:events';\n\nconst ee = new EventEmitter();\n\nonce(ee, 'error')\n .then(([err]) => console.log('ok', err.message))\n .catch((err) => console.error('error', err.message));\n\nee.emit('error', new Error('boom'));\n\n// Prints: ok boom\n
\nconst { EventEmitter, once } = require('node:events');\n\nconst ee = new EventEmitter();\n\nonce(ee, 'error')\n .then(([err]) => console.log('ok', err.message))\n .catch((err) => console.error('error', err.message));\n\nee.emit('error', new Error('boom'));\n\n// Prints: ok boom\n
\nAn <AbortSignal> can be used to cancel waiting for the event:
\nimport { EventEmitter, once } from 'node:events';\n\nconst ee = new EventEmitter();\nconst ac = new AbortController();\n\nasync function foo(emitter, event, signal) {\n try {\n await once(emitter, event, { signal });\n console.log('event emitted!');\n } catch (error) {\n if (error.name === 'AbortError') {\n console.error('Waiting for the event was canceled!');\n } else {\n console.error('There was an error', error.message);\n }\n }\n}\n\nfoo(ee, 'foo', ac.signal);\nac.abort(); // Abort waiting for the event\nee.emit('foo'); // Prints: Waiting for the event was canceled!\n
\nconst { EventEmitter, once } = require('node:events');\n\nconst ee = new EventEmitter();\nconst ac = new AbortController();\n\nasync function foo(emitter, event, signal) {\n try {\n await once(emitter, event, { signal });\n console.log('event emitted!');\n } catch (error) {\n if (error.name === 'AbortError') {\n console.error('Waiting for the event was canceled!');\n } else {\n console.error('There was an error', error.message);\n }\n }\n}\n\nfoo(ee, 'foo', ac.signal);\nac.abort(); // Abort waiting for the event\nee.emit('foo'); // Prints: Waiting for the event was canceled!\n
",
"modules": [
{
"textRaw": "Awaiting multiple events emitted on `process.nextTick()`",
"name": "awaiting_multiple_events_emitted_on_`process.nexttick()`",
"desc": "There is an edge case worth noting when using the events.once()
function\nto await multiple events emitted on in the same batch of process.nextTick()
\noperations, or whenever multiple events are emitted synchronously. Specifically,\nbecause the process.nextTick()
queue is drained before the Promise
microtask\nqueue, and because EventEmitter
emits all events synchronously, it is possible\nfor events.once()
to miss an event.
import { EventEmitter, once } from 'node:events';\nimport process from 'node:process';\n\nconst myEE = new EventEmitter();\n\nasync function foo() {\n await once(myEE, 'bar');\n console.log('bar');\n\n // This Promise will never resolve because the 'foo' event will\n // have already been emitted before the Promise is created.\n await once(myEE, 'foo');\n console.log('foo');\n}\n\nprocess.nextTick(() => {\n myEE.emit('bar');\n myEE.emit('foo');\n});\n\nfoo().then(() => console.log('done'));\n
\nconst { EventEmitter, once } = require('node:events');\n\nconst myEE = new EventEmitter();\n\nasync function foo() {\n await once(myEE, 'bar');\n console.log('bar');\n\n // This Promise will never resolve because the 'foo' event will\n // have already been emitted before the Promise is created.\n await once(myEE, 'foo');\n console.log('foo');\n}\n\nprocess.nextTick(() => {\n myEE.emit('bar');\n myEE.emit('foo');\n});\n\nfoo().then(() => console.log('done'));\n
\nTo catch both events, create each of the Promises before awaiting either\nof them, then it becomes possible to use Promise.all()
, Promise.race()
,\nor Promise.allSettled()
:
import { EventEmitter, once } from 'node:events';\nimport process from 'node:process';\n\nconst myEE = new EventEmitter();\n\nasync function foo() {\n await Promise.all([once(myEE, 'bar'), once(myEE, 'foo')]);\n console.log('foo', 'bar');\n}\n\nprocess.nextTick(() => {\n myEE.emit('bar');\n myEE.emit('foo');\n});\n\nfoo().then(() => console.log('done'));\n
\nconst { EventEmitter, once } = require('node:events');\n\nconst myEE = new EventEmitter();\n\nasync function foo() {\n await Promise.all([once(myEE, 'bar'), once(myEE, 'foo')]);\n console.log('foo', 'bar');\n}\n\nprocess.nextTick(() => {\n myEE.emit('bar');\n myEE.emit('foo');\n});\n\nfoo().then(() => console.log('done'));\n
",
"type": "module",
"displayName": "Awaiting multiple events emitted on `process.nextTick()`"
}
]
},
{
"textRaw": "`events.listenerCount(emitter, eventName)`",
"type": "method",
"name": "listenerCount",
"meta": {
"added": [
"v0.9.12"
],
"deprecated": [
"v3.2.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`emitter.listenerCount()`][] instead.",
"signatures": [
{
"params": [
{
"textRaw": "`emitter` {EventEmitter} The emitter to query",
"name": "emitter",
"type": "EventEmitter",
"desc": "The emitter to query"
},
{
"textRaw": "`eventName` {string|symbol} The event name",
"name": "eventName",
"type": "string|symbol",
"desc": "The event name"
}
]
}
],
"desc": "A class method that returns the number of listeners for the given eventName
\nregistered on the given emitter
.
import { EventEmitter, listenerCount } from 'node:events';\n\nconst myEmitter = new EventEmitter();\nmyEmitter.on('event', () => {});\nmyEmitter.on('event', () => {});\nconsole.log(listenerCount(myEmitter, 'event'));\n// Prints: 2\n
\nconst { EventEmitter, listenerCount } = require('node:events');\n\nconst myEmitter = new EventEmitter();\nmyEmitter.on('event', () => {});\nmyEmitter.on('event', () => {});\nconsole.log(listenerCount(myEmitter, 'event'));\n// Prints: 2\n
"
},
{
"textRaw": "`events.on(emitter, eventName[, options])`",
"type": "method",
"name": "on",
"meta": {
"added": [
"v13.6.0",
"v12.16.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {AsyncIterator} that iterates `eventName` events emitted by the `emitter`",
"name": "return",
"type": "AsyncIterator",
"desc": "that iterates `eventName` events emitted by the `emitter`"
},
"params": [
{
"textRaw": "`emitter` {EventEmitter}",
"name": "emitter",
"type": "EventEmitter"
},
{
"textRaw": "`eventName` {string|symbol} The name of the event being listened for",
"name": "eventName",
"type": "string|symbol",
"desc": "The name of the event being listened for"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} Can be used to cancel awaiting events.",
"name": "signal",
"type": "AbortSignal",
"desc": "Can be used to cancel awaiting events."
}
]
}
]
}
],
"desc": "import { on, EventEmitter } from 'node:events';\nimport process from 'node:process';\n\nconst ee = new EventEmitter();\n\n// Emit later on\nprocess.nextTick(() => {\n ee.emit('foo', 'bar');\n ee.emit('foo', 42);\n});\n\nfor await (const event of on(ee, 'foo')) {\n // The execution of this inner block is synchronous and it\n // processes one event at a time (even with await). Do not use\n // if concurrent execution is required.\n console.log(event); // prints ['bar'] [42]\n}\n// Unreachable here\n
\nconst { on, EventEmitter } = require('node:events');\n\n(async () => {\n const ee = new EventEmitter();\n\n // Emit later on\n process.nextTick(() => {\n ee.emit('foo', 'bar');\n ee.emit('foo', 42);\n });\n\n for await (const event of on(ee, 'foo')) {\n // The execution of this inner block is synchronous and it\n // processes one event at a time (even with await). Do not use\n // if concurrent execution is required.\n console.log(event); // prints ['bar'] [42]\n }\n // Unreachable here\n})();\n
\nReturns an AsyncIterator
that iterates eventName
events. It will throw\nif the EventEmitter
emits 'error'
. It removes all listeners when\nexiting the loop. The value
returned by each iteration is an array\ncomposed of the emitted event arguments.
An <AbortSignal> can be used to cancel waiting on events:
\nimport { on, EventEmitter } from 'node:events';\nimport process from 'node:process';\n\nconst ac = new AbortController();\n\n(async () => {\n const ee = new EventEmitter();\n\n // Emit later on\n process.nextTick(() => {\n ee.emit('foo', 'bar');\n ee.emit('foo', 42);\n });\n\n for await (const event of on(ee, 'foo', { signal: ac.signal })) {\n // The execution of this inner block is synchronous and it\n // processes one event at a time (even with await). Do not use\n // if concurrent execution is required.\n console.log(event); // prints ['bar'] [42]\n }\n // Unreachable here\n})();\n\nprocess.nextTick(() => ac.abort());\n
\nconst { on, EventEmitter } = require('node:events');\n\nconst ac = new AbortController();\n\n(async () => {\n const ee = new EventEmitter();\n\n // Emit later on\n process.nextTick(() => {\n ee.emit('foo', 'bar');\n ee.emit('foo', 42);\n });\n\n for await (const event of on(ee, 'foo', { signal: ac.signal })) {\n // The execution of this inner block is synchronous and it\n // processes one event at a time (even with await). Do not use\n // if concurrent execution is required.\n console.log(event); // prints ['bar'] [42]\n }\n // Unreachable here\n})();\n\nprocess.nextTick(() => ac.abort());\n
"
},
{
"textRaw": "`events.setMaxListeners(n[, ...eventTargets])`",
"type": "method",
"name": "setMaxListeners",
"meta": {
"added": [
"v15.4.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`n` {number} A non-negative number. The maximum number of listeners per `EventTarget` event.",
"name": "n",
"type": "number",
"desc": "A non-negative number. The maximum number of listeners per `EventTarget` event."
},
{
"textRaw": "`...eventsTargets` {EventTarget\\[]|EventEmitter\\[]} Zero or more {EventTarget} or {EventEmitter} instances. If none are specified, `n` is set as the default max for all newly created {EventTarget} and {EventEmitter} objects.",
"name": "...eventsTargets",
"type": "EventTarget\\[]|EventEmitter\\[]",
"desc": "Zero or more {EventTarget} or {EventEmitter} instances. If none are specified, `n` is set as the default max for all newly created {EventTarget} and {EventEmitter} objects."
}
]
}
],
"desc": "import { setMaxListeners, EventEmitter } from 'node:events';\n\nconst target = new EventTarget();\nconst emitter = new EventEmitter();\n\nsetMaxListeners(5, target, emitter);\n
\nconst {\n setMaxListeners,\n EventEmitter,\n} = require('node:events');\n\nconst target = new EventTarget();\nconst emitter = new EventEmitter();\n\nsetMaxListeners(5, target, emitter);\n
"
},
{
"textRaw": "`events.addAbortListener(signal, listener)`",
"type": "method",
"name": "addAbortListener",
"meta": {
"added": [
"v20.5.0",
"v18.18.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Disposable} A Disposable that removes the `abort` listener.",
"name": "return",
"type": "Disposable",
"desc": "A Disposable that removes the `abort` listener."
},
"params": [
{
"textRaw": "`signal` {AbortSignal}",
"name": "signal",
"type": "AbortSignal"
},
{
"textRaw": "`listener` {Function|EventListener}",
"name": "listener",
"type": "Function|EventListener"
}
]
}
],
"desc": "Listens once to the abort
event on the provided signal
.
Listening to the abort
event on abort signals is unsafe and may\nlead to resource leaks since another third party with the signal can\ncall e.stopImmediatePropagation()
. Unfortunately Node.js cannot change\nthis since it would violate the web standard. Additionally, the original\nAPI makes it easy to forget to remove listeners.
This API allows safely using AbortSignal
s in Node.js APIs by solving these\ntwo issues by listening to the event such that stopImmediatePropagation
does\nnot prevent the listener from running.
Returns a disposable so that it may be unsubscribed from more easily.
\nconst { addAbortListener } = require('node:events');\n\nfunction example(signal) {\n let disposable;\n try {\n signal.addEventListener('abort', (e) => e.stopImmediatePropagation());\n disposable = addAbortListener(signal, (e) => {\n // Do something when signal is aborted.\n });\n } finally {\n disposable?.[Symbol.dispose]();\n }\n}\n
\nimport { addAbortListener } from 'node:events';\n\nfunction example(signal) {\n let disposable;\n try {\n signal.addEventListener('abort', (e) => e.stopImmediatePropagation());\n disposable = addAbortListener(signal, (e) => {\n // Do something when signal is aborted.\n });\n } finally {\n disposable?.[Symbol.dispose]();\n }\n}\n
"
}
],
"source": "doc/api/events.md"
},
{
"textRaw": "File system",
"name": "fs",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/fs.js
\nThe node:fs
module enables interacting with the file system in a\nway modeled on standard POSIX functions.
To use the promise-based APIs:
\nimport * as fs from 'node:fs/promises';\n
\nconst fs = require('node:fs/promises');\n
\nTo use the callback and sync APIs:
\nimport * as fs from 'node:fs';\n
\nconst fs = require('node:fs');\n
\nAll file system operations have synchronous, callback, and promise-based\nforms, and are accessible using both CommonJS syntax and ES6 Modules (ESM).
", "modules": [ { "textRaw": "Promise example", "name": "promise_example", "desc": "Promise-based operations return a promise that is fulfilled when the\nasynchronous operation is complete.
\nimport { unlink } from 'node:fs/promises';\n\ntry {\n await unlink('/tmp/hello');\n console.log('successfully deleted /tmp/hello');\n} catch (error) {\n console.error('there was an error:', error.message);\n}\n
\nconst { unlink } = require('node:fs/promises');\n\n(async function(path) {\n try {\n await unlink(path);\n console.log(`successfully deleted ${path}`);\n } catch (error) {\n console.error('there was an error:', error.message);\n }\n})('/tmp/hello');\n
",
"type": "module",
"displayName": "Promise example"
},
{
"textRaw": "Callback example",
"name": "callback_example",
"desc": "The callback form takes a completion callback function as its last\nargument and invokes the operation asynchronously. The arguments passed to\nthe completion callback depend on the method, but the first argument is always\nreserved for an exception. If the operation is completed successfully, then\nthe first argument is null
or undefined
.
import { unlink } from 'node:fs';\n\nunlink('/tmp/hello', (err) => {\n if (err) throw err;\n console.log('successfully deleted /tmp/hello');\n});\n
\nconst { unlink } = require('node:fs');\n\nunlink('/tmp/hello', (err) => {\n if (err) throw err;\n console.log('successfully deleted /tmp/hello');\n});\n
\nThe callback-based versions of the node:fs
module APIs are preferable over\nthe use of the promise APIs when maximal performance (both in terms of\nexecution time and memory allocation) is required.
The synchronous APIs block the Node.js event loop and further JavaScript\nexecution until the operation is complete. Exceptions are thrown immediately\nand can be handled using try…catch
, or can be allowed to bubble up.
import { unlinkSync } from 'node:fs';\n\ntry {\n unlinkSync('/tmp/hello');\n console.log('successfully deleted /tmp/hello');\n} catch (err) {\n // handle the error\n}\n
\nconst { unlinkSync } = require('node:fs');\n\ntry {\n unlinkSync('/tmp/hello');\n console.log('successfully deleted /tmp/hello');\n} catch (err) {\n // handle the error\n}\n
",
"type": "module",
"displayName": "Synchronous example"
},
{
"textRaw": "Promises API",
"name": "promises_api",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/31553",
"description": "Exposed as `require('fs/promises')`."
},
{
"version": [
"v11.14.0",
"v10.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/26581",
"description": "This API is no longer experimental."
},
{
"version": "v10.1.0",
"pr-url": "https://github.com/nodejs/node/pull/20504",
"description": "The API is accessible via `require('fs').promises` only."
}
]
},
"desc": "The fs/promises
API provides asynchronous file system methods that return\npromises.
The promise APIs use the underlying Node.js threadpool to perform file\nsystem operations off the event loop thread. These operations are not\nsynchronized or threadsafe. Care must be taken when performing multiple\nconcurrent modifications on the same file or data corruption may occur.
", "classes": [ { "textRaw": "Class: `FileHandle`", "type": "class", "name": "FileHandle", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "desc": "A <FileHandle> object is an object wrapper for a numeric file descriptor.
\nInstances of the <FileHandle> object are created by the fsPromises.open()
\nmethod.
All <FileHandle> objects are <EventEmitter>s.
\nIf a <FileHandle> is not closed using the filehandle.close()
method, it will\ntry to automatically close the file descriptor and emit a process warning,\nhelping to prevent memory leaks. Please do not rely on this behavior because\nit can be unreliable and the file may not be closed. Instead, always explicitly\nclose <FileHandle>s. Node.js may change this behavior in the future.
The 'close'
event is emitted when the <FileHandle> has been closed and can no\nlonger be used.
Alias of filehandle.writeFile()
.
When operating on file handles, the mode cannot be changed from what it was set\nto with fsPromises.open()
. Therefore, this is equivalent to\nfilehandle.writeFile()
.
Modifies the permissions on the file. See chmod(2)
.
Changes the ownership of the file. A wrapper for chown(2)
.
Closes the file handle after waiting for any pending operation on the handle to\ncomplete.
\nimport { open } from 'node:fs/promises';\n\nlet filehandle;\ntry {\n filehandle = await open('thefile.txt', 'r');\n} finally {\n await filehandle?.close();\n}\n
"
},
{
"textRaw": "`filehandle.createReadStream([options])`",
"type": "method",
"name": "createReadStream",
"meta": {
"added": [
"v16.11.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {fs.ReadStream}",
"name": "return",
"type": "fs.ReadStream"
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`encoding` {string} **Default:** `null`",
"name": "encoding",
"type": "string",
"default": "`null`"
},
{
"textRaw": "`autoClose` {boolean} **Default:** `true`",
"name": "autoClose",
"type": "boolean",
"default": "`true`"
},
{
"textRaw": "`emitClose` {boolean} **Default:** `true`",
"name": "emitClose",
"type": "boolean",
"default": "`true`"
},
{
"textRaw": "`start` {integer}",
"name": "start",
"type": "integer"
},
{
"textRaw": "`end` {integer} **Default:** `Infinity`",
"name": "end",
"type": "integer",
"default": "`Infinity`"
},
{
"textRaw": "`highWaterMark` {integer} **Default:** `64 * 1024`",
"name": "highWaterMark",
"type": "integer",
"default": "`64 * 1024`"
}
]
}
]
}
],
"desc": "Unlike the 16 KiB default highWaterMark
for a <stream.Readable>, the stream\nreturned by this method has a default highWaterMark
of 64 KiB.
options
can include start
and end
values to read a range of bytes from\nthe file instead of the entire file. Both start
and end
are inclusive and\nstart counting at 0, allowed values are in the\n[0, Number.MAX_SAFE_INTEGER
] range. If start
is\nomitted or undefined
, filehandle.createReadStream()
reads sequentially from\nthe current file position. The encoding
can be any one of those accepted by\n<Buffer>.
If the FileHandle
points to a character device that only supports blocking\nreads (such as keyboard or sound card), read operations do not finish until data\nis available. This can prevent the process from exiting and the stream from\nclosing naturally.
By default, the stream will emit a 'close'
event after it has been\ndestroyed. Set the emitClose
option to false
to change this behavior.
import { open } from 'node:fs/promises';\n\nconst fd = await open('/dev/input/event0');\n// Create a stream from some character device.\nconst stream = fd.createReadStream();\nsetTimeout(() => {\n stream.close(); // This may not close the stream.\n // Artificially marking end-of-stream, as if the underlying resource had\n // indicated end-of-file by itself, allows the stream to close.\n // This does not cancel pending read operations, and if there is such an\n // operation, the process may still not be able to exit successfully\n // until it finishes.\n stream.push(null);\n stream.read(0);\n}, 100);\n
\nIf autoClose
is false, then the file descriptor won't be closed, even if\nthere's an error. It is the application's responsibility to close it and make\nsure there's no file descriptor leak. If autoClose
is set to true (default\nbehavior), on 'error'
or 'end'
the file descriptor will be closed\nautomatically.
An example to read the last 10 bytes of a file which is 100 bytes long:
\nimport { open } from 'node:fs/promises';\n\nconst fd = await open('sample.txt');\nfd.createReadStream({ start: 90, end: 99 });\n
"
},
{
"textRaw": "`filehandle.createWriteStream([options])`",
"type": "method",
"name": "createWriteStream",
"meta": {
"added": [
"v16.11.0"
],
"changes": [
{
"version": "v21.0.0",
"pr-url": "https://github.com/nodejs/node/pull/50093",
"description": "The `flush` option is now supported."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {fs.WriteStream}",
"name": "return",
"type": "fs.WriteStream"
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`encoding` {string} **Default:** `'utf8'`",
"name": "encoding",
"type": "string",
"default": "`'utf8'`"
},
{
"textRaw": "`autoClose` {boolean} **Default:** `true`",
"name": "autoClose",
"type": "boolean",
"default": "`true`"
},
{
"textRaw": "`emitClose` {boolean} **Default:** `true`",
"name": "emitClose",
"type": "boolean",
"default": "`true`"
},
{
"textRaw": "`start` {integer}",
"name": "start",
"type": "integer"
},
{
"textRaw": "`highWaterMark` {number} **Default:** `16384`",
"name": "highWaterMark",
"type": "number",
"default": "`16384`"
},
{
"textRaw": "`flush` {boolean} If `true`, the underlying file descriptor is flushed prior to closing it. **Default:** `false`.",
"name": "flush",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, the underlying file descriptor is flushed prior to closing it."
}
]
}
]
}
],
"desc": "options
may also include a start
option to allow writing data at some\nposition past the beginning of the file, allowed values are in the\n[0, Number.MAX_SAFE_INTEGER
] range. Modifying a file rather than\nreplacing it may require the flags
open
option to be set to r+
rather than\nthe default r
. The encoding
can be any one of those accepted by <Buffer>.
If autoClose
is set to true (default behavior) on 'error'
or 'finish'
\nthe file descriptor will be closed automatically. If autoClose
is false,\nthen the file descriptor won't be closed, even if there's an error.\nIt is the application's responsibility to close it and make sure there's no\nfile descriptor leak.
By default, the stream will emit a 'close'
event after it has been\ndestroyed. Set the emitClose
option to false
to change this behavior.
Forces all currently queued I/O operations associated with the file to the\noperating system's synchronized I/O completion state. Refer to the POSIX\nfdatasync(2)
documentation for details.
Unlike filehandle.sync
this method does not flush modified metadata.
Reads data from the file and stores that in the given buffer.
\nIf the file is not modified concurrently, the end-of-file is reached when the\nnumber of bytes read is zero.
" }, { "textRaw": "`filehandle.read([options])`", "type": "method", "name": "read", "meta": { "added": [ "v13.11.0", "v12.17.0" ], "changes": [ { "version": "v21.0.0", "pr-url": "https://github.com/nodejs/node/pull/42835", "description": "Accepts bigint values as `position`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills upon success with an object with two properties:", "name": "return", "type": "Promise", "desc": "Fulfills upon success with an object with two properties:", "options": [ { "textRaw": "`bytesRead` {integer} The number of bytes read", "name": "bytesRead", "type": "integer", "desc": "The number of bytes read" }, { "textRaw": "`buffer` {Buffer|TypedArray|DataView} A reference to the passed in `buffer` argument.", "name": "buffer", "type": "Buffer|TypedArray|DataView", "desc": "A reference to the passed in `buffer` argument." } ] }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`buffer` {Buffer|TypedArray|DataView} A buffer that will be filled with the file data read. **Default:** `Buffer.alloc(16384)`", "name": "buffer", "type": "Buffer|TypedArray|DataView", "default": "`Buffer.alloc(16384)`", "desc": "A buffer that will be filled with the file data read." }, { "textRaw": "`offset` {integer} The location in the buffer at which to start filling. **Default:** `0`", "name": "offset", "type": "integer", "default": "`0`", "desc": "The location in the buffer at which to start filling." }, { "textRaw": "`length` {integer} The number of bytes to read. **Default:** `buffer.byteLength - offset`", "name": "length", "type": "integer", "default": "`buffer.byteLength - offset`", "desc": "The number of bytes to read." }, { "textRaw": "`position` {integer|bigint|null} The location where to begin reading data from the file. If `null` or `-1`, data will be read from the current file position, and the position will be updated. If `position` is a non-negative integer, the current file position will remain unchanged. **Default:**: `null`", "name": "position", "type": "integer|bigint|null", "default": ": `null`", "desc": "The location where to begin reading data from the file. If `null` or `-1`, data will be read from the current file position, and the position will be updated. If `position` is a non-negative integer, the current file position will remain unchanged." } ] } ] } ], "desc": "Reads data from the file and stores that in the given buffer.
\nIf the file is not modified concurrently, the end-of-file is reached when the\nnumber of bytes read is zero.
" }, { "textRaw": "`filehandle.read(buffer[, options])`", "type": "method", "name": "read", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v21.0.0", "pr-url": "https://github.com/nodejs/node/pull/42835", "description": "Accepts bigint values as `position`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills upon success with an object with two properties:", "name": "return", "type": "Promise", "desc": "Fulfills upon success with an object with two properties:", "options": [ { "textRaw": "`bytesRead` {integer} The number of bytes read", "name": "bytesRead", "type": "integer", "desc": "The number of bytes read" }, { "textRaw": "`buffer` {Buffer|TypedArray|DataView} A reference to the passed in `buffer` argument.", "name": "buffer", "type": "Buffer|TypedArray|DataView", "desc": "A reference to the passed in `buffer` argument." } ] }, "params": [ { "textRaw": "`buffer` {Buffer|TypedArray|DataView} A buffer that will be filled with the file data read.", "name": "buffer", "type": "Buffer|TypedArray|DataView", "desc": "A buffer that will be filled with the file data read." }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`offset` {integer} The location in the buffer at which to start filling. **Default:** `0`", "name": "offset", "type": "integer", "default": "`0`", "desc": "The location in the buffer at which to start filling." }, { "textRaw": "`length` {integer} The number of bytes to read. **Default:** `buffer.byteLength - offset`", "name": "length", "type": "integer", "default": "`buffer.byteLength - offset`", "desc": "The number of bytes to read." }, { "textRaw": "`position` {integer|bigint|null} The location where to begin reading data from the file. If `null` or `-1`, data will be read from the current file position, and the position will be updated. If `position` is a non-negative integer, the current file position will remain unchanged. **Default:**: `null`", "name": "position", "type": "integer|bigint|null", "default": ": `null`", "desc": "The location where to begin reading data from the file. If `null` or `-1`, data will be read from the current file position, and the position will be updated. If `position` is a non-negative integer, the current file position will remain unchanged." } ] } ] } ], "desc": "Reads data from the file and stores that in the given buffer.
\nIf the file is not modified concurrently, the end-of-file is reached when the\nnumber of bytes read is zero.
" }, { "textRaw": "`filehandle.readableWebStream([options])`", "type": "method", "name": "readableWebStream", "meta": { "added": [ "v17.0.0" ], "changes": [ { "version": [ "v20.0.0", "v18.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/46933", "description": "Added option to create a 'bytes' stream." } ] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {ReadableStream}", "name": "return", "type": "ReadableStream" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`type` {string|undefined} Whether to open a normal or a `'bytes'` stream. **Default:** `undefined`", "name": "type", "type": "string|undefined", "default": "`undefined`", "desc": "Whether to open a normal or a `'bytes'` stream." } ] } ] } ], "desc": "Returns a ReadableStream
that may be used to read the files data.
An error will be thrown if this method is called more than once or is called\nafter the FileHandle
is closed or closing.
import {\n open,\n} from 'node:fs/promises';\n\nconst file = await open('./some/file/to/read');\n\nfor await (const chunk of file.readableWebStream())\n console.log(chunk);\n\nawait file.close();\n
\nconst {\n open,\n} = require('node:fs/promises');\n\n(async () => {\n const file = await open('./some/file/to/read');\n\n for await (const chunk of file.readableWebStream())\n console.log(chunk);\n\n await file.close();\n})();\n
\nWhile the ReadableStream
will read the file to completion, it will not\nclose the FileHandle
automatically. User code must still call the\nfileHandle.close()
method.
Asynchronously reads the entire contents of a file.
\nIf options
is a string, then it specifies the encoding
.
The <FileHandle> has to support reading.
\nIf one or more filehandle.read()
calls are made on a file handle and then a\nfilehandle.readFile()
call is made, the data will be read from the current\nposition till the end of the file. It doesn't always read from the beginning\nof the file.
Convenience method to create a readline
interface and stream over the file.\nSee filehandle.createReadStream()
for the options.
import { open } from 'node:fs/promises';\n\nconst file = await open('./some/file/to/read');\n\nfor await (const line of file.readLines()) {\n console.log(line);\n}\n
\nconst { open } = require('node:fs/promises');\n\n(async () => {\n const file = await open('./some/file/to/read');\n\n for await (const line of file.readLines()) {\n console.log(line);\n }\n})();\n
"
},
{
"textRaw": "`filehandle.readv(buffers[, position])`",
"type": "method",
"name": "readv",
"meta": {
"added": [
"v13.13.0",
"v12.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills upon success an object containing two properties:",
"name": "return",
"type": "Promise",
"desc": "Fulfills upon success an object containing two properties:",
"options": [
{
"textRaw": "`bytesRead` {integer} the number of bytes read",
"name": "bytesRead",
"type": "integer",
"desc": "the number of bytes read"
},
{
"textRaw": "`buffers` {Buffer\\[]|TypedArray\\[]|DataView\\[]} property containing a reference to the `buffers` input.",
"name": "buffers",
"type": "Buffer\\[]|TypedArray\\[]|DataView\\[]",
"desc": "property containing a reference to the `buffers` input."
}
]
},
"params": [
{
"textRaw": "`buffers` {Buffer\\[]|TypedArray\\[]|DataView\\[]}",
"name": "buffers",
"type": "Buffer\\[]|TypedArray\\[]|DataView\\[]"
},
{
"textRaw": "`position` {integer|null} The offset from the beginning of the file where the data should be read from. If `position` is not a `number`, the data will be read from the current position. **Default:** `null`",
"name": "position",
"type": "integer|null",
"default": "`null`",
"desc": "The offset from the beginning of the file where the data should be read from. If `position` is not a `number`, the data will be read from the current position."
}
]
}
],
"desc": "Read from a file and write to an array of <ArrayBufferView>s
" }, { "textRaw": "`filehandle.stat([options])`", "type": "method", "name": "stat", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": "v10.5.0", "pr-url": "https://github.com/nodejs/node/pull/20220", "description": "Accepts an additional `options` object to specify whether the numeric values returned should be bigint." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with an {fs.Stats} for the file.", "name": "return", "type": "Promise", "desc": "Fulfills with an {fs.Stats} for the file." }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`bigint` {boolean} Whether the numeric values in the returned {fs.Stats} object should be `bigint`. **Default:** `false`.", "name": "bigint", "type": "boolean", "default": "`false`", "desc": "Whether the numeric values in the returned {fs.Stats} object should be `bigint`." } ] } ] } ] }, { "textRaw": "`filehandle.sync()`", "type": "method", "name": "sync", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with `undefined` upon success.", "name": "return", "type": "Promise", "desc": "Fulfills with `undefined` upon success." }, "params": [] } ], "desc": "Request that all data for the open file descriptor is flushed to the storage\ndevice. The specific implementation is operating system and device specific.\nRefer to the POSIX fsync(2)
documentation for more detail.
Truncates the file.
\nIf the file was larger than len
bytes, only the first len
bytes will be\nretained in the file.
The following example retains only the first four bytes of the file:
\nimport { open } from 'node:fs/promises';\n\nlet filehandle = null;\ntry {\n filehandle = await open('temp.txt', 'r+');\n await filehandle.truncate(4);\n} finally {\n await filehandle?.close();\n}\n
\nIf the file previously was shorter than len
bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'
):
If len
is negative then 0
will be used.
Change the file system timestamps of the object referenced by the <FileHandle>\nthen fulfills the promise with no arguments upon success.
" }, { "textRaw": "`filehandle.write(buffer, offset[, length[, position]])`", "type": "method", "name": "write", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/31030", "description": "The `buffer` parameter won't coerce unsupported input to buffers anymore." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`buffer` {Buffer|TypedArray|DataView}", "name": "buffer", "type": "Buffer|TypedArray|DataView" }, { "textRaw": "`offset` {integer} The start position from within `buffer` where the data to write begins.", "name": "offset", "type": "integer", "desc": "The start position from within `buffer` where the data to write begins." }, { "textRaw": "`length` {integer} The number of bytes from `buffer` to write. **Default:** `buffer.byteLength - offset`", "name": "length", "type": "integer", "default": "`buffer.byteLength - offset`", "desc": "The number of bytes from `buffer` to write." }, { "textRaw": "`position` {integer|null} The offset from the beginning of the file where the data from `buffer` should be written. If `position` is not a `number`, the data will be written at the current position. See the POSIX pwrite(2) documentation for more detail. **Default:** `null`", "name": "position", "type": "integer|null", "default": "`null`", "desc": "The offset from the beginning of the file where the data from `buffer` should be written. If `position` is not a `number`, the data will be written at the current position. See the POSIX pwrite(2) documentation for more detail." } ] } ], "desc": "Write buffer
to the file.
The promise is fulfilled with an object containing two properties:
\nbytesWritten
<integer> the number of bytes writtenbuffer
<Buffer> | <TypedArray> | <DataView> a reference to the\nbuffer
written.It is unsafe to use filehandle.write()
multiple times on the same file\nwithout waiting for the promise to be fulfilled (or rejected). For this\nscenario, use filehandle.createWriteStream()
.
On Linux, positional writes do not work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`filehandle.write(buffer[, options])`", "type": "method", "name": "write", "meta": { "added": [ "v18.3.0", "v16.17.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`buffer` {Buffer|TypedArray|DataView}", "name": "buffer", "type": "Buffer|TypedArray|DataView" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`offset` {integer} **Default:** `0`", "name": "offset", "type": "integer", "default": "`0`" }, { "textRaw": "`length` {integer} **Default:** `buffer.byteLength - offset`", "name": "length", "type": "integer", "default": "`buffer.byteLength - offset`" }, { "textRaw": "`position` {integer} **Default:** `null`", "name": "position", "type": "integer", "default": "`null`" } ] } ] } ], "desc": "Write buffer
to the file.
Similar to the above filehandle.write
function, this version takes an\noptional options
object. If no options
object is specified, it will\ndefault with the above values.
Write string
to the file. If string
is not a string, the promise is\nrejected with an error.
The promise is fulfilled with an object containing two properties:
\nbytesWritten
<integer> the number of bytes writtenbuffer
<string> a reference to the string
written.It is unsafe to use filehandle.write()
multiple times on the same file\nwithout waiting for the promise to be fulfilled (or rejected). For this\nscenario, use filehandle.createWriteStream()
.
On Linux, positional writes do not work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`filehandle.writeFile(data, options)`", "type": "method", "name": "writeFile", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": [ "v15.14.0", "v14.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/37490", "description": "The `data` argument supports `AsyncIterable`, `Iterable`, and `Stream`." }, { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/31030", "description": "The `data` parameter won't coerce unsupported input to strings anymore." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`data` {string|Buffer|TypedArray|DataView|AsyncIterable|Iterable|Stream}", "name": "data", "type": "string|Buffer|TypedArray|DataView|AsyncIterable|Iterable|Stream" }, { "textRaw": "`options` {Object|string}", "name": "options", "type": "Object|string", "options": [ { "textRaw": "`encoding` {string|null} The expected character encoding when `data` is a string. **Default:** `'utf8'`", "name": "encoding", "type": "string|null", "default": "`'utf8'`", "desc": "The expected character encoding when `data` is a string." } ] } ] } ], "desc": "Asynchronously writes data to a file, replacing the file if it already exists.\ndata
can be a string, a buffer, an <AsyncIterable>, or an <Iterable> object.\nThe promise is fulfilled with no arguments upon success.
If options
is a string, then it specifies the encoding
.
The <FileHandle> has to support writing.
\nIt is unsafe to use filehandle.writeFile()
multiple times on the same file\nwithout waiting for the promise to be fulfilled (or rejected).
If one or more filehandle.write()
calls are made on a file handle and then a\nfilehandle.writeFile()
call is made, the data will be written from the\ncurrent position till the end of the file. It doesn't always write from the\nbeginning of the file.
Write an array of <ArrayBufferView>s to the file.
\nThe promise is fulfilled with an object containing a two properties:
\nbytesWritten
<integer> the number of bytes writtenbuffers
<Buffer[]> | <TypedArray[]> | <DataView[]> a reference to the buffers
\ninput.It is unsafe to call writev()
multiple times on the same file without waiting\nfor the promise to be fulfilled (or rejected).
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`filehandle[Symbol.asyncDispose]()`", "type": "method", "name": "[Symbol.asyncDispose]", "meta": { "added": [ "v20.4.0", "v18.18.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "params": [] } ], "desc": "An alias for filehandle.close()
.
Tests a user's permissions for the file or directory specified by path
.\nThe mode
argument is an optional integer that specifies the accessibility\nchecks to be performed. mode
should be either the value fs.constants.F_OK
\nor a mask consisting of the bitwise OR of any of fs.constants.R_OK
,\nfs.constants.W_OK
, and fs.constants.X_OK
(e.g.\nfs.constants.W_OK | fs.constants.R_OK
). Check File access constants for\npossible values of mode
.
If the accessibility check is successful, the promise is fulfilled with no\nvalue. If any of the accessibility checks fail, the promise is rejected\nwith an <Error> object. The following example checks if the file\n/etc/passwd
can be read and written by the current process.
import { access, constants } from 'node:fs/promises';\n\ntry {\n await access('/etc/passwd', constants.R_OK | constants.W_OK);\n console.log('can access');\n} catch {\n console.error('cannot access');\n}\n
\nUsing fsPromises.access()
to check for the accessibility of a file before\ncalling fsPromises.open()
is not recommended. Doing so introduces a race\ncondition, since other processes may change the file's state between the two\ncalls. Instead, user code should open/read/write the file directly and handle\nthe error raised if the file is not accessible.
Asynchronously append data to a file, creating the file if it does not yet\nexist. data
can be a string or a <Buffer>.
If options
is a string, then it specifies the encoding
.
The mode
option only affects the newly created file. See fs.open()
\nfor more details.
The path
may be specified as a <FileHandle> that has been opened\nfor appending (using fsPromises.open()
).
Changes the permissions of a file.
" }, { "textRaw": "`fsPromises.chown(path, uid, gid)`", "type": "method", "name": "chown", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with `undefined` upon success.", "name": "return", "type": "Promise", "desc": "Fulfills with `undefined` upon success." }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`uid` {integer}", "name": "uid", "type": "integer" }, { "textRaw": "`gid` {integer}", "name": "gid", "type": "integer" } ] } ], "desc": "Changes the ownership of a file.
" }, { "textRaw": "`fsPromises.copyFile(src, dest[, mode])`", "type": "method", "name": "copyFile", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": "v14.0.0", "pr-url": "https://github.com/nodejs/node/pull/27044", "description": "Changed `flags` argument to `mode` and imposed stricter type validation." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with `undefined` upon success.", "name": "return", "type": "Promise", "desc": "Fulfills with `undefined` upon success." }, "params": [ { "textRaw": "`src` {string|Buffer|URL} source filename to copy", "name": "src", "type": "string|Buffer|URL", "desc": "source filename to copy" }, { "textRaw": "`dest` {string|Buffer|URL} destination filename of the copy operation", "name": "dest", "type": "string|Buffer|URL", "desc": "destination filename of the copy operation" }, { "textRaw": "`mode` {integer} Optional modifiers that specify the behavior of the copy operation. It is possible to create a mask consisting of the bitwise OR of two or more values (e.g. `fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE`) **Default:** `0`.", "name": "mode", "type": "integer", "default": "`0`", "desc": "Optional modifiers that specify the behavior of the copy operation. It is possible to create a mask consisting of the bitwise OR of two or more values (e.g. `fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE`)", "options": [ { "textRaw": "`fs.constants.COPYFILE_EXCL`: The copy operation will fail if `dest` already exists.", "name": "fs.constants.COPYFILE_EXCL", "desc": "The copy operation will fail if `dest` already exists." }, { "textRaw": "`fs.constants.COPYFILE_FICLONE`: The copy operation will attempt to create a copy-on-write reflink. If the platform does not support copy-on-write, then a fallback copy mechanism is used.", "name": "fs.constants.COPYFILE_FICLONE", "desc": "The copy operation will attempt to create a copy-on-write reflink. If the platform does not support copy-on-write, then a fallback copy mechanism is used." }, { "textRaw": "`fs.constants.COPYFILE_FICLONE_FORCE`: The copy operation will attempt to create a copy-on-write reflink. If the platform does not support copy-on-write, then the operation will fail.", "name": "fs.constants.COPYFILE_FICLONE_FORCE", "desc": "The copy operation will attempt to create a copy-on-write reflink. If the platform does not support copy-on-write, then the operation will fail." } ] } ] } ], "desc": "Asynchronously copies src
to dest
. By default, dest
is overwritten if it\nalready exists.
No guarantees are made about the atomicity of the copy operation. If an\nerror occurs after the destination file has been opened for writing, an attempt\nwill be made to remove the destination.
\nimport { copyFile, constants } from 'node:fs/promises';\n\ntry {\n await copyFile('source.txt', 'destination.txt');\n console.log('source.txt was copied to destination.txt');\n} catch {\n console.error('The file could not be copied');\n}\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\ntry {\n await copyFile('source.txt', 'destination.txt', constants.COPYFILE_EXCL);\n console.log('source.txt was copied to destination.txt');\n} catch {\n console.error('The file could not be copied');\n}\n
"
},
{
"textRaw": "`fsPromises.cp(src, dest[, options])`",
"type": "method",
"name": "cp",
"meta": {
"added": [
"v16.7.0"
],
"changes": [
{
"version": [
"v20.1.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47084",
"description": "Accept an additional `mode` option to specify the copy behavior as the `mode` argument of `fs.copyFile()`."
},
{
"version": [
"v17.6.0",
"v16.15.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41819",
"description": "Accepts an additional `verbatimSymlinks` option to specify whether to perform path resolution for symlinks."
}
]
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with `undefined` upon success.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with `undefined` upon success."
},
"params": [
{
"textRaw": "`src` {string|URL} source path to copy.",
"name": "src",
"type": "string|URL",
"desc": "source path to copy."
},
{
"textRaw": "`dest` {string|URL} destination path to copy to.",
"name": "dest",
"type": "string|URL",
"desc": "destination path to copy to."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`dereference` {boolean} dereference symlinks. **Default:** `false`.",
"name": "dereference",
"type": "boolean",
"default": "`false`",
"desc": "dereference symlinks."
},
{
"textRaw": "`errorOnExist` {boolean} when `force` is `false`, and the destination exists, throw an error. **Default:** `false`.",
"name": "errorOnExist",
"type": "boolean",
"default": "`false`",
"desc": "when `force` is `false`, and the destination exists, throw an error."
},
{
"textRaw": "`filter` {Function} Function to filter copied files/directories. Return `true` to copy the item, `false` to ignore it. When ignoring a directory, all of its contents will be skipped as well. Can also return a `Promise` that resolves to `true` or `false` **Default:** `undefined`.",
"name": "filter",
"type": "Function",
"default": "`undefined`",
"desc": "Function to filter copied files/directories. Return `true` to copy the item, `false` to ignore it. When ignoring a directory, all of its contents will be skipped as well. Can also return a `Promise` that resolves to `true` or `false`",
"options": [
{
"textRaw": "`src` {string} source path to copy.",
"name": "src",
"type": "string",
"desc": "source path to copy."
},
{
"textRaw": "`dest` {string} destination path to copy to.",
"name": "dest",
"type": "string",
"desc": "destination path to copy to."
},
{
"textRaw": "Returns: {boolean|Promise}",
"name": "return",
"type": "boolean|Promise"
}
]
},
{
"textRaw": "`force` {boolean} overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the `errorOnExist` option to change this behavior. **Default:** `true`.",
"name": "force",
"type": "boolean",
"default": "`true`",
"desc": "overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the `errorOnExist` option to change this behavior."
},
{
"textRaw": "`mode` {integer} modifiers for copy operation. **Default:** `0`. See `mode` flag of [`fsPromises.copyFile()`][].",
"name": "mode",
"type": "integer",
"default": "`0`. See `mode` flag of [`fsPromises.copyFile()`][]",
"desc": "modifiers for copy operation."
},
{
"textRaw": "`preserveTimestamps` {boolean} When `true` timestamps from `src` will be preserved. **Default:** `false`.",
"name": "preserveTimestamps",
"type": "boolean",
"default": "`false`",
"desc": "When `true` timestamps from `src` will be preserved."
},
{
"textRaw": "`recursive` {boolean} copy directories recursively **Default:** `false`",
"name": "recursive",
"type": "boolean",
"default": "`false`",
"desc": "copy directories recursively"
},
{
"textRaw": "`verbatimSymlinks` {boolean} When `true`, path resolution for symlinks will be skipped. **Default:** `false`",
"name": "verbatimSymlinks",
"type": "boolean",
"default": "`false`",
"desc": "When `true`, path resolution for symlinks will be skipped."
}
]
}
]
}
],
"desc": "Asynchronously copies the entire directory structure from src
to dest
,\nincluding subdirectories and files.
When copying a directory to another directory, globs are not supported and\nbehavior is similar to cp dir1/ dir2/
.
Changes the permissions on a symbolic link.
\nThis method is only implemented on macOS.
" }, { "textRaw": "`fsPromises.lchown(path, uid, gid)`", "type": "method", "name": "lchown", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": "v10.6.0", "pr-url": "https://github.com/nodejs/node/pull/21498", "description": "This API is no longer deprecated." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with `undefined` upon success.", "name": "return", "type": "Promise", "desc": "Fulfills with `undefined` upon success." }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`uid` {integer}", "name": "uid", "type": "integer" }, { "textRaw": "`gid` {integer}", "name": "gid", "type": "integer" } ] } ], "desc": "Changes the ownership on a symbolic link.
" }, { "textRaw": "`fsPromises.lutimes(path, atime, mtime)`", "type": "method", "name": "lutimes", "meta": { "added": [ "v14.5.0", "v12.19.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with `undefined` upon success.", "name": "return", "type": "Promise", "desc": "Fulfills with `undefined` upon success." }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`atime` {number|string|Date}", "name": "atime", "type": "number|string|Date" }, { "textRaw": "`mtime` {number|string|Date}", "name": "mtime", "type": "number|string|Date" } ] } ], "desc": "Changes the access and modification times of a file in the same way as\nfsPromises.utimes()
, with the difference that if the path refers to a\nsymbolic link, then the link is not dereferenced: instead, the timestamps of\nthe symbolic link itself are changed.
Creates a new link from the existingPath
to the newPath
. See the POSIX\nlink(2)
documentation for more detail.
Equivalent to fsPromises.stat()
unless path
refers to a symbolic link,\nin which case the link itself is stat-ed, not the file that it refers to.\nRefer to the POSIX lstat(2)
document for more detail.
Asynchronously creates a directory.
\nThe optional options
argument can be an integer specifying mode
(permission\nand sticky bits), or an object with a mode
property and a recursive
\nproperty indicating whether parent directories should be created. Calling\nfsPromises.mkdir()
when path
is a directory that exists results in a\nrejection only when recursive
is false.
import { mkdir } from 'node:fs/promises';\n\ntry {\n const projectFolder = new URL('./test/project/', import.meta.url);\n const createDir = await mkdir(projectFolder, { recursive: true });\n\n console.log(`created ${createDir}`);\n} catch (err) {\n console.error(err.message);\n}\n
\nconst { mkdir } = require('node:fs/promises');\nconst { join } = require('node:path');\n\nasync function makeDirectory() {\n const projectFolder = join(__dirname, 'test', 'project');\n const dirCreation = await mkdir(projectFolder, { recursive: true });\n\n console.log(dirCreation);\n return dirCreation;\n}\n\nmakeDirectory().catch(console.error);\n
"
},
{
"textRaw": "`fsPromises.mkdtemp(prefix[, options])`",
"type": "method",
"name": "mkdtemp",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": "v20.6.0",
"pr-url": "https://github.com/nodejs/node/pull/48828",
"description": "The `prefix` parameter now accepts buffers and URL."
},
{
"version": [
"v16.5.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/39028",
"description": "The `prefix` parameter now accepts an empty string."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with a string containing the file system path of the newly created temporary directory.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with a string containing the file system path of the newly created temporary directory."
},
"params": [
{
"textRaw": "`prefix` {string|Buffer|URL}",
"name": "prefix",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {string|Object}",
"name": "options",
"type": "string|Object",
"options": [
{
"textRaw": "`encoding` {string} **Default:** `'utf8'`",
"name": "encoding",
"type": "string",
"default": "`'utf8'`"
}
]
}
]
}
],
"desc": "Creates a unique temporary directory. A unique directory name is generated by\nappending six random characters to the end of the provided prefix
. Due to\nplatform inconsistencies, avoid trailing X
characters in prefix
. Some\nplatforms, notably the BSDs, can return more than six random characters, and\nreplace trailing X
characters in prefix
with random characters.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use.
import { mkdtemp } from 'node:fs/promises';\nimport { join } from 'node:path';\nimport { tmpdir } from 'node:os';\n\ntry {\n await mkdtemp(join(tmpdir(), 'foo-'));\n} catch (err) {\n console.error(err);\n}\n
\nThe fsPromises.mkdtemp()
method will append the six randomly selected\ncharacters directly to the prefix
string. For instance, given a directory\n/tmp
, if the intention is to create a temporary directory within /tmp
, the\nprefix
must end with a trailing platform-specific path separator\n(require('node:path').sep
).
Opens a <FileHandle>.
\nRefer to the POSIX open(2)
documentation for more detail.
Some characters (< > : \" / \\ | ? *
) are reserved under Windows as documented\nby Naming Files, Paths, and Namespaces. Under NTFS, if the filename contains\na colon, Node.js will open a file system stream, as described by\nthis MSDN page.
Asynchronously open a directory for iterative scanning. See the POSIX\nopendir(3)
documentation for more detail.
Creates an <fs.Dir>, which contains all further functions for reading from\nand cleaning up the directory.
\nThe encoding
option sets the encoding for the path
while opening the\ndirectory and subsequent read operations.
Example using async iteration:
\nimport { opendir } from 'node:fs/promises';\n\ntry {\n const dir = await opendir('./');\n for await (const dirent of dir)\n console.log(dirent.name);\n} catch (err) {\n console.error(err);\n}\n
\nWhen using the async iterator, the <fs.Dir> object will be automatically\nclosed after the iterator exits.
" }, { "textRaw": "`fsPromises.readdir(path[, options])`", "type": "method", "name": "readdir", "meta": { "added": [ "v10.0.0" ], "changes": [ { "version": [ "v20.1.0", "v18.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/41439", "description": "Added `recursive` option." }, { "version": "v10.11.0", "pr-url": "https://github.com/nodejs/node/pull/22020", "description": "New option `withFileTypes` was added." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with an array of the names of the files in the directory excluding `'.'` and `'..'`.", "name": "return", "type": "Promise", "desc": "Fulfills with an array of the names of the files in the directory excluding `'.'` and `'..'`." }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`options` {string|Object}", "name": "options", "type": "string|Object", "options": [ { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`" }, { "textRaw": "`withFileTypes` {boolean} **Default:** `false`", "name": "withFileTypes", "type": "boolean", "default": "`false`" }, { "textRaw": "`recursive` {boolean} If `true`, reads the contents of a directory recursively. In recursive mode, it will list all files, sub files, and directories. **Default:** `false`.", "name": "recursive", "type": "boolean", "default": "`false`", "desc": "If `true`, reads the contents of a directory recursively. In recursive mode, it will list all files, sub files, and directories." } ] } ] } ], "desc": "Reads the contents of a directory.
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe filenames. If the encoding
is set to 'buffer'
, the filenames returned\nwill be passed as <Buffer> objects.
If options.withFileTypes
is set to true
, the returned array will contain\n<fs.Dirent> objects.
import { readdir } from 'node:fs/promises';\n\ntry {\n const files = await readdir(path);\n for (const file of files)\n console.log(file);\n} catch (err) {\n console.error(err);\n}\n
"
},
{
"textRaw": "`fsPromises.readFile(path[, options])`",
"type": "method",
"name": "readFile",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": [
"v15.2.0",
"v14.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/35911",
"description": "The options argument may include an AbortSignal to abort an ongoing readFile request."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with the contents of the file.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with the contents of the file."
},
"params": [
{
"textRaw": "`path` {string|Buffer|URL|FileHandle} filename or `FileHandle`",
"name": "path",
"type": "string|Buffer|URL|FileHandle",
"desc": "filename or `FileHandle`"
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`encoding` {string|null} **Default:** `null`",
"name": "encoding",
"type": "string|null",
"default": "`null`"
},
{
"textRaw": "`flag` {string} See [support of file system `flags`][]. **Default:** `'r'`.",
"name": "flag",
"type": "string",
"default": "`'r'`",
"desc": "See [support of file system `flags`][]."
},
{
"textRaw": "`signal` {AbortSignal} allows aborting an in-progress readFile",
"name": "signal",
"type": "AbortSignal",
"desc": "allows aborting an in-progress readFile"
}
]
}
]
}
],
"desc": "Asynchronously reads the entire contents of a file.
\nIf no encoding is specified (using options.encoding
), the data is returned\nas a <Buffer> object. Otherwise, the data will be a string.
If options
is a string, then it specifies the encoding.
When the path
is a directory, the behavior of fsPromises.readFile()
is\nplatform-specific. On macOS, Linux, and Windows, the promise will be rejected\nwith an error. On FreeBSD, a representation of the directory's contents will be\nreturned.
An example of reading a package.json
file located in the same directory of the\nrunning code:
import { readFile } from 'node:fs/promises';\ntry {\n const filePath = new URL('./package.json', import.meta.url);\n const contents = await readFile(filePath, { encoding: 'utf8' });\n console.log(contents);\n} catch (err) {\n console.error(err.message);\n}\n
\nconst { readFile } = require('node:fs/promises');\nconst { resolve } = require('node:path');\nasync function logFile() {\n try {\n const filePath = resolve('./package.json');\n const contents = await readFile(filePath, { encoding: 'utf8' });\n console.log(contents);\n } catch (err) {\n console.error(err.message);\n }\n}\nlogFile();\n
\nIt is possible to abort an ongoing readFile
using an <AbortSignal>. If a\nrequest is aborted the promise returned is rejected with an AbortError
:
import { readFile } from 'node:fs/promises';\n\ntry {\n const controller = new AbortController();\n const { signal } = controller;\n const promise = readFile(fileName, { signal });\n\n // Abort the request before the promise settles.\n controller.abort();\n\n await promise;\n} catch (err) {\n // When a request is aborted - err is an AbortError\n console.error(err);\n}\n
\nAborting an ongoing request does not abort individual operating\nsystem requests but rather the internal buffering fs.readFile
performs.
Any specified <FileHandle> has to support reading.
" }, { "textRaw": "`fsPromises.readlink(path[, options])`", "type": "method", "name": "readlink", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with the `linkString` upon success.", "name": "return", "type": "Promise", "desc": "Fulfills with the `linkString` upon success." }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`options` {string|Object}", "name": "options", "type": "string|Object", "options": [ { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`" } ] } ] } ], "desc": "Reads the contents of the symbolic link referred to by path
. See the POSIX\nreadlink(2)
documentation for more detail. The promise is fulfilled with the\nlinkString
upon success.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe link path returned. If the encoding
is set to 'buffer'
, the link path\nreturned will be passed as a <Buffer> object.
Determines the actual location of path
using the same semantics as the\nfs.realpath.native()
function.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe path. If the encoding
is set to 'buffer'
, the path returned will be\npassed as a <Buffer> object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc
in order for this function to work. Glibc does not have\nthis restriction.
Renames oldPath
to newPath
.
Removes the directory identified by path
.
Using fsPromises.rmdir()
on a file (not a directory) results in the\npromise being rejected with an ENOENT
error on Windows and an ENOTDIR
\nerror on POSIX.
To get a behavior similar to the rm -rf
Unix command, use\nfsPromises.rm()
with options { recursive: true, force: true }
.
Removes files and directories (modeled on the standard POSIX rm
utility).
Creates a symbolic link.
\nThe type
argument is only used on Windows platforms and can be one of 'dir'
,\n'file'
, or 'junction'
. If the type
argument is not a string, Node.js will\nautodetect target
type and use 'file'
or 'dir'
. If the target
does not\nexist, 'file'
will be used. Windows junction points require the destination\npath to be absolute. When using 'junction'
, the target
argument will\nautomatically be normalized to absolute path. Junction points on NTFS volumes\ncan only point to directories.
Truncates (shortens or extends the length) of the content at path
to len
\nbytes.
If path
refers to a symbolic link, then the link is removed without affecting\nthe file or directory to which that link refers. If the path
refers to a file\npath that is not a symbolic link, the file is deleted. See the POSIX unlink(2)
\ndocumentation for more detail.
Change the file system timestamps of the object referenced by path
.
The atime
and mtime
arguments follow these rules:
Date
s, or a\nnumeric string like '123456789.0'
.NaN
, Infinity
, or\n-Infinity
, an Error
will be thrown.Returns an async iterator that watches for changes on filename
, where filename
\nis either a file or a directory.
const { watch } = require('node:fs/promises');\n\nconst ac = new AbortController();\nconst { signal } = ac;\nsetTimeout(() => ac.abort(), 10000);\n\n(async () => {\n try {\n const watcher = watch(__filename, { signal });\n for await (const event of watcher)\n console.log(event);\n } catch (err) {\n if (err.name === 'AbortError')\n return;\n throw err;\n }\n})();\n
\nOn most platforms, 'rename'
is emitted whenever a filename appears or\ndisappears in the directory.
All the caveats for fs.watch()
also apply to fsPromises.watch()
.
Asynchronously writes data to a file, replacing the file if it already exists.\ndata
can be a string, a buffer, an <AsyncIterable>, or an <Iterable> object.
The encoding
option is ignored if data
is a buffer.
If options
is a string, then it specifies the encoding.
The mode
option only affects the newly created file. See fs.open()
\nfor more details.
Any specified <FileHandle> has to support writing.
\nIt is unsafe to use fsPromises.writeFile()
multiple times on the same file\nwithout waiting for the promise to be settled.
Similarly to fsPromises.readFile
- fsPromises.writeFile
is a convenience\nmethod that performs multiple write
calls internally to write the buffer\npassed to it. For performance sensitive code consider using\nfs.createWriteStream()
or filehandle.createWriteStream()
.
It is possible to use an <AbortSignal> to cancel an fsPromises.writeFile()
.\nCancelation is \"best effort\", and some amount of data is likely still\nto be written.
import { writeFile } from 'node:fs/promises';\nimport { Buffer } from 'node:buffer';\n\ntry {\n const controller = new AbortController();\n const { signal } = controller;\n const data = new Uint8Array(Buffer.from('Hello Node.js'));\n const promise = writeFile('message.txt', data, { signal });\n\n // Abort the request before the promise settles.\n controller.abort();\n\n await promise;\n} catch (err) {\n // When a request is aborted - err is an AbortError\n console.error(err);\n}\n
\nAborting an ongoing request does not abort individual operating\nsystem requests but rather the internal buffering fs.writeFile
performs.
Returns an object containing commonly used constants for file system\noperations. The object is the same as fs.constants
. See FS constants\nfor more details.
The callback APIs perform all operations asynchronously, without blocking the\nevent loop, then invoke a callback function upon completion or error.
\nThe callback APIs use the underlying Node.js threadpool to perform file\nsystem operations off the event loop thread. These operations are not\nsynchronized or threadsafe. Care must be taken when performing multiple\nconcurrent modifications on the same file or data corruption may occur.
", "methods": [ { "textRaw": "`fs.access(path[, mode], callback)`", "type": "method", "name": "access", "meta": { "added": [ "v0.11.15" ], "changes": [ { "version": "v20.8.0", "pr-url": "https://github.com/nodejs/node/pull/49683", "description": "The constants `fs.F_OK`, `fs.R_OK`, `fs.W_OK` and `fs.X_OK` which were present directly on `fs` are deprecated." }, { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol." }, { "version": "v6.3.0", "pr-url": "https://github.com/nodejs/node/pull/6534", "description": "The constants like `fs.R_OK`, etc which were present directly on `fs` were moved into `fs.constants` as a soft deprecation. Thus for Node.js `< v6.3.0` use `fs` to access those constants, or do something like `(fs.constants || fs).R_OK` to work with all versions." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer} **Default:** `fs.constants.F_OK`", "name": "mode", "type": "integer", "default": "`fs.constants.F_OK`" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Tests a user's permissions for the file or directory specified by path
.\nThe mode
argument is an optional integer that specifies the accessibility\nchecks to be performed. mode
should be either the value fs.constants.F_OK
\nor a mask consisting of the bitwise OR of any of fs.constants.R_OK
,\nfs.constants.W_OK
, and fs.constants.X_OK
(e.g.\nfs.constants.W_OK | fs.constants.R_OK
). Check File access constants for\npossible values of mode
.
The final argument, callback
, is a callback function that is invoked with\na possible error argument. If any of the accessibility checks fail, the error\nargument will be an Error
object. The following examples check if\npackage.json
exists, and if it is readable or writable.
import { access, constants } from 'node:fs';\n\nconst file = 'package.json';\n\n// Check if the file exists in the current directory.\naccess(file, constants.F_OK, (err) => {\n console.log(`${file} ${err ? 'does not exist' : 'exists'}`);\n});\n\n// Check if the file is readable.\naccess(file, constants.R_OK, (err) => {\n console.log(`${file} ${err ? 'is not readable' : 'is readable'}`);\n});\n\n// Check if the file is writable.\naccess(file, constants.W_OK, (err) => {\n console.log(`${file} ${err ? 'is not writable' : 'is writable'}`);\n});\n\n// Check if the file is readable and writable.\naccess(file, constants.R_OK | constants.W_OK, (err) => {\n console.log(`${file} ${err ? 'is not' : 'is'} readable and writable`);\n});\n
\nDo not use fs.access()
to check for the accessibility of a file before calling\nfs.open()
, fs.readFile()
, or fs.writeFile()
. Doing\nso introduces a race condition, since other processes may change the file's\nstate between the two calls. Instead, user code should open/read/write the\nfile directly and handle the error raised if the file is not accessible.
write (NOT RECOMMENDED)
\nimport { access, open, close } from 'node:fs';\n\naccess('myfile', (err) => {\n if (!err) {\n console.error('myfile already exists');\n return;\n }\n\n open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n\n try {\n writeMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n });\n});\n
\nwrite (RECOMMENDED)
\nimport { open, close } from 'node:fs';\n\nopen('myfile', 'wx', (err, fd) => {\n if (err) {\n if (err.code === 'EEXIST') {\n console.error('myfile already exists');\n return;\n }\n\n throw err;\n }\n\n try {\n writeMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n});\n
\nread (NOT RECOMMENDED)
\nimport { access, open, close } from 'node:fs';\naccess('myfile', (err) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n\n try {\n readMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n });\n});\n
\nread (RECOMMENDED)
\nimport { open, close } from 'node:fs';\n\nopen('myfile', 'r', (err, fd) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n try {\n readMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n});\n
\nThe \"not recommended\" examples above check for accessibility and then use the\nfile; the \"recommended\" examples are better because they use the file directly\nand handle the error, if any.
\nIn general, check for the accessibility of a file only if the file will not be\nused directly, for example when its accessibility is a signal from another\nprocess.
\nOn Windows, access-control policies (ACLs) on a directory may limit access to\na file or directory. The fs.access()
function, however, does not check the\nACL and therefore may report that a path is accessible even if the ACL restricts\nthe user from reading or writing to it.
Asynchronously append data to a file, creating the file if it does not yet\nexist. data
can be a string or a <Buffer>.
The mode
option only affects the newly created file. See fs.open()
\nfor more details.
import { appendFile } from 'node:fs';\n\nappendFile('message.txt', 'data to append', (err) => {\n if (err) throw err;\n console.log('The \"data to append\" was appended to file!');\n});\n
\nIf options
is a string, then it specifies the encoding:
import { appendFile } from 'node:fs';\n\nappendFile('message.txt', 'data to append', 'utf8', callback);\n
\nThe path
may be specified as a numeric file descriptor that has been opened\nfor appending (using fs.open()
or fs.openSync()
). The file descriptor will\nnot be closed automatically.
import { open, close, appendFile } from 'node:fs';\n\nfunction closeFd(fd) {\n close(fd, (err) => {\n if (err) throw err;\n });\n}\n\nopen('message.txt', 'a', (err, fd) => {\n if (err) throw err;\n\n try {\n appendFile(fd, 'data to append', 'utf8', (err) => {\n closeFd(fd);\n if (err) throw err;\n });\n } catch (err) {\n closeFd(fd);\n throw err;\n }\n});\n
"
},
{
"textRaw": "`fs.chmod(path, mode, callback)`",
"type": "method",
"name": "chmod",
"meta": {
"added": [
"v0.1.30"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
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"description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime."
},
{
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"description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol."
},
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"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/7897",
"description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`mode` {string|integer}",
"name": "mode",
"type": "string|integer"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
}
]
}
]
}
],
"desc": "Asynchronously changes the permissions of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee the POSIX chmod(2)
documentation for more detail.
import { chmod } from 'node:fs';\n\nchmod('my_file.txt', 0o775, (err) => {\n if (err) throw err;\n console.log('The permissions for file \"my_file.txt\" have been changed!');\n});\n
",
"modules": [
{
"textRaw": "File modes",
"name": "file_modes",
"desc": "The mode
argument used in both the fs.chmod()
and fs.chmodSync()
\nmethods is a numeric bitmask created using a logical OR of the following\nconstants:
Constant | \nOctal | \nDescription | \n
---|---|---|
fs.constants.S_IRUSR | \n0o400 | \nread by owner | \n
fs.constants.S_IWUSR | \n0o200 | \nwrite by owner | \n
fs.constants.S_IXUSR | \n0o100 | \nexecute/search by owner | \n
fs.constants.S_IRGRP | \n0o40 | \nread by group | \n
fs.constants.S_IWGRP | \n0o20 | \nwrite by group | \n
fs.constants.S_IXGRP | \n0o10 | \nexecute/search by group | \n
fs.constants.S_IROTH | \n0o4 | \nread by others | \n
fs.constants.S_IWOTH | \n0o2 | \nwrite by others | \n
fs.constants.S_IXOTH | \n0o1 | \nexecute/search by others | \n
An easier method of constructing the mode
is to use a sequence of three\noctal digits (e.g. 765
). The left-most digit (7
in the example), specifies\nthe permissions for the file owner. The middle digit (6
in the example),\nspecifies permissions for the group. The right-most digit (5
in the example),\nspecifies the permissions for others.
Number | \nDescription | \n
---|---|
7 | \nread, write, and execute | \n
6 | \nread and write | \n
5 | \nread and execute | \n
4 | \nread only | \n
3 | \nwrite and execute | \n
2 | \nwrite only | \n
1 | \nexecute only | \n
0 | \nno permission | \n
For example, the octal value 0o765
means:
When using raw numbers where file modes are expected, any value larger than\n0o777
may result in platform-specific behaviors that are not supported to work\nconsistently. Therefore constants like S_ISVTX
, S_ISGID
, or S_ISUID
are\nnot exposed in fs.constants
.
Caveats: on Windows only the write permission can be changed, and the\ndistinction among the permissions of group, owner, or others is not\nimplemented.
", "type": "module", "displayName": "File modes" } ] }, { "textRaw": "`fs.chown(path, uid, gid, callback)`", "type": "method", "name": "chown", "meta": { "added": [ "v0.1.97" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`uid` {integer}", "name": "uid", "type": "integer" }, { "textRaw": "`gid` {integer}", "name": "gid", "type": "integer" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Asynchronously changes owner and group of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee the POSIX chown(2)
documentation for more detail.
Closes the file descriptor. No arguments other than a possible exception are\ngiven to the completion callback.
\nCalling fs.close()
on any file descriptor (fd
) that is currently in use\nthrough any other fs
operation may lead to undefined behavior.
See the POSIX close(2)
documentation for more detail.
Asynchronously copies src
to dest
. By default, dest
is overwritten if it\nalready exists. No arguments other than a possible exception are given to the\ncallback function. Node.js makes no guarantees about the atomicity of the copy\noperation. If an error occurs after the destination file has been opened for\nwriting, Node.js will attempt to remove the destination.
mode
is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE
).
fs.constants.COPYFILE_EXCL
: The copy operation will fail if dest
already\nexists.fs.constants.COPYFILE_FICLONE
: The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE
: The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support\ncopy-on-write, then the operation will fail.import { copyFile, constants } from 'node:fs';\n\nfunction callback(err) {\n if (err) throw err;\n console.log('source.txt was copied to destination.txt');\n}\n\n// destination.txt will be created or overwritten by default.\ncopyFile('source.txt', 'destination.txt', callback);\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\ncopyFile('source.txt', 'destination.txt', constants.COPYFILE_EXCL, callback);\n
"
},
{
"textRaw": "`fs.cp(src, dest[, options], callback)`",
"type": "method",
"name": "cp",
"meta": {
"added": [
"v16.7.0"
],
"changes": [
{
"version": [
"v20.1.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47084",
"description": "Accept an additional `mode` option to specify the copy behavior as the `mode` argument of `fs.copyFile()`."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": [
"v17.6.0",
"v16.15.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41819",
"description": "Accepts an additional `verbatimSymlinks` option to specify whether to perform path resolution for symlinks."
}
]
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": [
{
"textRaw": "`src` {string|URL} source path to copy.",
"name": "src",
"type": "string|URL",
"desc": "source path to copy."
},
{
"textRaw": "`dest` {string|URL} destination path to copy to.",
"name": "dest",
"type": "string|URL",
"desc": "destination path to copy to."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`dereference` {boolean} dereference symlinks. **Default:** `false`.",
"name": "dereference",
"type": "boolean",
"default": "`false`",
"desc": "dereference symlinks."
},
{
"textRaw": "`errorOnExist` {boolean} when `force` is `false`, and the destination exists, throw an error. **Default:** `false`.",
"name": "errorOnExist",
"type": "boolean",
"default": "`false`",
"desc": "when `force` is `false`, and the destination exists, throw an error."
},
{
"textRaw": "`filter` {Function} Function to filter copied files/directories. Return `true` to copy the item, `false` to ignore it. When ignoring a directory, all of its contents will be skipped as well. Can also return a `Promise` that resolves to `true` or `false` **Default:** `undefined`.",
"name": "filter",
"type": "Function",
"default": "`undefined`",
"desc": "Function to filter copied files/directories. Return `true` to copy the item, `false` to ignore it. When ignoring a directory, all of its contents will be skipped as well. Can also return a `Promise` that resolves to `true` or `false`",
"options": [
{
"textRaw": "`src` {string} source path to copy.",
"name": "src",
"type": "string",
"desc": "source path to copy."
},
{
"textRaw": "`dest` {string} destination path to copy to.",
"name": "dest",
"type": "string",
"desc": "destination path to copy to."
},
{
"textRaw": "Returns: {boolean|Promise}",
"name": "return",
"type": "boolean|Promise"
}
]
},
{
"textRaw": "`force` {boolean} overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the `errorOnExist` option to change this behavior. **Default:** `true`.",
"name": "force",
"type": "boolean",
"default": "`true`",
"desc": "overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the `errorOnExist` option to change this behavior."
},
{
"textRaw": "`mode` {integer} modifiers for copy operation. **Default:** `0`. See `mode` flag of [`fs.copyFile()`][].",
"name": "mode",
"type": "integer",
"default": "`0`. See `mode` flag of [`fs.copyFile()`][]",
"desc": "modifiers for copy operation."
},
{
"textRaw": "`preserveTimestamps` {boolean} When `true` timestamps from `src` will be preserved. **Default:** `false`.",
"name": "preserveTimestamps",
"type": "boolean",
"default": "`false`",
"desc": "When `true` timestamps from `src` will be preserved."
},
{
"textRaw": "`recursive` {boolean} copy directories recursively **Default:** `false`",
"name": "recursive",
"type": "boolean",
"default": "`false`",
"desc": "copy directories recursively"
},
{
"textRaw": "`verbatimSymlinks` {boolean} When `true`, path resolution for symlinks will be skipped. **Default:** `false`",
"name": "verbatimSymlinks",
"type": "boolean",
"default": "`false`",
"desc": "When `true`, path resolution for symlinks will be skipped."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Asynchronously copies the entire directory structure from src
to dest
,\nincluding subdirectories and files.
When copying a directory to another directory, globs are not supported and\nbehavior is similar to cp dir1/ dir2/
.
Unlike the 16 KiB default highWaterMark
for a <stream.Readable>, the stream\nreturned by this method has a default highWaterMark
of 64 KiB.
options
can include start
and end
values to read a range of bytes from\nthe file instead of the entire file. Both start
and end
are inclusive and\nstart counting at 0, allowed values are in the\n[0, Number.MAX_SAFE_INTEGER
] range. If fd
is specified and start
is\nomitted or undefined
, fs.createReadStream()
reads sequentially from the\ncurrent file position. The encoding
can be any one of those accepted by\n<Buffer>.
If fd
is specified, ReadStream
will ignore the path
argument and will use\nthe specified file descriptor. This means that no 'open'
event will be\nemitted. fd
should be blocking; non-blocking fd
s should be passed to\n<net.Socket>.
If fd
points to a character device that only supports blocking reads\n(such as keyboard or sound card), read operations do not finish until data is\navailable. This can prevent the process from exiting and the stream from\nclosing naturally.
By default, the stream will emit a 'close'
event after it has been\ndestroyed. Set the emitClose
option to false
to change this behavior.
By providing the fs
option, it is possible to override the corresponding fs
\nimplementations for open
, read
, and close
. When providing the fs
option,\nan override for read
is required. If no fd
is provided, an override for\nopen
is also required. If autoClose
is true
, an override for close
is\nalso required.
import { createReadStream } from 'node:fs';\n\n// Create a stream from some character device.\nconst stream = createReadStream('/dev/input/event0');\nsetTimeout(() => {\n stream.close(); // This may not close the stream.\n // Artificially marking end-of-stream, as if the underlying resource had\n // indicated end-of-file by itself, allows the stream to close.\n // This does not cancel pending read operations, and if there is such an\n // operation, the process may still not be able to exit successfully\n // until it finishes.\n stream.push(null);\n stream.read(0);\n}, 100);\n
\nIf autoClose
is false, then the file descriptor won't be closed, even if\nthere's an error. It is the application's responsibility to close it and make\nsure there's no file descriptor leak. If autoClose
is set to true (default\nbehavior), on 'error'
or 'end'
the file descriptor will be closed\nautomatically.
mode
sets the file mode (permission and sticky bits), but only if the\nfile was created.
An example to read the last 10 bytes of a file which is 100 bytes long:
\nimport { createReadStream } from 'node:fs';\n\ncreateReadStream('sample.txt', { start: 90, end: 99 });\n
\nIf options
is a string, then it specifies the encoding.
options
may also include a start
option to allow writing data at some\nposition past the beginning of the file, allowed values are in the\n[0, Number.MAX_SAFE_INTEGER
] range. Modifying a file rather than\nreplacing it may require the flags
option to be set to r+
rather than the\ndefault w
. The encoding
can be any one of those accepted by <Buffer>.
If autoClose
is set to true (default behavior) on 'error'
or 'finish'
\nthe file descriptor will be closed automatically. If autoClose
is false,\nthen the file descriptor won't be closed, even if there's an error.\nIt is the application's responsibility to close it and make sure there's no\nfile descriptor leak.
By default, the stream will emit a 'close'
event after it has been\ndestroyed. Set the emitClose
option to false
to change this behavior.
By providing the fs
option it is possible to override the corresponding fs
\nimplementations for open
, write
, writev
, and close
. Overriding write()
\nwithout writev()
can reduce performance as some optimizations (_writev()
)\nwill be disabled. When providing the fs
option, overrides for at least one of\nwrite
and writev
are required. If no fd
option is supplied, an override\nfor open
is also required. If autoClose
is true
, an override for close
\nis also required.
Like <fs.ReadStream>, if fd
is specified, <fs.WriteStream> will ignore the\npath
argument and will use the specified file descriptor. This means that no\n'open'
event will be emitted. fd
should be blocking; non-blocking fd
s\nshould be passed to <net.Socket>.
If options
is a string, then it specifies the encoding.
Test whether or not the given path exists by checking with the file system.\nThen call the callback
argument with either true or false:
import { exists } from 'node:fs';\n\nexists('/etc/passwd', (e) => {\n console.log(e ? 'it exists' : 'no passwd!');\n});\n
\nThe parameters for this callback are not consistent with other Node.js\ncallbacks. Normally, the first parameter to a Node.js callback is an err
\nparameter, optionally followed by other parameters. The fs.exists()
callback\nhas only one boolean parameter. This is one reason fs.access()
is recommended\ninstead of fs.exists()
.
Using fs.exists()
to check for the existence of a file before calling\nfs.open()
, fs.readFile()
, or fs.writeFile()
is not recommended. Doing\nso introduces a race condition, since other processes may change the file's\nstate between the two calls. Instead, user code should open/read/write the\nfile directly and handle the error raised if the file does not exist.
write (NOT RECOMMENDED)
\nimport { exists, open, close } from 'node:fs';\n\nexists('myfile', (e) => {\n if (e) {\n console.error('myfile already exists');\n } else {\n open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n\n try {\n writeMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n });\n }\n});\n
\nwrite (RECOMMENDED)
\nimport { open, close } from 'node:fs';\nopen('myfile', 'wx', (err, fd) => {\n if (err) {\n if (err.code === 'EEXIST') {\n console.error('myfile already exists');\n return;\n }\n\n throw err;\n }\n\n try {\n writeMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n});\n
\nread (NOT RECOMMENDED)
\nimport { open, close, exists } from 'node:fs';\n\nexists('myfile', (e) => {\n if (e) {\n open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n\n try {\n readMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n });\n } else {\n console.error('myfile does not exist');\n }\n});\n
\nread (RECOMMENDED)
\nimport { open, close } from 'node:fs';\n\nopen('myfile', 'r', (err, fd) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n try {\n readMyData(fd);\n } finally {\n close(fd, (err) => {\n if (err) throw err;\n });\n }\n});\n
\nThe \"not recommended\" examples above check for existence and then use the\nfile; the \"recommended\" examples are better because they use the file directly\nand handle the error, if any.
\nIn general, check for the existence of a file only if the file won't be\nused directly, for example when its existence is a signal from another\nprocess.
" }, { "textRaw": "`fs.fchmod(fd, mode, callback)`", "type": "method", "name": "fchmod", "meta": { "added": [ "v0.4.7" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`fd` {integer}", "name": "fd", "type": "integer" }, { "textRaw": "`mode` {string|integer}", "name": "mode", "type": "string|integer" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Sets the permissions on the file. No arguments other than a possible exception\nare given to the completion callback.
\nSee the POSIX fchmod(2)
documentation for more detail.
Sets the owner of the file. No arguments other than a possible exception are\ngiven to the completion callback.
\nSee the POSIX fchown(2)
documentation for more detail.
Forces all currently queued I/O operations associated with the file to the\noperating system's synchronized I/O completion state. Refer to the POSIX\nfdatasync(2)
documentation for details. No arguments other than a possible\nexception are given to the completion callback.
Invokes the callback with the <fs.Stats> for the file descriptor.
\nSee the POSIX fstat(2)
documentation for more detail.
Request that all data for the open file descriptor is flushed to the storage\ndevice. The specific implementation is operating system and device specific.\nRefer to the POSIX fsync(2)
documentation for more detail. No arguments other\nthan a possible exception are given to the completion callback.
Truncates the file descriptor. No arguments other than a possible exception are\ngiven to the completion callback.
\nSee the POSIX ftruncate(2)
documentation for more detail.
If the file referred to by the file descriptor was larger than len
bytes, only\nthe first len
bytes will be retained in the file.
For example, the following program retains only the first four bytes of the\nfile:
\nimport { open, close, ftruncate } from 'node:fs';\n\nfunction closeFd(fd) {\n close(fd, (err) => {\n if (err) throw err;\n });\n}\n\nopen('temp.txt', 'r+', (err, fd) => {\n if (err) throw err;\n\n try {\n ftruncate(fd, 4, (err) => {\n closeFd(fd);\n if (err) throw err;\n });\n } catch (err) {\n closeFd(fd);\n if (err) throw err;\n }\n});\n
\nIf the file previously was shorter than len
bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'
):
If len
is negative then 0
will be used.
Change the file system timestamps of the object referenced by the supplied file\ndescriptor. See fs.utimes()
.
Changes the permissions on a symbolic link. No arguments other than a possible\nexception are given to the completion callback.
\nThis method is only implemented on macOS.
\nSee the POSIX lchmod(2)
documentation for more detail.
Set the owner of the symbolic link. No arguments other than a possible\nexception are given to the completion callback.
\nSee the POSIX lchown(2)
documentation for more detail.
Changes the access and modification times of a file in the same way as\nfs.utimes()
, with the difference that if the path refers to a symbolic\nlink, then the link is not dereferenced: instead, the timestamps of the\nsymbolic link itself are changed.
No arguments other than a possible exception are given to the completion\ncallback.
" }, { "textRaw": "`fs.link(existingPath, newPath, callback)`", "type": "method", "name": "link", "meta": { "added": [ "v0.1.31" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `existingPath` and `newPath` parameters can be WHATWG `URL` objects using `file:` protocol. Support is currently still *experimental*." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`existingPath` {string|Buffer|URL}", "name": "existingPath", "type": "string|Buffer|URL" }, { "textRaw": "`newPath` {string|Buffer|URL}", "name": "newPath", "type": "string|Buffer|URL" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Creates a new link from the existingPath
to the newPath
. See the POSIX\nlink(2)
documentation for more detail. No arguments other than a possible\nexception are given to the completion callback.
Retrieves the <fs.Stats> for the symbolic link referred to by the path.\nThe callback gets two arguments (err, stats)
where stats
is a <fs.Stats>\nobject. lstat()
is identical to stat()
, except that if path
is a symbolic\nlink, then the link itself is stat-ed, not the file that it refers to.
See the POSIX lstat(2)
documentation for more details.
Asynchronously creates a directory.
\nThe callback is given a possible exception and, if recursive
is true
, the\nfirst directory path created, (err[, path])
.\npath
can still be undefined
when recursive
is true
, if no directory was\ncreated (for instance, if it was previously created).
The optional options
argument can be an integer specifying mode
(permission\nand sticky bits), or an object with a mode
property and a recursive
\nproperty indicating whether parent directories should be created. Calling\nfs.mkdir()
when path
is a directory that exists results in an error only\nwhen recursive
is false. If recursive
is false and the directory exists,\nan EEXIST
error occurs.
import { mkdir } from 'node:fs';\n\n// Create ./tmp/a/apple, regardless of whether ./tmp and ./tmp/a exist.\nmkdir('./tmp/a/apple', { recursive: true }, (err) => {\n if (err) throw err;\n});\n
\nOn Windows, using fs.mkdir()
on the root directory even with recursion will\nresult in an error:
import { mkdir } from 'node:fs';\n\nmkdir('/', { recursive: true }, (err) => {\n // => [Error: EPERM: operation not permitted, mkdir 'C:\\']\n});\n
\nSee the POSIX mkdir(2)
documentation for more details.
Creates a unique temporary directory.
\nGenerates six random characters to be appended behind a required\nprefix
to create a unique temporary directory. Due to platform\ninconsistencies, avoid trailing X
characters in prefix
. Some platforms,\nnotably the BSDs, can return more than six random characters, and replace\ntrailing X
characters in prefix
with random characters.
The created directory path is passed as a string to the callback's second\nparameter.
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use.
import { mkdtemp } from 'node:fs';\nimport { join } from 'node:path';\nimport { tmpdir } from 'node:os';\n\nmkdtemp(join(tmpdir(), 'foo-'), (err, directory) => {\n if (err) throw err;\n console.log(directory);\n // Prints: /tmp/foo-itXde2 or C:\\Users\\...\\AppData\\Local\\Temp\\foo-itXde2\n});\n
\nThe fs.mkdtemp()
method will append the six randomly selected characters\ndirectly to the prefix
string. For instance, given a directory /tmp
, if the\nintention is to create a temporary directory within /tmp
, the prefix
\nmust end with a trailing platform-specific path separator\n(require('node:path').sep
).
import { tmpdir } from 'node:os';\nimport { mkdtemp } from 'node:fs';\n\n// The parent directory for the new temporary directory\nconst tmpDir = tmpdir();\n\n// This method is *INCORRECT*:\nmkdtemp(tmpDir, (err, directory) => {\n if (err) throw err;\n console.log(directory);\n // Will print something similar to `/tmpabc123`.\n // A new temporary directory is created at the file system root\n // rather than *within* the /tmp directory.\n});\n\n// This method is *CORRECT*:\nimport { sep } from 'node:path';\nmkdtemp(`${tmpDir}${sep}`, (err, directory) => {\n if (err) throw err;\n console.log(directory);\n // Will print something similar to `/tmp/abc123`.\n // A new temporary directory is created within\n // the /tmp directory.\n});\n
"
},
{
"textRaw": "`fs.open(path[, flags[, mode]], callback)`",
"type": "method",
"name": "open",
"meta": {
"added": [
"v0.0.2"
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"changes": [
{
"version": "v18.0.0",
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},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`flags` {string|number} See [support of file system `flags`][]. **Default:** `'r'`.",
"name": "flags",
"type": "string|number",
"default": "`'r'`",
"desc": "See [support of file system `flags`][]."
},
{
"textRaw": "`mode` {string|integer} **Default:** `0o666` (readable and writable)",
"name": "mode",
"type": "string|integer",
"default": "`0o666` (readable and writable)"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`fd` {integer}",
"name": "fd",
"type": "integer"
}
]
}
]
}
],
"desc": "Asynchronous file open. See the POSIX open(2)
documentation for more details.
mode
sets the file mode (permission and sticky bits), but only if the file was\ncreated. On Windows, only the write permission can be manipulated; see\nfs.chmod()
.
The callback gets two arguments (err, fd)
.
Some characters (< > : \" / \\ | ? *
) are reserved under Windows as documented\nby Naming Files, Paths, and Namespaces. Under NTFS, if the filename contains\na colon, Node.js will open a file system stream, as described by\nthis MSDN page.
Functions based on fs.open()
exhibit this behavior as well:\nfs.writeFile()
, fs.readFile()
, etc.
Returns a <Blob> whose data is backed by the given file.
\nThe file must not be modified after the <Blob> is created. Any modifications\nwill cause reading the <Blob> data to fail with a DOMException
error.\nSynchronous stat operations on the file when the Blob
is created, and before\neach read in order to detect whether the file data has been modified on disk.
import { openAsBlob } from 'node:fs';\n\nconst blob = await openAsBlob('the.file.txt');\nconst ab = await blob.arrayBuffer();\nblob.stream();\n
\nconst { openAsBlob } = require('node:fs');\n\n(async () => {\n const blob = await openAsBlob('the.file.txt');\n const ab = await blob.arrayBuffer();\n blob.stream();\n})();\n
"
},
{
"textRaw": "`fs.opendir(path[, options], callback)`",
"type": "method",
"name": "opendir",
"meta": {
"added": [
"v12.12.0"
],
"changes": [
{
"version": [
"v20.1.0",
"v18.17.0"
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"description": "Added `recursive` option."
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{
"version": [
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"pr-url": "https://github.com/nodejs/node/pull/30114",
"description": "The `bufferSize` option was introduced."
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]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`encoding` {string|null} **Default:** `'utf8'`",
"name": "encoding",
"type": "string|null",
"default": "`'utf8'`"
},
{
"textRaw": "`bufferSize` {number} Number of directory entries that are buffered internally when reading from the directory. Higher values lead to better performance but higher memory usage. **Default:** `32`",
"name": "bufferSize",
"type": "number",
"default": "`32`",
"desc": "Number of directory entries that are buffered internally when reading from the directory. Higher values lead to better performance but higher memory usage."
},
{
"textRaw": "`recursive` {boolean} **Default:** `false`",
"name": "recursive",
"type": "boolean",
"default": "`false`"
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`dir` {fs.Dir}",
"name": "dir",
"type": "fs.Dir"
}
]
}
]
}
],
"desc": "Asynchronously open a directory. See the POSIX opendir(3)
documentation for\nmore details.
Creates an <fs.Dir>, which contains all further functions for reading from\nand cleaning up the directory.
\nThe encoding
option sets the encoding for the path
while opening the\ndirectory and subsequent read operations.
Read data from the file specified by fd
.
The callback is given the three arguments, (err, bytesRead, buffer)
.
If the file is not modified concurrently, the end-of-file is reached when the\nnumber of bytes read is zero.
\nIf this method is invoked as its util.promisify()
ed version, it returns\na promise for an Object
with bytesRead
and buffer
properties.
Similar to the fs.read()
function, this version takes an optional\noptions
object. If no options
object is specified, it will default with the\nabove values.
Similar to the fs.read()
function, this version takes an optional\noptions
object. If no options
object is specified, it will default with the\nabove values.
Reads the contents of a directory. The callback gets two arguments (err, files)
\nwhere files
is an array of the names of the files in the directory excluding\n'.'
and '..'
.
See the POSIX readdir(3)
documentation for more details.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe filenames passed to the callback. If the encoding
is set to 'buffer'
,\nthe filenames returned will be passed as <Buffer> objects.
If options.withFileTypes
is set to true
, the files
array will contain\n<fs.Dirent> objects.
Asynchronously reads the entire contents of a file.
\nimport { readFile } from 'node:fs';\n\nreadFile('/etc/passwd', (err, data) => {\n if (err) throw err;\n console.log(data);\n});\n
\nThe callback is passed two arguments (err, data)
, where data
is the\ncontents of the file.
If no encoding is specified, then the raw buffer is returned.
\nIf options
is a string, then it specifies the encoding:
import { readFile } from 'node:fs';\n\nreadFile('/etc/passwd', 'utf8', callback);\n
\nWhen the path is a directory, the behavior of fs.readFile()
and\nfs.readFileSync()
is platform-specific. On macOS, Linux, and Windows, an\nerror will be returned. On FreeBSD, a representation of the directory's contents\nwill be returned.
import { readFile } from 'node:fs';\n\n// macOS, Linux, and Windows\nreadFile('<directory>', (err, data) => {\n // => [Error: EISDIR: illegal operation on a directory, read <directory>]\n});\n\n// FreeBSD\nreadFile('<directory>', (err, data) => {\n // => null, <data>\n});\n
\nIt is possible to abort an ongoing request using an AbortSignal
. If a\nrequest is aborted the callback is called with an AbortError
:
import { readFile } from 'node:fs';\n\nconst controller = new AbortController();\nconst signal = controller.signal;\nreadFile(fileInfo[0].name, { signal }, (err, buf) => {\n // ...\n});\n// When you want to abort the request\ncontroller.abort();\n
\nThe fs.readFile()
function buffers the entire file. To minimize memory costs,\nwhen possible prefer streaming via fs.createReadStream()
.
Aborting an ongoing request does not abort individual operating\nsystem requests but rather the internal buffering fs.readFile
performs.
path
, it will not be closed\nautomatically.'Hello World'
and six bytes are read with the file descriptor,\nthe call to fs.readFile()
with the same file descriptor, would give\n'World'
, rather than 'Hello World'
.The fs.readFile()
method asynchronously reads the contents of a file into\nmemory one chunk at a time, allowing the event loop to turn between each chunk.\nThis allows the read operation to have less impact on other activity that may\nbe using the underlying libuv thread pool but means that it will take longer\nto read a complete file into memory.
The additional read overhead can vary broadly on different systems and depends\non the type of file being read. If the file type is not a regular file (a pipe\nfor instance) and Node.js is unable to determine an actual file size, each read\noperation will load on 64 KiB of data. For regular files, each read will process\n512 KiB of data.
\nFor applications that require as-fast-as-possible reading of file contents, it\nis better to use fs.read()
directly and for application code to manage\nreading the full contents of the file itself.
The Node.js GitHub issue #25741 provides more information and a detailed\nanalysis on the performance of fs.readFile()
for multiple file sizes in\ndifferent Node.js versions.
Reads the contents of the symbolic link referred to by path
. The callback gets\ntwo arguments (err, linkString)
.
See the POSIX readlink(2)
documentation for more details.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe link path passed to the callback. If the encoding
is set to 'buffer'
,\nthe link path returned will be passed as a <Buffer> object.
Read from a file specified by fd
and write to an array of ArrayBufferView
s\nusing readv()
.
position
is the offset from the beginning of the file from where data\nshould be read. If typeof position !== 'number'
, the data will be read\nfrom the current position.
The callback will be given three arguments: err
, bytesRead
, and\nbuffers
. bytesRead
is how many bytes were read from the file.
If this method is invoked as its util.promisify()
ed version, it returns\na promise for an Object
with bytesRead
and buffers
properties.
Asynchronously computes the canonical pathname by resolving .
, ..
, and\nsymbolic links.
A canonical pathname is not necessarily unique. Hard links and bind mounts can\nexpose a file system entity through many pathnames.
\nThis function behaves like realpath(3)
, with some exceptions:
No case conversion is performed on case-insensitive file systems.
\nThe maximum number of symbolic links is platform-independent and generally\n(much) higher than what the native realpath(3)
implementation supports.
The callback
gets two arguments (err, resolvedPath)
. May use process.cwd
\nto resolve relative paths.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe path passed to the callback. If the encoding
is set to 'buffer'
,\nthe path returned will be passed as a <Buffer> object.
If path
resolves to a socket or a pipe, the function will return a system\ndependent name for that object.
Asynchronous realpath(3)
.
The callback
gets two arguments (err, resolvedPath)
.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe path passed to the callback. If the encoding
is set to 'buffer'
,\nthe path returned will be passed as a <Buffer> object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc
in order for this function to work. Glibc does not have\nthis restriction.
Asynchronously rename file at oldPath
to the pathname provided\nas newPath
. In the case that newPath
already exists, it will\nbe overwritten. If there is a directory at newPath
, an error will\nbe raised instead. No arguments other than a possible exception are\ngiven to the completion callback.
See also: rename(2)
.
import { rename } from 'node:fs';\n\nrename('oldFile.txt', 'newFile.txt', (err) => {\n if (err) throw err;\n console.log('Rename complete!');\n});\n
"
},
{
"textRaw": "`fs.rmdir(path[, options], callback)`",
"type": "method",
"name": "rmdir",
"meta": {
"added": [
"v0.0.2"
],
"changes": [
{
"version": "v18.0.0",
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"version": "v16.0.0",
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"description": "Using `fs.rmdir(path, { recursive: true })` on a `path` that is a file is no longer permitted and results in an `ENOENT` error on Windows and an `ENOTDIR` error on POSIX."
},
{
"version": "v16.0.0",
"pr-url": "https://github.com/nodejs/node/pull/37216",
"description": "Using `fs.rmdir(path, { recursive: true })` on a `path` that does not exist is no longer permitted and results in a `ENOENT` error."
},
{
"version": "v16.0.0",
"pr-url": "https://github.com/nodejs/node/pull/37302",
"description": "The `recursive` option is deprecated, using it triggers a deprecation warning."
},
{
"version": "v14.14.0",
"pr-url": "https://github.com/nodejs/node/pull/35579",
"description": "The `recursive` option is deprecated, use `fs.rm` instead."
},
{
"version": [
"v13.3.0",
"v12.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/30644",
"description": "The `maxBusyTries` option is renamed to `maxRetries`, and its default is 0. The `emfileWait` option has been removed, and `EMFILE` errors use the same retry logic as other errors. The `retryDelay` option is now supported. `ENFILE` errors are now retried."
},
{
"version": "v12.10.0",
"pr-url": "https://github.com/nodejs/node/pull/29168",
"description": "The `recursive`, `maxBusyTries`, and `emfileWait` options are now supported."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/12562",
"description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime."
},
{
"version": "v7.6.0",
"pr-url": "https://github.com/nodejs/node/pull/10739",
"description": "The `path` parameters can be a WHATWG `URL` object using `file:` protocol."
},
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/7897",
"description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`maxRetries` {integer} If an `EBUSY`, `EMFILE`, `ENFILE`, `ENOTEMPTY`, or `EPERM` error is encountered, Node.js retries the operation with a linear backoff wait of `retryDelay` milliseconds longer on each try. This option represents the number of retries. This option is ignored if the `recursive` option is not `true`. **Default:** `0`.",
"name": "maxRetries",
"type": "integer",
"default": "`0`",
"desc": "If an `EBUSY`, `EMFILE`, `ENFILE`, `ENOTEMPTY`, or `EPERM` error is encountered, Node.js retries the operation with a linear backoff wait of `retryDelay` milliseconds longer on each try. This option represents the number of retries. This option is ignored if the `recursive` option is not `true`."
},
{
"textRaw": "`recursive` {boolean} If `true`, perform a recursive directory removal. In recursive mode, operations are retried on failure. **Default:** `false`. **Deprecated.**",
"name": "recursive",
"type": "boolean",
"default": "`false`. **Deprecated.**",
"desc": "If `true`, perform a recursive directory removal. In recursive mode, operations are retried on failure."
},
{
"textRaw": "`retryDelay` {integer} The amount of time in milliseconds to wait between retries. This option is ignored if the `recursive` option is not `true`. **Default:** `100`.",
"name": "retryDelay",
"type": "integer",
"default": "`100`",
"desc": "The amount of time in milliseconds to wait between retries. This option is ignored if the `recursive` option is not `true`."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
}
]
}
]
}
],
"desc": "Asynchronous rmdir(2)
. No arguments other than a possible exception are given\nto the completion callback.
Using fs.rmdir()
on a file (not a directory) results in an ENOENT
error on\nWindows and an ENOTDIR
error on POSIX.
To get a behavior similar to the rm -rf
Unix command, use fs.rm()
\nwith options { recursive: true, force: true }
.
Asynchronously removes files and directories (modeled on the standard POSIX rm
\nutility). No arguments other than a possible exception are given to the\ncompletion callback.
Asynchronous stat(2)
. The callback gets two arguments (err, stats)
where\nstats
is an <fs.Stats> object.
In case of an error, the err.code
will be one of Common System Errors.
fs.stat()
follows symbolic links. Use fs.lstat()
to look at the\nlinks themselves.
Using fs.stat()
to check for the existence of a file before calling\nfs.open()
, fs.readFile()
, or fs.writeFile()
is not recommended.\nInstead, user code should open/read/write the file directly and handle the\nerror raised if the file is not available.
To check if a file exists without manipulating it afterwards, fs.access()
\nis recommended.
For example, given the following directory structure:
\n- txtDir\n-- file.txt\n- app.js\n
\nThe next program will check for the stats of the given paths:
\nimport { stat } from 'node:fs';\n\nconst pathsToCheck = ['./txtDir', './txtDir/file.txt'];\n\nfor (let i = 0; i < pathsToCheck.length; i++) {\n stat(pathsToCheck[i], (err, stats) => {\n console.log(stats.isDirectory());\n console.log(stats);\n });\n}\n
\nThe resulting output will resemble:
\ntrue\nStats {\n dev: 16777220,\n mode: 16877,\n nlink: 3,\n uid: 501,\n gid: 20,\n rdev: 0,\n blksize: 4096,\n ino: 14214262,\n size: 96,\n blocks: 0,\n atimeMs: 1561174653071.963,\n mtimeMs: 1561174614583.3518,\n ctimeMs: 1561174626623.5366,\n birthtimeMs: 1561174126937.2893,\n atime: 2019-06-22T03:37:33.072Z,\n mtime: 2019-06-22T03:36:54.583Z,\n ctime: 2019-06-22T03:37:06.624Z,\n birthtime: 2019-06-22T03:28:46.937Z\n}\nfalse\nStats {\n dev: 16777220,\n mode: 33188,\n nlink: 1,\n uid: 501,\n gid: 20,\n rdev: 0,\n blksize: 4096,\n ino: 14214074,\n size: 8,\n blocks: 8,\n atimeMs: 1561174616618.8555,\n mtimeMs: 1561174614584,\n ctimeMs: 1561174614583.8145,\n birthtimeMs: 1561174007710.7478,\n atime: 2019-06-22T03:36:56.619Z,\n mtime: 2019-06-22T03:36:54.584Z,\n ctime: 2019-06-22T03:36:54.584Z,\n birthtime: 2019-06-22T03:26:47.711Z\n}\n
"
},
{
"textRaw": "`fs.statfs(path[, options], callback)`",
"type": "method",
"name": "statfs",
"meta": {
"added": [
"v19.6.0",
"v18.15.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`bigint` {boolean} Whether the numeric values in the returned {fs.StatFs} object should be `bigint`. **Default:** `false`.",
"name": "bigint",
"type": "boolean",
"default": "`false`",
"desc": "Whether the numeric values in the returned {fs.StatFs} object should be `bigint`."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`stats` {fs.StatFs}",
"name": "stats",
"type": "fs.StatFs"
}
]
}
]
}
],
"desc": "Asynchronous statfs(2)
. Returns information about the mounted file system which\ncontains path
. The callback gets two arguments (err, stats)
where stats
\nis an <fs.StatFs> object.
In case of an error, the err.code
will be one of Common System Errors.
Creates the link called path
pointing to target
. No arguments other than a\npossible exception are given to the completion callback.
See the POSIX symlink(2)
documentation for more details.
The type
argument is only available on Windows and ignored on other platforms.\nIt can be set to 'dir'
, 'file'
, or 'junction'
. If the type
argument is\nnot a string, Node.js will autodetect target
type and use 'file'
or 'dir'
.\nIf the target
does not exist, 'file'
will be used. Windows junction points\nrequire the destination path to be absolute. When using 'junction'
, the\ntarget
argument will automatically be normalized to absolute path. Junction\npoints on NTFS volumes can only point to directories.
Relative targets are relative to the link's parent directory.
\nimport { symlink } from 'node:fs';\n\nsymlink('./mew', './mewtwo', callback);\n
\nThe above example creates a symbolic link mewtwo
which points to mew
in the\nsame directory:
$ tree .\n.\n├── mew\n└── mewtwo -> ./mew\n
"
},
{
"textRaw": "`fs.truncate(path[, len], callback)`",
"type": "method",
"name": "truncate",
"meta": {
"added": [
"v0.8.6"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v16.0.0",
"pr-url": "https://github.com/nodejs/node/pull/37460",
"description": "The error returned may be an `AggregateError` if more than one error is returned."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/12562",
"description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime."
},
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/7897",
"description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`len` {integer} **Default:** `0`",
"name": "len",
"type": "integer",
"default": "`0`"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error|AggregateError}",
"name": "err",
"type": "Error|AggregateError"
}
]
}
]
}
],
"desc": "Truncates the file. No arguments other than a possible exception are\ngiven to the completion callback. A file descriptor can also be passed as the\nfirst argument. In this case, fs.ftruncate()
is called.
import { truncate } from 'node:fs';\n// Assuming that 'path/file.txt' is a regular file.\ntruncate('path/file.txt', (err) => {\n if (err) throw err;\n console.log('path/file.txt was truncated');\n});\n
\nconst { truncate } = require('node:fs');\n// Assuming that 'path/file.txt' is a regular file.\ntruncate('path/file.txt', (err) => {\n if (err) throw err;\n console.log('path/file.txt was truncated');\n});\n
\nPassing a file descriptor is deprecated and may result in an error being thrown\nin the future.
\nSee the POSIX truncate(2)
documentation for more details.
Asynchronously removes a file or symbolic link. No arguments other than a\npossible exception are given to the completion callback.
\nimport { unlink } from 'node:fs';\n// Assuming that 'path/file.txt' is a regular file.\nunlink('path/file.txt', (err) => {\n if (err) throw err;\n console.log('path/file.txt was deleted');\n});\n
\nfs.unlink()
will not work on a directory, empty or otherwise. To remove a\ndirectory, use fs.rmdir()
.
See the POSIX unlink(2)
documentation for more details.
Stop watching for changes on filename
. If listener
is specified, only that\nparticular listener is removed. Otherwise, all listeners are removed,\neffectively stopping watching of filename
.
Calling fs.unwatchFile()
with a filename that is not being watched is a\nno-op, not an error.
Using fs.watch()
is more efficient than fs.watchFile()
and\nfs.unwatchFile()
. fs.watch()
should be used instead of fs.watchFile()
\nand fs.unwatchFile()
when possible.
Change the file system timestamps of the object referenced by path
.
The atime
and mtime
arguments follow these rules:
Date
s, or a numeric string like '123456789.0'
.NaN
, Infinity
, or\n-Infinity
, an Error
will be thrown.Watch for changes on filename
, where filename
is either a file or a\ndirectory.
The second argument is optional. If options
is provided as a string, it\nspecifies the encoding
. Otherwise options
should be passed as an object.
The listener callback gets two arguments (eventType, filename)
. eventType
\nis either 'rename'
or 'change'
, and filename
is the name of the file\nwhich triggered the event.
On most platforms, 'rename'
is emitted whenever a filename appears or\ndisappears in the directory.
The listener callback is attached to the 'change'
event fired by\n<fs.FSWatcher>, but it is not the same thing as the 'change'
value of\neventType
.
If a signal
is passed, aborting the corresponding AbortController will close\nthe returned <fs.FSWatcher>.
The fs.watch
API is not 100% consistent across platforms, and is\nunavailable in some situations.
On Windows, no events will be emitted if the watched directory is moved or\nrenamed. An EPERM
error is reported when the watched directory is deleted.
This feature depends on the underlying operating system providing a way\nto be notified of file system changes.
\ninotify(7)
.kqueue(2)
.kqueue(2)
for files and FSEvents
for\ndirectories.event ports
.ReadDirectoryChangesW
.AHAFS
, which must be enabled.If the underlying functionality is not available for some reason, then\nfs.watch()
will not be able to function and may throw an exception.\nFor example, watching files or directories can be unreliable, and in some\ncases impossible, on network file systems (NFS, SMB, etc) or host file systems\nwhen using virtualization software such as Vagrant or Docker.
It is still possible to use fs.watchFile()
, which uses stat polling, but\nthis method is slower and less reliable.
On Linux and macOS systems, fs.watch()
resolves the path to an inode and\nwatches the inode. If the watched path is deleted and recreated, it is assigned\na new inode. The watch will emit an event for the delete but will continue\nwatching the original inode. Events for the new inode will not be emitted.\nThis is expected behavior.
AIX files retain the same inode for the lifetime of a file. Saving and closing a\nwatched file on AIX will result in two notifications (one for adding new\ncontent, and one for truncation).
" }, { "textRaw": "Filename argument", "name": "Filename argument", "type": "misc", "desc": "Providing filename
argument in the callback is only supported on Linux,\nmacOS, Windows, and AIX. Even on supported platforms, filename
is not always\nguaranteed to be provided. Therefore, don't assume that filename
argument is\nalways provided in the callback, and have some fallback logic if it is null
.
import { watch } from 'node:fs';\nwatch('somedir', (eventType, filename) => {\n console.log(`event type is: ${eventType}`);\n if (filename) {\n console.log(`filename provided: ${filename}`);\n } else {\n console.log('filename not provided');\n }\n});\n
"
}
]
}
]
},
{
"textRaw": "`fs.watchFile(filename[, options], listener)`",
"type": "method",
"name": "watchFile",
"meta": {
"added": [
"v0.1.31"
],
"changes": [
{
"version": "v10.5.0",
"pr-url": "https://github.com/nodejs/node/pull/20220",
"description": "The `bigint` option is now supported."
},
{
"version": "v7.6.0",
"pr-url": "https://github.com/nodejs/node/pull/10739",
"description": "The `filename` parameter can be a WHATWG `URL` object using `file:` protocol."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {fs.StatWatcher}",
"name": "return",
"type": "fs.StatWatcher"
},
"params": [
{
"textRaw": "`filename` {string|Buffer|URL}",
"name": "filename",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`bigint` {boolean} **Default:** `false`",
"name": "bigint",
"type": "boolean",
"default": "`false`"
},
{
"textRaw": "`persistent` {boolean} **Default:** `true`",
"name": "persistent",
"type": "boolean",
"default": "`true`"
},
{
"textRaw": "`interval` {integer} **Default:** `5007`",
"name": "interval",
"type": "integer",
"default": "`5007`"
}
]
},
{
"textRaw": "`listener` {Function}",
"name": "listener",
"type": "Function",
"options": [
{
"textRaw": "`current` {fs.Stats}",
"name": "current",
"type": "fs.Stats"
},
{
"textRaw": "`previous` {fs.Stats}",
"name": "previous",
"type": "fs.Stats"
}
]
}
]
}
],
"desc": "Watch for changes on filename
. The callback listener
will be called each\ntime the file is accessed.
The options
argument may be omitted. If provided, it should be an object. The\noptions
object may contain a boolean named persistent
that indicates\nwhether the process should continue to run as long as files are being watched.\nThe options
object may specify an interval
property indicating how often the\ntarget should be polled in milliseconds.
The listener
gets two arguments the current stat object and the previous\nstat object:
import { watchFile } from 'node:fs';\n\nwatchFile('message.text', (curr, prev) => {\n console.log(`the current mtime is: ${curr.mtime}`);\n console.log(`the previous mtime was: ${prev.mtime}`);\n});\n
\nThese stat objects are instances of fs.Stat
. If the bigint
option is true
,\nthe numeric values in these objects are specified as BigInt
s.
To be notified when the file was modified, not just accessed, it is necessary\nto compare curr.mtimeMs
and prev.mtimeMs
.
When an fs.watchFile
operation results in an ENOENT
error, it\nwill invoke the listener once, with all the fields zeroed (or, for dates, the\nUnix Epoch). If the file is created later on, the listener will be called\nagain, with the latest stat objects. This is a change in functionality since\nv0.10.
Using fs.watch()
is more efficient than fs.watchFile
and\nfs.unwatchFile
. fs.watch
should be used instead of fs.watchFile
and\nfs.unwatchFile
when possible.
When a file being watched by fs.watchFile()
disappears and reappears,\nthen the contents of previous
in the second callback event (the file's\nreappearance) will be the same as the contents of previous
in the first\ncallback event (its disappearance).
This happens when:
\nWrite buffer
to the file specified by fd
.
offset
determines the part of the buffer to be written, and length
is\nan integer specifying the number of bytes to write.
position
refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number'
, the data will be written\nat the current position. See pwrite(2)
.
The callback will be given three arguments (err, bytesWritten, buffer)
where\nbytesWritten
specifies how many bytes were written from buffer
.
If this method is invoked as its util.promisify()
ed version, it returns\na promise for an Object
with bytesWritten
and buffer
properties.
It is unsafe to use fs.write()
multiple times on the same file without waiting\nfor the callback. For this scenario, fs.createWriteStream()
is\nrecommended.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "`fs.write(fd, buffer[, options], callback)`", "type": "method", "name": "write", "meta": { "added": [ "v18.3.0", "v16.17.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`fd` {integer}", "name": "fd", "type": "integer" }, { "textRaw": "`buffer` {Buffer|TypedArray|DataView}", "name": "buffer", "type": "Buffer|TypedArray|DataView" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`offset` {integer} **Default:** `0`", "name": "offset", "type": "integer", "default": "`0`" }, { "textRaw": "`length` {integer} **Default:** `buffer.byteLength - offset`", "name": "length", "type": "integer", "default": "`buffer.byteLength - offset`" }, { "textRaw": "`position` {integer} **Default:** `null`", "name": "position", "type": "integer", "default": "`null`" } ] }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`bytesWritten` {integer}", "name": "bytesWritten", "type": "integer" }, { "textRaw": "`buffer` {Buffer|TypedArray|DataView}", "name": "buffer", "type": "Buffer|TypedArray|DataView" } ] } ] } ], "desc": "Write buffer
to the file specified by fd
.
Similar to the above fs.write
function, this version takes an\noptional options
object. If no options
object is specified, it will\ndefault with the above values.
Write string
to the file specified by fd
. If string
is not a string,\nan exception is thrown.
position
refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number'
the data will be written at\nthe current position. See pwrite(2)
.
encoding
is the expected string encoding.
The callback will receive the arguments (err, written, string)
where written
\nspecifies how many bytes the passed string required to be written. Bytes\nwritten is not necessarily the same as string characters written. See\nBuffer.byteLength
.
It is unsafe to use fs.write()
multiple times on the same file without waiting\nfor the callback. For this scenario, fs.createWriteStream()
is\nrecommended.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
\nOn Windows, if the file descriptor is connected to the console (e.g. fd == 1
\nor stdout
) a string containing non-ASCII characters will not be rendered\nproperly by default, regardless of the encoding used.\nIt is possible to configure the console to render UTF-8 properly by changing the\nactive codepage with the chcp 65001
command. See the chcp docs for more\ndetails.
When file
is a filename, asynchronously writes data to the file, replacing the\nfile if it already exists. data
can be a string or a buffer.
When file
is a file descriptor, the behavior is similar to calling\nfs.write()
directly (which is recommended). See the notes below on using\na file descriptor.
The encoding
option is ignored if data
is a buffer.
The mode
option only affects the newly created file. See fs.open()
\nfor more details.
import { writeFile } from 'node:fs';\nimport { Buffer } from 'node:buffer';\n\nconst data = new Uint8Array(Buffer.from('Hello Node.js'));\nwriteFile('message.txt', data, (err) => {\n if (err) throw err;\n console.log('The file has been saved!');\n});\n
\nIf options
is a string, then it specifies the encoding:
import { writeFile } from 'node:fs';\n\nwriteFile('message.txt', 'Hello Node.js', 'utf8', callback);\n
\nIt is unsafe to use fs.writeFile()
multiple times on the same file without\nwaiting for the callback. For this scenario, fs.createWriteStream()
is\nrecommended.
Similarly to fs.readFile
- fs.writeFile
is a convenience method that\nperforms multiple write
calls internally to write the buffer passed to it.\nFor performance sensitive code consider using fs.createWriteStream()
.
It is possible to use an <AbortSignal> to cancel an fs.writeFile()
.\nCancelation is \"best effort\", and some amount of data is likely still\nto be written.
import { writeFile } from 'node:fs';\nimport { Buffer } from 'node:buffer';\n\nconst controller = new AbortController();\nconst { signal } = controller;\nconst data = new Uint8Array(Buffer.from('Hello Node.js'));\nwriteFile('message.txt', data, { signal }, (err) => {\n // When a request is aborted - the callback is called with an AbortError\n});\n// When the request should be aborted\ncontroller.abort();\n
\nAborting an ongoing request does not abort individual operating\nsystem requests but rather the internal buffering fs.writeFile
performs.
When file
is a file descriptor, the behavior is almost identical to directly\ncalling fs.write()
like:
import { write } from 'node:fs';\nimport { Buffer } from 'node:buffer';\n\nwrite(fd, Buffer.from(data, options.encoding), callback);\n
\nThe difference from directly calling fs.write()
is that under some unusual\nconditions, fs.write()
might write only part of the buffer and need to be\nretried to write the remaining data, whereas fs.writeFile()
retries until\nthe data is entirely written (or an error occurs).
The implications of this are a common source of confusion. In\nthe file descriptor case, the file is not replaced! The data is not necessarily\nwritten to the beginning of the file, and the file's original data may remain\nbefore and/or after the newly written data.
\nFor example, if fs.writeFile()
is called twice in a row, first to write the\nstring 'Hello'
, then to write the string ', World'
, the file would contain\n'Hello, World'
, and might contain some of the file's original data (depending\non the size of the original file, and the position of the file descriptor). If\na file name had been used instead of a descriptor, the file would be guaranteed\nto contain only ', World'
.
Write an array of ArrayBufferView
s to the file specified by fd
using\nwritev()
.
position
is the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number'
, the data will be written\nat the current position.
The callback will be given three arguments: err
, bytesWritten
, and\nbuffers
. bytesWritten
is how many bytes were written from buffers
.
If this method is util.promisify()
ed, it returns a promise for an\nObject
with bytesWritten
and buffers
properties.
It is unsafe to use fs.writev()
multiple times on the same file without\nwaiting for the callback. For this scenario, use fs.createWriteStream()
.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" } ], "type": "module", "displayName": "Callback API" }, { "textRaw": "Synchronous API", "name": "synchronous_api", "desc": "The synchronous APIs perform all operations synchronously, blocking the\nevent loop until the operation completes or fails.
", "methods": [ { "textRaw": "`fs.accessSync(path[, mode])`", "type": "method", "name": "accessSync", "meta": { "added": [ "v0.11.15" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer} **Default:** `fs.constants.F_OK`", "name": "mode", "type": "integer", "default": "`fs.constants.F_OK`" } ] } ], "desc": "Synchronously tests a user's permissions for the file or directory specified\nby path
. The mode
argument is an optional integer that specifies the\naccessibility checks to be performed. mode
should be either the value\nfs.constants.F_OK
or a mask consisting of the bitwise OR of any of\nfs.constants.R_OK
, fs.constants.W_OK
, and fs.constants.X_OK
(e.g.\nfs.constants.W_OK | fs.constants.R_OK
). Check File access constants for\npossible values of mode
.
If any of the accessibility checks fail, an Error
will be thrown. Otherwise,\nthe method will return undefined
.
import { accessSync, constants } from 'node:fs';\n\ntry {\n accessSync('etc/passwd', constants.R_OK | constants.W_OK);\n console.log('can read/write');\n} catch (err) {\n console.error('no access!');\n}\n
"
},
{
"textRaw": "`fs.appendFileSync(path, data[, options])`",
"type": "method",
"name": "appendFileSync",
"meta": {
"added": [
"v0.6.7"
],
"changes": [
{
"version": "v21.1.0",
"pr-url": "https://github.com/nodejs/node/pull/50095",
"description": "The `flush` option is now supported."
},
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/7831",
"description": "The passed `options` object will never be modified."
},
{
"version": "v5.0.0",
"pr-url": "https://github.com/nodejs/node/pull/3163",
"description": "The `file` parameter can be a file descriptor now."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL|number} filename or file descriptor",
"name": "path",
"type": "string|Buffer|URL|number",
"desc": "filename or file descriptor"
},
{
"textRaw": "`data` {string|Buffer}",
"name": "data",
"type": "string|Buffer"
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`encoding` {string|null} **Default:** `'utf8'`",
"name": "encoding",
"type": "string|null",
"default": "`'utf8'`"
},
{
"textRaw": "`mode` {integer} **Default:** `0o666`",
"name": "mode",
"type": "integer",
"default": "`0o666`"
},
{
"textRaw": "`flag` {string} See [support of file system `flags`][]. **Default:** `'a'`.",
"name": "flag",
"type": "string",
"default": "`'a'`",
"desc": "See [support of file system `flags`][]."
},
{
"textRaw": "`flush` {boolean} If `true`, the underlying file descriptor is flushed prior to closing it. **Default:** `false`.",
"name": "flush",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, the underlying file descriptor is flushed prior to closing it."
}
]
}
]
}
],
"desc": "Synchronously append data to a file, creating the file if it does not yet\nexist. data
can be a string or a <Buffer>.
The mode
option only affects the newly created file. See fs.open()
\nfor more details.
import { appendFileSync } from 'node:fs';\n\ntry {\n appendFileSync('message.txt', 'data to append');\n console.log('The \"data to append\" was appended to file!');\n} catch (err) {\n /* Handle the error */\n}\n
\nIf options
is a string, then it specifies the encoding:
import { appendFileSync } from 'node:fs';\n\nappendFileSync('message.txt', 'data to append', 'utf8');\n
\nThe path
may be specified as a numeric file descriptor that has been opened\nfor appending (using fs.open()
or fs.openSync()
). The file descriptor will\nnot be closed automatically.
import { openSync, closeSync, appendFileSync } from 'node:fs';\n\nlet fd;\n\ntry {\n fd = openSync('message.txt', 'a');\n appendFileSync(fd, 'data to append', 'utf8');\n} catch (err) {\n /* Handle the error */\n} finally {\n if (fd !== undefined)\n closeSync(fd);\n}\n
"
},
{
"textRaw": "`fs.chmodSync(path, mode)`",
"type": "method",
"name": "chmodSync",
"meta": {
"added": [
"v0.6.7"
],
"changes": [
{
"version": "v7.6.0",
"pr-url": "https://github.com/nodejs/node/pull/10739",
"description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`mode` {string|integer}",
"name": "mode",
"type": "string|integer"
}
]
}
],
"desc": "For detailed information, see the documentation of the asynchronous version of\nthis API: fs.chmod()
.
See the POSIX chmod(2)
documentation for more detail.
Synchronously changes owner and group of a file. Returns undefined
.\nThis is the synchronous version of fs.chown()
.
See the POSIX chown(2)
documentation for more detail.
Closes the file descriptor. Returns undefined
.
Calling fs.closeSync()
on any file descriptor (fd
) that is currently in use\nthrough any other fs
operation may lead to undefined behavior.
See the POSIX close(2)
documentation for more detail.
Synchronously copies src
to dest
. By default, dest
is overwritten if it\nalready exists. Returns undefined
. Node.js makes no guarantees about the\natomicity of the copy operation. If an error occurs after the destination file\nhas been opened for writing, Node.js will attempt to remove the destination.
mode
is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE
).
fs.constants.COPYFILE_EXCL
: The copy operation will fail if dest
already\nexists.fs.constants.COPYFILE_FICLONE
: The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE
: The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support\ncopy-on-write, then the operation will fail.import { copyFileSync, constants } from 'node:fs';\n\n// destination.txt will be created or overwritten by default.\ncopyFileSync('source.txt', 'destination.txt');\nconsole.log('source.txt was copied to destination.txt');\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\ncopyFileSync('source.txt', 'destination.txt', constants.COPYFILE_EXCL);\n
"
},
{
"textRaw": "`fs.cpSync(src, dest[, options])`",
"type": "method",
"name": "cpSync",
"meta": {
"added": [
"v16.7.0"
],
"changes": [
{
"version": [
"v20.1.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47084",
"description": "Accept an additional `mode` option to specify the copy behavior as the `mode` argument of `fs.copyFile()`."
},
{
"version": [
"v17.6.0",
"v16.15.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41819",
"description": "Accepts an additional `verbatimSymlinks` option to specify whether to perform path resolution for symlinks."
}
]
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": [
{
"textRaw": "`src` {string|URL} source path to copy.",
"name": "src",
"type": "string|URL",
"desc": "source path to copy."
},
{
"textRaw": "`dest` {string|URL} destination path to copy to.",
"name": "dest",
"type": "string|URL",
"desc": "destination path to copy to."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`dereference` {boolean} dereference symlinks. **Default:** `false`.",
"name": "dereference",
"type": "boolean",
"default": "`false`",
"desc": "dereference symlinks."
},
{
"textRaw": "`errorOnExist` {boolean} when `force` is `false`, and the destination exists, throw an error. **Default:** `false`.",
"name": "errorOnExist",
"type": "boolean",
"default": "`false`",
"desc": "when `force` is `false`, and the destination exists, throw an error."
},
{
"textRaw": "`filter` {Function} Function to filter copied files/directories. Return `true` to copy the item, `false` to ignore it. When ignoring a directory, all of its contents will be skipped as well. **Default:** `undefined`",
"name": "filter",
"type": "Function",
"default": "`undefined`",
"desc": "Function to filter copied files/directories. Return `true` to copy the item, `false` to ignore it. When ignoring a directory, all of its contents will be skipped as well.",
"options": [
{
"textRaw": "`src` {string} source path to copy.",
"name": "src",
"type": "string",
"desc": "source path to copy."
},
{
"textRaw": "`dest` {string} destination path to copy to.",
"name": "dest",
"type": "string",
"desc": "destination path to copy to."
},
{
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
}
]
},
{
"textRaw": "`force` {boolean} overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the `errorOnExist` option to change this behavior. **Default:** `true`.",
"name": "force",
"type": "boolean",
"default": "`true`",
"desc": "overwrite existing file or directory. The copy operation will ignore errors if you set this to false and the destination exists. Use the `errorOnExist` option to change this behavior."
},
{
"textRaw": "`mode` {integer} modifiers for copy operation. **Default:** `0`. See `mode` flag of [`fs.copyFileSync()`][].",
"name": "mode",
"type": "integer",
"default": "`0`. See `mode` flag of [`fs.copyFileSync()`][]",
"desc": "modifiers for copy operation."
},
{
"textRaw": "`preserveTimestamps` {boolean} When `true` timestamps from `src` will be preserved. **Default:** `false`.",
"name": "preserveTimestamps",
"type": "boolean",
"default": "`false`",
"desc": "When `true` timestamps from `src` will be preserved."
},
{
"textRaw": "`recursive` {boolean} copy directories recursively **Default:** `false`",
"name": "recursive",
"type": "boolean",
"default": "`false`",
"desc": "copy directories recursively"
},
{
"textRaw": "`verbatimSymlinks` {boolean} When `true`, path resolution for symlinks will be skipped. **Default:** `false`",
"name": "verbatimSymlinks",
"type": "boolean",
"default": "`false`",
"desc": "When `true`, path resolution for symlinks will be skipped."
}
]
}
]
}
],
"desc": "Synchronously copies the entire directory structure from src
to dest
,\nincluding subdirectories and files.
When copying a directory to another directory, globs are not supported and\nbehavior is similar to cp dir1/ dir2/
.
Returns true
if the path exists, false
otherwise.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.exists()
.
fs.exists()
is deprecated, but fs.existsSync()
is not. The callback
\nparameter to fs.exists()
accepts parameters that are inconsistent with other\nNode.js callbacks. fs.existsSync()
does not use a callback.
import { existsSync } from 'node:fs';\n\nif (existsSync('/etc/passwd'))\n console.log('The path exists.');\n
"
},
{
"textRaw": "`fs.fchmodSync(fd, mode)`",
"type": "method",
"name": "fchmodSync",
"meta": {
"added": [
"v0.4.7"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fd` {integer}",
"name": "fd",
"type": "integer"
},
{
"textRaw": "`mode` {string|integer}",
"name": "mode",
"type": "string|integer"
}
]
}
],
"desc": "Sets the permissions on the file. Returns undefined
.
See the POSIX fchmod(2)
documentation for more detail.
Sets the owner of the file. Returns undefined
.
See the POSIX fchown(2)
documentation for more detail.
Forces all currently queued I/O operations associated with the file to the\noperating system's synchronized I/O completion state. Refer to the POSIX\nfdatasync(2)
documentation for details. Returns undefined
.
Retrieves the <fs.Stats> for the file descriptor.
\nSee the POSIX fstat(2)
documentation for more detail.
Request that all data for the open file descriptor is flushed to the storage\ndevice. The specific implementation is operating system and device specific.\nRefer to the POSIX fsync(2)
documentation for more detail. Returns undefined
.
Truncates the file descriptor. Returns undefined
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.ftruncate()
.
Synchronous version of fs.futimes()
. Returns undefined
.
Changes the permissions on a symbolic link. Returns undefined
.
This method is only implemented on macOS.
\nSee the POSIX lchmod(2)
documentation for more detail.
Set the owner for the path. Returns undefined
.
See the POSIX lchown(2)
documentation for more details.
Change the file system timestamps of the symbolic link referenced by path
.\nReturns undefined
, or throws an exception when parameters are incorrect or\nthe operation fails. This is the synchronous version of fs.lutimes()
.
Creates a new link from the existingPath
to the newPath
. See the POSIX\nlink(2)
documentation for more detail. Returns undefined
.
Retrieves the <fs.Stats> for the symbolic link referred to by path
.
See the POSIX lstat(2)
documentation for more details.
Synchronously creates a directory. Returns undefined
, or if recursive
is\ntrue
, the first directory path created.\nThis is the synchronous version of fs.mkdir()
.
See the POSIX mkdir(2)
documentation for more details.
Returns the created directory path.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.mkdtemp()
.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use.
Synchronously open a directory. See opendir(3)
.
Creates an <fs.Dir>, which contains all further functions for reading from\nand cleaning up the directory.
\nThe encoding
option sets the encoding for the path
while opening the\ndirectory and subsequent read operations.
Returns an integer representing the file descriptor.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.open()
.
Reads the contents of the directory.
\nSee the POSIX readdir(3)
documentation for more details.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe filenames returned. If the encoding
is set to 'buffer'
,\nthe filenames returned will be passed as <Buffer> objects.
If options.withFileTypes
is set to true
, the result will contain\n<fs.Dirent> objects.
Returns the contents of the path
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.readFile()
.
If the encoding
option is specified then this function returns a\nstring. Otherwise it returns a buffer.
Similar to fs.readFile()
, when the path is a directory, the behavior of\nfs.readFileSync()
is platform-specific.
import { readFileSync } from 'node:fs';\n\n// macOS, Linux, and Windows\nreadFileSync('<directory>');\n// => [Error: EISDIR: illegal operation on a directory, read <directory>]\n\n// FreeBSD\nreadFileSync('<directory>'); // => <data>\n
"
},
{
"textRaw": "`fs.readlinkSync(path[, options])`",
"type": "method",
"name": "readlinkSync",
"meta": {
"added": [
"v0.1.31"
],
"changes": [
{
"version": "v7.6.0",
"pr-url": "https://github.com/nodejs/node/pull/10739",
"description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string|Buffer}",
"name": "return",
"type": "string|Buffer"
},
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {string|Object}",
"name": "options",
"type": "string|Object",
"options": [
{
"textRaw": "`encoding` {string} **Default:** `'utf8'`",
"name": "encoding",
"type": "string",
"default": "`'utf8'`"
}
]
}
]
}
],
"desc": "Returns the symbolic link's string value.
\nSee the POSIX readlink(2)
documentation for more details.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe link path returned. If the encoding
is set to 'buffer'
,\nthe link path returned will be passed as a <Buffer> object.
Returns the number of bytesRead
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.read()
.
Returns the number of bytesRead
.
Similar to the above fs.readSync
function, this version takes an optional options
object.\nIf no options
object is specified, it will default with the above values.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.read()
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.readv()
.
Returns the resolved pathname.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.realpath()
.
Synchronous realpath(3)
.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe path returned. If the encoding
is set to 'buffer'
,\nthe path returned will be passed as a <Buffer> object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc
in order for this function to work. Glibc does not have\nthis restriction.
Renames the file from oldPath
to newPath
. Returns undefined
.
See the POSIX rename(2)
documentation for more details.
Synchronous rmdir(2)
. Returns undefined
.
Using fs.rmdirSync()
on a file (not a directory) results in an ENOENT
error\non Windows and an ENOTDIR
error on POSIX.
To get a behavior similar to the rm -rf
Unix command, use fs.rmSync()
\nwith options { recursive: true, force: true }
.
Synchronously removes files and directories (modeled on the standard POSIX rm
\nutility). Returns undefined
.
Retrieves the <fs.Stats> for the path.
" }, { "textRaw": "`fs.statfsSync(path[, options])`", "type": "method", "name": "statfsSync", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {fs.StatFs}", "name": "return", "type": "fs.StatFs" }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`bigint` {boolean} Whether the numeric values in the returned {fs.StatFs} object should be `bigint`. **Default:** `false`.", "name": "bigint", "type": "boolean", "default": "`false`", "desc": "Whether the numeric values in the returned {fs.StatFs} object should be `bigint`." } ] } ] } ], "desc": "Synchronous statfs(2)
. Returns information about the mounted file system which\ncontains path
.
In case of an error, the err.code
will be one of Common System Errors.
Returns undefined
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.symlink()
.
Truncates the file. Returns undefined
. A file descriptor can also be\npassed as the first argument. In this case, fs.ftruncateSync()
is called.
Passing a file descriptor is deprecated and may result in an error being thrown\nin the future.
" }, { "textRaw": "`fs.unlinkSync(path)`", "type": "method", "name": "unlinkSync", "meta": { "added": [ "v0.1.21" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" } ] } ], "desc": "Synchronous unlink(2)
. Returns undefined
.
Returns undefined
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.utimes()
.
Returns undefined
.
The mode
option only affects the newly created file. See fs.open()
\nfor more details.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.writeFile()
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, buffer...)
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, buffer...)
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, string...)
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.writev()
.
The common objects are shared by all of the file system API variants\n(promise, callback, and synchronous).
", "classes": [ { "textRaw": "Class: `fs.Dir`", "type": "class", "name": "fs.Dir", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "desc": "A class representing a directory stream.
\nCreated by fs.opendir()
, fs.opendirSync()
, or\nfsPromises.opendir()
.
import { opendir } from 'node:fs/promises';\n\ntry {\n const dir = await opendir('./');\n for await (const dirent of dir)\n console.log(dirent.name);\n} catch (err) {\n console.error(err);\n}\n
\nWhen using the async iterator, the <fs.Dir> object will be automatically\nclosed after the iterator exits.
", "methods": [ { "textRaw": "`dir.close()`", "type": "method", "name": "close", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [] } ], "desc": "Asynchronously close the directory's underlying resource handle.\nSubsequent reads will result in errors.
\nA promise is returned that will be fulfilled after the resource has been\nclosed.
" }, { "textRaw": "`dir.close(callback)`", "type": "method", "name": "close", "meta": { "added": [ "v12.12.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." } ] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Asynchronously close the directory's underlying resource handle.\nSubsequent reads will result in errors.
\nThe callback
will be called after the resource handle has been closed.
Synchronously close the directory's underlying resource handle.\nSubsequent reads will result in errors.
" }, { "textRaw": "`dir.read()`", "type": "method", "name": "read", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with a {fs.Dirent|null}", "name": "return", "type": "Promise", "desc": "Fulfills with a {fs.Dirent|null}" }, "params": [] } ], "desc": "Asynchronously read the next directory entry via readdir(3)
as an\n<fs.Dirent>.
A promise is returned that will be fulfilled with an <fs.Dirent>, or null
\nif there are no more directory entries to read.
Directory entries returned by this function are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory might not be\nincluded in the iteration results.
" }, { "textRaw": "`dir.read(callback)`", "type": "method", "name": "read", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`dirent` {fs.Dirent|null}", "name": "dirent", "type": "fs.Dirent|null" } ] } ] } ], "desc": "Asynchronously read the next directory entry via readdir(3)
as an\n<fs.Dirent>.
After the read is completed, the callback
will be called with an\n<fs.Dirent>, or null
if there are no more directory entries to read.
Directory entries returned by this function are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory might not be\nincluded in the iteration results.
" }, { "textRaw": "`dir.readSync()`", "type": "method", "name": "readSync", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {fs.Dirent|null}", "name": "return", "type": "fs.Dirent|null" }, "params": [] } ], "desc": "Synchronously read the next directory entry as an <fs.Dirent>. See the\nPOSIX readdir(3)
documentation for more detail.
If there are no more directory entries to read, null
will be returned.
Directory entries returned by this function are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory might not be\nincluded in the iteration results.
" }, { "textRaw": "`dir[Symbol.asyncIterator]()`", "type": "method", "name": "[Symbol.asyncIterator]", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {AsyncIterator} An AsyncIterator of {fs.Dirent}", "name": "return", "type": "AsyncIterator", "desc": "An AsyncIterator of {fs.Dirent}" }, "params": [] } ], "desc": "Asynchronously iterates over the directory until all entries have\nbeen read. Refer to the POSIX readdir(3)
documentation for more detail.
Entries returned by the async iterator are always an <fs.Dirent>.\nThe null
case from dir.read()
is handled internally.
See <fs.Dir> for an example.
\nDirectory entries returned by this iterator are in no particular order as\nprovided by the operating system's underlying directory mechanisms.\nEntries added or removed while iterating over the directory might not be\nincluded in the iteration results.
" } ], "properties": [ { "textRaw": "`path` {string}", "type": "string", "name": "path", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "desc": "The read-only path of this directory as was provided to fs.opendir()
,\nfs.opendirSync()
, or fsPromises.opendir()
.
A representation of a directory entry, which can be a file or a subdirectory\nwithin the directory, as returned by reading from an <fs.Dir>. The\ndirectory entry is a combination of the file name and file type pairs.
\nAdditionally, when fs.readdir()
or fs.readdirSync()
is called with\nthe withFileTypes
option set to true
, the resulting array is filled with\n<fs.Dirent> objects, rather than strings or <Buffer>s.
Returns true
if the <fs.Dirent> object describes a block device.
Returns true
if the <fs.Dirent> object describes a character device.
Returns true
if the <fs.Dirent> object describes a file system\ndirectory.
Returns true
if the <fs.Dirent> object describes a first-in-first-out\n(FIFO) pipe.
Returns true
if the <fs.Dirent> object describes a regular file.
Returns true
if the <fs.Dirent> object describes a socket.
Returns true
if the <fs.Dirent> object describes a symbolic link.
The file name that this <fs.Dirent> object refers to. The type of this\nvalue is determined by the options.encoding
passed to fs.readdir()
or\nfs.readdirSync()
.
The path to the parent directory of the file this <fs.Dirent> object refers to.
" }, { "textRaw": "`path` {string}", "type": "string", "name": "path", "meta": { "added": [ "v20.1.0", "v18.17.0" ], "deprecated": [ "v21.5.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`dirent.parentPath`][] instead.", "desc": "Alias for dirent.parentPath
.
A successful call to fs.watch()
method will return a new <fs.FSWatcher>\nobject.
All <fs.FSWatcher> objects emit a 'change'
event whenever a specific watched\nfile is modified.
Emitted when something changes in a watched directory or file.\nSee more details in fs.watch()
.
The filename
argument may not be provided depending on operating system\nsupport. If filename
is provided, it will be provided as a <Buffer> if\nfs.watch()
is called with its encoding
option set to 'buffer'
, otherwise\nfilename
will be a UTF-8 string.
import { watch } from 'node:fs';\n// Example when handled through fs.watch() listener\nwatch('./tmp', { encoding: 'buffer' }, (eventType, filename) => {\n if (filename) {\n console.log(filename);\n // Prints: <Buffer ...>\n }\n});\n
"
},
{
"textRaw": "Event: `'close'`",
"type": "event",
"name": "close",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"params": [],
"desc": "Emitted when the watcher stops watching for changes. The closed\n<fs.FSWatcher> object is no longer usable in the event handler.
" }, { "textRaw": "Event: `'error'`", "type": "event", "name": "error", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "params": [ { "textRaw": "`error` {Error}", "name": "error", "type": "Error" } ], "desc": "Emitted when an error occurs while watching the file. The errored\n<fs.FSWatcher> object is no longer usable in the event handler.
" } ], "methods": [ { "textRaw": "`watcher.close()`", "type": "method", "name": "close", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Stop watching for changes on the given <fs.FSWatcher>. Once stopped, the\n<fs.FSWatcher> object is no longer usable.
" }, { "textRaw": "`watcher.ref()`", "type": "method", "name": "ref", "meta": { "added": [ "v14.3.0", "v12.20.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {fs.FSWatcher}", "name": "return", "type": "fs.FSWatcher" }, "params": [] } ], "desc": "When called, requests that the Node.js event loop not exit so long as the\n<fs.FSWatcher> is active. Calling watcher.ref()
multiple times will have\nno effect.
By default, all <fs.FSWatcher> objects are \"ref'ed\", making it normally\nunnecessary to call watcher.ref()
unless watcher.unref()
had been\ncalled previously.
When called, the active <fs.FSWatcher> object will not require the Node.js\nevent loop to remain active. If there is no other activity keeping the\nevent loop running, the process may exit before the <fs.FSWatcher> object's\ncallback is invoked. Calling watcher.unref()
multiple times will have\nno effect.
A successful call to fs.watchFile()
method will return a new <fs.StatWatcher>\nobject.
When called, requests that the Node.js event loop not exit so long as the\n<fs.StatWatcher> is active. Calling watcher.ref()
multiple times will have\nno effect.
By default, all <fs.StatWatcher> objects are \"ref'ed\", making it normally\nunnecessary to call watcher.ref()
unless watcher.unref()
had been\ncalled previously.
When called, the active <fs.StatWatcher> object will not require the Node.js\nevent loop to remain active. If there is no other activity keeping the\nevent loop running, the process may exit before the <fs.StatWatcher> object's\ncallback is invoked. Calling watcher.unref()
multiple times will have\nno effect.
Instances of <fs.ReadStream> are created and returned using the\nfs.createReadStream()
function.
Emitted when the <fs.ReadStream>'s underlying file descriptor has been closed.
" }, { "textRaw": "Event: `'open'`", "type": "event", "name": "open", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "params": [ { "textRaw": "`fd` {integer} Integer file descriptor used by the {fs.ReadStream}.", "name": "fd", "type": "integer", "desc": "Integer file descriptor used by the {fs.ReadStream}." } ], "desc": "Emitted when the <fs.ReadStream>'s file descriptor has been opened.
" }, { "textRaw": "Event: `'ready'`", "type": "event", "name": "ready", "meta": { "added": [ "v9.11.0" ], "changes": [] }, "params": [], "desc": "Emitted when the <fs.ReadStream> is ready to be used.
\nFires immediately after 'open'
.
The number of bytes that have been read so far.
" }, { "textRaw": "`path` {string|Buffer}", "type": "string|Buffer", "name": "path", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "The path to the file the stream is reading from as specified in the first\nargument to fs.createReadStream()
. If path
is passed as a string, then\nreadStream.path
will be a string. If path
is passed as a <Buffer>, then\nreadStream.path
will be a <Buffer>. If fd
is specified, then\nreadStream.path
will be undefined
.
This property is true
if the underlying file has not been opened yet,\ni.e. before the 'ready'
event is emitted.
A <fs.Stats> object provides information about a file.
\nObjects returned from fs.stat()
, fs.lstat()
, fs.fstat()
, and\ntheir synchronous counterparts are of this type.\nIf bigint
in the options
passed to those methods is true, the numeric values\nwill be bigint
instead of number
, and the object will contain additional\nnanosecond-precision properties suffixed with Ns
.
Stats {\n dev: 2114,\n ino: 48064969,\n mode: 33188,\n nlink: 1,\n uid: 85,\n gid: 100,\n rdev: 0,\n size: 527,\n blksize: 4096,\n blocks: 8,\n atimeMs: 1318289051000.1,\n mtimeMs: 1318289051000.1,\n ctimeMs: 1318289051000.1,\n birthtimeMs: 1318289051000.1,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT }\n
\nbigint
version:
BigIntStats {\n dev: 2114n,\n ino: 48064969n,\n mode: 33188n,\n nlink: 1n,\n uid: 85n,\n gid: 100n,\n rdev: 0n,\n size: 527n,\n blksize: 4096n,\n blocks: 8n,\n atimeMs: 1318289051000n,\n mtimeMs: 1318289051000n,\n ctimeMs: 1318289051000n,\n birthtimeMs: 1318289051000n,\n atimeNs: 1318289051000000000n,\n mtimeNs: 1318289051000000000n,\n ctimeNs: 1318289051000000000n,\n birthtimeNs: 1318289051000000000n,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT }\n
",
"methods": [
{
"textRaw": "`stats.isBlockDevice()`",
"type": "method",
"name": "isBlockDevice",
"meta": {
"added": [
"v0.1.10"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": []
}
],
"desc": "Returns true
if the <fs.Stats> object describes a block device.
Returns true
if the <fs.Stats> object describes a character device.
Returns true
if the <fs.Stats> object describes a file system directory.
If the <fs.Stats> object was obtained from calling fs.lstat()
on a\nsymbolic link which resolves to a directory, this method will return false
.\nThis is because fs.lstat()
returns information\nabout a symbolic link itself and not the path it resolves to.
Returns true
if the <fs.Stats> object describes a first-in-first-out (FIFO)\npipe.
Returns true
if the <fs.Stats> object describes a regular file.
Returns true
if the <fs.Stats> object describes a socket.
Returns true
if the <fs.Stats> object describes a symbolic link.
This method is only valid when using fs.lstat()
.
The numeric identifier of the device containing the file.
" }, { "textRaw": "`ino` {number|bigint}", "type": "number|bigint", "name": "ino", "desc": "The file system specific \"Inode\" number for the file.
" }, { "textRaw": "`mode` {number|bigint}", "type": "number|bigint", "name": "mode", "desc": "A bit-field describing the file type and mode.
" }, { "textRaw": "`nlink` {number|bigint}", "type": "number|bigint", "name": "nlink", "desc": "The number of hard-links that exist for the file.
" }, { "textRaw": "`uid` {number|bigint}", "type": "number|bigint", "name": "uid", "desc": "The numeric user identifier of the user that owns the file (POSIX).
" }, { "textRaw": "`gid` {number|bigint}", "type": "number|bigint", "name": "gid", "desc": "The numeric group identifier of the group that owns the file (POSIX).
" }, { "textRaw": "`rdev` {number|bigint}", "type": "number|bigint", "name": "rdev", "desc": "A numeric device identifier if the file represents a device.
" }, { "textRaw": "`size` {number|bigint}", "type": "number|bigint", "name": "size", "desc": "The size of the file in bytes.
\nIf the underlying file system does not support getting the size of the file,\nthis will be 0
.
The file system block size for i/o operations.
" }, { "textRaw": "`blocks` {number|bigint}", "type": "number|bigint", "name": "blocks", "desc": "The number of blocks allocated for this file.
" }, { "textRaw": "`atimeMs` {number|bigint}", "type": "number|bigint", "name": "atimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was accessed expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`mtimeMs` {number|bigint}", "type": "number|bigint", "name": "mtimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was modified expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`ctimeMs` {number|bigint}", "type": "number|bigint", "name": "ctimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time the file status was changed expressed\nin milliseconds since the POSIX Epoch.
" }, { "textRaw": "`birthtimeMs` {number|bigint}", "type": "number|bigint", "name": "birthtimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the creation time of this file expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`atimeNs` {bigint}", "type": "bigint", "name": "atimeNs", "meta": { "added": [ "v12.10.0" ], "changes": [] }, "desc": "Only present when bigint: true
is passed into the method that generates\nthe object.\nThe timestamp indicating the last time this file was accessed expressed in\nnanoseconds since the POSIX Epoch.
Only present when bigint: true
is passed into the method that generates\nthe object.\nThe timestamp indicating the last time this file was modified expressed in\nnanoseconds since the POSIX Epoch.
Only present when bigint: true
is passed into the method that generates\nthe object.\nThe timestamp indicating the last time the file status was changed expressed\nin nanoseconds since the POSIX Epoch.
Only present when bigint: true
is passed into the method that generates\nthe object.\nThe timestamp indicating the creation time of this file expressed in\nnanoseconds since the POSIX Epoch.
The timestamp indicating the last time this file was accessed.
" }, { "textRaw": "`mtime` {Date}", "type": "Date", "name": "mtime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was modified.
" }, { "textRaw": "`ctime` {Date}", "type": "Date", "name": "ctime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time the file status was changed.
" }, { "textRaw": "`birthtime` {Date}", "type": "Date", "name": "birthtime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the creation time of this file.
" } ], "modules": [ { "textRaw": "Stat time values", "name": "stat_time_values", "desc": "The atimeMs
, mtimeMs
, ctimeMs
, birthtimeMs
properties are\nnumeric values that hold the corresponding times in milliseconds. Their\nprecision is platform specific. When bigint: true
is passed into the\nmethod that generates the object, the properties will be bigints,\notherwise they will be numbers.
The atimeNs
, mtimeNs
, ctimeNs
, birthtimeNs
properties are\nbigints that hold the corresponding times in nanoseconds. They are\nonly present when bigint: true
is passed into the method that generates\nthe object. Their precision is platform specific.
atime
, mtime
, ctime
, and birthtime
are\nDate
object alternate representations of the various times. The\nDate
and number values are not connected. Assigning a new number value, or\nmutating the Date
value, will not be reflected in the corresponding alternate\nrepresentation.
The times in the stat object have the following semantics:
\natime
\"Access Time\": Time when file data last accessed. Changed\nby the mknod(2)
, utimes(2)
, and read(2)
system calls.mtime
\"Modified Time\": Time when file data last modified.\nChanged by the mknod(2)
, utimes(2)
, and write(2)
system calls.ctime
\"Change Time\": Time when file status was last changed\n(inode data modification). Changed by the chmod(2)
, chown(2)
,\nlink(2)
, mknod(2)
, rename(2)
, unlink(2)
, utimes(2)
,\nread(2)
, and write(2)
system calls.birthtime
\"Birth Time\": Time of file creation. Set once when the\nfile is created. On file systems where birthtime is not available,\nthis field may instead hold either the ctime
or\n1970-01-01T00:00Z
(ie, Unix epoch timestamp 0
). This value may be greater\nthan atime
or mtime
in this case. On Darwin and other FreeBSD variants,\nalso set if the atime
is explicitly set to an earlier value than the current\nbirthtime
using the utimes(2)
system call.Prior to Node.js 0.12, the ctime
held the birthtime
on Windows systems. As\nof 0.12, ctime
is not \"creation time\", and on Unix systems, it never was.
Provides information about a mounted file system.
\nObjects returned from fs.statfs()
and its synchronous counterpart are of\nthis type. If bigint
in the options
passed to those methods is true
, the\nnumeric values will be bigint
instead of number
.
StatFs {\n type: 1397114950,\n bsize: 4096,\n blocks: 121938943,\n bfree: 61058895,\n bavail: 61058895,\n files: 999,\n ffree: 1000000\n}\n
\nbigint
version:
StatFs {\n type: 1397114950n,\n bsize: 4096n,\n blocks: 121938943n,\n bfree: 61058895n,\n bavail: 61058895n,\n files: 999n,\n ffree: 1000000n\n}\n
",
"properties": [
{
"textRaw": "`bavail` {number|bigint}",
"type": "number|bigint",
"name": "bavail",
"meta": {
"added": [
"v19.6.0",
"v18.15.0"
],
"changes": []
},
"desc": "Free blocks available to unprivileged users.
" }, { "textRaw": "`bfree` {number|bigint}", "type": "number|bigint", "name": "bfree", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "Free blocks in file system.
" }, { "textRaw": "`blocks` {number|bigint}", "type": "number|bigint", "name": "blocks", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "Total data blocks in file system.
" }, { "textRaw": "`bsize` {number|bigint}", "type": "number|bigint", "name": "bsize", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "Optimal transfer block size.
" }, { "textRaw": "`ffree` {number|bigint}", "type": "number|bigint", "name": "ffree", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "Free file nodes in file system.
" }, { "textRaw": "`files` {number|bigint}", "type": "number|bigint", "name": "files", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "Total file nodes in file system.
" }, { "textRaw": "`type` {number|bigint}", "type": "number|bigint", "name": "type", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "Type of file system.
" } ] }, { "textRaw": "Class: `fs.WriteStream`", "type": "class", "name": "fs.WriteStream", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "Instances of <fs.WriteStream> are created and returned using the\nfs.createWriteStream()
function.
Emitted when the <fs.WriteStream>'s underlying file descriptor has been closed.
" }, { "textRaw": "Event: `'open'`", "type": "event", "name": "open", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "params": [ { "textRaw": "`fd` {integer} Integer file descriptor used by the {fs.WriteStream}.", "name": "fd", "type": "integer", "desc": "Integer file descriptor used by the {fs.WriteStream}." } ], "desc": "Emitted when the <fs.WriteStream>'s file is opened.
" }, { "textRaw": "Event: `'ready'`", "type": "event", "name": "ready", "meta": { "added": [ "v9.11.0" ], "changes": [] }, "params": [], "desc": "Emitted when the <fs.WriteStream> is ready to be used.
\nFires immediately after 'open'
.
The number of bytes written so far. Does not include data that is still queued\nfor writing.
" }, { "textRaw": "`writeStream.path`", "name": "path", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "The path to the file the stream is writing to as specified in the first\nargument to fs.createWriteStream()
. If path
is passed as a string, then\nwriteStream.path
will be a string. If path
is passed as a <Buffer>, then\nwriteStream.path
will be a <Buffer>.
This property is true
if the underlying file has not been opened yet,\ni.e. before the 'ready'
event is emitted.
Closes writeStream
. Optionally accepts a\ncallback that will be executed once the writeStream
\nis closed.
Returns an object containing commonly used constants for file system\noperations.
", "modules": [ { "textRaw": "FS constants", "name": "fs_constants", "desc": "The following constants are exported by fs.constants
and fsPromises.constants
.
Not every constant will be available on every operating system;\nthis is especially important for Windows, where many of the POSIX specific\ndefinitions are not available.\nFor portable applications it is recommended to check for their presence\nbefore use.
\nTo use more than one constant, use the bitwise OR |
operator.
Example:
\nimport { open, constants } from 'node:fs';\n\nconst {\n O_RDWR,\n O_CREAT,\n O_EXCL,\n} = constants;\n\nopen('/path/to/my/file', O_RDWR | O_CREAT | O_EXCL, (err, fd) => {\n // ...\n});\n
",
"modules": [
{
"textRaw": "File access constants",
"name": "file_access_constants",
"desc": "The following constants are meant for use as the mode
parameter passed to\nfsPromises.access()
, fs.access()
, and fs.accessSync()
.
Constant | \nDescription | \n
---|---|
F_OK | \n Flag indicating that the file is visible to the calling process.\n This is useful for determining if a file exists, but says nothing\n about rwx permissions. Default if no mode is specified. | \n
R_OK | \n Flag indicating that the file can be read by the calling process. | \n
W_OK | \n Flag indicating that the file can be written by the calling\n process. | \n
X_OK | \n Flag indicating that the file can be executed by the calling\n process. This has no effect on Windows\n (will behave like fs.constants.F_OK ). | \n
The definitions are also available on Windows.
", "type": "module", "displayName": "File access constants" }, { "textRaw": "File copy constants", "name": "file_copy_constants", "desc": "The following constants are meant for use with fs.copyFile()
.
Constant | \nDescription | \n
---|---|
COPYFILE_EXCL | \n If present, the copy operation will fail with an error if the\n destination path already exists. | \n
COPYFILE_FICLONE | \n If present, the copy operation will attempt to create a\n copy-on-write reflink. If the underlying platform does not support\n copy-on-write, then a fallback copy mechanism is used. | \n
COPYFILE_FICLONE_FORCE | \n If present, the copy operation will attempt to create a\n copy-on-write reflink. If the underlying platform does not support\n copy-on-write, then the operation will fail with an error. | \n
The definitions are also available on Windows.
", "type": "module", "displayName": "File copy constants" }, { "textRaw": "File open constants", "name": "file_open_constants", "desc": "The following constants are meant for use with fs.open()
.
Constant | \nDescription | \n
---|---|
O_RDONLY | \n Flag indicating to open a file for read-only access. | \n
O_WRONLY | \n Flag indicating to open a file for write-only access. | \n
O_RDWR | \n Flag indicating to open a file for read-write access. | \n
O_CREAT | \n Flag indicating to create the file if it does not already exist. | \n
O_EXCL | \n Flag indicating that opening a file should fail if the\n O_CREAT flag is set and the file already exists. | \n
O_NOCTTY | \n Flag indicating that if path identifies a terminal device, opening the\n path shall not cause that terminal to become the controlling terminal for\n the process (if the process does not already have one). | \n
O_TRUNC | \n Flag indicating that if the file exists and is a regular file, and the\n file is opened successfully for write access, its length shall be truncated\n to zero. | \n
O_APPEND | \n Flag indicating that data will be appended to the end of the file. | \n
O_DIRECTORY | \n Flag indicating that the open should fail if the path is not a\n directory. | \n
O_NOATIME | \n Flag indicating reading accesses to the file system will no longer\n result in an update to the atime information associated with\n the file. This flag is available on Linux operating systems only. | \n
O_NOFOLLOW | \n Flag indicating that the open should fail if the path is a symbolic\n link. | \n
O_SYNC | \n Flag indicating that the file is opened for synchronized I/O with write\n operations waiting for file integrity. | \n
O_DSYNC | \n Flag indicating that the file is opened for synchronized I/O with write\n operations waiting for data integrity. | \n
O_SYMLINK | \n Flag indicating to open the symbolic link itself rather than the\n resource it is pointing to. | \n
O_DIRECT | \n When set, an attempt will be made to minimize caching effects of file\n I/O. | \n
O_NONBLOCK | \n Flag indicating to open the file in nonblocking mode when possible. | \n
UV_FS_O_FILEMAP | \n When set, a memory file mapping is used to access the file. This flag\n is available on Windows operating systems only. On other operating systems,\n this flag is ignored. | \n
On Windows, only O_APPEND
, O_CREAT
, O_EXCL
, O_RDONLY
, O_RDWR
,\nO_TRUNC
, O_WRONLY
, and UV_FS_O_FILEMAP
are available.
The following constants are meant for use with the <fs.Stats> object's\nmode
property for determining a file's type.
Constant | \nDescription | \n
---|---|
S_IFMT | \n Bit mask used to extract the file type code. | \n
S_IFREG | \n File type constant for a regular file. | \n
S_IFDIR | \n File type constant for a directory. | \n
S_IFCHR | \n File type constant for a character-oriented device file. | \n
S_IFBLK | \n File type constant for a block-oriented device file. | \n
S_IFIFO | \n File type constant for a FIFO/pipe. | \n
S_IFLNK | \n File type constant for a symbolic link. | \n
S_IFSOCK | \n File type constant for a socket. | \n
On Windows, only S_IFCHR
, S_IFDIR
, S_IFLNK
, S_IFMT
, and S_IFREG
,\nare available.
The following constants are meant for use with the <fs.Stats> object's\nmode
property for determining the access permissions for a file.
Constant | \nDescription | \n
---|---|
S_IRWXU | \n File mode indicating readable, writable, and executable by owner. | \n
S_IRUSR | \n File mode indicating readable by owner. | \n
S_IWUSR | \n File mode indicating writable by owner. | \n
S_IXUSR | \n File mode indicating executable by owner. | \n
S_IRWXG | \n File mode indicating readable, writable, and executable by group. | \n
S_IRGRP | \n File mode indicating readable by group. | \n
S_IWGRP | \n File mode indicating writable by group. | \n
S_IXGRP | \n File mode indicating executable by group. | \n
S_IRWXO | \n File mode indicating readable, writable, and executable by others. | \n
S_IROTH | \n File mode indicating readable by others. | \n
S_IWOTH | \n File mode indicating writable by others. | \n
S_IXOTH | \n File mode indicating executable by others. | \n
On Windows, only S_IRUSR
and S_IWUSR
are available.
Because they are executed asynchronously by the underlying thread pool,\nthere is no guaranteed ordering when using either the callback or\npromise-based methods.
\nFor example, the following is prone to error because the fs.stat()
\noperation might complete before the fs.rename()
operation:
const fs = require('node:fs');\n\nfs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n console.log('renamed complete');\n});\nfs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n});\n
\nIt is important to correctly order the operations by awaiting the results\nof one before invoking the other:
\nimport { rename, stat } from 'node:fs/promises';\n\nconst oldPath = '/tmp/hello';\nconst newPath = '/tmp/world';\n\ntry {\n await rename(oldPath, newPath);\n const stats = await stat(newPath);\n console.log(`stats: ${JSON.stringify(stats)}`);\n} catch (error) {\n console.error('there was an error:', error.message);\n}\n
\nconst { rename, stat } = require('node:fs/promises');\n\n(async function(oldPath, newPath) {\n try {\n await rename(oldPath, newPath);\n const stats = await stat(newPath);\n console.log(`stats: ${JSON.stringify(stats)}`);\n } catch (error) {\n console.error('there was an error:', error.message);\n }\n})('/tmp/hello', '/tmp/world');\n
\nOr, when using the callback APIs, move the fs.stat()
call into the callback\nof the fs.rename()
operation:
import { rename, stat } from 'node:fs';\n\nrename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n });\n});\n
\nconst { rename, stat } = require('node:fs/promises');\n\nrename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n });\n});\n
",
"type": "module",
"displayName": "Ordering of callback and promise-based operations"
},
{
"textRaw": "File paths",
"name": "file_paths",
"desc": "Most fs
operations accept file paths that may be specified in the form of\na string, a <Buffer>, or a <URL> object using the file:
protocol.
String paths are interpreted as UTF-8 character sequences identifying\nthe absolute or relative filename. Relative paths will be resolved relative\nto the current working directory as determined by calling process.cwd()
.
Example using an absolute path on POSIX:
\nimport { open } from 'node:fs/promises';\n\nlet fd;\ntry {\n fd = await open('/open/some/file.txt', 'r');\n // Do something with the file\n} finally {\n await fd?.close();\n}\n
\nExample using a relative path on POSIX (relative to process.cwd()
):
import { open } from 'node:fs/promises';\n\nlet fd;\ntry {\n fd = await open('file.txt', 'r');\n // Do something with the file\n} finally {\n await fd?.close();\n}\n
",
"type": "module",
"displayName": "String paths"
},
{
"textRaw": "File URL paths",
"name": "file_url_paths",
"meta": {
"added": [
"v7.6.0"
],
"changes": []
},
"desc": "For most node:fs
module functions, the path
or filename
argument may be\npassed as a <URL> object using the file:
protocol.
import { readFileSync } from 'node:fs';\n\nreadFileSync(new URL('file:///tmp/hello'));\n
\nfile:
URLs are always absolute paths.
On Windows, file:
<URL>s with a host name convert to UNC paths, while file:
\n<URL>s with drive letters convert to local absolute paths. file:
<URL>s\nwith no host name and no drive letter will result in an error:
import { readFileSync } from 'node:fs';\n// On Windows :\n\n// - WHATWG file URLs with hostname convert to UNC path\n// file://hostname/p/a/t/h/file => \\\\hostname\\p\\a\\t\\h\\file\nreadFileSync(new URL('file://hostname/p/a/t/h/file'));\n\n// - WHATWG file URLs with drive letters convert to absolute path\n// file:///C:/tmp/hello => C:\\tmp\\hello\nreadFileSync(new URL('file:///C:/tmp/hello'));\n\n// - WHATWG file URLs without hostname must have a drive letters\nreadFileSync(new URL('file:///notdriveletter/p/a/t/h/file'));\nreadFileSync(new URL('file:///c/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must be absolute\n
\nfile:
<URL>s with drive letters must use :
as a separator just after\nthe drive letter. Using another separator will result in an error.
On all other platforms, file:
<URL>s with a host name are unsupported and\nwill result in an error:
import { readFileSync } from 'node:fs';\n// On other platforms:\n\n// - WHATWG file URLs with hostname are unsupported\n// file://hostname/p/a/t/h/file => throw!\nreadFileSync(new URL('file://hostname/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: must be absolute\n\n// - WHATWG file URLs convert to absolute path\n// file:///tmp/hello => /tmp/hello\nreadFileSync(new URL('file:///tmp/hello'));\n
\nA file:
<URL> having encoded slash characters will result in an error on all\nplatforms:
import { readFileSync } from 'node:fs';\n\n// On Windows\nreadFileSync(new URL('file:///C:/p/a/t/h/%2F'));\nreadFileSync(new URL('file:///C:/p/a/t/h/%2f'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n\\ or / characters */\n\n// On POSIX\nreadFileSync(new URL('file:///p/a/t/h/%2F'));\nreadFileSync(new URL('file:///p/a/t/h/%2f'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n/ characters */\n
\nOn Windows, file:
<URL>s having encoded backslash will result in an error:
import { readFileSync } from 'node:fs';\n\n// On Windows\nreadFileSync(new URL('file:///C:/path/%5C'));\nreadFileSync(new URL('file:///C:/path/%5c'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n\\ or / characters */\n
",
"type": "module",
"displayName": "Platform-specific considerations"
}
],
"type": "module",
"displayName": "File URL paths"
},
{
"textRaw": "Buffer paths",
"name": "buffer_paths",
"desc": "Paths specified using a <Buffer> are useful primarily on certain POSIX\noperating systems that treat file paths as opaque byte sequences. On such\nsystems, it is possible for a single file path to contain sub-sequences that\nuse multiple character encodings. As with string paths, <Buffer> paths may\nbe relative or absolute:
\nExample using an absolute path on POSIX:
\nimport { open } from 'node:fs/promises';\nimport { Buffer } from 'node:buffer';\n\nlet fd;\ntry {\n fd = await open(Buffer.from('/open/some/file.txt'), 'r');\n // Do something with the file\n} finally {\n await fd?.close();\n}\n
",
"type": "module",
"displayName": "Buffer paths"
},
{
"textRaw": "Per-drive working directories on Windows",
"name": "per-drive_working_directories_on_windows",
"desc": "On Windows, Node.js follows the concept of per-drive working directory. This\nbehavior can be observed when using a drive path without a backslash. For\nexample fs.readdirSync('C:\\\\')
can potentially return a different result than\nfs.readdirSync('C:')
. For more information, see\nthis MSDN page.
On POSIX systems, for every process, the kernel maintains a table of currently\nopen files and resources. Each open file is assigned a simple numeric\nidentifier called a file descriptor. At the system-level, all file system\noperations use these file descriptors to identify and track each specific\nfile. Windows systems use a different but conceptually similar mechanism for\ntracking resources. To simplify things for users, Node.js abstracts away the\ndifferences between operating systems and assigns all open files a numeric file\ndescriptor.
\nThe callback-based fs.open()
, and synchronous fs.openSync()
methods open a\nfile and allocate a new file descriptor. Once allocated, the file descriptor may\nbe used to read data from, write data to, or request information about the file.
Operating systems limit the number of file descriptors that may be open\nat any given time so it is critical to close the descriptor when operations\nare completed. Failure to do so will result in a memory leak that will\neventually cause an application to crash.
\nimport { open, close, fstat } from 'node:fs';\n\nfunction closeFd(fd) {\n close(fd, (err) => {\n if (err) throw err;\n });\n}\n\nopen('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n try {\n fstat(fd, (err, stat) => {\n if (err) {\n closeFd(fd);\n throw err;\n }\n\n // use stat\n\n closeFd(fd);\n });\n } catch (err) {\n closeFd(fd);\n throw err;\n }\n});\n
\nThe promise-based APIs use a <FileHandle> object in place of the numeric\nfile descriptor. These objects are better managed by the system to ensure\nthat resources are not leaked. However, it is still required that they are\nclosed when operations are completed:
\nimport { open } from 'node:fs/promises';\n\nlet file;\ntry {\n file = await open('/open/some/file.txt', 'r');\n const stat = await file.stat();\n // use stat\n} finally {\n await file.close();\n}\n
",
"type": "module",
"displayName": "File descriptors"
},
{
"textRaw": "Threadpool usage",
"name": "threadpool_usage",
"desc": "All callback and promise-based file system APIs (with the exception of\nfs.FSWatcher()
) use libuv's threadpool. This can have surprising and negative\nperformance implications for some applications. See the\nUV_THREADPOOL_SIZE
documentation for more information.
The following flags are available wherever the flag
option takes a\nstring.
'a'
: Open file for appending.\nThe file is created if it does not exist.
'ax'
: Like 'a'
but fails if the path exists.
'a+'
: Open file for reading and appending.\nThe file is created if it does not exist.
'ax+'
: Like 'a+'
but fails if the path exists.
'as'
: Open file for appending in synchronous mode.\nThe file is created if it does not exist.
'as+'
: Open file for reading and appending in synchronous mode.\nThe file is created if it does not exist.
'r'
: Open file for reading.\nAn exception occurs if the file does not exist.
'rs'
: Open file for reading in synchronous mode.\nAn exception occurs if the file does not exist.
'r+'
: Open file for reading and writing.\nAn exception occurs if the file does not exist.
'rs+'
: Open file for reading and writing in synchronous mode. Instructs\nthe operating system to bypass the local file system cache.
This is primarily useful for opening files on NFS mounts as it allows\nskipping the potentially stale local cache. It has a very real impact on\nI/O performance so using this flag is not recommended unless it is needed.
\nThis doesn't turn fs.open()
or fsPromises.open()
into a synchronous\nblocking call. If synchronous operation is desired, something like\nfs.openSync()
should be used.
'w'
: Open file for writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx'
: Like 'w'
but fails if the path exists.
'w+'
: Open file for reading and writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx+'
: Like 'w+'
but fails if the path exists.
flag
can also be a number as documented by open(2)
; commonly used constants\nare available from fs.constants
. On Windows, flags are translated to\ntheir equivalent ones where applicable, e.g. O_WRONLY
to FILE_GENERIC_WRITE
,\nor O_EXCL|O_CREAT
to CREATE_NEW
, as accepted by CreateFileW
.
The exclusive flag 'x'
(O_EXCL
flag in open(2)
) causes the operation to\nreturn an error if the path already exists. On POSIX, if the path is a symbolic\nlink, using O_EXCL
returns an error even if the link is to a path that does\nnot exist. The exclusive flag might not work with network file systems.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
\nModifying a file rather than replacing it may require the flag
option to be\nset to 'r+'
rather than the default 'w'
.
The behavior of some flags are platform-specific. As such, opening a directory\non macOS and Linux with the 'a+'
flag, as in the example below, will return an\nerror. In contrast, on Windows and FreeBSD, a file descriptor or a FileHandle
\nwill be returned.
// macOS and Linux\nfs.open('<directory>', 'a+', (err, fd) => {\n // => [Error: EISDIR: illegal operation on a directory, open <directory>]\n});\n\n// Windows and FreeBSD\nfs.open('<directory>', 'a+', (err, fd) => {\n // => null, <fd>\n});\n
\nOn Windows, opening an existing hidden file using the 'w'
flag (either\nthrough fs.open()
, fs.writeFile()
, or fsPromises.open()
) will fail with\nEPERM
. Existing hidden files can be opened for writing with the 'r+'
flag.
A call to fs.ftruncate()
or filehandle.truncate()
can be used to reset\nthe file contents.
Source Code: lib/http.js
\nTo use the HTTP server and client one must require('node:http')
.
The HTTP interfaces in Node.js are designed to support many features\nof the protocol which have been traditionally difficult to use.\nIn particular, large, possibly chunk-encoded, messages. The interface is\ncareful to never buffer entire requests or responses, so the\nuser is able to stream data.
\nHTTP message headers are represented by an object like this:
\n{ \"content-length\": \"123\",\n \"content-type\": \"text/plain\",\n \"connection\": \"keep-alive\",\n \"host\": \"example.com\",\n \"accept\": \"*/*\" }\n
\nKeys are lowercased. Values are not modified.
\nIn order to support the full spectrum of possible HTTP applications, the Node.js\nHTTP API is very low-level. It deals with stream handling and message\nparsing only. It parses a message into headers and body but it does not\nparse the actual headers or the body.
\nSee message.headers
for details on how duplicate headers are handled.
The raw headers as they were received are retained in the rawHeaders
\nproperty, which is an array of [key, value, key2, value2, ...]
. For\nexample, the previous message header object might have a rawHeaders
\nlist like the following:
[ 'ConTent-Length', '123456',\n 'content-LENGTH', '123',\n 'content-type', 'text/plain',\n 'CONNECTION', 'keep-alive',\n 'Host', 'example.com',\n 'accepT', '*/*' ]\n
",
"classes": [
{
"textRaw": "Class: `http.Agent`",
"type": "class",
"name": "http.Agent",
"meta": {
"added": [
"v0.3.4"
],
"changes": []
},
"desc": "An Agent
is responsible for managing connection persistence\nand reuse for HTTP clients. It maintains a queue of pending requests\nfor a given host and port, reusing a single socket connection for each\nuntil the queue is empty, at which time the socket is either destroyed\nor put into a pool where it is kept to be used again for requests to the\nsame host and port. Whether it is destroyed or pooled depends on the\nkeepAlive
option.
Pooled connections have TCP Keep-Alive enabled for them, but servers may\nstill close idle connections, in which case they will be removed from the\npool and a new connection will be made when a new HTTP request is made for\nthat host and port. Servers may also refuse to allow multiple requests\nover the same connection, in which case the connection will have to be\nremade for every request and cannot be pooled. The Agent
will still make\nthe requests to that server, but each one will occur over a new connection.
When a connection is closed by the client or the server, it is removed\nfrom the pool. Any unused sockets in the pool will be unrefed so as not\nto keep the Node.js process running when there are no outstanding requests.\n(see socket.unref()
).
It is good practice, to destroy()
an Agent
instance when it is no\nlonger in use, because unused sockets consume OS resources.
Sockets are removed from an agent when the socket emits either\na 'close'
event or an 'agentRemove'
event. When intending to keep one\nHTTP request open for a long time without keeping it in the agent, something\nlike the following may be done:
http.get(options, (res) => {\n // Do stuff\n}).on('socket', (socket) => {\n socket.emit('agentRemove');\n});\n
\nAn agent may also be used for an individual request. By providing\n{agent: false}
as an option to the http.get()
or http.request()
\nfunctions, a one-time use Agent
with default options will be used\nfor the client connection.
agent:false
:
http.get({\n hostname: 'localhost',\n port: 80,\n path: '/',\n agent: false, // Create a new agent just for this one request\n}, (res) => {\n // Do stuff with response\n});\n
",
"methods": [
{
"textRaw": "`agent.createConnection(options[, callback])`",
"type": "method",
"name": "createConnection",
"meta": {
"added": [
"v0.11.4"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Duplex}",
"name": "return",
"type": "stream.Duplex"
},
"params": [
{
"textRaw": "`options` {Object} Options containing connection details. Check [`net.createConnection()`][] for the format of the options",
"name": "options",
"type": "Object",
"desc": "Options containing connection details. Check [`net.createConnection()`][] for the format of the options"
},
{
"textRaw": "`callback` {Function} Callback function that receives the created socket",
"name": "callback",
"type": "Function",
"desc": "Callback function that receives the created socket"
}
]
}
],
"desc": "Produces a socket/stream to be used for HTTP requests.
\nBy default, this function is the same as net.createConnection()
. However,\ncustom agents may override this method in case greater flexibility is desired.
A socket/stream can be supplied in one of two ways: by returning the\nsocket/stream from this function, or by passing the socket/stream to callback
.
This method is guaranteed to return an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
\ncallback
has a signature of (err, stream)
.
Called when socket
is detached from a request and could be persisted by the\nAgent
. Default behavior is to:
socket.setKeepAlive(true, this.keepAliveMsecs);\nsocket.unref();\nreturn true;\n
\nThis method can be overridden by a particular Agent
subclass. If this\nmethod returns a falsy value, the socket will be destroyed instead of persisting\nit for use with the next request.
The socket
argument can be an instance of <net.Socket>, a subclass of\n<stream.Duplex>.
Called when socket
is attached to request
after being persisted because of\nthe keep-alive options. Default behavior is to:
socket.ref();\n
\nThis method can be overridden by a particular Agent
subclass.
The socket
argument can be an instance of <net.Socket>, a subclass of\n<stream.Duplex>.
Destroy any sockets that are currently in use by the agent.
\nIt is usually not necessary to do this. However, if using an\nagent with keepAlive
enabled, then it is best to explicitly shut down\nthe agent when it is no longer needed. Otherwise,\nsockets might stay open for quite a long time before the server\nterminates them.
Get a unique name for a set of request options, to determine whether a\nconnection can be reused. For an HTTP agent, this returns\nhost:port:localAddress
or host:port:localAddress:family
. For an HTTPS agent,\nthe name includes the CA, cert, ciphers, and other HTTPS/TLS-specific options\nthat determine socket reusability.
An object which contains arrays of sockets currently awaiting use by\nthe agent when keepAlive
is enabled. Do not modify.
Sockets in the freeSockets
list will be automatically destroyed and\nremoved from the array on 'timeout'
.
By default set to 256. For agents with keepAlive
enabled, this\nsets the maximum number of sockets that will be left open in the free\nstate.
By default set to Infinity
. Determines how many concurrent sockets the agent\ncan have open per origin. Origin is the returned value of agent.getName()
.
By default set to Infinity
. Determines how many concurrent sockets the agent\ncan have open. Unlike maxSockets
, this parameter applies across all origins.
An object which contains queues of requests that have not yet been assigned to\nsockets. Do not modify.
" }, { "textRaw": "`sockets` {Object}", "type": "Object", "name": "sockets", "meta": { "added": [ "v0.3.6" ], "changes": [ { "version": "v16.0.0", "pr-url": "https://github.com/nodejs/node/pull/36409", "description": "The property now has a `null` prototype." } ] }, "desc": "An object which contains arrays of sockets currently in use by the\nagent. Do not modify.
" } ], "signatures": [ { "params": [ { "textRaw": "`options` {Object} Set of configurable options to set on the agent. Can have the following fields:", "name": "options", "type": "Object", "desc": "Set of configurable options to set on the agent. Can have the following fields:", "options": [ { "textRaw": "`keepAlive` {boolean} Keep sockets around even when there are no outstanding requests, so they can be used for future requests without having to reestablish a TCP connection. Not to be confused with the `keep-alive` value of the `Connection` header. The `Connection: keep-alive` header is always sent when using an agent except when the `Connection` header is explicitly specified or when the `keepAlive` and `maxSockets` options are respectively set to `false` and `Infinity`, in which case `Connection: close` will be used. **Default:** `false`.", "name": "keepAlive", "type": "boolean", "default": "`false`", "desc": "Keep sockets around even when there are no outstanding requests, so they can be used for future requests without having to reestablish a TCP connection. Not to be confused with the `keep-alive` value of the `Connection` header. The `Connection: keep-alive` header is always sent when using an agent except when the `Connection` header is explicitly specified or when the `keepAlive` and `maxSockets` options are respectively set to `false` and `Infinity`, in which case `Connection: close` will be used." }, { "textRaw": "`keepAliveMsecs` {number} When using the `keepAlive` option, specifies the [initial delay][] for TCP Keep-Alive packets. Ignored when the `keepAlive` option is `false` or `undefined`. **Default:** `1000`.", "name": "keepAliveMsecs", "type": "number", "default": "`1000`", "desc": "When using the `keepAlive` option, specifies the [initial delay][] for TCP Keep-Alive packets. Ignored when the `keepAlive` option is `false` or `undefined`." }, { "textRaw": "`maxSockets` {number} Maximum number of sockets to allow per host. If the same host opens multiple concurrent connections, each request will use new socket until the `maxSockets` value is reached. If the host attempts to open more connections than `maxSockets`, the additional requests will enter into a pending request queue, and will enter active connection state when an existing connection terminates. This makes sure there are at most `maxSockets` active connections at any point in time, from a given host. **Default:** `Infinity`.", "name": "maxSockets", "type": "number", "default": "`Infinity`", "desc": "Maximum number of sockets to allow per host. If the same host opens multiple concurrent connections, each request will use new socket until the `maxSockets` value is reached. If the host attempts to open more connections than `maxSockets`, the additional requests will enter into a pending request queue, and will enter active connection state when an existing connection terminates. This makes sure there are at most `maxSockets` active connections at any point in time, from a given host." }, { "textRaw": "`maxTotalSockets` {number} Maximum number of sockets allowed for all hosts in total. Each request will use a new socket until the maximum is reached. **Default:** `Infinity`.", "name": "maxTotalSockets", "type": "number", "default": "`Infinity`", "desc": "Maximum number of sockets allowed for all hosts in total. Each request will use a new socket until the maximum is reached." }, { "textRaw": "`maxFreeSockets` {number} Maximum number of sockets per host to leave open in a free state. Only relevant if `keepAlive` is set to `true`. **Default:** `256`.", "name": "maxFreeSockets", "type": "number", "default": "`256`", "desc": "Maximum number of sockets per host to leave open in a free state. Only relevant if `keepAlive` is set to `true`." }, { "textRaw": "`scheduling` {string} Scheduling strategy to apply when picking the next free socket to use. It can be `'fifo'` or `'lifo'`. The main difference between the two scheduling strategies is that `'lifo'` selects the most recently used socket, while `'fifo'` selects the least recently used socket. In case of a low rate of request per second, the `'lifo'` scheduling will lower the risk of picking a socket that might have been closed by the server due to inactivity. In case of a high rate of request per second, the `'fifo'` scheduling will maximize the number of open sockets, while the `'lifo'` scheduling will keep it as low as possible. **Default:** `'lifo'`.", "name": "scheduling", "type": "string", "default": "`'lifo'`", "desc": "Scheduling strategy to apply when picking the next free socket to use. It can be `'fifo'` or `'lifo'`. The main difference between the two scheduling strategies is that `'lifo'` selects the most recently used socket, while `'fifo'` selects the least recently used socket. In case of a low rate of request per second, the `'lifo'` scheduling will lower the risk of picking a socket that might have been closed by the server due to inactivity. In case of a high rate of request per second, the `'fifo'` scheduling will maximize the number of open sockets, while the `'lifo'` scheduling will keep it as low as possible." }, { "textRaw": "`timeout` {number} Socket timeout in milliseconds. This will set the timeout when the socket is created.", "name": "timeout", "type": "number", "desc": "Socket timeout in milliseconds. This will set the timeout when the socket is created." } ] } ], "desc": "options
in socket.connect()
are also supported.
The default http.globalAgent
that is used by http.request()
has all\nof these values set to their respective defaults.
To configure any of them, a custom http.Agent
instance must be created.
import { Agent, request } from 'node:http';\nconst keepAliveAgent = new Agent({ keepAlive: true });\noptions.agent = keepAliveAgent;\nrequest(options, onResponseCallback);\n
\nconst http = require('node:http');\nconst keepAliveAgent = new http.Agent({ keepAlive: true });\noptions.agent = keepAliveAgent;\nhttp.request(options, onResponseCallback);\n
"
}
]
},
{
"textRaw": "Class: `http.ClientRequest`",
"type": "class",
"name": "http.ClientRequest",
"meta": {
"added": [
"v0.1.17"
],
"changes": []
},
"desc": "This object is created internally and returned from http.request()
. It\nrepresents an in-progress request whose header has already been queued. The\nheader is still mutable using the setHeader(name, value)
,\ngetHeader(name)
, removeHeader(name)
API. The actual header will\nbe sent along with the first data chunk or when calling request.end()
.
To get the response, add a listener for 'response'
to the request object.\n'response'
will be emitted from the request object when the response\nheaders have been received. The 'response'
event is executed with one\nargument which is an instance of http.IncomingMessage
.
During the 'response'
event, one can add listeners to the\nresponse object; particularly to listen for the 'data'
event.
If no 'response'
handler is added, then the response will be\nentirely discarded. However, if a 'response'
event handler is added,\nthen the data from the response object must be consumed, either by\ncalling response.read()
whenever there is a 'readable'
event, or\nby adding a 'data'
handler, or by calling the .resume()
method.\nUntil the data is consumed, the 'end'
event will not fire. Also, until\nthe data is read it will consume memory that can eventually lead to a\n'process out of memory' error.
For backward compatibility, res
will only emit 'error'
if there is an\n'error'
listener registered.
Set Content-Length
header to limit the response body size.\nIf response.strictContentLength
is set to true
, mismatching the\nContent-Length
header value will result in an Error
being thrown,\nidentified by code:
'ERR_HTTP_CONTENT_LENGTH_MISMATCH'
.
Content-Length
value should be in bytes, not characters. Use\nBuffer.byteLength()
to determine the length of the body in bytes.
Emitted when the request has been aborted by the client. This event is only\nemitted on the first call to abort()
.
Indicates that the request is completed, or its underlying connection was\nterminated prematurely (before the response completion).
" }, { "textRaw": "Event: `'connect'`", "type": "event", "name": "connect", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "params": [ { "textRaw": "`response` {http.IncomingMessage}", "name": "response", "type": "http.IncomingMessage" }, { "textRaw": "`socket` {stream.Duplex}", "name": "socket", "type": "stream.Duplex" }, { "textRaw": "`head` {Buffer}", "name": "head", "type": "Buffer" } ], "desc": "Emitted each time a server responds to a request with a CONNECT
method. If\nthis event is not being listened for, clients receiving a CONNECT
method will\nhave their connections closed.
This event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
\nA client and server pair demonstrating how to listen for the 'connect'
event:
import { createServer, request } from 'node:http';\nimport { connect } from 'node:net';\nimport { URL } from 'node:url';\n\n// Create an HTTP tunneling proxy\nconst proxy = createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nproxy.on('connect', (req, clientSocket, head) => {\n // Connect to an origin server\n const { port, hostname } = new URL(`http://${req.url}`);\n const serverSocket = connect(port || 80, hostname, () => {\n clientSocket.write('HTTP/1.1 200 Connection Established\\r\\n' +\n 'Proxy-agent: Node.js-Proxy\\r\\n' +\n '\\r\\n');\n serverSocket.write(head);\n serverSocket.pipe(clientSocket);\n clientSocket.pipe(serverSocket);\n });\n});\n\n// Now that proxy is running\nproxy.listen(1337, '127.0.0.1', () => {\n\n // Make a request to a tunneling proxy\n const options = {\n port: 1337,\n host: '127.0.0.1',\n method: 'CONNECT',\n path: 'www.google.com:80',\n };\n\n const req = request(options);\n req.end();\n\n req.on('connect', (res, socket, head) => {\n console.log('got connected!');\n\n // Make a request over an HTTP tunnel\n socket.write('GET / HTTP/1.1\\r\\n' +\n 'Host: www.google.com:80\\r\\n' +\n 'Connection: close\\r\\n' +\n '\\r\\n');\n socket.on('data', (chunk) => {\n console.log(chunk.toString());\n });\n socket.on('end', () => {\n proxy.close();\n });\n });\n});\n
\nconst http = require('node:http');\nconst net = require('node:net');\nconst { URL } = require('node:url');\n\n// Create an HTTP tunneling proxy\nconst proxy = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nproxy.on('connect', (req, clientSocket, head) => {\n // Connect to an origin server\n const { port, hostname } = new URL(`http://${req.url}`);\n const serverSocket = net.connect(port || 80, hostname, () => {\n clientSocket.write('HTTP/1.1 200 Connection Established\\r\\n' +\n 'Proxy-agent: Node.js-Proxy\\r\\n' +\n '\\r\\n');\n serverSocket.write(head);\n serverSocket.pipe(clientSocket);\n clientSocket.pipe(serverSocket);\n });\n});\n\n// Now that proxy is running\nproxy.listen(1337, '127.0.0.1', () => {\n\n // Make a request to a tunneling proxy\n const options = {\n port: 1337,\n host: '127.0.0.1',\n method: 'CONNECT',\n path: 'www.google.com:80',\n };\n\n const req = http.request(options);\n req.end();\n\n req.on('connect', (res, socket, head) => {\n console.log('got connected!');\n\n // Make a request over an HTTP tunnel\n socket.write('GET / HTTP/1.1\\r\\n' +\n 'Host: www.google.com:80\\r\\n' +\n 'Connection: close\\r\\n' +\n '\\r\\n');\n socket.on('data', (chunk) => {\n console.log(chunk.toString());\n });\n socket.on('end', () => {\n proxy.close();\n });\n });\n});\n
"
},
{
"textRaw": "Event: `'continue'`",
"type": "event",
"name": "continue",
"meta": {
"added": [
"v0.3.2"
],
"changes": []
},
"params": [],
"desc": "Emitted when the server sends a '100 Continue' HTTP response, usually because\nthe request contained 'Expect: 100-continue'. This is an instruction that\nthe client should send the request body.
" }, { "textRaw": "Event: `'finish'`", "type": "event", "name": "finish", "meta": { "added": [ "v0.3.6" ], "changes": [] }, "params": [], "desc": "Emitted when the request has been sent. More specifically, this event is emitted\nwhen the last segment of the response headers and body have been handed off to\nthe operating system for transmission over the network. It does not imply that\nthe server has received anything yet.
" }, { "textRaw": "Event: `'information'`", "type": "event", "name": "information", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "params": [ { "textRaw": "`info` {Object}", "name": "info", "type": "Object", "options": [ { "textRaw": "`httpVersion` {string}", "name": "httpVersion", "type": "string" }, { "textRaw": "`httpVersionMajor` {integer}", "name": "httpVersionMajor", "type": "integer" }, { "textRaw": "`httpVersionMinor` {integer}", "name": "httpVersionMinor", "type": "integer" }, { "textRaw": "`statusCode` {integer}", "name": "statusCode", "type": "integer" }, { "textRaw": "`statusMessage` {string}", "name": "statusMessage", "type": "string" }, { "textRaw": "`headers` {Object}", "name": "headers", "type": "Object" }, { "textRaw": "`rawHeaders` {string\\[]}", "name": "rawHeaders", "type": "string\\[]" } ] } ], "desc": "Emitted when the server sends a 1xx intermediate response (excluding 101\nUpgrade). The listeners of this event will receive an object containing the\nHTTP version, status code, status message, key-value headers object,\nand array with the raw header names followed by their respective values.
\nimport { request } from 'node:http';\n\nconst options = {\n host: '127.0.0.1',\n port: 8080,\n path: '/length_request',\n};\n\n// Make a request\nconst req = request(options);\nreq.end();\n\nreq.on('information', (info) => {\n console.log(`Got information prior to main response: ${info.statusCode}`);\n});\n
\nconst http = require('node:http');\n\nconst options = {\n host: '127.0.0.1',\n port: 8080,\n path: '/length_request',\n};\n\n// Make a request\nconst req = http.request(options);\nreq.end();\n\nreq.on('information', (info) => {\n console.log(`Got information prior to main response: ${info.statusCode}`);\n});\n
\n101 Upgrade statuses do not fire this event due to their break from the\ntraditional HTTP request/response chain, such as web sockets, in-place TLS\nupgrades, or HTTP 2.0. To be notified of 101 Upgrade notices, listen for the\n'upgrade'
event instead.
Emitted when a response is received to this request. This event is emitted only\nonce.
" }, { "textRaw": "Event: `'socket'`", "type": "event", "name": "socket", "meta": { "added": [ "v0.5.3" ], "changes": [] }, "params": [ { "textRaw": "`socket` {stream.Duplex}", "name": "socket", "type": "stream.Duplex" } ], "desc": "This event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
" }, { "textRaw": "Event: `'timeout'`", "type": "event", "name": "timeout", "meta": { "added": [ "v0.7.8" ], "changes": [] }, "params": [], "desc": "Emitted when the underlying socket times out from inactivity. This only notifies\nthat the socket has been idle. The request must be destroyed manually.
\nSee also: request.setTimeout()
.
Emitted each time a server responds to a request with an upgrade. If this\nevent is not being listened for and the response status code is 101 Switching\nProtocols, clients receiving an upgrade header will have their connections\nclosed.
\nThis event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
\nA client server pair demonstrating how to listen for the 'upgrade'
event.
import http from 'node:http';\nimport process from 'node:process';\n\n// Create an HTTP server\nconst server = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nserver.on('upgrade', (req, socket, head) => {\n socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\\r\\n' +\n 'Upgrade: WebSocket\\r\\n' +\n 'Connection: Upgrade\\r\\n' +\n '\\r\\n');\n\n socket.pipe(socket); // echo back\n});\n\n// Now that server is running\nserver.listen(1337, '127.0.0.1', () => {\n\n // make a request\n const options = {\n port: 1337,\n host: '127.0.0.1',\n headers: {\n 'Connection': 'Upgrade',\n 'Upgrade': 'websocket',\n },\n };\n\n const req = http.request(options);\n req.end();\n\n req.on('upgrade', (res, socket, upgradeHead) => {\n console.log('got upgraded!');\n socket.end();\n process.exit(0);\n });\n});\n
\nconst http = require('node:http');\n\n// Create an HTTP server\nconst server = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nserver.on('upgrade', (req, socket, head) => {\n socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\\r\\n' +\n 'Upgrade: WebSocket\\r\\n' +\n 'Connection: Upgrade\\r\\n' +\n '\\r\\n');\n\n socket.pipe(socket); // echo back\n});\n\n// Now that server is running\nserver.listen(1337, '127.0.0.1', () => {\n\n // make a request\n const options = {\n port: 1337,\n host: '127.0.0.1',\n headers: {\n 'Connection': 'Upgrade',\n 'Upgrade': 'websocket',\n },\n };\n\n const req = http.request(options);\n req.end();\n\n req.on('upgrade', (res, socket, upgradeHead) => {\n console.log('got upgraded!');\n socket.end();\n process.exit(0);\n });\n});\n
"
}
],
"methods": [
{
"textRaw": "`request.abort()`",
"type": "method",
"name": "abort",
"meta": {
"added": [
"v0.3.8"
],
"deprecated": [
"v14.1.0",
"v13.14.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`request.destroy()`][] instead.",
"signatures": [
{
"params": []
}
],
"desc": "Marks the request as aborting. Calling this will cause remaining data\nin the response to be dropped and the socket to be destroyed.
" }, { "textRaw": "`request.cork()`", "type": "method", "name": "cork", "meta": { "added": [ "v13.2.0", "v12.16.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "See writable.cork()
.
Finishes sending the request. If any parts of the body are\nunsent, it will flush them to the stream. If the request is\nchunked, this will send the terminating '0\\r\\n\\r\\n'
.
If data
is specified, it is equivalent to calling\nrequest.write(data, encoding)
followed by request.end(callback)
.
If callback
is specified, it will be called when the request stream\nis finished.
Destroy the request. Optionally emit an 'error'
event,\nand emit a 'close'
event. Calling this will cause remaining data\nin the response to be dropped and the socket to be destroyed.
See writable.destroy()
for further details.
Is true
after request.destroy()
has been called.
See writable.destroyed
for further details.
Flushes the request headers.
\nFor efficiency reasons, Node.js normally buffers the request headers until\nrequest.end()
is called or the first chunk of request data is written. It\nthen tries to pack the request headers and data into a single TCP packet.
That's usually desired (it saves a TCP round-trip), but not when the first\ndata is not sent until possibly much later. request.flushHeaders()
bypasses\nthe optimization and kickstarts the request.
Reads out a header on the request. The name is case-insensitive.\nThe type of the return value depends on the arguments provided to\nrequest.setHeader()
.
request.setHeader('content-type', 'text/html');\nrequest.setHeader('Content-Length', Buffer.byteLength(body));\nrequest.setHeader('Cookie', ['type=ninja', 'language=javascript']);\nconst contentType = request.getHeader('Content-Type');\n// 'contentType' is 'text/html'\nconst contentLength = request.getHeader('Content-Length');\n// 'contentLength' is of type number\nconst cookie = request.getHeader('Cookie');\n// 'cookie' is of type string[]\n
"
},
{
"textRaw": "`request.getHeaderNames()`",
"type": "method",
"name": "getHeaderNames",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string\\[]}",
"name": "return",
"type": "string\\[]"
},
"params": []
}
],
"desc": "Returns an array containing the unique names of the current outgoing headers.\nAll header names are lowercase.
\nrequest.setHeader('Foo', 'bar');\nrequest.setHeader('Cookie', ['foo=bar', 'bar=baz']);\n\nconst headerNames = request.getHeaderNames();\n// headerNames === ['foo', 'cookie']\n
"
},
{
"textRaw": "`request.getHeaders()`",
"type": "method",
"name": "getHeaders",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Returns a shallow copy of the current outgoing headers. Since a shallow copy\nis used, array values may be mutated without additional calls to various\nheader-related http module methods. The keys of the returned object are the\nheader names and the values are the respective header values. All header names\nare lowercase.
\nThe object returned by the request.getHeaders()
method does not\nprototypically inherit from the JavaScript Object
. This means that typical\nObject
methods such as obj.toString()
, obj.hasOwnProperty()
, and others\nare not defined and will not work.
request.setHeader('Foo', 'bar');\nrequest.setHeader('Cookie', ['foo=bar', 'bar=baz']);\n\nconst headers = request.getHeaders();\n// headers === { foo: 'bar', 'cookie': ['foo=bar', 'bar=baz'] }\n
"
},
{
"textRaw": "`request.getRawHeaderNames()`",
"type": "method",
"name": "getRawHeaderNames",
"meta": {
"added": [
"v15.13.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string\\[]}",
"name": "return",
"type": "string\\[]"
},
"params": []
}
],
"desc": "Returns an array containing the unique names of the current outgoing raw\nheaders. Header names are returned with their exact casing being set.
\nrequest.setHeader('Foo', 'bar');\nrequest.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headerNames = request.getRawHeaderNames();\n// headerNames === ['Foo', 'Set-Cookie']\n
"
},
{
"textRaw": "`request.hasHeader(name)`",
"type": "method",
"name": "hasHeader",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Returns true
if the header identified by name
is currently set in the\noutgoing headers. The header name matching is case-insensitive.
const hasContentType = request.hasHeader('content-type');\n
"
},
{
"textRaw": "`request.removeHeader(name)`",
"type": "method",
"name": "removeHeader",
"meta": {
"added": [
"v1.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Removes a header that's already defined into headers object.
\nrequest.removeHeader('Content-Type');\n
"
},
{
"textRaw": "`request.setHeader(name, value)`",
"type": "method",
"name": "setHeader",
"meta": {
"added": [
"v1.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Sets a single header value for headers object. If this header already exists in\nthe to-be-sent headers, its value will be replaced. Use an array of strings\nhere to send multiple headers with the same name. Non-string values will be\nstored without modification. Therefore, request.getHeader()
may return\nnon-string values. However, the non-string values will be converted to strings\nfor network transmission.
request.setHeader('Content-Type', 'application/json');\n
\nor
\nrequest.setHeader('Cookie', ['type=ninja', 'language=javascript']);\n
\nWhen the value is a string an exception will be thrown if it contains\ncharacters outside the latin1
encoding.
If you need to pass UTF-8 characters in the value please encode the value\nusing the RFC 8187 standard.
\nconst filename = 'Rock 🎵.txt';\nrequest.setHeader('Content-Disposition', `attachment; filename*=utf-8''${encodeURIComponent(filename)}`);\n
"
},
{
"textRaw": "`request.setNoDelay([noDelay])`",
"type": "method",
"name": "setNoDelay",
"meta": {
"added": [
"v0.5.9"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`noDelay` {boolean}",
"name": "noDelay",
"type": "boolean"
}
]
}
],
"desc": "Once a socket is assigned to this request and is connected\nsocket.setNoDelay()
will be called.
Once a socket is assigned to this request and is connected\nsocket.setKeepAlive()
will be called.
Once a socket is assigned to this request and is connected\nsocket.setTimeout()
will be called.
See writable.uncork()
.
Sends a chunk of the body. This method can be called multiple times. If no\nContent-Length
is set, data will automatically be encoded in HTTP Chunked\ntransfer encoding, so that server knows when the data ends. The\nTransfer-Encoding: chunked
header is added. Calling request.end()
\nis necessary to finish sending the request.
The encoding
argument is optional and only applies when chunk
is a string.\nDefaults to 'utf8'
.
The callback
argument is optional and will be called when this chunk of data\nis flushed, but only if the chunk is non-empty.
Returns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in user memory.\n'drain'
will be emitted when the buffer is free again.
When write
function is called with empty string or buffer, it does\nnothing and waits for more input.
The request.aborted
property will be true
if the request has\nbeen aborted.
See request.socket
.
The request.finished
property will be true
if request.end()
\nhas been called. request.end()
will automatically be called if the\nrequest was initiated via http.get()
.
Limits maximum response headers count. If set to 0, no limit will be applied.
" }, { "textRaw": "`path` {string} The request path.", "type": "string", "name": "path", "meta": { "added": [ "v0.4.0" ], "changes": [] }, "desc": "The request path." }, { "textRaw": "`method` {string} The request method.", "type": "string", "name": "method", "meta": { "added": [ "v0.1.97" ], "changes": [] }, "desc": "The request method." }, { "textRaw": "`host` {string} The request host.", "type": "string", "name": "host", "meta": { "added": [ "v14.5.0", "v12.19.0" ], "changes": [] }, "desc": "The request host." }, { "textRaw": "`protocol` {string} The request protocol.", "type": "string", "name": "protocol", "meta": { "added": [ "v14.5.0", "v12.19.0" ], "changes": [] }, "desc": "The request protocol." }, { "textRaw": "`reusedSocket` {boolean} Whether the request is send through a reused socket.", "type": "boolean", "name": "reusedSocket", "meta": { "added": [ "v13.0.0", "v12.16.0" ], "changes": [] }, "desc": "When sending request through a keep-alive enabled agent, the underlying socket\nmight be reused. But if server closes connection at unfortunate time, client\nmay run into a 'ECONNRESET' error.
\nimport http from 'node:http';\n\n// Server has a 5 seconds keep-alive timeout by default\nhttp\n .createServer((req, res) => {\n res.write('hello\\n');\n res.end();\n })\n .listen(3000);\n\nsetInterval(() => {\n // Adapting a keep-alive agent\n http.get('http://localhost:3000', { agent }, (res) => {\n res.on('data', (data) => {\n // Do nothing\n });\n });\n}, 5000); // Sending request on 5s interval so it's easy to hit idle timeout\n
\nconst http = require('node:http');\n\n// Server has a 5 seconds keep-alive timeout by default\nhttp\n .createServer((req, res) => {\n res.write('hello\\n');\n res.end();\n })\n .listen(3000);\n\nsetInterval(() => {\n // Adapting a keep-alive agent\n http.get('http://localhost:3000', { agent }, (res) => {\n res.on('data', (data) => {\n // Do nothing\n });\n });\n}, 5000); // Sending request on 5s interval so it's easy to hit idle timeout\n
\nBy marking a request whether it reused socket or not, we can do\nautomatic error retry base on it.
\nimport http from 'node:http';\nconst agent = new http.Agent({ keepAlive: true });\n\nfunction retriableRequest() {\n const req = http\n .get('http://localhost:3000', { agent }, (res) => {\n // ...\n })\n .on('error', (err) => {\n // Check if retry is needed\n if (req.reusedSocket && err.code === 'ECONNRESET') {\n retriableRequest();\n }\n });\n}\n\nretriableRequest();\n
\nconst http = require('node:http');\nconst agent = new http.Agent({ keepAlive: true });\n\nfunction retriableRequest() {\n const req = http\n .get('http://localhost:3000', { agent }, (res) => {\n // ...\n })\n .on('error', (err) => {\n // Check if retry is needed\n if (req.reusedSocket && err.code === 'ECONNRESET') {\n retriableRequest();\n }\n });\n}\n\nretriableRequest();\n
",
"shortDesc": "Whether the request is send through a reused socket."
},
{
"textRaw": "`socket` {stream.Duplex}",
"type": "stream.Duplex",
"name": "socket",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"desc": "Reference to the underlying socket. Usually users will not want to access\nthis property. In particular, the socket will not emit 'readable'
events\nbecause of how the protocol parser attaches to the socket.
import http from 'node:http';\nconst options = {\n host: 'www.google.com',\n};\nconst req = http.get(options);\nreq.end();\nreq.once('response', (res) => {\n const ip = req.socket.localAddress;\n const port = req.socket.localPort;\n console.log(`Your IP address is ${ip} and your source port is ${port}.`);\n // Consume response object\n});\n
\nconst http = require('node:http');\nconst options = {\n host: 'www.google.com',\n};\nconst req = http.get(options);\nreq.end();\nreq.once('response', (res) => {\n const ip = req.socket.localAddress;\n const port = req.socket.localPort;\n console.log(`Your IP address is ${ip} and your source port is ${port}.`);\n // Consume response object\n});\n
\nThis property is guaranteed to be an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specified a socket\ntype other than <net.Socket>.
" }, { "textRaw": "`writableEnded` {boolean}", "type": "boolean", "name": "writableEnded", "meta": { "added": [ "v12.9.0" ], "changes": [] }, "desc": "Is true
after request.end()
has been called. This property\ndoes not indicate whether the data has been flushed, for this use\nrequest.writableFinished
instead.
Is true
if all data has been flushed to the underlying system, immediately\nbefore the 'finish'
event is emitted.
Emitted each time a request with an HTTP Expect: 100-continue
is received.\nIf this event is not listened for, the server will automatically respond\nwith a 100 Continue
as appropriate.
Handling this event involves calling response.writeContinue()
if the\nclient should continue to send the request body, or generating an appropriate\nHTTP response (e.g. 400 Bad Request) if the client should not continue to send\nthe request body.
When this event is emitted and handled, the 'request'
event will\nnot be emitted.
Emitted each time a request with an HTTP Expect
header is received, where the\nvalue is not 100-continue
. If this event is not listened for, the server will\nautomatically respond with a 417 Expectation Failed
as appropriate.
When this event is emitted and handled, the 'request'
event will\nnot be emitted.
If a client connection emits an 'error'
event, it will be forwarded here.\nListener of this event is responsible for closing/destroying the underlying\nsocket. For example, one may wish to more gracefully close the socket with a\ncustom HTTP response instead of abruptly severing the connection. The socket\nmust be closed or destroyed before the listener ends.
This event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
\nDefault behavior is to try close the socket with a HTTP '400 Bad Request',\nor a HTTP '431 Request Header Fields Too Large' in the case of a\nHPE_HEADER_OVERFLOW
error. If the socket is not writable or headers\nof the current attached http.ServerResponse
has been sent, it is\nimmediately destroyed.
socket
is the net.Socket
object that the error originated from.
import http from 'node:http';\n\nconst server = http.createServer((req, res) => {\n res.end();\n});\nserver.on('clientError', (err, socket) => {\n socket.end('HTTP/1.1 400 Bad Request\\r\\n\\r\\n');\n});\nserver.listen(8000);\n
\nconst http = require('node:http');\n\nconst server = http.createServer((req, res) => {\n res.end();\n});\nserver.on('clientError', (err, socket) => {\n socket.end('HTTP/1.1 400 Bad Request\\r\\n\\r\\n');\n});\nserver.listen(8000);\n
\nWhen the 'clientError'
event occurs, there is no request
or response
\nobject, so any HTTP response sent, including response headers and payload,\nmust be written directly to the socket
object. Care must be taken to\nensure the response is a properly formatted HTTP response message.
err
is an instance of Error
with two extra columns:
bytesParsed
: the bytes count of request packet that Node.js may have parsed\ncorrectly;rawPacket
: the raw packet of current request.In some cases, the client has already received the response and/or the socket\nhas already been destroyed, like in case of ECONNRESET
errors. Before\ntrying to send data to the socket, it is better to check that it is still\nwritable.
server.on('clientError', (err, socket) => {\n if (err.code === 'ECONNRESET' || !socket.writable) {\n return;\n }\n\n socket.end('HTTP/1.1 400 Bad Request\\r\\n\\r\\n');\n});\n
"
},
{
"textRaw": "Event: `'close'`",
"type": "event",
"name": "close",
"meta": {
"added": [
"v0.1.4"
],
"changes": []
},
"params": [],
"desc": "Emitted when the server closes.
" }, { "textRaw": "Event: `'connect'`", "type": "event", "name": "connect", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "params": [ { "textRaw": "`request` {http.IncomingMessage} Arguments for the HTTP request, as it is in the [`'request'`][] event", "name": "request", "type": "http.IncomingMessage", "desc": "Arguments for the HTTP request, as it is in the [`'request'`][] event" }, { "textRaw": "`socket` {stream.Duplex} Network socket between the server and client", "name": "socket", "type": "stream.Duplex", "desc": "Network socket between the server and client" }, { "textRaw": "`head` {Buffer} The first packet of the tunneling stream (may be empty)", "name": "head", "type": "Buffer", "desc": "The first packet of the tunneling stream (may be empty)" } ], "desc": "Emitted each time a client requests an HTTP CONNECT
method. If this event is\nnot listened for, then clients requesting a CONNECT
method will have their\nconnections closed.
This event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
\nAfter this event is emitted, the request's socket will not have a 'data'
\nevent listener, meaning it will need to be bound in order to handle data\nsent to the server on that socket.
This event is emitted when a new TCP stream is established. socket
is\ntypically an object of type net.Socket
. Usually users will not want to\naccess this event. In particular, the socket will not emit 'readable'
events\nbecause of how the protocol parser attaches to the socket. The socket
can\nalso be accessed at request.socket
.
This event can also be explicitly emitted by users to inject connections\ninto the HTTP server. In that case, any Duplex
stream can be passed.
If socket.setTimeout()
is called here, the timeout will be replaced with\nserver.keepAliveTimeout
when the socket has served a request (if\nserver.keepAliveTimeout
is non-zero).
This event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
" }, { "textRaw": "Event: `'dropRequest'`", "type": "event", "name": "dropRequest", "meta": { "added": [ "v18.7.0", "v16.17.0" ], "changes": [] }, "params": [ { "textRaw": "`request` {http.IncomingMessage} Arguments for the HTTP request, as it is in the [`'request'`][] event", "name": "request", "type": "http.IncomingMessage", "desc": "Arguments for the HTTP request, as it is in the [`'request'`][] event" }, { "textRaw": "`socket` {stream.Duplex} Network socket between the server and client", "name": "socket", "type": "stream.Duplex", "desc": "Network socket between the server and client" } ], "desc": "When the number of requests on a socket reaches the threshold of\nserver.maxRequestsPerSocket
, the server will drop new requests\nand emit 'dropRequest'
event instead, then send 503
to client.
Emitted each time there is a request. There may be multiple requests\nper connection (in the case of HTTP Keep-Alive connections).
" }, { "textRaw": "Event: `'upgrade'`", "type": "event", "name": "upgrade", "meta": { "added": [ "v0.1.94" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/19981", "description": "Not listening to this event no longer causes the socket to be destroyed if a client sends an Upgrade header." } ] }, "params": [ { "textRaw": "`request` {http.IncomingMessage} Arguments for the HTTP request, as it is in the [`'request'`][] event", "name": "request", "type": "http.IncomingMessage", "desc": "Arguments for the HTTP request, as it is in the [`'request'`][] event" }, { "textRaw": "`socket` {stream.Duplex} Network socket between the server and client", "name": "socket", "type": "stream.Duplex", "desc": "Network socket between the server and client" }, { "textRaw": "`head` {Buffer} The first packet of the upgraded stream (may be empty)", "name": "head", "type": "Buffer", "desc": "The first packet of the upgraded stream (may be empty)" } ], "desc": "Emitted each time a client requests an HTTP upgrade. Listening to this event\nis optional and clients cannot insist on a protocol change.
\nAfter this event is emitted, the request's socket will not have a 'data'
\nevent listener, meaning it will need to be bound in order to handle data\nsent to the server on that socket.
This event is guaranteed to be passed an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specifies a socket\ntype other than <net.Socket>.
" } ], "methods": [ { "textRaw": "`server.close([callback])`", "type": "method", "name": "close", "meta": { "added": [ "v0.1.90" ], "changes": [ { "version": [ "v19.0.0" ], "pr-url": "https://github.com/nodejs/node/pull/43522", "description": "The method closes idle connections before returning." } ] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function" } ] } ], "desc": "Stops the server from accepting new connections and closes all connections\nconnected to this server which are not sending a request or waiting for\na response.\nSee net.Server.close()
.
Closes all connections connected to this server.
" }, { "textRaw": "`server.closeIdleConnections()`", "type": "method", "name": "closeIdleConnections", "meta": { "added": [ "v18.2.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Closes all connections connected to this server which are not sending a request\nor waiting for a response.
" }, { "textRaw": "`server.listen()`", "type": "method", "name": "listen", "signatures": [ { "params": [] } ], "desc": "Starts the HTTP server listening for connections.\nThis method is identical to server.listen()
from net.Server
.
Sets the timeout value for sockets, and emits a 'timeout'
event on\nthe Server object, passing the socket as an argument, if a timeout\noccurs.
If there is a 'timeout'
event listener on the Server object, then it\nwill be called with the timed-out socket as an argument.
By default, the Server does not timeout sockets. However, if a callback\nis assigned to the Server's 'timeout'
event, timeouts must be handled\nexplicitly.
Calls server.close()
and returns a promise that fulfills when the\nserver has closed.
Limit the amount of time the parser will wait to receive the complete HTTP\nheaders.
\nIf the timeout expires, the server responds with status 408 without\nforwarding the request to the request listener and then closes the connection.
\nIt must be set to a non-zero value (e.g. 120 seconds) to protect against\npotential Denial-of-Service attacks in case the server is deployed without a\nreverse proxy in front.
" }, { "textRaw": "`listening` {boolean} Indicates whether or not the server is listening for connections.", "type": "boolean", "name": "listening", "meta": { "added": [ "v5.7.0" ], "changes": [] }, "desc": "Indicates whether or not the server is listening for connections." }, { "textRaw": "`maxHeadersCount` {number} **Default:** `2000`", "type": "number", "name": "maxHeadersCount", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "default": "`2000`", "desc": "Limits maximum incoming headers count. If set to 0, no limit will be applied.
" }, { "textRaw": "`requestTimeout` {number} **Default:** `300000`", "type": "number", "name": "requestTimeout", "meta": { "added": [ "v14.11.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41263", "description": "The default request timeout changed from no timeout to 300s (5 minutes)." } ] }, "default": "`300000`", "desc": "Sets the timeout value in milliseconds for receiving the entire request from\nthe client.
\nIf the timeout expires, the server responds with status 408 without\nforwarding the request to the request listener and then closes the connection.
\nIt must be set to a non-zero value (e.g. 120 seconds) to protect against\npotential Denial-of-Service attacks in case the server is deployed without a\nreverse proxy in front.
" }, { "textRaw": "`maxRequestsPerSocket` {number} Requests per socket. **Default:** 0 (no limit)", "type": "number", "name": "maxRequestsPerSocket", "meta": { "added": [ "v16.10.0" ], "changes": [] }, "default": "0 (no limit)", "desc": "The maximum number of requests socket can handle\nbefore closing keep alive connection.
\nA value of 0
will disable the limit.
When the limit is reached it will set the Connection
header value to close
,\nbut will not actually close the connection, subsequent requests sent\nafter the limit is reached will get 503 Service Unavailable
as a response.
The number of milliseconds of inactivity before a socket is presumed\nto have timed out.
\nA value of 0
will disable the timeout behavior on incoming connections.
The socket timeout logic is set up on connection, so changing this\nvalue only affects new connections to the server, not any existing connections.
", "shortDesc": "Timeout in milliseconds." }, { "textRaw": "`keepAliveTimeout` {number} Timeout in milliseconds. **Default:** `5000` (5 seconds).", "type": "number", "name": "keepAliveTimeout", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "default": "`5000` (5 seconds)", "desc": "The number of milliseconds of inactivity a server needs to wait for additional\nincoming data, after it has finished writing the last response, before a socket\nwill be destroyed. If the server receives new data before the keep-alive\ntimeout has fired, it will reset the regular inactivity timeout, i.e.,\nserver.timeout
.
A value of 0
will disable the keep-alive timeout behavior on incoming\nconnections.\nA value of 0
makes the http server behave similarly to Node.js versions prior\nto 8.0.0, which did not have a keep-alive timeout.
The socket timeout logic is set up on connection, so changing this value only\naffects new connections to the server, not any existing connections.
", "shortDesc": "Timeout in milliseconds." } ] }, { "textRaw": "Class: `http.ServerResponse`", "type": "class", "name": "http.ServerResponse", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "desc": "This object is created internally by an HTTP server, not by the user. It is\npassed as the second parameter to the 'request'
event.
Indicates that the response is completed, or its underlying connection was\nterminated prematurely (before the response completion).
" }, { "textRaw": "Event: `'finish'`", "type": "event", "name": "finish", "meta": { "added": [ "v0.3.6" ], "changes": [] }, "params": [], "desc": "Emitted when the response has been sent. More specifically, this event is\nemitted when the last segment of the response headers and body have been\nhanded off to the operating system for transmission over the network. It\ndoes not imply that the client has received anything yet.
" } ], "methods": [ { "textRaw": "`response.addTrailers(headers)`", "type": "method", "name": "addTrailers", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`headers` {Object}", "name": "headers", "type": "Object" } ] } ], "desc": "This method adds HTTP trailing headers (a header but at the end of the\nmessage) to the response.
\nTrailers will only be emitted if chunked encoding is used for the\nresponse; if it is not (e.g. if the request was HTTP/1.0), they will\nbe silently discarded.
\nHTTP requires the Trailer
header to be sent in order to\nemit trailers, with a list of the header fields in its value. E.g.,
response.writeHead(200, { 'Content-Type': 'text/plain',\n 'Trailer': 'Content-MD5' });\nresponse.write(fileData);\nresponse.addTrailers({ 'Content-MD5': '7895bf4b8828b55ceaf47747b4bca667' });\nresponse.end();\n
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
See writable.cork()
.
This method signals to the server that all of the response headers and body\nhave been sent; that server should consider this message complete.\nThe method, response.end()
, MUST be called on each response.
If data
is specified, it is similar in effect to calling\nresponse.write(data, encoding)
followed by response.end(callback)
.
If callback
is specified, it will be called when the response stream\nis finished.
Flushes the response headers. See also: request.flushHeaders()
.
Reads out a header that's already been queued but not sent to the client.\nThe name is case-insensitive. The type of the return value depends\non the arguments provided to response.setHeader()
.
response.setHeader('Content-Type', 'text/html');\nresponse.setHeader('Content-Length', Buffer.byteLength(body));\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);\nconst contentType = response.getHeader('content-type');\n// contentType is 'text/html'\nconst contentLength = response.getHeader('Content-Length');\n// contentLength is of type number\nconst setCookie = response.getHeader('set-cookie');\n// setCookie is of type string[]\n
"
},
{
"textRaw": "`response.getHeaderNames()`",
"type": "method",
"name": "getHeaderNames",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string\\[]}",
"name": "return",
"type": "string\\[]"
},
"params": []
}
],
"desc": "Returns an array containing the unique names of the current outgoing headers.\nAll header names are lowercase.
\nresponse.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headerNames = response.getHeaderNames();\n// headerNames === ['foo', 'set-cookie']\n
"
},
{
"textRaw": "`response.getHeaders()`",
"type": "method",
"name": "getHeaders",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Returns a shallow copy of the current outgoing headers. Since a shallow copy\nis used, array values may be mutated without additional calls to various\nheader-related http module methods. The keys of the returned object are the\nheader names and the values are the respective header values. All header names\nare lowercase.
\nThe object returned by the response.getHeaders()
method does not\nprototypically inherit from the JavaScript Object
. This means that typical\nObject
methods such as obj.toString()
, obj.hasOwnProperty()
, and others\nare not defined and will not work.
response.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headers = response.getHeaders();\n// headers === { foo: 'bar', 'set-cookie': ['foo=bar', 'bar=baz'] }\n
"
},
{
"textRaw": "`response.hasHeader(name)`",
"type": "method",
"name": "hasHeader",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Returns true
if the header identified by name
is currently set in the\noutgoing headers. The header name matching is case-insensitive.
const hasContentType = response.hasHeader('content-type');\n
"
},
{
"textRaw": "`response.removeHeader(name)`",
"type": "method",
"name": "removeHeader",
"meta": {
"added": [
"v0.4.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Removes a header that's queued for implicit sending.
\nresponse.removeHeader('Content-Encoding');\n
"
},
{
"textRaw": "`response.setHeader(name, value)`",
"type": "method",
"name": "setHeader",
"meta": {
"added": [
"v0.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ServerResponse}",
"name": "return",
"type": "http.ServerResponse"
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns the response object.
\nSets a single header value for implicit headers. If this header already exists\nin the to-be-sent headers, its value will be replaced. Use an array of strings\nhere to send multiple headers with the same name. Non-string values will be\nstored without modification. Therefore, response.getHeader()
may return\nnon-string values. However, the non-string values will be converted to strings\nfor network transmission. The same response object is returned to the caller,\nto enable call chaining.
response.setHeader('Content-Type', 'text/html');\n
\nor
\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);\n
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
When headers have been set with response.setHeader()
, they will be merged\nwith any headers passed to response.writeHead()
, with the headers passed\nto response.writeHead()
given precedence.
// Returns content-type = text/plain\nconst server = http.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\n
\nIf response.writeHead()
method is called and this method has not been\ncalled, it will directly write the supplied header values onto the network\nchannel without caching internally, and the response.getHeader()
on the\nheader will not yield the expected result. If progressive population of headers\nis desired with potential future retrieval and modification, use\nresponse.setHeader()
instead of response.writeHead()
.
Sets the Socket's timeout value to msecs
. If a callback is\nprovided, then it is added as a listener on the 'timeout'
event on\nthe response object.
If no 'timeout'
listener is added to the request, the response, or\nthe server, then sockets are destroyed when they time out. If a handler is\nassigned to the request, the response, or the server's 'timeout'
events,\ntimed out sockets must be handled explicitly.
See writable.uncork()
.
If this method is called and response.writeHead()
has not been called,\nit will switch to implicit header mode and flush the implicit headers.
This sends a chunk of the response body. This method may\nbe called multiple times to provide successive parts of the body.
\nWriting to the body is not allowed when the request method or response status\ndo not support content. If an attempt is made to write to the body for a\nHEAD request or as part of a 204
or 304
response, a synchronous Error
\nwith the code ERR_HTTP_BODY_NOT_ALLOWED
is thrown.
chunk
can be a string or a buffer. If chunk
is a string,\nthe second parameter specifies how to encode it into a byte stream.\ncallback
will be called when this chunk of data is flushed.
This is the raw HTTP body and has nothing to do with higher-level multi-part\nbody encodings that may be used.
\nThe first time response.write()
is called, it will send the buffered\nheader information and the first chunk of the body to the client. The second\ntime response.write()
is called, Node.js assumes data will be streamed,\nand sends the new data separately. That is, the response is buffered up to the\nfirst chunk of the body.
Returns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in user memory.\n'drain'
will be emitted when the buffer is free again.
Sends an HTTP/1.1 100 Continue message to the client, indicating that\nthe request body should be sent. See the 'checkContinue'
event on\nServer
.
Sends an HTTP/1.1 103 Early Hints message to the client with a Link header,\nindicating that the user agent can preload/preconnect the linked resources.\nThe hints
is an object containing the values of headers to be sent with\nearly hints message. The optional callback
argument will be called when\nthe response message has been written.
Example
\nconst earlyHintsLink = '</styles.css>; rel=preload; as=style';\nresponse.writeEarlyHints({\n 'link': earlyHintsLink,\n});\n\nconst earlyHintsLinks = [\n '</styles.css>; rel=preload; as=style',\n '</scripts.js>; rel=preload; as=script',\n];\nresponse.writeEarlyHints({\n 'link': earlyHintsLinks,\n 'x-trace-id': 'id for diagnostics',\n});\n\nconst earlyHintsCallback = () => console.log('early hints message sent');\nresponse.writeEarlyHints({\n 'link': earlyHintsLinks,\n}, earlyHintsCallback);\n
"
},
{
"textRaw": "`response.writeHead(statusCode[, statusMessage][, headers])`",
"type": "method",
"name": "writeHead",
"meta": {
"added": [
"v0.1.30"
],
"changes": [
{
"version": "v14.14.0",
"pr-url": "https://github.com/nodejs/node/pull/35274",
"description": "Allow passing headers as an array."
},
{
"version": [
"v11.10.0",
"v10.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/25974",
"description": "Return `this` from `writeHead()` to allow chaining with `end()`."
},
{
"version": [
"v5.11.0",
"v4.4.5"
],
"pr-url": "https://github.com/nodejs/node/pull/6291",
"description": "A `RangeError` is thrown if `statusCode` is not a number in the range `[100, 999]`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ServerResponse}",
"name": "return",
"type": "http.ServerResponse"
},
"params": [
{
"textRaw": "`statusCode` {number}",
"name": "statusCode",
"type": "number"
},
{
"textRaw": "`statusMessage` {string}",
"name": "statusMessage",
"type": "string"
},
{
"textRaw": "`headers` {Object|Array}",
"name": "headers",
"type": "Object|Array"
}
]
}
],
"desc": "Sends a response header to the request. The status code is a 3-digit HTTP\nstatus code, like 404
. The last argument, headers
, are the response headers.\nOptionally one can give a human-readable statusMessage
as the second\nargument.
headers
may be an Array
where the keys and values are in the same list.\nIt is not a list of tuples. So, the even-numbered offsets are key values,\nand the odd-numbered offsets are the associated values. The array is in the same\nformat as request.rawHeaders
.
Returns a reference to the ServerResponse
, so that calls can be chained.
const body = 'hello world';\nresponse\n .writeHead(200, {\n 'Content-Length': Buffer.byteLength(body),\n 'Content-Type': 'text/plain',\n })\n .end(body);\n
\nThis method must only be called once on a message and it must\nbe called before response.end()
is called.
If response.write()
or response.end()
are called before calling\nthis, the implicit/mutable headers will be calculated and call this function.
When headers have been set with response.setHeader()
, they will be merged\nwith any headers passed to response.writeHead()
, with the headers passed\nto response.writeHead()
given precedence.
If this method is called and response.setHeader()
has not been called,\nit will directly write the supplied header values onto the network channel\nwithout caching internally, and the response.getHeader()
on the header\nwill not yield the expected result. If progressive population of headers is\ndesired with potential future retrieval and modification, use\nresponse.setHeader()
instead.
// Returns content-type = text/plain\nconst server = http.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\n
\nContent-Length
is read in bytes, not characters. Use\nBuffer.byteLength()
to determine the length of the body in bytes. Node.js\nwill check whether Content-Length
and the length of the body which has\nbeen transmitted are equal or not.
Attempting to set a header field name or value that contains invalid characters\nwill result in a [Error
][] being thrown.
Sends a HTTP/1.1 102 Processing message to the client, indicating that\nthe request body should be sent.
" } ], "properties": [ { "textRaw": "`connection` {stream.Duplex}", "type": "stream.Duplex", "name": "connection", "meta": { "added": [ "v0.3.0" ], "deprecated": [ "v13.0.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated. Use [`response.socket`][].", "desc": "See response.socket
.
The response.finished
property will be true
if response.end()
\nhas been called.
Boolean (read-only). True if headers were sent, false otherwise.
" }, { "textRaw": "`req` {http.IncomingMessage}", "type": "http.IncomingMessage", "name": "req", "meta": { "added": [ "v15.7.0" ], "changes": [] }, "desc": "A reference to the original HTTP request
object.
When true, the Date header will be automatically generated and sent in\nthe response if it is not already present in the headers. Defaults to true.
\nThis should only be disabled for testing; HTTP requires the Date header\nin responses.
" }, { "textRaw": "`socket` {stream.Duplex}", "type": "stream.Duplex", "name": "socket", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "desc": "Reference to the underlying socket. Usually users will not want to access\nthis property. In particular, the socket will not emit 'readable'
events\nbecause of how the protocol parser attaches to the socket. After\nresponse.end()
, the property is nulled.
import http from 'node:http';\nconst server = http.createServer((req, res) => {\n const ip = res.socket.remoteAddress;\n const port = res.socket.remotePort;\n res.end(`Your IP address is ${ip} and your source port is ${port}.`);\n}).listen(3000);\n
\nconst http = require('node:http');\nconst server = http.createServer((req, res) => {\n const ip = res.socket.remoteAddress;\n const port = res.socket.remotePort;\n res.end(`Your IP address is ${ip} and your source port is ${port}.`);\n}).listen(3000);\n
\nThis property is guaranteed to be an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specified a socket\ntype other than <net.Socket>.
" }, { "textRaw": "`statusCode` {number} **Default:** `200`", "type": "number", "name": "statusCode", "meta": { "added": [ "v0.4.0" ], "changes": [] }, "default": "`200`", "desc": "When using implicit headers (not calling response.writeHead()
explicitly),\nthis property controls the status code that will be sent to the client when\nthe headers get flushed.
response.statusCode = 404;\n
\nAfter response header was sent to the client, this property indicates the\nstatus code which was sent out.
" }, { "textRaw": "`statusMessage` {string}", "type": "string", "name": "statusMessage", "meta": { "added": [ "v0.11.8" ], "changes": [] }, "desc": "When using implicit headers (not calling response.writeHead()
explicitly),\nthis property controls the status message that will be sent to the client when\nthe headers get flushed. If this is left as undefined
then the standard\nmessage for the status code will be used.
response.statusMessage = 'Not found';\n
\nAfter response header was sent to the client, this property indicates the\nstatus message which was sent out.
" }, { "textRaw": "`strictContentLength` {boolean} **Default:** `false`", "type": "boolean", "name": "strictContentLength", "meta": { "added": [ "v18.10.0", "v16.18.0" ], "changes": [] }, "default": "`false`", "desc": "If set to true
, Node.js will check whether the Content-Length
\nheader value and the size of the body, in bytes, are equal.\nMismatching the Content-Length
header value will result\nin an Error
being thrown, identified by code:
'ERR_HTTP_CONTENT_LENGTH_MISMATCH'
.
Is true
after response.end()
has been called. This property\ndoes not indicate whether the data has been flushed, for this use\nresponse.writableFinished
instead.
Is true
if all data has been flushed to the underlying system, immediately\nbefore the 'finish'
event is emitted.
An IncomingMessage
object is created by http.Server
or\nhttp.ClientRequest
and passed as the first argument to the 'request'
\nand 'response'
event respectively. It may be used to access response\nstatus, headers, and data.
Different from its socket
value which is a subclass of <stream.Duplex>, the\nIncomingMessage
itself extends <stream.Readable> and is created separately to\nparse and emit the incoming HTTP headers and payload, as the underlying socket\nmay be reused multiple times in case of keep-alive.
Emitted when the request has been aborted.
" }, { "textRaw": "Event: `'close'`", "type": "event", "name": "close", "meta": { "added": [ "v0.4.2" ], "changes": [ { "version": "v16.0.0", "pr-url": "https://github.com/nodejs/node/pull/33035", "description": "The close event is now emitted when the request has been completed and not when the underlying socket is closed." } ] }, "params": [], "desc": "Emitted when the request has been completed.
" } ], "properties": [ { "textRaw": "`aborted` {boolean}", "type": "boolean", "name": "aborted", "meta": { "added": [ "v10.1.0" ], "deprecated": [ "v17.0.0", "v16.12.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated. Check `message.destroyed` from <stream.Readable>.", "desc": "The message.aborted
property will be true
if the request has\nbeen aborted.
The message.complete
property will be true
if a complete HTTP message has\nbeen received and successfully parsed.
This property is particularly useful as a means of determining if a client or\nserver fully transmitted a message before a connection was terminated:
\nconst req = http.request({\n host: '127.0.0.1',\n port: 8080,\n method: 'POST',\n}, (res) => {\n res.resume();\n res.on('end', () => {\n if (!res.complete)\n console.error(\n 'The connection was terminated while the message was still being sent');\n });\n});\n
"
},
{
"textRaw": "`message.connection`",
"name": "connection",
"meta": {
"added": [
"v0.1.90"
],
"deprecated": [
"v16.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated. Use [`message.socket`][].",
"desc": "Alias for message.socket
.
The request/response headers object.
\nKey-value pairs of header names and values. Header names are lower-cased.
\n// Prints something like:\n//\n// { 'user-agent': 'curl/7.22.0',\n// host: '127.0.0.1:8000',\n// accept: '*/*' }\nconsole.log(request.headers);\n
\nDuplicates in raw headers are handled in the following ways, depending on the\nheader name:
\nage
, authorization
, content-length
, content-type
,\netag
, expires
, from
, host
, if-modified-since
, if-unmodified-since
,\nlast-modified
, location
, max-forwards
, proxy-authorization
, referer
,\nretry-after
, server
, or user-agent
are discarded.\nTo allow duplicate values of the headers listed above to be joined,\nuse the option joinDuplicateHeaders
in http.request()
\nand http.createServer()
. See RFC 9110 Section 5.3 for more\ninformation.set-cookie
is always an array. Duplicates are added to the array.cookie
headers, the values are joined together with ;
.,
.Similar to message.headers
, but there is no join logic and the values are\nalways arrays of strings, even for headers received just once.
// Prints something like:\n//\n// { 'user-agent': ['curl/7.22.0'],\n// host: ['127.0.0.1:8000'],\n// accept: ['*/*'] }\nconsole.log(request.headersDistinct);\n
"
},
{
"textRaw": "`httpVersion` {string}",
"type": "string",
"name": "httpVersion",
"meta": {
"added": [
"v0.1.1"
],
"changes": []
},
"desc": "In case of server request, the HTTP version sent by the client. In the case of\nclient response, the HTTP version of the connected-to server.\nProbably either '1.1'
or '1.0'
.
Also message.httpVersionMajor
is the first integer and\nmessage.httpVersionMinor
is the second.
Only valid for request obtained from http.Server
.
The request method as a string. Read only. Examples: 'GET'
, 'DELETE'
.
The raw request/response headers list exactly as they were received.
\nThe keys and values are in the same list. It is not a\nlist of tuples. So, the even-numbered offsets are key values, and the\nodd-numbered offsets are the associated values.
\nHeader names are not lowercased, and duplicates are not merged.
\n// Prints something like:\n//\n// [ 'user-agent',\n// 'this is invalid because there can be only one',\n// 'User-Agent',\n// 'curl/7.22.0',\n// 'Host',\n// '127.0.0.1:8000',\n// 'ACCEPT',\n// '*/*' ]\nconsole.log(request.rawHeaders);\n
"
},
{
"textRaw": "`rawTrailers` {string\\[]}",
"type": "string\\[]",
"name": "rawTrailers",
"meta": {
"added": [
"v0.11.6"
],
"changes": []
},
"desc": "The raw request/response trailer keys and values exactly as they were\nreceived. Only populated at the 'end'
event.
The net.Socket
object associated with the connection.
With HTTPS support, use request.socket.getPeerCertificate()
to obtain the\nclient's authentication details.
This property is guaranteed to be an instance of the <net.Socket> class,\na subclass of <stream.Duplex>, unless the user specified a socket\ntype other than <net.Socket> or internally nulled.
" }, { "textRaw": "`statusCode` {number}", "type": "number", "name": "statusCode", "meta": { "added": [ "v0.1.1" ], "changes": [] }, "desc": "Only valid for response obtained from http.ClientRequest
.
The 3-digit HTTP response status code. E.G. 404
.
Only valid for response obtained from http.ClientRequest
.
The HTTP response status message (reason phrase). E.G. OK
or Internal Server Error
.
The request/response trailers object. Only populated at the 'end'
event.
Similar to message.trailers
, but there is no join logic and the values are\nalways arrays of strings, even for headers received just once.\nOnly populated at the 'end'
event.
Only valid for request obtained from http.Server
.
Request URL string. This contains only the URL that is present in the actual\nHTTP request. Take the following request:
\nGET /status?name=ryan HTTP/1.1\nAccept: text/plain\n
\nTo parse the URL into its parts:
\nnew URL(request.url, `http://${request.headers.host}`);\n
\nWhen request.url
is '/status?name=ryan'
and request.headers.host
is\n'localhost:3000'
:
$ node\n> new URL(request.url, `http://${request.headers.host}`)\nURL {\n href: 'http://localhost:3000/status?name=ryan',\n origin: 'http://localhost:3000',\n protocol: 'http:',\n username: '',\n password: '',\n host: 'localhost:3000',\n hostname: 'localhost',\n port: '3000',\n pathname: '/status',\n search: '?name=ryan',\n searchParams: URLSearchParams { 'name' => 'ryan' },\n hash: ''\n}\n
"
}
],
"methods": [
{
"textRaw": "`message.destroy([error])`",
"type": "method",
"name": "destroy",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"version": [
"v14.5.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32789",
"description": "The function returns `this` for consistency with other Readable streams."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {this}",
"name": "return",
"type": "this"
},
"params": [
{
"textRaw": "`error` {Error}",
"name": "error",
"type": "Error"
}
]
}
],
"desc": "Calls destroy()
on the socket that received the IncomingMessage
. If error
\nis provided, an 'error'
event is emitted on the socket and error
is passed\nas an argument to any listeners on the event.
Calls message.socket.setTimeout(msecs, callback)
.
This class serves as the parent class of http.ClientRequest
\nand http.ServerResponse
. It is an abstract outgoing message from\nthe perspective of the participants of an HTTP transaction.
Emitted when the buffer of the message is free again.
" }, { "textRaw": "Event: `'finish'`", "type": "event", "name": "finish", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "params": [], "desc": "Emitted when the transmission is finished successfully.
" }, { "textRaw": "Event: `'prefinish'`", "type": "event", "name": "prefinish", "meta": { "added": [ "v0.11.6" ], "changes": [] }, "params": [], "desc": "Emitted after outgoingMessage.end()
is called.\nWhen the event is emitted, all data has been processed but not necessarily\ncompletely flushed.
Adds HTTP trailers (headers but at the end of the message) to the message.
\nTrailers will only be emitted if the message is chunked encoded. If not,\nthe trailers will be silently discarded.
\nHTTP requires the Trailer
header to be sent to emit trailers,\nwith a list of header field names in its value, e.g.
message.writeHead(200, { 'Content-Type': 'text/plain',\n 'Trailer': 'Content-MD5' });\nmessage.write(fileData);\nmessage.addTrailers({ 'Content-MD5': '7895bf4b8828b55ceaf47747b4bca667' });\nmessage.end();\n
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
Append a single header value to the header object.
\nIf the value is an array, this is equivalent to calling this method multiple\ntimes.
\nIf there were no previous values for the header, this is equivalent to calling\noutgoingMessage.setHeader(name, value)
.
Depending of the value of options.uniqueHeaders
when the client request or the\nserver were created, this will end up in the header being sent multiple times or\na single time with values joined using ;
.
See writable.cork()
.
Destroys the message. Once a socket is associated with the message\nand is connected, that socket will be destroyed as well.
" }, { "textRaw": "`outgoingMessage.end(chunk[, encoding][, callback])`", "type": "method", "name": "end", "meta": { "added": [ "v0.1.90" ], "changes": [ { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/33155", "description": "The `chunk` parameter can now be a `Uint8Array`." }, { "version": "v0.11.6", "description": "add `callback` argument." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {this}", "name": "return", "type": "this" }, "params": [ { "textRaw": "`chunk` {string|Buffer|Uint8Array}", "name": "chunk", "type": "string|Buffer|Uint8Array" }, { "textRaw": "`encoding` {string} Optional, **Default**: `utf8`", "name": "encoding", "type": "string", "desc": "Optional, **Default**: `utf8`" }, { "textRaw": "`callback` {Function} Optional", "name": "callback", "type": "Function", "desc": "Optional" } ] } ], "desc": "Finishes the outgoing message. If any parts of the body are unsent, it will\nflush them to the underlying system. If the message is chunked, it will\nsend the terminating chunk 0\\r\\n\\r\\n
, and send the trailers (if any).
If chunk
is specified, it is equivalent to calling\noutgoingMessage.write(chunk, encoding)
, followed by\noutgoingMessage.end(callback)
.
If callback
is provided, it will be called when the message is finished\n(equivalent to a listener of the 'finish'
event).
Flushes the message headers.
\nFor efficiency reason, Node.js normally buffers the message headers\nuntil outgoingMessage.end()
is called or the first chunk of message data\nis written. It then tries to pack the headers and data into a single TCP\npacket.
It is usually desired (it saves a TCP round-trip), but not when the first\ndata is not sent until possibly much later. outgoingMessage.flushHeaders()
\nbypasses the optimization and kickstarts the message.
Gets the value of the HTTP header with the given name. If that header is not\nset, the returned value will be undefined
.
Returns an array containing the unique names of the current outgoing headers.\nAll names are lowercase.
" }, { "textRaw": "`outgoingMessage.getHeaders()`", "type": "method", "name": "getHeaders", "meta": { "added": [ "v7.7.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "Returns a shallow copy of the current outgoing headers. Since a shallow\ncopy is used, array values may be mutated without additional calls to\nvarious header-related HTTP module methods. The keys of the returned\nobject are the header names and the values are the respective header\nvalues. All header names are lowercase.
\nThe object returned by the outgoingMessage.getHeaders()
method does\nnot prototypically inherit from the JavaScript Object
. This means that\ntypical Object
methods such as obj.toString()
, obj.hasOwnProperty()
,\nand others are not defined and will not work.
outgoingMessage.setHeader('Foo', 'bar');\noutgoingMessage.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headers = outgoingMessage.getHeaders();\n// headers === { foo: 'bar', 'set-cookie': ['foo=bar', 'bar=baz'] }\n
"
},
{
"textRaw": "`outgoingMessage.hasHeader(name)`",
"type": "method",
"name": "hasHeader",
"meta": {
"added": [
"v7.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Returns true
if the header identified by name
is currently set in the\noutgoing headers. The header name is case-insensitive.
const hasContentType = outgoingMessage.hasHeader('content-type');\n
"
},
{
"textRaw": "`outgoingMessage.pipe()`",
"type": "method",
"name": "pipe",
"meta": {
"added": [
"v9.0.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Overrides the stream.pipe()
method inherited from the legacy Stream
class\nwhich is the parent class of http.OutgoingMessage
.
Calling this method will throw an Error
because outgoingMessage
is a\nwrite-only stream.
Removes a header that is queued for implicit sending.
\noutgoingMessage.removeHeader('Content-Encoding');\n
"
},
{
"textRaw": "`outgoingMessage.setHeader(name, value)`",
"type": "method",
"name": "setHeader",
"meta": {
"added": [
"v0.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {this}",
"name": "return",
"type": "this"
},
"params": [
{
"textRaw": "`name` {string} Header name",
"name": "name",
"type": "string",
"desc": "Header name"
},
{
"textRaw": "`value` {any} Header value",
"name": "value",
"type": "any",
"desc": "Header value"
}
]
}
],
"desc": "Sets a single header value. If the header already exists in the to-be-sent\nheaders, its value will be replaced. Use an array of strings to send multiple\nheaders with the same name.
" }, { "textRaw": "`outgoingMessage.setHeaders(headers)`", "type": "method", "name": "setHeaders", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {http.ServerResponse}", "name": "return", "type": "http.ServerResponse" }, "params": [ { "textRaw": "`headers` {Headers|Map}", "name": "headers", "type": "Headers|Map" } ] } ], "desc": "Returns the response object.
\nSets multiple header values for implicit headers.\nheaders
must be an instance of Headers
or Map
,\nif a header already exists in the to-be-sent headers,\nits value will be replaced.
const headers = new Headers({ foo: 'bar' });\nresponse.setHeaders(headers);\n
\nor
\nconst headers = new Map([['foo', 'bar']]);\nres.setHeaders(headers);\n
\nWhen headers have been set with outgoingMessage.setHeaders()
,\nthey will be merged with any headers passed to response.writeHead()
,\nwith the headers passed to response.writeHead()
given precedence.
// Returns content-type = text/plain\nconst server = http.createServer((req, res) => {\n const headers = new Headers({ 'Content-Type': 'text/html' });\n res.setHeaders(headers);\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\n
"
},
{
"textRaw": "`outgoingMessage.setTimeout(msesc[, callback])`",
"type": "method",
"name": "setTimeout",
"meta": {
"added": [
"v0.9.12"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {this}",
"name": "return",
"type": "this"
},
"params": [
{
"textRaw": "`msesc` {number}",
"name": "msesc",
"type": "number"
},
{
"textRaw": "`callback` {Function} Optional function to be called when a timeout occurs. Same as binding to the `timeout` event.",
"name": "callback",
"type": "Function",
"desc": "Optional function to be called when a timeout occurs. Same as binding to the `timeout` event."
}
]
}
],
"desc": "Once a socket is associated with the message and is connected,\nsocket.setTimeout()
will be called with msecs
as the first parameter.
Sends a chunk of the body. This method can be called multiple times.
\nThe encoding
argument is only relevant when chunk
is a string. Defaults to\n'utf8'
.
The callback
argument is optional and will be called when this chunk of data\nis flushed.
Returns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in the user\nmemory. The 'drain'
event will be emitted when the buffer is free again.
Alias of outgoingMessage.socket
.
Read-only. true
if the headers were sent, otherwise false
.
Reference to the underlying socket. Usually, users will not want to access\nthis property.
\nAfter calling outgoingMessage.end()
, this property will be nulled.
The number of times outgoingMessage.cork()
has been called.
Is true
if outgoingMessage.end()
has been called. This property does\nnot indicate whether the data has been flushed. For that purpose, use\nmessage.writableFinished
instead.
Is true
if all data has been flushed to the underlying system.
The highWaterMark
of the underlying socket if assigned. Otherwise, the default\nbuffer level when writable.write()
starts returning false (16384
).
The number of buffered bytes.
" }, { "textRaw": "`writableObjectMode` {boolean}", "type": "boolean", "name": "writableObjectMode", "meta": { "added": [ "v12.9.0" ], "changes": [] }, "desc": "Always false
.
A list of the HTTP methods that are supported by the parser.
" }, { "textRaw": "`STATUS_CODES` {Object}", "type": "Object", "name": "STATUS_CODES", "meta": { "added": [ "v0.1.22" ], "changes": [] }, "desc": "A collection of all the standard HTTP response status codes, and the\nshort description of each. For example, http.STATUS_CODES[404] === 'Not Found'
.
Global instance of Agent
which is used as the default for all HTTP client\nrequests.
Read-only property specifying the maximum allowed size of HTTP headers in bytes.\nDefaults to 16 KiB. Configurable using the --max-http-header-size
CLI\noption.
This can be overridden for servers and client requests by passing the\nmaxHeaderSize
option.
Returns a new instance of http.Server
.
The requestListener
is a function which is automatically\nadded to the 'request'
event.
import http from 'node:http';\n\n// Create a local server to receive data from\nconst server = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'application/json' });\n res.end(JSON.stringify({\n data: 'Hello World!',\n }));\n});\n\nserver.listen(8000);\n
\nconst http = require('node:http');\n\n// Create a local server to receive data from\nconst server = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'application/json' });\n res.end(JSON.stringify({\n data: 'Hello World!',\n }));\n});\n\nserver.listen(8000);\n
\nimport http from 'node:http';\n\n// Create a local server to receive data from\nconst server = http.createServer();\n\n// Listen to the request event\nserver.on('request', (request, res) => {\n res.writeHead(200, { 'Content-Type': 'application/json' });\n res.end(JSON.stringify({\n data: 'Hello World!',\n }));\n});\n\nserver.listen(8000);\n
\nconst http = require('node:http');\n\n// Create a local server to receive data from\nconst server = http.createServer();\n\n// Listen to the request event\nserver.on('request', (request, res) => {\n res.writeHead(200, { 'Content-Type': 'application/json' });\n res.end(JSON.stringify({\n data: 'Hello World!',\n }));\n});\n\nserver.listen(8000);\n
"
},
{
"textRaw": "`http.get(options[, callback])`",
"type": "method",
"name": "get",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ClientRequest}",
"name": "return",
"type": "http.ClientRequest"
},
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object} Accepts the same `options` as [`http.request()`][], with the method set to GET by default.",
"name": "options",
"type": "Object",
"desc": "Accepts the same `options` as [`http.request()`][], with the method set to GET by default."
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Since most requests are GET requests without bodies, Node.js provides this\nconvenience method. The only difference between this method and\nhttp.request()
is that it sets the method to GET by default and calls req.end()
\nautomatically. The callback must take care to consume the response\ndata for reasons stated in http.ClientRequest
section.
The callback
is invoked with a single argument that is an instance of\nhttp.IncomingMessage
.
JSON fetching example:
\nhttp.get('http://localhost:8000/', (res) => {\n const { statusCode } = res;\n const contentType = res.headers['content-type'];\n\n let error;\n // Any 2xx status code signals a successful response but\n // here we're only checking for 200.\n if (statusCode !== 200) {\n error = new Error('Request Failed.\\n' +\n `Status Code: ${statusCode}`);\n } else if (!/^application\\/json/.test(contentType)) {\n error = new Error('Invalid content-type.\\n' +\n `Expected application/json but received ${contentType}`);\n }\n if (error) {\n console.error(error.message);\n // Consume response data to free up memory\n res.resume();\n return;\n }\n\n res.setEncoding('utf8');\n let rawData = '';\n res.on('data', (chunk) => { rawData += chunk; });\n res.on('end', () => {\n try {\n const parsedData = JSON.parse(rawData);\n console.log(parsedData);\n } catch (e) {\n console.error(e.message);\n }\n });\n}).on('error', (e) => {\n console.error(`Got error: ${e.message}`);\n});\n\n// Create a local server to receive data from\nconst server = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'application/json' });\n res.end(JSON.stringify({\n data: 'Hello World!',\n }));\n});\n\nserver.listen(8000);\n
"
},
{
"textRaw": "`http.get(url[, options][, callback])`",
"type": "method",
"name": "get",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ClientRequest}",
"name": "return",
"type": "http.ClientRequest"
},
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object} Accepts the same `options` as [`http.request()`][], with the method set to GET by default.",
"name": "options",
"type": "Object",
"desc": "Accepts the same `options` as [`http.request()`][], with the method set to GET by default."
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Since most requests are GET requests without bodies, Node.js provides this\nconvenience method. The only difference between this method and\nhttp.request()
is that it sets the method to GET by default and calls req.end()
\nautomatically. The callback must take care to consume the response\ndata for reasons stated in http.ClientRequest
section.
The callback
is invoked with a single argument that is an instance of\nhttp.IncomingMessage
.
JSON fetching example:
\nhttp.get('http://localhost:8000/', (res) => {\n const { statusCode } = res;\n const contentType = res.headers['content-type'];\n\n let error;\n // Any 2xx status code signals a successful response but\n // here we're only checking for 200.\n if (statusCode !== 200) {\n error = new Error('Request Failed.\\n' +\n `Status Code: ${statusCode}`);\n } else if (!/^application\\/json/.test(contentType)) {\n error = new Error('Invalid content-type.\\n' +\n `Expected application/json but received ${contentType}`);\n }\n if (error) {\n console.error(error.message);\n // Consume response data to free up memory\n res.resume();\n return;\n }\n\n res.setEncoding('utf8');\n let rawData = '';\n res.on('data', (chunk) => { rawData += chunk; });\n res.on('end', () => {\n try {\n const parsedData = JSON.parse(rawData);\n console.log(parsedData);\n } catch (e) {\n console.error(e.message);\n }\n });\n}).on('error', (e) => {\n console.error(`Got error: ${e.message}`);\n});\n\n// Create a local server to receive data from\nconst server = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'application/json' });\n res.end(JSON.stringify({\n data: 'Hello World!',\n }));\n});\n\nserver.listen(8000);\n
"
},
{
"textRaw": "`http.request(options[, callback])`",
"type": "method",
"name": "request",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": [
"v16.7.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/39310",
"description": "When using a `URL` object parsed username and password will now be properly URI decoded."
},
{
"version": [
"v15.3.0",
"v14.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/36048",
"description": "It is possible to abort a request with an AbortSignal."
},
{
"version": [
"v13.8.0",
"v12.15.0",
"v10.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/31448",
"description": "The `insecureHTTPParser` option is supported now."
},
{
"version": "v13.3.0",
"pr-url": "https://github.com/nodejs/node/pull/30570",
"description": "The `maxHeaderSize` option is supported now."
},
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ClientRequest}",
"name": "return",
"type": "http.ClientRequest"
},
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`agent` {http.Agent | boolean} Controls [`Agent`][] behavior. Possible values:",
"name": "agent",
"type": "http.Agent | boolean",
"desc": "Controls [`Agent`][] behavior. Possible values:",
"options": [
{
"textRaw": "`undefined` (default): use [`http.globalAgent`][] for this host and port.",
"name": "undefined",
"desc": "(default): use [`http.globalAgent`][] for this host and port."
},
{
"textRaw": "`Agent` object: explicitly use the passed in `Agent`.",
"name": "Agent",
"desc": "object: explicitly use the passed in `Agent`."
},
{
"textRaw": "`false`: causes a new `Agent` with default values to be used.",
"name": "false",
"desc": "causes a new `Agent` with default values to be used."
}
]
},
{
"textRaw": "`auth` {string} Basic authentication (`'user:password'`) to compute an Authorization header.",
"name": "auth",
"type": "string",
"desc": "Basic authentication (`'user:password'`) to compute an Authorization header."
},
{
"textRaw": "`createConnection` {Function} A function that produces a socket/stream to use for the request when the `agent` option is not used. This can be used to avoid creating a custom `Agent` class just to override the default `createConnection` function. See [`agent.createConnection()`][] for more details. Any [`Duplex`][] stream is a valid return value.",
"name": "createConnection",
"type": "Function",
"desc": "A function that produces a socket/stream to use for the request when the `agent` option is not used. This can be used to avoid creating a custom `Agent` class just to override the default `createConnection` function. See [`agent.createConnection()`][] for more details. Any [`Duplex`][] stream is a valid return value."
},
{
"textRaw": "`defaultPort` {number} Default port for the protocol. **Default:** `agent.defaultPort` if an `Agent` is used, else `undefined`.",
"name": "defaultPort",
"type": "number",
"default": "`agent.defaultPort` if an `Agent` is used, else `undefined`",
"desc": "Default port for the protocol."
},
{
"textRaw": "`family` {number} IP address family to use when resolving `host` or `hostname`. Valid values are `4` or `6`. When unspecified, both IP v4 and v6 will be used.",
"name": "family",
"type": "number",
"desc": "IP address family to use when resolving `host` or `hostname`. Valid values are `4` or `6`. When unspecified, both IP v4 and v6 will be used."
},
{
"textRaw": "`headers` {Object} An object containing request headers.",
"name": "headers",
"type": "Object",
"desc": "An object containing request headers."
},
{
"textRaw": "`hints` {number} Optional [`dns.lookup()` hints][].",
"name": "hints",
"type": "number",
"desc": "Optional [`dns.lookup()` hints][]."
},
{
"textRaw": "`host` {string} A domain name or IP address of the server to issue the request to. **Default:** `'localhost'`.",
"name": "host",
"type": "string",
"default": "`'localhost'`",
"desc": "A domain name or IP address of the server to issue the request to."
},
{
"textRaw": "`hostname` {string} Alias for `host`. To support [`url.parse()`][], `hostname` will be used if both `host` and `hostname` are specified.",
"name": "hostname",
"type": "string",
"desc": "Alias for `host`. To support [`url.parse()`][], `hostname` will be used if both `host` and `hostname` are specified."
},
{
"textRaw": "`insecureHTTPParser` {boolean} If set to `true`, it will use a HTTP parser with leniency flags enabled. Using the insecure parser should be avoided. See [`--insecure-http-parser`][] for more information. **Default:** `false`",
"name": "insecureHTTPParser",
"type": "boolean",
"default": "`false`",
"desc": "If set to `true`, it will use a HTTP parser with leniency flags enabled. Using the insecure parser should be avoided. See [`--insecure-http-parser`][] for more information."
},
{
"textRaw": "`joinDuplicateHeaders` {boolean} It joins the field line values of multiple headers in a request with `, ` instead of discarding the duplicates. See [`message.headers`][] for more information. **Default:** `false`.",
"name": "joinDuplicateHeaders",
"type": "boolean",
"default": "`false`",
"desc": "It joins the field line values of multiple headers in a request with `, ` instead of discarding the duplicates. See [`message.headers`][] for more information."
},
{
"textRaw": "`localAddress` {string} Local interface to bind for network connections.",
"name": "localAddress",
"type": "string",
"desc": "Local interface to bind for network connections."
},
{
"textRaw": "`localPort` {number} Local port to connect from.",
"name": "localPort",
"type": "number",
"desc": "Local port to connect from."
},
{
"textRaw": "`lookup` {Function} Custom lookup function. **Default:** [`dns.lookup()`][].",
"name": "lookup",
"type": "Function",
"default": "[`dns.lookup()`][]",
"desc": "Custom lookup function."
},
{
"textRaw": "`maxHeaderSize` {number} Optionally overrides the value of [`--max-http-header-size`][] (the maximum length of response headers in bytes) for responses received from the server. **Default:** 16384 (16 KiB).",
"name": "maxHeaderSize",
"type": "number",
"default": "16384 (16 KiB)",
"desc": "Optionally overrides the value of [`--max-http-header-size`][] (the maximum length of response headers in bytes) for responses received from the server."
},
{
"textRaw": "`method` {string} A string specifying the HTTP request method. **Default:** `'GET'`.",
"name": "method",
"type": "string",
"default": "`'GET'`",
"desc": "A string specifying the HTTP request method."
},
{
"textRaw": "`path` {string} Request path. Should include query string if any. E.G. `'/index.html?page=12'`. An exception is thrown when the request path contains illegal characters. Currently, only spaces are rejected but that may change in the future. **Default:** `'/'`.",
"name": "path",
"type": "string",
"default": "`'/'`",
"desc": "Request path. Should include query string if any. E.G. `'/index.html?page=12'`. An exception is thrown when the request path contains illegal characters. Currently, only spaces are rejected but that may change in the future."
},
{
"textRaw": "`port` {number} Port of remote server. **Default:** `defaultPort` if set, else `80`.",
"name": "port",
"type": "number",
"default": "`defaultPort` if set, else `80`",
"desc": "Port of remote server."
},
{
"textRaw": "`protocol` {string} Protocol to use. **Default:** `'http:'`.",
"name": "protocol",
"type": "string",
"default": "`'http:'`",
"desc": "Protocol to use."
},
{
"textRaw": "`setHost` {boolean}: Specifies whether or not to automatically add the `Host` header. Defaults to `true`.",
"name": "setHost",
"type": "boolean",
"desc": ": Specifies whether or not to automatically add the `Host` header. Defaults to `true`."
},
{
"textRaw": "`signal` {AbortSignal}: An AbortSignal that may be used to abort an ongoing request.",
"name": "signal",
"type": "AbortSignal",
"desc": ": An AbortSignal that may be used to abort an ongoing request."
},
{
"textRaw": "`socketPath` {string} Unix domain socket. Cannot be used if one of `host` or `port` is specified, as those specify a TCP Socket.",
"name": "socketPath",
"type": "string",
"desc": "Unix domain socket. Cannot be used if one of `host` or `port` is specified, as those specify a TCP Socket."
},
{
"textRaw": "`timeout` {number}: A number specifying the socket timeout in milliseconds. This will set the timeout before the socket is connected.",
"name": "timeout",
"type": "number",
"desc": ": A number specifying the socket timeout in milliseconds. This will set the timeout before the socket is connected."
},
{
"textRaw": "`uniqueHeaders` {Array} A list of request headers that should be sent only once. If the header's value is an array, the items will be joined using `; `.",
"name": "uniqueHeaders",
"type": "Array",
"desc": "A list of request headers that should be sent only once. If the header's value is an array, the items will be joined using `; `."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "options
in socket.connect()
are also supported.
Node.js maintains several connections per server to make HTTP requests.\nThis function allows one to transparently issue requests.
\nurl
can be a string or a URL
object. If url
is a\nstring, it is automatically parsed with new URL()
. If it is a URL
\nobject, it will be automatically converted to an ordinary options
object.
If both url
and options
are specified, the objects are merged, with the\noptions
properties taking precedence.
The optional callback
parameter will be added as a one-time listener for\nthe 'response'
event.
http.request()
returns an instance of the http.ClientRequest
\nclass. The ClientRequest
instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest
object.
import http from 'node:http';\nimport { Buffer } from 'node:buffer';\n\nconst postData = JSON.stringify({\n 'msg': 'Hello World!',\n});\n\nconst options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/json',\n 'Content-Length': Buffer.byteLength(postData),\n },\n};\n\nconst req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.');\n });\n});\n\nreq.on('error', (e) => {\n console.error(`problem with request: ${e.message}`);\n});\n\n// Write data to request body\nreq.write(postData);\nreq.end();\n
\nconst http = require('node:http');\n\nconst postData = JSON.stringify({\n 'msg': 'Hello World!',\n});\n\nconst options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/json',\n 'Content-Length': Buffer.byteLength(postData),\n },\n};\n\nconst req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.');\n });\n});\n\nreq.on('error', (e) => {\n console.error(`problem with request: ${e.message}`);\n});\n\n// Write data to request body\nreq.write(postData);\nreq.end();\n
\nIn the example req.end()
was called. With http.request()
one\nmust always call req.end()
to signify the end of the request -\neven if there is no data being written to the request body.
If any error is encountered during the request (be that with DNS resolution,\nTCP level errors, or actual HTTP parse errors) an 'error'
event is emitted\non the returned request object. As with all 'error'
events, if no listeners\nare registered the error will be thrown.
There are a few special headers that should be noted.
\nSending a 'Connection: keep-alive' will notify Node.js that the connection to\nthe server should be persisted until the next request.
\nSending a 'Content-Length' header will disable the default chunked encoding.
\nSending an 'Expect' header will immediately send the request headers.\nUsually, when sending 'Expect: 100-continue', both a timeout and a listener\nfor the 'continue'
event should be set. See RFC 2616 Section 8.2.3 for more\ninformation.
Sending an Authorization header will override using the auth
option\nto compute basic authentication.
Example using a URL
as options
:
const options = new URL('http://abc:xyz@example.com');\n\nconst req = http.request(options, (res) => {\n // ...\n});\n
\nIn a successful request, the following events will be emitted in the following\norder:
\n'socket'
'response'
\n'data'
any number of times, on the res
object\n('data'
will not be emitted at all if the response body is empty, for\ninstance, in most redirects)'end'
on the res
object'close'
In the case of a connection error, the following events will be emitted:
\n'socket'
'error'
'close'
In the case of a premature connection close before the response is received,\nthe following events will be emitted in the following order:
\n'socket'
'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
'close'
In the case of a premature connection close after the response is received,\nthe following events will be emitted in the following order:
\n'socket'
'response'
\n'data'
any number of times, on the res
object'aborted'
on the res
object'error'
on the res
object with an error with message\n'Error: aborted'
and code 'ECONNRESET'
'close'
'close'
on the res
objectIf req.destroy()
is called before a socket is assigned, the following\nevents will be emitted in the following order:
req.destroy()
called here)'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
, or the error with which req.destroy()
was called'close'
If req.destroy()
is called before the connection succeeds, the following\nevents will be emitted in the following order:
'socket'
req.destroy()
called here)'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
, or the error with which req.destroy()
was called'close'
If req.destroy()
is called after the response is received, the following\nevents will be emitted in the following order:
'socket'
'response'
\n'data'
any number of times, on the res
objectreq.destroy()
called here)'aborted'
on the res
object'error'
on the res
object with an error with message 'Error: aborted'
\nand code 'ECONNRESET'
, or the error with which req.destroy()
was called'close'
'close'
on the res
objectIf req.abort()
is called before a socket is assigned, the following\nevents will be emitted in the following order:
req.abort()
called here)'abort'
'close'
If req.abort()
is called before the connection succeeds, the following\nevents will be emitted in the following order:
'socket'
req.abort()
called here)'abort'
'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
'close'
If req.abort()
is called after the response is received, the following\nevents will be emitted in the following order:
'socket'
'response'
\n'data'
any number of times, on the res
objectreq.abort()
called here)'abort'
'aborted'
on the res
object'error'
on the res
object with an error with message\n'Error: aborted'
and code 'ECONNRESET'
.'close'
'close'
on the res
objectSetting the timeout
option or using the setTimeout()
function will\nnot abort the request or do anything besides add a 'timeout'
event.
Passing an AbortSignal
and then calling abort()
on the corresponding\nAbortController
will behave the same way as calling .destroy()
on the\nrequest. Specifically, the 'error'
event will be emitted with an error with\nthe message 'AbortError: The operation was aborted'
, the code 'ABORT_ERR'
\nand the cause
, if one was provided.
options
in socket.connect()
are also supported.
Node.js maintains several connections per server to make HTTP requests.\nThis function allows one to transparently issue requests.
\nurl
can be a string or a URL
object. If url
is a\nstring, it is automatically parsed with new URL()
. If it is a URL
\nobject, it will be automatically converted to an ordinary options
object.
If both url
and options
are specified, the objects are merged, with the\noptions
properties taking precedence.
The optional callback
parameter will be added as a one-time listener for\nthe 'response'
event.
http.request()
returns an instance of the http.ClientRequest
\nclass. The ClientRequest
instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest
object.
import http from 'node:http';\nimport { Buffer } from 'node:buffer';\n\nconst postData = JSON.stringify({\n 'msg': 'Hello World!',\n});\n\nconst options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/json',\n 'Content-Length': Buffer.byteLength(postData),\n },\n};\n\nconst req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.');\n });\n});\n\nreq.on('error', (e) => {\n console.error(`problem with request: ${e.message}`);\n});\n\n// Write data to request body\nreq.write(postData);\nreq.end();\n
\nconst http = require('node:http');\n\nconst postData = JSON.stringify({\n 'msg': 'Hello World!',\n});\n\nconst options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/json',\n 'Content-Length': Buffer.byteLength(postData),\n },\n};\n\nconst req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.');\n });\n});\n\nreq.on('error', (e) => {\n console.error(`problem with request: ${e.message}`);\n});\n\n// Write data to request body\nreq.write(postData);\nreq.end();\n
\nIn the example req.end()
was called. With http.request()
one\nmust always call req.end()
to signify the end of the request -\neven if there is no data being written to the request body.
If any error is encountered during the request (be that with DNS resolution,\nTCP level errors, or actual HTTP parse errors) an 'error'
event is emitted\non the returned request object. As with all 'error'
events, if no listeners\nare registered the error will be thrown.
There are a few special headers that should be noted.
\nSending a 'Connection: keep-alive' will notify Node.js that the connection to\nthe server should be persisted until the next request.
\nSending a 'Content-Length' header will disable the default chunked encoding.
\nSending an 'Expect' header will immediately send the request headers.\nUsually, when sending 'Expect: 100-continue', both a timeout and a listener\nfor the 'continue'
event should be set. See RFC 2616 Section 8.2.3 for more\ninformation.
Sending an Authorization header will override using the auth
option\nto compute basic authentication.
Example using a URL
as options
:
const options = new URL('http://abc:xyz@example.com');\n\nconst req = http.request(options, (res) => {\n // ...\n});\n
\nIn a successful request, the following events will be emitted in the following\norder:
\n'socket'
'response'
\n'data'
any number of times, on the res
object\n('data'
will not be emitted at all if the response body is empty, for\ninstance, in most redirects)'end'
on the res
object'close'
In the case of a connection error, the following events will be emitted:
\n'socket'
'error'
'close'
In the case of a premature connection close before the response is received,\nthe following events will be emitted in the following order:
\n'socket'
'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
'close'
In the case of a premature connection close after the response is received,\nthe following events will be emitted in the following order:
\n'socket'
'response'
\n'data'
any number of times, on the res
object'aborted'
on the res
object'error'
on the res
object with an error with message\n'Error: aborted'
and code 'ECONNRESET'
'close'
'close'
on the res
objectIf req.destroy()
is called before a socket is assigned, the following\nevents will be emitted in the following order:
req.destroy()
called here)'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
, or the error with which req.destroy()
was called'close'
If req.destroy()
is called before the connection succeeds, the following\nevents will be emitted in the following order:
'socket'
req.destroy()
called here)'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
, or the error with which req.destroy()
was called'close'
If req.destroy()
is called after the response is received, the following\nevents will be emitted in the following order:
'socket'
'response'
\n'data'
any number of times, on the res
objectreq.destroy()
called here)'aborted'
on the res
object'error'
on the res
object with an error with message 'Error: aborted'
\nand code 'ECONNRESET'
, or the error with which req.destroy()
was called'close'
'close'
on the res
objectIf req.abort()
is called before a socket is assigned, the following\nevents will be emitted in the following order:
req.abort()
called here)'abort'
'close'
If req.abort()
is called before the connection succeeds, the following\nevents will be emitted in the following order:
'socket'
req.abort()
called here)'abort'
'error'
with an error with message 'Error: socket hang up'
and code\n'ECONNRESET'
'close'
If req.abort()
is called after the response is received, the following\nevents will be emitted in the following order:
'socket'
'response'
\n'data'
any number of times, on the res
objectreq.abort()
called here)'abort'
'aborted'
on the res
object'error'
on the res
object with an error with message\n'Error: aborted'
and code 'ECONNRESET'
.'close'
'close'
on the res
objectSetting the timeout
option or using the setTimeout()
function will\nnot abort the request or do anything besides add a 'timeout'
event.
Passing an AbortSignal
and then calling abort()
on the corresponding\nAbortController
will behave the same way as calling .destroy()
on the\nrequest. Specifically, the 'error'
event will be emitted with an error with\nthe message 'AbortError: The operation was aborted'
, the code 'ABORT_ERR'
\nand the cause
, if one was provided.
Performs the low-level validations on the provided name
that are done when\nres.setHeader(name, value)
is called.
Passing illegal value as name
will result in a TypeError
being thrown,\nidentified by code: 'ERR_INVALID_HTTP_TOKEN'
.
It is not necessary to use this method before passing headers to an HTTP request\nor response. The HTTP module will automatically validate such headers.
\nExample:
\nimport { validateHeaderName } from 'node:http';\n\ntry {\n validateHeaderName('');\n} catch (err) {\n console.error(err instanceof TypeError); // --> true\n console.error(err.code); // --> 'ERR_INVALID_HTTP_TOKEN'\n console.error(err.message); // --> 'Header name must be a valid HTTP token [\"\"]'\n}\n
\nconst { validateHeaderName } = require('node:http');\n\ntry {\n validateHeaderName('');\n} catch (err) {\n console.error(err instanceof TypeError); // --> true\n console.error(err.code); // --> 'ERR_INVALID_HTTP_TOKEN'\n console.error(err.message); // --> 'Header name must be a valid HTTP token [\"\"]'\n}\n
"
},
{
"textRaw": "`http.validateHeaderValue(name, value)`",
"type": "method",
"name": "validateHeaderValue",
"meta": {
"added": [
"v14.3.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Performs the low-level validations on the provided value
that are done when\nres.setHeader(name, value)
is called.
Passing illegal value as value
will result in a TypeError
being thrown.
code: 'ERR_HTTP_INVALID_HEADER_VALUE'
.code: 'ERR_INVALID_CHAR'
.It is not necessary to use this method before passing headers to an HTTP request\nor response. The HTTP module will automatically validate such headers.
\nExamples:
\nimport { validateHeaderValue } from 'node:http';\n\ntry {\n validateHeaderValue('x-my-header', undefined);\n} catch (err) {\n console.error(err instanceof TypeError); // --> true\n console.error(err.code === 'ERR_HTTP_INVALID_HEADER_VALUE'); // --> true\n console.error(err.message); // --> 'Invalid value \"undefined\" for header \"x-my-header\"'\n}\n\ntry {\n validateHeaderValue('x-my-header', 'oʊmɪɡə');\n} catch (err) {\n console.error(err instanceof TypeError); // --> true\n console.error(err.code === 'ERR_INVALID_CHAR'); // --> true\n console.error(err.message); // --> 'Invalid character in header content [\"x-my-header\"]'\n}\n
\nconst { validateHeaderValue } = require('node:http');\n\ntry {\n validateHeaderValue('x-my-header', undefined);\n} catch (err) {\n console.error(err instanceof TypeError); // --> true\n console.error(err.code === 'ERR_HTTP_INVALID_HEADER_VALUE'); // --> true\n console.error(err.message); // --> 'Invalid value \"undefined\" for header \"x-my-header\"'\n}\n\ntry {\n validateHeaderValue('x-my-header', 'oʊmɪɡə');\n} catch (err) {\n console.error(err instanceof TypeError); // --> true\n console.error(err.code === 'ERR_INVALID_CHAR'); // --> true\n console.error(err.message); // --> 'Invalid character in header content [\"x-my-header\"]'\n}\n
"
},
{
"textRaw": "`http.setMaxIdleHTTPParsers(max)`",
"type": "method",
"name": "setMaxIdleHTTPParsers",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`max` {number} **Default:** `1000`.",
"name": "max",
"type": "number",
"default": "`1000`"
}
]
}
],
"desc": "Set the maximum number of idle HTTP parsers.
" } ], "type": "module", "displayName": "HTTP", "source": "doc/api/http.md" }, { "textRaw": "HTTP/2", "name": "http/2", "meta": { "added": [ "v8.4.0" ], "changes": [ { "version": [ "v15.3.0", "v14.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/36070", "description": "It is possible to abort a request with an AbortSignal." }, { "version": "v15.0.0", "pr-url": "https://github.com/nodejs/node/pull/34664", "description": "Requests with the `host` header (with or without `:authority`) can now be sent/received." }, { "version": "v10.10.0", "pr-url": "https://github.com/nodejs/node/pull/22466", "description": "HTTP/2 is now Stable. Previously, it had been Experimental." } ] }, "introduced_in": "v8.4.0", "stability": 2, "stabilityText": "Stable", "desc": "Source Code: lib/http2.js
\nThe node:http2
module provides an implementation of the HTTP/2 protocol.\nIt can be accessed using:
const http2 = require('node:http2');\n
",
"modules": [
{
"textRaw": "Determining if crypto support is unavailable",
"name": "determining_if_crypto_support_is_unavailable",
"desc": "It is possible for Node.js to be built without including support for the\nnode:crypto
module. In such cases, attempting to import
from node:http2
or\ncalling require('node:http2')
will result in an error being thrown.
When using CommonJS, the error thrown can be caught using try/catch:
\nlet http2;\ntry {\n http2 = require('node:http2');\n} catch (err) {\n console.error('http2 support is disabled!');\n}\n
\nWhen using the lexical ESM import
keyword, the error can only be\ncaught if a handler for process.on('uncaughtException')
is registered\nbefore any attempt to load the module is made (using, for instance,\na preload module).
When using ESM, if there is a chance that the code may be run on a build\nof Node.js where crypto support is not enabled, consider using the\nimport()
function instead of the lexical import
keyword:
let http2;\ntry {\n http2 = await import('node:http2');\n} catch (err) {\n console.error('http2 support is disabled!');\n}\n
",
"type": "module",
"displayName": "Determining if crypto support is unavailable"
},
{
"textRaw": "Core API",
"name": "core_api",
"desc": "The Core API provides a low-level interface designed specifically around\nsupport for HTTP/2 protocol features. It is specifically not designed for\ncompatibility with the existing HTTP/1 module API. However,\nthe Compatibility API is.
\nThe http2
Core API is much more symmetric between client and server than the\nhttp
API. For instance, most events, like 'error'
, 'connect'
and\n'stream'
, can be emitted either by client-side code or server-side code.
The following illustrates a simple HTTP/2 server using the Core API.\nSince there are no browsers known that support\nunencrypted HTTP/2, the use of\nhttp2.createSecureServer()
is necessary when communicating\nwith browser clients.
const http2 = require('node:http2');\nconst fs = require('node:fs');\n\nconst server = http2.createSecureServer({\n key: fs.readFileSync('localhost-privkey.pem'),\n cert: fs.readFileSync('localhost-cert.pem'),\n});\nserver.on('error', (err) => console.error(err));\n\nserver.on('stream', (stream, headers) => {\n // stream is a Duplex\n stream.respond({\n 'content-type': 'text/html; charset=utf-8',\n ':status': 200,\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(8443);\n
\nTo generate the certificate and key for this example, run:
\nopenssl req -x509 -newkey rsa:2048 -nodes -sha256 -subj '/CN=localhost' \\\n -keyout localhost-privkey.pem -out localhost-cert.pem\n
",
"type": "module",
"displayName": "Server-side example"
},
{
"textRaw": "Client-side example",
"name": "client-side_example",
"desc": "The following illustrates an HTTP/2 client:
\nconst http2 = require('node:http2');\nconst fs = require('node:fs');\nconst client = http2.connect('https://localhost:8443', {\n ca: fs.readFileSync('localhost-cert.pem'),\n});\nclient.on('error', (err) => console.error(err));\n\nconst req = client.request({ ':path': '/' });\n\nreq.on('response', (headers, flags) => {\n for (const name in headers) {\n console.log(`${name}: ${headers[name]}`);\n }\n});\n\nreq.setEncoding('utf8');\nlet data = '';\nreq.on('data', (chunk) => { data += chunk; });\nreq.on('end', () => {\n console.log(`\\n${data}`);\n client.close();\n});\nreq.end();\n
",
"type": "module",
"displayName": "Client-side example"
},
{
"textRaw": "Headers object",
"name": "headers_object",
"desc": "Headers are represented as own-properties on JavaScript objects. The property\nkeys will be serialized to lower-case. Property values should be strings (if\nthey are not they will be coerced to strings) or an Array
of strings (in order\nto send more than one value per header field).
const headers = {\n ':status': '200',\n 'content-type': 'text-plain',\n 'ABC': ['has', 'more', 'than', 'one', 'value'],\n};\n\nstream.respond(headers);\n
\nHeader objects passed to callback functions will have a null
prototype. This\nmeans that normal JavaScript object methods such as\nObject.prototype.toString()
and Object.prototype.hasOwnProperty()
will\nnot work.
For incoming headers:
\n:status
header is converted to number
.:status
, :method
, :authority
, :scheme
, :path
,\n:protocol
, age
, authorization
, access-control-allow-credentials
,\naccess-control-max-age
, access-control-request-method
, content-encoding
,\ncontent-language
, content-length
, content-location
, content-md5
,\ncontent-range
, content-type
, date
, dnt
, etag
, expires
, from
,\nhost
, if-match
, if-modified-since
, if-none-match
, if-range
,\nif-unmodified-since
, last-modified
, location
, max-forwards
,\nproxy-authorization
, range
, referer
,retry-after
, tk
,\nupgrade-insecure-requests
, user-agent
or x-content-type-options
are\ndiscarded.set-cookie
is always an array. Duplicates are added to the array.cookie
headers, the values are joined together with '; '.const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream, headers) => {\n console.log(headers[':path']);\n console.log(headers.ABC);\n});\n
",
"modules": [
{
"textRaw": "Sensitive headers",
"name": "sensitive_headers",
"desc": "HTTP2 headers can be marked as sensitive, which means that the HTTP/2\nheader compression algorithm will never index them. This can make sense for\nheader values with low entropy and that may be considered valuable to an\nattacker, for example Cookie
or Authorization
. To achieve this, add\nthe header name to the [http2.sensitiveHeaders]
property as an array:
const headers = {\n ':status': '200',\n 'content-type': 'text-plain',\n 'cookie': 'some-cookie',\n 'other-sensitive-header': 'very secret data',\n [http2.sensitiveHeaders]: ['cookie', 'other-sensitive-header'],\n};\n\nstream.respond(headers);\n
\nFor some headers, such as Authorization
and short Cookie
headers,\nthis flag is set automatically.
This property is also set for received headers. It will contain the names of\nall headers marked as sensitive, including ones marked that way automatically.
", "type": "module", "displayName": "Sensitive headers" } ], "type": "module", "displayName": "Headers object" }, { "textRaw": "Settings object", "name": "settings_object", "meta": { "added": [ "v8.4.0" ], "changes": [ { "version": "v12.12.0", "pr-url": "https://github.com/nodejs/node/pull/29833", "description": "The `maxConcurrentStreams` setting is stricter." }, { "version": "v8.9.3", "pr-url": "https://github.com/nodejs/node/pull/16676", "description": "The `maxHeaderListSize` setting is now strictly enforced." } ] }, "desc": "The http2.getDefaultSettings()
, http2.getPackedSettings()
,\nhttp2.createServer()
, http2.createSecureServer()
,\nhttp2session.settings()
, http2session.localSettings
, and\nhttp2session.remoteSettings
APIs either return or receive as input an\nobject that defines configuration settings for an Http2Session
object.\nThese objects are ordinary JavaScript objects containing the following\nproperties.
headerTableSize
<number> Specifies the maximum number of bytes used for\nheader compression. The minimum allowed value is 0. The maximum allowed value\nis 232-1. Default: 4096
.enablePush
<boolean> Specifies true
if HTTP/2 Push Streams are to be\npermitted on the Http2Session
instances. Default: true
.initialWindowSize
<number> Specifies the sender's initial window size in\nbytes for stream-level flow control. The minimum allowed value is 0. The\nmaximum allowed value is 232-1. Default: 65535
.maxFrameSize
<number> Specifies the size in bytes of the largest frame\npayload. The minimum allowed value is 16,384. The maximum allowed value is\n224-1. Default: 16384
.maxConcurrentStreams
<number> Specifies the maximum number of concurrent\nstreams permitted on an Http2Session
. There is no default value which\nimplies, at least theoretically, 232-1 streams may be open\nconcurrently at any given time in an Http2Session
. The minimum value\nis 0. The maximum allowed value is 232-1. Default:\n4294967295
.maxHeaderListSize
<number> Specifies the maximum size (uncompressed octets)\nof header list that will be accepted. The minimum allowed value is 0. The\nmaximum allowed value is 232-1. Default: 65535
.maxHeaderSize
<number> Alias for maxHeaderListSize
.enableConnectProtocol
<boolean> Specifies true
if the \"Extended Connect\nProtocol\" defined by RFC 8441 is to be enabled. This setting is only\nmeaningful if sent by the server. Once the enableConnectProtocol
setting\nhas been enabled for a given Http2Session
, it cannot be disabled.\nDefault: false
.customSettings
<Object> Specifies additional settings, yet not implemented\nin node and the underlying libraries. The key of the object defines the\nnumeric value of the settings type (as defined in the \"HTTP/2 SETTINGS\"\nregistry established by [RFC 7540]) and the values the actual numeric value\nof the settings.\nThe settings type has to be an integer in the range from 1 to 2^16-1.\nIt should not be a settings type already handled by node, i.e. currently\nit should be greater than 6, although it is not an error.\nThe values need to be unsigned integers in the range from 0 to 2^32-1.\nCurrently, a maximum of up 10 custom settings is supported.\nIt is only supported for sending SETTINGS, or for receiving settings values\nspecified in the remoteCustomSettings
options of the server or client\nobject. Do not mix the customSettings
-mechanism for a settings id with\ninterfaces for the natively handled settings, in case a setting becomes\nnatively supported in a future node version.All additional properties on the settings object are ignored.
", "type": "module", "displayName": "Settings object" }, { "textRaw": "Error handling", "name": "error_handling", "desc": "There are several types of error conditions that may arise when using the\nnode:http2
module:
Validation errors occur when an incorrect argument, option, or setting value is\npassed in. These will always be reported by a synchronous throw
.
State errors occur when an action is attempted at an incorrect time (for\ninstance, attempting to send data on a stream after it has closed). These will\nbe reported using either a synchronous throw
or via an 'error'
event on\nthe Http2Stream
, Http2Session
or HTTP/2 Server objects, depending on where\nand when the error occurs.
Internal errors occur when an HTTP/2 session fails unexpectedly. These will be\nreported via an 'error'
event on the Http2Session
or HTTP/2 Server objects.
Protocol errors occur when various HTTP/2 protocol constraints are violated.\nThese will be reported using either a synchronous throw
or via an 'error'
\nevent on the Http2Stream
, Http2Session
or HTTP/2 Server objects, depending\non where and when the error occurs.
The HTTP/2 implementation applies stricter handling of invalid characters in\nHTTP header names and values than the HTTP/1 implementation.
\nHeader field names are case-insensitive and are transmitted over the wire\nstrictly as lower-case strings. The API provided by Node.js allows header\nnames to be set as mixed-case strings (e.g. Content-Type
) but will convert\nthose to lower-case (e.g. content-type
) upon transmission.
Header field-names must only contain one or more of the following ASCII\ncharacters: a
-z
, A
-Z
, 0
-9
, !
, #
, $
, %
, &
, '
, *
, +
,\n-
, .
, ^
, _
, `
(backtick), |
, and ~
.
Using invalid characters within an HTTP header field name will cause the\nstream to be closed with a protocol error being reported.
\nHeader field values are handled with more leniency but should not contain\nnew-line or carriage return characters and should be limited to US-ASCII\ncharacters, per the requirements of the HTTP specification.
", "type": "module", "displayName": "Invalid character handling in header names and values" }, { "textRaw": "Push streams on the client", "name": "push_streams_on_the_client", "desc": "To receive pushed streams on the client, set a listener for the 'stream'
\nevent on the ClientHttp2Session
:
const http2 = require('node:http2');\n\nconst client = http2.connect('http://localhost');\n\nclient.on('stream', (pushedStream, requestHeaders) => {\n pushedStream.on('push', (responseHeaders) => {\n // Process response headers\n });\n pushedStream.on('data', (chunk) => { /* handle pushed data */ });\n});\n\nconst req = client.request({ ':path': '/' });\n
",
"type": "module",
"displayName": "Push streams on the client"
},
{
"textRaw": "Supporting the `CONNECT` method",
"name": "supporting_the_`connect`_method",
"desc": "The CONNECT
method is used to allow an HTTP/2 server to be used as a proxy\nfor TCP/IP connections.
A simple TCP Server:
\nconst net = require('node:net');\n\nconst server = net.createServer((socket) => {\n let name = '';\n socket.setEncoding('utf8');\n socket.on('data', (chunk) => name += chunk);\n socket.on('end', () => socket.end(`hello ${name}`));\n});\n\nserver.listen(8000);\n
\nAn HTTP/2 CONNECT proxy:
\nconst http2 = require('node:http2');\nconst { NGHTTP2_REFUSED_STREAM } = http2.constants;\nconst net = require('node:net');\n\nconst proxy = http2.createServer();\nproxy.on('stream', (stream, headers) => {\n if (headers[':method'] !== 'CONNECT') {\n // Only accept CONNECT requests\n stream.close(NGHTTP2_REFUSED_STREAM);\n return;\n }\n const auth = new URL(`tcp://${headers[':authority']}`);\n // It's a very good idea to verify that hostname and port are\n // things this proxy should be connecting to.\n const socket = net.connect(auth.port, auth.hostname, () => {\n stream.respond();\n socket.pipe(stream);\n stream.pipe(socket);\n });\n socket.on('error', (error) => {\n stream.close(http2.constants.NGHTTP2_CONNECT_ERROR);\n });\n});\n\nproxy.listen(8001);\n
\nAn HTTP/2 CONNECT client:
\nconst http2 = require('node:http2');\n\nconst client = http2.connect('http://localhost:8001');\n\n// Must not specify the ':path' and ':scheme' headers\n// for CONNECT requests or an error will be thrown.\nconst req = client.request({\n ':method': 'CONNECT',\n ':authority': 'localhost:8000',\n});\n\nreq.on('response', (headers) => {\n console.log(headers[http2.constants.HTTP2_HEADER_STATUS]);\n});\nlet data = '';\nreq.setEncoding('utf8');\nreq.on('data', (chunk) => data += chunk);\nreq.on('end', () => {\n console.log(`The server says: ${data}`);\n client.close();\n});\nreq.end('Jane');\n
",
"type": "module",
"displayName": "Supporting the `CONNECT` method"
},
{
"textRaw": "The extended `CONNECT` protocol",
"name": "the_extended_`connect`_protocol",
"desc": "RFC 8441 defines an \"Extended CONNECT Protocol\" extension to HTTP/2 that\nmay be used to bootstrap the use of an Http2Stream
using the CONNECT
\nmethod as a tunnel for other communication protocols (such as WebSockets).
The use of the Extended CONNECT Protocol is enabled by HTTP/2 servers by using\nthe enableConnectProtocol
setting:
const http2 = require('node:http2');\nconst settings = { enableConnectProtocol: true };\nconst server = http2.createServer({ settings });\n
\nOnce the client receives the SETTINGS
frame from the server indicating that\nthe extended CONNECT may be used, it may send CONNECT
requests that use the\n':protocol'
HTTP/2 pseudo-header:
const http2 = require('node:http2');\nconst client = http2.connect('http://localhost:8080');\nclient.on('remoteSettings', (settings) => {\n if (settings.enableConnectProtocol) {\n const req = client.request({ ':method': 'CONNECT', ':protocol': 'foo' });\n // ...\n }\n});\n
",
"type": "module",
"displayName": "The extended `CONNECT` protocol"
}
],
"classes": [
{
"textRaw": "Class: `Http2Session`",
"type": "class",
"name": "Http2Session",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"desc": "Instances of the http2.Http2Session
class represent an active communications\nsession between an HTTP/2 client and server. Instances of this class are not\nintended to be constructed directly by user code.
Each Http2Session
instance will exhibit slightly different behaviors\ndepending on whether it is operating as a server or a client. The\nhttp2session.type
property can be used to determine the mode in which an\nHttp2Session
is operating. On the server side, user code should rarely\nhave occasion to work with the Http2Session
object directly, with most\nactions typically taken through interactions with either the Http2Server
or\nHttp2Stream
objects.
User code will not create Http2Session
instances directly. Server-side\nHttp2Session
instances are created by the Http2Server
instance when a\nnew HTTP/2 connection is received. Client-side Http2Session
instances are\ncreated using the http2.connect()
method.
Every Http2Session
instance is associated with exactly one net.Socket
or\ntls.TLSSocket
when it is created. When either the Socket
or the\nHttp2Session
are destroyed, both will be destroyed.
Because of the specific serialization and processing requirements imposed\nby the HTTP/2 protocol, it is not recommended for user code to read data from\nor write data to a Socket
instance bound to a Http2Session
. Doing so can\nput the HTTP/2 session into an indeterminate state causing the session and\nthe socket to become unusable.
Once a Socket
has been bound to an Http2Session
, user code should rely\nsolely on the API of the Http2Session
.
The 'close'
event is emitted once the Http2Session
has been destroyed. Its\nlistener does not expect any arguments.
The 'connect'
event is emitted once the Http2Session
has been successfully\nconnected to the remote peer and communication may begin.
User code will typically not listen for this event directly.
" }, { "textRaw": "Event: `'error'`", "type": "event", "name": "error", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [ { "textRaw": "`error` {Error}", "name": "error", "type": "Error" } ], "desc": "The 'error'
event is emitted when an error occurs during the processing of\nan Http2Session
.
The 'frameError'
event is emitted when an error occurs while attempting to\nsend a frame on the session. If the frame that could not be sent is associated\nwith a specific Http2Stream
, an attempt to emit a 'frameError'
event on the\nHttp2Stream
is made.
If the 'frameError'
event is associated with a stream, the stream will be\nclosed and destroyed immediately following the 'frameError'
event. If the\nevent is not associated with a stream, the Http2Session
will be shut down\nimmediately following the 'frameError'
event.
The 'goaway'
event is emitted when a GOAWAY
frame is received.
The Http2Session
instance will be shut down automatically when the 'goaway'
\nevent is emitted.
The 'localSettings'
event is emitted when an acknowledgment SETTINGS
frame\nhas been received.
When using http2session.settings()
to submit new settings, the modified\nsettings do not take effect until the 'localSettings'
event is emitted.
session.settings({ enablePush: false });\n\nsession.on('localSettings', (settings) => {\n /* Use the new settings */\n});\n
"
},
{
"textRaw": "Event: `'ping'`",
"type": "event",
"name": "ping",
"meta": {
"added": [
"v10.12.0"
],
"changes": []
},
"params": [
{
"textRaw": "`payload` {Buffer} The `PING` frame 8-byte payload",
"name": "payload",
"type": "Buffer",
"desc": "The `PING` frame 8-byte payload"
}
],
"desc": "The 'ping'
event is emitted whenever a PING
frame is received from the\nconnected peer.
The 'remoteSettings'
event is emitted when a new SETTINGS
frame is received\nfrom the connected peer.
session.on('remoteSettings', (settings) => {\n /* Use the new settings */\n});\n
"
},
{
"textRaw": "Event: `'stream'`",
"type": "event",
"name": "stream",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"params": [
{
"textRaw": "`stream` {Http2Stream} A reference to the stream",
"name": "stream",
"type": "Http2Stream",
"desc": "A reference to the stream"
},
{
"textRaw": "`headers` {HTTP/2 Headers Object} An object describing the headers",
"name": "headers",
"type": "HTTP/2 Headers Object",
"desc": "An object describing the headers"
},
{
"textRaw": "`flags` {number} The associated numeric flags",
"name": "flags",
"type": "number",
"desc": "The associated numeric flags"
},
{
"textRaw": "`rawHeaders` {Array} An array containing the raw header names followed by their respective values.",
"name": "rawHeaders",
"type": "Array",
"desc": "An array containing the raw header names followed by their respective values."
}
],
"desc": "The 'stream'
event is emitted when a new Http2Stream
is created.
const http2 = require('node:http2');\nsession.on('stream', (stream, headers, flags) => {\n const method = headers[':method'];\n const path = headers[':path'];\n // ...\n stream.respond({\n ':status': 200,\n 'content-type': 'text/plain; charset=utf-8',\n });\n stream.write('hello ');\n stream.end('world');\n});\n
\nOn the server side, user code will typically not listen for this event directly,\nand would instead register a handler for the 'stream'
event emitted by the\nnet.Server
or tls.Server
instances returned by http2.createServer()
and\nhttp2.createSecureServer()
, respectively, as in the example below:
const http2 = require('node:http2');\n\n// Create an unencrypted HTTP/2 server\nconst server = http2.createServer();\n\nserver.on('stream', (stream, headers) => {\n stream.respond({\n 'content-type': 'text/html; charset=utf-8',\n ':status': 200,\n });\n stream.on('error', (error) => console.error(error));\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(8000);\n
\nEven though HTTP/2 streams and network sockets are not in a 1:1 correspondence,\na network error will destroy each individual stream and must be handled on the\nstream level, as shown above.
" }, { "textRaw": "Event: `'timeout'`", "type": "event", "name": "timeout", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "After the http2session.setTimeout()
method is used to set the timeout period\nfor this Http2Session
, the 'timeout'
event is emitted if there is no\nactivity on the Http2Session
after the configured number of milliseconds.\nIts listener does not expect any arguments.
session.setTimeout(2000);\nsession.on('timeout', () => { /* .. */ });\n
"
}
],
"properties": [
{
"textRaw": "`alpnProtocol` {string|undefined}",
"type": "string|undefined",
"name": "alpnProtocol",
"meta": {
"added": [
"v9.4.0"
],
"changes": []
},
"desc": "Value will be undefined
if the Http2Session
is not yet connected to a\nsocket, h2c
if the Http2Session
is not connected to a TLSSocket
, or\nwill return the value of the connected TLSSocket
's own alpnProtocol
\nproperty.
Will be true
if this Http2Session
instance has been closed, otherwise\nfalse
.
Will be true
if this Http2Session
instance is still connecting, will be set\nto false
before emitting connect
event and/or calling the http2.connect
\ncallback.
Will be true
if this Http2Session
instance has been destroyed and must no\nlonger be used, otherwise false
.
Value is undefined
if the Http2Session
session socket has not yet been\nconnected, true
if the Http2Session
is connected with a TLSSocket
,\nand false
if the Http2Session
is connected to any other kind of socket\nor stream.
A prototype-less object describing the current local settings of this\nHttp2Session
. The local settings are local to this Http2Session
instance.
If the Http2Session
is connected to a TLSSocket
, the originSet
property\nwill return an Array
of origins for which the Http2Session
may be\nconsidered authoritative.
The originSet
property is only available when using a secure TLS connection.
Indicates whether the Http2Session
is currently waiting for acknowledgment of\na sent SETTINGS
frame. Will be true
after calling the\nhttp2session.settings()
method. Will be false
once all sent SETTINGS
\nframes have been acknowledged.
A prototype-less object describing the current remote settings of this\nHttp2Session
. The remote settings are set by the connected HTTP/2 peer.
Returns a Proxy
object that acts as a net.Socket
(or tls.TLSSocket
) but\nlimits available methods to ones safe to use with HTTP/2.
destroy
, emit
, end
, pause
, read
, resume
, and write
will throw\nan error with code ERR_HTTP2_NO_SOCKET_MANIPULATION
. See\nHttp2Session
and Sockets for more information.
setTimeout
method will be called on this Http2Session
.
All other interactions will be routed directly to the socket.
" }, { "textRaw": "`http2session.state`", "name": "state", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Provides miscellaneous information about the current state of the\nHttp2Session
.
effectiveLocalWindowSize
<number> The current local (receive)\nflow control window size for the Http2Session
.effectiveRecvDataLength
<number> The current number of bytes\nthat have been received since the last flow control WINDOW_UPDATE
.nextStreamID
<number> The numeric identifier to be used the\nnext time a new Http2Stream
is created by this Http2Session
.localWindowSize
<number> The number of bytes that the remote peer can\nsend without receiving a WINDOW_UPDATE
.lastProcStreamID
<number> The numeric id of the Http2Stream
\nfor which a HEADERS
or DATA
frame was most recently received.remoteWindowSize
<number> The number of bytes that this Http2Session
\nmay send without receiving a WINDOW_UPDATE
.outboundQueueSize
<number> The number of frames currently within the\noutbound queue for this Http2Session
.deflateDynamicTableSize
<number> The current size in bytes of the\noutbound header compression state table.inflateDynamicTableSize
<number> The current size in bytes of the\ninbound header compression state table.An object describing the current status of this Http2Session
.
The http2session.type
will be equal to\nhttp2.constants.NGHTTP2_SESSION_SERVER
if this Http2Session
instance is a\nserver, and http2.constants.NGHTTP2_SESSION_CLIENT
if the instance is a\nclient.
Gracefully closes the Http2Session
, allowing any existing streams to\ncomplete on their own and preventing new Http2Stream
instances from being\ncreated. Once closed, http2session.destroy()
might be called if there\nare no open Http2Stream
instances.
If specified, the callback
function is registered as a handler for the\n'close'
event.
Immediately terminates the Http2Session
and the associated net.Socket
or\ntls.TLSSocket
.
Once destroyed, the Http2Session
will emit the 'close'
event. If error
\nis not undefined, an 'error'
event will be emitted immediately before the\n'close'
event.
If there are any remaining open Http2Streams
associated with the\nHttp2Session
, those will also be destroyed.
Transmits a GOAWAY
frame to the connected peer without shutting down the\nHttp2Session
.
Sends a PING
frame to the connected HTTP/2 peer. A callback
function must\nbe provided. The method will return true
if the PING
was sent, false
\notherwise.
The maximum number of outstanding (unacknowledged) pings is determined by the\nmaxOutstandingPings
configuration option. The default maximum is 10.
If provided, the payload
must be a Buffer
, TypedArray
, or DataView
\ncontaining 8 bytes of data that will be transmitted with the PING
and\nreturned with the ping acknowledgment.
The callback will be invoked with three arguments: an error argument that will\nbe null
if the PING
was successfully acknowledged, a duration
argument\nthat reports the number of milliseconds elapsed since the ping was sent and the\nacknowledgment was received, and a Buffer
containing the 8-byte PING
\npayload.
session.ping(Buffer.from('abcdefgh'), (err, duration, payload) => {\n if (!err) {\n console.log(`Ping acknowledged in ${duration} milliseconds`);\n console.log(`With payload '${payload.toString()}'`);\n }\n});\n
\nIf the payload
argument is not specified, the default payload will be the\n64-bit timestamp (little endian) marking the start of the PING
duration.
Calls ref()
on this Http2Session
\ninstance's underlying net.Socket
.
Sets the local endpoint's window size.\nThe windowSize
is the total window size to set, not\nthe delta.
const http2 = require('node:http2');\n\nconst server = http2.createServer();\nconst expectedWindowSize = 2 ** 20;\nserver.on('session', (session) => {\n\n // Set local window size to be 2 ** 20\n session.setLocalWindowSize(expectedWindowSize);\n});\n
\nFor http2 clients the proper event is either 'connect'
or 'remoteSettings'
.
Used to set a callback function that is called when there is no activity on\nthe Http2Session
after msecs
milliseconds. The given callback
is\nregistered as a listener on the 'timeout'
event.
Updates the current local settings for this Http2Session
and sends a new\nSETTINGS
frame to the connected HTTP/2 peer.
Once called, the http2session.pendingSettingsAck
property will be true
\nwhile the session is waiting for the remote peer to acknowledge the new\nsettings.
The new settings will not become effective until the SETTINGS
acknowledgment\nis received and the 'localSettings'
event is emitted. It is possible to send\nmultiple SETTINGS
frames while acknowledgment is still pending.
Calls unref()
on this Http2Session
\ninstance's underlying net.Socket
.
Submits an ALTSVC
frame (as defined by RFC 7838) to the connected client.
const http2 = require('node:http2');\n\nconst server = http2.createServer();\nserver.on('session', (session) => {\n // Set altsvc for origin https://example.org:80\n session.altsvc('h2=\":8000\"', 'https://example.org:80');\n});\n\nserver.on('stream', (stream) => {\n // Set altsvc for a specific stream\n stream.session.altsvc('h2=\":8000\"', stream.id);\n});\n
\nSending an ALTSVC
frame with a specific stream ID indicates that the alternate\nservice is associated with the origin of the given Http2Stream
.
The alt
and origin string must contain only ASCII bytes and are\nstrictly interpreted as a sequence of ASCII bytes. The special value 'clear'
\nmay be passed to clear any previously set alternative service for a given\ndomain.
When a string is passed for the originOrStream
argument, it will be parsed as\na URL and the origin will be derived. For instance, the origin for the\nHTTP URL 'https://example.org/foo/bar'
is the ASCII string\n'https://example.org'
. An error will be thrown if either the given string\ncannot be parsed as a URL or if a valid origin cannot be derived.
A URL
object, or any object with an origin
property, may be passed as\noriginOrStream
, in which case the value of the origin
property will be\nused. The value of the origin
property must be a properly serialized\nASCII origin.
Submits an ORIGIN
frame (as defined by RFC 8336) to the connected client\nto advertise the set of origins for which the server is capable of providing\nauthoritative responses.
const http2 = require('node:http2');\nconst options = getSecureOptionsSomehow();\nconst server = http2.createSecureServer(options);\nserver.on('stream', (stream) => {\n stream.respond();\n stream.end('ok');\n});\nserver.on('session', (session) => {\n session.origin('https://example.com', 'https://example.org');\n});\n
\nWhen a string is passed as an origin
, it will be parsed as a URL and the\norigin will be derived. For instance, the origin for the HTTP URL\n'https://example.org/foo/bar'
is the ASCII string\n'https://example.org'
. An error will be thrown if either the given string\ncannot be parsed as a URL or if a valid origin cannot be derived.
A URL
object, or any object with an origin
property, may be passed as\nan origin
, in which case the value of the origin
property will be\nused. The value of the origin
property must be a properly serialized\nASCII origin.
Alternatively, the origins
option may be used when creating a new HTTP/2\nserver using the http2.createSecureServer()
method:
const http2 = require('node:http2');\nconst options = getSecureOptionsSomehow();\noptions.origins = ['https://example.com', 'https://example.org'];\nconst server = http2.createSecureServer(options);\nserver.on('stream', (stream) => {\n stream.respond();\n stream.end('ok');\n});\n
"
}
],
"modules": [
{
"textRaw": "Specifying alternative services",
"name": "specifying_alternative_services",
"desc": "The format of the alt
parameter is strictly defined by RFC 7838 as an\nASCII string containing a comma-delimited list of \"alternative\" protocols\nassociated with a specific host and port.
For example, the value 'h2=\"example.org:81\"'
indicates that the HTTP/2\nprotocol is available on the host 'example.org'
on TCP/IP port 81. The\nhost and port must be contained within the quote (\"
) characters.
Multiple alternatives may be specified, for instance: 'h2=\"example.org:81\", h2=\":82\"'
.
The protocol identifier ('h2'
in the examples) may be any valid\nALPN Protocol ID.
The syntax of these values is not validated by the Node.js implementation and\nare passed through as provided by the user or received from the peer.
", "type": "module", "displayName": "Specifying alternative services" } ] }, { "textRaw": "Class: `ClientHttp2Session`", "type": "class", "name": "ClientHttp2Session", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "The 'altsvc'
event is emitted whenever an ALTSVC
frame is received by\nthe client. The event is emitted with the ALTSVC
value, origin, and stream\nID. If no origin
is provided in the ALTSVC
frame, origin
will\nbe an empty string.
const http2 = require('node:http2');\nconst client = http2.connect('https://example.org');\n\nclient.on('altsvc', (alt, origin, streamId) => {\n console.log(alt);\n console.log(origin);\n console.log(streamId);\n});\n
"
},
{
"textRaw": "Event: `'origin'`",
"type": "event",
"name": "origin",
"meta": {
"added": [
"v10.12.0"
],
"changes": []
},
"params": [
{
"textRaw": "`origins` {string\\[]}",
"name": "origins",
"type": "string\\[]"
}
],
"desc": "The 'origin'
event is emitted whenever an ORIGIN
frame is received by\nthe client. The event is emitted with an array of origin
strings. The\nhttp2session.originSet
will be updated to include the received\norigins.
const http2 = require('node:http2');\nconst client = http2.connect('https://example.org');\n\nclient.on('origin', (origins) => {\n for (let n = 0; n < origins.length; n++)\n console.log(origins[n]);\n});\n
\nThe 'origin'
event is only emitted when using a secure TLS connection.
For HTTP/2 Client Http2Session
instances only, the http2session.request()
\ncreates and returns an Http2Stream
instance that can be used to send an\nHTTP/2 request to the connected server.
When a ClientHttp2Session
is first created, the socket may not yet be\nconnected. if clienthttp2session.request()
is called during this time, the\nactual request will be deferred until the socket is ready to go.\nIf the session
is closed before the actual request be executed, an\nERR_HTTP2_GOAWAY_SESSION
is thrown.
This method is only available if http2session.type
is equal to\nhttp2.constants.NGHTTP2_SESSION_CLIENT
.
const http2 = require('node:http2');\nconst clientSession = http2.connect('https://localhost:1234');\nconst {\n HTTP2_HEADER_PATH,\n HTTP2_HEADER_STATUS,\n} = http2.constants;\n\nconst req = clientSession.request({ [HTTP2_HEADER_PATH]: '/' });\nreq.on('response', (headers) => {\n console.log(headers[HTTP2_HEADER_STATUS]);\n req.on('data', (chunk) => { /* .. */ });\n req.on('end', () => { /* .. */ });\n});\n
\nWhen the options.waitForTrailers
option is set, the 'wantTrailers'
event\nis emitted immediately after queuing the last chunk of payload data to be sent.\nThe http2stream.sendTrailers()
method can then be called to send trailing\nheaders to the peer.
When options.waitForTrailers
is set, the Http2Stream
will not automatically\nclose when the final DATA
frame is transmitted. User code must call either\nhttp2stream.sendTrailers()
or http2stream.close()
to close the\nHttp2Stream
.
When options.signal
is set with an AbortSignal
and then abort
on the\ncorresponding AbortController
is called, the request will emit an 'error'
\nevent with an AbortError
error.
The :method
and :path
pseudo-headers are not specified within headers
,\nthey respectively default to:
:method
= 'GET'
:path
= /
Each instance of the Http2Stream
class represents a bidirectional HTTP/2\ncommunications stream over an Http2Session
instance. Any single Http2Session
\nmay have up to 231-1 Http2Stream
instances over its lifetime.
User code will not construct Http2Stream
instances directly. Rather, these\nare created, managed, and provided to user code through the Http2Session
\ninstance. On the server, Http2Stream
instances are created either in response\nto an incoming HTTP request (and handed off to user code via the 'stream'
\nevent), or in response to a call to the http2stream.pushStream()
method.\nOn the client, Http2Stream
instances are created and returned when either the\nhttp2session.request()
method is called, or in response to an incoming\n'push'
event.
The Http2Stream
class is a base for the ServerHttp2Stream
and\nClientHttp2Stream
classes, each of which is used specifically by either\nthe Server or Client side, respectively.
All Http2Stream
instances are Duplex
streams. The Writable
side of the\nDuplex
is used to send data to the connected peer, while the Readable
side\nis used to receive data sent by the connected peer.
The default text character encoding for an Http2Stream
is UTF-8. When using an\nHttp2Stream
to send text, use the 'content-type'
header to set the character\nencoding.
stream.respond({\n 'content-type': 'text/html; charset=utf-8',\n ':status': 200,\n});\n
",
"modules": [
{
"textRaw": "`Http2Stream` Lifecycle",
"name": "`http2stream`_lifecycle",
"modules": [
{
"textRaw": "Creation",
"name": "creation",
"desc": "On the server side, instances of ServerHttp2Stream
are created either\nwhen:
HEADERS
frame with a previously unused stream ID is received;http2stream.pushStream()
method is called.On the client side, instances of ClientHttp2Stream
are created when the\nhttp2session.request()
method is called.
On the client, the Http2Stream
instance returned by http2session.request()
\nmay not be immediately ready for use if the parent Http2Session
has not yet\nbeen fully established. In such cases, operations called on the Http2Stream
\nwill be buffered until the 'ready'
event is emitted. User code should rarely,\nif ever, need to handle the 'ready'
event directly. The ready status of an\nHttp2Stream
can be determined by checking the value of http2stream.id
. If\nthe value is undefined
, the stream is not yet ready for use.
All Http2Stream
instances are destroyed either when:
RST_STREAM
frame for the stream is received by the connected peer,\nand (for client streams only) pending data has been read.http2stream.close()
method is called, and (for client streams only)\npending data has been read.http2stream.destroy()
or http2session.destroy()
methods are called.When an Http2Stream
instance is destroyed, an attempt will be made to send an\nRST_STREAM
frame to the connected peer.
When the Http2Stream
instance is destroyed, the 'close'
event will\nbe emitted. Because Http2Stream
is an instance of stream.Duplex
, the\n'end'
event will also be emitted if the stream data is currently flowing.\nThe 'error'
event may also be emitted if http2stream.destroy()
was called\nwith an Error
passed as the first argument.
After the Http2Stream
has been destroyed, the http2stream.destroyed
\nproperty will be true
and the http2stream.rstCode
property will specify the\nRST_STREAM
error code. The Http2Stream
instance is no longer usable once\ndestroyed.
The 'aborted'
event is emitted whenever a Http2Stream
instance is\nabnormally aborted in mid-communication.\nIts listener does not expect any arguments.
The 'aborted'
event will only be emitted if the Http2Stream
writable side\nhas not been ended.
The 'close'
event is emitted when the Http2Stream
is destroyed. Once\nthis event is emitted, the Http2Stream
instance is no longer usable.
The HTTP/2 error code used when closing the stream can be retrieved using\nthe http2stream.rstCode
property. If the code is any value other than\nNGHTTP2_NO_ERROR
(0
), an 'error'
event will have also been emitted.
The 'error'
event is emitted when an error occurs during the processing of\nan Http2Stream
.
The 'frameError'
event is emitted when an error occurs while attempting to\nsend a frame. When invoked, the handler function will receive an integer\nargument identifying the frame type, and an integer argument identifying the\nerror code. The Http2Stream
instance will be destroyed immediately after the\n'frameError'
event is emitted.
The 'ready'
event is emitted when the Http2Stream
has been opened, has\nbeen assigned an id
, and can be used. The listener does not expect any\narguments.
The 'timeout'
event is emitted after no activity is received for this\nHttp2Stream
within the number of milliseconds set using\nhttp2stream.setTimeout()
.\nIts listener does not expect any arguments.
The 'trailers'
event is emitted when a block of headers associated with\ntrailing header fields is received. The listener callback is passed the\nHTTP/2 Headers Object and flags associated with the headers.
This event might not be emitted if http2stream.end()
is called\nbefore trailers are received and the incoming data is not being read or\nlistened for.
stream.on('trailers', (headers, flags) => {\n console.log(headers);\n});\n
"
},
{
"textRaw": "Event: `'wantTrailers'`",
"type": "event",
"name": "wantTrailers",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"params": [],
"desc": "The 'wantTrailers'
event is emitted when the Http2Stream
has queued the\nfinal DATA
frame to be sent on a frame and the Http2Stream
is ready to send\ntrailing headers. When initiating a request or response, the waitForTrailers
\noption must be set for this event to be emitted.
Set to true
if the Http2Stream
instance was aborted abnormally. When set,\nthe 'aborted'
event will have been emitted.
This property shows the number of characters currently buffered to be written.\nSee net.Socket.bufferSize
for details.
Set to true
if the Http2Stream
instance has been closed.
Set to true
if the Http2Stream
instance has been destroyed and is no longer\nusable.
Set to true
if the END_STREAM
flag was set in the request or response\nHEADERS frame received, indicating that no additional data should be received\nand the readable side of the Http2Stream
will be closed.
The numeric stream identifier of this Http2Stream
instance. Set to undefined
\nif the stream identifier has not yet been assigned.
Set to true
if the Http2Stream
instance has not yet been assigned a\nnumeric stream identifier.
Set to the RST_STREAM
error code reported when the Http2Stream
is\ndestroyed after either receiving an RST_STREAM
frame from the connected peer,\ncalling http2stream.close()
, or http2stream.destroy()
. Will be\nundefined
if the Http2Stream
has not been closed.
An object containing the outbound headers sent for this Http2Stream
.
An array of objects containing the outbound informational (additional) headers\nsent for this Http2Stream
.
An object containing the outbound trailers sent for this HttpStream
.
A reference to the Http2Session
instance that owns this Http2Stream
. The\nvalue will be undefined
after the Http2Stream
instance is destroyed.
Provides miscellaneous information about the current state of the\nHttp2Stream
.
localWindowSize
<number> The number of bytes the connected peer may send\nfor this Http2Stream
without receiving a WINDOW_UPDATE
.state
<number> A flag indicating the low-level current state of the\nHttp2Stream
as determined by nghttp2
.localClose
<number> 1
if this Http2Stream
has been closed locally.remoteClose
<number> 1
if this Http2Stream
has been closed\nremotely.sumDependencyWeight
<number> The sum weight of all Http2Stream
\ninstances that depend on this Http2Stream
as specified using\nPRIORITY
frames.weight
<number> The priority weight of this Http2Stream
.A current state of this Http2Stream
.
Closes the Http2Stream
instance by sending an RST_STREAM
frame to the\nconnected HTTP/2 peer.
Updates the priority for this Http2Stream
instance.
const http2 = require('node:http2');\nconst client = http2.connect('http://example.org:8000');\nconst { NGHTTP2_CANCEL } = http2.constants;\nconst req = client.request({ ':path': '/' });\n\n// Cancel the stream if there's no activity after 5 seconds\nreq.setTimeout(5000, () => req.close(NGHTTP2_CANCEL));\n
"
},
{
"textRaw": "`http2stream.sendTrailers(headers)`",
"type": "method",
"name": "sendTrailers",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`headers` {HTTP/2 Headers Object}",
"name": "headers",
"type": "HTTP/2 Headers Object"
}
]
}
],
"desc": "Sends a trailing HEADERS
frame to the connected HTTP/2 peer. This method\nwill cause the Http2Stream
to be immediately closed and must only be\ncalled after the 'wantTrailers'
event has been emitted. When sending a\nrequest or sending a response, the options.waitForTrailers
option must be set\nin order to keep the Http2Stream
open after the final DATA
frame so that\ntrailers can be sent.
const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond(undefined, { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ xyz: 'abc' });\n });\n stream.end('Hello World');\n});\n
\nThe HTTP/1 specification forbids trailers from containing HTTP/2 pseudo-header\nfields (e.g. ':method'
, ':path'
, etc).
The ClientHttp2Stream
class is an extension of Http2Stream
that is\nused exclusively on HTTP/2 Clients. Http2Stream
instances on the client\nprovide events such as 'response'
and 'push'
that are only relevant on\nthe client.
Emitted when the server sends a 100 Continue
status, usually because\nthe request contained Expect: 100-continue
. This is an instruction that\nthe client should send the request body.
The 'headers'
event is emitted when an additional block of headers is received\nfor a stream, such as when a block of 1xx
informational headers is received.\nThe listener callback is passed the HTTP/2 Headers Object and flags\nassociated with the headers.
stream.on('headers', (headers, flags) => {\n console.log(headers);\n});\n
"
},
{
"textRaw": "Event: `'push'`",
"type": "event",
"name": "push",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"params": [
{
"textRaw": "`headers` {HTTP/2 Headers Object}",
"name": "headers",
"type": "HTTP/2 Headers Object"
},
{
"textRaw": "`flags` {number}",
"name": "flags",
"type": "number"
}
],
"desc": "The 'push'
event is emitted when response headers for a Server Push stream\nare received. The listener callback is passed the HTTP/2 Headers Object and\nflags associated with the headers.
stream.on('push', (headers, flags) => {\n console.log(headers);\n});\n
"
},
{
"textRaw": "Event: `'response'`",
"type": "event",
"name": "response",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"params": [
{
"textRaw": "`headers` {HTTP/2 Headers Object}",
"name": "headers",
"type": "HTTP/2 Headers Object"
},
{
"textRaw": "`flags` {number}",
"name": "flags",
"type": "number"
}
],
"desc": "The 'response'
event is emitted when a response HEADERS
frame has been\nreceived for this stream from the connected HTTP/2 server. The listener is\ninvoked with two arguments: an Object
containing the received\nHTTP/2 Headers Object, and flags associated with the headers.
const http2 = require('node:http2');\nconst client = http2.connect('https://localhost');\nconst req = client.request({ ':path': '/' });\nreq.on('response', (headers, flags) => {\n console.log(headers[':status']);\n});\n
"
}
]
},
{
"textRaw": "Class: `ServerHttp2Stream`",
"type": "class",
"name": "ServerHttp2Stream",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"desc": "The ServerHttp2Stream
class is an extension of Http2Stream
that is\nused exclusively on HTTP/2 Servers. Http2Stream
instances on the server\nprovide additional methods such as http2stream.pushStream()
and\nhttp2stream.respond()
that are only relevant on the server.
Sends an additional informational HEADERS
frame to the connected HTTP/2 peer.
Initiates a push stream. The callback is invoked with the new Http2Stream
\ninstance created for the push stream passed as the second argument, or an\nError
passed as the first argument.
const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 });\n stream.pushStream({ ':path': '/' }, (err, pushStream, headers) => {\n if (err) throw err;\n pushStream.respond({ ':status': 200 });\n pushStream.end('some pushed data');\n });\n stream.end('some data');\n});\n
\nSetting the weight of a push stream is not allowed in the HEADERS
frame. Pass\na weight
value to http2stream.priority
with the silent
option set to\ntrue
to enable server-side bandwidth balancing between concurrent streams.
Calling http2stream.pushStream()
from within a pushed stream is not permitted\nand will throw an error.
const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 });\n stream.end('some data');\n});\n
\nInitiates a response. When the options.waitForTrailers
option is set, the\n'wantTrailers'
event will be emitted immediately after queuing the last chunk\nof payload data to be sent. The http2stream.sendTrailers()
method can then be\nused to sent trailing header fields to the peer.
When options.waitForTrailers
is set, the Http2Stream
will not automatically\nclose when the final DATA
frame is transmitted. User code must call either\nhttp2stream.sendTrailers()
or http2stream.close()
to close the\nHttp2Stream
.
const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 }, { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ ABC: 'some value to send' });\n });\n stream.end('some data');\n});\n
"
},
{
"textRaw": "`http2stream.respondWithFD(fd[, headers[, options]])`",
"type": "method",
"name": "respondWithFD",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": [
"v14.5.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/33160",
"description": "Allow explicitly setting date headers."
},
{
"version": "v12.12.0",
"pr-url": "https://github.com/nodejs/node/pull/29876",
"description": "The `fd` option may now be a `FileHandle`."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18936",
"description": "Any readable file descriptor, not necessarily for a regular file, is supported now."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`fd` {number|FileHandle} A readable file descriptor.",
"name": "fd",
"type": "number|FileHandle",
"desc": "A readable file descriptor."
},
{
"textRaw": "`headers` {HTTP/2 Headers Object}",
"name": "headers",
"type": "HTTP/2 Headers Object"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`statCheck` {Function}",
"name": "statCheck",
"type": "Function"
},
{
"textRaw": "`waitForTrailers` {boolean} When `true`, the `Http2Stream` will emit the `'wantTrailers'` event after the final `DATA` frame has been sent.",
"name": "waitForTrailers",
"type": "boolean",
"desc": "When `true`, the `Http2Stream` will emit the `'wantTrailers'` event after the final `DATA` frame has been sent."
},
{
"textRaw": "`offset` {number} The offset position at which to begin reading.",
"name": "offset",
"type": "number",
"desc": "The offset position at which to begin reading."
},
{
"textRaw": "`length` {number} The amount of data from the fd to send.",
"name": "length",
"type": "number",
"desc": "The amount of data from the fd to send."
}
]
}
]
}
],
"desc": "Initiates a response whose data is read from the given file descriptor. No\nvalidation is performed on the given file descriptor. If an error occurs while\nattempting to read data using the file descriptor, the Http2Stream
will be\nclosed using an RST_STREAM
frame using the standard INTERNAL_ERROR
code.
When used, the Http2Stream
object's Duplex
interface will be closed\nautomatically.
const http2 = require('node:http2');\nconst fs = require('node:fs');\n\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n const fd = fs.openSync('/some/file', 'r');\n\n const stat = fs.fstatSync(fd);\n const headers = {\n 'content-length': stat.size,\n 'last-modified': stat.mtime.toUTCString(),\n 'content-type': 'text/plain; charset=utf-8',\n };\n stream.respondWithFD(fd, headers);\n stream.on('close', () => fs.closeSync(fd));\n});\n
\nThe optional options.statCheck
function may be specified to give user code\nan opportunity to set additional content headers based on the fs.Stat
details\nof the given fd. If the statCheck
function is provided, the\nhttp2stream.respondWithFD()
method will perform an fs.fstat()
call to\ncollect details on the provided file descriptor.
The offset
and length
options may be used to limit the response to a\nspecific range subset. This can be used, for instance, to support HTTP Range\nrequests.
The file descriptor or FileHandle
is not closed when the stream is closed,\nso it will need to be closed manually once it is no longer needed.\nUsing the same file descriptor concurrently for multiple streams\nis not supported and may result in data loss. Re-using a file descriptor\nafter a stream has finished is supported.
When the options.waitForTrailers
option is set, the 'wantTrailers'
event\nwill be emitted immediately after queuing the last chunk of payload data to be\nsent. The http2stream.sendTrailers()
method can then be used to sent trailing\nheader fields to the peer.
When options.waitForTrailers
is set, the Http2Stream
will not automatically\nclose when the final DATA
frame is transmitted. User code must call either\nhttp2stream.sendTrailers()
or http2stream.close()
to close the\nHttp2Stream
.
const http2 = require('node:http2');\nconst fs = require('node:fs');\n\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n const fd = fs.openSync('/some/file', 'r');\n\n const stat = fs.fstatSync(fd);\n const headers = {\n 'content-length': stat.size,\n 'last-modified': stat.mtime.toUTCString(),\n 'content-type': 'text/plain; charset=utf-8',\n };\n stream.respondWithFD(fd, headers, { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ ABC: 'some value to send' });\n });\n\n stream.on('close', () => fs.closeSync(fd));\n});\n
"
},
{
"textRaw": "`http2stream.respondWithFile(path[, headers[, options]])`",
"type": "method",
"name": "respondWithFile",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": [
"v14.5.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/33160",
"description": "Allow explicitly setting date headers."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18936",
"description": "Any readable file, not necessarily a regular file, is supported now."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`headers` {HTTP/2 Headers Object}",
"name": "headers",
"type": "HTTP/2 Headers Object"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`statCheck` {Function}",
"name": "statCheck",
"type": "Function"
},
{
"textRaw": "`onError` {Function} Callback function invoked in the case of an error before send.",
"name": "onError",
"type": "Function",
"desc": "Callback function invoked in the case of an error before send."
},
{
"textRaw": "`waitForTrailers` {boolean} When `true`, the `Http2Stream` will emit the `'wantTrailers'` event after the final `DATA` frame has been sent.",
"name": "waitForTrailers",
"type": "boolean",
"desc": "When `true`, the `Http2Stream` will emit the `'wantTrailers'` event after the final `DATA` frame has been sent."
},
{
"textRaw": "`offset` {number} The offset position at which to begin reading.",
"name": "offset",
"type": "number",
"desc": "The offset position at which to begin reading."
},
{
"textRaw": "`length` {number} The amount of data from the fd to send.",
"name": "length",
"type": "number",
"desc": "The amount of data from the fd to send."
}
]
}
]
}
],
"desc": "Sends a regular file as the response. The path
must specify a regular file\nor an 'error'
event will be emitted on the Http2Stream
object.
When used, the Http2Stream
object's Duplex
interface will be closed\nautomatically.
The optional options.statCheck
function may be specified to give user code\nan opportunity to set additional content headers based on the fs.Stat
details\nof the given file:
If an error occurs while attempting to read the file data, the Http2Stream
\nwill be closed using an RST_STREAM
frame using the standard INTERNAL_ERROR
\ncode. If the onError
callback is defined, then it will be called. Otherwise\nthe stream will be destroyed.
Example using a file path:
\nconst http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n function statCheck(stat, headers) {\n headers['last-modified'] = stat.mtime.toUTCString();\n }\n\n function onError(err) {\n // stream.respond() can throw if the stream has been destroyed by\n // the other side.\n try {\n if (err.code === 'ENOENT') {\n stream.respond({ ':status': 404 });\n } else {\n stream.respond({ ':status': 500 });\n }\n } catch (err) {\n // Perform actual error handling.\n console.error(err);\n }\n stream.end();\n }\n\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain; charset=utf-8' },\n { statCheck, onError });\n});\n
\nThe options.statCheck
function may also be used to cancel the send operation\nby returning false
. For instance, a conditional request may check the stat\nresults to determine if the file has been modified to return an appropriate\n304
response:
const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n function statCheck(stat, headers) {\n // Check the stat here...\n stream.respond({ ':status': 304 });\n return false; // Cancel the send operation\n }\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain; charset=utf-8' },\n { statCheck });\n});\n
\nThe content-length
header field will be automatically set.
The offset
and length
options may be used to limit the response to a\nspecific range subset. This can be used, for instance, to support HTTP Range\nrequests.
The options.onError
function may also be used to handle all the errors\nthat could happen before the delivery of the file is initiated. The\ndefault behavior is to destroy the stream.
When the options.waitForTrailers
option is set, the 'wantTrailers'
event\nwill be emitted immediately after queuing the last chunk of payload data to be\nsent. The http2stream.sendTrailers()
method can then be used to sent trailing\nheader fields to the peer.
When options.waitForTrailers
is set, the Http2Stream
will not automatically\nclose when the final DATA
frame is transmitted. User code must call either\nhttp2stream.sendTrailers()
or http2stream.close()
to close the\nHttp2Stream
.
const http2 = require('node:http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain; charset=utf-8' },\n { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ ABC: 'some value to send' });\n });\n});\n
"
}
],
"properties": [
{
"textRaw": "`headersSent` {boolean}",
"type": "boolean",
"name": "headersSent",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"desc": "True if headers were sent, false otherwise (read-only).
" }, { "textRaw": "`pushAllowed` {boolean}", "type": "boolean", "name": "pushAllowed", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Read-only property mapped to the SETTINGS_ENABLE_PUSH
flag of the remote\nclient's most recent SETTINGS
frame. Will be true
if the remote peer\naccepts push streams, false
otherwise. Settings are the same for every\nHttp2Stream
in the same Http2Session
.
Instances of Http2Server
are created using the http2.createServer()
\nfunction. The Http2Server
class is not exported directly by the\nnode:http2
module.
If a 'request'
listener is registered or http2.createServer()
is\nsupplied a callback function, the 'checkContinue'
event is emitted each time\na request with an HTTP Expect: 100-continue
is received. If this event is\nnot listened for, the server will automatically respond with a status\n100 Continue
as appropriate.
Handling this event involves calling response.writeContinue()
if the\nclient should continue to send the request body, or generating an appropriate\nHTTP response (e.g. 400 Bad Request) if the client should not continue to send\nthe request body.
When this event is emitted and handled, the 'request'
event will\nnot be emitted.
This event is emitted when a new TCP stream is established. socket
is\ntypically an object of type net.Socket
. Usually users will not want to\naccess this event.
This event can also be explicitly emitted by users to inject connections\ninto the HTTP server. In that case, any Duplex
stream can be passed.
Emitted each time there is a request. There may be multiple requests\nper session. See the Compatibility API.
" }, { "textRaw": "Event: `'session'`", "type": "event", "name": "session", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [ { "textRaw": "`session` {ServerHttp2Session}", "name": "session", "type": "ServerHttp2Session" } ], "desc": "The 'session'
event is emitted when a new Http2Session
is created by the\nHttp2Server
.
The 'sessionError'
event is emitted when an 'error'
event is emitted by\nan Http2Session
object associated with the Http2Server
.
The 'stream'
event is emitted when a 'stream'
event has been emitted by\nan Http2Session
associated with the server.
See also Http2Session
's 'stream'
event.
const http2 = require('node:http2');\nconst {\n HTTP2_HEADER_METHOD,\n HTTP2_HEADER_PATH,\n HTTP2_HEADER_STATUS,\n HTTP2_HEADER_CONTENT_TYPE,\n} = http2.constants;\n\nconst server = http2.createServer();\nserver.on('stream', (stream, headers, flags) => {\n const method = headers[HTTP2_HEADER_METHOD];\n const path = headers[HTTP2_HEADER_PATH];\n // ...\n stream.respond({\n [HTTP2_HEADER_STATUS]: 200,\n [HTTP2_HEADER_CONTENT_TYPE]: 'text/plain; charset=utf-8',\n });\n stream.write('hello ');\n stream.end('world');\n});\n
"
},
{
"textRaw": "Event: `'timeout'`",
"type": "event",
"name": "timeout",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": "v13.0.0",
"pr-url": "https://github.com/nodejs/node/pull/27558",
"description": "The default timeout changed from 120s to 0 (no timeout)."
}
]
},
"params": [],
"desc": "The 'timeout'
event is emitted when there is no activity on the Server for\na given number of milliseconds set using http2server.setTimeout()
.\nDefault: 0 (no timeout)
Stops the server from establishing new sessions. This does not prevent new\nrequest streams from being created due to the persistent nature of HTTP/2\nsessions. To gracefully shut down the server, call http2session.close()
on\nall active sessions.
If callback
is provided, it is not invoked until all active sessions have been\nclosed, although the server has already stopped allowing new sessions. See\nnet.Server.close()
for more details.
Calls server.close()
and returns a promise that fulfills when the\nserver has closed.
Used to set the timeout value for http2 server requests,\nand sets a callback function that is called when there is no activity\non the Http2Server
after msecs
milliseconds.
The given callback is registered as a listener on the 'timeout'
event.
In case if callback
is not a function, a new ERR_INVALID_ARG_TYPE
\nerror will be thrown.
Used to update the server with the provided settings.
\nThrows ERR_HTTP2_INVALID_SETTING_VALUE
for invalid settings
values.
Throws ERR_INVALID_ARG_TYPE
for invalid settings
argument.
The number of milliseconds of inactivity before a socket is presumed\nto have timed out.
\nA value of 0
will disable the timeout behavior on incoming connections.
The socket timeout logic is set up on connection, so changing this\nvalue only affects new connections to the server, not any existing connections.
", "shortDesc": "Timeout in milliseconds." } ] }, { "textRaw": "Class: `Http2SecureServer`", "type": "class", "name": "Http2SecureServer", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Instances of Http2SecureServer
are created using the\nhttp2.createSecureServer()
function. The Http2SecureServer
class is not\nexported directly by the node:http2
module.
If a 'request'
listener is registered or http2.createSecureServer()
\nis supplied a callback function, the 'checkContinue'
event is emitted each\ntime a request with an HTTP Expect: 100-continue
is received. If this event\nis not listened for, the server will automatically respond with a status\n100 Continue
as appropriate.
Handling this event involves calling response.writeContinue()
if the\nclient should continue to send the request body, or generating an appropriate\nHTTP response (e.g. 400 Bad Request) if the client should not continue to send\nthe request body.
When this event is emitted and handled, the 'request'
event will\nnot be emitted.
This event is emitted when a new TCP stream is established, before the TLS\nhandshake begins. socket
is typically an object of type net.Socket
.\nUsually users will not want to access this event.
This event can also be explicitly emitted by users to inject connections\ninto the HTTP server. In that case, any Duplex
stream can be passed.
Emitted each time there is a request. There may be multiple requests\nper session. See the Compatibility API.
" }, { "textRaw": "Event: `'session'`", "type": "event", "name": "session", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [ { "textRaw": "`session` {ServerHttp2Session}", "name": "session", "type": "ServerHttp2Session" } ], "desc": "The 'session'
event is emitted when a new Http2Session
is created by the\nHttp2SecureServer
.
The 'sessionError'
event is emitted when an 'error'
event is emitted by\nan Http2Session
object associated with the Http2SecureServer
.
The 'stream'
event is emitted when a 'stream'
event has been emitted by\nan Http2Session
associated with the server.
See also Http2Session
's 'stream'
event.
const http2 = require('node:http2');\nconst {\n HTTP2_HEADER_METHOD,\n HTTP2_HEADER_PATH,\n HTTP2_HEADER_STATUS,\n HTTP2_HEADER_CONTENT_TYPE,\n} = http2.constants;\n\nconst options = getOptionsSomehow();\n\nconst server = http2.createSecureServer(options);\nserver.on('stream', (stream, headers, flags) => {\n const method = headers[HTTP2_HEADER_METHOD];\n const path = headers[HTTP2_HEADER_PATH];\n // ...\n stream.respond({\n [HTTP2_HEADER_STATUS]: 200,\n [HTTP2_HEADER_CONTENT_TYPE]: 'text/plain; charset=utf-8',\n });\n stream.write('hello ');\n stream.end('world');\n});\n
"
},
{
"textRaw": "Event: `'timeout'`",
"type": "event",
"name": "timeout",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"params": [],
"desc": "The 'timeout'
event is emitted when there is no activity on the Server for\na given number of milliseconds set using http2secureServer.setTimeout()
.\nDefault: 2 minutes.
The 'unknownProtocol'
event is emitted when a connecting client fails to\nnegotiate an allowed protocol (i.e. HTTP/2 or HTTP/1.1). The event handler\nreceives the socket for handling. If no listener is registered for this event,\nthe connection is terminated. A timeout may be specified using the\n'unknownProtocolTimeout'
option passed to http2.createSecureServer()
.
In earlier versions of Node.js, this event would be emitted if allowHTTP1
is\nfalse
and, during the TLS handshake, the client either does not send an ALPN\nextension or sends an ALPN extension that does not include HTTP/2 (h2
). Newer\nversions of Node.js only emit this event if allowHTTP1
is false
and the\nclient does not send an ALPN extension. If the client sends an ALPN extension\nthat does not include HTTP/2 (or HTTP/1.1 if allowHTTP1
is true
), the TLS\nhandshake will fail and no secure connection will be established.
See the Compatibility API.
" } ], "methods": [ { "textRaw": "`server.close([callback])`", "type": "method", "name": "close", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function" } ] } ], "desc": "Stops the server from establishing new sessions. This does not prevent new\nrequest streams from being created due to the persistent nature of HTTP/2\nsessions. To gracefully shut down the server, call http2session.close()
on\nall active sessions.
If callback
is provided, it is not invoked until all active sessions have been\nclosed, although the server has already stopped allowing new sessions. See\ntls.Server.close()
for more details.
Used to set the timeout value for http2 secure server requests,\nand sets a callback function that is called when there is no activity\non the Http2SecureServer
after msecs
milliseconds.
The given callback is registered as a listener on the 'timeout'
event.
In case if callback
is not a function, a new ERR_INVALID_ARG_TYPE
\nerror will be thrown.
Used to update the server with the provided settings.
\nThrows ERR_HTTP2_INVALID_SETTING_VALUE
for invalid settings
values.
Throws ERR_INVALID_ARG_TYPE
for invalid settings
argument.
The number of milliseconds of inactivity before a socket is presumed\nto have timed out.
\nA value of 0
will disable the timeout behavior on incoming connections.
The socket timeout logic is set up on connection, so changing this\nvalue only affects new connections to the server, not any existing connections.
", "shortDesc": "Timeout in milliseconds." } ] } ], "methods": [ { "textRaw": "`http2.createServer([options][, onRequestHandler])`", "type": "method", "name": "createServer", "meta": { "added": [ "v8.4.0" ], "changes": [ { "version": [ "v15.10.0", "v14.16.0", "v12.21.0", "v10.24.0" ], "pr-url": "https://github.com/nodejs-private/node-private/pull/246", "description": "Added `unknownProtocolTimeout` option with a default of 10000." }, { "version": [ "v14.4.0", "v12.18.0", "v10.21.0" ], "commit": "3948830ce6408be620b09a70bf66158623022af0", "pr-url": "https://github.com/nodejs-private/node-private/pull/204", "description": "Added `maxSettings` option with a default of 32." }, { "version": [ "v13.3.0", "v12.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/30534", "description": "Added `maxSessionRejectedStreams` option with a default of 100." }, { "version": [ "v13.3.0", "v12.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/30534", "description": "Added `maxSessionInvalidFrames` option with a default of 1000." }, { "version": "v13.0.0", "pr-url": "https://github.com/nodejs/node/pull/29144", "description": "The `PADDING_STRATEGY_CALLBACK` has been made equivalent to providing `PADDING_STRATEGY_ALIGNED` and `selectPadding` has been removed." }, { "version": "v12.4.0", "pr-url": "https://github.com/nodejs/node/pull/27782", "description": "The `options` parameter now supports `net.createServer()` options." }, { "version": "v9.6.0", "pr-url": "https://github.com/nodejs/node/pull/15752", "description": "Added the `Http1IncomingMessage` and `Http1ServerResponse` option." }, { "version": "v8.9.3", "pr-url": "https://github.com/nodejs/node/pull/17105", "description": "Added the `maxOutstandingPings` option with a default limit of 10." }, { "version": "v8.9.3", "pr-url": "https://github.com/nodejs/node/pull/16676", "description": "Added the `maxHeaderListPairs` option with a default limit of 128 header pairs." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Http2Server}", "name": "return", "type": "Http2Server" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`maxDeflateDynamicTableSize` {number} Sets the maximum dynamic table size for deflating header fields. **Default:** `4Kib`.", "name": "maxDeflateDynamicTableSize", "type": "number", "default": "`4Kib`", "desc": "Sets the maximum dynamic table size for deflating header fields." }, { "textRaw": "`maxSettings` {number} Sets the maximum number of settings entries per `SETTINGS` frame. The minimum value allowed is `1`. **Default:** `32`.", "name": "maxSettings", "type": "number", "default": "`32`", "desc": "Sets the maximum number of settings entries per `SETTINGS` frame. The minimum value allowed is `1`." }, { "textRaw": "`maxSessionMemory`{number} Sets the maximum memory that the `Http2Session` is permitted to use. The value is expressed in terms of number of megabytes, e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. This is a credit based limit, existing `Http2Stream`s may cause this limit to be exceeded, but new `Http2Stream` instances will be rejected while this limit is exceeded. The current number of `Http2Stream` sessions, the current memory use of the header compression tables, current data queued to be sent, and unacknowledged `PING` and `SETTINGS` frames are all counted towards the current limit. **Default:** `10`.", "name": "maxSessionMemory", "type": "number", "default": "`10`", "desc": "Sets the maximum memory that the `Http2Session` is permitted to use. The value is expressed in terms of number of megabytes, e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. This is a credit based limit, existing `Http2Stream`s may cause this limit to be exceeded, but new `Http2Stream` instances will be rejected while this limit is exceeded. The current number of `Http2Stream` sessions, the current memory use of the header compression tables, current data queued to be sent, and unacknowledged `PING` and `SETTINGS` frames are all counted towards the current limit." }, { "textRaw": "`maxHeaderListPairs` {number} Sets the maximum number of header entries. This is similar to [`server.maxHeadersCount`][] or [`request.maxHeadersCount`][] in the `node:http` module. The minimum value is `4`. **Default:** `128`.", "name": "maxHeaderListPairs", "type": "number", "default": "`128`", "desc": "Sets the maximum number of header entries. This is similar to [`server.maxHeadersCount`][] or [`request.maxHeadersCount`][] in the `node:http` module. The minimum value is `4`." }, { "textRaw": "`maxOutstandingPings` {number} Sets the maximum number of outstanding, unacknowledged pings. **Default:** `10`.", "name": "maxOutstandingPings", "type": "number", "default": "`10`", "desc": "Sets the maximum number of outstanding, unacknowledged pings." }, { "textRaw": "`maxSendHeaderBlockLength` {number} Sets the maximum allowed size for a serialized, compressed block of headers. Attempts to send headers that exceed this limit will result in a `'frameError'` event being emitted and the stream being closed and destroyed. While this sets the maximum allowed size to the entire block of headers, `nghttp2` (the internal http2 library) has a limit of `65536` for each decompressed key/value pair.", "name": "maxSendHeaderBlockLength", "type": "number", "desc": "Sets the maximum allowed size for a serialized, compressed block of headers. Attempts to send headers that exceed this limit will result in a `'frameError'` event being emitted and the stream being closed and destroyed. While this sets the maximum allowed size to the entire block of headers, `nghttp2` (the internal http2 library) has a limit of `65536` for each decompressed key/value pair." }, { "textRaw": "`paddingStrategy` {number} The strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames. **Default:** `http2.constants.PADDING_STRATEGY_NONE`. Value may be one of:", "name": "paddingStrategy", "type": "number", "default": "`http2.constants.PADDING_STRATEGY_NONE`. Value may be one of:", "desc": "The strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames.", "options": [ { "textRaw": "`http2.constants.PADDING_STRATEGY_NONE`: No padding is applied.", "name": "http2.constants.PADDING_STRATEGY_NONE", "desc": "No padding is applied." }, { "textRaw": "`http2.constants.PADDING_STRATEGY_MAX`: The maximum amount of padding, determined by the internal implementation, is applied.", "name": "http2.constants.PADDING_STRATEGY_MAX", "desc": "The maximum amount of padding, determined by the internal implementation, is applied." }, { "textRaw": "`http2.constants.PADDING_STRATEGY_ALIGNED`: Attempts to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, there is a maximum allowed number of padding bytes that is determined by current flow control state and settings. If this maximum is less than the calculated amount needed to ensure alignment, the maximum is used and the total frame length is not necessarily aligned at 8 bytes.", "name": "http2.constants.PADDING_STRATEGY_ALIGNED", "desc": "Attempts to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, there is a maximum allowed number of padding bytes that is determined by current flow control state and settings. If this maximum is less than the calculated amount needed to ensure alignment, the maximum is used and the total frame length is not necessarily aligned at 8 bytes." } ] }, { "textRaw": "`peerMaxConcurrentStreams` {number} Sets the maximum number of concurrent streams for the remote peer as if a `SETTINGS` frame had been received. Will be overridden if the remote peer sets its own value for `maxConcurrentStreams`. **Default:** `100`.", "name": "peerMaxConcurrentStreams", "type": "number", "default": "`100`", "desc": "Sets the maximum number of concurrent streams for the remote peer as if a `SETTINGS` frame had been received. Will be overridden if the remote peer sets its own value for `maxConcurrentStreams`." }, { "textRaw": "`maxSessionInvalidFrames` {integer} Sets the maximum number of invalid frames that will be tolerated before the session is closed. **Default:** `1000`.", "name": "maxSessionInvalidFrames", "type": "integer", "default": "`1000`", "desc": "Sets the maximum number of invalid frames that will be tolerated before the session is closed." }, { "textRaw": "`maxSessionRejectedStreams` {integer} Sets the maximum number of rejected upon creation streams that will be tolerated before the session is closed. Each rejection is associated with an `NGHTTP2_ENHANCE_YOUR_CALM` error that should tell the peer to not open any more streams, continuing to open streams is therefore regarded as a sign of a misbehaving peer. **Default:** `100`.", "name": "maxSessionRejectedStreams", "type": "integer", "default": "`100`", "desc": "Sets the maximum number of rejected upon creation streams that will be tolerated before the session is closed. Each rejection is associated with an `NGHTTP2_ENHANCE_YOUR_CALM` error that should tell the peer to not open any more streams, continuing to open streams is therefore regarded as a sign of a misbehaving peer." }, { "textRaw": "`settings` {HTTP/2 Settings Object} The initial settings to send to the remote peer upon connection.", "name": "settings", "type": "HTTP/2 Settings Object", "desc": "The initial settings to send to the remote peer upon connection." }, { "textRaw": "`remoteCustomSettings` {Array} The array of integer values determines the settings types, which are included in the `CustomSettings`-property of the received remoteSettings. Please see the `CustomSettings`-property of the `Http2Settings` object for more information, on the allowed setting types.", "name": "remoteCustomSettings", "type": "Array", "desc": "The array of integer values determines the settings types, which are included in the `CustomSettings`-property of the received remoteSettings. Please see the `CustomSettings`-property of the `Http2Settings` object for more information, on the allowed setting types." }, { "textRaw": "`Http1IncomingMessage` {http.IncomingMessage} Specifies the `IncomingMessage` class to used for HTTP/1 fallback. Useful for extending the original `http.IncomingMessage`. **Default:** `http.IncomingMessage`.", "name": "Http1IncomingMessage", "type": "http.IncomingMessage", "default": "`http.IncomingMessage`", "desc": "Specifies the `IncomingMessage` class to used for HTTP/1 fallback. Useful for extending the original `http.IncomingMessage`." }, { "textRaw": "`Http1ServerResponse` {http.ServerResponse} Specifies the `ServerResponse` class to used for HTTP/1 fallback. Useful for extending the original `http.ServerResponse`. **Default:** `http.ServerResponse`.", "name": "Http1ServerResponse", "type": "http.ServerResponse", "default": "`http.ServerResponse`", "desc": "Specifies the `ServerResponse` class to used for HTTP/1 fallback. Useful for extending the original `http.ServerResponse`." }, { "textRaw": "`Http2ServerRequest` {http2.Http2ServerRequest} Specifies the `Http2ServerRequest` class to use. Useful for extending the original `Http2ServerRequest`. **Default:** `Http2ServerRequest`.", "name": "Http2ServerRequest", "type": "http2.Http2ServerRequest", "default": "`Http2ServerRequest`", "desc": "Specifies the `Http2ServerRequest` class to use. Useful for extending the original `Http2ServerRequest`." }, { "textRaw": "`Http2ServerResponse` {http2.Http2ServerResponse} Specifies the `Http2ServerResponse` class to use. Useful for extending the original `Http2ServerResponse`. **Default:** `Http2ServerResponse`.", "name": "Http2ServerResponse", "type": "http2.Http2ServerResponse", "default": "`Http2ServerResponse`", "desc": "Specifies the `Http2ServerResponse` class to use. Useful for extending the original `Http2ServerResponse`." }, { "textRaw": "`unknownProtocolTimeout` {number} Specifies a timeout in milliseconds that a server should wait when an [`'unknownProtocol'`][] is emitted. If the socket has not been destroyed by that time the server will destroy it. **Default:** `10000`.", "name": "unknownProtocolTimeout", "type": "number", "default": "`10000`", "desc": "Specifies a timeout in milliseconds that a server should wait when an [`'unknownProtocol'`][] is emitted. If the socket has not been destroyed by that time the server will destroy it." }, { "textRaw": "...: Any [`net.createServer()`][] option can be provided.", "name": "...", "desc": "Any [`net.createServer()`][] option can be provided." } ] }, { "textRaw": "`onRequestHandler` {Function} See [Compatibility API][]", "name": "onRequestHandler", "type": "Function", "desc": "See [Compatibility API][]" } ] } ], "desc": "Returns a net.Server
instance that creates and manages Http2Session
\ninstances.
Since there are no browsers known that support\nunencrypted HTTP/2, the use of\nhttp2.createSecureServer()
is necessary when communicating\nwith browser clients.
const http2 = require('node:http2');\n\n// Create an unencrypted HTTP/2 server.\n// Since there are no browsers known that support\n// unencrypted HTTP/2, the use of `http2.createSecureServer()`\n// is necessary when communicating with browser clients.\nconst server = http2.createServer();\n\nserver.on('stream', (stream, headers) => {\n stream.respond({\n 'content-type': 'text/html; charset=utf-8',\n ':status': 200,\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(8000);\n
"
},
{
"textRaw": "`http2.createSecureServer(options[, onRequestHandler])`",
"type": "method",
"name": "createSecureServer",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": [
"v15.10.0",
"v14.16.0",
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"description": "Added `maxSettings` option with a default of 32."
},
{
"version": [
"v13.3.0",
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],
"pr-url": "https://github.com/nodejs/node/pull/30534",
"description": "Added `maxSessionRejectedStreams` option with a default of 100."
},
{
"version": [
"v13.3.0",
"v12.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/30534",
"description": "Added `maxSessionInvalidFrames` option with a default of 1000."
},
{
"version": "v13.0.0",
"pr-url": "https://github.com/nodejs/node/pull/29144",
"description": "The `PADDING_STRATEGY_CALLBACK` has been made equivalent to providing `PADDING_STRATEGY_ALIGNED` and `selectPadding` has been removed."
},
{
"version": "v10.12.0",
"pr-url": "https://github.com/nodejs/node/pull/22956",
"description": "Added the `origins` option to automatically send an `ORIGIN` frame on `Http2Session` startup."
},
{
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]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Http2SecureServer}",
"name": "return",
"type": "Http2SecureServer"
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`allowHTTP1` {boolean} Incoming client connections that do not support HTTP/2 will be downgraded to HTTP/1.x when set to `true`. See the [`'unknownProtocol'`][] event. See [ALPN negotiation][]. **Default:** `false`.",
"name": "allowHTTP1",
"type": "boolean",
"default": "`false`",
"desc": "Incoming client connections that do not support HTTP/2 will be downgraded to HTTP/1.x when set to `true`. See the [`'unknownProtocol'`][] event. See [ALPN negotiation][]."
},
{
"textRaw": "`maxDeflateDynamicTableSize` {number} Sets the maximum dynamic table size for deflating header fields. **Default:** `4Kib`.",
"name": "maxDeflateDynamicTableSize",
"type": "number",
"default": "`4Kib`",
"desc": "Sets the maximum dynamic table size for deflating header fields."
},
{
"textRaw": "`maxSettings` {number} Sets the maximum number of settings entries per `SETTINGS` frame. The minimum value allowed is `1`. **Default:** `32`.",
"name": "maxSettings",
"type": "number",
"default": "`32`",
"desc": "Sets the maximum number of settings entries per `SETTINGS` frame. The minimum value allowed is `1`."
},
{
"textRaw": "`maxSessionMemory`{number} Sets the maximum memory that the `Http2Session` is permitted to use. The value is expressed in terms of number of megabytes, e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. This is a credit based limit, existing `Http2Stream`s may cause this limit to be exceeded, but new `Http2Stream` instances will be rejected while this limit is exceeded. The current number of `Http2Stream` sessions, the current memory use of the header compression tables, current data queued to be sent, and unacknowledged `PING` and `SETTINGS` frames are all counted towards the current limit. **Default:** `10`.",
"name": "maxSessionMemory",
"type": "number",
"default": "`10`",
"desc": "Sets the maximum memory that the `Http2Session` is permitted to use. The value is expressed in terms of number of megabytes, e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. This is a credit based limit, existing `Http2Stream`s may cause this limit to be exceeded, but new `Http2Stream` instances will be rejected while this limit is exceeded. The current number of `Http2Stream` sessions, the current memory use of the header compression tables, current data queued to be sent, and unacknowledged `PING` and `SETTINGS` frames are all counted towards the current limit."
},
{
"textRaw": "`maxHeaderListPairs` {number} Sets the maximum number of header entries. This is similar to [`server.maxHeadersCount`][] or [`request.maxHeadersCount`][] in the `node:http` module. The minimum value is `4`. **Default:** `128`.",
"name": "maxHeaderListPairs",
"type": "number",
"default": "`128`",
"desc": "Sets the maximum number of header entries. This is similar to [`server.maxHeadersCount`][] or [`request.maxHeadersCount`][] in the `node:http` module. The minimum value is `4`."
},
{
"textRaw": "`maxOutstandingPings` {number} Sets the maximum number of outstanding, unacknowledged pings. **Default:** `10`.",
"name": "maxOutstandingPings",
"type": "number",
"default": "`10`",
"desc": "Sets the maximum number of outstanding, unacknowledged pings."
},
{
"textRaw": "`maxSendHeaderBlockLength` {number} Sets the maximum allowed size for a serialized, compressed block of headers. Attempts to send headers that exceed this limit will result in a `'frameError'` event being emitted and the stream being closed and destroyed.",
"name": "maxSendHeaderBlockLength",
"type": "number",
"desc": "Sets the maximum allowed size for a serialized, compressed block of headers. Attempts to send headers that exceed this limit will result in a `'frameError'` event being emitted and the stream being closed and destroyed."
},
{
"textRaw": "`paddingStrategy` {number} Strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames. **Default:** `http2.constants.PADDING_STRATEGY_NONE`. Value may be one of:",
"name": "paddingStrategy",
"type": "number",
"default": "`http2.constants.PADDING_STRATEGY_NONE`. Value may be one of:",
"desc": "Strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames.",
"options": [
{
"textRaw": "`http2.constants.PADDING_STRATEGY_NONE`: No padding is applied.",
"name": "http2.constants.PADDING_STRATEGY_NONE",
"desc": "No padding is applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_MAX`: The maximum amount of padding, determined by the internal implementation, is applied.",
"name": "http2.constants.PADDING_STRATEGY_MAX",
"desc": "The maximum amount of padding, determined by the internal implementation, is applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_ALIGNED`: Attempts to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, there is a maximum allowed number of padding bytes that is determined by current flow control state and settings. If this maximum is less than the calculated amount needed to ensure alignment, the maximum is used and the total frame length is not necessarily aligned at 8 bytes.",
"name": "http2.constants.PADDING_STRATEGY_ALIGNED",
"desc": "Attempts to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, there is a maximum allowed number of padding bytes that is determined by current flow control state and settings. If this maximum is less than the calculated amount needed to ensure alignment, the maximum is used and the total frame length is not necessarily aligned at 8 bytes."
}
]
},
{
"textRaw": "`peerMaxConcurrentStreams` {number} Sets the maximum number of concurrent streams for the remote peer as if a `SETTINGS` frame had been received. Will be overridden if the remote peer sets its own value for `maxConcurrentStreams`. **Default:** `100`.",
"name": "peerMaxConcurrentStreams",
"type": "number",
"default": "`100`",
"desc": "Sets the maximum number of concurrent streams for the remote peer as if a `SETTINGS` frame had been received. Will be overridden if the remote peer sets its own value for `maxConcurrentStreams`."
},
{
"textRaw": "`maxSessionInvalidFrames` {integer} Sets the maximum number of invalid frames that will be tolerated before the session is closed. **Default:** `1000`.",
"name": "maxSessionInvalidFrames",
"type": "integer",
"default": "`1000`",
"desc": "Sets the maximum number of invalid frames that will be tolerated before the session is closed."
},
{
"textRaw": "`maxSessionRejectedStreams` {integer} Sets the maximum number of rejected upon creation streams that will be tolerated before the session is closed. Each rejection is associated with an `NGHTTP2_ENHANCE_YOUR_CALM` error that should tell the peer to not open any more streams, continuing to open streams is therefore regarded as a sign of a misbehaving peer. **Default:** `100`.",
"name": "maxSessionRejectedStreams",
"type": "integer",
"default": "`100`",
"desc": "Sets the maximum number of rejected upon creation streams that will be tolerated before the session is closed. Each rejection is associated with an `NGHTTP2_ENHANCE_YOUR_CALM` error that should tell the peer to not open any more streams, continuing to open streams is therefore regarded as a sign of a misbehaving peer."
},
{
"textRaw": "`settings` {HTTP/2 Settings Object} The initial settings to send to the remote peer upon connection.",
"name": "settings",
"type": "HTTP/2 Settings Object",
"desc": "The initial settings to send to the remote peer upon connection."
},
{
"textRaw": "`remoteCustomSettings` {Array} The array of integer values determines the settings types, which are included in the `customSettings`-property of the received remoteSettings. Please see the `customSettings`-property of the `Http2Settings` object for more information, on the allowed setting types.",
"name": "remoteCustomSettings",
"type": "Array",
"desc": "The array of integer values determines the settings types, which are included in the `customSettings`-property of the received remoteSettings. Please see the `customSettings`-property of the `Http2Settings` object for more information, on the allowed setting types."
},
{
"textRaw": "...: Any [`tls.createServer()`][] options can be provided. For servers, the identity options (`pfx` or `key`/`cert`) are usually required.",
"name": "...",
"desc": "Any [`tls.createServer()`][] options can be provided. For servers, the identity options (`pfx` or `key`/`cert`) are usually required."
},
{
"textRaw": "`origins` {string\\[]} An array of origin strings to send within an `ORIGIN` frame immediately following creation of a new server `Http2Session`.",
"name": "origins",
"type": "string\\[]",
"desc": "An array of origin strings to send within an `ORIGIN` frame immediately following creation of a new server `Http2Session`."
},
{
"textRaw": "`unknownProtocolTimeout` {number} Specifies a timeout in milliseconds that a server should wait when an [`'unknownProtocol'`][] event is emitted. If the socket has not been destroyed by that time the server will destroy it. **Default:** `10000`.",
"name": "unknownProtocolTimeout",
"type": "number",
"default": "`10000`",
"desc": "Specifies a timeout in milliseconds that a server should wait when an [`'unknownProtocol'`][] event is emitted. If the socket has not been destroyed by that time the server will destroy it."
}
]
},
{
"textRaw": "`onRequestHandler` {Function} See [Compatibility API][]",
"name": "onRequestHandler",
"type": "Function",
"desc": "See [Compatibility API][]"
}
]
}
],
"desc": "Returns a tls.Server
instance that creates and manages Http2Session
\ninstances.
const http2 = require('node:http2');\nconst fs = require('node:fs');\n\nconst options = {\n key: fs.readFileSync('server-key.pem'),\n cert: fs.readFileSync('server-cert.pem'),\n};\n\n// Create a secure HTTP/2 server\nconst server = http2.createSecureServer(options);\n\nserver.on('stream', (stream, headers) => {\n stream.respond({\n 'content-type': 'text/html; charset=utf-8',\n ':status': 200,\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(8443);\n
"
},
{
"textRaw": "`http2.connect(authority[, options][, listener])`",
"type": "method",
"name": "connect",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": [
"v15.10.0",
"v14.16.0",
"v12.21.0",
"v10.24.0"
],
"pr-url": "https://github.com/nodejs-private/node-private/pull/246",
"description": "Added `unknownProtocolTimeout` option with a default of 10000."
},
{
"version": [
"v14.4.0",
"v12.18.0",
"v10.21.0"
],
"commit": "3948830ce6408be620b09a70bf66158623022af0",
"pr-url": "https://github.com/nodejs-private/node-private/pull/204",
"description": "Added `maxSettings` option with a default of 32."
},
{
"version": "v13.0.0",
"pr-url": "https://github.com/nodejs/node/pull/29144",
"description": "The `PADDING_STRATEGY_CALLBACK` has been made equivalent to providing `PADDING_STRATEGY_ALIGNED` and `selectPadding` has been removed."
},
{
"version": "v8.9.3",
"pr-url": "https://github.com/nodejs/node/pull/17105",
"description": "Added the `maxOutstandingPings` option with a default limit of 10."
},
{
"version": "v8.9.3",
"pr-url": "https://github.com/nodejs/node/pull/16676",
"description": "Added the `maxHeaderListPairs` option with a default limit of 128 header pairs."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {ClientHttp2Session}",
"name": "return",
"type": "ClientHttp2Session"
},
"params": [
{
"textRaw": "`authority` {string|URL} The remote HTTP/2 server to connect to. This must be in the form of a minimal, valid URL with the `http://` or `https://` prefix, host name, and IP port (if a non-default port is used). Userinfo (user ID and password), path, querystring, and fragment details in the URL will be ignored.",
"name": "authority",
"type": "string|URL",
"desc": "The remote HTTP/2 server to connect to. This must be in the form of a minimal, valid URL with the `http://` or `https://` prefix, host name, and IP port (if a non-default port is used). Userinfo (user ID and password), path, querystring, and fragment details in the URL will be ignored."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`maxDeflateDynamicTableSize` {number} Sets the maximum dynamic table size for deflating header fields. **Default:** `4Kib`.",
"name": "maxDeflateDynamicTableSize",
"type": "number",
"default": "`4Kib`",
"desc": "Sets the maximum dynamic table size for deflating header fields."
},
{
"textRaw": "`maxSettings` {number} Sets the maximum number of settings entries per `SETTINGS` frame. The minimum value allowed is `1`. **Default:** `32`.",
"name": "maxSettings",
"type": "number",
"default": "`32`",
"desc": "Sets the maximum number of settings entries per `SETTINGS` frame. The minimum value allowed is `1`."
},
{
"textRaw": "`maxSessionMemory`{number} Sets the maximum memory that the `Http2Session` is permitted to use. The value is expressed in terms of number of megabytes, e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. This is a credit based limit, existing `Http2Stream`s may cause this limit to be exceeded, but new `Http2Stream` instances will be rejected while this limit is exceeded. The current number of `Http2Stream` sessions, the current memory use of the header compression tables, current data queued to be sent, and unacknowledged `PING` and `SETTINGS` frames are all counted towards the current limit. **Default:** `10`.",
"name": "maxSessionMemory",
"type": "number",
"default": "`10`",
"desc": "Sets the maximum memory that the `Http2Session` is permitted to use. The value is expressed in terms of number of megabytes, e.g. `1` equal 1 megabyte. The minimum value allowed is `1`. This is a credit based limit, existing `Http2Stream`s may cause this limit to be exceeded, but new `Http2Stream` instances will be rejected while this limit is exceeded. The current number of `Http2Stream` sessions, the current memory use of the header compression tables, current data queued to be sent, and unacknowledged `PING` and `SETTINGS` frames are all counted towards the current limit."
},
{
"textRaw": "`maxHeaderListPairs` {number} Sets the maximum number of header entries. This is similar to [`server.maxHeadersCount`][] or [`request.maxHeadersCount`][] in the `node:http` module. The minimum value is `1`. **Default:** `128`.",
"name": "maxHeaderListPairs",
"type": "number",
"default": "`128`",
"desc": "Sets the maximum number of header entries. This is similar to [`server.maxHeadersCount`][] or [`request.maxHeadersCount`][] in the `node:http` module. The minimum value is `1`."
},
{
"textRaw": "`maxOutstandingPings` {number} Sets the maximum number of outstanding, unacknowledged pings. **Default:** `10`.",
"name": "maxOutstandingPings",
"type": "number",
"default": "`10`",
"desc": "Sets the maximum number of outstanding, unacknowledged pings."
},
{
"textRaw": "`maxReservedRemoteStreams` {number} Sets the maximum number of reserved push streams the client will accept at any given time. Once the current number of currently reserved push streams exceeds reaches this limit, new push streams sent by the server will be automatically rejected. The minimum allowed value is 0. The maximum allowed value is 232-1. A negative value sets this option to the maximum allowed value. **Default:** `200`.",
"name": "maxReservedRemoteStreams",
"type": "number",
"default": "`200`",
"desc": "Sets the maximum number of reserved push streams the client will accept at any given time. Once the current number of currently reserved push streams exceeds reaches this limit, new push streams sent by the server will be automatically rejected. The minimum allowed value is 0. The maximum allowed value is 232-1. A negative value sets this option to the maximum allowed value."
},
{
"textRaw": "`maxSendHeaderBlockLength` {number} Sets the maximum allowed size for a serialized, compressed block of headers. Attempts to send headers that exceed this limit will result in a `'frameError'` event being emitted and the stream being closed and destroyed.",
"name": "maxSendHeaderBlockLength",
"type": "number",
"desc": "Sets the maximum allowed size for a serialized, compressed block of headers. Attempts to send headers that exceed this limit will result in a `'frameError'` event being emitted and the stream being closed and destroyed."
},
{
"textRaw": "`paddingStrategy` {number} Strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames. **Default:** `http2.constants.PADDING_STRATEGY_NONE`. Value may be one of:",
"name": "paddingStrategy",
"type": "number",
"default": "`http2.constants.PADDING_STRATEGY_NONE`. Value may be one of:",
"desc": "Strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames.",
"options": [
{
"textRaw": "`http2.constants.PADDING_STRATEGY_NONE`: No padding is applied.",
"name": "http2.constants.PADDING_STRATEGY_NONE",
"desc": "No padding is applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_MAX`: The maximum amount of padding, determined by the internal implementation, is applied.",
"name": "http2.constants.PADDING_STRATEGY_MAX",
"desc": "The maximum amount of padding, determined by the internal implementation, is applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_ALIGNED`: Attempts to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, there is a maximum allowed number of padding bytes that is determined by current flow control state and settings. If this maximum is less than the calculated amount needed to ensure alignment, the maximum is used and the total frame length is not necessarily aligned at 8 bytes.",
"name": "http2.constants.PADDING_STRATEGY_ALIGNED",
"desc": "Attempts to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, there is a maximum allowed number of padding bytes that is determined by current flow control state and settings. If this maximum is less than the calculated amount needed to ensure alignment, the maximum is used and the total frame length is not necessarily aligned at 8 bytes."
}
]
},
{
"textRaw": "`peerMaxConcurrentStreams` {number} Sets the maximum number of concurrent streams for the remote peer as if a `SETTINGS` frame had been received. Will be overridden if the remote peer sets its own value for `maxConcurrentStreams`. **Default:** `100`.",
"name": "peerMaxConcurrentStreams",
"type": "number",
"default": "`100`",
"desc": "Sets the maximum number of concurrent streams for the remote peer as if a `SETTINGS` frame had been received. Will be overridden if the remote peer sets its own value for `maxConcurrentStreams`."
},
{
"textRaw": "`protocol` {string} The protocol to connect with, if not set in the `authority`. Value may be either `'http:'` or `'https:'`. **Default:** `'https:'`",
"name": "protocol",
"type": "string",
"default": "`'https:'`",
"desc": "The protocol to connect with, if not set in the `authority`. Value may be either `'http:'` or `'https:'`."
},
{
"textRaw": "`settings` {HTTP/2 Settings Object} The initial settings to send to the remote peer upon connection.",
"name": "settings",
"type": "HTTP/2 Settings Object",
"desc": "The initial settings to send to the remote peer upon connection."
},
{
"textRaw": "`remoteCustomSettings` {Array} The array of integer values determines the settings types, which are included in the `CustomSettings`-property of the received remoteSettings. Please see the `CustomSettings`-property of the `Http2Settings` object for more information, on the allowed setting types.",
"name": "remoteCustomSettings",
"type": "Array",
"desc": "The array of integer values determines the settings types, which are included in the `CustomSettings`-property of the received remoteSettings. Please see the `CustomSettings`-property of the `Http2Settings` object for more information, on the allowed setting types."
},
{
"textRaw": "`createConnection` {Function} An optional callback that receives the `URL` instance passed to `connect` and the `options` object, and returns any [`Duplex`][] stream that is to be used as the connection for this session.",
"name": "createConnection",
"type": "Function",
"desc": "An optional callback that receives the `URL` instance passed to `connect` and the `options` object, and returns any [`Duplex`][] stream that is to be used as the connection for this session."
},
{
"textRaw": "...: Any [`net.connect()`][] or [`tls.connect()`][] options can be provided.",
"name": "...",
"desc": "Any [`net.connect()`][] or [`tls.connect()`][] options can be provided."
},
{
"textRaw": "`unknownProtocolTimeout` {number} Specifies a timeout in milliseconds that a server should wait when an [`'unknownProtocol'`][] event is emitted. If the socket has not been destroyed by that time the server will destroy it. **Default:** `10000`.",
"name": "unknownProtocolTimeout",
"type": "number",
"default": "`10000`",
"desc": "Specifies a timeout in milliseconds that a server should wait when an [`'unknownProtocol'`][] event is emitted. If the socket has not been destroyed by that time the server will destroy it."
}
]
},
{
"textRaw": "`listener` {Function} Will be registered as a one-time listener of the [`'connect'`][] event.",
"name": "listener",
"type": "Function",
"desc": "Will be registered as a one-time listener of the [`'connect'`][] event."
}
]
}
],
"desc": "Returns a ClientHttp2Session
instance.
const http2 = require('node:http2');\nconst client = http2.connect('https://localhost:1234');\n\n/* Use the client */\n\nclient.close();\n
"
},
{
"textRaw": "`http2.getDefaultSettings()`",
"type": "method",
"name": "getDefaultSettings",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {HTTP/2 Settings Object}",
"name": "return",
"type": "HTTP/2 Settings Object"
},
"params": []
}
],
"desc": "Returns an object containing the default settings for an Http2Session
\ninstance. This method returns a new object instance every time it is called\nso instances returned may be safely modified for use.
Returns a Buffer
instance containing serialized representation of the given\nHTTP/2 settings as specified in the HTTP/2 specification. This is intended\nfor use with the HTTP2-Settings
header field.
const http2 = require('node:http2');\n\nconst packed = http2.getPackedSettings({ enablePush: false });\n\nconsole.log(packed.toString('base64'));\n// Prints: AAIAAAAA\n
"
},
{
"textRaw": "`http2.getUnpackedSettings(buf)`",
"type": "method",
"name": "getUnpackedSettings",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {HTTP/2 Settings Object}",
"name": "return",
"type": "HTTP/2 Settings Object"
},
"params": [
{
"textRaw": "`buf` {Buffer|TypedArray} The packed settings.",
"name": "buf",
"type": "Buffer|TypedArray",
"desc": "The packed settings."
}
]
}
],
"desc": "Returns a HTTP/2 Settings Object containing the deserialized settings from\nthe given Buffer
as generated by http2.getPackedSettings()
.
Create an HTTP/2 server session from an existing socket.
" } ], "properties": [ { "textRaw": "`http2.constants`", "name": "constants", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "modules": [ { "textRaw": "Error codes for `RST_STREAM` and `GOAWAY`", "name": "error_codes_for_`rst_stream`_and_`goaway`", "desc": "Value | \nName | \nConstant | \n
---|---|---|
0x00 | \nNo Error | \nhttp2.constants.NGHTTP2_NO_ERROR | \n
0x01 | \nProtocol Error | \nhttp2.constants.NGHTTP2_PROTOCOL_ERROR | \n
0x02 | \nInternal Error | \nhttp2.constants.NGHTTP2_INTERNAL_ERROR | \n
0x03 | \nFlow Control Error | \nhttp2.constants.NGHTTP2_FLOW_CONTROL_ERROR | \n
0x04 | \nSettings Timeout | \nhttp2.constants.NGHTTP2_SETTINGS_TIMEOUT | \n
0x05 | \nStream Closed | \nhttp2.constants.NGHTTP2_STREAM_CLOSED | \n
0x06 | \nFrame Size Error | \nhttp2.constants.NGHTTP2_FRAME_SIZE_ERROR | \n
0x07 | \nRefused Stream | \nhttp2.constants.NGHTTP2_REFUSED_STREAM | \n
0x08 | \nCancel | \nhttp2.constants.NGHTTP2_CANCEL | \n
0x09 | \nCompression Error | \nhttp2.constants.NGHTTP2_COMPRESSION_ERROR | \n
0x0a | \nConnect Error | \nhttp2.constants.NGHTTP2_CONNECT_ERROR | \n
0x0b | \nEnhance Your Calm | \nhttp2.constants.NGHTTP2_ENHANCE_YOUR_CALM | \n
0x0c | \nInadequate Security | \nhttp2.constants.NGHTTP2_INADEQUATE_SECURITY | \n
0x0d | \nHTTP/1.1 Required | \nhttp2.constants.NGHTTP2_HTTP_1_1_REQUIRED | \n
The 'timeout'
event is emitted when there is no activity on the Server for\na given number of milliseconds set using http2server.setTimeout()
.
This symbol can be set as a property on the HTTP/2 headers object with an array\nvalue in order to provide a list of headers considered sensitive.\nSee Sensitive headers for more details.
" } ], "type": "module", "displayName": "Core API" }, { "textRaw": "Compatibility API", "name": "compatibility_api", "desc": "The Compatibility API has the goal of providing a similar developer experience\nof HTTP/1 when using HTTP/2, making it possible to develop applications\nthat support both HTTP/1 and HTTP/2. This API targets only the\npublic API of the HTTP/1. However many modules use internal\nmethods or state, and those are not supported as it is a completely\ndifferent implementation.
\nThe following example creates an HTTP/2 server using the compatibility\nAPI:
\nconst http2 = require('node:http2');\nconst server = http2.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });\n res.end('ok');\n});\n
\nIn order to create a mixed HTTPS and HTTP/2 server, refer to the\nALPN negotiation section.\nUpgrading from non-tls HTTP/1 servers is not supported.
\nThe HTTP/2 compatibility API is composed of Http2ServerRequest
and\nHttp2ServerResponse
. They aim at API compatibility with HTTP/1, but\nthey do not hide the differences between the protocols. As an example,\nthe status message for HTTP codes is ignored.
ALPN negotiation allows supporting both HTTPS and HTTP/2 over\nthe same socket. The req
and res
objects can be either HTTP/1 or\nHTTP/2, and an application must restrict itself to the public API of\nHTTP/1, and detect if it is possible to use the more advanced\nfeatures of HTTP/2.
The following example creates a server that supports both protocols:
\nconst { createSecureServer } = require('node:http2');\nconst { readFileSync } = require('node:fs');\n\nconst cert = readFileSync('./cert.pem');\nconst key = readFileSync('./key.pem');\n\nconst server = createSecureServer(\n { cert, key, allowHTTP1: true },\n onRequest,\n).listen(4443);\n\nfunction onRequest(req, res) {\n // Detects if it is a HTTPS request or HTTP/2\n const { socket: { alpnProtocol } } = req.httpVersion === '2.0' ?\n req.stream.session : req;\n res.writeHead(200, { 'content-type': 'application/json' });\n res.end(JSON.stringify({\n alpnProtocol,\n httpVersion: req.httpVersion,\n }));\n}\n
\nThe 'request'
event works identically on both HTTPS and\nHTTP/2.
A Http2ServerRequest
object is created by http2.Server
or\nhttp2.SecureServer
and passed as the first argument to the\n'request'
event. It may be used to access a request status, headers, and\ndata.
The 'aborted'
event is emitted whenever a Http2ServerRequest
instance is\nabnormally aborted in mid-communication.
The 'aborted'
event will only be emitted if the Http2ServerRequest
writable\nside has not been ended.
Indicates that the underlying Http2Stream
was closed.\nJust like 'end'
, this event occurs only once per response.
The request.aborted
property will be true
if the request has\nbeen aborted.
The request authority pseudo header field. Because HTTP/2 allows requests\nto set either :authority
or host
, this value is derived from\nreq.headers[':authority']
if present. Otherwise, it is derived from\nreq.headers['host']
.
The request.complete
property will be true
if the request has\nbeen completed, aborted, or destroyed.
See request.socket
.
The request/response headers object.
\nKey-value pairs of header names and values. Header names are lower-cased.
\n// Prints something like:\n//\n// { 'user-agent': 'curl/7.22.0',\n// host: '127.0.0.1:8000',\n// accept: '*/*' }\nconsole.log(request.headers);\n
\n\nIn HTTP/2, the request path, host name, protocol, and method are represented as\nspecial headers prefixed with the :
character (e.g. ':path'
). These special\nheaders will be included in the request.headers
object. Care must be taken not\nto inadvertently modify these special headers or errors may occur. For instance,\nremoving all headers from the request will cause errors to occur:
removeAllHeaders(request.headers);\nassert(request.url); // Fails because the :path header has been removed\n
"
},
{
"textRaw": "`httpVersion` {string}",
"type": "string",
"name": "httpVersion",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"desc": "In case of server request, the HTTP version sent by the client. In the case of\nclient response, the HTTP version of the connected-to server. Returns\n'2.0'
.
Also message.httpVersionMajor
is the first integer and\nmessage.httpVersionMinor
is the second.
The request method as a string. Read-only. Examples: 'GET'
, 'DELETE'
.
The raw request/response headers list exactly as they were received.
\nThe keys and values are in the same list. It is not a\nlist of tuples. So, the even-numbered offsets are key values, and the\nodd-numbered offsets are the associated values.
\nHeader names are not lowercased, and duplicates are not merged.
\n// Prints something like:\n//\n// [ 'user-agent',\n// 'this is invalid because there can be only one',\n// 'User-Agent',\n// 'curl/7.22.0',\n// 'Host',\n// '127.0.0.1:8000',\n// 'ACCEPT',\n// '*/*' ]\nconsole.log(request.rawHeaders);\n
"
},
{
"textRaw": "`rawTrailers` {string\\[]}",
"type": "string\\[]",
"name": "rawTrailers",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"desc": "The raw request/response trailer keys and values exactly as they were\nreceived. Only populated at the 'end'
event.
The request scheme pseudo header field indicating the scheme\nportion of the target URL.
" }, { "textRaw": "`socket` {net.Socket|tls.TLSSocket}", "type": "net.Socket|tls.TLSSocket", "name": "socket", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Returns a Proxy
object that acts as a net.Socket
(or tls.TLSSocket
) but\napplies getters, setters, and methods based on HTTP/2 logic.
destroyed
, readable
, and writable
properties will be retrieved from and\nset on request.stream
.
destroy
, emit
, end
, on
and once
methods will be called on\nrequest.stream
.
setTimeout
method will be called on request.stream.session
.
pause
, read
, resume
, and write
will throw an error with code\nERR_HTTP2_NO_SOCKET_MANIPULATION
. See Http2Session
and Sockets for\nmore information.
All other interactions will be routed directly to the socket. With TLS support,\nuse request.socket.getPeerCertificate()
to obtain the client's\nauthentication details.
The Http2Stream
object backing the request.
The request/response trailers object. Only populated at the 'end'
event.
Request URL string. This contains only the URL that is present in the actual\nHTTP request. If the request is:
\nGET /status?name=ryan HTTP/1.1\nAccept: text/plain\n
\nThen request.url
will be:
'/status?name=ryan'\n
\nTo parse the url into its parts, new URL()
can be used:
$ node\n> new URL('/status?name=ryan', 'http://example.com')\nURL {\n href: 'http://example.com/status?name=ryan',\n origin: 'http://example.com',\n protocol: 'http:',\n username: '',\n password: '',\n host: 'example.com',\n hostname: 'example.com',\n port: '',\n pathname: '/status',\n search: '?name=ryan',\n searchParams: URLSearchParams { 'name' => 'ryan' },\n hash: ''\n}\n
"
}
],
"methods": [
{
"textRaw": "`request.destroy([error])`",
"type": "method",
"name": "destroy",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`error` {Error}",
"name": "error",
"type": "Error"
}
]
}
],
"desc": "Calls destroy()
on the Http2Stream
that received\nthe Http2ServerRequest
. If error
is provided, an 'error'
event\nis emitted and error
is passed as an argument to any listeners on the event.
It does nothing if the stream was already destroyed.
" }, { "textRaw": "`request.setTimeout(msecs, callback)`", "type": "method", "name": "setTimeout", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {http2.Http2ServerRequest}", "name": "return", "type": "http2.Http2ServerRequest" }, "params": [ { "textRaw": "`msecs` {number}", "name": "msecs", "type": "number" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function" } ] } ], "desc": "Sets the Http2Stream
's timeout value to msecs
. If a callback is\nprovided, then it is added as a listener on the 'timeout'
event on\nthe response object.
If no 'timeout'
listener is added to the request, the response, or\nthe server, then Http2Stream
s are destroyed when they time out. If a\nhandler is assigned to the request, the response, or the server's 'timeout'
\nevents, timed out sockets must be handled explicitly.
This object is created internally by an HTTP server, not by the user. It is\npassed as the second parameter to the 'request'
event.
Indicates that the underlying Http2Stream
was terminated before\nresponse.end()
was called or able to flush.
Emitted when the response has been sent. More specifically, this event is\nemitted when the last segment of the response headers and body have been\nhanded off to the HTTP/2 multiplexing for transmission over the network. It\ndoes not imply that the client has received anything yet.
\nAfter this event, no more events will be emitted on the response object.
" } ], "methods": [ { "textRaw": "`response.addTrailers(headers)`", "type": "method", "name": "addTrailers", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`headers` {Object}", "name": "headers", "type": "Object" } ] } ], "desc": "This method adds HTTP trailing headers (a header but at the end of the\nmessage) to the response.
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
Append a single header value to the header object.
\nIf the value is an array, this is equivalent to calling this method multiple\ntimes.
\nIf there were no previous values for the header, this is equivalent to calling\nresponse.setHeader()
.
Attempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
// Returns headers including \"set-cookie: a\" and \"set-cookie: b\"\nconst server = http2.createServer((req, res) => {\n res.setHeader('set-cookie', 'a');\n res.appendHeader('set-cookie', 'b');\n res.writeHead(200);\n res.end('ok');\n});\n
"
},
{
"textRaw": "`response.createPushResponse(headers, callback)`",
"type": "method",
"name": "createPushResponse",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`headers` {HTTP/2 Headers Object} An object describing the headers",
"name": "headers",
"type": "HTTP/2 Headers Object",
"desc": "An object describing the headers"
},
{
"textRaw": "`callback` {Function} Called once `http2stream.pushStream()` is finished, or either when the attempt to create the pushed `Http2Stream` has failed or has been rejected, or the state of `Http2ServerRequest` is closed prior to calling the `http2stream.pushStream()` method",
"name": "callback",
"type": "Function",
"desc": "Called once `http2stream.pushStream()` is finished, or either when the attempt to create the pushed `Http2Stream` has failed or has been rejected, or the state of `Http2ServerRequest` is closed prior to calling the `http2stream.pushStream()` method",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`res` {http2.Http2ServerResponse} The newly-created `Http2ServerResponse` object",
"name": "res",
"type": "http2.Http2ServerResponse",
"desc": "The newly-created `Http2ServerResponse` object"
}
]
}
]
}
],
"desc": "Call http2stream.pushStream()
with the given headers, and wrap the\ngiven Http2Stream
on a newly created Http2ServerResponse
as the callback\nparameter if successful. When Http2ServerRequest
is closed, the callback is\ncalled with an error ERR_HTTP2_INVALID_STREAM
.
This method signals to the server that all of the response headers and body\nhave been sent; that server should consider this message complete.\nThe method, response.end()
, MUST be called on each response.
If data
is specified, it is equivalent to calling\nresponse.write(data, encoding)
followed by response.end(callback)
.
If callback
is specified, it will be called when the response stream\nis finished.
Reads out a header that has already been queued but not sent to the client.\nThe name is case-insensitive.
\nconst contentType = response.getHeader('content-type');\n
"
},
{
"textRaw": "`response.getHeaderNames()`",
"type": "method",
"name": "getHeaderNames",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string\\[]}",
"name": "return",
"type": "string\\[]"
},
"params": []
}
],
"desc": "Returns an array containing the unique names of the current outgoing headers.\nAll header names are lowercase.
\nresponse.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headerNames = response.getHeaderNames();\n// headerNames === ['foo', 'set-cookie']\n
"
},
{
"textRaw": "`response.getHeaders()`",
"type": "method",
"name": "getHeaders",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Returns a shallow copy of the current outgoing headers. Since a shallow copy\nis used, array values may be mutated without additional calls to various\nheader-related http module methods. The keys of the returned object are the\nheader names and the values are the respective header values. All header names\nare lowercase.
\nThe object returned by the response.getHeaders()
method does not\nprototypically inherit from the JavaScript Object
. This means that typical\nObject
methods such as obj.toString()
, obj.hasOwnProperty()
, and others\nare not defined and will not work.
response.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headers = response.getHeaders();\n// headers === { foo: 'bar', 'set-cookie': ['foo=bar', 'bar=baz'] }\n
"
},
{
"textRaw": "`response.hasHeader(name)`",
"type": "method",
"name": "hasHeader",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Returns true
if the header identified by name
is currently set in the\noutgoing headers. The header name matching is case-insensitive.
const hasContentType = response.hasHeader('content-type');\n
"
},
{
"textRaw": "`response.removeHeader(name)`",
"type": "method",
"name": "removeHeader",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Removes a header that has been queued for implicit sending.
\nresponse.removeHeader('Content-Encoding');\n
"
},
{
"textRaw": "`response.setHeader(name, value)`",
"type": "method",
"name": "setHeader",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {string|string\\[]}",
"name": "value",
"type": "string|string\\[]"
}
]
}
],
"desc": "Sets a single header value for implicit headers. If this header already exists\nin the to-be-sent headers, its value will be replaced. Use an array of strings\nhere to send multiple headers with the same name.
\nresponse.setHeader('Content-Type', 'text/html; charset=utf-8');\n
\nor
\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);\n
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
When headers have been set with response.setHeader()
, they will be merged\nwith any headers passed to response.writeHead()
, with the headers passed\nto response.writeHead()
given precedence.
// Returns content-type = text/plain\nconst server = http2.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html; charset=utf-8');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });\n res.end('ok');\n});\n
"
},
{
"textRaw": "`response.setTimeout(msecs[, callback])`",
"type": "method",
"name": "setTimeout",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http2.Http2ServerResponse}",
"name": "return",
"type": "http2.Http2ServerResponse"
},
"params": [
{
"textRaw": "`msecs` {number}",
"name": "msecs",
"type": "number"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Sets the Http2Stream
's timeout value to msecs
. If a callback is\nprovided, then it is added as a listener on the 'timeout'
event on\nthe response object.
If no 'timeout'
listener is added to the request, the response, or\nthe server, then Http2Stream
s are destroyed when they time out. If a\nhandler is assigned to the request, the response, or the server's 'timeout'
\nevents, timed out sockets must be handled explicitly.
If this method is called and response.writeHead()
has not been called,\nit will switch to implicit header mode and flush the implicit headers.
This sends a chunk of the response body. This method may\nbe called multiple times to provide successive parts of the body.
\nIn the node:http
module, the response body is omitted when the\nrequest is a HEAD request. Similarly, the 204
and 304
responses\nmust not include a message body.
chunk
can be a string or a buffer. If chunk
is a string,\nthe second parameter specifies how to encode it into a byte stream.\nBy default the encoding
is 'utf8'
. callback
will be called when this chunk\nof data is flushed.
This is the raw HTTP body and has nothing to do with higher-level multi-part\nbody encodings that may be used.
\nThe first time response.write()
is called, it will send the buffered\nheader information and the first chunk of the body to the client. The second\ntime response.write()
is called, Node.js assumes data will be streamed,\nand sends the new data separately. That is, the response is buffered up to the\nfirst chunk of the body.
Returns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in user memory.\n'drain'
will be emitted when the buffer is free again.
Sends a status 100 Continue
to the client, indicating that the request body\nshould be sent. See the 'checkContinue'
event on Http2Server
and\nHttp2SecureServer
.
Sends a status 103 Early Hints
to the client with a Link header,\nindicating that the user agent can preload/preconnect the linked resources.\nThe hints
is an object containing the values of headers to be sent with\nearly hints message.
Example
\nconst earlyHintsLink = '</styles.css>; rel=preload; as=style';\nresponse.writeEarlyHints({\n 'link': earlyHintsLink,\n});\n\nconst earlyHintsLinks = [\n '</styles.css>; rel=preload; as=style',\n '</scripts.js>; rel=preload; as=script',\n];\nresponse.writeEarlyHints({\n 'link': earlyHintsLinks,\n});\n
"
},
{
"textRaw": "`response.writeHead(statusCode[, statusMessage][, headers])`",
"type": "method",
"name": "writeHead",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"version": [
"v11.10.0",
"v10.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/25974",
"description": "Return `this` from `writeHead()` to allow chaining with `end()`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http2.Http2ServerResponse}",
"name": "return",
"type": "http2.Http2ServerResponse"
},
"params": [
{
"textRaw": "`statusCode` {number}",
"name": "statusCode",
"type": "number"
},
{
"textRaw": "`statusMessage` {string}",
"name": "statusMessage",
"type": "string"
},
{
"textRaw": "`headers` {Object|Array}",
"name": "headers",
"type": "Object|Array"
}
]
}
],
"desc": "Sends a response header to the request. The status code is a 3-digit HTTP\nstatus code, like 404
. The last argument, headers
, are the response headers.
Returns a reference to the Http2ServerResponse
, so that calls can be chained.
For compatibility with HTTP/1, a human-readable statusMessage
may be\npassed as the second argument. However, because the statusMessage
has no\nmeaning within HTTP/2, the argument will have no effect and a process warning\nwill be emitted.
const body = 'hello world';\nresponse.writeHead(200, {\n 'Content-Length': Buffer.byteLength(body),\n 'Content-Type': 'text/plain; charset=utf-8',\n});\n
\nContent-Length
is given in bytes not characters. The\nBuffer.byteLength()
API may be used to determine the number of bytes in a\ngiven encoding. On outbound messages, Node.js does not check if Content-Length\nand the length of the body being transmitted are equal or not. However, when\nreceiving messages, Node.js will automatically reject messages when the\nContent-Length
does not match the actual payload size.
This method may be called at most one time on a message before\nresponse.end()
is called.
If response.write()
or response.end()
are called before calling\nthis, the implicit/mutable headers will be calculated and call this function.
When headers have been set with response.setHeader()
, they will be merged\nwith any headers passed to response.writeHead()
, with the headers passed\nto response.writeHead()
given precedence.
// Returns content-type = text/plain\nconst server = http2.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html; charset=utf-8');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });\n res.end('ok');\n});\n
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
See response.socket
.
Boolean value that indicates whether the response has completed. Starts\nas false
. After response.end()
executes, the value will be true
.
True if headers were sent, false otherwise (read-only).
" }, { "textRaw": "`req` {http2.Http2ServerRequest}", "type": "http2.Http2ServerRequest", "name": "req", "meta": { "added": [ "v15.7.0" ], "changes": [] }, "desc": "A reference to the original HTTP2 request
object.
When true, the Date header will be automatically generated and sent in\nthe response if it is not already present in the headers. Defaults to true.
\nThis should only be disabled for testing; HTTP requires the Date header\nin responses.
" }, { "textRaw": "`socket` {net.Socket|tls.TLSSocket}", "type": "net.Socket|tls.TLSSocket", "name": "socket", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Returns a Proxy
object that acts as a net.Socket
(or tls.TLSSocket
) but\napplies getters, setters, and methods based on HTTP/2 logic.
destroyed
, readable
, and writable
properties will be retrieved from and\nset on response.stream
.
destroy
, emit
, end
, on
and once
methods will be called on\nresponse.stream
.
setTimeout
method will be called on response.stream.session
.
pause
, read
, resume
, and write
will throw an error with code\nERR_HTTP2_NO_SOCKET_MANIPULATION
. See Http2Session
and Sockets for\nmore information.
All other interactions will be routed directly to the socket.
\nconst http2 = require('node:http2');\nconst server = http2.createServer((req, res) => {\n const ip = req.socket.remoteAddress;\n const port = req.socket.remotePort;\n res.end(`Your IP address is ${ip} and your source port is ${port}.`);\n}).listen(3000);\n
"
},
{
"textRaw": "`statusCode` {number}",
"type": "number",
"name": "statusCode",
"meta": {
"added": [
"v8.4.0"
],
"changes": []
},
"desc": "When using implicit headers (not calling response.writeHead()
explicitly),\nthis property controls the status code that will be sent to the client when\nthe headers get flushed.
response.statusCode = 404;\n
\nAfter response header was sent to the client, this property indicates the\nstatus code which was sent out.
" }, { "textRaw": "`statusMessage` {string}", "type": "string", "name": "statusMessage", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Status message is not supported by HTTP/2 (RFC 7540 8.1.2.4). It returns\nan empty string.
" }, { "textRaw": "`stream` {Http2Stream}", "type": "Http2Stream", "name": "stream", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "The Http2Stream
object backing the response.
Is true
after response.end()
has been called. This property\ndoes not indicate whether the data has been flushed, for this use\nwritable.writableFinished
instead.
The Performance Observer API can be used to collect basic performance\nmetrics for each Http2Session
and Http2Stream
instance.
const { PerformanceObserver } = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((items) => {\n const entry = items.getEntries()[0];\n console.log(entry.entryType); // prints 'http2'\n if (entry.name === 'Http2Session') {\n // Entry contains statistics about the Http2Session\n } else if (entry.name === 'Http2Stream') {\n // Entry contains statistics about the Http2Stream\n }\n});\nobs.observe({ entryTypes: ['http2'] });\n
\nThe entryType
property of the PerformanceEntry
will be equal to 'http2'
.
The name
property of the PerformanceEntry
will be equal to either\n'Http2Stream'
or 'Http2Session'
.
If name
is equal to Http2Stream
, the PerformanceEntry
will contain the\nfollowing additional properties:
bytesRead
<number> The number of DATA
frame bytes received for this\nHttp2Stream
.bytesWritten
<number> The number of DATA
frame bytes sent for this\nHttp2Stream
.id
<number> The identifier of the associated Http2Stream
timeToFirstByte
<number> The number of milliseconds elapsed between the\nPerformanceEntry
startTime
and the reception of the first DATA
frame.timeToFirstByteSent
<number> The number of milliseconds elapsed between\nthe PerformanceEntry
startTime
and sending of the first DATA
frame.timeToFirstHeader
<number> The number of milliseconds elapsed between the\nPerformanceEntry
startTime
and the reception of the first header.If name
is equal to Http2Session
, the PerformanceEntry
will contain the\nfollowing additional properties:
bytesRead
<number> The number of bytes received for this Http2Session
.bytesWritten
<number> The number of bytes sent for this Http2Session
.framesReceived
<number> The number of HTTP/2 frames received by the\nHttp2Session
.framesSent
<number> The number of HTTP/2 frames sent by the Http2Session
.maxConcurrentStreams
<number> The maximum number of streams concurrently\nopen during the lifetime of the Http2Session
.pingRTT
<number> The number of milliseconds elapsed since the transmission\nof a PING
frame and the reception of its acknowledgment. Only present if\na PING
frame has been sent on the Http2Session
.streamAverageDuration
<number> The average duration (in milliseconds) for\nall Http2Stream
instances.streamCount
<number> The number of Http2Stream
instances processed by\nthe Http2Session
.type
<string> Either 'server'
or 'client'
to identify the type of\nHttp2Session
.HTTP/2 requires requests to have either the :authority
pseudo-header\nor the host
header. Prefer :authority
when constructing an HTTP/2\nrequest directly, and host
when converting from HTTP/1 (in proxies,\nfor instance).
The compatibility API falls back to host
if :authority
is not\npresent. See request.authority
for more information. However,\nif you don't use the compatibility API (or use req.headers
directly),\nyou need to implement any fall-back behavior yourself.
Source Code: lib/https.js
\nHTTPS is the HTTP protocol over TLS/SSL. In Node.js this is implemented as a\nseparate module.
", "modules": [ { "textRaw": "Determining if crypto support is unavailable", "name": "determining_if_crypto_support_is_unavailable", "desc": "It is possible for Node.js to be built without including support for the\nnode:crypto
module. In such cases, attempting to import
from https
or\ncalling require('node:https')
will result in an error being thrown.
When using CommonJS, the error thrown can be caught using try/catch:
\nlet https;\ntry {\n https = require('node:https');\n} catch (err) {\n console.error('https support is disabled!');\n}\n
\nWhen using the lexical ESM import
keyword, the error can only be\ncaught if a handler for process.on('uncaughtException')
is registered\nbefore any attempt to load the module is made (using, for instance,\na preload module).
When using ESM, if there is a chance that the code may be run on a build\nof Node.js where crypto support is not enabled, consider using the\nimport()
function instead of the lexical import
keyword:
let https;\ntry {\n https = await import('node:https');\n} catch (err) {\n console.error('https support is disabled!');\n}\n
",
"type": "module",
"displayName": "Determining if crypto support is unavailable"
}
],
"classes": [
{
"textRaw": "Class: `https.Agent`",
"type": "class",
"name": "https.Agent",
"meta": {
"added": [
"v0.4.5"
],
"changes": [
{
"version": "v5.3.0",
"pr-url": "https://github.com/nodejs/node/pull/4252",
"description": "support `0` `maxCachedSessions` to disable TLS session caching."
},
{
"version": "v2.5.0",
"pr-url": "https://github.com/nodejs/node/pull/2228",
"description": "parameter `maxCachedSessions` added to `options` for TLS sessions reuse."
}
]
},
"desc": "An Agent
object for HTTPS similar to http.Agent
. See\nhttps.request()
for more information.
See http.Server
for more information.
See server.close()
in the node:http
module.
Calls server.close()
and returns a promise that\nfulfills when the server has closed.
See server.closeAllConnections()
in the node:http
module.
See server.closeIdleConnections()
in the node:http
module.
Starts the HTTPS server listening for encrypted connections.\nThis method is identical to server.listen()
from net.Server
.
See server.setTimeout()
in the node:http
module.
See server.headersTimeout
in the node:http
module.
See server.maxHeadersCount
in the node:http
module.
See server.requestTimeout
in the node:http
module.
See server.timeout
in the node:http
module.
See server.keepAliveTimeout
in the node:http
module.
// curl -k https://localhost:8000/\nconst https = require('node:https');\nconst fs = require('node:fs');\n\nconst options = {\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n};\n\nhttps.createServer(options, (req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n}).listen(8000);\n
\nOr
\nconst https = require('node:https');\nconst fs = require('node:fs');\n\nconst options = {\n pfx: fs.readFileSync('test/fixtures/test_cert.pfx'),\n passphrase: 'sample',\n};\n\nhttps.createServer(options, (req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n}).listen(8000);\n
"
},
{
"textRaw": "`https.get(options[, callback])`",
"type": "method",
"name": "get",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object | string | URL} Accepts the same `options` as [`https.request()`][], with the method set to GET by default.",
"name": "options",
"type": "Object | string | URL",
"desc": "Accepts the same `options` as [`https.request()`][], with the method set to GET by default."
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Like http.get()
but for HTTPS.
options
can be an object, a string, or a URL
object. If options
is a\nstring, it is automatically parsed with new URL()
. If it is a URL
\nobject, it will be automatically converted to an ordinary options
object.
const https = require('node:https');\n\nhttps.get('https://encrypted.google.com/', (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n\n}).on('error', (e) => {\n console.error(e);\n});\n
"
},
{
"textRaw": "`https.get(url[, options][, callback])`",
"type": "method",
"name": "get",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object | string | URL} Accepts the same `options` as [`https.request()`][], with the method set to GET by default.",
"name": "options",
"type": "Object | string | URL",
"desc": "Accepts the same `options` as [`https.request()`][], with the method set to GET by default."
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Like http.get()
but for HTTPS.
options
can be an object, a string, or a URL
object. If options
is a\nstring, it is automatically parsed with new URL()
. If it is a URL
\nobject, it will be automatically converted to an ordinary options
object.
const https = require('node:https');\n\nhttps.get('https://encrypted.google.com/', (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n\n}).on('error', (e) => {\n console.error(e);\n});\n
"
},
{
"textRaw": "`https.request(options[, callback])`",
"type": "method",
"name": "request",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": [
"v16.7.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/39310",
"description": "When using a `URL` object parsed username and password will now be properly URI decoded."
},
{
"version": [
"v14.1.0",
"v13.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32786",
"description": "The `highWaterMark` option is accepted now."
},
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v9.3.0",
"pr-url": "https://github.com/nodejs/node/pull/14903",
"description": "The `options` parameter can now include `clientCertEngine`."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ClientRequest}",
"name": "return",
"type": "http.ClientRequest"
},
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object | string | URL} Accepts all `options` from [`http.request()`][], with some differences in default values:",
"name": "options",
"type": "Object | string | URL",
"desc": "Accepts all `options` from [`http.request()`][], with some differences in default values:",
"options": [
{
"textRaw": "`protocol` **Default:** `'https:'`",
"name": "protocol",
"default": "`'https:'`"
},
{
"textRaw": "`port` **Default:** `443`",
"name": "port",
"default": "`443`"
},
{
"textRaw": "`agent` **Default:** `https.globalAgent`",
"name": "agent",
"default": "`https.globalAgent`"
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Makes a request to a secure web server.
\nThe following additional options
from tls.connect()
are also accepted:\nca
, cert
, ciphers
, clientCertEngine
, crl
, dhparam
, ecdhCurve
,\nhonorCipherOrder
, key
, passphrase
, pfx
, rejectUnauthorized
,\nsecureOptions
, secureProtocol
, servername
, sessionIdContext
,\nhighWaterMark
.
options
can be an object, a string, or a URL
object. If options
is a\nstring, it is automatically parsed with new URL()
. If it is a URL
\nobject, it will be automatically converted to an ordinary options
object.
https.request()
returns an instance of the http.ClientRequest
\nclass. The ClientRequest
instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest
object.
const https = require('node:https');\n\nconst options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n};\n\nconst req = https.request(options, (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n});\n\nreq.on('error', (e) => {\n console.error(e);\n});\nreq.end();\n
\nExample using options from tls.connect()
:
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n};\noptions.agent = new https.Agent(options);\n\nconst req = https.request(options, (res) => {\n // ...\n});\n
\nAlternatively, opt out of connection pooling by not using an Agent
.
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n agent: false,\n};\n\nconst req = https.request(options, (res) => {\n // ...\n});\n
\nExample using a URL
as options
:
const options = new URL('https://abc:xyz@example.com');\n\nconst req = https.request(options, (res) => {\n // ...\n});\n
\nExample pinning on certificate fingerprint, or the public key (similar to\npin-sha256
):
const tls = require('node:tls');\nconst https = require('node:https');\nconst crypto = require('node:crypto');\n\nfunction sha256(s) {\n return crypto.createHash('sha256').update(s).digest('base64');\n}\nconst options = {\n hostname: 'github.com',\n port: 443,\n path: '/',\n method: 'GET',\n checkServerIdentity: function(host, cert) {\n // Make sure the certificate is issued to the host we are connected to\n const err = tls.checkServerIdentity(host, cert);\n if (err) {\n return err;\n }\n\n // Pin the public key, similar to HPKP pin-sha256 pinning\n const pubkey256 = 'pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=';\n if (sha256(cert.pubkey) !== pubkey256) {\n const msg = 'Certificate verification error: ' +\n `The public key of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // Pin the exact certificate, rather than the pub key\n const cert256 = '25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:' +\n 'D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16';\n if (cert.fingerprint256 !== cert256) {\n const msg = 'Certificate verification error: ' +\n `The certificate of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // This loop is informational only.\n // Print the certificate and public key fingerprints of all certs in the\n // chain. Its common to pin the public key of the issuer on the public\n // internet, while pinning the public key of the service in sensitive\n // environments.\n do {\n console.log('Subject Common Name:', cert.subject.CN);\n console.log(' Certificate SHA256 fingerprint:', cert.fingerprint256);\n\n hash = crypto.createHash('sha256');\n console.log(' Public key ping-sha256:', sha256(cert.pubkey));\n\n lastprint256 = cert.fingerprint256;\n cert = cert.issuerCertificate;\n } while (cert.fingerprint256 !== lastprint256);\n\n },\n};\n\noptions.agent = new https.Agent(options);\nconst req = https.request(options, (res) => {\n console.log('All OK. Server matched our pinned cert or public key');\n console.log('statusCode:', res.statusCode);\n // Print the HPKP values\n console.log('headers:', res.headers['public-key-pins']);\n\n res.on('data', (d) => {});\n});\n\nreq.on('error', (e) => {\n console.error(e.message);\n});\nreq.end();\n
\nOutputs for example:
\nSubject Common Name: github.com\n Certificate SHA256 fingerprint: 25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16\n Public key ping-sha256: pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=\nSubject Common Name: DigiCert SHA2 Extended Validation Server CA\n Certificate SHA256 fingerprint: 40:3E:06:2A:26:53:05:91:13:28:5B:AF:80:A0:D4:AE:42:2C:84:8C:9F:78:FA:D0:1F:C9:4B:C5:B8:7F:EF:1A\n Public key ping-sha256: RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\nSubject Common Name: DigiCert High Assurance EV Root CA\n Certificate SHA256 fingerprint: 74:31:E5:F4:C3:C1:CE:46:90:77:4F:0B:61:E0:54:40:88:3B:A9:A0:1E:D0:0B:A6:AB:D7:80:6E:D3:B1:18:CF\n Public key ping-sha256: WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\nAll OK. Server matched our pinned cert or public key\nstatusCode: 200\nheaders: max-age=0; pin-sha256=\"WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\"; pin-sha256=\"RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\"; pin-sha256=\"k2v657xBsOVe1PQRwOsHsw3bsGT2VzIqz5K+59sNQws=\"; pin-sha256=\"K87oWBWM9UZfyddvDfoxL+8lpNyoUB2ptGtn0fv6G2Q=\"; pin-sha256=\"IQBnNBEiFuhj+8x6X8XLgh01V9Ic5/V3IRQLNFFc7v4=\"; pin-sha256=\"iie1VXtL7HzAMF+/PVPR9xzT80kQxdZeJ+zduCB3uj0=\"; pin-sha256=\"LvRiGEjRqfzurezaWuj8Wie2gyHMrW5Q06LspMnox7A=\"; includeSubDomains\n
"
},
{
"textRaw": "`https.request(url[, options][, callback])`",
"type": "method",
"name": "request",
"meta": {
"added": [
"v0.3.6"
],
"changes": [
{
"version": [
"v16.7.0",
"v14.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/39310",
"description": "When using a `URL` object parsed username and password will now be properly URI decoded."
},
{
"version": [
"v14.1.0",
"v13.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32786",
"description": "The `highWaterMark` option is accepted now."
},
{
"version": "v10.9.0",
"pr-url": "https://github.com/nodejs/node/pull/21616",
"description": "The `url` parameter can now be passed along with a separate `options` object."
},
{
"version": "v9.3.0",
"pr-url": "https://github.com/nodejs/node/pull/14903",
"description": "The `options` parameter can now include `clientCertEngine`."
},
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10638",
"description": "The `options` parameter can be a WHATWG `URL` object."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {http.ClientRequest}",
"name": "return",
"type": "http.ClientRequest"
},
"params": [
{
"textRaw": "`url` {string | URL}",
"name": "url",
"type": "string | URL"
},
{
"textRaw": "`options` {Object | string | URL} Accepts all `options` from [`http.request()`][], with some differences in default values:",
"name": "options",
"type": "Object | string | URL",
"desc": "Accepts all `options` from [`http.request()`][], with some differences in default values:",
"options": [
{
"textRaw": "`protocol` **Default:** `'https:'`",
"name": "protocol",
"default": "`'https:'`"
},
{
"textRaw": "`port` **Default:** `443`",
"name": "port",
"default": "`443`"
},
{
"textRaw": "`agent` **Default:** `https.globalAgent`",
"name": "agent",
"default": "`https.globalAgent`"
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Makes a request to a secure web server.
\nThe following additional options
from tls.connect()
are also accepted:\nca
, cert
, ciphers
, clientCertEngine
, crl
, dhparam
, ecdhCurve
,\nhonorCipherOrder
, key
, passphrase
, pfx
, rejectUnauthorized
,\nsecureOptions
, secureProtocol
, servername
, sessionIdContext
,\nhighWaterMark
.
options
can be an object, a string, or a URL
object. If options
is a\nstring, it is automatically parsed with new URL()
. If it is a URL
\nobject, it will be automatically converted to an ordinary options
object.
https.request()
returns an instance of the http.ClientRequest
\nclass. The ClientRequest
instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest
object.
const https = require('node:https');\n\nconst options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n};\n\nconst req = https.request(options, (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n});\n\nreq.on('error', (e) => {\n console.error(e);\n});\nreq.end();\n
\nExample using options from tls.connect()
:
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n};\noptions.agent = new https.Agent(options);\n\nconst req = https.request(options, (res) => {\n // ...\n});\n
\nAlternatively, opt out of connection pooling by not using an Agent
.
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n agent: false,\n};\n\nconst req = https.request(options, (res) => {\n // ...\n});\n
\nExample using a URL
as options
:
const options = new URL('https://abc:xyz@example.com');\n\nconst req = https.request(options, (res) => {\n // ...\n});\n
\nExample pinning on certificate fingerprint, or the public key (similar to\npin-sha256
):
const tls = require('node:tls');\nconst https = require('node:https');\nconst crypto = require('node:crypto');\n\nfunction sha256(s) {\n return crypto.createHash('sha256').update(s).digest('base64');\n}\nconst options = {\n hostname: 'github.com',\n port: 443,\n path: '/',\n method: 'GET',\n checkServerIdentity: function(host, cert) {\n // Make sure the certificate is issued to the host we are connected to\n const err = tls.checkServerIdentity(host, cert);\n if (err) {\n return err;\n }\n\n // Pin the public key, similar to HPKP pin-sha256 pinning\n const pubkey256 = 'pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=';\n if (sha256(cert.pubkey) !== pubkey256) {\n const msg = 'Certificate verification error: ' +\n `The public key of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // Pin the exact certificate, rather than the pub key\n const cert256 = '25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:' +\n 'D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16';\n if (cert.fingerprint256 !== cert256) {\n const msg = 'Certificate verification error: ' +\n `The certificate of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // This loop is informational only.\n // Print the certificate and public key fingerprints of all certs in the\n // chain. Its common to pin the public key of the issuer on the public\n // internet, while pinning the public key of the service in sensitive\n // environments.\n do {\n console.log('Subject Common Name:', cert.subject.CN);\n console.log(' Certificate SHA256 fingerprint:', cert.fingerprint256);\n\n hash = crypto.createHash('sha256');\n console.log(' Public key ping-sha256:', sha256(cert.pubkey));\n\n lastprint256 = cert.fingerprint256;\n cert = cert.issuerCertificate;\n } while (cert.fingerprint256 !== lastprint256);\n\n },\n};\n\noptions.agent = new https.Agent(options);\nconst req = https.request(options, (res) => {\n console.log('All OK. Server matched our pinned cert or public key');\n console.log('statusCode:', res.statusCode);\n // Print the HPKP values\n console.log('headers:', res.headers['public-key-pins']);\n\n res.on('data', (d) => {});\n});\n\nreq.on('error', (e) => {\n console.error(e.message);\n});\nreq.end();\n
\nOutputs for example:
\nSubject Common Name: github.com\n Certificate SHA256 fingerprint: 25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16\n Public key ping-sha256: pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=\nSubject Common Name: DigiCert SHA2 Extended Validation Server CA\n Certificate SHA256 fingerprint: 40:3E:06:2A:26:53:05:91:13:28:5B:AF:80:A0:D4:AE:42:2C:84:8C:9F:78:FA:D0:1F:C9:4B:C5:B8:7F:EF:1A\n Public key ping-sha256: RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\nSubject Common Name: DigiCert High Assurance EV Root CA\n Certificate SHA256 fingerprint: 74:31:E5:F4:C3:C1:CE:46:90:77:4F:0B:61:E0:54:40:88:3B:A9:A0:1E:D0:0B:A6:AB:D7:80:6E:D3:B1:18:CF\n Public key ping-sha256: WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\nAll OK. Server matched our pinned cert or public key\nstatusCode: 200\nheaders: max-age=0; pin-sha256=\"WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\"; pin-sha256=\"RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\"; pin-sha256=\"k2v657xBsOVe1PQRwOsHsw3bsGT2VzIqz5K+59sNQws=\"; pin-sha256=\"K87oWBWM9UZfyddvDfoxL+8lpNyoUB2ptGtn0fv6G2Q=\"; pin-sha256=\"IQBnNBEiFuhj+8x6X8XLgh01V9Ic5/V3IRQLNFFc7v4=\"; pin-sha256=\"iie1VXtL7HzAMF+/PVPR9xzT80kQxdZeJ+zduCB3uj0=\"; pin-sha256=\"LvRiGEjRqfzurezaWuj8Wie2gyHMrW5Q06LspMnox7A=\"; includeSubDomains\n
"
}
],
"properties": [
{
"textRaw": "`https.globalAgent`",
"name": "globalAgent",
"meta": {
"added": [
"v0.5.9"
],
"changes": [
{
"version": [
"v19.0.0"
],
"pr-url": "https://github.com/nodejs/node/pull/43522",
"description": "The agent now uses HTTP Keep-Alive by default."
}
]
},
"desc": "Global instance of https.Agent
for all HTTPS client requests.
Source Code: lib/inspector.js
\nThe node:inspector
module provides an API for interacting with the V8\ninspector.
It can be accessed using:
\nimport * as inspector from 'node:inspector/promises';\n
\nconst inspector = require('node:inspector/promises');\n
\nor
\nimport * as inspector from 'node:inspector';\n
\nconst inspector = require('node:inspector');\n
",
"modules": [
{
"textRaw": "Promises API",
"name": "promises_api",
"stability": 1,
"stabilityText": "Experimental",
"meta": {
"added": [
"v19.0.0"
],
"changes": []
},
"classes": [
{
"textRaw": "Class: `inspector.Session`",
"type": "class",
"name": "inspector.Session",
"desc": "The inspector.Session
is used for dispatching messages to the V8 inspector\nback-end and receiving message responses and notifications.
Emitted when any notification from the V8 Inspector is received.
\nsession.on('inspectorNotification', (message) => console.log(message.method));\n// Debugger.paused\n// Debugger.resumed\n
\n\n\nCaveat Breakpoints with same-thread session is not recommended, see\nsupport of breakpoints.
\n
It is also possible to subscribe only to notifications with specific method:
" }, { "textRaw": "Event: `Emitted when an inspector notification is received that has its method field set\nto the <inspector-protocol-method>
value.
The following snippet installs a listener on the 'Debugger.paused'
\nevent, and prints the reason for program suspension whenever program\nexecution is suspended (through breakpoints, for example):
session.on('Debugger.paused', ({ params }) => {\n console.log(params.hitBreakpoints);\n});\n// [ '/the/file/that/has/the/breakpoint.js:11:0' ]\n
\n\n" } ], "methods": [ { "textRaw": "`session.connect()`", "type": "method", "name": "connect", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Caveat Breakpoints with same-thread session is not recommended, see\nsupport of breakpoints.
\n
Connects a session to the inspector back-end.
" }, { "textRaw": "`session.connectToMainThread()`", "type": "method", "name": "connectToMainThread", "meta": { "added": [ "v12.11.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Connects a session to the main thread inspector back-end. An exception will\nbe thrown if this API was not called on a Worker thread.
" }, { "textRaw": "`session.disconnect()`", "type": "method", "name": "disconnect", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Immediately close the session. All pending message callbacks will be called\nwith an error. session.connect()
will need to be called to be able to send\nmessages again. Reconnected session will lose all inspector state, such as\nenabled agents or configured breakpoints.
Posts a message to the inspector back-end.
\nimport { Session } from 'node:inspector/promises';\ntry {\n const session = new Session();\n session.connect();\n const result = await session.post('Runtime.evaluate', { expression: '2 + 2' });\n console.log(result);\n} catch (error) {\n console.error(error);\n}\n// Output: { result: { type: 'number', value: 4, description: '4' } }\n
\nThe latest version of the V8 inspector protocol is published on the\nChrome DevTools Protocol Viewer.
\nNode.js inspector supports all the Chrome DevTools Protocol domains declared\nby V8. Chrome DevTools Protocol domain provides an interface for interacting\nwith one of the runtime agents used to inspect the application state and listen\nto the run-time events.
\nApart from the debugger, various V8 Profilers are available through the DevTools\nprotocol.
", "modules": [ { "textRaw": "CPU profiler", "name": "cpu_profiler", "desc": "Here's an example showing how to use the CPU Profiler:
\nimport { Session } from 'node:inspector/promises';\nimport fs from 'node:fs';\nconst session = new Session();\nsession.connect();\n\nawait session.post('Profiler.enable');\nawait session.post('Profiler.start');\n// Invoke business logic under measurement here...\n\n// some time later...\nconst { profile } = await session.post('Profiler.stop');\n\n// Write profile to disk, upload, etc.\nfs.writeFileSync('./profile.cpuprofile', JSON.stringify(profile));\n
",
"type": "module",
"displayName": "CPU profiler"
},
{
"textRaw": "Heap profiler",
"name": "heap_profiler",
"desc": "Here's an example showing how to use the Heap Profiler:
\nimport { Session } from 'node:inspector/promises';\nimport fs from 'node:fs';\nconst session = new Session();\n\nconst fd = fs.openSync('profile.heapsnapshot', 'w');\n\nsession.connect();\n\nsession.on('HeapProfiler.addHeapSnapshotChunk', (m) => {\n fs.writeSync(fd, m.params.chunk);\n});\n\nconst result = await session.post('HeapProfiler.takeHeapSnapshot', null);\nconsole.log('HeapProfiler.takeHeapSnapshot done:', result);\nsession.disconnect();\nfs.closeSync(fd);\n
",
"type": "module",
"displayName": "Heap profiler"
}
]
}
],
"signatures": [
{
"params": [],
"desc": "Create a new instance of the inspector.Session
class. The inspector session\nneeds to be connected through session.connect()
before the messages\ncan be dispatched to the inspector backend.
When using Session
, the object outputted by the console API will not be\nreleased, unless we performed manually Runtime.DiscardConsoleEntries
\ncommand.
The inspector.Session
is used for dispatching messages to the V8 inspector\nback-end and receiving message responses and notifications.
Emitted when any notification from the V8 Inspector is received.
\nsession.on('inspectorNotification', (message) => console.log(message.method));\n// Debugger.paused\n// Debugger.resumed\n
\n\n\nCaveat Breakpoints with same-thread session is not recommended, see\nsupport of breakpoints.
\n
It is also possible to subscribe only to notifications with specific method:
" }, { "textRaw": "Event: `Emitted when an inspector notification is received that has its method field set\nto the <inspector-protocol-method>
value.
The following snippet installs a listener on the 'Debugger.paused'
\nevent, and prints the reason for program suspension whenever program\nexecution is suspended (through breakpoints, for example):
session.on('Debugger.paused', ({ params }) => {\n console.log(params.hitBreakpoints);\n});\n// [ '/the/file/that/has/the/breakpoint.js:11:0' ]\n
\n\n" } ], "methods": [ { "textRaw": "`session.connect()`", "type": "method", "name": "connect", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Caveat Breakpoints with same-thread session is not recommended, see\nsupport of breakpoints.
\n
Connects a session to the inspector back-end.
" }, { "textRaw": "`session.connectToMainThread()`", "type": "method", "name": "connectToMainThread", "meta": { "added": [ "v12.11.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Connects a session to the main thread inspector back-end. An exception will\nbe thrown if this API was not called on a Worker thread.
" }, { "textRaw": "`session.disconnect()`", "type": "method", "name": "disconnect", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Immediately close the session. All pending message callbacks will be called\nwith an error. session.connect()
will need to be called to be able to send\nmessages again. Reconnected session will lose all inspector state, such as\nenabled agents or configured breakpoints.
Posts a message to the inspector back-end. callback
will be notified when\na response is received. callback
is a function that accepts two optional\narguments: error and message-specific result.
session.post('Runtime.evaluate', { expression: '2 + 2' },\n (error, { result }) => console.log(result));\n// Output: { type: 'number', value: 4, description: '4' }\n
\nThe latest version of the V8 inspector protocol is published on the\nChrome DevTools Protocol Viewer.
\nNode.js inspector supports all the Chrome DevTools Protocol domains declared\nby V8. Chrome DevTools Protocol domain provides an interface for interacting\nwith one of the runtime agents used to inspect the application state and listen\nto the run-time events.
\nYou can not set reportProgress
to true
when sending a\nHeapProfiler.takeHeapSnapshot
or HeapProfiler.stopTrackingHeapObjects
\ncommand to V8.
Apart from the debugger, various V8 Profilers are available through the DevTools\nprotocol.
", "modules": [ { "textRaw": "CPU profiler", "name": "cpu_profiler", "desc": "Here's an example showing how to use the CPU Profiler:
\nconst inspector = require('node:inspector');\nconst fs = require('node:fs');\nconst session = new inspector.Session();\nsession.connect();\n\nsession.post('Profiler.enable', () => {\n session.post('Profiler.start', () => {\n // Invoke business logic under measurement here...\n\n // some time later...\n session.post('Profiler.stop', (err, { profile }) => {\n // Write profile to disk, upload, etc.\n if (!err) {\n fs.writeFileSync('./profile.cpuprofile', JSON.stringify(profile));\n }\n });\n });\n});\n
",
"type": "module",
"displayName": "CPU profiler"
},
{
"textRaw": "Heap profiler",
"name": "heap_profiler",
"desc": "Here's an example showing how to use the Heap Profiler:
\nconst inspector = require('node:inspector');\nconst fs = require('node:fs');\nconst session = new inspector.Session();\n\nconst fd = fs.openSync('profile.heapsnapshot', 'w');\n\nsession.connect();\n\nsession.on('HeapProfiler.addHeapSnapshotChunk', (m) => {\n fs.writeSync(fd, m.params.chunk);\n});\n\nsession.post('HeapProfiler.takeHeapSnapshot', null, (err, r) => {\n console.log('HeapProfiler.takeHeapSnapshot done:', err, r);\n session.disconnect();\n fs.closeSync(fd);\n});\n
",
"type": "module",
"displayName": "Heap profiler"
}
]
}
],
"signatures": [
{
"params": [],
"desc": "Create a new instance of the inspector.Session
class. The inspector session\nneeds to be connected through session.connect()
before the messages\ncan be dispatched to the inspector backend.
When using Session
, the object outputted by the console API will not be\nreleased, unless we performed manually Runtime.DiscardConsoleEntries
\ncommand.
Attempts to close all remaining connections, blocking the event loop until all\nare closed. Once all connections are closed, deactivates the inspector.
" }, { "textRaw": "`inspector.open([port[, host[, wait]]])`", "type": "method", "name": "open", "meta": { "changes": [ { "version": "v20.6.0", "pr-url": "https://github.com/nodejs/node/pull/48765", "description": "inspector.open() now returns a `Disposable` object." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Disposable} A Disposable that calls [`inspector.close()`][].", "name": "return", "type": "Disposable", "desc": "A Disposable that calls [`inspector.close()`][]." }, "params": [ { "textRaw": "`port` {number} Port to listen on for inspector connections. Optional. **Default:** what was specified on the CLI.", "name": "port", "type": "number", "default": "what was specified on the CLI", "desc": "Port to listen on for inspector connections. Optional." }, { "textRaw": "`host` {string} Host to listen on for inspector connections. Optional. **Default:** what was specified on the CLI.", "name": "host", "type": "string", "default": "what was specified on the CLI", "desc": "Host to listen on for inspector connections. Optional." }, { "textRaw": "`wait` {boolean} Block until a client has connected. Optional. **Default:** `false`.", "name": "wait", "type": "boolean", "default": "`false`", "desc": "Block until a client has connected. Optional." } ] } ], "desc": "Activate inspector on host and port. Equivalent to\nnode --inspect=[[host:]port]
, but can be done programmatically after node has\nstarted.
If wait is true
, will block until a client has connected to the inspect port\nand flow control has been passed to the debugger client.
See the security warning regarding the host
\nparameter usage.
Return the URL of the active inspector, or undefined
if there is none.
$ node --inspect -p 'inspector.url()'\nDebugger listening on ws://127.0.0.1:9229/166e272e-7a30-4d09-97ce-f1c012b43c34\nFor help, see: https://nodejs.org/en/docs/inspector\nws://127.0.0.1:9229/166e272e-7a30-4d09-97ce-f1c012b43c34\n\n$ node --inspect=localhost:3000 -p 'inspector.url()'\nDebugger listening on ws://localhost:3000/51cf8d0e-3c36-4c59-8efd-54519839e56a\nFor help, see: https://nodejs.org/en/docs/inspector\nws://localhost:3000/51cf8d0e-3c36-4c59-8efd-54519839e56a\n\n$ node -p 'inspector.url()'\nundefined\n
"
},
{
"textRaw": "`inspector.waitForDebugger()`",
"type": "method",
"name": "waitForDebugger",
"meta": {
"added": [
"v12.7.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Blocks until a client (existing or connected later) has sent\nRuntime.runIfWaitingForDebugger
command.
An exception will be thrown if there is no active inspector.
" } ], "properties": [ { "textRaw": "`console` {Object} An object to send messages to the remote inspector console.", "type": "Object", "name": "console", "desc": "require('node:inspector').console.log('a message');\n
\nThe inspector console does not have API parity with Node.js\nconsole.
", "shortDesc": "An object to send messages to the remote inspector console." } ], "type": "module", "displayName": "Common Objects" }, { "textRaw": "Support of breakpoints", "name": "support_of_breakpoints", "desc": "The Chrome DevTools Protocol Debugger
domain allows an\ninspector.Session
to attach to a program and set breakpoints to step through\nthe codes.
However, setting breakpoints with a same-thread inspector.Session
, which is\nconnected by session.connect()
, should be avoided as the program being\nattached and paused is exactly the debugger itself. Instead, try connect to the\nmain thread by session.connectToMainThread()
and set breakpoints in a\nworker thread, or connect with a Debugger program over WebSocket\nconnection.
CommonJS modules are the original way to package JavaScript code for Node.js.\nNode.js also supports the ECMAScript modules standard used by browsers\nand other JavaScript runtimes.
\nIn Node.js, each file is treated as a separate module. For\nexample, consider a file named foo.js
:
const circle = require('./circle.js');\nconsole.log(`The area of a circle of radius 4 is ${circle.area(4)}`);\n
\nOn the first line, foo.js
loads the module circle.js
that is in the same\ndirectory as foo.js
.
Here are the contents of circle.js
:
const { PI } = Math;\n\nexports.area = (r) => PI * r ** 2;\n\nexports.circumference = (r) => 2 * PI * r;\n
\nThe module circle.js
has exported the functions area()
and\ncircumference()
. Functions and objects are added to the root of a module\nby specifying additional properties on the special exports
object.
Variables local to the module will be private, because the module is wrapped\nin a function by Node.js (see module wrapper).\nIn this example, the variable PI
is private to circle.js
.
The module.exports
property can be assigned a new value (such as a function\nor object).
Below, bar.js
makes use of the square
module, which exports a Square class:
const Square = require('./square.js');\nconst mySquare = new Square(2);\nconsole.log(`The area of mySquare is ${mySquare.area()}`);\n
\nThe square
module is defined in square.js
:
// Assigning to exports will not modify module, must use module.exports\nmodule.exports = class Square {\n constructor(width) {\n this.width = width;\n }\n\n area() {\n return this.width ** 2;\n }\n};\n
\nThe CommonJS module system is implemented in the module
core module.
Node.js has two module systems: CommonJS modules and ECMAScript modules.
\nBy default, Node.js will treat the following as CommonJS modules:
\nFiles with a .cjs
extension;
Files with a .js
extension when the nearest parent package.json
file\ncontains a top-level field \"type\"
with a value of \"commonjs\"
.
Files with a .js
extension or without an extension, when the nearest parent\npackage.json
file doesn't contain a top-level field \"type\"
or there is\nno package.json
in any parent folder; unless the file contains syntax that\nerrors unless it is evaluated as an ES module. Package authors should include\nthe \"type\"
field, even in packages where all sources are CommonJS. Being\nexplicit about the type
of the package will make things easier for build\ntools and loaders to determine how the files in the package should be\ninterpreted.
Files with an extension that is not .mjs
, .cjs
, .json
, .node
, or .js
\n(when the nearest parent package.json
file contains a top-level field\n\"type\"
with a value of \"module\"
, those files will be recognized as\nCommonJS modules only if they are being included via require()
, not when\nused as the command-line entry point of the program).
See Determining module system for more details.
\nCalling require()
always use the CommonJS module loader. Calling import()
\nalways use the ECMAScript module loader.
When a file is run directly from Node.js, require.main
is set to its\nmodule
. That means that it is possible to determine whether a file has been\nrun directly by testing require.main === module
.
For a file foo.js
, this will be true
if run via node foo.js
, but\nfalse
if run by require('./foo')
.
When the entry point is not a CommonJS module, require.main
is undefined
,\nand the main module is out of reach.
The semantics of the Node.js require()
function were designed to be general\nenough to support reasonable directory structures. Package manager programs\nsuch as dpkg
, rpm
, and npm
will hopefully find it possible to build\nnative packages from Node.js modules without modification.
Below we give a suggested directory structure that could work:
\nLet's say that we wanted to have the folder at\n/usr/lib/node/<some-package>/<some-version>
hold the contents of a\nspecific version of a package.
Packages can depend on one another. In order to install package foo
, it\nmay be necessary to install a specific version of package bar
. The bar
\npackage may itself have dependencies, and in some cases, these may even collide\nor form cyclic dependencies.
Because Node.js looks up the realpath
of any modules it loads (that is, it\nresolves symlinks) and then looks for their dependencies in node_modules
folders,\nthis situation can be resolved with the following architecture:
/usr/lib/node/foo/1.2.3/
: Contents of the foo
package, version 1.2.3./usr/lib/node/bar/4.3.2/
: Contents of the bar
package that foo
depends\non./usr/lib/node/foo/1.2.3/node_modules/bar
: Symbolic link to\n/usr/lib/node/bar/4.3.2/
./usr/lib/node/bar/4.3.2/node_modules/*
: Symbolic links to the packages that\nbar
depends on.Thus, even if a cycle is encountered, or if there are dependency\nconflicts, every module will be able to get a version of its dependency\nthat it can use.
\nWhen the code in the foo
package does require('bar')
, it will get the\nversion that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar
.\nThen, when the code in the bar
package calls require('quux')
, it'll get\nthe version that is symlinked into\n/usr/lib/node/bar/4.3.2/node_modules/quux
.
Furthermore, to make the module lookup process even more optimal, rather\nthan putting packages directly in /usr/lib/node
, we could put them in\n/usr/lib/node_modules/<name>/<version>
. Then Node.js will not bother\nlooking for missing dependencies in /usr/node_modules
or /node_modules
.
In order to make modules available to the Node.js REPL, it might be useful to\nalso add the /usr/lib/node_modules
folder to the $NODE_PATH
environment\nvariable. Since the module lookups using node_modules
folders are all\nrelative, and based on the real path of the files making the calls to\nrequire()
, the packages themselves can be anywhere.
To get the exact filename that will be loaded when require()
is called, use\nthe require.resolve()
function.
Putting together all of the above, here is the high-level algorithm\nin pseudocode of what require()
does:
\nrequire(X) from module at path Y\n1. If X is a core module,\n a. return the core module\n b. STOP\n2. If X begins with '/'\n a. set Y to be the file system root\n3. If X begins with './' or '/' or '../'\n a. LOAD_AS_FILE(Y + X)\n b. LOAD_AS_DIRECTORY(Y + X)\n c. THROW \"not found\"\n4. If X begins with '#'\n a. LOAD_PACKAGE_IMPORTS(X, dirname(Y))\n5. LOAD_PACKAGE_SELF(X, dirname(Y))\n6. LOAD_NODE_MODULES(X, dirname(Y))\n7. THROW \"not found\"\n\nLOAD_AS_FILE(X)\n1. If X is a file, load X as its file extension format. STOP\n2. If X.js is a file, load X.js as JavaScript text. STOP\n3. If X.json is a file, parse X.json to a JavaScript Object. STOP\n4. If X.node is a file, load X.node as binary addon. STOP\n\nLOAD_INDEX(X)\n1. If X/index.js is a file, load X/index.js as JavaScript text. STOP\n2. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP\n3. If X/index.node is a file, load X/index.node as binary addon. STOP\n\nLOAD_AS_DIRECTORY(X)\n1. If X/package.json is a file,\n a. Parse X/package.json, and look for \"main\" field.\n b. If \"main\" is a falsy value, GOTO 2.\n c. let M = X + (json main field)\n d. LOAD_AS_FILE(M)\n e. LOAD_INDEX(M)\n f. LOAD_INDEX(X) DEPRECATED\n g. THROW \"not found\"\n2. LOAD_INDEX(X)\n\nLOAD_NODE_MODULES(X, START)\n1. let DIRS = NODE_MODULES_PATHS(START)\n2. for each DIR in DIRS:\n a. LOAD_PACKAGE_EXPORTS(X, DIR)\n b. LOAD_AS_FILE(DIR/X)\n c. LOAD_AS_DIRECTORY(DIR/X)\n\nNODE_MODULES_PATHS(START)\n1. let PARTS = path split(START)\n2. let I = count of PARTS - 1\n3. let DIRS = []\n4. while I >= 0,\n a. if PARTS[I] = \"node_modules\" CONTINUE\n b. DIR = path join(PARTS[0 .. I] + \"node_modules\")\n c. DIRS = DIR + DIRS\n d. let I = I - 1\n5. return DIRS + GLOBAL_FOLDERS\n\nLOAD_PACKAGE_IMPORTS(X, DIR)\n1. Find the closest package scope SCOPE to DIR.\n2. If no scope was found, return.\n3. If the SCOPE/package.json \"imports\" is null or undefined, return.\n4. let MATCH = PACKAGE_IMPORTS_RESOLVE(X, pathToFileURL(SCOPE),\n [\"node\", \"require\"]) defined in the ESM resolver.\n5. RESOLVE_ESM_MATCH(MATCH).\n\nLOAD_PACKAGE_EXPORTS(X, DIR)\n1. Try to interpret X as a combination of NAME and SUBPATH where the name\n may have a @scope/ prefix and the subpath begins with a slash (`/`).\n2. If X does not match this pattern or DIR/NAME/package.json is not a file,\n return.\n3. Parse DIR/NAME/package.json, and look for \"exports\" field.\n4. If \"exports\" is null or undefined, return.\n5. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(DIR/NAME), \".\" + SUBPATH,\n `package.json` \"exports\", [\"node\", \"require\"]) defined in the ESM resolver.\n6. RESOLVE_ESM_MATCH(MATCH)\n\nLOAD_PACKAGE_SELF(X, DIR)\n1. Find the closest package scope SCOPE to DIR.\n2. If no scope was found, return.\n3. If the SCOPE/package.json \"exports\" is null or undefined, return.\n4. If the SCOPE/package.json \"name\" is not the first segment of X, return.\n5. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(SCOPE),\n \".\" + X.slice(\"name\".length), `package.json` \"exports\", [\"node\", \"require\"])\n defined in the ESM resolver.\n6. RESOLVE_ESM_MATCH(MATCH)\n\nRESOLVE_ESM_MATCH(MATCH)\n1. let RESOLVED_PATH = fileURLToPath(MATCH)\n2. If the file at RESOLVED_PATH exists, load RESOLVED_PATH as its extension\n format. STOP\n3. THROW \"not found\"\n" }, { "textRaw": "Caching", "name": "Caching", "type": "misc", "desc": "
Modules are cached after the first time they are loaded. This means (among other\nthings) that every call to require('foo')
will get exactly the same object\nreturned, if it would resolve to the same file.
Provided require.cache
is not modified, multiple calls to require('foo')
\nwill not cause the module code to be executed multiple times. This is an\nimportant feature. With it, \"partially done\" objects can be returned, thus\nallowing transitive dependencies to be loaded even when they would cause cycles.
To have a module execute code multiple times, export a function, and call that\nfunction.
", "miscs": [ { "textRaw": "Module caching caveats", "name": "Module caching caveats", "type": "misc", "desc": "Modules are cached based on their resolved filename. Since modules may resolve\nto a different filename based on the location of the calling module (loading\nfrom node_modules
folders), it is not a guarantee that require('foo')
will\nalways return the exact same object, if it would resolve to different files.
Additionally, on case-insensitive file systems or operating systems, different\nresolved filenames can point to the same file, but the cache will still treat\nthem as different modules and will reload the file multiple times. For example,\nrequire('./foo')
and require('./FOO')
return two different objects,\nirrespective of whether or not ./foo
and ./FOO
are the same file.
Node.js has several modules compiled into the binary. These modules are\ndescribed in greater detail elsewhere in this documentation.
\nThe core modules are defined within the Node.js source and are located in the\nlib/
folder.
Core modules can be identified using the node:
prefix, in which case\nit bypasses the require
cache. For instance, require('node:http')
will\nalways return the built in HTTP module, even if there is require.cache
entry\nby that name.
Some core modules are always preferentially loaded if their identifier is\npassed to require()
. For instance, require('http')
will always\nreturn the built-in HTTP module, even if there is a file by that name. The list\nof core modules that can be loaded without using the node:
prefix is exposed\nas module.builtinModules
.
When there are circular require()
calls, a module might not have finished\nexecuting when it is returned.
Consider this situation:
\na.js
:
console.log('a starting');\nexports.done = false;\nconst b = require('./b.js');\nconsole.log('in a, b.done = %j', b.done);\nexports.done = true;\nconsole.log('a done');\n
\nb.js
:
console.log('b starting');\nexports.done = false;\nconst a = require('./a.js');\nconsole.log('in b, a.done = %j', a.done);\nexports.done = true;\nconsole.log('b done');\n
\nmain.js
:
console.log('main starting');\nconst a = require('./a.js');\nconst b = require('./b.js');\nconsole.log('in main, a.done = %j, b.done = %j', a.done, b.done);\n
\nWhen main.js
loads a.js
, then a.js
in turn loads b.js
. At that\npoint, b.js
tries to load a.js
. In order to prevent an infinite\nloop, an unfinished copy of the a.js
exports object is returned to the\nb.js
module. b.js
then finishes loading, and its exports
object is\nprovided to the a.js
module.
By the time main.js
has loaded both modules, they're both finished.\nThe output of this program would thus be:
$ node main.js\nmain starting\na starting\nb starting\nin b, a.done = false\nb done\nin a, b.done = true\na done\nin main, a.done = true, b.done = true\n
\nCareful planning is required to allow cyclic module dependencies to work\ncorrectly within an application.
" }, { "textRaw": "File modules", "name": "File modules", "type": "misc", "desc": "If the exact filename is not found, then Node.js will attempt to load the\nrequired filename with the added extensions: .js
, .json
, and finally\n.node
. When loading a file that has a different extension (e.g. .cjs
), its\nfull name must be passed to require()
, including its file extension (e.g.\nrequire('./file.cjs')
).
.json
files are parsed as JSON text files, .node
files are interpreted as\ncompiled addon modules loaded with process.dlopen()
. Files using any other\nextension (or no extension at all) are parsed as JavaScript text files. Refer to\nthe Determining module system section to understand what parse goal will be\nused.
A required module prefixed with '/'
is an absolute path to the file. For\nexample, require('/home/marco/foo.js')
will load the file at\n/home/marco/foo.js
.
A required module prefixed with './'
is relative to the file calling\nrequire()
. That is, circle.js
must be in the same directory as foo.js
for\nrequire('./circle')
to find it.
Without a leading '/'
, './'
, or '../'
to indicate a file, the module must\neither be a core module or is loaded from a node_modules
folder.
If the given path does not exist, require()
will throw a\nMODULE_NOT_FOUND
error.
There are three ways in which a folder may be passed to require()
as\nan argument.
The first is to create a package.json
file in the root of the folder,\nwhich specifies a main
module. An example package.json
file might\nlook like this:
{ \"name\" : \"some-library\",\n \"main\" : \"./lib/some-library.js\" }\n
\nIf this was in a folder at ./some-library
, then\nrequire('./some-library')
would attempt to load\n./some-library/lib/some-library.js
.
If there is no package.json
file present in the directory, or if the\n\"main\"
entry is missing or cannot be resolved, then Node.js\nwill attempt to load an index.js
or index.node
file out of that\ndirectory. For example, if there was no package.json
file in the previous\nexample, then require('./some-library')
would attempt to load:
./some-library/index.js
./some-library/index.node
If these attempts fail, then Node.js will report the entire module as missing\nwith the default error:
\nError: Cannot find module 'some-library'\n
\nIn all three above cases, an import('./some-library')
call would result in a\nERR_UNSUPPORTED_DIR_IMPORT
error. Using package subpath exports or\nsubpath imports can provide the same containment organization benefits as\nfolders as modules, and work for both require
and import
.
If the module identifier passed to require()
is not a\ncore module, and does not begin with '/'
, '../'
, or\n'./'
, then Node.js starts at the directory of the current module, and\nadds /node_modules
, and attempts to load the module from that location.\nNode.js will not append node_modules
to a path already ending in\nnode_modules
.
If it is not found there, then it moves to the parent directory, and so\non, until the root of the file system is reached.
\nFor example, if the file at '/home/ry/projects/foo.js'
called\nrequire('bar.js')
, then Node.js would look in the following locations, in\nthis order:
/home/ry/projects/node_modules/bar.js
/home/ry/node_modules/bar.js
/home/node_modules/bar.js
/node_modules/bar.js
This allows programs to localize their dependencies, so that they do not\nclash.
\nIt is possible to require specific files or sub modules distributed with a\nmodule by including a path suffix after the module name. For instance\nrequire('example-module/path/to/file')
would resolve path/to/file
\nrelative to where example-module
is located. The suffixed path follows the\nsame module resolution semantics.
If the NODE_PATH
environment variable is set to a colon-delimited list\nof absolute paths, then Node.js will search those paths for modules if they\nare not found elsewhere.
On Windows, NODE_PATH
is delimited by semicolons (;
) instead of colons.
NODE_PATH
was originally created to support loading modules from\nvarying paths before the current module resolution algorithm was defined.
NODE_PATH
is still supported, but is less necessary now that the Node.js\necosystem has settled on a convention for locating dependent modules.\nSometimes deployments that rely on NODE_PATH
show surprising behavior\nwhen people are unaware that NODE_PATH
must be set. Sometimes a\nmodule's dependencies change, causing a different version (or even a\ndifferent module) to be loaded as the NODE_PATH
is searched.
Additionally, Node.js will search in the following list of GLOBAL_FOLDERS:
\n$HOME/.node_modules
$HOME/.node_libraries
$PREFIX/lib/node
Where $HOME
is the user's home directory, and $PREFIX
is the Node.js\nconfigured node_prefix
.
These are mostly for historic reasons.
\nIt is strongly encouraged to place dependencies in the local node_modules
\nfolder. These will be loaded faster, and more reliably.
Before a module's code is executed, Node.js will wrap it with a function\nwrapper that looks like the following:
\n(function(exports, require, module, __filename, __dirname) {\n// Module code actually lives in here\n});\n
\nBy doing this, Node.js achieves a few things:
\nvar
, const
, or let
) scoped to\nthe module rather than the global object.module
and exports
objects that the implementor can use to export\nvalues from the module.__filename
and __dirname
, containing the\nmodule's absolute filename and directory path.Due to the synchronous nature of require()
, it is not possible to use it to\nload ECMAScript module files. Attempting to do so will throw a\nERR_REQUIRE_ESM
error. Use import()
instead.
The .mjs
extension is reserved for ECMAScript Modules which cannot be\nloaded via require()
. See Determining module system section for more info\nregarding which files are parsed as ECMAScript modules.
The directory name of the current module. This is the same as the\npath.dirname()
of the __filename
.
Example: running node example.js
from /Users/mjr
console.log(__dirname);\n// Prints: /Users/mjr\nconsole.log(path.dirname(__filename));\n// Prints: /Users/mjr\n
"
},
{
"textRaw": "`__filename`",
"name": "`__filename`",
"meta": {
"added": [
"v0.0.1"
],
"changes": []
},
"type": "var",
"desc": "The file name of the current module. This is the current module file's absolute\npath with symlinks resolved.
\nFor a main program this is not necessarily the same as the file name used in the\ncommand line.
\nSee __dirname
for the directory name of the current module.
Examples:
\nRunning node example.js
from /Users/mjr
console.log(__filename);\n// Prints: /Users/mjr/example.js\nconsole.log(__dirname);\n// Prints: /Users/mjr\n
\nGiven two modules: a
and b
, where b
is a dependency of\na
and there is a directory structure of:
/Users/mjr/app/a.js
/Users/mjr/app/node_modules/b/b.js
References to __filename
within b.js
will return\n/Users/mjr/app/node_modules/b/b.js
while references to __filename
within\na.js
will return /Users/mjr/app/a.js
.
A reference to the module.exports
that is shorter to type.\nSee the section about the exports shortcut for details on when to use\nexports
and when to use module.exports
.
A reference to the current module, see the section about the\nmodule
object. In particular, module.exports
is used for defining what\na module exports and makes available through require()
.
Used to import modules, JSON
, and local files. Modules can be imported\nfrom node_modules
. Local modules and JSON files can be imported using\na relative path (e.g. ./
, ./foo
, ./bar/baz
, ../foo
) that will be\nresolved against the directory named by __dirname
(if defined) or\nthe current working directory. The relative paths of POSIX style are resolved\nin an OS independent fashion, meaning that the examples above will work on\nWindows in the same way they would on Unix systems.
// Importing a local module with a path relative to the `__dirname` or current\n// working directory. (On Windows, this would resolve to .\\path\\myLocalModule.)\nconst myLocalModule = require('./path/myLocalModule');\n\n// Importing a JSON file:\nconst jsonData = require('./path/filename.json');\n\n// Importing a module from node_modules or Node.js built-in module:\nconst crypto = require('node:crypto');\n
",
"properties": [
{
"textRaw": "`cache` {Object}",
"type": "Object",
"name": "cache",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"desc": "Modules are cached in this object when they are required. By deleting a key\nvalue from this object, the next require
will reload the module.\nThis does not apply to native addons, for which reloading will result in an\nerror.
Adding or replacing entries is also possible. This cache is checked before\nbuilt-in modules and if a name matching a built-in module is added to the cache,\nonly node:
-prefixed require calls are going to receive the built-in module.\nUse with care!
const assert = require('node:assert');\nconst realFs = require('node:fs');\n\nconst fakeFs = {};\nrequire.cache.fs = { exports: fakeFs };\n\nassert.strictEqual(require('fs'), fakeFs);\nassert.strictEqual(require('node:fs'), realFs);\n
"
},
{
"textRaw": "`extensions` {Object}",
"type": "Object",
"name": "extensions",
"meta": {
"added": [
"v0.3.0"
],
"deprecated": [
"v0.10.6"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Instruct require
on how to handle certain file extensions.
Process files with the extension .sjs
as .js
:
require.extensions['.sjs'] = require.extensions['.js'];\n
\nDeprecated. In the past, this list has been used to load non-JavaScript\nmodules into Node.js by compiling them on-demand. However, in practice, there\nare much better ways to do this, such as loading modules via some other Node.js\nprogram, or compiling them to JavaScript ahead of time.
\nAvoid using require.extensions
. Use could cause subtle bugs and resolving the\nextensions gets slower with each registered extension.
The Module
object representing the entry script loaded when the Node.js\nprocess launched, or undefined
if the entry point of the program is not a\nCommonJS module.\nSee \"Accessing the main module\".
In entry.js
script:
console.log(require.main);\n
\nnode entry.js\n
\n\nModule {\n id: '.',\n path: '/absolute/path/to',\n exports: {},\n filename: '/absolute/path/to/entry.js',\n loaded: false,\n children: [],\n paths:\n [ '/absolute/path/to/node_modules',\n '/absolute/path/node_modules',\n '/absolute/node_modules',\n '/node_modules' ] }\n
"
}
],
"methods": [
{
"textRaw": "`require.resolve(request[, options])`",
"type": "method",
"name": "resolve",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"version": "v8.9.0",
"pr-url": "https://github.com/nodejs/node/pull/16397",
"description": "The `paths` option is now supported."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`request` {string} The module path to resolve.",
"name": "request",
"type": "string",
"desc": "The module path to resolve."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`paths` {string\\[]} Paths to resolve module location from. If present, these paths are used instead of the default resolution paths, with the exception of [GLOBAL\\_FOLDERS][GLOBAL_FOLDERS] like `$HOME/.node_modules`, which are always included. Each of these paths is used as a starting point for the module resolution algorithm, meaning that the `node_modules` hierarchy is checked from this location.",
"name": "paths",
"type": "string\\[]",
"desc": "Paths to resolve module location from. If present, these paths are used instead of the default resolution paths, with the exception of [GLOBAL\\_FOLDERS][GLOBAL_FOLDERS] like `$HOME/.node_modules`, which are always included. Each of these paths is used as a starting point for the module resolution algorithm, meaning that the `node_modules` hierarchy is checked from this location."
}
]
}
]
}
],
"desc": "Use the internal require()
machinery to look up the location of a module,\nbut rather than loading the module, just return the resolved filename.
If the module can not be found, a MODULE_NOT_FOUND
error is thrown.
Returns an array containing the paths searched during resolution of request
or\nnull
if the request
string references a core module, for example http
or\nfs
.
This section was moved to\nModules: module
core module.
This section was moved to\nModules: module
core module.
In each module, the module
free variable is a reference to the object\nrepresenting the current module. For convenience, module.exports
is\nalso accessible via the exports
module-global. module
is not actually\na global but rather local to each module.
The module objects required for the first time by this one.
" }, { "textRaw": "`exports` {Object}", "type": "Object", "name": "exports", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "The module.exports
object is created by the Module
system. Sometimes this is\nnot acceptable; many want their module to be an instance of some class. To do\nthis, assign the desired export object to module.exports
. Assigning\nthe desired object to exports
will simply rebind the local exports
variable,\nwhich is probably not what is desired.
For example, suppose we were making a module called a.js
:
const EventEmitter = require('node:events');\n\nmodule.exports = new EventEmitter();\n\n// Do some work, and after some time emit\n// the 'ready' event from the module itself.\nsetTimeout(() => {\n module.exports.emit('ready');\n}, 1000);\n
\nThen in another file we could do:
\nconst a = require('./a');\na.on('ready', () => {\n console.log('module \"a\" is ready');\n});\n
\nAssignment to module.exports
must be done immediately. It cannot be\ndone in any callbacks. This does not work:
x.js
:
setTimeout(() => {\n module.exports = { a: 'hello' };\n}, 0);\n
\ny.js
:
const x = require('./x');\nconsole.log(x.a);\n
",
"modules": [
{
"textRaw": "`exports` shortcut",
"name": "`exports`_shortcut",
"meta": {
"added": [
"v0.1.16"
],
"changes": []
},
"desc": "The exports
variable is available within a module's file-level scope, and is\nassigned the value of module.exports
before the module is evaluated.
It allows a shortcut, so that module.exports.f = ...
can be written more\nsuccinctly as exports.f = ...
. However, be aware that like any variable, if a\nnew value is assigned to exports
, it is no longer bound to module.exports
:
module.exports.hello = true; // Exported from require of module\nexports = { hello: false }; // Not exported, only available in the module\n
\nWhen the module.exports
property is being completely replaced by a new\nobject, it is common to also reassign exports
:
module.exports = exports = function Constructor() {\n // ... etc.\n};\n
\nTo illustrate the behavior, imagine this hypothetical implementation of\nrequire()
, which is quite similar to what is actually done by require()
:
function require(/* ... */) {\n const module = { exports: {} };\n ((module, exports) => {\n // Module code here. In this example, define a function.\n function someFunc() {}\n exports = someFunc;\n // At this point, exports is no longer a shortcut to module.exports, and\n // this module will still export an empty default object.\n module.exports = someFunc;\n // At this point, the module will now export someFunc, instead of the\n // default object.\n })(module, module.exports);\n return module.exports;\n}\n
",
"type": "module",
"displayName": "`exports` shortcut"
}
]
},
{
"textRaw": "`filename` {string}",
"type": "string",
"name": "filename",
"meta": {
"added": [
"v0.1.16"
],
"changes": []
},
"desc": "The fully resolved filename of the module.
" }, { "textRaw": "`id` {string}", "type": "string", "name": "id", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "The identifier for the module. Typically this is the fully resolved\nfilename.
" }, { "textRaw": "`isPreloading` Type: {boolean} `true` if the module is running during the Node.js preload phase.", "type": "boolean", "name": "Type", "meta": { "added": [ "v15.4.0", "v14.17.0" ], "changes": [] }, "desc": "`true` if the module is running during the Node.js preload phase." }, { "textRaw": "`loaded` {boolean}", "type": "boolean", "name": "loaded", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "Whether or not the module is done loading, or is in the process of\nloading.
" }, { "textRaw": "`parent` {module | null | undefined}", "type": "module | null | undefined", "name": "parent", "meta": { "added": [ "v0.1.16" ], "deprecated": [ "v14.6.0", "v12.19.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Please use [`require.main`][] and [`module.children`][] instead.", "desc": "The module that first required this one, or null
if the current module is the\nentry point of the current process, or undefined
if the module was loaded by\nsomething that is not a CommonJS module (E.G.: REPL or import
).
The directory name of the module. This is usually the same as the\npath.dirname()
of the module.id
.
The search paths for the module.
" } ], "methods": [ { "textRaw": "`module.require(id)`", "type": "method", "name": "require", "meta": { "added": [ "v0.5.1" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {any} exported module content", "name": "return", "type": "any", "desc": "exported module content" }, "params": [ { "textRaw": "`id` {string}", "name": "id", "type": "string" } ] } ], "desc": "The module.require()
method provides a way to load a module as if\nrequire()
was called from the original module.
In order to do this, it is necessary to get a reference to the module
object.\nSince require()
returns the module.exports
, and the module
is typically\nonly available within a specific module's code, it must be explicitly exported\nin order to be used.
Provides general utility methods when interacting with instances of\nModule
, the module
variable often seen in CommonJS modules. Accessed\nvia import 'node:module'
or require('node:module')
.
A list of the names of all modules provided by Node.js. Can be used to verify\nif a module is maintained by a third party or not.
\nmodule
in this context isn't the same object that's provided\nby the module wrapper. To access it, require the Module
module:
// module.mjs\n// In an ECMAScript module\nimport { builtinModules as builtin } from 'node:module';\n
\n// module.cjs\n// In a CommonJS module\nconst builtin = require('node:module').builtinModules;\n
"
}
],
"methods": [
{
"textRaw": "`module.createRequire(filename)`",
"type": "method",
"name": "createRequire",
"meta": {
"added": [
"v12.2.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {require} Require function",
"name": "return",
"type": "require",
"desc": "Require function"
},
"params": [
{
"textRaw": "`filename` {string|URL} Filename to be used to construct the require function. Must be a file URL object, file URL string, or absolute path string.",
"name": "filename",
"type": "string|URL",
"desc": "Filename to be used to construct the require function. Must be a file URL object, file URL string, or absolute path string."
}
]
}
],
"desc": "import { createRequire } from 'node:module';\nconst require = createRequire(import.meta.url);\n\n// sibling-module.js is a CommonJS module.\nconst siblingModule = require('./sibling-module');\n
"
},
{
"textRaw": "`module.isBuiltin(moduleName)`",
"type": "method",
"name": "isBuiltin",
"meta": {
"added": [
"v18.6.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} returns true if the module is builtin else returns false",
"name": "return",
"type": "boolean",
"desc": "returns true if the module is builtin else returns false"
},
"params": [
{
"textRaw": "`moduleName` {string} name of the module",
"name": "moduleName",
"type": "string",
"desc": "name of the module"
}
]
}
],
"desc": "import { isBuiltin } from 'node:module';\nisBuiltin('node:fs'); // true\nisBuiltin('fs'); // true\nisBuiltin('wss'); // false\n
"
},
{
"textRaw": "`module.register(specifier[, parentURL][, options])`",
"type": "method",
"name": "register",
"meta": {
"added": [
"v20.6.0"
],
"changes": [
{
"version": "v20.8.0",
"pr-url": "https://github.com/nodejs/node/pull/49655",
"description": "Add support for WHATWG URL instances."
}
]
},
"stability": 1,
"stabilityText": ".2 - Release candidate",
"signatures": [
{
"params": [
{
"textRaw": "`specifier` {string|URL} Customization hooks to be registered; this should be the same string that would be passed to `import()`, except that if it is relative, it is resolved relative to `parentURL`.",
"name": "specifier",
"type": "string|URL",
"desc": "Customization hooks to be registered; this should be the same string that would be passed to `import()`, except that if it is relative, it is resolved relative to `parentURL`."
},
{
"textRaw": "`parentURL` {string|URL} If you want to resolve `specifier` relative to a base URL, such as `import.meta.url`, you can pass that URL here. **Default:** `'data:'`",
"name": "parentURL",
"type": "string|URL",
"default": "`'data:'`",
"desc": "If you want to resolve `specifier` relative to a base URL, such as `import.meta.url`, you can pass that URL here."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`parentURL` {string|URL} If you want to resolve `specifier` relative to a base URL, such as `import.meta.url`, you can pass that URL here. This property is ignored if the `parentURL` is supplied as the second argument. **Default:** `'data:'`",
"name": "parentURL",
"type": "string|URL",
"default": "`'data:'`",
"desc": "If you want to resolve `specifier` relative to a base URL, such as `import.meta.url`, you can pass that URL here. This property is ignored if the `parentURL` is supplied as the second argument."
},
{
"textRaw": "`data` {any} Any arbitrary, cloneable JavaScript value to pass into the [`initialize`][] hook.",
"name": "data",
"type": "any",
"desc": "Any arbitrary, cloneable JavaScript value to pass into the [`initialize`][] hook."
},
{
"textRaw": "`transferList` {Object\\[]} [transferrable objects][] to be passed into the `initialize` hook.",
"name": "transferList",
"type": "Object\\[]",
"desc": "[transferrable objects][] to be passed into the `initialize` hook."
}
]
}
]
}
],
"desc": "Register a module that exports hooks that customize Node.js module\nresolution and loading behavior. See Customization hooks.
" }, { "textRaw": "`module.syncBuiltinESMExports()`", "type": "method", "name": "syncBuiltinESMExports", "meta": { "added": [ "v12.12.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "The module.syncBuiltinESMExports()
method updates all the live bindings for\nbuiltin ES Modules to match the properties of the CommonJS exports. It\ndoes not add or remove exported names from the ES Modules.
const fs = require('node:fs');\nconst assert = require('node:assert');\nconst { syncBuiltinESMExports } = require('node:module');\n\nfs.readFile = newAPI;\n\ndelete fs.readFileSync;\n\nfunction newAPI() {\n // ...\n}\n\nfs.newAPI = newAPI;\n\nsyncBuiltinESMExports();\n\nimport('node:fs').then((esmFS) => {\n // It syncs the existing readFile property with the new value\n assert.strictEqual(esmFS.readFile, newAPI);\n // readFileSync has been deleted from the required fs\n assert.strictEqual('readFileSync' in fs, false);\n // syncBuiltinESMExports() does not remove readFileSync from esmFS\n assert.strictEqual('readFileSync' in esmFS, true);\n // syncBuiltinESMExports() does not add names\n assert.strictEqual(esmFS.newAPI, undefined);\n});\n
\n" } ], "type": "module", "displayName": "The `Module` object" }, { "textRaw": "Source map v3 support", "name": "source_map_v3_support", "meta": { "added": [ "v13.7.0", "v12.17.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "desc": "
Helpers for interacting with the source map cache. This cache is\npopulated when source map parsing is enabled and\nsource map include directives are found in a modules' footer.
\nTo enable source map parsing, Node.js must be run with the flag\n--enable-source-maps
, or with code coverage enabled by setting\nNODE_V8_COVERAGE=dir
.
// module.mjs\n// In an ECMAScript module\nimport { findSourceMap, SourceMap } from 'node:module';\n
\n// module.cjs\n// In a CommonJS module\nconst { findSourceMap, SourceMap } = require('node:module');\n
\n\n",
"methods": [
{
"textRaw": "`module.findSourceMap(path)`",
"type": "method",
"name": "findSourceMap",
"meta": {
"added": [
"v13.7.0",
"v12.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {module.SourceMap|undefined} Returns `module.SourceMap` if a source map is found, `undefined` otherwise.",
"name": "return",
"type": "module.SourceMap|undefined",
"desc": "Returns `module.SourceMap` if a source map is found, `undefined` otherwise."
},
"params": [
{
"textRaw": "`path` {string}",
"name": "path",
"type": "string"
}
]
}
],
"desc": "path
is the resolved path for the file for which a corresponding source map\nshould be fetched.
Getter for the payload used to construct the SourceMap
instance.
Given a line offset and column offset in the generated source\nfile, returns an object representing the SourceMap range in the\noriginal file if found, or an empty object if not.
\nThe object returned contains the following keys:
\nThe returned value represents the raw range as it appears in the\nSourceMap, based on zero-indexed offsets, not 1-indexed line and\ncolumn numbers as they appear in Error messages and CallSite\nobjects.
\nTo get the corresponding 1-indexed line and column numbers from a\nlineNumber and columnNumber as they are reported by Error stacks\nand CallSite objects, use sourceMap.findOrigin(lineNumber, columnNumber)
Given a 1-indexed lineNumber
and columnNumber
from a call site in\nthe generated source, find the corresponding call site location\nin the original source.
If the lineNumber
and columnNumber
provided are not found in any\nsource map, then an empty object is returned. Otherwise, the\nreturned object contains the following keys:
Creates a new sourceMap
instance.
payload
is an object with keys matching the Source map v3 format:
file
: <string>version
: <number>sources
: <string[]>sourcesContent
: <string[]>names
: <string[]>mappings
: <string>sourceRoot
: <string>lineLengths
is an optional array of the length of each line in the\ngenerated code.
", "miscs": [ { "textRaw": "Enabling", "name": "enabling", "desc": "
Module resolution and loading can be customized by registering a file which\nexports a set of hooks. This can be done using the register
method\nfrom node:module
, which you can run before your application code by\nusing the --import
flag:
node --import ./register-hooks.js ./my-app.js\n
\n// register-hooks.js\nimport { register } from 'node:module';\n\nregister('./hooks.mjs', import.meta.url);\n
\n// register-hooks.js\nconst { register } = require('node:module');\nconst { pathToFileURL } = require('node:url');\n\nregister('./hooks.mjs', pathToFileURL(__filename));\n
\nThe file passed to --import
can also be an export from a dependency:
node --import some-package/register ./my-app.js\n
\nWhere some-package
has an \"exports\"
field defining the /register
\nexport to map to a file that calls register()
, like the following register-hooks.js
\nexample.
Using --import
ensures that the hooks are registered before any application\nfiles are imported, including the entry point of the application. Alternatively,\nregister
can be called from the entry point, but dynamic import()
must be\nused for any code that should be run after the hooks are registered:
import { register } from 'node:module';\n\nregister('http-to-https', import.meta.url);\n\n// Because this is a dynamic `import()`, the `http-to-https` hooks will run\n// to handle `./my-app.js` and any other files it imports or requires.\nawait import('./my-app.js');\n
\nconst { register } = require('node:module');\nconst { pathToFileURL } = require('node:url');\n\nregister('http-to-https', pathToFileURL(__filename));\n\n// Because this is a dynamic `import()`, the `http-to-https` hooks will run\n// to handle `./my-app.js` and any other files it imports or requires.\nimport('./my-app.js');\n
\nIn this example, we are registering the http-to-https
hooks, but they will\nonly be available for subsequently imported modules—in this case, my-app.js
\nand anything it references via import
(and optionally require
). If the\nimport('./my-app.js')
had instead been a static import './my-app.js'
, the\napp would have already been loaded before the http-to-https
hooks were\nregistered. This due to the ES modules specification, where static imports are\nevaluated from the leaves of the tree first, then back to the trunk. There can\nbe static imports within my-app.js
, which will not be evaluated until\nmy-app.js
is dynamically imported.
my-app.js
can also be CommonJS. Customization hooks will run for any\nmodules that it references via import
(and optionally require
).
Finally, if all you want to do is register hooks before your app runs and you\ndon't want to create a separate file for that purpose, you can pass a data:
\nURL to --import
:
node --import 'data:text/javascript,import { register } from \"node:module\"; import { pathToFileURL } from \"node:url\"; register(\"http-to-https\", pathToFileURL(\"./\"));' ./my-app.js\n
",
"type": "misc",
"displayName": "Enabling"
},
{
"textRaw": "Chaining",
"name": "chaining",
"desc": "It's possible to call register
more than once:
// entrypoint.mjs\nimport { register } from 'node:module';\n\nregister('./foo.mjs', import.meta.url);\nregister('./bar.mjs', import.meta.url);\nawait import('./my-app.mjs');\n
\n// entrypoint.cjs\nconst { register } = require('node:module');\nconst { pathToFileURL } = require('node:url');\n\nconst parentURL = pathToFileURL(__filename);\nregister('./foo.mjs', parentURL);\nregister('./bar.mjs', parentURL);\nimport('./my-app.mjs');\n
\nIn this example, the registered hooks will form chains. These chains run\nlast-in, first out (LIFO). If both foo.mjs
and bar.mjs
define a resolve
\nhook, they will be called like so (note the right-to-left):\nnode's default ← ./foo.mjs
← ./bar.mjs
\n(starting with ./bar.mjs
, then ./foo.mjs
, then the Node.js default).\nThe same applies to all the other hooks.
The registered hooks also affect register
itself. In this example,\nbar.mjs
will be resolved and loaded via the hooks registered by foo.mjs
\n(because foo
's hooks will have already been added to the chain). This allows\nfor things like writing hooks in non-JavaScript languages, so long as\nearlier registered hooks transpile into JavaScript.
The register
method cannot be called from within the module that defines the\nhooks.
Module customization hooks run on a dedicated thread, separate from the main\nthread that runs application code. This means mutating global variables won't\naffect the other thread(s), and message channels must be used to communicate\nbetween the threads.
\nThe register
method can be used to pass data to an initialize
hook. The\ndata passed to the hook may include transferrable objects like ports.
import { register } from 'node:module';\nimport { MessageChannel } from 'node:worker_threads';\n\n// This example demonstrates how a message channel can be used to\n// communicate with the hooks, by sending `port2` to the hooks.\nconst { port1, port2 } = new MessageChannel();\n\nport1.on('message', (msg) => {\n console.log(msg);\n});\n\nregister('./my-hooks.mjs', {\n parentURL: import.meta.url,\n data: { number: 1, port: port2 },\n transferList: [port2],\n});\n
\nconst { register } = require('node:module');\nconst { pathToFileURL } = require('node:url');\nconst { MessageChannel } = require('node:worker_threads');\n\n// This example showcases how a message channel can be used to\n// communicate with the hooks, by sending `port2` to the hooks.\nconst { port1, port2 } = new MessageChannel();\n\nport1.on('message', (msg) => {\n console.log(msg);\n});\n\nregister('./my-hooks.mjs', {\n parentURL: pathToFileURL(__filename),\n data: { number: 1, port: port2 },\n transferList: [port2],\n});\n
",
"type": "misc",
"displayName": "Communication with module customization hooks"
},
{
"textRaw": "Hooks",
"name": "hooks",
"desc": "The register
method can be used to register a module that exports a set of\nhooks. The hooks are functions that are called by Node.js to customize the\nmodule resolution and loading process. The exported functions must have specific\nnames and signatures, and they must be exported as named exports.
export async function initialize({ number, port }) {\n // Receives data from `register`.\n}\n\nexport async function resolve(specifier, context, nextResolve) {\n // Take an `import` or `require` specifier and resolve it to a URL.\n}\n\nexport async function load(url, context, nextLoad) {\n // Take a resolved URL and return the source code to be evaluated.\n}\n
\nHooks are part of a chain, even if that chain consists of only one\ncustom (user-provided) hook and the default hook, which is always present. Hook\nfunctions nest: each one must always return a plain object, and chaining happens\nas a result of each function calling next<hookName>()
, which is a reference to\nthe subsequent loader's hook (in LIFO order).
A hook that returns a value lacking a required property triggers an exception. A\nhook that returns without calling next<hookName>()
and without returning\nshortCircuit: true
also triggers an exception. These errors are to help\nprevent unintentional breaks in the chain. Return shortCircuit: true
from a\nhook to signal that the chain is intentionally ending at your hook.
Hooks are run in a separate thread, isolated from the main thread where\napplication code runs. That means it is a different realm. The hooks thread\nmay be terminated by the main thread at any time, so do not depend on\nasynchronous operations (like console.log
) to complete.
The initialize
hook provides a way to define a custom function that runs in\nthe hooks thread when the hooks module is initialized. Initialization happens\nwhen the hooks module is registered via register
.
This hook can receive data from a register
invocation, including\nports and other transferrable objects. The return value of initialize
can be a\n<Promise>, in which case it will be awaited before the main application thread\nexecution resumes.
Module customization code:
\n// path-to-my-hooks.js\n\nexport async function initialize({ number, port }) {\n port.postMessage(`increment: ${number + 1}`);\n}\n
\nCaller code:
\nimport assert from 'node:assert';\nimport { register } from 'node:module';\nimport { MessageChannel } from 'node:worker_threads';\n\n// This example showcases how a message channel can be used to communicate\n// between the main (application) thread and the hooks running on the hooks\n// thread, by sending `port2` to the `initialize` hook.\nconst { port1, port2 } = new MessageChannel();\n\nport1.on('message', (msg) => {\n assert.strictEqual(msg, 'increment: 2');\n});\n\nregister('./path-to-my-hooks.js', {\n parentURL: import.meta.url,\n data: { number: 1, port: port2 },\n transferList: [port2],\n});\n
\nconst assert = require('node:assert');\nconst { register } = require('node:module');\nconst { pathToFileURL } = require('node:url');\nconst { MessageChannel } = require('node:worker_threads');\n\n// This example showcases how a message channel can be used to communicate\n// between the main (application) thread and the hooks running on the hooks\n// thread, by sending `port2` to the `initialize` hook.\nconst { port1, port2 } = new MessageChannel();\n\nport1.on('message', (msg) => {\n assert.strictEqual(msg, 'increment: 2');\n});\n\nregister('./path-to-my-hooks.js', {\n parentURL: pathToFileURL(__filename),\n data: { number: 1, port: port2 },\n transferList: [port2],\n});\n
"
},
{
"textRaw": "`resolve(specifier, context, nextResolve)`",
"type": "method",
"name": "resolve",
"meta": {
"changes": [
{
"version": "v21.0.0",
"pr-url": "https://github.com/nodejs/node/pull/50140",
"description": "The property `context.importAssertions` is replaced with `context.importAttributes`. Using the old name is still supported and will emit an experimental warning."
},
{
"version": [
"v18.6.0",
"v16.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/42623",
"description": "Add support for chaining resolve hooks. Each hook must either call `nextResolve()` or include a `shortCircuit` property set to `true` in its return."
},
{
"version": [
"v17.1.0",
"v16.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40250",
"description": "Add support for import assertions."
}
]
},
"stability": 1,
"stabilityText": ".2 - Release candidate",
"signatures": [
{
"return": {
"textRaw": "Returns: {Object|Promise}",
"name": "return",
"type": "Object|Promise",
"options": [
{
"textRaw": "`format` {string|null|undefined} A hint to the load hook (it might be ignored) `'builtin' | 'commonjs' | 'json' | 'module' | 'wasm'`",
"name": "format",
"type": "string|null|undefined",
"desc": "A hint to the load hook (it might be ignored) `'builtin' | 'commonjs' | 'json' | 'module' | 'wasm'`"
},
{
"textRaw": "`importAttributes` {Object|undefined} The import attributes to use when caching the module (optional; if excluded the input will be used)",
"name": "importAttributes",
"type": "Object|undefined",
"desc": "The import attributes to use when caching the module (optional; if excluded the input will be used)"
},
{
"textRaw": "`shortCircuit` {undefined|boolean} A signal that this hook intends to terminate the chain of `resolve` hooks. **Default:** `false`",
"name": "shortCircuit",
"type": "undefined|boolean",
"default": "`false`",
"desc": "A signal that this hook intends to terminate the chain of `resolve` hooks."
},
{
"textRaw": "`url` {string} The absolute URL to which this input resolves",
"name": "url",
"type": "string",
"desc": "The absolute URL to which this input resolves"
}
]
},
"params": [
{
"textRaw": "`specifier` {string}",
"name": "specifier",
"type": "string"
},
{
"textRaw": "`context` {Object}",
"name": "context",
"type": "Object",
"options": [
{
"textRaw": "`conditions` {string\\[]} Export conditions of the relevant `package.json`",
"name": "conditions",
"type": "string\\[]",
"desc": "Export conditions of the relevant `package.json`"
},
{
"textRaw": "`importAttributes` {Object} An object whose key-value pairs represent the attributes for the module to import",
"name": "importAttributes",
"type": "Object",
"desc": "An object whose key-value pairs represent the attributes for the module to import"
},
{
"textRaw": "`parentURL` {string|undefined} The module importing this one, or undefined if this is the Node.js entry point",
"name": "parentURL",
"type": "string|undefined",
"desc": "The module importing this one, or undefined if this is the Node.js entry point"
}
]
},
{
"textRaw": "`nextResolve` {Function} The subsequent `resolve` hook in the chain, or the Node.js default `resolve` hook after the last user-supplied `resolve` hook",
"name": "nextResolve",
"type": "Function",
"desc": "The subsequent `resolve` hook in the chain, or the Node.js default `resolve` hook after the last user-supplied `resolve` hook",
"options": [
{
"textRaw": "`specifier` {string}",
"name": "specifier",
"type": "string"
},
{
"textRaw": "`context` {Object}",
"name": "context",
"type": "Object"
}
]
}
]
}
],
"desc": "\n\nWarning Despite support for returning promises and async functions, calls\nto
\nresolve
may block the main thread which can impact performance.
The resolve
hook chain is responsible for telling Node.js where to find and\nhow to cache a given import
statement or expression, or require
call. It can\noptionally return a format (such as 'module'
) as a hint to the load
hook. If\na format is specified, the load
hook is ultimately responsible for providing\nthe final format
value (and it is free to ignore the hint provided by\nresolve
); if resolve
provides a format
, a custom load
hook is required\neven if only to pass the value to the Node.js default load
hook.
Import type attributes are part of the cache key for saving loaded modules into\nthe internal module cache. The resolve
hook is responsible for returning an\nimportAttributes
object if the module should be cached with different\nattributes than were present in the source code.
The conditions
property in context
is an array of conditions for\npackage exports conditions that apply to this resolution\nrequest. They can be used for looking up conditional mappings elsewhere or to\nmodify the list when calling the default resolution logic.
The current package exports conditions are always in\nthe context.conditions
array passed into the hook. To guarantee default\nNode.js module specifier resolution behavior when calling defaultResolve
, the\ncontext.conditions
array passed to it must include all elements of the\ncontext.conditions
array originally passed into the resolve
hook.
export async function resolve(specifier, context, nextResolve) {\n const { parentURL = null } = context;\n\n if (Math.random() > 0.5) { // Some condition.\n // For some or all specifiers, do some custom logic for resolving.\n // Always return an object of the form {url: <string>}.\n return {\n shortCircuit: true,\n url: parentURL ?\n new URL(specifier, parentURL).href :\n new URL(specifier).href,\n };\n }\n\n if (Math.random() < 0.5) { // Another condition.\n // When calling `defaultResolve`, the arguments can be modified. In this\n // case it's adding another value for matching conditional exports.\n return nextResolve(specifier, {\n ...context,\n conditions: [...context.conditions, 'another-condition'],\n });\n }\n\n // Defer to the next hook in the chain, which would be the\n // Node.js default resolve if this is the last user-specified loader.\n return nextResolve(specifier);\n}\n
"
},
{
"textRaw": "`load(url, context, nextLoad)`",
"type": "method",
"name": "load",
"meta": {
"changes": [
{
"version": "v20.6.0",
"pr-url": "https://github.com/nodejs/node/pull/47999",
"description": "Add support for `source` with format `commonjs`."
},
{
"version": [
"v18.6.0",
"v16.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/42623",
"description": "Add support for chaining load hooks. Each hook must either call `nextLoad()` or include a `shortCircuit` property set to `true` in its return."
}
]
},
"stability": 1,
"stabilityText": ".2 - Release candidate",
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object",
"options": [
{
"textRaw": "`format` {string}",
"name": "format",
"type": "string"
},
{
"textRaw": "`shortCircuit` {undefined|boolean} A signal that this hook intends to terminate the chain of `resolve` hooks. **Default:** `false`",
"name": "shortCircuit",
"type": "undefined|boolean",
"default": "`false`",
"desc": "A signal that this hook intends to terminate the chain of `resolve` hooks."
},
{
"textRaw": "`source` {string|ArrayBuffer|TypedArray} The source for Node.js to evaluate",
"name": "source",
"type": "string|ArrayBuffer|TypedArray",
"desc": "The source for Node.js to evaluate"
}
]
},
"params": [
{
"textRaw": "`url` {string} The URL returned by the `resolve` chain",
"name": "url",
"type": "string",
"desc": "The URL returned by the `resolve` chain"
},
{
"textRaw": "`context` {Object}",
"name": "context",
"type": "Object",
"options": [
{
"textRaw": "`conditions` {string\\[]} Export conditions of the relevant `package.json`",
"name": "conditions",
"type": "string\\[]",
"desc": "Export conditions of the relevant `package.json`"
},
{
"textRaw": "`format` {string|null|undefined} The format optionally supplied by the `resolve` hook chain",
"name": "format",
"type": "string|null|undefined",
"desc": "The format optionally supplied by the `resolve` hook chain"
},
{
"textRaw": "`importAttributes` {Object}",
"name": "importAttributes",
"type": "Object"
}
]
},
{
"textRaw": "`nextLoad` {Function} The subsequent `load` hook in the chain, or the Node.js default `load` hook after the last user-supplied `load` hook",
"name": "nextLoad",
"type": "Function",
"desc": "The subsequent `load` hook in the chain, or the Node.js default `load` hook after the last user-supplied `load` hook",
"options": [
{
"textRaw": "`specifier` {string}",
"name": "specifier",
"type": "string"
},
{
"textRaw": "`context` {Object}",
"name": "context",
"type": "Object"
}
]
}
]
}
],
"desc": "The load
hook provides a way to define a custom method of determining how a\nURL should be interpreted, retrieved, and parsed. It is also in charge of\nvalidating the import assertion.
The final value of format
must be one of the following:
format | \nDescription | \nAcceptable types for source returned by load | \n
---|---|---|
'builtin' | \nLoad a Node.js builtin module | \nNot applicable | \n
'commonjs' | \nLoad a Node.js CommonJS module | \n{ string , ArrayBuffer , TypedArray , null , undefined } | \n
'json' | \nLoad a JSON file | \n{ string , ArrayBuffer , TypedArray } | \n
'module' | \nLoad an ES module | \n{ string , ArrayBuffer , TypedArray } | \n
'wasm' | \nLoad a WebAssembly module | \n{ ArrayBuffer , TypedArray } | \n
The value of source
is ignored for type 'builtin'
because currently it is\nnot possible to replace the value of a Node.js builtin (core) module.
Omitting vs providing a source
for 'commonjs'
has very different effects:
source
is provided, all require
calls from this module will be\nprocessed by the ESM loader with registered resolve
and load
hooks; all\nrequire.resolve
calls from this module will be processed by the ESM loader\nwith registered resolve
hooks; only a subset of the CommonJS API will be\navailable (e.g. no require.extensions
, no require.cache
, no\nrequire.resolve.paths
) and monkey-patching on the CommonJS module loader\nwill not apply.source
is undefined or null
, it will be handled by the CommonJS module\nloader and require
/require.resolve
calls will not go through the\nregistered hooks. This behavior for nullish source
is temporary — in the\nfuture, nullish source
will not be supported.When node
is run with --experimental-default-type=commonjs
, the Node.js\ninternal load
implementation, which is the value of next
for the\nlast hook in the load
chain, returns null
for source
when format
is\n'commonjs'
for backward compatibility. Here is an example hook that would\nopt-in to using the non-default behavior:
import { readFile } from 'node:fs/promises';\n\nexport async function load(url, context, nextLoad) {\n const result = await nextLoad(url, context);\n if (result.format === 'commonjs') {\n result.source ??= await readFile(new URL(result.responseURL ?? url));\n }\n return result;\n}\n
\n\n\nWarning: The ESM
\nload
hook and namespaced exports from CommonJS modules\nare incompatible. Attempting to use them together will result in an empty\nobject from the import. This may be addressed in the future.
\n\nThese types all correspond to classes defined in ECMAScript.
\n
ArrayBuffer
object is a SharedArrayBuffer
.TypedArray
object is a Uint8Array
.If the source value of a text-based format (i.e., 'json'
, 'module'
)\nis not a string, it is converted to a string using util.TextDecoder
.
The load
hook provides a way to define a custom method for retrieving the\nsource code of a resolved URL. This would allow a loader to potentially avoid\nreading files from disk. It could also be used to map an unrecognized format to\na supported one, for example yaml
to module
.
export async function load(url, context, nextLoad) {\n const { format } = context;\n\n if (Math.random() > 0.5) { // Some condition\n /*\n For some or all URLs, do some custom logic for retrieving the source.\n Always return an object of the form {\n format: <string>,\n source: <string|buffer>,\n }.\n */\n return {\n format,\n shortCircuit: true,\n source: '...',\n };\n }\n\n // Defer to the next hook in the chain.\n return nextLoad(url);\n}\n
\nIn a more advanced scenario, this can also be used to transform an unsupported\nsource to a supported one (see Examples below).
\nThe various module customization hooks can be used together to accomplish\nwide-ranging customizations of the Node.js code loading and evaluation\nbehaviors.
" } ], "modules": [ { "textRaw": "Import from HTTPS", "name": "import_from_https", "desc": "In current Node.js, specifiers starting with https://
are experimental (see\nHTTPS and HTTP imports).
The hook below registers hooks to enable rudimentary support for such\nspecifiers. While this may seem like a significant improvement to Node.js core\nfunctionality, there are substantial downsides to actually using these hooks:\nperformance is much slower than loading files from disk, there is no caching,\nand there is no security.
\n// https-hooks.mjs\nimport { get } from 'node:https';\n\nexport function load(url, context, nextLoad) {\n // For JavaScript to be loaded over the network, we need to fetch and\n // return it.\n if (url.startsWith('https://')) {\n return new Promise((resolve, reject) => {\n get(url, (res) => {\n let data = '';\n res.setEncoding('utf8');\n res.on('data', (chunk) => data += chunk);\n res.on('end', () => resolve({\n // This example assumes all network-provided JavaScript is ES module\n // code.\n format: 'module',\n shortCircuit: true,\n source: data,\n }));\n }).on('error', (err) => reject(err));\n });\n }\n\n // Let Node.js handle all other URLs.\n return nextLoad(url);\n}\n
\n// main.mjs\nimport { VERSION } from 'https://coffeescript.org/browser-compiler-modern/coffeescript.js';\n\nconsole.log(VERSION);\n
\nWith the preceding hooks module, running\nnode --import 'data:text/javascript,import { register } from \"node:module\"; import { pathToFileURL } from \"node:url\"; register(pathToFileURL(\"./https-hooks.mjs\"));' ./main.mjs
\nprints the current version of CoffeeScript per the module at the URL in\nmain.mjs
.
Sources that are in formats Node.js doesn't understand can be converted into\nJavaScript using the load
hook.
This is less performant than transpiling source files before running Node.js;\ntranspiler hooks should only be used for development and testing purposes.
\n// coffeescript-hooks.mjs\nimport { readFile } from 'node:fs/promises';\nimport { dirname, extname, resolve as resolvePath } from 'node:path';\nimport { cwd } from 'node:process';\nimport { fileURLToPath, pathToFileURL } from 'node:url';\nimport coffeescript from 'coffeescript';\n\nconst extensionsRegex = /\\.(coffee|litcoffee|coffee\\.md)$/;\n\nexport async function load(url, context, nextLoad) {\n if (extensionsRegex.test(url)) {\n // CoffeeScript files can be either CommonJS or ES modules, so we want any\n // CoffeeScript file to be treated by Node.js the same as a .js file at the\n // same location. To determine how Node.js would interpret an arbitrary .js\n // file, search up the file system for the nearest parent package.json file\n // and read its \"type\" field.\n const format = await getPackageType(url);\n\n const { source: rawSource } = await nextLoad(url, { ...context, format });\n // This hook converts CoffeeScript source code into JavaScript source code\n // for all imported CoffeeScript files.\n const transformedSource = coffeescript.compile(rawSource.toString(), url);\n\n return {\n format,\n shortCircuit: true,\n source: transformedSource,\n };\n }\n\n // Let Node.js handle all other URLs.\n return nextLoad(url);\n}\n\nasync function getPackageType(url) {\n // `url` is only a file path during the first iteration when passed the\n // resolved url from the load() hook\n // an actual file path from load() will contain a file extension as it's\n // required by the spec\n // this simple truthy check for whether `url` contains a file extension will\n // work for most projects but does not cover some edge-cases (such as\n // extensionless files or a url ending in a trailing space)\n const isFilePath = !!extname(url);\n // If it is a file path, get the directory it's in\n const dir = isFilePath ?\n dirname(fileURLToPath(url)) :\n url;\n // Compose a file path to a package.json in the same directory,\n // which may or may not exist\n const packagePath = resolvePath(dir, 'package.json');\n // Try to read the possibly nonexistent package.json\n const type = await readFile(packagePath, { encoding: 'utf8' })\n .then((filestring) => JSON.parse(filestring).type)\n .catch((err) => {\n if (err?.code !== 'ENOENT') console.error(err);\n });\n // If package.json existed and contained a `type` field with a value, voilà\n if (type) return type;\n // Otherwise, (if not at the root) continue checking the next directory up\n // If at the root, stop and return false\n return dir.length > 1 && getPackageType(resolvePath(dir, '..'));\n}\n
\n# main.coffee\nimport { scream } from './scream.coffee'\nconsole.log scream 'hello, world'\n\nimport { version } from 'node:process'\nconsole.log \"Brought to you by Node.js version #{version}\"\n
\n# scream.coffee\nexport scream = (str) -> str.toUpperCase()\n
\nWith the preceding hooks module, running\nnode --import 'data:text/javascript,import { register } from \"node:module\"; import { pathToFileURL } from \"node:url\"; register(pathToFileURL(\"./coffeescript-hooks.mjs\"));' ./main.coffee
\ncauses main.coffee
to be turned into JavaScript after its source code is\nloaded from disk but before Node.js executes it; and so on for any .coffee
,\n.litcoffee
or .coffee.md
files referenced via import
statements of any\nloaded file.
The previous two examples defined load
hooks. This is an example of a\nresolve
hook. This hooks module reads an import-map.json
file that defines\nwhich specifiers to override to other URLs (this is a very simplistic\nimplementation of a small subset of the \"import maps\" specification).
// import-map-hooks.js\nimport fs from 'node:fs/promises';\n\nconst { imports } = JSON.parse(await fs.readFile('import-map.json'));\n\nexport async function resolve(specifier, context, nextResolve) {\n if (Object.hasOwn(imports, specifier)) {\n return nextResolve(imports[specifier], context);\n }\n\n return nextResolve(specifier, context);\n}\n
\nWith these files:
\n// main.js\nimport 'a-module';\n
\n// import-map.json\n{\n \"imports\": {\n \"a-module\": \"./some-module.js\"\n }\n}\n
\n// some-module.js\nconsole.log('some module!');\n
\nRunning node --import 'data:text/javascript,import { register } from \"node:module\"; import { pathToFileURL } from \"node:url\"; register(pathToFileURL(\"./import-map-hooks.js\"));' main.js
\nshould print some module!
.
\n\nStability: 2 - Stable
\n
Source Code: lib/net.js
\nThe node:net
module provides an asynchronous network API for creating stream-based\nTCP or IPC servers (net.createServer()
) and clients\n(net.createConnection()
).
It can be accessed using:
\nconst net = require('node:net');\n
",
"modules": [
{
"textRaw": "IPC support",
"name": "ipc_support",
"desc": "The node:net
module supports IPC with named pipes on Windows, and Unix domain\nsockets on other operating systems.
net.connect()
, net.createConnection()
, server.listen()
, and\nsocket.connect()
take a path
parameter to identify IPC endpoints.
On Unix, the local domain is also known as the Unix domain. The path is a\nfile system pathname. It gets truncated to an OS-dependent length of\nsizeof(sockaddr_un.sun_path) - 1
. Typical values are 107 bytes on Linux and\n103 bytes on macOS. If a Node.js API abstraction creates the Unix domain socket,\nit will unlink the Unix domain socket as well. For example,\nnet.createServer()
may create a Unix domain socket and\nserver.close()
will unlink it. But if a user creates the Unix domain\nsocket outside of these abstractions, the user will need to remove it. The same\napplies when a Node.js API creates a Unix domain socket but the program then\ncrashes. In short, a Unix domain socket will be visible in the file system and\nwill persist until unlinked. On Linux, You can use Unix abstract socket by adding\n\\0
to the beginning of the path, such as \\0abstract
. The path to the Unix\nabstract socket is not visible in the file system and it will disappear automatically\nwhen all open references to the socket are closed.
On Windows, the local domain is implemented using a named pipe. The path must\nrefer to an entry in \\\\?\\pipe\\
or \\\\.\\pipe\\
. Any characters are permitted,\nbut the latter may do some processing of pipe names, such as resolving ..
\nsequences. Despite how it might look, the pipe namespace is flat. Pipes will\nnot persist. They are removed when the last reference to them is closed.\nUnlike Unix domain sockets, Windows will close and remove the pipe when the\nowning process exits.
JavaScript string escaping requires paths to be specified with extra backslash\nescaping such as:
\nnet.createServer().listen(\n path.join('\\\\\\\\?\\\\pipe', process.cwd(), 'myctl'));\n
",
"type": "module",
"displayName": "Identifying paths for IPC connections"
}
],
"type": "module",
"displayName": "IPC support"
}
],
"classes": [
{
"textRaw": "Class: `net.BlockList`",
"type": "class",
"name": "net.BlockList",
"meta": {
"added": [
"v15.0.0",
"v14.18.0"
],
"changes": []
},
"desc": "The BlockList
object can be used with some network APIs to specify rules for\ndisabling inbound or outbound access to specific IP addresses, IP ranges, or\nIP subnets.
Adds a rule to block the given IP address.
" }, { "textRaw": "`blockList.addRange(start, end[, type])`", "type": "method", "name": "addRange", "meta": { "added": [ "v15.0.0", "v14.18.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`start` {string|net.SocketAddress} The starting IPv4 or IPv6 address in the range.", "name": "start", "type": "string|net.SocketAddress", "desc": "The starting IPv4 or IPv6 address in the range." }, { "textRaw": "`end` {string|net.SocketAddress} The ending IPv4 or IPv6 address in the range.", "name": "end", "type": "string|net.SocketAddress", "desc": "The ending IPv4 or IPv6 address in the range." }, { "textRaw": "`type` {string} Either `'ipv4'` or `'ipv6'`. **Default:** `'ipv4'`.", "name": "type", "type": "string", "default": "`'ipv4'`", "desc": "Either `'ipv4'` or `'ipv6'`." } ] } ], "desc": "Adds a rule to block a range of IP addresses from start
(inclusive) to\nend
(inclusive).
Adds a rule to block a range of IP addresses specified as a subnet mask.
" }, { "textRaw": "`blockList.check(address[, type])`", "type": "method", "name": "check", "meta": { "added": [ "v15.0.0", "v14.18.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`address` {string|net.SocketAddress} The IP address to check", "name": "address", "type": "string|net.SocketAddress", "desc": "The IP address to check" }, { "textRaw": "`type` {string} Either `'ipv4'` or `'ipv6'`. **Default:** `'ipv4'`.", "name": "type", "type": "string", "default": "`'ipv4'`", "desc": "Either `'ipv4'` or `'ipv6'`." } ] } ], "desc": "Returns true
if the given IP address matches any of the rules added to the\nBlockList
.
const blockList = new net.BlockList();\nblockList.addAddress('123.123.123.123');\nblockList.addRange('10.0.0.1', '10.0.0.10');\nblockList.addSubnet('8592:757c:efae:4e45::', 64, 'ipv6');\n\nconsole.log(blockList.check('123.123.123.123')); // Prints: true\nconsole.log(blockList.check('10.0.0.3')); // Prints: true\nconsole.log(blockList.check('222.111.111.222')); // Prints: false\n\n// IPv6 notation for IPv4 addresses works:\nconsole.log(blockList.check('::ffff:7b7b:7b7b', 'ipv6')); // Prints: true\nconsole.log(blockList.check('::ffff:123.123.123.123', 'ipv6')); // Prints: true\n
"
}
],
"properties": [
{
"textRaw": "`rules` Type: {string\\[]}",
"type": "string\\[]",
"name": "Type",
"meta": {
"added": [
"v15.0.0",
"v14.18.0"
],
"changes": []
},
"desc": "The list of rules added to the blocklist.
" } ] }, { "textRaw": "Class: `net.SocketAddress`", "type": "class", "name": "net.SocketAddress", "meta": { "added": [ "v15.14.0", "v14.18.0" ], "changes": [] }, "properties": [ { "textRaw": "`address` Type {string}", "type": "string", "name": "Type", "meta": { "added": [ "v15.14.0", "v14.18.0" ], "changes": [] }, "desc": "Either `'ipv4'` or `'ipv6'`." }, { "textRaw": "`family` Type {string} Either `'ipv4'` or `'ipv6'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.14.0", "v14.18.0" ], "changes": [] }, "desc": "Either `'ipv4'` or `'ipv6'`." }, { "textRaw": "`flowlabel` Type {number}", "type": "number", "name": "Type", "meta": { "added": [ "v15.14.0", "v14.18.0" ], "changes": [] } }, { "textRaw": "`port` Type {number}", "type": "number", "name": "Type", "meta": { "added": [ "v15.14.0", "v14.18.0" ], "changes": [] } } ], "signatures": [ { "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`address` {string} The network address as either an IPv4 or IPv6 string. **Default**: `'127.0.0.1'` if `family` is `'ipv4'`; `'::'` if `family` is `'ipv6'`.", "name": "address", "type": "string", "desc": "The network address as either an IPv4 or IPv6 string. **Default**: `'127.0.0.1'` if `family` is `'ipv4'`; `'::'` if `family` is `'ipv6'`." }, { "textRaw": "`family` {string} One of either `'ipv4'` or `'ipv6'`. **Default**: `'ipv4'`.", "name": "family", "type": "string", "desc": "One of either `'ipv4'` or `'ipv6'`. **Default**: `'ipv4'`." }, { "textRaw": "`flowlabel` {number} An IPv6 flow-label used only if `family` is `'ipv6'`.", "name": "flowlabel", "type": "number", "desc": "An IPv6 flow-label used only if `family` is `'ipv6'`." }, { "textRaw": "`port` {number} An IP port.", "name": "port", "type": "number", "desc": "An IP port." } ] } ] } ] }, { "textRaw": "Class: `net.Server`", "type": "class", "name": "net.Server", "meta": { "added": [ "v0.1.90" ], "changes": [] }, "desc": "This class is used to create a TCP or IPC server.
", "events": [ { "textRaw": "Event: `'close'`", "type": "event", "name": "close", "meta": { "added": [ "v0.5.0" ], "changes": [] }, "params": [], "desc": "Emitted when the server closes. If connections exist, this\nevent is not emitted until all connections are ended.
" }, { "textRaw": "Event: `'connection'`", "type": "event", "name": "connection", "meta": { "added": [ "v0.1.90" ], "changes": [] }, "params": [ { "textRaw": "{net.Socket} The connection object", "type": "net.Socket", "desc": "The connection object" } ], "desc": "Emitted when a new connection is made. socket
is an instance of\nnet.Socket
.
Emitted when an error occurs. Unlike net.Socket
, the 'close'
\nevent will not be emitted directly following this event unless\nserver.close()
is manually called. See the example in discussion of\nserver.listen()
.
Emitted when the server has been bound after calling server.listen()
.
When the number of connections reaches the threshold of server.maxConnections
,\nthe server will drop new connections and emit 'drop'
event instead. If it is a\nTCP server, the argument is as follows, otherwise the argument is undefined
.
data
<Object> The argument passed to event listener.\n\nReturns the bound address
, the address family
name, and port
of the server\nas reported by the operating system if listening on an IP socket\n(useful to find which port was assigned when getting an OS-assigned address):\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
.
For a server listening on a pipe or Unix domain socket, the name is returned\nas a string.
\nconst server = net.createServer((socket) => {\n socket.end('goodbye\\n');\n}).on('error', (err) => {\n // Handle errors here.\n throw err;\n});\n\n// Grab an arbitrary unused port.\nserver.listen(() => {\n console.log('opened server on', server.address());\n});\n
\nserver.address()
returns null
before the 'listening'
event has been\nemitted or after calling server.close()
.
Stops the server from accepting new connections and keeps existing\nconnections. This function is asynchronous, the server is finally closed\nwhen all connections are ended and the server emits a 'close'
event.\nThe optional callback
will be called once the 'close'
event occurs. Unlike\nthat event, it will be called with an Error
as its only argument if the server\nwas not open when it was closed.
Calls server.close()
and returns a promise that fulfills when the\nserver has closed.
Asynchronously get the number of concurrent connections on the server. Works\nwhen sockets were sent to forks.
\nCallback should take two arguments err
and count
.
Start a server listening for connections. A net.Server
can be a TCP or\nan IPC server depending on what it listens to.
Possible signatures:
\nserver.listen(handle[, backlog][, callback])
server.listen(options[, callback])
server.listen(path[, backlog][, callback])
\nfor IPC serversserver.listen([port[, host[, backlog]]][, callback])
\nfor TCP serversThis function is asynchronous. When the server starts listening, the\n'listening'
event will be emitted. The last parameter callback
\nwill be added as a listener for the 'listening'
event.
All listen()
methods can take a backlog
parameter to specify the maximum\nlength of the queue of pending connections. The actual length will be determined\nby the OS through sysctl settings such as tcp_max_syn_backlog
and somaxconn
\non Linux. The default value of this parameter is 511 (not 512).
All net.Socket
are set to SO_REUSEADDR
(see socket(7)
for\ndetails).
The server.listen()
method can be called again if and only if there was an\nerror during the first server.listen()
call or server.close()
has been\ncalled. Otherwise, an ERR_SERVER_ALREADY_LISTEN
error will be thrown.
One of the most common errors raised when listening is EADDRINUSE
.\nThis happens when another server is already listening on the requested\nport
/path
/handle
. One way to handle this would be to retry\nafter a certain amount of time:
server.on('error', (e) => {\n if (e.code === 'EADDRINUSE') {\n console.error('Address in use, retrying...');\n setTimeout(() => {\n server.close();\n server.listen(PORT, HOST);\n }, 1000);\n }\n});\n
",
"methods": [
{
"textRaw": "`server.listen(handle[, backlog][, callback])`",
"type": "method",
"name": "listen",
"meta": {
"added": [
"v0.5.10"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {net.Server}",
"name": "return",
"type": "net.Server"
},
"params": [
{
"textRaw": "`handle` {Object}",
"name": "handle",
"type": "Object"
},
{
"textRaw": "`backlog` {number} Common parameter of [`server.listen()`][] functions",
"name": "backlog",
"type": "number",
"desc": "Common parameter of [`server.listen()`][] functions"
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "Start a server listening for connections on a given handle
that has\nalready been bound to a port, a Unix domain socket, or a Windows named pipe.
The handle
object can be either a server, a socket (anything with an\nunderlying _handle
member), or an object with an fd
member that is a\nvalid file descriptor.
Listening on a file descriptor is not supported on Windows.
" }, { "textRaw": "`server.listen(options[, callback])`", "type": "method", "name": "listen", "meta": { "added": [ "v0.11.14" ], "changes": [ { "version": "v15.6.0", "pr-url": "https://github.com/nodejs/node/pull/36623", "description": "AbortSignal support was added." }, { "version": "v11.4.0", "pr-url": "https://github.com/nodejs/node/pull/23798", "description": "The `ipv6Only` option is supported." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {net.Server}", "name": "return", "type": "net.Server" }, "params": [ { "textRaw": "`options` {Object} Required. Supports the following properties:", "name": "options", "type": "Object", "desc": "Required. Supports the following properties:", "options": [ { "textRaw": "`port` {number}", "name": "port", "type": "number" }, { "textRaw": "`host` {string}", "name": "host", "type": "string" }, { "textRaw": "`path` {string} Will be ignored if `port` is specified. See [Identifying paths for IPC connections][].", "name": "path", "type": "string", "desc": "Will be ignored if `port` is specified. See [Identifying paths for IPC connections][]." }, { "textRaw": "`backlog` {number} Common parameter of [`server.listen()`][] functions.", "name": "backlog", "type": "number", "desc": "Common parameter of [`server.listen()`][] functions." }, { "textRaw": "`exclusive` {boolean} **Default:** `false`", "name": "exclusive", "type": "boolean", "default": "`false`" }, { "textRaw": "`readableAll` {boolean} For IPC servers makes the pipe readable for all users. **Default:** `false`.", "name": "readableAll", "type": "boolean", "default": "`false`", "desc": "For IPC servers makes the pipe readable for all users." }, { "textRaw": "`writableAll` {boolean} For IPC servers makes the pipe writable for all users. **Default:** `false`.", "name": "writableAll", "type": "boolean", "default": "`false`", "desc": "For IPC servers makes the pipe writable for all users." }, { "textRaw": "`ipv6Only` {boolean} For TCP servers, setting `ipv6Only` to `true` will disable dual-stack support, i.e., binding to host `::` won't make `0.0.0.0` be bound. **Default:** `false`.", "name": "ipv6Only", "type": "boolean", "default": "`false`", "desc": "For TCP servers, setting `ipv6Only` to `true` will disable dual-stack support, i.e., binding to host `::` won't make `0.0.0.0` be bound." }, { "textRaw": "`signal` {AbortSignal} An AbortSignal that may be used to close a listening server.", "name": "signal", "type": "AbortSignal", "desc": "An AbortSignal that may be used to close a listening server." } ] }, { "textRaw": "`callback` {Function} functions.", "name": "callback", "type": "Function", "desc": "functions." } ] } ], "desc": "If port
is specified, it behaves the same as\nserver.listen([port[, host[, backlog]]][, callback])
.\nOtherwise, if path
is specified, it behaves the same as\nserver.listen(path[, backlog][, callback])
.\nIf none of them is specified, an error will be thrown.
If exclusive
is false
(default), then cluster workers will use the same\nunderlying handle, allowing connection handling duties to be shared. When\nexclusive
is true
, the handle is not shared, and attempted port sharing\nresults in an error. An example which listens on an exclusive port is\nshown below.
server.listen({\n host: 'localhost',\n port: 80,\n exclusive: true,\n});\n
\nWhen exclusive
is true
and the underlying handle is shared, it is\npossible that several workers query a handle with different backlogs.\nIn this case, the first backlog
passed to the master process will be used.
Starting an IPC server as root may cause the server path to be inaccessible for\nunprivileged users. Using readableAll
and writableAll
will make the server\naccessible for all users.
If the signal
option is enabled, calling .abort()
on the corresponding\nAbortController
is similar to calling .close()
on the server:
const controller = new AbortController();\nserver.listen({\n host: 'localhost',\n port: 80,\n signal: controller.signal,\n});\n// Later, when you want to close the server.\ncontroller.abort();\n
"
},
{
"textRaw": "`server.listen(path[, backlog][, callback])`",
"type": "method",
"name": "listen",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {net.Server}",
"name": "return",
"type": "net.Server"
},
"params": [
{
"textRaw": "`path` {string} Path the server should listen to. See [Identifying paths for IPC connections][].",
"name": "path",
"type": "string",
"desc": "Path the server should listen to. See [Identifying paths for IPC connections][]."
},
{
"textRaw": "`backlog` {number} Common parameter of [`server.listen()`][] functions.",
"name": "backlog",
"type": "number",
"desc": "Common parameter of [`server.listen()`][] functions."
},
{
"textRaw": "`callback` {Function}.",
"name": "callback",
"type": "Function",
"desc": "."
}
]
}
],
"desc": "Start an IPC server listening for connections on the given path
.
Start a TCP server listening for connections on the given port
and host
.
If port
is omitted or is 0, the operating system will assign an arbitrary\nunused port, which can be retrieved by using server.address().port
\nafter the 'listening'
event has been emitted.
If host
is omitted, the server will accept connections on the\nunspecified IPv6 address (::
) when IPv6 is available, or the\nunspecified IPv4 address (0.0.0.0
) otherwise.
In most operating systems, listening to the unspecified IPv6 address (::
)\nmay cause the net.Server
to also listen on the unspecified IPv4 address\n(0.0.0.0
).
Opposite of unref()
, calling ref()
on a previously unref
ed server will\nnot let the program exit if it's the only server left (the default behavior).\nIf the server is ref
ed calling ref()
again will have no effect.
Calling unref()
on a server will allow the program to exit if this is the only\nactive server in the event system. If the server is already unref
ed calling\nunref()
again will have no effect.
Set this property to reject connections when the server's connection count gets\nhigh.
\nIt is not recommended to use this option once a socket has been sent to a child\nwith child_process.fork()
.
net.Server
is an EventEmitter
with the following events:
This class is an abstraction of a TCP socket or a streaming IPC endpoint\n(uses named pipes on Windows, and Unix domain sockets otherwise). It is also\nan EventEmitter
.
A net.Socket
can be created by the user and used directly to interact with\na server. For example, it is returned by net.createConnection()
,\nso the user can use it to talk to the server.
It can also be created by Node.js and passed to the user when a connection\nis received. For example, it is passed to the listeners of a\n'connection'
event emitted on a net.Server
, so the user can use\nit to interact with the client.
Emitted once the socket is fully closed. The argument hadError
is a boolean\nwhich says if the socket was closed due to a transmission error.
Emitted when a socket connection is successfully established.\nSee net.createConnection()
.
Emitted when a new connection attempt is started. This may be emitted multiple times\nif the family autoselection algorithm is enabled in socket.connect(options)
.
Emitted when a connection attempt failed. This may be emitted multiple times\nif the family autoselection algorithm is enabled in socket.connect(options)
.
Emitted when a connection attempt timed out. This is only emitted (and may be\nemitted multiple times) if the family autoselection algorithm is enabled\nin socket.connect(options)
.
Emitted when data is received. The argument data
will be a Buffer
or\nString
. Encoding of data is set by socket.setEncoding()
.
The data will be lost if there is no listener when a Socket
\nemits a 'data'
event.
Emitted when the write buffer becomes empty. Can be used to throttle uploads.
\nSee also: the return values of socket.write()
.
Emitted when the other end of the socket signals the end of transmission, thus\nending the readable side of the socket.
\nBy default (allowHalfOpen
is false
) the socket will send an end of\ntransmission packet back and destroy its file descriptor once it has written out\nits pending write queue. However, if allowHalfOpen
is set to true
, the\nsocket will not automatically end()
its writable side,\nallowing the user to write arbitrary amounts of data. The user must call\nend()
explicitly to close the connection (i.e. sending a\nFIN packet back).
Emitted when an error occurs. The 'close'
event will be called directly\nfollowing this event.
Emitted after resolving the host name but before connecting.\nNot applicable to Unix sockets.
\nerr
<Error> | <null> The error object. See dns.lookup()
.address
<string> The IP address.family
<number> | <null> The address type. See dns.lookup()
.host
<string> The host name.Emitted when a socket is ready to be used.
\nTriggered immediately after 'connect'
.
Emitted if the socket times out from inactivity. This is only to notify that\nthe socket has been idle. The user must manually close the connection.
\nSee also: socket.setTimeout()
.
Returns the bound address
, the address family
name and port
of the\nsocket as reported by the operating system:\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
Initiate a connection on a given socket.
\nPossible signatures:
\nsocket.connect(options[, connectListener])
socket.connect(path[, connectListener])
\nfor IPC connections.socket.connect(port[, host][, connectListener])
\nfor TCP connections.This function is asynchronous. When the connection is established, the\n'connect'
event will be emitted. If there is a problem connecting,\ninstead of a 'connect'
event, an 'error'
event will be emitted with\nthe error passed to the 'error'
listener.\nThe last parameter connectListener
, if supplied, will be added as a listener\nfor the 'connect'
event once.
This function should only be used for reconnecting a socket after\n'close'
has been emitted or otherwise it may lead to undefined\nbehavior.
Initiate a connection on a given socket. Normally this method is not needed,\nthe socket should be created and opened with net.createConnection()
. Use\nthis only when implementing a custom Socket.
For TCP connections, available options
are:
port
<number> Required. Port the socket should connect to.host
<string> Host the socket should connect to. Default: 'localhost'
.localAddress
<string> Local address the socket should connect from.localPort
<number> Local port the socket should connect from.family
<number>: Version of IP stack. Must be 4
, 6
, or 0
. The value\n0
indicates that both IPv4 and IPv6 addresses are allowed. Default: 0
.hints
<number> Optional dns.lookup()
hints.lookup
<Function> Custom lookup function. Default: dns.lookup()
.noDelay
<boolean> If set to true
, it disables the use of Nagle's algorithm immediately\nafter the socket is established. Default: false
.keepAlive
<boolean> If set to true
, it enables keep-alive functionality on the socket\nimmediately after the connection is established, similarly on what is done in\nsocket.setKeepAlive([enable][, initialDelay])
.\nDefault: false
.keepAliveInitialDelay
<number> If set to a positive number, it sets the initial delay before\nthe first keepalive probe is sent on an idle socket.Default: 0
.autoSelectFamily
<boolean>: If set to true
, it enables a family autodetection algorithm\nthat loosely implements section 5 of RFC 8305.\nThe all
option passed to lookup is set to true
and the sockets attempts to connect to all\nobtained IPv6 and IPv4 addresses, in sequence, until a connection is established.\nThe first returned AAAA address is tried first, then the first returned A address,\nthen the second returned AAAA address and so on.\nEach connection attempt (but the last one) is given the amount of time specified by the autoSelectFamilyAttemptTimeout
option before timing out and trying the next address.\nIgnored if the family
option is not 0
or if localAddress
is set.\nConnection errors are not emitted if at least one connection succeeds.\nIf all connections attempts fails, a single AggregateError
with all failed attempts is emitted.\nDefault: net.getDefaultAutoSelectFamily()
autoSelectFamilyAttemptTimeout
<number>: The amount of time in milliseconds to wait\nfor a connection attempt to finish before trying the next address when using the autoSelectFamily
option.\nIf set to a positive integer less than 10
, then the value 10
will be used instead.\nDefault: net.getDefaultAutoSelectFamilyAttemptTimeout()
For IPC connections, available options
are:
path
<string> Required. Path the client should connect to.\nSee Identifying paths for IPC connections. If provided, the TCP-specific\noptions above are ignored.For both types, available options
include:
onread
<Object> If specified, incoming data is stored in a single buffer
\nand passed to the supplied callback
when data arrives on the socket.\nThis will cause the streaming functionality to not provide any data.\nThe socket will emit events like 'error'
, 'end'
, and 'close'
\nas usual. Methods like pause()
and resume()
will also behave as\nexpected.\nbuffer
<Buffer> | <Uint8Array> | <Function> Either a reusable chunk of memory to\nuse for storing incoming data or a function that returns such.callback
<Function> This function is called for every chunk of incoming\ndata. Two arguments are passed to it: the number of bytes written to\nbuffer
and a reference to buffer
. Return false
from this function to\nimplicitly pause()
the socket. This function will be executed in the\nglobal context.Following is an example of a client using the onread
option:
const net = require('node:net');\nnet.connect({\n port: 80,\n onread: {\n // Reuses a 4KiB Buffer for every read from the socket.\n buffer: Buffer.alloc(4 * 1024),\n callback: function(nread, buf) {\n // Received data is available in `buf` from 0 to `nread`.\n console.log(buf.toString('utf8', 0, nread));\n },\n },\n});\n
"
},
{
"textRaw": "`socket.connect(path[, connectListener])`",
"type": "method",
"name": "connect",
"signatures": [
{
"return": {
"textRaw": "Returns: {net.Socket} The socket itself.",
"name": "return",
"type": "net.Socket",
"desc": "The socket itself."
},
"params": [
{
"textRaw": "`path` {string} Path the client should connect to. See [Identifying paths for IPC connections][].",
"name": "path",
"type": "string",
"desc": "Path the client should connect to. See [Identifying paths for IPC connections][]."
},
{
"textRaw": "`connectListener` {Function} Common parameter of [`socket.connect()`][] methods. Will be added as a listener for the [`'connect'`][] event once.",
"name": "connectListener",
"type": "Function",
"desc": "Common parameter of [`socket.connect()`][] methods. Will be added as a listener for the [`'connect'`][] event once."
}
]
}
],
"desc": "Initiate an IPC connection on the given socket.
\nAlias to\nsocket.connect(options[, connectListener])
\ncalled with { path: path }
as options
.
Initiate a TCP connection on the given socket.
\nAlias to\nsocket.connect(options[, connectListener])
\ncalled with {port: port, host: host}
as options
.
Ensures that no more I/O activity happens on this socket.\nDestroys the stream and closes the connection.
\nSee writable.destroy()
for further details.
Destroys the socket after all data is written. If the 'finish'
event was\nalready emitted the socket is destroyed immediately. If the socket is still\nwritable it implicitly calls socket.end()
.
Half-closes the socket. i.e., it sends a FIN packet. It is possible the\nserver will still send some data.
\nSee writable.end()
for further details.
Pauses the reading of data. That is, 'data'
events will not be emitted.\nUseful to throttle back an upload.
Opposite of unref()
, calling ref()
on a previously unref
ed socket will\nnot let the program exit if it's the only socket left (the default behavior).\nIf the socket is ref
ed calling ref
again will have no effect.
Close the TCP connection by sending an RST packet and destroy the stream.\nIf this TCP socket is in connecting status, it will send an RST packet and destroy this TCP socket once it is connected.\nOtherwise, it will call socket.destroy
with an ERR_SOCKET_CLOSED
Error.\nIf this is not a TCP socket (for example, a pipe), calling this method will immediately throw an ERR_INVALID_HANDLE_TYPE
Error.
Resumes reading after a call to socket.pause()
.
Set the encoding for the socket as a Readable Stream. See\nreadable.setEncoding()
for more information.
Enable/disable keep-alive functionality, and optionally set the initial\ndelay before the first keepalive probe is sent on an idle socket.
\nSet initialDelay
(in milliseconds) to set the delay between the last\ndata packet received and the first keepalive probe. Setting 0
for\ninitialDelay
will leave the value unchanged from the default\n(or previous) setting.
Enabling the keep-alive functionality will set the following socket options:
\nSO_KEEPALIVE=1
TCP_KEEPIDLE=initialDelay
TCP_KEEPCNT=10
TCP_KEEPINTVL=1
Enable/disable the use of Nagle's algorithm.
\nWhen a TCP connection is created, it will have Nagle's algorithm enabled.
\nNagle's algorithm delays data before it is sent via the network. It attempts\nto optimize throughput at the expense of latency.
\nPassing true
for noDelay
or not passing an argument will disable Nagle's\nalgorithm for the socket. Passing false
for noDelay
will enable Nagle's\nalgorithm.
Sets the socket to timeout after timeout
milliseconds of inactivity on\nthe socket. By default net.Socket
do not have a timeout.
When an idle timeout is triggered the socket will receive a 'timeout'
\nevent but the connection will not be severed. The user must manually call\nsocket.end()
or socket.destroy()
to end the connection.
socket.setTimeout(3000);\nsocket.on('timeout', () => {\n console.log('socket timeout');\n socket.end();\n});\n
\nIf timeout
is 0, then the existing idle timeout is disabled.
The optional callback
parameter will be added as a one-time listener for the\n'timeout'
event.
Calling unref()
on a socket will allow the program to exit if this is the only\nactive socket in the event system. If the socket is already unref
ed calling\nunref()
again will have no effect.
Sends data on the socket. The second parameter specifies the encoding in the\ncase of a string. It defaults to UTF8 encoding.
\nReturns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in user memory.\n'drain'
will be emitted when the buffer is again free.
The optional callback
parameter will be executed when the data is finally\nwritten out, which may not be immediately.
See Writable
stream write()
method for more\ninformation.
This property is only present if the family autoselection algorithm is enabled in\nsocket.connect(options)
and it is an array of the addresses that have been attempted.
Each address is a string in the form of $IP:$PORT
. If the connection was successful,\nthen the last address is the one that the socket is currently connected to.
This property shows the number of characters buffered for writing. The buffer\nmay contain strings whose length after encoding is not yet known. So this number\nis only an approximation of the number of bytes in the buffer.
\nnet.Socket
has the property that socket.write()
always works. This is to\nhelp users get up and running quickly. The computer cannot always keep up\nwith the amount of data that is written to a socket. The network connection\nsimply might be too slow. Node.js will internally queue up the data written to a\nsocket and send it out over the wire when it is possible.
The consequence of this internal buffering is that memory may grow.\nUsers who experience large or growing bufferSize
should attempt to\n\"throttle\" the data flows in their program with\nsocket.pause()
and socket.resume()
.
The amount of received bytes.
" }, { "textRaw": "`bytesWritten` {integer}", "type": "integer", "name": "bytesWritten", "meta": { "added": [ "v0.5.3" ], "changes": [] }, "desc": "The amount of bytes sent.
" }, { "textRaw": "`connecting` {boolean}", "type": "boolean", "name": "connecting", "meta": { "added": [ "v6.1.0" ], "changes": [] }, "desc": "If true
,\nsocket.connect(options[, connectListener])
was\ncalled and has not yet finished. It will stay true
until the socket becomes\nconnected, then it is set to false
and the 'connect'
event is emitted. Note\nthat the\nsocket.connect(options[, connectListener])
\ncallback is a listener for the 'connect'
event.
See writable.destroyed
for further details.
The string representation of the local IP address the remote client is\nconnecting on. For example, in a server listening on '0.0.0.0'
, if a client\nconnects on '192.168.1.1'
, the value of socket.localAddress
would be\n'192.168.1.1'
.
The numeric representation of the local port. For example, 80
or 21
.
The string representation of the local IP family. 'IPv4'
or 'IPv6'
.
This is true
if the socket is not connected yet, either because .connect()
\nhas not yet been called or because it is still in the process of connecting\n(see socket.connecting
).
The string representation of the remote IP address. For example,\n'74.125.127.100'
or '2001:4860:a005::68'
. Value may be undefined
if\nthe socket is destroyed (for example, if the client disconnected).
The string representation of the remote IP family. 'IPv4'
or 'IPv6'
. Value may be undefined
if\nthe socket is destroyed (for example, if the client disconnected).
The numeric representation of the remote port. For example, 80
or 21
. Value may be undefined
if\nthe socket is destroyed (for example, if the client disconnected).
The socket timeout in milliseconds as set by socket.setTimeout()
.\nIt is undefined
if a timeout has not been set.
This property represents the state of the connection as a string.
\nsocket.readyState
is opening
.open
.readOnly
.writeOnly
.Creates a new socket object.
\nThe newly created socket can be either a TCP socket or a streaming IPC\nendpoint, depending on what it connect()
to.
Aliases to\nnet.createConnection()
.
Possible signatures:
\nnet.connect(options[, connectListener])
net.connect(path[, connectListener])
for IPC\nconnections.net.connect(port[, host][, connectListener])
\nfor TCP connections.Alias to\nnet.createConnection(options[, connectListener])
.
Alias to\nnet.createConnection(path[, connectListener])
.
Alias to\nnet.createConnection(port[, host][, connectListener])
.
A factory function, which creates a new net.Socket
,\nimmediately initiates connection with socket.connect()
,\nthen returns the net.Socket
that starts the connection.
When the connection is established, a 'connect'
event will be emitted\non the returned socket. The last parameter connectListener
, if supplied,\nwill be added as a listener for the 'connect'
event once.
Possible signatures:
\nnet.createConnection(options[, connectListener])
net.createConnection(path[, connectListener])
\nfor IPC connections.net.createConnection(port[, host][, connectListener])
\nfor TCP connections.The net.connect()
function is an alias to this function.
For available options, see\nnew net.Socket([options])
\nand socket.connect(options[, connectListener])
.
Additional options:
\ntimeout
<number> If set, will be used to call\nsocket.setTimeout(timeout)
after the socket is created, but before\nit starts the connection.Following is an example of a client of the echo server described\nin the net.createServer()
section:
const net = require('node:net');\nconst client = net.createConnection({ port: 8124 }, () => {\n // 'connect' listener.\n console.log('connected to server!');\n client.write('world!\\r\\n');\n});\nclient.on('data', (data) => {\n console.log(data.toString());\n client.end();\n});\nclient.on('end', () => {\n console.log('disconnected from server');\n});\n
\nTo connect on the socket /tmp/echo.sock
:
const client = net.createConnection({ path: '/tmp/echo.sock' });\n
"
},
{
"textRaw": "`net.createConnection(path[, connectListener])`",
"type": "method",
"name": "createConnection",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {net.Socket} The newly created socket used to start the connection.",
"name": "return",
"type": "net.Socket",
"desc": "The newly created socket used to start the connection."
},
"params": [
{
"textRaw": "`path` {string} Path the socket should connect to. Will be passed to [`socket.connect(path[, connectListener])`][`socket.connect(path)`]. See [Identifying paths for IPC connections][].",
"name": "path",
"type": "string",
"desc": "Path the socket should connect to. Will be passed to [`socket.connect(path[, connectListener])`][`socket.connect(path)`]. See [Identifying paths for IPC connections][]."
},
{
"textRaw": "`connectListener` {Function} Common parameter of the [`net.createConnection()`][] functions, an \"once\" listener for the `'connect'` event on the initiating socket. Will be passed to [`socket.connect(path[, connectListener])`][`socket.connect(path)`].",
"name": "connectListener",
"type": "Function",
"desc": "Common parameter of the [`net.createConnection()`][] functions, an \"once\" listener for the `'connect'` event on the initiating socket. Will be passed to [`socket.connect(path[, connectListener])`][`socket.connect(path)`]."
}
]
}
],
"desc": "Initiates an IPC connection.
\nThis function creates a new net.Socket
with all options set to default,\nimmediately initiates connection with\nsocket.connect(path[, connectListener])
,\nthen returns the net.Socket
that starts the connection.
Initiates a TCP connection.
\nThis function creates a new net.Socket
with all options set to default,\nimmediately initiates connection with\nsocket.connect(port[, host][, connectListener])
,\nthen returns the net.Socket
that starts the connection.
Creates a new TCP or IPC server.
\nIf allowHalfOpen
is set to true
, when the other end of the socket\nsignals the end of transmission, the server will only send back the end of\ntransmission when socket.end()
is explicitly called. For example, in the\ncontext of TCP, when a FIN packed is received, a FIN packed is sent\nback only when socket.end()
is explicitly called. Until then the\nconnection is half-closed (non-readable but still writable). See 'end'
\nevent and RFC 1122 (section 4.2.2.13) for more information.
If pauseOnConnect
is set to true
, then the socket associated with each\nincoming connection will be paused, and no data will be read from its handle.\nThis allows connections to be passed between processes without any data being\nread by the original process. To begin reading data from a paused socket, call\nsocket.resume()
.
The server can be a TCP server or an IPC server, depending on what it\nlisten()
to.
Here is an example of a TCP echo server which listens for connections\non port 8124:
\nconst net = require('node:net');\nconst server = net.createServer((c) => {\n // 'connection' listener.\n console.log('client connected');\n c.on('end', () => {\n console.log('client disconnected');\n });\n c.write('hello\\r\\n');\n c.pipe(c);\n});\nserver.on('error', (err) => {\n throw err;\n});\nserver.listen(8124, () => {\n console.log('server bound');\n});\n
\nTest this by using telnet
:
telnet localhost 8124\n
\nTo listen on the socket /tmp/echo.sock
:
server.listen('/tmp/echo.sock', () => {\n console.log('server bound');\n});\n
\nUse nc
to connect to a Unix domain socket server:
nc -U /tmp/echo.sock\n
"
},
{
"textRaw": "`net.getDefaultAutoSelectFamily()`",
"type": "method",
"name": "getDefaultAutoSelectFamily",
"meta": {
"added": [
"v19.4.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Gets the current default value of the autoSelectFamily
option of socket.connect(options)
.\nThe initial default value is true
, unless the command line option\n--no-network-family-autoselection
is provided.
autoSelectFamily
option.Sets the default value of the autoSelectFamily
option of socket.connect(options)
.
value
<boolean> The new default value. The initial default value is false
.Gets the current default value of the autoSelectFamilyAttemptTimeout
option of socket.connect(options)
.\nThe initial default value is 250
.
autoSelectFamilyAttemptTimeout
option.Sets the default value of the autoSelectFamilyAttemptTimeout
option of socket.connect(options)
.
value
<number> The new default value, which must be a positive number. If the number is less than 10
,\nthe value 10
is used instead. The initial default value is 250
.Returns 6
if input
is an IPv6 address. Returns 4
if input
is an IPv4\naddress in dot-decimal notation with no leading zeroes. Otherwise, returns\n0
.
net.isIP('::1'); // returns 6\nnet.isIP('127.0.0.1'); // returns 4\nnet.isIP('127.000.000.001'); // returns 0\nnet.isIP('127.0.0.1/24'); // returns 0\nnet.isIP('fhqwhgads'); // returns 0\n
"
},
{
"textRaw": "`net.isIPv4(input)`",
"type": "method",
"name": "isIPv4",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`input` {string}",
"name": "input",
"type": "string"
}
]
}
],
"desc": "Returns true
if input
is an IPv4 address in dot-decimal notation with no\nleading zeroes. Otherwise, returns false
.
net.isIPv4('127.0.0.1'); // returns true\nnet.isIPv4('127.000.000.001'); // returns false\nnet.isIPv4('127.0.0.1/24'); // returns false\nnet.isIPv4('fhqwhgads'); // returns false\n
"
},
{
"textRaw": "`net.isIPv6(input)`",
"type": "method",
"name": "isIPv6",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`input` {string}",
"name": "input",
"type": "string"
}
]
}
],
"desc": "Returns true
if input
is an IPv6 address. Otherwise, returns false
.
net.isIPv6('::1'); // returns true\nnet.isIPv6('fhqwhgads'); // returns false\n
"
}
],
"type": "module",
"displayName": "Net",
"source": "doc/api/net.md"
},
{
"textRaw": "OS",
"name": "os",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/os.js
\nThe node:os
module provides operating system-related utility methods and\nproperties. It can be accessed using:
const os = require('node:os');\n
",
"properties": [
{
"textRaw": "`EOL` {string}",
"type": "string",
"name": "EOL",
"meta": {
"added": [
"v0.7.8"
],
"changes": []
},
"desc": "The operating system-specific end-of-line marker.
\n\\n
on POSIX\\r\\n
on WindowsContains commonly used operating system-specific constants for error codes,\nprocess signals, and so on. The specific constants defined are described in\nOS constants.
" }, { "textRaw": "`devNull` {string}", "type": "string", "name": "devNull", "meta": { "added": [ "v16.3.0", "v14.18.0" ], "changes": [] }, "desc": "The platform-specific file path of the null device.
\n\\\\.\\nul
on Windows/dev/null
on POSIXReturns an estimate of the default amount of parallelism a program should use.\nAlways returns a value greater than zero.
\nThis function is a small wrapper about libuv's uv_available_parallelism()
.
Returns the operating system CPU architecture for which the Node.js binary was\ncompiled. Possible values are 'arm'
, 'arm64'
, 'ia32'
, 'loong64'
,\n'mips'
, 'mipsel'
, 'ppc'
, 'ppc64'
, 'riscv64'
, 's390'
, 's390x'
,\nand 'x64'
.
The return value is equivalent to process.arch
.
Returns an array of objects containing information about each logical CPU core.\nThe array will be empty if no CPU information is available, such as if the\n/proc
file system is unavailable.
The properties included on each object include:
\nmodel
<string>speed
<number> (in MHz)times
<Object>\nuser
<number> The number of milliseconds the CPU has spent in user mode.nice
<number> The number of milliseconds the CPU has spent in nice mode.sys
<number> The number of milliseconds the CPU has spent in sys mode.idle
<number> The number of milliseconds the CPU has spent in idle mode.irq
<number> The number of milliseconds the CPU has spent in irq mode.[\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 252020,\n nice: 0,\n sys: 30340,\n idle: 1070356870,\n irq: 0,\n },\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 306960,\n nice: 0,\n sys: 26980,\n idle: 1071569080,\n irq: 0,\n },\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 248450,\n nice: 0,\n sys: 21750,\n idle: 1070919370,\n irq: 0,\n },\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 256880,\n nice: 0,\n sys: 19430,\n idle: 1070905480,\n irq: 20,\n },\n },\n]\n
\nnice
values are POSIX-only. On Windows, the nice
values of all processors\nare always 0.
os.cpus().length
should not be used to calculate the amount of parallelism\navailable to an application. Use\nos.availableParallelism()
for this purpose.
Returns a string identifying the endianness of the CPU for which the Node.js\nbinary was compiled.
\nPossible values are 'BE'
for big endian and 'LE'
for little endian.
Returns the amount of free system memory in bytes as an integer.
" }, { "textRaw": "`os.getPriority([pid])`", "type": "method", "name": "getPriority", "meta": { "added": [ "v10.10.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer}", "name": "return", "type": "integer" }, "params": [ { "textRaw": "`pid` {integer} The process ID to retrieve scheduling priority for. **Default:** `0`.", "name": "pid", "type": "integer", "default": "`0`", "desc": "The process ID to retrieve scheduling priority for." } ] } ], "desc": "Returns the scheduling priority for the process specified by pid
. If pid
is\nnot provided or is 0
, the priority of the current process is returned.
Returns the string path of the current user's home directory.
\nOn POSIX, it uses the $HOME
environment variable if defined. Otherwise it\nuses the effective UID to look up the user's home directory.
On Windows, it uses the USERPROFILE
environment variable if defined.\nOtherwise it uses the path to the profile directory of the current user.
Returns the host name of the operating system as a string.
" }, { "textRaw": "`os.loadavg()`", "type": "method", "name": "loadavg", "meta": { "added": [ "v0.3.3" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {number\\[]}", "name": "return", "type": "number\\[]" }, "params": [] } ], "desc": "Returns an array containing the 1, 5, and 15 minute load averages.
\nThe load average is a measure of system activity calculated by the operating\nsystem and expressed as a fractional number.
\nThe load average is a Unix-specific concept. On Windows, the return value is\nalways [0, 0, 0]
.
Returns the machine type as a string, such as arm
, arm64
, aarch64
,\nmips
, mips64
, ppc64
, ppc64le
, s390
, s390x
, i386
, i686
, x86_64
.
On POSIX systems, the machine type is determined by calling\nuname(3)
. On Windows, RtlGetVersion()
is used, and if it is not\navailable, GetVersionExW()
will be used. See\nhttps://en.wikipedia.org/wiki/Uname#Examples for more information.
Returns an object containing network interfaces that have been assigned a\nnetwork address.
\nEach key on the returned object identifies a network interface. The associated\nvalue is an array of objects that each describe an assigned network address.
\nThe properties available on the assigned network address object include:
\naddress
<string> The assigned IPv4 or IPv6 addressnetmask
<string> The IPv4 or IPv6 network maskfamily
<string> Either IPv4
or IPv6
mac
<string> The MAC address of the network interfaceinternal
<boolean> true
if the network interface is a loopback or\nsimilar interface that is not remotely accessible; otherwise false
scopeid
<number> The numeric IPv6 scope ID (only specified when family
\nis IPv6
)cidr
<string> The assigned IPv4 or IPv6 address with the routing prefix\nin CIDR notation. If the netmask
is invalid, this property is set\nto null
.{\n lo: [\n {\n address: '127.0.0.1',\n netmask: '255.0.0.0',\n family: 'IPv4',\n mac: '00:00:00:00:00:00',\n internal: true,\n cidr: '127.0.0.1/8'\n },\n {\n address: '::1',\n netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',\n family: 'IPv6',\n mac: '00:00:00:00:00:00',\n scopeid: 0,\n internal: true,\n cidr: '::1/128'\n }\n ],\n eth0: [\n {\n address: '192.168.1.108',\n netmask: '255.255.255.0',\n family: 'IPv4',\n mac: '01:02:03:0a:0b:0c',\n internal: false,\n cidr: '192.168.1.108/24'\n },\n {\n address: 'fe80::a00:27ff:fe4e:66a1',\n netmask: 'ffff:ffff:ffff:ffff::',\n family: 'IPv6',\n mac: '01:02:03:0a:0b:0c',\n scopeid: 1,\n internal: false,\n cidr: 'fe80::a00:27ff:fe4e:66a1/64'\n }\n ]\n}\n
"
},
{
"textRaw": "`os.platform()`",
"type": "method",
"name": "platform",
"meta": {
"added": [
"v0.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": []
}
],
"desc": "Returns a string identifying the operating system platform for which\nthe Node.js binary was compiled. The value is set at compile time.\nPossible values are 'aix'
, 'darwin'
, 'freebsd'
,'linux'
,\n'openbsd'
, 'sunos'
, and 'win32'
.
The return value is equivalent to process.platform
.
The value 'android'
may also be returned if Node.js is built on the Android\noperating system. Android support is experimental.
Returns the operating system as a string.
\nOn POSIX systems, the operating system release is determined by calling\nuname(3)
. On Windows, GetVersionExW()
is used. See\nhttps://en.wikipedia.org/wiki/Uname#Examples for more information.
Attempts to set the scheduling priority for the process specified by pid
. If\npid
is not provided or is 0
, the process ID of the current process is used.
The priority
input must be an integer between -20
(high priority) and 19
\n(low priority). Due to differences between Unix priority levels and Windows\npriority classes, priority
is mapped to one of six priority constants in\nos.constants.priority
. When retrieving a process priority level, this range\nmapping may cause the return value to be slightly different on Windows. To avoid\nconfusion, set priority
to one of the priority constants.
On Windows, setting priority to PRIORITY_HIGHEST
requires elevated user\nprivileges. Otherwise the set priority will be silently reduced to\nPRIORITY_HIGH
.
Returns the operating system's default directory for temporary files as a\nstring.
" }, { "textRaw": "`os.totalmem()`", "type": "method", "name": "totalmem", "meta": { "added": [ "v0.3.3" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer}", "name": "return", "type": "integer" }, "params": [] } ], "desc": "Returns the total amount of system memory in bytes as an integer.
" }, { "textRaw": "`os.type()`", "type": "method", "name": "type", "meta": { "added": [ "v0.3.3" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {string}", "name": "return", "type": "string" }, "params": [] } ], "desc": "Returns the operating system name as returned by uname(3)
. For example, it\nreturns 'Linux'
on Linux, 'Darwin'
on macOS, and 'Windows_NT'
on Windows.
See https://en.wikipedia.org/wiki/Uname#Examples for additional information\nabout the output of running uname(3)
on various operating systems.
Returns the system uptime in number of seconds.
" }, { "textRaw": "`os.userInfo([options])`", "type": "method", "name": "userInfo", "meta": { "added": [ "v6.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`encoding` {string} Character encoding used to interpret resulting strings. If `encoding` is set to `'buffer'`, the `username`, `shell`, and `homedir` values will be `Buffer` instances. **Default:** `'utf8'`.", "name": "encoding", "type": "string", "default": "`'utf8'`", "desc": "Character encoding used to interpret resulting strings. If `encoding` is set to `'buffer'`, the `username`, `shell`, and `homedir` values will be `Buffer` instances." } ] } ] } ], "desc": "Returns information about the currently effective user. On POSIX platforms,\nthis is typically a subset of the password file. The returned object includes\nthe username
, uid
, gid
, shell
, and homedir
. On Windows, the uid
and\ngid
fields are -1
, and shell
is null
.
The value of homedir
returned by os.userInfo()
is provided by the operating\nsystem. This differs from the result of os.homedir()
, which queries\nenvironment variables for the home directory before falling back to the\noperating system response.
Throws a SystemError
if a user has no username
or homedir
.
Returns a string identifying the kernel version.
\nOn POSIX systems, the operating system release is determined by calling\nuname(3)
. On Windows, RtlGetVersion()
is used, and if it is not\navailable, GetVersionExW()
will be used. See\nhttps://en.wikipedia.org/wiki/Uname#Examples for more information.
The following constants are exported by os.constants
.
Not all constants will be available on every operating system.
", "modules": [ { "textRaw": "Signal constants", "name": "signal_constants", "meta": { "changes": [ { "version": "v5.11.0", "pr-url": "https://github.com/nodejs/node/pull/6093", "description": "Added support for `SIGINFO`." } ] }, "desc": "The following signal constants are exported by os.constants.signals
.
Constant | \nDescription | \n
---|---|
SIGHUP | \n Sent to indicate when a controlling terminal is closed or a parent\n process exits. | \n
SIGINT | \n Sent to indicate when a user wishes to interrupt a process\n (Ctrl+C). | \n
SIGQUIT | \n Sent to indicate when a user wishes to terminate a process and perform a\n core dump. | \n
SIGILL | \n Sent to a process to notify that it has attempted to perform an illegal,\n malformed, unknown, or privileged instruction. | \n
SIGTRAP | \n Sent to a process when an exception has occurred. | \n
SIGABRT | \n Sent to a process to request that it abort. | \n
SIGIOT | \n Synonym for SIGABRT | \n
SIGBUS | \n Sent to a process to notify that it has caused a bus error. | \n
SIGFPE | \n Sent to a process to notify that it has performed an illegal arithmetic\n operation. | \n
SIGKILL | \n Sent to a process to terminate it immediately. | \n
SIGUSR1 SIGUSR2 | \n Sent to a process to identify user-defined conditions. | \n
SIGSEGV | \n Sent to a process to notify of a segmentation fault. | \n
SIGPIPE | \n Sent to a process when it has attempted to write to a disconnected\n pipe. | \n
SIGALRM | \n Sent to a process when a system timer elapses. | \n
SIGTERM | \n Sent to a process to request termination. | \n
SIGCHLD | \n Sent to a process when a child process terminates. | \n
SIGSTKFLT | \n Sent to a process to indicate a stack fault on a coprocessor. | \n
SIGCONT | \n Sent to instruct the operating system to continue a paused process. | \n
SIGSTOP | \n Sent to instruct the operating system to halt a process. | \n
SIGTSTP | \n Sent to a process to request it to stop. | \n
SIGBREAK | \n Sent to indicate when a user wishes to interrupt a process. | \n
SIGTTIN | \n Sent to a process when it reads from the TTY while in the\n background. | \n
SIGTTOU | \n Sent to a process when it writes to the TTY while in the\n background. | \n
SIGURG | \n Sent to a process when a socket has urgent data to read. | \n
SIGXCPU | \n Sent to a process when it has exceeded its limit on CPU usage. | \n
SIGXFSZ | \n Sent to a process when it grows a file larger than the maximum\n allowed. | \n
SIGVTALRM | \n Sent to a process when a virtual timer has elapsed. | \n
SIGPROF | \n Sent to a process when a system timer has elapsed. | \n
SIGWINCH | \n Sent to a process when the controlling terminal has changed its\n size. | \n
SIGIO | \n Sent to a process when I/O is available. | \n
SIGPOLL | \n Synonym for SIGIO | \n
SIGLOST | \n Sent to a process when a file lock has been lost. | \n
SIGPWR | \n Sent to a process to notify of a power failure. | \n
SIGINFO | \n Synonym for SIGPWR | \n
SIGSYS | \n Sent to a process to notify of a bad argument. | \n
SIGUNUSED | \n Synonym for SIGSYS | \n
The following error constants are exported by os.constants.errno
.
Constant | \nDescription | \n
---|---|
E2BIG | \n Indicates that the list of arguments is longer than expected. | \n
EACCES | \n Indicates that the operation did not have sufficient permissions. | \n
EADDRINUSE | \n Indicates that the network address is already in use. | \n
EADDRNOTAVAIL | \n Indicates that the network address is currently unavailable for\n use. | \n
EAFNOSUPPORT | \n Indicates that the network address family is not supported. | \n
EAGAIN | \n Indicates that there is no data available and to try the\n operation again later. | \n
EALREADY | \n Indicates that the socket already has a pending connection in\n progress. | \n
EBADF | \n Indicates that a file descriptor is not valid. | \n
EBADMSG | \n Indicates an invalid data message. | \n
EBUSY | \n Indicates that a device or resource is busy. | \n
ECANCELED | \n Indicates that an operation was canceled. | \n
ECHILD | \n Indicates that there are no child processes. | \n
ECONNABORTED | \n Indicates that the network connection has been aborted. | \n
ECONNREFUSED | \n Indicates that the network connection has been refused. | \n
ECONNRESET | \n Indicates that the network connection has been reset. | \n
EDEADLK | \n Indicates that a resource deadlock has been avoided. | \n
EDESTADDRREQ | \n Indicates that a destination address is required. | \n
EDOM | \n Indicates that an argument is out of the domain of the function. | \n
EDQUOT | \n Indicates that the disk quota has been exceeded. | \n
EEXIST | \n Indicates that the file already exists. | \n
EFAULT | \n Indicates an invalid pointer address. | \n
EFBIG | \n Indicates that the file is too large. | \n
EHOSTUNREACH | \n Indicates that the host is unreachable. | \n
EIDRM | \n Indicates that the identifier has been removed. | \n
EILSEQ | \n Indicates an illegal byte sequence. | \n
EINPROGRESS | \n Indicates that an operation is already in progress. | \n
EINTR | \n Indicates that a function call was interrupted. | \n
EINVAL | \n Indicates that an invalid argument was provided. | \n
EIO | \n Indicates an otherwise unspecified I/O error. | \n
EISCONN | \n Indicates that the socket is connected. | \n
EISDIR | \n Indicates that the path is a directory. | \n
ELOOP | \n Indicates too many levels of symbolic links in a path. | \n
EMFILE | \n Indicates that there are too many open files. | \n
EMLINK | \n Indicates that there are too many hard links to a file. | \n
EMSGSIZE | \n Indicates that the provided message is too long. | \n
EMULTIHOP | \n Indicates that a multihop was attempted. | \n
ENAMETOOLONG | \n Indicates that the filename is too long. | \n
ENETDOWN | \n Indicates that the network is down. | \n
ENETRESET | \n Indicates that the connection has been aborted by the network. | \n
ENETUNREACH | \n Indicates that the network is unreachable. | \n
ENFILE | \n Indicates too many open files in the system. | \n
ENOBUFS | \n Indicates that no buffer space is available. | \n
ENODATA | \n Indicates that no message is available on the stream head read\n queue. | \n
ENODEV | \n Indicates that there is no such device. | \n
ENOENT | \n Indicates that there is no such file or directory. | \n
ENOEXEC | \n Indicates an exec format error. | \n
ENOLCK | \n Indicates that there are no locks available. | \n
ENOLINK | \n Indications that a link has been severed. | \n
ENOMEM | \n Indicates that there is not enough space. | \n
ENOMSG | \n Indicates that there is no message of the desired type. | \n
ENOPROTOOPT | \n Indicates that a given protocol is not available. | \n
ENOSPC | \n Indicates that there is no space available on the device. | \n
ENOSR | \n Indicates that there are no stream resources available. | \n
ENOSTR | \n Indicates that a given resource is not a stream. | \n
ENOSYS | \n Indicates that a function has not been implemented. | \n
ENOTCONN | \n Indicates that the socket is not connected. | \n
ENOTDIR | \n Indicates that the path is not a directory. | \n
ENOTEMPTY | \n Indicates that the directory is not empty. | \n
ENOTSOCK | \n Indicates that the given item is not a socket. | \n
ENOTSUP | \n Indicates that a given operation is not supported. | \n
ENOTTY | \n Indicates an inappropriate I/O control operation. | \n
ENXIO | \n Indicates no such device or address. | \n
EOPNOTSUPP | \n Indicates that an operation is not supported on the socket. Although\n ENOTSUP and EOPNOTSUPP have the same value\n on Linux, according to POSIX.1 these error values should be distinct.) | \n
EOVERFLOW | \n Indicates that a value is too large to be stored in a given data\n type. | \n
EPERM | \n Indicates that the operation is not permitted. | \n
EPIPE | \n Indicates a broken pipe. | \n
EPROTO | \n Indicates a protocol error. | \n
EPROTONOSUPPORT | \n Indicates that a protocol is not supported. | \n
EPROTOTYPE | \n Indicates the wrong type of protocol for a socket. | \n
ERANGE | \n Indicates that the results are too large. | \n
EROFS | \n Indicates that the file system is read only. | \n
ESPIPE | \n Indicates an invalid seek operation. | \n
ESRCH | \n Indicates that there is no such process. | \n
ESTALE | \n Indicates that the file handle is stale. | \n
ETIME | \n Indicates an expired timer. | \n
ETIMEDOUT | \n Indicates that the connection timed out. | \n
ETXTBSY | \n Indicates that a text file is busy. | \n
EWOULDBLOCK | \n Indicates that the operation would block. | \n
EXDEV | \n Indicates an improper link. | \n
The following error codes are specific to the Windows operating system.
\nConstant | \nDescription | \n
---|---|
WSAEINTR | \n Indicates an interrupted function call. | \n
WSAEBADF | \n Indicates an invalid file handle. | \n
WSAEACCES | \n Indicates insufficient permissions to complete the operation. | \n
WSAEFAULT | \n Indicates an invalid pointer address. | \n
WSAEINVAL | \n Indicates that an invalid argument was passed. | \n
WSAEMFILE | \n Indicates that there are too many open files. | \n
WSAEWOULDBLOCK | \n Indicates that a resource is temporarily unavailable. | \n
WSAEINPROGRESS | \n Indicates that an operation is currently in progress. | \n
WSAEALREADY | \n Indicates that an operation is already in progress. | \n
WSAENOTSOCK | \n Indicates that the resource is not a socket. | \n
WSAEDESTADDRREQ | \n Indicates that a destination address is required. | \n
WSAEMSGSIZE | \n Indicates that the message size is too long. | \n
WSAEPROTOTYPE | \n Indicates the wrong protocol type for the socket. | \n
WSAENOPROTOOPT | \n Indicates a bad protocol option. | \n
WSAEPROTONOSUPPORT | \n Indicates that the protocol is not supported. | \n
WSAESOCKTNOSUPPORT | \n Indicates that the socket type is not supported. | \n
WSAEOPNOTSUPP | \n Indicates that the operation is not supported. | \n
WSAEPFNOSUPPORT | \n Indicates that the protocol family is not supported. | \n
WSAEAFNOSUPPORT | \n Indicates that the address family is not supported. | \n
WSAEADDRINUSE | \n Indicates that the network address is already in use. | \n
WSAEADDRNOTAVAIL | \n Indicates that the network address is not available. | \n
WSAENETDOWN | \n Indicates that the network is down. | \n
WSAENETUNREACH | \n Indicates that the network is unreachable. | \n
WSAENETRESET | \n Indicates that the network connection has been reset. | \n
WSAECONNABORTED | \n Indicates that the connection has been aborted. | \n
WSAECONNRESET | \n Indicates that the connection has been reset by the peer. | \n
WSAENOBUFS | \n Indicates that there is no buffer space available. | \n
WSAEISCONN | \n Indicates that the socket is already connected. | \n
WSAENOTCONN | \n Indicates that the socket is not connected. | \n
WSAESHUTDOWN | \n Indicates that data cannot be sent after the socket has been\n shutdown. | \n
WSAETOOMANYREFS | \n Indicates that there are too many references. | \n
WSAETIMEDOUT | \n Indicates that the connection has timed out. | \n
WSAECONNREFUSED | \n Indicates that the connection has been refused. | \n
WSAELOOP | \n Indicates that a name cannot be translated. | \n
WSAENAMETOOLONG | \n Indicates that a name was too long. | \n
WSAEHOSTDOWN | \n Indicates that a network host is down. | \n
WSAEHOSTUNREACH | \n Indicates that there is no route to a network host. | \n
WSAENOTEMPTY | \n Indicates that the directory is not empty. | \n
WSAEPROCLIM | \n Indicates that there are too many processes. | \n
WSAEUSERS | \n Indicates that the user quota has been exceeded. | \n
WSAEDQUOT | \n Indicates that the disk quota has been exceeded. | \n
WSAESTALE | \n Indicates a stale file handle reference. | \n
WSAEREMOTE | \n Indicates that the item is remote. | \n
WSASYSNOTREADY | \n Indicates that the network subsystem is not ready. | \n
WSAVERNOTSUPPORTED | \n Indicates that the winsock.dll version is out of\n range. | \n
WSANOTINITIALISED | \n Indicates that successful WSAStartup has not yet been performed. | \n
WSAEDISCON | \n Indicates that a graceful shutdown is in progress. | \n
WSAENOMORE | \n Indicates that there are no more results. | \n
WSAECANCELLED | \n Indicates that an operation has been canceled. | \n
WSAEINVALIDPROCTABLE | \n Indicates that the procedure call table is invalid. | \n
WSAEINVALIDPROVIDER | \n Indicates an invalid service provider. | \n
WSAEPROVIDERFAILEDINIT | \n Indicates that the service provider failed to initialized. | \n
WSASYSCALLFAILURE | \n Indicates a system call failure. | \n
WSASERVICE_NOT_FOUND | \n Indicates that a service was not found. | \n
WSATYPE_NOT_FOUND | \n Indicates that a class type was not found. | \n
WSA_E_NO_MORE | \n Indicates that there are no more results. | \n
WSA_E_CANCELLED | \n Indicates that the call was canceled. | \n
WSAEREFUSED | \n Indicates that a database query was refused. | \n
If available on the operating system, the following constants\nare exported in os.constants.dlopen
. See dlopen(3)
for detailed\ninformation.
Constant | \nDescription | \n
---|---|
RTLD_LAZY | \n Perform lazy binding. Node.js sets this flag by default. | \n
RTLD_NOW | \n Resolve all undefined symbols in the library before dlopen(3)\n returns. | \n
RTLD_GLOBAL | \n Symbols defined by the library will be made available for symbol\n resolution of subsequently loaded libraries. | \n
RTLD_LOCAL | \n The converse of RTLD_GLOBAL . This is the default behavior\n if neither flag is specified. | \n
RTLD_DEEPBIND | \n Make a self-contained library use its own symbols in preference to\n symbols from previously loaded libraries. | \n
The following process scheduling constants are exported by\nos.constants.priority
.
Constant | \nDescription | \n
---|---|
PRIORITY_LOW | \n The lowest process scheduling priority. This corresponds to\n IDLE_PRIORITY_CLASS on Windows, and a nice value of\n 19 on all other platforms. | \n
PRIORITY_BELOW_NORMAL | \n The process scheduling priority above PRIORITY_LOW and\n below PRIORITY_NORMAL . This corresponds to\n BELOW_NORMAL_PRIORITY_CLASS on Windows, and a nice value of\n 10 on all other platforms. | \n
PRIORITY_NORMAL | \n The default process scheduling priority. This corresponds to\n NORMAL_PRIORITY_CLASS on Windows, and a nice value of\n 0 on all other platforms. | \n
PRIORITY_ABOVE_NORMAL | \n The process scheduling priority above PRIORITY_NORMAL and\n below PRIORITY_HIGH . This corresponds to\n ABOVE_NORMAL_PRIORITY_CLASS on Windows, and a nice value of\n -7 on all other platforms. | \n
PRIORITY_HIGH | \n The process scheduling priority above PRIORITY_ABOVE_NORMAL \n and below PRIORITY_HIGHEST . This corresponds to\n HIGH_PRIORITY_CLASS on Windows, and a nice value of\n -14 on all other platforms. | \n
PRIORITY_HIGHEST | \n The highest process scheduling priority. This corresponds to\n REALTIME_PRIORITY_CLASS on Windows, and a nice value of\n -20 on all other platforms. | \n
Constant | \nDescription | \n
---|---|
UV_UDP_REUSEADDR | \n \n |
Source Code: lib/path.js
\nThe node:path
module provides utilities for working with file and directory\npaths. It can be accessed using:
const path = require('node:path');\n
",
"modules": [
{
"textRaw": "Windows vs. POSIX",
"name": "windows_vs._posix",
"desc": "The default operation of the node:path
module varies based on the operating\nsystem on which a Node.js application is running. Specifically, when running on\na Windows operating system, the node:path
module will assume that\nWindows-style paths are being used.
So using path.basename()
might yield different results on POSIX and Windows:
On POSIX:
\npath.basename('C:\\\\temp\\\\myfile.html');\n// Returns: 'C:\\\\temp\\\\myfile.html'\n
\nOn Windows:
\npath.basename('C:\\\\temp\\\\myfile.html');\n// Returns: 'myfile.html'\n
\nTo achieve consistent results when working with Windows file paths on any\noperating system, use path.win32
:
On POSIX and Windows:
\npath.win32.basename('C:\\\\temp\\\\myfile.html');\n// Returns: 'myfile.html'\n
\nTo achieve consistent results when working with POSIX file paths on any\noperating system, use path.posix
:
On POSIX and Windows:
\npath.posix.basename('/tmp/myfile.html');\n// Returns: 'myfile.html'\n
\nOn Windows Node.js follows the concept of per-drive working directory.\nThis behavior can be observed when using a drive path without a backslash. For\nexample, path.resolve('C:\\\\')
can potentially return a different result than\npath.resolve('C:')
. For more information, see\nthis MSDN page.
The path.basename()
method returns the last portion of a path
, similar to\nthe Unix basename
command. Trailing directory separators are\nignored.
path.basename('/foo/bar/baz/asdf/quux.html');\n// Returns: 'quux.html'\n\npath.basename('/foo/bar/baz/asdf/quux.html', '.html');\n// Returns: 'quux'\n
\nAlthough Windows usually treats file names, including file extensions, in a\ncase-insensitive manner, this function does not. For example, C:\\\\foo.html
and\nC:\\\\foo.HTML
refer to the same file, but basename
treats the extension as a\ncase-sensitive string:
path.win32.basename('C:\\\\foo.html', '.html');\n// Returns: 'foo'\n\npath.win32.basename('C:\\\\foo.HTML', '.html');\n// Returns: 'foo.HTML'\n
\nA TypeError
is thrown if path
is not a string or if suffix
is given\nand is not a string.
The path.dirname()
method returns the directory name of a path
, similar to\nthe Unix dirname
command. Trailing directory separators are ignored, see\npath.sep
.
path.dirname('/foo/bar/baz/asdf/quux');\n// Returns: '/foo/bar/baz/asdf'\n
\nA TypeError
is thrown if path
is not a string.
The path.extname()
method returns the extension of the path
, from the last\noccurrence of the .
(period) character to end of string in the last portion of\nthe path
. If there is no .
in the last portion of the path
, or if\nthere are no .
characters other than the first character of\nthe basename of path
(see path.basename()
) , an empty string is returned.
path.extname('index.html');\n// Returns: '.html'\n\npath.extname('index.coffee.md');\n// Returns: '.md'\n\npath.extname('index.');\n// Returns: '.'\n\npath.extname('index');\n// Returns: ''\n\npath.extname('.index');\n// Returns: ''\n\npath.extname('.index.md');\n// Returns: '.md'\n
\nA TypeError
is thrown if path
is not a string.
The path.format()
method returns a path string from an object. This is the\nopposite of path.parse()
.
When providing properties to the pathObject
remember that there are\ncombinations where one property has priority over another:
pathObject.root
is ignored if pathObject.dir
is providedpathObject.ext
and pathObject.name
are ignored if pathObject.base
existsFor example, on POSIX:
\n// If `dir`, `root` and `base` are provided,\n// `${dir}${path.sep}${base}`\n// will be returned. `root` is ignored.\npath.format({\n root: '/ignored',\n dir: '/home/user/dir',\n base: 'file.txt',\n});\n// Returns: '/home/user/dir/file.txt'\n\n// `root` will be used if `dir` is not specified.\n// If only `root` is provided or `dir` is equal to `root` then the\n// platform separator will not be included. `ext` will be ignored.\npath.format({\n root: '/',\n base: 'file.txt',\n ext: 'ignored',\n});\n// Returns: '/file.txt'\n\n// `name` + `ext` will be used if `base` is not specified.\npath.format({\n root: '/',\n name: 'file',\n ext: '.txt',\n});\n// Returns: '/file.txt'\n\n// The dot will be added if it is not specified in `ext`.\npath.format({\n root: '/',\n name: 'file',\n ext: 'txt',\n});\n// Returns: '/file.txt'\n
\nOn Windows:
\npath.format({\n dir: 'C:\\\\path\\\\dir',\n base: 'file.txt',\n});\n// Returns: 'C:\\\\path\\\\dir\\\\file.txt'\n
"
},
{
"textRaw": "`path.isAbsolute(path)`",
"type": "method",
"name": "isAbsolute",
"meta": {
"added": [
"v0.11.2"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`path` {string}",
"name": "path",
"type": "string"
}
]
}
],
"desc": "The path.isAbsolute()
method determines if path
is an absolute path.
If the given path
is a zero-length string, false
will be returned.
For example, on POSIX:
\npath.isAbsolute('/foo/bar'); // true\npath.isAbsolute('/baz/..'); // true\npath.isAbsolute('qux/'); // false\npath.isAbsolute('.'); // false\n
\nOn Windows:
\npath.isAbsolute('//server'); // true\npath.isAbsolute('\\\\\\\\server'); // true\npath.isAbsolute('C:/foo/..'); // true\npath.isAbsolute('C:\\\\foo\\\\..'); // true\npath.isAbsolute('bar\\\\baz'); // false\npath.isAbsolute('bar/baz'); // false\npath.isAbsolute('.'); // false\n
\nA TypeError
is thrown if path
is not a string.
The path.join()
method joins all given path
segments together using the\nplatform-specific separator as a delimiter, then normalizes the resulting path.
Zero-length path
segments are ignored. If the joined path string is a\nzero-length string then '.'
will be returned, representing the current\nworking directory.
path.join('/foo', 'bar', 'baz/asdf', 'quux', '..');\n// Returns: '/foo/bar/baz/asdf'\n\npath.join('foo', {}, 'bar');\n// Throws 'TypeError: Path must be a string. Received {}'\n
\nA TypeError
is thrown if any of the path segments is not a string.
The path.normalize()
method normalizes the given path
, resolving '..'
and\n'.'
segments.
When multiple, sequential path segment separation characters are found (e.g.\n/
on POSIX and either \\
or /
on Windows), they are replaced by a single\ninstance of the platform-specific path segment separator (/
on POSIX and\n\\
on Windows). Trailing separators are preserved.
If the path
is a zero-length string, '.'
is returned, representing the\ncurrent working directory.
On POSIX, the types of normalization applied by this function do not strictly\nadhere to the POSIX specification. For example, this function will replace two\nleading forward slashes with a single slash as if it was a regular absolute\npath, whereas a few POSIX systems assign special meaning to paths beginning with\nexactly two forward slashes. Similarly, other substitutions performed by this\nfunction, such as removing ..
segments, may change how the underlying system\nresolves the path.
For example, on POSIX:
\npath.normalize('/foo/bar//baz/asdf/quux/..');\n// Returns: '/foo/bar/baz/asdf'\n
\nOn Windows:
\npath.normalize('C:\\\\temp\\\\\\\\foo\\\\bar\\\\..\\\\');\n// Returns: 'C:\\\\temp\\\\foo\\\\'\n
\nSince Windows recognizes multiple path separators, both separators will be\nreplaced by instances of the Windows preferred separator (\\
):
path.win32.normalize('C:////temp\\\\\\\\/\\\\/\\\\/foo/bar');\n// Returns: 'C:\\\\temp\\\\foo\\\\bar'\n
\nA TypeError
is thrown if path
is not a string.
The path.parse()
method returns an object whose properties represent\nsignificant elements of the path
. Trailing directory separators are ignored,\nsee path.sep
.
The returned object will have the following properties:
\n\nFor example, on POSIX:
\npath.parse('/home/user/dir/file.txt');\n// Returns:\n// { root: '/',\n// dir: '/home/user/dir',\n// base: 'file.txt',\n// ext: '.txt',\n// name: 'file' }\n
\n┌─────────────────────┬────────────┐\n│ dir │ base │\n├──────┬ ├──────┬─────┤\n│ root │ │ name │ ext │\n\" / home/user/dir / file .txt \"\n└──────┴──────────────┴──────┴─────┘\n(All spaces in the \"\" line should be ignored. They are purely for formatting.)\n
\nOn Windows:
\npath.parse('C:\\\\path\\\\dir\\\\file.txt');\n// Returns:\n// { root: 'C:\\\\',\n// dir: 'C:\\\\path\\\\dir',\n// base: 'file.txt',\n// ext: '.txt',\n// name: 'file' }\n
\n┌─────────────────────┬────────────┐\n│ dir │ base │\n├──────┬ ├──────┬─────┤\n│ root │ │ name │ ext │\n\" C:\\ path\\dir \\ file .txt \"\n└──────┴──────────────┴──────┴─────┘\n(All spaces in the \"\" line should be ignored. They are purely for formatting.)\n
\nA TypeError
is thrown if path
is not a string.
The path.relative()
method returns the relative path from from
to to
based\non the current working directory. If from
and to
each resolve to the same\npath (after calling path.resolve()
on each), a zero-length string is returned.
If a zero-length string is passed as from
or to
, the current working\ndirectory will be used instead of the zero-length strings.
For example, on POSIX:
\npath.relative('/data/orandea/test/aaa', '/data/orandea/impl/bbb');\n// Returns: '../../impl/bbb'\n
\nOn Windows:
\npath.relative('C:\\\\orandea\\\\test\\\\aaa', 'C:\\\\orandea\\\\impl\\\\bbb');\n// Returns: '..\\\\..\\\\impl\\\\bbb'\n
\nA TypeError
is thrown if either from
or to
is not a string.
The path.resolve()
method resolves a sequence of paths or path segments into\nan absolute path.
The given sequence of paths is processed from right to left, with each\nsubsequent path
prepended until an absolute path is constructed.\nFor instance, given the sequence of path segments: /foo
, /bar
, baz
,\ncalling path.resolve('/foo', '/bar', 'baz')
would return /bar/baz
\nbecause 'baz'
is not an absolute path but '/bar' + '/' + 'baz'
is.
If, after processing all given path
segments, an absolute path has not yet\nbeen generated, the current working directory is used.
The resulting path is normalized and trailing slashes are removed unless the\npath is resolved to the root directory.
\nZero-length path
segments are ignored.
If no path
segments are passed, path.resolve()
will return the absolute path\nof the current working directory.
path.resolve('/foo/bar', './baz');\n// Returns: '/foo/bar/baz'\n\npath.resolve('/foo/bar', '/tmp/file/');\n// Returns: '/tmp/file'\n\npath.resolve('wwwroot', 'static_files/png/', '../gif/image.gif');\n// If the current working directory is /home/myself/node,\n// this returns '/home/myself/node/wwwroot/static_files/gif/image.gif'\n
\nA TypeError
is thrown if any of the arguments is not a string.
On Windows systems only, returns an equivalent namespace-prefixed path for\nthe given path
. If path
is not a string, path
will be returned without\nmodifications.
This method is meaningful only on Windows systems. On POSIX systems, the\nmethod is non-operational and always returns path
without modifications.
Provides the platform-specific path delimiter:
\n;
for Windows:
for POSIXFor example, on POSIX:
\nconsole.log(process.env.PATH);\n// Prints: '/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin'\n\nprocess.env.PATH.split(path.delimiter);\n// Returns: ['/usr/bin', '/bin', '/usr/sbin', '/sbin', '/usr/local/bin']\n
\nOn Windows:
\nconsole.log(process.env.PATH);\n// Prints: 'C:\\Windows\\system32;C:\\Windows;C:\\Program Files\\node\\'\n\nprocess.env.PATH.split(path.delimiter);\n// Returns ['C:\\\\Windows\\\\system32', 'C:\\\\Windows', 'C:\\\\Program Files\\\\node\\\\']\n
"
},
{
"textRaw": "`posix` {Object}",
"type": "Object",
"name": "posix",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v15.3.0",
"pr-url": "https://github.com/nodejs/node/pull/34962",
"description": "Exposed as `require('path/posix')`."
}
]
},
"desc": "The path.posix
property provides access to POSIX specific implementations\nof the path
methods.
The API is accessible via require('node:path').posix
or require('node:path/posix')
.
Provides the platform-specific path segment separator:
\n\\
on Windows/
on POSIXFor example, on POSIX:
\n'foo/bar/baz'.split(path.sep);\n// Returns: ['foo', 'bar', 'baz']\n
\nOn Windows:
\n'foo\\\\bar\\\\baz'.split(path.sep);\n// Returns: ['foo', 'bar', 'baz']\n
\nOn Windows, both the forward slash (/
) and backward slash (\\
) are accepted\nas path segment separators; however, the path
methods only add backward\nslashes (\\
).
The path.win32
property provides access to Windows-specific implementations\nof the path
methods.
The API is accessible via require('node:path').win32
or require('node:path/win32')
.
Source Code: lib/perf_hooks.js
\nThis module provides an implementation of a subset of the W3C\nWeb Performance APIs as well as additional APIs for\nNode.js-specific performance measurements.
\nNode.js supports the following Web Performance APIs:
\n\nconst { PerformanceObserver, performance } = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((items) => {\n console.log(items.getEntries()[0].duration);\n performance.clearMarks();\n});\nobs.observe({ type: 'measure' });\nperformance.measure('Start to Now');\n\nperformance.mark('A');\ndoSomeLongRunningProcess(() => {\n performance.measure('A to Now', 'A');\n\n performance.mark('B');\n performance.measure('A to B', 'A', 'B');\n});\n
",
"properties": [
{
"textRaw": "`perf_hooks.performance`",
"name": "performance",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"desc": "An object that can be used to collect performance metrics from the current\nNode.js instance. It is similar to window.performance
in browsers.
If name
is not provided, removes all PerformanceMark
objects from the\nPerformance Timeline. If name
is provided, removes only the named mark.
If name
is not provided, removes all PerformanceMeasure
objects from the\nPerformance Timeline. If name
is provided, removes only the named measure.
If name
is not provided, removes all PerformanceResourceTiming
objects from\nthe Resource Timeline. If name
is provided, removes only the named resource.
The eventLoopUtilization()
method returns an object that contains the\ncumulative duration of time the event loop has been both idle and active as a\nhigh resolution milliseconds timer. The utilization
value is the calculated\nEvent Loop Utilization (ELU).
If bootstrapping has not yet finished on the main thread the properties have\nthe value of 0
. The ELU is immediately available on Worker threads since\nbootstrap happens within the event loop.
Both utilization1
and utilization2
are optional parameters.
If utilization1
is passed, then the delta between the current call's active
\nand idle
times, as well as the corresponding utilization
value are\ncalculated and returned (similar to process.hrtime()
).
If utilization1
and utilization2
are both passed, then the delta is\ncalculated between the two arguments. This is a convenience option because,\nunlike process.hrtime()
, calculating the ELU is more complex than a\nsingle subtraction.
ELU is similar to CPU utilization, except that it only measures event loop\nstatistics and not CPU usage. It represents the percentage of time the event\nloop has spent outside the event loop's event provider (e.g. epoll_wait
).\nNo other CPU idle time is taken into consideration. The following is an example\nof how a mostly idle process will have a high ELU.
'use strict';\nconst { eventLoopUtilization } = require('node:perf_hooks').performance;\nconst { spawnSync } = require('node:child_process');\n\nsetImmediate(() => {\n const elu = eventLoopUtilization();\n spawnSync('sleep', ['5']);\n console.log(eventLoopUtilization(elu).utilization);\n});\n
\nAlthough the CPU is mostly idle while running this script, the value of\nutilization
is 1
. This is because the call to\nchild_process.spawnSync()
blocks the event loop from proceeding.
Passing in a user-defined object instead of the result of a previous call to\neventLoopUtilization()
will lead to undefined behavior. The return values\nare not guaranteed to reflect any correct state of the event loop.
Returns a list of PerformanceEntry
objects in chronological order with\nrespect to performanceEntry.startTime
. If you are only interested in\nperformance entries of certain types or that have certain names, see\nperformance.getEntriesByType()
and performance.getEntriesByName()
.
Returns a list of PerformanceEntry
objects in chronological order\nwith respect to performanceEntry.startTime
whose performanceEntry.name
is\nequal to name
, and optionally, whose performanceEntry.entryType
is equal to\ntype
.
Returns a list of PerformanceEntry
objects in chronological order\nwith respect to performanceEntry.startTime
whose performanceEntry.entryType
\nis equal to type
.
Creates a new PerformanceMark
entry in the Performance Timeline. A\nPerformanceMark
is a subclass of PerformanceEntry
whose\nperformanceEntry.entryType
is always 'mark'
, and whose\nperformanceEntry.duration
is always 0
. Performance marks are used\nto mark specific significant moments in the Performance Timeline.
The created PerformanceMark
entry is put in the global Performance Timeline\nand can be queried with performance.getEntries
,\nperformance.getEntriesByName
, and performance.getEntriesByType
. When the\nobservation is performed, the entries should be cleared from the global\nPerformance Timeline manually with performance.clearMarks
.
This property is an extension by Node.js. It is not available in Web browsers.
\nCreates a new PerformanceResourceTiming
entry in the Resource Timeline. A\nPerformanceResourceTiming
is a subclass of PerformanceEntry
whose\nperformanceEntry.entryType
is always 'resource'
. Performance resources\nare used to mark moments in the Resource Timeline.
The created PerformanceMark
entry is put in the global Resource Timeline\nand can be queried with performance.getEntries
,\nperformance.getEntriesByName
, and performance.getEntriesByType
. When the\nobservation is performed, the entries should be cleared from the global\nPerformance Timeline manually with performance.clearResourceTimings
.
Creates a new PerformanceMeasure
entry in the Performance Timeline. A\nPerformanceMeasure
is a subclass of PerformanceEntry
whose\nperformanceEntry.entryType
is always 'measure'
, and whose\nperformanceEntry.duration
measures the number of milliseconds elapsed since\nstartMark
and endMark
.
The startMark
argument may identify any existing PerformanceMark
in the\nPerformance Timeline, or may identify any of the timestamp properties\nprovided by the PerformanceNodeTiming
class. If the named startMark
does\nnot exist, an error is thrown.
The optional endMark
argument must identify any existing PerformanceMark
\nin the Performance Timeline or any of the timestamp properties provided by the\nPerformanceNodeTiming
class. endMark
will be performance.now()
\nif no parameter is passed, otherwise if the named endMark
does not exist, an\nerror will be thrown.
The created PerformanceMeasure
entry is put in the global Performance Timeline\nand can be queried with performance.getEntries
,\nperformance.getEntriesByName
, and performance.getEntriesByType
. When the\nobservation is performed, the entries should be cleared from the global\nPerformance Timeline manually with performance.clearMeasures
.
Returns the current high resolution millisecond timestamp, where 0 represents\nthe start of the current node
process.
Sets the global performance resource timing buffer size to the specified number\nof \"resource\" type performance entry objects.
\nBy default the max buffer size is set to 250.
" }, { "textRaw": "`performance.timerify(fn[, options])`", "type": "method", "name": "timerify", "meta": { "added": [ "v8.5.0" ], "changes": [ { "version": "v16.0.0", "pr-url": "https://github.com/nodejs/node/pull/37475", "description": "Added the histogram option." }, { "version": "v16.0.0", "pr-url": "https://github.com/nodejs/node/pull/37136", "description": "Re-implemented to use pure-JavaScript and the ability to time async functions." } ] }, "signatures": [ { "params": [ { "textRaw": "`fn` {Function}", "name": "fn", "type": "Function" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`histogram` {RecordableHistogram} A histogram object created using `perf_hooks.createHistogram()` that will record runtime durations in nanoseconds.", "name": "histogram", "type": "RecordableHistogram", "desc": "A histogram object created using `perf_hooks.createHistogram()` that will record runtime durations in nanoseconds." } ] } ] } ], "desc": "This property is an extension by Node.js. It is not available in Web browsers.
\nWraps a function within a new function that measures the running time of the\nwrapped function. A PerformanceObserver
must be subscribed to the 'function'
\nevent type in order for the timing details to be accessed.
const {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nfunction someFunction() {\n console.log('hello world');\n}\n\nconst wrapped = performance.timerify(someFunction);\n\nconst obs = new PerformanceObserver((list) => {\n console.log(list.getEntries()[0].duration);\n\n performance.clearMarks();\n performance.clearMeasures();\n obs.disconnect();\n});\nobs.observe({ entryTypes: ['function'] });\n\n// A performance timeline entry will be created\nwrapped();\n
\nIf the wrapped function returns a promise, a finally handler will be attached\nto the promise and the duration will be reported once the finally handler is\ninvoked.
" }, { "textRaw": "`performance.toJSON()`", "type": "method", "name": "toJSON", "meta": { "added": [ "v16.1.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This method must be called with the `performance` object as the receiver." } ] }, "signatures": [ { "params": [] } ], "desc": "An object which is JSON representation of the performance
object. It\nis similar to window.performance.toJSON
in browsers.
The 'resourcetimingbufferfull'
event is fired when the global performance\nresource timing buffer is full. Adjust resource timing buffer size with\nperformance.setResourceTimingBufferSize()
or clear the buffer with\nperformance.clearResourceTimings()
in the event listener to allow\nmore entries to be added to the performance timeline buffer.
This property is an extension by Node.js. It is not available in Web browsers.
\nAn instance of the PerformanceNodeTiming
class that provides performance\nmetrics for specific Node.js operational milestones.
The timeOrigin
specifies the high resolution millisecond timestamp at\nwhich the current node
process began, measured in Unix time.
The constructor of this class is not exposed to users directly.
", "properties": [ { "textRaw": "`duration` {number}", "type": "number", "name": "duration", "meta": { "added": [ "v8.5.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceEntry` object as the receiver." } ] }, "desc": "The total number of milliseconds elapsed for this entry. This value will not\nbe meaningful for all Performance Entry types.
" }, { "textRaw": "`entryType` {string}", "type": "string", "name": "entryType", "meta": { "added": [ "v8.5.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceEntry` object as the receiver." } ] }, "desc": "The type of the performance entry. It may be one of:
\n'node'
(Node.js only)'mark'
(available on the Web)'measure'
(available on the Web)'gc'
(Node.js only)'function'
(Node.js only)'http2'
(Node.js only)'http'
(Node.js only)The name of the performance entry.
" }, { "textRaw": "`startTime` {number}", "type": "number", "name": "startTime", "meta": { "added": [ "v8.5.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceEntry` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp marking the starting time of the\nPerformance Entry.
" } ] }, { "textRaw": "Class: `PerformanceMark`", "type": "class", "name": "PerformanceMark", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [] }, "desc": "Exposes marks created via the Performance.mark()
method.
Additional detail specified when creating with Performance.mark()
method.
Exposes measures created via the Performance.measure()
method.
The constructor of this class is not exposed to users directly.
", "properties": [ { "textRaw": "`detail` {any}", "type": "any", "name": "detail", "meta": { "added": [ "v16.0.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceMeasure` object as the receiver." } ] }, "desc": "Additional detail specified when creating with Performance.measure()
method.
This class is an extension by Node.js. It is not available in Web browsers.
\nProvides detailed Node.js timing data.
\nThe constructor of this class is not exposed to users directly.
", "properties": [ { "textRaw": "`detail` {any}", "type": "any", "name": "detail", "meta": { "added": [ "v16.0.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceNodeEntry` object as the receiver." } ] }, "desc": "Additional detail specific to the entryType
.
When performanceEntry.entryType
is equal to 'gc'
, the performance.flags
\nproperty contains additional information about garbage collection operation.\nThe value may be one of:
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_NO
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_FORCED
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE
When performanceEntry.entryType
is equal to 'gc'
, the performance.kind
\nproperty identifies the type of garbage collection operation that occurred.\nThe value may be one of:
perf_hooks.constants.NODE_PERFORMANCE_GC_MAJOR
perf_hooks.constants.NODE_PERFORMANCE_GC_MINOR
perf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTAL
perf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCB
When performanceEntry.type
is equal to 'gc'
, the\nperformanceNodeEntry.detail
property will be an <Object> with two properties:
kind
<number> One of:\nperf_hooks.constants.NODE_PERFORMANCE_GC_MAJOR
perf_hooks.constants.NODE_PERFORMANCE_GC_MINOR
perf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTAL
perf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCB
flags
<number> One of:\nperf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_NO
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_FORCED
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY
perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE
When performanceEntry.type
is equal to 'http'
, the\nperformanceNodeEntry.detail
property will be an <Object> containing\nadditional information.
If performanceEntry.name
is equal to HttpClient
, the detail
\nwill contain the following properties: req
, res
. And the req
property\nwill be an <Object> containing method
, url
, headers
, the res
property\nwill be an <Object> containing statusCode
, statusMessage
, headers
.
If performanceEntry.name
is equal to HttpRequest
, the detail
\nwill contain the following properties: req
, res
. And the req
property\nwill be an <Object> containing method
, url
, headers
, the res
property\nwill be an <Object> containing statusCode
, statusMessage
, headers
.
This could add additional memory overhead and should only be used for\ndiagnostic purposes, not left turned on in production by default.
", "type": "module", "displayName": "HTTP ('http') Details" }, { "textRaw": "HTTP/2 ('http2') Details", "name": "http/2_('http2')_details", "desc": "When performanceEntry.type
is equal to 'http2'
, the\nperformanceNodeEntry.detail
property will be an <Object> containing\nadditional performance information.
If performanceEntry.name
is equal to Http2Stream
, the detail
\nwill contain the following properties:
bytesRead
<number> The number of DATA
frame bytes received for this\nHttp2Stream
.bytesWritten
<number> The number of DATA
frame bytes sent for this\nHttp2Stream
.id
<number> The identifier of the associated Http2Stream
timeToFirstByte
<number> The number of milliseconds elapsed between the\nPerformanceEntry
startTime
and the reception of the first DATA
frame.timeToFirstByteSent
<number> The number of milliseconds elapsed between\nthe PerformanceEntry
startTime
and sending of the first DATA
frame.timeToFirstHeader
<number> The number of milliseconds elapsed between the\nPerformanceEntry
startTime
and the reception of the first header.If performanceEntry.name
is equal to Http2Session
, the detail
will\ncontain the following properties:
bytesRead
<number> The number of bytes received for this Http2Session
.bytesWritten
<number> The number of bytes sent for this Http2Session
.framesReceived
<number> The number of HTTP/2 frames received by the\nHttp2Session
.framesSent
<number> The number of HTTP/2 frames sent by the Http2Session
.maxConcurrentStreams
<number> The maximum number of streams concurrently\nopen during the lifetime of the Http2Session
.pingRTT
<number> The number of milliseconds elapsed since the transmission\nof a PING
frame and the reception of its acknowledgment. Only present if\na PING
frame has been sent on the Http2Session
.streamAverageDuration
<number> The average duration (in milliseconds) for\nall Http2Stream
instances.streamCount
<number> The number of Http2Stream
instances processed by\nthe Http2Session
.type
<string> Either 'server'
or 'client'
to identify the type of\nHttp2Session
.When performanceEntry.type
is equal to 'function'
, the\nperformanceNodeEntry.detail
property will be an <Array> listing\nthe input arguments to the timed function.
When performanceEntry.type
is equal to 'net'
, the\nperformanceNodeEntry.detail
property will be an <Object> containing\nadditional information.
If performanceEntry.name
is equal to connect
, the detail
\nwill contain the following properties: host
, port
.
When performanceEntry.type
is equal to 'dns'
, the\nperformanceNodeEntry.detail
property will be an <Object> containing\nadditional information.
If performanceEntry.name
is equal to lookup
, the detail
\nwill contain the following properties: hostname
, family
, hints
, verbatim
,\naddresses
.
If performanceEntry.name
is equal to lookupService
, the detail
will\ncontain the following properties: host
, port
, hostname
, service
.
If performanceEntry.name
is equal to queryxxx
or getHostByAddr
, the detail
will\ncontain the following properties: host
, ttl
, result
. The value of result
is\nsame as the result of queryxxx
or getHostByAddr
.
This property is an extension by Node.js. It is not available in Web browsers.
\nProvides timing details for Node.js itself. The constructor of this class\nis not exposed to users.
", "properties": [ { "textRaw": "`bootstrapComplete` {number}", "type": "number", "name": "bootstrapComplete", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the Node.js process\ncompleted bootstrapping. If bootstrapping has not yet finished, the property\nhas the value of -1.
" }, { "textRaw": "`environment` {number}", "type": "number", "name": "environment", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the Node.js environment was\ninitialized.
" }, { "textRaw": "`idleTime` {number}", "type": "number", "name": "idleTime", "meta": { "added": [ "v14.10.0", "v12.19.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp of the amount of time the event loop\nhas been idle within the event loop's event provider (e.g. epoll_wait
). This\ndoes not take CPU usage into consideration. If the event loop has not yet\nstarted (e.g., in the first tick of the main script), the property has the\nvalue of 0.
The high resolution millisecond timestamp at which the Node.js event loop\nexited. If the event loop has not yet exited, the property has the value of -1.\nIt can only have a value of not -1 in a handler of the 'exit'
event.
The high resolution millisecond timestamp at which the Node.js event loop\nstarted. If the event loop has not yet started (e.g., in the first tick of the\nmain script), the property has the value of -1.
" }, { "textRaw": "`nodeStart` {number}", "type": "number", "name": "nodeStart", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the Node.js process was\ninitialized.
" }, { "textRaw": "`v8Start` {number}", "type": "number", "name": "v8Start", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the V8 platform was\ninitialized.
" } ] }, { "textRaw": "Class: `PerformanceResourceTiming`", "type": "class", "name": "PerformanceResourceTiming", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [] }, "desc": "Provides detailed network timing data regarding the loading of an application's\nresources.
\nThe constructor of this class is not exposed to users directly.
", "properties": [ { "textRaw": "`workerStart` {number}", "type": "number", "name": "workerStart", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp at immediately before dispatching\nthe fetch
request. If the resource is not intercepted by a worker the property\nwill always return 0.
The high resolution millisecond timestamp that represents the start time\nof the fetch which initiates the redirect.
" }, { "textRaw": "`redirectEnd` {number}", "type": "number", "name": "redirectEnd", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp that will be created immediately after\nreceiving the last byte of the response of the last redirect.
" }, { "textRaw": "`fetchStart` {number}", "type": "number", "name": "fetchStart", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp immediately before the Node.js starts\nto fetch the resource.
" }, { "textRaw": "`domainLookupStart` {number}", "type": "number", "name": "domainLookupStart", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp immediately before the Node.js starts\nthe domain name lookup for the resource.
" }, { "textRaw": "`domainLookupEnd` {number}", "type": "number", "name": "domainLookupEnd", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp representing the time immediately\nafter the Node.js finished the domain name lookup for the resource.
" }, { "textRaw": "`connectStart` {number}", "type": "number", "name": "connectStart", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp representing the time immediately\nbefore Node.js starts to establish the connection to the server to retrieve\nthe resource.
" }, { "textRaw": "`connectEnd` {number}", "type": "number", "name": "connectEnd", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp representing the time immediately\nafter Node.js finishes establishing the connection to the server to retrieve\nthe resource.
" }, { "textRaw": "`secureConnectionStart` {number}", "type": "number", "name": "secureConnectionStart", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp representing the time immediately\nbefore Node.js starts the handshake process to secure the current connection.
" }, { "textRaw": "`requestStart` {number}", "type": "number", "name": "requestStart", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp representing the time immediately\nbefore Node.js receives the first byte of the response from the server.
" }, { "textRaw": "`responseEnd` {number}", "type": "number", "name": "responseEnd", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "The high resolution millisecond timestamp representing the time immediately\nafter Node.js receives the last byte of the resource or immediately before\nthe transport connection is closed, whichever comes first.
" }, { "textRaw": "`transferSize` {number}", "type": "number", "name": "transferSize", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "A number representing the size (in octets) of the fetched resource. The size\nincludes the response header fields plus the response payload body.
" }, { "textRaw": "`encodedBodySize` {number}", "type": "number", "name": "encodedBodySize", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "A number representing the size (in octets) received from the fetch\n(HTTP or cache), of the payload body, before removing any applied\ncontent-codings.
" }, { "textRaw": "`decodedBodySize` {number}", "type": "number", "name": "decodedBodySize", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This property getter must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "desc": "A number representing the size (in octets) received from the fetch\n(HTTP or cache), of the message body, after removing any applied\ncontent-codings.
" } ], "methods": [ { "textRaw": "`performanceResourceTiming.toJSON()`", "type": "method", "name": "toJSON", "meta": { "added": [ "v18.2.0", "v16.17.0" ], "changes": [ { "version": "v19.0.0", "pr-url": "https://github.com/nodejs/node/pull/44483", "description": "This method must be called with the `PerformanceResourceTiming` object as the receiver." } ] }, "signatures": [ { "params": [] } ], "desc": "Returns a object
that is the JSON representation of the\nPerformanceResourceTiming
object
Get supported types.
" } ], "methods": [ { "textRaw": "`performanceObserver.disconnect()`", "type": "method", "name": "disconnect", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Disconnects the PerformanceObserver
instance from all notifications.
Subscribes the <PerformanceObserver> instance to notifications of new\n<PerformanceEntry> instances identified either by options.entryTypes
\nor options.type
:
const {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n // Called once asynchronously. `list` contains three items.\n});\nobs.observe({ type: 'mark' });\n\nfor (let n = 0; n < 3; n++)\n performance.mark(`test${n}`);\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`list` {PerformanceObserverEntryList}",
"name": "list",
"type": "PerformanceObserverEntryList"
},
{
"textRaw": "`observer` {PerformanceObserver}",
"name": "observer",
"type": "PerformanceObserver"
}
]
}
],
"desc": "PerformanceObserver
objects provide notifications when new\nPerformanceEntry
instances have been added to the Performance Timeline.
const {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n console.log(list.getEntries());\n\n performance.clearMarks();\n performance.clearMeasures();\n observer.disconnect();\n});\nobs.observe({ entryTypes: ['mark'], buffered: true });\n\nperformance.mark('test');\n
\nBecause PerformanceObserver
instances introduce their own additional\nperformance overhead, instances should not be left subscribed to notifications\nindefinitely. Users should disconnect observers as soon as they are no\nlonger needed.
The callback
is invoked when a PerformanceObserver
is\nnotified about new PerformanceEntry
instances. The callback receives a\nPerformanceObserverEntryList
instance and a reference to the\nPerformanceObserver
.
The PerformanceObserverEntryList
class is used to provide access to the\nPerformanceEntry
instances passed to a PerformanceObserver
.\nThe constructor of this class is not exposed to users.
Returns a list of PerformanceEntry
objects in chronological order\nwith respect to performanceEntry.startTime
.
const {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((perfObserverList, observer) => {\n console.log(perfObserverList.getEntries());\n /**\n * [\n * PerformanceEntry {\n * name: 'test',\n * entryType: 'mark',\n * startTime: 81.465639,\n * duration: 0,\n * detail: null\n * },\n * PerformanceEntry {\n * name: 'meow',\n * entryType: 'mark',\n * startTime: 81.860064,\n * duration: 0,\n * detail: null\n * }\n * ]\n */\n\n performance.clearMarks();\n performance.clearMeasures();\n observer.disconnect();\n});\nobs.observe({ type: 'mark' });\n\nperformance.mark('test');\nperformance.mark('meow');\n
"
},
{
"textRaw": "`performanceObserverEntryList.getEntriesByName(name[, type])`",
"type": "method",
"name": "getEntriesByName",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {PerformanceEntry\\[]}",
"name": "return",
"type": "PerformanceEntry\\[]"
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`type` {string}",
"name": "type",
"type": "string"
}
]
}
],
"desc": "Returns a list of PerformanceEntry
objects in chronological order\nwith respect to performanceEntry.startTime
whose performanceEntry.name
is\nequal to name
, and optionally, whose performanceEntry.entryType
is equal to\ntype
.
const {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((perfObserverList, observer) => {\n console.log(perfObserverList.getEntriesByName('meow'));\n /**\n * [\n * PerformanceEntry {\n * name: 'meow',\n * entryType: 'mark',\n * startTime: 98.545991,\n * duration: 0,\n * detail: null\n * }\n * ]\n */\n console.log(perfObserverList.getEntriesByName('nope')); // []\n\n console.log(perfObserverList.getEntriesByName('test', 'mark'));\n /**\n * [\n * PerformanceEntry {\n * name: 'test',\n * entryType: 'mark',\n * startTime: 63.518931,\n * duration: 0,\n * detail: null\n * }\n * ]\n */\n console.log(perfObserverList.getEntriesByName('test', 'measure')); // []\n\n performance.clearMarks();\n performance.clearMeasures();\n observer.disconnect();\n});\nobs.observe({ entryTypes: ['mark', 'measure'] });\n\nperformance.mark('test');\nperformance.mark('meow');\n
"
},
{
"textRaw": "`performanceObserverEntryList.getEntriesByType(type)`",
"type": "method",
"name": "getEntriesByType",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {PerformanceEntry\\[]}",
"name": "return",
"type": "PerformanceEntry\\[]"
},
"params": [
{
"textRaw": "`type` {string}",
"name": "type",
"type": "string"
}
]
}
],
"desc": "Returns a list of PerformanceEntry
objects in chronological order\nwith respect to performanceEntry.startTime
whose performanceEntry.entryType
\nis equal to type
.
const {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nconst obs = new PerformanceObserver((perfObserverList, observer) => {\n console.log(perfObserverList.getEntriesByType('mark'));\n /**\n * [\n * PerformanceEntry {\n * name: 'test',\n * entryType: 'mark',\n * startTime: 55.897834,\n * duration: 0,\n * detail: null\n * },\n * PerformanceEntry {\n * name: 'meow',\n * entryType: 'mark',\n * startTime: 56.350146,\n * duration: 0,\n * detail: null\n * }\n * ]\n */\n performance.clearMarks();\n performance.clearMeasures();\n observer.disconnect();\n});\nobs.observe({ type: 'mark' });\n\nperformance.mark('test');\nperformance.mark('meow');\n
"
}
]
},
{
"textRaw": "Class: `Histogram`",
"type": "class",
"name": "Histogram",
"meta": {
"added": [
"v11.10.0"
],
"changes": []
},
"properties": [
{
"textRaw": "`count` {number}",
"type": "number",
"name": "count",
"meta": {
"added": [
"v17.4.0",
"v16.14.0"
],
"changes": []
},
"desc": "The number of samples recorded by the histogram.
" }, { "textRaw": "`countBigInt` {bigint}", "type": "bigint", "name": "countBigInt", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "desc": "The number of samples recorded by the histogram.
" }, { "textRaw": "`exceeds` {number}", "type": "number", "name": "exceeds", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "desc": "The number of times the event loop delay exceeded the maximum 1 hour event\nloop delay threshold.
" }, { "textRaw": "`exceedsBigInt` {bigint}", "type": "bigint", "name": "exceedsBigInt", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "desc": "The number of times the event loop delay exceeded the maximum 1 hour event\nloop delay threshold.
" }, { "textRaw": "`max` {number}", "type": "number", "name": "max", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "desc": "The maximum recorded event loop delay.
" }, { "textRaw": "`maxBigInt` {bigint}", "type": "bigint", "name": "maxBigInt", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "desc": "The maximum recorded event loop delay.
" }, { "textRaw": "`mean` {number}", "type": "number", "name": "mean", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "desc": "The mean of the recorded event loop delays.
" }, { "textRaw": "`min` {number}", "type": "number", "name": "min", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "desc": "The minimum recorded event loop delay.
" }, { "textRaw": "`minBigInt` {bigint}", "type": "bigint", "name": "minBigInt", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "desc": "The minimum recorded event loop delay.
" }, { "textRaw": "`percentiles` {Map}", "type": "Map", "name": "percentiles", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "desc": "Returns a Map
object detailing the accumulated percentile distribution.
Returns a Map
object detailing the accumulated percentile distribution.
The standard deviation of the recorded event loop delays.
" } ], "methods": [ { "textRaw": "`histogram.percentile(percentile)`", "type": "method", "name": "percentile", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {number}", "name": "return", "type": "number" }, "params": [ { "textRaw": "`percentile` {number} A percentile value in the range (0, 100].", "name": "percentile", "type": "number", "desc": "A percentile value in the range (0, 100]." } ] } ], "desc": "Returns the value at the given percentile.
" }, { "textRaw": "`histogram.percentileBigInt(percentile)`", "type": "method", "name": "percentileBigInt", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {bigint}", "name": "return", "type": "bigint" }, "params": [ { "textRaw": "`percentile` {number} A percentile value in the range (0, 100].", "name": "percentile", "type": "number", "desc": "A percentile value in the range (0, 100]." } ] } ], "desc": "Returns the value at the given percentile.
" }, { "textRaw": "`histogram.reset()`", "type": "method", "name": "reset", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Resets the collected histogram data.
" } ] }, { "textRaw": "Class: `IntervalHistogram extends Histogram`", "type": "class", "name": "IntervalHistogram", "desc": "A Histogram
that is periodically updated on a given interval.
Disables the update interval timer. Returns true
if the timer was\nstopped, false
if it was already stopped.
Enables the update interval timer. Returns true
if the timer was\nstarted, false
if it was already started.
<IntervalHistogram> instances can be cloned via <MessagePort>. On the receiving\nend, the histogram is cloned as a plain <Histogram> object that does not\nimplement the enable()
and disable()
methods.
Adds the values from other
to this histogram.
Calculates the amount of time (in nanoseconds) that has passed since the\nprevious call to recordDelta()
and records that amount in the histogram.
The following example uses the Async Hooks and Performance APIs to measure\nthe actual duration of a Timeout operation (including the amount of time it took\nto execute the callback).
\n'use strict';\nconst async_hooks = require('node:async_hooks');\nconst {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\n\nconst set = new Set();\nconst hook = async_hooks.createHook({\n init(id, type) {\n if (type === 'Timeout') {\n performance.mark(`Timeout-${id}-Init`);\n set.add(id);\n }\n },\n destroy(id) {\n if (set.has(id)) {\n set.delete(id);\n performance.mark(`Timeout-${id}-Destroy`);\n performance.measure(`Timeout-${id}`,\n `Timeout-${id}-Init`,\n `Timeout-${id}-Destroy`);\n }\n },\n});\nhook.enable();\n\nconst obs = new PerformanceObserver((list, observer) => {\n console.log(list.getEntries()[0]);\n performance.clearMarks();\n performance.clearMeasures();\n observer.disconnect();\n});\nobs.observe({ entryTypes: ['measure'], buffered: true });\n\nsetTimeout(() => {}, 1000);\n
",
"type": "module",
"displayName": "Measuring the duration of async operations"
},
{
"textRaw": "Measuring how long it takes to load dependencies",
"name": "measuring_how_long_it_takes_to_load_dependencies",
"desc": "The following example measures the duration of require()
operations to load\ndependencies:
'use strict';\nconst {\n performance,\n PerformanceObserver,\n} = require('node:perf_hooks');\nconst mod = require('node:module');\n\n// Monkey patch the require function\nmod.Module.prototype.require =\n performance.timerify(mod.Module.prototype.require);\nrequire = performance.timerify(require);\n\n// Activate the observer\nconst obs = new PerformanceObserver((list) => {\n const entries = list.getEntries();\n entries.forEach((entry) => {\n console.log(`require('${entry[0]}')`, entry.duration);\n });\n performance.clearMarks();\n performance.clearMeasures();\n obs.disconnect();\n});\nobs.observe({ entryTypes: ['function'], buffered: true });\n\nrequire('some-module');\n
",
"type": "module",
"displayName": "Measuring how long it takes to load dependencies"
},
{
"textRaw": "Measuring how long one HTTP round-trip takes",
"name": "measuring_how_long_one_http_round-trip_takes",
"desc": "The following example is used to trace the time spent by HTTP client\n(OutgoingMessage
) and HTTP request (IncomingMessage
). For HTTP client,\nit means the time interval between starting the request and receiving the\nresponse, and for HTTP request, it means the time interval between receiving\nthe request and sending the response:
'use strict';\nconst { PerformanceObserver } = require('node:perf_hooks');\nconst http = require('node:http');\n\nconst obs = new PerformanceObserver((items) => {\n items.getEntries().forEach((item) => {\n console.log(item);\n });\n});\n\nobs.observe({ entryTypes: ['http'] });\n\nconst PORT = 8080;\n\nhttp.createServer((req, res) => {\n res.end('ok');\n}).listen(PORT, () => {\n http.get(`http://127.0.0.1:${PORT}`);\n});\n
",
"type": "module",
"displayName": "Measuring how long one HTTP round-trip takes"
},
{
"textRaw": "Measuring how long the `net.connect` (only for TCP) takes when the connection is successful",
"name": "measuring_how_long_the_`net.connect`_(only_for_tcp)_takes_when_the_connection_is_successful",
"desc": "'use strict';\nconst { PerformanceObserver } = require('node:perf_hooks');\nconst net = require('node:net');\nconst obs = new PerformanceObserver((items) => {\n items.getEntries().forEach((item) => {\n console.log(item);\n });\n});\nobs.observe({ entryTypes: ['net'] });\nconst PORT = 8080;\nnet.createServer((socket) => {\n socket.destroy();\n}).listen(PORT, () => {\n net.connect(PORT);\n});\n
",
"type": "module",
"displayName": "Measuring how long the `net.connect` (only for TCP) takes when the connection is successful"
},
{
"textRaw": "Measuring how long the DNS takes when the request is successful",
"name": "measuring_how_long_the_dns_takes_when_the_request_is_successful",
"desc": "'use strict';\nconst { PerformanceObserver } = require('node:perf_hooks');\nconst dns = require('node:dns');\nconst obs = new PerformanceObserver((items) => {\n items.getEntries().forEach((item) => {\n console.log(item);\n });\n});\nobs.observe({ entryTypes: ['dns'] });\ndns.lookup('localhost', () => {});\ndns.promises.resolve('localhost');\n
",
"type": "module",
"displayName": "Measuring how long the DNS takes when the request is successful"
}
]
}
],
"methods": [
{
"textRaw": "`perf_hooks.createHistogram([options])`",
"type": "method",
"name": "createHistogram",
"meta": {
"added": [
"v15.9.0",
"v14.18.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {RecordableHistogram}",
"name": "return",
"type": "RecordableHistogram"
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`lowest` {number|bigint} The lowest discernible value. Must be an integer value greater than 0. **Default:** `1`.",
"name": "lowest",
"type": "number|bigint",
"default": "`1`",
"desc": "The lowest discernible value. Must be an integer value greater than 0."
},
{
"textRaw": "`highest` {number|bigint} The highest recordable value. Must be an integer value that is equal to or greater than two times `lowest`. **Default:** `Number.MAX_SAFE_INTEGER`.",
"name": "highest",
"type": "number|bigint",
"default": "`Number.MAX_SAFE_INTEGER`",
"desc": "The highest recordable value. Must be an integer value that is equal to or greater than two times `lowest`."
},
{
"textRaw": "`figures` {number} The number of accuracy digits. Must be a number between `1` and `5`. **Default:** `3`.",
"name": "figures",
"type": "number",
"default": "`3`",
"desc": "The number of accuracy digits. Must be a number between `1` and `5`."
}
]
}
]
}
],
"desc": "Returns a <RecordableHistogram>.
" }, { "textRaw": "`perf_hooks.monitorEventLoopDelay([options])`", "type": "method", "name": "monitorEventLoopDelay", "meta": { "added": [ "v11.10.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {IntervalHistogram}", "name": "return", "type": "IntervalHistogram" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`resolution` {number} The sampling rate in milliseconds. Must be greater than zero. **Default:** `10`.", "name": "resolution", "type": "number", "default": "`10`", "desc": "The sampling rate in milliseconds. Must be greater than zero." } ] } ] } ], "desc": "This property is an extension by Node.js. It is not available in Web browsers.
\nCreates an IntervalHistogram
object that samples and reports the event loop\ndelay over time. The delays will be reported in nanoseconds.
Using a timer to detect approximate event loop delay works because the\nexecution of timers is tied specifically to the lifecycle of the libuv\nevent loop. That is, a delay in the loop will cause a delay in the execution\nof the timer, and those delays are specifically what this API is intended to\ndetect.
\nconst { monitorEventLoopDelay } = require('node:perf_hooks');\nconst h = monitorEventLoopDelay({ resolution: 20 });\nh.enable();\n// Do something.\nh.disable();\nconsole.log(h.min);\nconsole.log(h.max);\nconsole.log(h.mean);\nconsole.log(h.stddev);\nconsole.log(h.percentiles);\nconsole.log(h.percentile(50));\nconsole.log(h.percentile(99));\n
"
}
],
"type": "module",
"displayName": "Performance measurement APIs",
"source": "doc/api/perf_hooks.md"
},
{
"textRaw": "Permissions",
"name": "permissions",
"desc": "Permissions can be used to control what system resources the\nNode.js process has access to or what actions the process can take\nwith those resources. Permissions can also control what modules can\nbe accessed by other modules.
\nModule-based permissions control which files\nor URLs are available to other modules during application execution.\nThis can be used to control what modules can be accessed by third-party\ndependencies, for example.
\nProcess-based permissions control the Node.js\nprocess's access to resources.\nThe resource can be entirely allowed or denied, or actions related to it can\nbe controlled. For example, file system reads can be allowed while denying\nwrites.
\nIf you find a potential security vulnerability, please refer to our\nSecurity Policy.
", "modules": [ { "textRaw": "Module-based permissions", "name": "module-based_permissions", "introduced_in": "v11.8.0", "stability": 1, "stabilityText": "Experimental", "miscs": [ { "textRaw": "Policies", "name": "policy", "introduced_in": "v11.8.0", "type": "misc", "stability": 1, "stabilityText": "Experimental", "desc": "Node.js contains experimental support for creating policies on loading code.
\nPolicies are a security feature intended to ensure the integrity\nof the loaded code.
\nWhile it does not function as a provenance mechanism to trace the origin of\ncode, it serves as a robust defense against the execution of malicious code.\nUnlike runtime-based models that may restrict capabilities once the code is\nloaded, Node.js policies focus on preventing malicious code from ever being\nfully loaded into the application in the first place.
\nThe use of policies assumes safe practices for the policy\nfiles such as ensuring that policy files cannot be overwritten by the Node.js\napplication by using file permissions.
\nA best practice would be to ensure that the policy manifest is read-only for\nthe running Node.js application and that the file cannot be changed\nby the running Node.js application in any way. A typical setup would be to\ncreate the policy file as a different user id than the one running Node.js\nand granting read permissions to the user id running Node.js.
", "miscs": [ { "textRaw": "Enabling", "name": "Enabling", "type": "misc", "desc": "The --experimental-policy
flag can be used to enable features for policies\nwhen loading modules.
Once this has been set, all modules must conform to a policy manifest file\npassed to the flag:
\nnode --experimental-policy=policy.json app.js\n
\nThe policy manifest will be used to enforce constraints on code loaded by\nNode.js.
\nTo mitigate tampering with policy files on disk, an integrity for\nthe policy file itself may be provided via --policy-integrity
.\nThis allows running node
and asserting the policy file contents\neven if the file is changed on disk.
node --experimental-policy=policy.json --policy-integrity=\"sha384-SggXRQHwCG8g+DktYYzxkXRIkTiEYWBHqev0xnpCxYlqMBufKZHAHQM3/boDaI/0\" app.js\n
"
},
{
"textRaw": "Features",
"name": "features",
"modules": [
{
"textRaw": "Error behavior",
"name": "error_behavior",
"desc": "When a policy check fails, Node.js by default will throw an error.\nIt is possible to change the error behavior to one of a few possibilities\nby defining an \"onerror\" field in a policy manifest. The following values are\navailable to change the behavior:
\n\"exit\"
: will exit the process immediately.\nNo cleanup code will be allowed to run.\"log\"
: will log the error at the site of the failure.\"throw\"
: will throw a JS error at the site of the failure. This is the\ndefault.{\n \"onerror\": \"log\",\n \"resources\": {\n \"./app/checked.js\": {\n \"integrity\": \"sha384-SggXRQHwCG8g+DktYYzxkXRIkTiEYWBHqev0xnpCxYlqMBufKZHAHQM3/boDaI/0\"\n }\n }\n}\n
",
"type": "module",
"displayName": "Error behavior"
},
{
"textRaw": "Integrity checks",
"name": "integrity_checks",
"desc": "Policy files must use integrity checks with Subresource Integrity strings\ncompatible with the browser\nintegrity attribute\nassociated with absolute URLs.
\nWhen using require()
or import
all resources involved in loading are checked\nfor integrity if a policy manifest has been specified. If a resource does not\nmatch the integrity listed in the manifest, an error will be thrown.
An example policy file that would allow loading a file checked.js
:
{\n \"resources\": {\n \"./app/checked.js\": {\n \"integrity\": \"sha384-SggXRQHwCG8g+DktYYzxkXRIkTiEYWBHqev0xnpCxYlqMBufKZHAHQM3/boDaI/0\"\n }\n }\n}\n
\nEach resource listed in the policy manifest can be of one the following\nformats to determine its location:
\n./resource.js
, ../resource.js
, or /resource.js
.file:///resource.js
.When loading resources the entire URL must match including search parameters\nand hash fragment. ./a.js?b
will not be used when attempting to load\n./a.js
and vice versa.
To generate integrity strings, a script such as\nnode -e 'process.stdout.write(\"sha256-\");process.stdin.pipe(crypto.createHash(\"sha256\").setEncoding(\"base64\")).pipe(process.stdout)' < FILE
\ncan be used.
Integrity can be specified as the boolean value true
to accept any\nbody for the resource which can be useful for local development. It is not\nrecommended in production since it would allow unexpected alteration of\nresources to be considered valid.
An application may need to ship patched versions of modules or to prevent\nmodules from allowing all modules access to all other modules. Redirection\ncan be used by intercepting attempts to load the modules wishing to be\nreplaced.
\n{\n \"resources\": {\n \"./app/checked.js\": {\n \"dependencies\": {\n \"fs\": true,\n \"os\": \"./app/node_modules/alt-os\",\n \"http\": { \"import\": true }\n }\n }\n }\n}\n
\nThe dependencies are keyed by the requested specifier string and have values\nof either true
, null
, a string pointing to a module to be resolved,\nor a conditions object.
The specifier string does not perform any searching and must match exactly what\nis provided to the require()
or import
except for a canonicalization step.\nTherefore, multiple specifiers may be needed in the policy if it uses multiple\ndifferent strings to point to the same module (such as excluding the extension).
Specifier strings are canonicalized but not resolved prior to be used for\nmatching in order to have some compatibility with import maps, for example if a\nresource file:///C:/app/utils.js
was given the following redirection from a\npolicy located at file:///C:/app/policy.json
:
{\n \"resources\": {\n \"file:///C:/app/utils.js\": {\n \"dependencies\": {\n \"./utils.js\": \"./utils-v2.js\"\n }\n }\n }\n}\n
\nAny specifier used to load file:///C:/app/utils.js
would then be intercepted\nand redirected to file:///C:/app/utils-v2.js
instead regardless of using an\nabsolute or relative specifier. However, if a specifier that is not an absolute\nor relative URL string is used, it would not be intercepted. So, if an import\nsuch as import('#utils')
was used, it would not be intercepted.
If the value of the redirection is true
, a \"dependencies\" field at the top of\nthe policy file will be used. If that field at the top of the policy file is\ntrue
the default node searching algorithms are used to find the module.
If the value of the redirection is a string, it is resolved relative to\nthe manifest and then immediately used without searching.
\nAny specifier string for which resolution is attempted and that is not listed in\nthe dependencies results in an error according to the policy.
\nA boolean value of true
for the dependencies map can be specified to allow a\nmodule to load any specifier without redirection. This can be useful for local\ndevelopment and may have some valid usage in production, but should be used\nonly with care after auditing a module to ensure its behavior is valid.
Similar to \"exports\"
in package.json
, dependencies can also be specified to\nbe objects containing conditions which branch how dependencies are loaded. In\nthe preceding example, \"http\"
is allowed when the \"import\"
condition is\npart of loading it.
A value of null
for the resolved value causes the resolution to fail. This\ncan be used to ensure some kinds of dynamic access are explicitly prevented.
Unknown values for the resolved module location cause failures but are\nnot guaranteed to be forward compatible.
\nAll the guarantees for policy redirection are specified in the\nGuarantees section.
\nRedirected dependencies can provide attenuated or modified functionality as fits\nthe application. For example, log data about timing of function durations by\nwrapping the original:
\nconst original = require('fn');\nmodule.exports = function fn(...args) {\n console.time();\n try {\n return new.target ?\n Reflect.construct(original, args) :\n Reflect.apply(original, this, args);\n } finally {\n console.timeEnd();\n }\n};\n
",
"type": "module",
"displayName": "Dependency redirection"
}
],
"type": "misc",
"displayName": "Features"
},
{
"textRaw": "Scopes",
"name": "scopes",
"desc": "Use the \"scopes\"
field of a manifest to set configuration for many resources\nat once. The \"scopes\"
field works by matching resources by their segments.\nIf a scope or resource includes \"cascade\": true
, unknown specifiers will\nbe searched for in their containing scope. The containing scope for cascading\nis found by recursively reducing the resource URL by removing segments for\nspecial schemes, keeping trailing \"/\"
suffixes, and removing the query and\nhash fragment. This leads to the eventual reduction of the URL to its origin.\nIf the URL is non-special the scope will be located by the URL's origin. If no\nscope is found for the origin or in the case of opaque origins, a protocol\nstring can be used as a scope. If no scope is found for the URL's protocol, a\nfinal empty string \"\"
scope will be used.
Note, blob:
URLs adopt their origin from the path they contain, and so a scope\nof \"blob:https://nodejs.org\"
will have no effect since no URL can have an\norigin of blob:https://nodejs.org
; URLs starting with\nblob:https://nodejs.org/
will use https://nodejs.org
for its origin and\nthus https:
for its protocol scope. For opaque origin blob:
URLs they will\nhave blob:
for their protocol scope since they do not adopt origins.
{\n \"scopes\": {\n \"file:///C:/app/\": {},\n \"file:\": {},\n \"\": {}\n }\n}\n
\nGiven a file located at file:///C:/app/bin/main.js
, the following scopes would\nbe checked in order:
\"file:///C:/app/bin/\"
This determines the policy for all file based resources within\n\"file:///C:/app/bin/\"
. This is not in the \"scopes\"
field of the policy and\nwould be skipped. Adding this scope to the policy would cause it to be used\nprior to the \"file:///C:/app/\"
scope.
\"file:///C:/app/\"
This determines the policy for all file based resources within\n\"file:///C:/app/\"
. This is in the \"scopes\"
field of the policy and it would\ndetermine the policy for the resource at file:///C:/app/bin/main.js
. If the\nscope has \"cascade\": true
, any unsatisfied queries about the resource would\ndelegate to the next relevant scope for file:///C:/app/bin/main.js
, \"file:\"
.
\"file:///C:/\"
This determines the policy for all file based resources within \"file:///C:/\"
.\nThis is not in the \"scopes\"
field of the policy and would be skipped. It would\nnot be used for file:///C:/app/bin/main.js
unless \"file:///C:/app/\"
is set\nto cascade or is not in the \"scopes\"
of the policy.
\"file:///\"
This determines the policy for all file based resources on the localhost
. This\nis not in the \"scopes\"
field of the policy and would be skipped. It would not\nbe used for file:///C:/app/bin/main.js
unless \"file:///C:/\"
is set to\ncascade or is not in the \"scopes\"
of the policy.
\"file:\"
This determines the policy for all file based resources. It would not be used\nfor file:///C:/app/bin/main.js
unless \"file:///\"
is set to cascade or is not\nin the \"scopes\"
of the policy.
\"\"
This determines the policy for all resources. It would not be used for\nfile:///C:/app/bin/main.js
unless \"file:\"
is set to cascade.
Setting an integrity to true
on a scope will set the integrity for any\nresource not found in the manifest to true
.
Setting an integrity to null
on a scope will set the integrity for any\nresource not found in the manifest to fail matching.
Not including an integrity is the same as setting the integrity to null
.
\"cascade\"
for integrity checks will be ignored if \"integrity\"
is explicitly\nset.
The following example allows loading any file:
\n{\n \"scopes\": {\n \"file:\": {\n \"integrity\": true\n }\n }\n}\n
",
"type": "module",
"displayName": "Integrity using scopes"
},
{
"textRaw": "Dependency redirection using scopes",
"name": "dependency_redirection_using_scopes",
"desc": "The following example, would allow access to fs
for all resources within\n./app/
:
{\n \"resources\": {\n \"./app/checked.js\": {\n \"cascade\": true,\n \"integrity\": true\n }\n },\n \"scopes\": {\n \"./app/\": {\n \"dependencies\": {\n \"fs\": true\n }\n }\n }\n}\n
\nThe following example, would allow access to fs
for all data:
resources:
{\n \"resources\": {\n \"data:text/javascript,import('node:fs');\": {\n \"cascade\": true,\n \"integrity\": true\n }\n },\n \"scopes\": {\n \"data:\": {\n \"dependencies\": {\n \"fs\": true\n }\n }\n }\n}\n
\nGiven an import map:
\n{\n \"imports\": {\n \"react\": \"./app/node_modules/react/index.js\"\n },\n \"scopes\": {\n \"./ssr/\": {\n \"react\": \"./app/node_modules/server-side-react/index.js\"\n }\n }\n}\n
\n{\n \"dependencies\": true,\n \"scopes\": {\n \"\": {\n \"cascade\": true,\n \"dependencies\": {\n \"react\": \"./app/node_modules/react/index.js\"\n }\n },\n \"./ssr/\": {\n \"cascade\": true,\n \"dependencies\": {\n \"react\": \"./app/node_modules/server-side-react/index.js\"\n }\n }\n }\n}\n
\nImport maps assume you can get any resource by default. This means\n\"dependencies\"
at the top level of the policy should be set to true
.\nPolicies require this to be opt-in since it enables all resources of the\napplication cross linkage which doesn't make sense for many scenarios. They also\nassume any given scope has access to any scope above its allowed dependencies;\nall scopes emulating import maps must set \"cascade\": true
.
Import maps only have a single top level scope for their \"imports\". So for\nemulating \"imports\"
use the \"\"
scope. For emulating \"scopes\"
use the\n\"scopes\"
in a similar manner to how \"scopes\"
works in import maps.
Caveats: Policies do not use string matching for various finding of scope. They\ndo URL traversals. This means things like blob:
and data:
URLs might not be\nentirely interoperable between the two systems. For example import maps can\npartially match a data:
or blob:
URL by partitioning the URL on a /
\ncharacter, policies intentionally cannot. For blob:
URLs import map scopes do\nnot adopt the origin of the blob:
URL.
Additionally, import maps only work on import
so it may be desirable to add a\n\"import\"
condition to all dependency mappings.
require()
, import()
or new Module()
.require.cache
which allow access to loaded modules.\nPolicy redirection only affects specifiers to require()
and\nimport
.The Node.js Permission Model is a mechanism for restricting access to specific\nresources during execution.\nThe API exists behind a flag --experimental-permission
which when enabled,\nwill restrict access to all available permissions.
The available permissions are documented by the --experimental-permission
\nflag.
When starting Node.js with --experimental-permission
,\nthe ability to access the file system through the fs
module, spawn processes,\nuse node:worker_threads
, native addons, and enable the runtime inspector\nwill be restricted.
$ node --experimental-permission index.js\nnode:internal/modules/cjs/loader:171\n const result = internalModuleStat(filename);\n ^\n\nError: Access to this API has been restricted\n at stat (node:internal/modules/cjs/loader:171:18)\n at Module._findPath (node:internal/modules/cjs/loader:627:16)\n at resolveMainPath (node:internal/modules/run_main:19:25)\n at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:76:24)\n at node:internal/main/run_main_module:23:47 {\n code: 'ERR_ACCESS_DENIED',\n permission: 'FileSystemRead',\n resource: '/home/user/index.js'\n}\n
\nAllowing access to spawning a process and creating worker threads can be done\nusing the --allow-child-process
and --allow-worker
respectively.
To allow native addons when using permission model, use the --allow-addons
\nflag.
When enabling the Permission Model through the --experimental-permission
\nflag a new property permission
is added to the process
object.\nThis property contains one function:
API call to check permissions at runtime (permission.has()
)
process.permission.has('fs.write'); // true\nprocess.permission.has('fs.write', '/home/rafaelgss/protected-folder'); // true\n\nprocess.permission.has('fs.read'); // true\nprocess.permission.has('fs.read', '/home/rafaelgss/protected-folder'); // false\n
"
}
],
"type": "misc",
"displayName": "Runtime API"
},
{
"textRaw": "File System Permissions",
"name": "file_system_permissions",
"desc": "To allow access to the file system, use the --allow-fs-read
and\n--allow-fs-write
flags:
$ node --experimental-permission --allow-fs-read=* --allow-fs-write=* index.js\nHello world!\n(node:19836) ExperimentalWarning: Permission is an experimental feature\n(Use `node --trace-warnings ...` to show where the warning was created)\n
\nThe valid arguments for both flags are:
\n*
- To allow all FileSystemRead
or FileSystemWrite
operations,\nrespectively.,
) to allow only matching FileSystemRead
or\nFileSystemWrite
operations, respectively.Example:
\n--allow-fs-read=*
- It will allow all FileSystemRead
operations.--allow-fs-write=*
- It will allow all FileSystemWrite
operations.--allow-fs-write=/tmp/
- It will allow FileSystemWrite
access to the /tmp/
\nfolder.--allow-fs-read=/tmp/ --allow-fs-read=/home/.gitignore
- It allows FileSystemRead
access\nto the /tmp/
folder and the /home/.gitignore
path.Wildcards are supported too:
\n--allow-fs-read=/home/test*
will allow read access to everything\nthat matches the wildcard. e.g: /home/test/file1
or /home/test2
After passing a wildcard character (*
) all subsequent characters will\nbe ignored. For example: /home/*.js
will work similar to /home/*
.
There are constraints you need to know before using this system:
\n--env-file
or --openssl-config
are designed\nto read files before environment initialization. As a result, such flags are\nnot subject to the rules of the Permission Model.--allow-fs-*
).Source Code: lib/punycode.js
\nThe version of the punycode module bundled in Node.js is being deprecated.\nIn a future major version of Node.js this module will be removed. Users\ncurrently depending on the punycode
module should switch to using the\nuserland-provided Punycode.js module instead. For punycode-based URL\nencoding, see url.domainToASCII
or, more generally, the\nWHATWG URL API.
The punycode
module is a bundled version of the Punycode.js module. It\ncan be accessed using:
const punycode = require('punycode');\n
\nPunycode is a character encoding scheme defined by RFC 3492 that is\nprimarily intended for use in Internationalized Domain Names. Because host\nnames in URLs are limited to ASCII characters only, Domain Names that contain\nnon-ASCII characters must be converted into ASCII using the Punycode scheme.\nFor instance, the Japanese character that translates into the English word,\n'example'
is '例'
. The Internationalized Domain Name, '例.com'
(equivalent\nto 'example.com'
) is represented by Punycode as the ASCII string\n'xn--fsq.com'
.
The punycode
module provides a simple implementation of the Punycode standard.
The punycode
module is a third-party dependency used by Node.js and\nmade available to developers as a convenience. Fixes or other modifications to\nthe module must be directed to the Punycode.js project.
The punycode.decode()
method converts a Punycode string of ASCII-only\ncharacters to the equivalent string of Unicode codepoints.
punycode.decode('maana-pta'); // 'mañana'\npunycode.decode('--dqo34k'); // '☃-⌘'\n
"
},
{
"textRaw": "`punycode.encode(string)`",
"type": "method",
"name": "encode",
"meta": {
"added": [
"v0.5.1"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`string` {string}",
"name": "string",
"type": "string"
}
]
}
],
"desc": "The punycode.encode()
method converts a string of Unicode codepoints to a\nPunycode string of ASCII-only characters.
punycode.encode('mañana'); // 'maana-pta'\npunycode.encode('☃-⌘'); // '--dqo34k'\n
"
},
{
"textRaw": "`punycode.toASCII(domain)`",
"type": "method",
"name": "toASCII",
"meta": {
"added": [
"v0.6.1"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`domain` {string}",
"name": "domain",
"type": "string"
}
]
}
],
"desc": "The punycode.toASCII()
method converts a Unicode string representing an\nInternationalized Domain Name to Punycode. Only the non-ASCII parts of the\ndomain name will be converted. Calling punycode.toASCII()
on a string that\nalready only contains ASCII characters will have no effect.
// encode domain names\npunycode.toASCII('mañana.com'); // 'xn--maana-pta.com'\npunycode.toASCII('☃-⌘.com'); // 'xn----dqo34k.com'\npunycode.toASCII('example.com'); // 'example.com'\n
"
},
{
"textRaw": "`punycode.toUnicode(domain)`",
"type": "method",
"name": "toUnicode",
"meta": {
"added": [
"v0.6.1"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`domain` {string}",
"name": "domain",
"type": "string"
}
]
}
],
"desc": "The punycode.toUnicode()
method converts a string representing a domain name\ncontaining Punycode encoded characters into Unicode. Only the Punycode\nencoded parts of the domain name are be converted.
// decode domain names\npunycode.toUnicode('xn--maana-pta.com'); // 'mañana.com'\npunycode.toUnicode('xn----dqo34k.com'); // '☃-⌘.com'\npunycode.toUnicode('example.com'); // 'example.com'\n
"
}
],
"properties": [
{
"textRaw": "`punycode.ucs2`",
"name": "ucs2",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"methods": [
{
"textRaw": "`punycode.ucs2.decode(string)`",
"type": "method",
"name": "decode",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`string` {string}",
"name": "string",
"type": "string"
}
]
}
],
"desc": "The punycode.ucs2.decode()
method returns an array containing the numeric\ncodepoint values of each Unicode symbol in the string.
punycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]\n// surrogate pair for U+1D306 tetragram for centre:\npunycode.ucs2.decode('\\uD834\\uDF06'); // [0x1D306]\n
"
},
{
"textRaw": "`punycode.ucs2.encode(codePoints)`",
"type": "method",
"name": "encode",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`codePoints` {integer\\[]}",
"name": "codePoints",
"type": "integer\\[]"
}
]
}
],
"desc": "The punycode.ucs2.encode()
method returns a string based on an array of\nnumeric code point values.
punycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'\npunycode.ucs2.encode([0x1D306]); // '\\uD834\\uDF06'\n
"
}
]
},
{
"textRaw": "`version` {string}",
"type": "string",
"name": "version",
"meta": {
"added": [
"v0.6.1"
],
"changes": []
},
"desc": "Returns a string identifying the current Punycode.js version number.
" } ], "type": "module", "displayName": "Punycode", "source": "doc/api/punycode.md" }, { "textRaw": "Query string", "name": "querystring", "introduced_in": "v0.1.25", "stability": 2, "stabilityText": "Stable", "desc": "Source Code: lib/querystring.js
\nThe node:querystring
module provides utilities for parsing and formatting URL\nquery strings. It can be accessed using:
const querystring = require('node:querystring');\n
\nquerystring
is more performant than <URLSearchParams> but is not a\nstandardized API. Use <URLSearchParams> when performance is not critical or\nwhen compatibility with browser code is desirable.
The querystring.decode()
function is an alias for querystring.parse()
.
The querystring.encode()
function is an alias for querystring.stringify()
.
The querystring.escape()
method performs URL percent-encoding on the given\nstr
in a manner that is optimized for the specific requirements of URL\nquery strings.
The querystring.escape()
method is used by querystring.stringify()
and is\ngenerally not expected to be used directly. It is exported primarily to allow\napplication code to provide a replacement percent-encoding implementation if\nnecessary by assigning querystring.escape
to an alternative function.
The querystring.parse()
method parses a URL query string (str
) into a\ncollection of key and value pairs.
For example, the query string 'foo=bar&abc=xyz&abc=123'
is parsed into:
{\n \"foo\": \"bar\",\n \"abc\": [\"xyz\", \"123\"]\n}\n
\nThe object returned by the querystring.parse()
method does not\nprototypically inherit from the JavaScript Object
. This means that typical\nObject
methods such as obj.toString()
, obj.hasOwnProperty()
, and others\nare not defined and will not work.
By default, percent-encoded characters within the query string will be assumed\nto use UTF-8 encoding. If an alternative character encoding is used, then an\nalternative decodeURIComponent
option will need to be specified:
// Assuming gbkDecodeURIComponent function already exists...\n\nquerystring.parse('w=%D6%D0%CE%C4&foo=bar', null, null,\n { decodeURIComponent: gbkDecodeURIComponent });\n
"
},
{
"textRaw": "`querystring.stringify(obj[, sep[, eq[, options]]])`",
"type": "method",
"name": "stringify",
"meta": {
"added": [
"v0.1.25"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`obj` {Object} The object to serialize into a URL query string",
"name": "obj",
"type": "Object",
"desc": "The object to serialize into a URL query string"
},
{
"textRaw": "`sep` {string} The substring used to delimit key and value pairs in the query string. **Default:** `'&'`.",
"name": "sep",
"type": "string",
"default": "`'&'`",
"desc": "The substring used to delimit key and value pairs in the query string."
},
{
"textRaw": "`eq` {string}. The substring used to delimit keys and values in the query string. **Default:** `'='`.",
"name": "eq",
"type": "string",
"default": "`'='`",
"desc": ". The substring used to delimit keys and values in the query string."
},
{
"textRaw": "`options`",
"name": "options",
"options": [
{
"textRaw": "`encodeURIComponent` {Function} The function to use when converting URL-unsafe characters to percent-encoding in the query string. **Default:** `querystring.escape()`.",
"name": "encodeURIComponent",
"type": "Function",
"default": "`querystring.escape()`",
"desc": "The function to use when converting URL-unsafe characters to percent-encoding in the query string."
}
]
}
]
}
],
"desc": "The querystring.stringify()
method produces a URL query string from a\ngiven obj
by iterating through the object's \"own properties\".
It serializes the following types of values passed in obj
:\n<string> | <number> | <bigint> | <boolean> | <string[]> | <number[]> | <bigint[]> | <boolean[]>\nThe numeric values must be finite. Any other input values will be coerced to\nempty strings.
querystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], corge: '' });\n// Returns 'foo=bar&baz=qux&baz=quux&corge='\n\nquerystring.stringify({ foo: 'bar', baz: 'qux' }, ';', ':');\n// Returns 'foo:bar;baz:qux'\n
\nBy default, characters requiring percent-encoding within the query string will\nbe encoded as UTF-8. If an alternative encoding is required, then an alternative\nencodeURIComponent
option will need to be specified:
// Assuming gbkEncodeURIComponent function already exists,\n\nquerystring.stringify({ w: '中文', foo: 'bar' }, null, null,\n { encodeURIComponent: gbkEncodeURIComponent });\n
"
},
{
"textRaw": "`querystring.unescape(str)`",
"type": "method",
"name": "unescape",
"meta": {
"added": [
"v0.1.25"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`str` {string}",
"name": "str",
"type": "string"
}
]
}
],
"desc": "The querystring.unescape()
method performs decoding of URL percent-encoded\ncharacters on the given str
.
The querystring.unescape()
method is used by querystring.parse()
and is\ngenerally not expected to be used directly. It is exported primarily to allow\napplication code to provide a replacement decoding implementation if\nnecessary by assigning querystring.unescape
to an alternative function.
By default, the querystring.unescape()
method will attempt to use the\nJavaScript built-in decodeURIComponent()
method to decode. If that fails,\na safer equivalent that does not throw on malformed URLs will be used.
Source Code: lib/readline.js
\nThe node:readline
module provides an interface for reading data from a\nReadable stream (such as process.stdin
) one line at a time.
To use the promise-based APIs:
\nimport * as readline from 'node:readline/promises';\n
\nconst readline = require('node:readline/promises');\n
\nTo use the callback and sync APIs:
\nimport * as readline from 'node:readline';\n
\nconst readline = require('node:readline');\n
\nThe following simple example illustrates the basic use of the node:readline
\nmodule.
import * as readline from 'node:readline/promises';\nimport { stdin as input, stdout as output } from 'node:process';\n\nconst rl = readline.createInterface({ input, output });\n\nconst answer = await rl.question('What do you think of Node.js? ');\n\nconsole.log(`Thank you for your valuable feedback: ${answer}`);\n\nrl.close();\n
\nconst readline = require('node:readline');\nconst { stdin: input, stdout: output } = require('node:process');\n\nconst rl = readline.createInterface({ input, output });\n\nrl.question('What do you think of Node.js? ', (answer) => {\n // TODO: Log the answer in a database\n console.log(`Thank you for your valuable feedback: ${answer}`);\n\n rl.close();\n});\n
\nOnce this code is invoked, the Node.js application will not terminate until the\nreadline.Interface
is closed because the interface waits for data to be\nreceived on the input
stream.
Instances of the InterfaceConstructor
class are constructed using the\nreadlinePromises.createInterface()
or readline.createInterface()
method.\nEvery instance is associated with a single input
Readable stream and a\nsingle output
Writable stream.\nThe output
stream is used to print prompts for user input that arrives on,\nand is read from, the input
stream.
The 'close'
event is emitted when one of the following occur:
rl.close()
method is called and the InterfaceConstructor
instance has\nrelinquished control over the input
and output
streams;input
stream receives its 'end'
event;input
stream receives Ctrl+D to signal\nend-of-transmission (EOT);input
stream receives Ctrl+C to signal SIGINT
\nand there is no 'SIGINT'
event listener registered on the\nInterfaceConstructor
instance.The listener function is called without passing any arguments.
\nThe InterfaceConstructor
instance is finished once the 'close'
event is\nemitted.
The 'line'
event is emitted whenever the input
stream receives an\nend-of-line input (\\n
, \\r
, or \\r\\n
). This usually occurs when the user\npresses Enter or Return.
The 'line'
event is also emitted if new data has been read from a stream and\nthat stream ends without a final end-of-line marker.
The listener function is called with a string containing the single line of\nreceived input.
\nrl.on('line', (input) => {\n console.log(`Received: ${input}`);\n});\n
"
},
{
"textRaw": "Event: `'history'`",
"type": "event",
"name": "history",
"meta": {
"added": [
"v15.8.0",
"v14.18.0"
],
"changes": []
},
"params": [],
"desc": "The 'history'
event is emitted whenever the history array has changed.
The listener function is called with an array containing the history array.\nIt will reflect all changes, added lines and removed lines due to\nhistorySize
and removeHistoryDuplicates
.
The primary purpose is to allow a listener to persist the history.\nIt is also possible for the listener to change the history object. This\ncould be useful to prevent certain lines to be added to the history, like\na password.
\nrl.on('history', (history) => {\n console.log(`Received: ${history}`);\n});\n
"
},
{
"textRaw": "Event: `'pause'`",
"type": "event",
"name": "pause",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'pause'
event is emitted when one of the following occur:
input
stream is paused.input
stream is not paused and receives the 'SIGCONT'
event. (See\nevents 'SIGTSTP'
and 'SIGCONT'
.)The listener function is called without passing any arguments.
\nrl.on('pause', () => {\n console.log('Readline paused.');\n});\n
"
},
{
"textRaw": "Event: `'resume'`",
"type": "event",
"name": "resume",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'resume'
event is emitted whenever the input
stream is resumed.
The listener function is called without passing any arguments.
\nrl.on('resume', () => {\n console.log('Readline resumed.');\n});\n
"
},
{
"textRaw": "Event: `'SIGCONT'`",
"type": "event",
"name": "SIGCONT",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'SIGCONT'
event is emitted when a Node.js process previously moved into\nthe background using Ctrl+Z (i.e. SIGTSTP
) is then\nbrought back to the foreground using fg(1p)
.
If the input
stream was paused before the SIGTSTP
request, this event will\nnot be emitted.
The listener function is invoked without passing any arguments.
\nrl.on('SIGCONT', () => {\n // `prompt` will automatically resume the stream\n rl.prompt();\n});\n
\nThe 'SIGCONT'
event is not supported on Windows.
The 'SIGINT'
event is emitted whenever the input
stream receives\na Ctrl+C input, known typically as SIGINT
. If there are no\n'SIGINT'
event listeners registered when the input
stream receives a\nSIGINT
, the 'pause'
event will be emitted.
The listener function is invoked without passing any arguments.
\nrl.on('SIGINT', () => {\n rl.question('Are you sure you want to exit? ', (answer) => {\n if (answer.match(/^y(es)?$/i)) rl.pause();\n });\n});\n
"
},
{
"textRaw": "Event: `'SIGTSTP'`",
"type": "event",
"name": "SIGTSTP",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'SIGTSTP'
event is emitted when the input
stream receives\na Ctrl+Z input, typically known as SIGTSTP
. If there are\nno 'SIGTSTP'
event listeners registered when the input
stream receives a\nSIGTSTP
, the Node.js process will be sent to the background.
When the program is resumed using fg(1p)
, the 'pause'
and 'SIGCONT'
events\nwill be emitted. These can be used to resume the input
stream.
The 'pause'
and 'SIGCONT'
events will not be emitted if the input
was\npaused before the process was sent to the background.
The listener function is invoked without passing any arguments.
\nrl.on('SIGTSTP', () => {\n // This will override SIGTSTP and prevent the program from going to the\n // background.\n console.log('Caught SIGTSTP.');\n});\n
\nThe 'SIGTSTP'
event is not supported on Windows.
The rl.close()
method closes the InterfaceConstructor
instance and\nrelinquishes control over the input
and output
streams. When called,\nthe 'close'
event will be emitted.
Calling rl.close()
does not immediately stop other events (including 'line'
)\nfrom being emitted by the InterfaceConstructor
instance.
The rl.pause()
method pauses the input
stream, allowing it to be resumed\nlater if necessary.
Calling rl.pause()
does not immediately pause other events (including\n'line'
) from being emitted by the InterfaceConstructor
instance.
The rl.prompt()
method writes the InterfaceConstructor
instances configured\nprompt
to a new line in output
in order to provide a user with a new\nlocation at which to provide input.
When called, rl.prompt()
will resume the input
stream if it has been\npaused.
If the InterfaceConstructor
was created with output
set to null
or\nundefined
the prompt is not written.
The rl.resume()
method resumes the input
stream if it has been paused.
The rl.setPrompt()
method sets the prompt that will be written to output
\nwhenever rl.prompt()
is called.
The rl.getPrompt()
method returns the current prompt used by rl.prompt()
.
The rl.write()
method will write either data
or a key sequence identified\nby key
to the output
. The key
argument is supported only if output
is\na TTY text terminal. See TTY keybindings for a list of key\ncombinations.
If key
is specified, data
is ignored.
When called, rl.write()
will resume the input
stream if it has been\npaused.
If the InterfaceConstructor
was created with output
set to null
or\nundefined
the data
and key
are not written.
rl.write('Delete this!');\n// Simulate Ctrl+U to delete the line written previously\nrl.write(null, { ctrl: true, name: 'u' });\n
\nThe rl.write()
method will write the data to the readline
Interface
's\ninput
as if it were provided by the user.
Create an AsyncIterator
object that iterates through each line in the input\nstream as a string. This method allows asynchronous iteration of\nInterfaceConstructor
objects through for await...of
loops.
Errors in the input stream are not forwarded.
\nIf the loop is terminated with break
, throw
, or return
,\nrl.close()
will be called. In other words, iterating over a\nInterfaceConstructor
will always consume the input stream fully.
Performance is not on par with the traditional 'line'
event API. Use 'line'
\ninstead for performance-sensitive applications.
async function processLineByLine() {\n const rl = readline.createInterface({\n // ...\n });\n\n for await (const line of rl) {\n // Each line in the readline input will be successively available here as\n // `line`.\n }\n}\n
\nreadline.createInterface()
will start to consume the input stream once\ninvoked. Having asynchronous operations between interface creation and\nasynchronous iteration may result in missed lines.
Returns the real position of the cursor in relation to the input\nprompt + string. Long input (wrapping) strings, as well as multiple\nline prompts are included in the calculations.
" } ], "properties": [ { "textRaw": "`line` {string}", "type": "string", "name": "line", "meta": { "added": [ "v0.1.98" ], "changes": [ { "version": [ "v15.8.0", "v14.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/33676", "description": "Value will always be a string, never undefined." } ] }, "desc": "The current input data being processed by node.
\nThis can be used when collecting input from a TTY stream to retrieve the\ncurrent value that has been processed thus far, prior to the line
event\nbeing emitted. Once the line
event has been emitted, this property will\nbe an empty string.
Be aware that modifying the value during the instance runtime may have\nunintended consequences if rl.cursor
is not also controlled.
If not using a TTY stream for input, use the 'line'
event.
One possible use case would be as follows:
\nconst values = ['lorem ipsum', 'dolor sit amet'];\nconst rl = readline.createInterface(process.stdin);\nconst showResults = debounce(() => {\n console.log(\n '\\n',\n values.filter((val) => val.startsWith(rl.line)).join(' '),\n );\n}, 300);\nprocess.stdin.on('keypress', (c, k) => {\n showResults();\n});\n
"
},
{
"textRaw": "`cursor` {number|undefined}",
"type": "number|undefined",
"name": "cursor",
"meta": {
"added": [
"v0.1.98"
],
"changes": []
},
"desc": "The cursor position relative to rl.line
.
This will track where the current cursor lands in the input string, when\nreading input from a TTY stream. The position of cursor determines the\nportion of the input string that will be modified as input is processed,\nas well as the column where the terminal caret will be rendered.
" } ] } ], "modules": [ { "textRaw": "Promises API", "name": "promises_api", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "classes": [ { "textRaw": "Class: `readlinePromises.Interface`", "type": "class", "name": "readlinePromises.Interface", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "desc": "Instances of the readlinePromises.Interface
class are constructed using the\nreadlinePromises.createInterface()
method. Every instance is associated with a\nsingle input
Readable stream and a single output
Writable stream.\nThe output
stream is used to print prompts for user input that arrives on,\nand is read from, the input
stream.
The rl.question()
method displays the query
by writing it to the output
,\nwaits for user input to be provided on input
, then invokes the callback
\nfunction passing the provided input as the first argument.
When called, rl.question()
will resume the input
stream if it has been\npaused.
If the readlinePromises.Interface
was created with output
set to null
or\nundefined
the query
is not written.
If the question is called after rl.close()
, it returns a rejected promise.
Example usage:
\nconst answer = await rl.question('What is your favorite food? ');\nconsole.log(`Oh, so your favorite food is ${answer}`);\n
\nUsing an AbortSignal
to cancel a question.
const signal = AbortSignal.timeout(10_000);\n\nsignal.addEventListener('abort', () => {\n console.log('The food question timed out');\n}, { once: true });\n\nconst answer = await rl.question('What is your favorite food? ', { signal });\nconsole.log(`Oh, so your favorite food is ${answer}`);\n
"
}
]
},
{
"textRaw": "Class: `readlinePromises.Readline`",
"type": "class",
"name": "readlinePromises.Readline",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"methods": [
{
"textRaw": "`rl.clearLine(dir)`",
"type": "method",
"name": "clearLine",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: this",
"name": "return",
"desc": "this"
},
"params": [
{
"textRaw": "`dir` {integer}",
"name": "dir",
"type": "integer",
"options": [
{
"textRaw": "`-1`: to the left from cursor",
"name": "-1",
"desc": "to the left from cursor"
},
{
"textRaw": "`1`: to the right from cursor",
"name": "1",
"desc": "to the right from cursor"
},
{
"textRaw": "`0`: the entire line",
"name": "0",
"desc": "the entire line"
}
]
}
]
}
],
"desc": "The rl.clearLine()
method adds to the internal list of pending action an\naction that clears current line of the associated stream
in a specified\ndirection identified by dir
.\nCall rl.commit()
to see the effect of this method, unless autoCommit: true
\nwas passed to the constructor.
The rl.clearScreenDown()
method adds to the internal list of pending action an\naction that clears the associated stream from the current position of the\ncursor down.\nCall rl.commit()
to see the effect of this method, unless autoCommit: true
\nwas passed to the constructor.
The rl.commit()
method sends all the pending actions to the associated\nstream
and clears the internal list of pending actions.
The rl.cursorTo()
method adds to the internal list of pending action an action\nthat moves cursor to the specified position in the associated stream
.\nCall rl.commit()
to see the effect of this method, unless autoCommit: true
\nwas passed to the constructor.
The rl.moveCursor()
method adds to the internal list of pending action an\naction that moves the cursor relative to its current position in the\nassociated stream
.\nCall rl.commit()
to see the effect of this method, unless autoCommit: true
\nwas passed to the constructor.
The rl.rollback
methods clears the internal list of pending actions without\nsending it to the associated stream
.
The readlinePromises.createInterface()
method creates a new readlinePromises.Interface
\ninstance.
const readlinePromises = require('node:readline/promises');\nconst rl = readlinePromises.createInterface({\n input: process.stdin,\n output: process.stdout,\n});\n
\nOnce the readlinePromises.Interface
instance is created, the most common case\nis to listen for the 'line'
event:
rl.on('line', (line) => {\n console.log(`Received: ${line}`);\n});\n
\nIf terminal
is true
for this instance then the output
stream will get\nthe best compatibility if it defines an output.columns
property and emits\na 'resize'
event on the output
if or when the columns ever change\n(process.stdout
does this automatically when it is a TTY).
The completer
function takes the current line entered by the user\nas an argument, and returns an Array
with 2 entries:
Array
with matching entries for the completion.For instance: [[substr1, substr2, ...], originalsubstring]
.
function completer(line) {\n const completions = '.help .error .exit .quit .q'.split(' ');\n const hits = completions.filter((c) => c.startsWith(line));\n // Show all completions if none found\n return [hits.length ? hits : completions, line];\n}\n
\nThe completer
function can also return a <Promise>, or be asynchronous:
async function completer(linePartial) {\n await someAsyncWork();\n return [['123'], linePartial];\n}\n
",
"type": "module",
"displayName": "Use of the `completer` function"
}
]
}
],
"type": "module",
"displayName": "Promises API"
},
{
"textRaw": "Callback API",
"name": "callback_api",
"meta": {
"added": [
"v0.1.104"
],
"changes": []
},
"classes": [
{
"textRaw": "Class: `readline.Interface`",
"type": "class",
"name": "readline.Interface",
"meta": {
"added": [
"v0.1.104"
],
"changes": [
{
"version": "v17.0.0",
"pr-url": "https://github.com/nodejs/node/pull/37947",
"description": "The class `readline.Interface` now inherits from `Interface`."
}
]
},
"desc": "Instances of the readline.Interface
class are constructed using the\nreadline.createInterface()
method. Every instance is associated with a\nsingle input
Readable stream and a single output
Writable stream.\nThe output
stream is used to print prompts for user input that arrives on,\nand is read from, the input
stream.
The rl.question()
method displays the query
by writing it to the output
,\nwaits for user input to be provided on input
, then invokes the callback
\nfunction passing the provided input as the first argument.
When called, rl.question()
will resume the input
stream if it has been\npaused.
If the readline.Interface
was created with output
set to null
or\nundefined
the query
is not written.
The callback
function passed to rl.question()
does not follow the typical\npattern of accepting an Error
object or null
as the first argument.\nThe callback
is called with the provided answer as the only argument.
An error will be thrown if calling rl.question()
after rl.close()
.
Example usage:
\nrl.question('What is your favorite food? ', (answer) => {\n console.log(`Oh, so your favorite food is ${answer}`);\n});\n
\nUsing an AbortController
to cancel a question.
const ac = new AbortController();\nconst signal = ac.signal;\n\nrl.question('What is your favorite food? ', { signal }, (answer) => {\n console.log(`Oh, so your favorite food is ${answer}`);\n});\n\nsignal.addEventListener('abort', () => {\n console.log('The food question timed out');\n}, { once: true });\n\nsetTimeout(() => ac.abort(), 10000);\n
"
}
]
}
],
"methods": [
{
"textRaw": "`readline.clearLine(stream, dir[, callback])`",
"type": "method",
"name": "clearLine",
"meta": {
"added": [
"v0.7.7"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v12.7.0",
"pr-url": "https://github.com/nodejs/node/pull/28674",
"description": "The stream's write() callback and return value are exposed."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `false` if `stream` wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`.",
"name": "return",
"type": "boolean",
"desc": "`false` if `stream` wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`."
},
"params": [
{
"textRaw": "`stream` {stream.Writable}",
"name": "stream",
"type": "stream.Writable"
},
{
"textRaw": "`dir` {number}",
"name": "dir",
"type": "number",
"options": [
{
"textRaw": "`-1`: to the left from cursor",
"name": "-1",
"desc": "to the left from cursor"
},
{
"textRaw": "`1`: to the right from cursor",
"name": "1",
"desc": "to the right from cursor"
},
{
"textRaw": "`0`: the entire line",
"name": "0",
"desc": "the entire line"
}
]
},
{
"textRaw": "`callback` {Function} Invoked once the operation completes.",
"name": "callback",
"type": "Function",
"desc": "Invoked once the operation completes."
}
]
}
],
"desc": "The readline.clearLine()
method clears current line of given TTY stream\nin a specified direction identified by dir
.
The readline.clearScreenDown()
method clears the given TTY stream from\nthe current position of the cursor down.
The readline.createInterface()
method creates a new readline.Interface
\ninstance.
const readline = require('node:readline');\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout,\n});\n
\nOnce the readline.Interface
instance is created, the most common case is to\nlisten for the 'line'
event:
rl.on('line', (line) => {\n console.log(`Received: ${line}`);\n});\n
\nIf terminal
is true
for this instance then the output
stream will get\nthe best compatibility if it defines an output.columns
property and emits\na 'resize'
event on the output
if or when the columns ever change\n(process.stdout
does this automatically when it is a TTY).
When creating a readline.Interface
using stdin
as input, the program\nwill not terminate until it receives an EOF character. To exit without\nwaiting for user input, call process.stdin.unref()
.
The completer
function takes the current line entered by the user\nas an argument, and returns an Array
with 2 entries:
Array
with matching entries for the completion.For instance: [[substr1, substr2, ...], originalsubstring]
.
function completer(line) {\n const completions = '.help .error .exit .quit .q'.split(' ');\n const hits = completions.filter((c) => c.startsWith(line));\n // Show all completions if none found\n return [hits.length ? hits : completions, line];\n}\n
\nThe completer
function can be called asynchronously if it accepts two\narguments:
function completer(linePartial, callback) {\n callback(null, [['123'], linePartial]);\n}\n
",
"type": "module",
"displayName": "Use of the `completer` function"
}
]
},
{
"textRaw": "`readline.cursorTo(stream, x[, y][, callback])`",
"type": "method",
"name": "cursorTo",
"meta": {
"added": [
"v0.7.7"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v12.7.0",
"pr-url": "https://github.com/nodejs/node/pull/28674",
"description": "The stream's write() callback and return value are exposed."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `false` if `stream` wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`.",
"name": "return",
"type": "boolean",
"desc": "`false` if `stream` wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`."
},
"params": [
{
"textRaw": "`stream` {stream.Writable}",
"name": "stream",
"type": "stream.Writable"
},
{
"textRaw": "`x` {number}",
"name": "x",
"type": "number"
},
{
"textRaw": "`y` {number}",
"name": "y",
"type": "number"
},
{
"textRaw": "`callback` {Function} Invoked once the operation completes.",
"name": "callback",
"type": "Function",
"desc": "Invoked once the operation completes."
}
]
}
],
"desc": "The readline.cursorTo()
method moves cursor to the specified position in a\ngiven TTY stream
.
The readline.moveCursor()
method moves the cursor relative to its current\nposition in a given TTY stream
.
Keybindings | \nDescription | \nNotes | \n
---|---|---|
Ctrl+Shift+Backspace | \nDelete line left | \nDoesn't work on Linux, Mac and Windows | \n
Ctrl+Shift+Delete | \nDelete line right | \nDoesn't work on Mac | \n
Ctrl+C | \nEmit SIGINT or close the readline instance | \n \n |
Ctrl+H | \nDelete left | \n\n |
Ctrl+D | \nDelete right or close the readline instance in case the current line is empty / EOF | \nDoesn't work on Windows | \n
Ctrl+U | \nDelete from the current position to the line start | \n\n |
Ctrl+K | \nDelete from the current position to the end of line | \n\n |
Ctrl+Y | \nYank (Recall) the previously deleted text | \nOnly works with text deleted by Ctrl+U or Ctrl+K | \n
Meta+Y | \nCycle among previously deleted texts | \nOnly available when the last keystroke is Ctrl+Y or Meta+Y | \n
Ctrl+A | \nGo to start of line | \n\n |
Ctrl+E | \nGo to end of line | \n\n |
Ctrl+B | \nBack one character | \n\n |
Ctrl+F | \nForward one character | \n\n |
Ctrl+L | \nClear screen | \n\n |
Ctrl+N | \nNext history item | \n\n |
Ctrl+P | \nPrevious history item | \n\n |
Ctrl+- | \nUndo previous change | \nAny keystroke that emits key code 0x1F will do this action.\n In many terminals, for example xterm ,\n this is bound to Ctrl+-. | \n
Ctrl+6 | \nRedo previous change | \nMany terminals don't have a default redo keystroke.\n We choose key code 0x1E to perform redo.\n In xterm , it is bound to Ctrl+6\n by default. | \n
Ctrl+Z | \nMoves running process into background. Type\n fg and press Enter\n to return. | \n Doesn't work on Windows | \n
Ctrl+W or Ctrl\n +Backspace | \nDelete backward to a word boundary | \nCtrl+Backspace Doesn't\n work on Linux, Mac and Windows | \n
Ctrl+Delete | \nDelete forward to a word boundary | \nDoesn't work on Mac | \n
Ctrl+Left arrow or\n Meta+B | \nWord left | \nCtrl+Left arrow Doesn't work\n on Mac | \n
Ctrl+Right arrow or\n Meta+F | \nWord right | \nCtrl+Right arrow Doesn't work\n on Mac | \n
Meta+D or Meta\n +Delete | \nDelete word right | \nMeta+Delete Doesn't work\n on windows | \n
Meta+Backspace | \nDelete word left | \nDoesn't work on Mac | \n
The readline.emitKeypressEvents()
method causes the given Readable\nstream to begin emitting 'keypress'
events corresponding to received input.
Optionally, interface
specifies a readline.Interface
instance for which\nautocompletion is disabled when copy-pasted input is detected.
If the stream
is a TTY, then it must be in raw mode.
This is automatically called by any readline instance on its input
if the\ninput
is a terminal. Closing the readline
instance does not stop\nthe input
from emitting 'keypress'
events.
readline.emitKeypressEvents(process.stdin);\nif (process.stdin.isTTY)\n process.stdin.setRawMode(true);\n
\nThe following example illustrates the use of readline.Interface
class to\nimplement a small command-line interface:
const readline = require('node:readline');\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout,\n prompt: 'OHAI> ',\n});\n\nrl.prompt();\n\nrl.on('line', (line) => {\n switch (line.trim()) {\n case 'hello':\n console.log('world!');\n break;\n default:\n console.log(`Say what? I might have heard '${line.trim()}'`);\n break;\n }\n rl.prompt();\n}).on('close', () => {\n console.log('Have a great day!');\n process.exit(0);\n});\n
\nA common use case for readline
is to consume an input file one line at a\ntime. The easiest way to do so is leveraging the fs.ReadStream
API as\nwell as a for await...of
loop:
const fs = require('node:fs');\nconst readline = require('node:readline');\n\nasync function processLineByLine() {\n const fileStream = fs.createReadStream('input.txt');\n\n const rl = readline.createInterface({\n input: fileStream,\n crlfDelay: Infinity,\n });\n // Note: we use the crlfDelay option to recognize all instances of CR LF\n // ('\\r\\n') in input.txt as a single line break.\n\n for await (const line of rl) {\n // Each line in input.txt will be successively available here as `line`.\n console.log(`Line from file: ${line}`);\n }\n}\n\nprocessLineByLine();\n
\nAlternatively, one could use the 'line'
event:
const fs = require('node:fs');\nconst readline = require('node:readline');\n\nconst rl = readline.createInterface({\n input: fs.createReadStream('sample.txt'),\n crlfDelay: Infinity,\n});\n\nrl.on('line', (line) => {\n console.log(`Line from file: ${line}`);\n});\n
\nCurrently, for await...of
loop can be a bit slower. If async
/ await
\nflow and speed are both essential, a mixed approach can be applied:
const { once } = require('node:events');\nconst { createReadStream } = require('node:fs');\nconst { createInterface } = require('node:readline');\n\n(async function processLineByLine() {\n try {\n const rl = createInterface({\n input: createReadStream('big-file.txt'),\n crlfDelay: Infinity,\n });\n\n rl.on('line', (line) => {\n // Process the line.\n });\n\n await once(rl, 'close');\n\n console.log('File processed.');\n } catch (err) {\n console.error(err);\n }\n})();\n
"
}
],
"type": "module",
"displayName": "Readline",
"source": "doc/api/readline.md"
},
{
"textRaw": "REPL",
"name": "repl",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/repl.js
\nThe node:repl
module provides a Read-Eval-Print-Loop (REPL) implementation\nthat is available both as a standalone program or includible in other\napplications. It can be accessed using:
const repl = require('node:repl');\n
",
"modules": [
{
"textRaw": "Design and features",
"name": "design_and_features",
"desc": "The node:repl
module exports the repl.REPLServer
class. While running,\ninstances of repl.REPLServer
will accept individual lines of user input,\nevaluate those according to a user-defined evaluation function, then output the\nresult. Input and output may be from stdin
and stdout
, respectively, or may\nbe connected to any Node.js stream.
Instances of repl.REPLServer
support automatic completion of inputs,\ncompletion preview, simplistic Emacs-style line editing, multi-line inputs,\nZSH-like reverse-i-search, ZSH-like substring-based history search,\nANSI-styled output, saving and restoring current REPL session state, error\nrecovery, and customizable evaluation functions. Terminals that do not support\nANSI styles and Emacs-style line editing automatically fall back to a limited\nfeature set.
The following special commands are supported by all REPL instances:
\n.break
: When in the process of inputting a multi-line expression, enter\nthe .break
command (or press Ctrl+C) to abort\nfurther input or processing of that expression..clear
: Resets the REPL context
to an empty object and clears any\nmulti-line expression being input..exit
: Close the I/O stream, causing the REPL to exit..help
: Show this list of special commands..save
: Save the current REPL session to a file:\n> .save ./file/to/save.js
.load
: Load a file into the current REPL session.\n> .load ./file/to/load.js
.editor
: Enter editor mode (Ctrl+D to\nfinish, Ctrl+C to cancel).> .editor\n// Entering editor mode (^D to finish, ^C to cancel)\nfunction welcome(name) {\n return `Hello ${name}!`;\n}\n\nwelcome('Node.js User');\n\n// ^D\n'Hello Node.js User!'\n>\n
\nThe following key combinations in the REPL have these special effects:
\n.break
command.\nWhen pressed twice on a blank line, has the same effect as the .exit
\ncommand..exit
command.For key bindings related to the reverse-i-search, see reverse-i-search
.\nFor all other key bindings, see TTY keybindings.
By default, all instances of repl.REPLServer
use an evaluation function\nthat evaluates JavaScript expressions and provides access to Node.js built-in\nmodules. This default behavior can be overridden by passing in an alternative\nevaluation function when the repl.REPLServer
instance is created.
The default evaluator supports direct evaluation of JavaScript expressions:
\n> 1 + 1\n2\n> const m = 2\nundefined\n> m + 1\n3\n
\nUnless otherwise scoped within blocks or functions, variables declared\neither implicitly or using the const
, let
, or var
keywords\nare declared at the global scope.
The default evaluator provides access to any variables that exist in the global\nscope. It is possible to expose a variable to the REPL explicitly by assigning\nit to the context
object associated with each REPLServer
:
const repl = require('node:repl');\nconst msg = 'message';\n\nrepl.start('> ').context.m = msg;\n
\nProperties in the context
object appear as local within the REPL:
$ node repl_test.js\n> m\n'message'\n
\nContext properties are not read-only by default. To specify read-only globals,\ncontext properties must be defined using Object.defineProperty()
:
const repl = require('node:repl');\nconst msg = 'message';\n\nconst r = repl.start('> ');\nObject.defineProperty(r.context, 'm', {\n configurable: false,\n enumerable: true,\n value: msg,\n});\n
",
"type": "module",
"displayName": "Global and local scope"
},
{
"textRaw": "Accessing core Node.js modules",
"name": "accessing_core_node.js_modules",
"desc": "The default evaluator will automatically load Node.js core modules into the\nREPL environment when used. For instance, unless otherwise declared as a\nglobal or scoped variable, the input fs
will be evaluated on-demand as\nglobal.fs = require('node:fs')
.
> fs.createReadStream('./some/file');\n
",
"type": "module",
"displayName": "Accessing core Node.js modules"
},
{
"textRaw": "Global uncaught exceptions",
"name": "global_uncaught_exceptions",
"meta": {
"changes": [
{
"version": "v12.3.0",
"pr-url": "https://github.com/nodejs/node/pull/27151",
"description": "The `'uncaughtException'` event is from now on triggered if the repl is used as standalone program."
}
]
},
"desc": "The REPL uses the domain
module to catch all uncaught exceptions for that\nREPL session.
This use of the domain
module in the REPL has these side effects:
Uncaught exceptions only emit the 'uncaughtException'
event in the\nstandalone REPL. Adding a listener for this event in a REPL within\nanother Node.js program results in ERR_INVALID_REPL_INPUT
.
const r = repl.start();\n\nr.write('process.on(\"uncaughtException\", () => console.log(\"Foobar\"));\\n');\n// Output stream includes:\n// TypeError [ERR_INVALID_REPL_INPUT]: Listeners for `uncaughtException`\n// cannot be used in the REPL\n\nr.close();\n
\nTrying to use process.setUncaughtExceptionCaptureCallback()
throws\nan ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE
error.
The default evaluator will, by default, assign the result of the most recently\nevaluated expression to the special variable _
(underscore).\nExplicitly setting _
to a value will disable this behavior.
> [ 'a', 'b', 'c' ]\n[ 'a', 'b', 'c' ]\n> _.length\n3\n> _ += 1\nExpression assignment to _ now disabled.\n4\n> 1 + 1\n2\n> _\n4\n
\nSimilarly, _error
will refer to the last seen error, if there was any.\nExplicitly setting _error
to a value will disable this behavior.
> throw new Error('foo');\nUncaught Error: foo\n> _error.message\n'foo'\n
",
"type": "module",
"displayName": "Assignment of the `_` (underscore) variable"
},
{
"textRaw": "`await` keyword",
"name": "`await`_keyword",
"desc": "Support for the await
keyword is enabled at the top level.
> await Promise.resolve(123)\n123\n> await Promise.reject(new Error('REPL await'))\nUncaught Error: REPL await\n at REPL2:1:54\n> const timeout = util.promisify(setTimeout);\nundefined\n> const old = Date.now(); await timeout(1000); console.log(Date.now() - old);\n1002\nundefined\n
\nOne known limitation of using the await
keyword in the REPL is that\nit will invalidate the lexical scoping of the const
and let
\nkeywords.
For example:
\n> const m = await Promise.resolve(123)\nundefined\n> m\n123\n> const m = await Promise.resolve(234)\nundefined\n> m\n234\n
\n--no-experimental-repl-await
shall disable top-level await in REPL.
The REPL supports bi-directional reverse-i-search similar to ZSH. It is\ntriggered with Ctrl+R to search backward\nand Ctrl+S to search forwards.
\nDuplicated history entries will be skipped.
\nEntries are accepted as soon as any key is pressed that doesn't correspond\nwith the reverse search. Cancelling is possible by pressing Esc\nor Ctrl+C.
\nChanging the direction immediately searches for the next entry in the expected\ndirection from the current position on.
", "type": "module", "displayName": "Reverse-i-search" }, { "textRaw": "Custom evaluation functions", "name": "custom_evaluation_functions", "desc": "When a new repl.REPLServer
is created, a custom evaluation function may be\nprovided. This can be used, for instance, to implement fully customized REPL\napplications.
The following illustrates a hypothetical example of a REPL that performs\ntranslation of text from one language to another:
\nconst repl = require('node:repl');\nconst { Translator } = require('translator');\n\nconst myTranslator = new Translator('en', 'fr');\n\nfunction myEval(cmd, context, filename, callback) {\n callback(null, myTranslator.translate(cmd));\n}\n\nrepl.start({ prompt: '> ', eval: myEval });\n
",
"modules": [
{
"textRaw": "Recoverable errors",
"name": "recoverable_errors",
"desc": "At the REPL prompt, pressing Enter sends the current line of input to\nthe eval
function. In order to support multi-line input, the eval
function\ncan return an instance of repl.Recoverable
to the provided callback function:
function myEval(cmd, context, filename, callback) {\n let result;\n try {\n result = vm.runInThisContext(cmd);\n } catch (e) {\n if (isRecoverableError(e)) {\n return callback(new repl.Recoverable(e));\n }\n }\n callback(null, result);\n}\n\nfunction isRecoverableError(error) {\n if (error.name === 'SyntaxError') {\n return /^(Unexpected end of input|Unexpected token)/.test(error.message);\n }\n return false;\n}\n
",
"type": "module",
"displayName": "Recoverable errors"
}
],
"type": "module",
"displayName": "Custom evaluation functions"
},
{
"textRaw": "Customizing REPL output",
"name": "customizing_repl_output",
"desc": "By default, repl.REPLServer
instances format output using the\nutil.inspect()
method before writing the output to the provided Writable
\nstream (process.stdout
by default). The showProxy
inspection option is set\nto true by default and the colors
option is set to true depending on the\nREPL's useColors
option.
The useColors
boolean option can be specified at construction to instruct the\ndefault writer to use ANSI style codes to colorize the output from the\nutil.inspect()
method.
If the REPL is run as standalone program, it is also possible to change the\nREPL's inspection defaults from inside the REPL by using the\ninspect.replDefaults
property which mirrors the defaultOptions
from\nutil.inspect()
.
> util.inspect.replDefaults.compact = false;\nfalse\n> [1]\n[\n 1\n]\n>\n
\nTo fully customize the output of a repl.REPLServer
instance pass in a new\nfunction for the writer
option on construction. The following example, for\ninstance, simply converts any input text to upper case:
const repl = require('node:repl');\n\nconst r = repl.start({ prompt: '> ', eval: myEval, writer: myWriter });\n\nfunction myEval(cmd, context, filename, callback) {\n callback(null, cmd);\n}\n\nfunction myWriter(output) {\n return output.toUpperCase();\n}\n
",
"type": "module",
"displayName": "Customizing REPL output"
}
],
"type": "module",
"displayName": "Design and features"
},
{
"textRaw": "The Node.js REPL",
"name": "the_node.js_repl",
"desc": "Node.js itself uses the node:repl
module to provide its own interactive\ninterface for executing JavaScript. This can be used by executing the Node.js\nbinary without passing any arguments (or by passing the -i
argument):
$ node\n> const a = [1, 2, 3];\nundefined\n> a\n[ 1, 2, 3 ]\n> a.forEach((v) => {\n... console.log(v);\n... });\n1\n2\n3\n
",
"modules": [
{
"textRaw": "Environment variable options",
"name": "environment_variable_options",
"desc": "Various behaviors of the Node.js REPL can be customized using the following\nenvironment variables:
\nNODE_REPL_HISTORY
: When a valid path is given, persistent REPL history\nwill be saved to the specified file rather than .node_repl_history
in the\nuser's home directory. Setting this value to ''
(an empty string) will\ndisable persistent REPL history. Whitespace will be trimmed from the value.\nOn Windows platforms environment variables with empty values are invalid so\nset this variable to one or more spaces to disable persistent REPL history.NODE_REPL_HISTORY_SIZE
: Controls how many lines of history will be\npersisted if history is available. Must be a positive number.\nDefault: 1000
.NODE_REPL_MODE
: May be either 'sloppy'
or 'strict'
. Default:\n'sloppy'
, which will allow non-strict mode code to be run.By default, the Node.js REPL will persist history between node
REPL sessions\nby saving inputs to a .node_repl_history
file located in the user's home\ndirectory. This can be disabled by setting the environment variable\nNODE_REPL_HISTORY=''
.
For advanced line-editors, start Node.js with the environment variable\nNODE_NO_READLINE=1
. This will start the main and debugger REPL in canonical\nterminal settings, which will allow use with rlwrap
.
For example, the following can be added to a .bashrc
file:
alias node=\"env NODE_NO_READLINE=1 rlwrap node\"\n
",
"type": "module",
"displayName": "Using the Node.js REPL with advanced line-editors"
},
{
"textRaw": "Starting multiple REPL instances against a single running instance",
"name": "starting_multiple_repl_instances_against_a_single_running_instance",
"desc": "It is possible to create and run multiple REPL instances against a single\nrunning instance of Node.js that share a single global
object but have\nseparate I/O interfaces.
The following example, for instance, provides separate REPLs on stdin
, a Unix\nsocket, and a TCP socket:
const net = require('node:net');\nconst repl = require('node:repl');\nlet connections = 0;\n\nrepl.start({\n prompt: 'Node.js via stdin> ',\n input: process.stdin,\n output: process.stdout,\n});\n\nnet.createServer((socket) => {\n connections += 1;\n repl.start({\n prompt: 'Node.js via Unix socket> ',\n input: socket,\n output: socket,\n }).on('exit', () => {\n socket.end();\n });\n}).listen('/tmp/node-repl-sock');\n\nnet.createServer((socket) => {\n connections += 1;\n repl.start({\n prompt: 'Node.js via TCP socket> ',\n input: socket,\n output: socket,\n }).on('exit', () => {\n socket.end();\n });\n}).listen(5001);\n
\nRunning this application from the command line will start a REPL on stdin.\nOther REPL clients may connect through the Unix socket or TCP socket. telnet
,\nfor instance, is useful for connecting to TCP sockets, while socat
can be used\nto connect to both Unix and TCP sockets.
By starting a REPL from a Unix socket-based server instead of stdin, it is\npossible to connect to a long-running Node.js process without restarting it.
\nFor an example of running a \"full-featured\" (terminal
) REPL over\na net.Server
and net.Socket
instance, see:\nhttps://gist.github.com/TooTallNate/2209310.
For an example of running a REPL instance over curl(1)
, see:\nhttps://gist.github.com/TooTallNate/2053342.
options
<Object> | <string> See repl.start()
Instances of repl.REPLServer
are created using the repl.start()
method\nor directly using the JavaScript new
keyword.
const repl = require('node:repl');\n\nconst options = { useColors: true };\n\nconst firstInstance = repl.start(options);\nconst secondInstance = new repl.REPLServer(options);\n
",
"events": [
{
"textRaw": "Event: `'exit'`",
"type": "event",
"name": "exit",
"meta": {
"added": [
"v0.7.7"
],
"changes": []
},
"params": [],
"desc": "The 'exit'
event is emitted when the REPL is exited either by receiving the\n.exit
command as input, the user pressing Ctrl+C twice\nto signal SIGINT
,\nor by pressing Ctrl+D to signal 'end'
on the input\nstream. The listener\ncallback is invoked without any arguments.
replServer.on('exit', () => {\n console.log('Received \"exit\" event from repl!');\n process.exit();\n});\n
"
},
{
"textRaw": "Event: `'reset'`",
"type": "event",
"name": "reset",
"meta": {
"added": [
"v0.11.0"
],
"changes": []
},
"params": [],
"desc": "The 'reset'
event is emitted when the REPL's context is reset. This occurs\nwhenever the .clear
command is received as input unless the REPL is using\nthe default evaluator and the repl.REPLServer
instance was created with the\nuseGlobal
option set to true
. The listener callback will be called with a\nreference to the context
object as the only argument.
This can be used primarily to re-initialize REPL context to some pre-defined\nstate:
\nconst repl = require('node:repl');\n\nfunction initializeContext(context) {\n context.m = 'test';\n}\n\nconst r = repl.start({ prompt: '> ' });\ninitializeContext(r.context);\n\nr.on('reset', initializeContext);\n
\nWhen this code is executed, the global 'm'
variable can be modified but then\nreset to its initial value using the .clear
command:
$ ./node example.js\n> m\n'test'\n> m = 1\n1\n> m\n1\n> .clear\nClearing context...\n> m\n'test'\n>\n
"
}
],
"methods": [
{
"textRaw": "`replServer.defineCommand(keyword, cmd)`",
"type": "method",
"name": "defineCommand",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`keyword` {string} The command keyword (_without_ a leading `.` character).",
"name": "keyword",
"type": "string",
"desc": "The command keyword (_without_ a leading `.` character)."
},
{
"textRaw": "`cmd` {Object|Function} The function to invoke when the command is processed.",
"name": "cmd",
"type": "Object|Function",
"desc": "The function to invoke when the command is processed."
}
]
}
],
"desc": "The replServer.defineCommand()
method is used to add new .
-prefixed commands\nto the REPL instance. Such commands are invoked by typing a .
followed by the\nkeyword
. The cmd
is either a Function
or an Object
with the following\nproperties:
help
<string> Help text to be displayed when .help
is entered (Optional).action
<Function> The function to execute, optionally accepting a single\nstring argument.The following example shows two new commands added to the REPL instance:
\nconst repl = require('node:repl');\n\nconst replServer = repl.start({ prompt: '> ' });\nreplServer.defineCommand('sayhello', {\n help: 'Say hello',\n action(name) {\n this.clearBufferedCommand();\n console.log(`Hello, ${name}!`);\n this.displayPrompt();\n },\n});\nreplServer.defineCommand('saybye', function saybye() {\n console.log('Goodbye!');\n this.close();\n});\n
\nThe new commands can then be used from within the REPL instance:
\n> .sayhello Node.js User\nHello, Node.js User!\n> .saybye\nGoodbye!\n
"
},
{
"textRaw": "`replServer.displayPrompt([preserveCursor])`",
"type": "method",
"name": "displayPrompt",
"meta": {
"added": [
"v0.1.91"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`preserveCursor` {boolean}",
"name": "preserveCursor",
"type": "boolean"
}
]
}
],
"desc": "The replServer.displayPrompt()
method readies the REPL instance for input\nfrom the user, printing the configured prompt
to a new line in the output
\nand resuming the input
to accept new input.
When multi-line input is being entered, an ellipsis is printed rather than the\n'prompt'.
\nWhen preserveCursor
is true
, the cursor placement will not be reset to 0
.
The replServer.displayPrompt
method is primarily intended to be called from\nwithin the action function for commands registered using the\nreplServer.defineCommand()
method.
The replServer.clearBufferedCommand()
method clears any command that has been\nbuffered but not yet executed. This method is primarily intended to be\ncalled from within the action function for commands registered using the\nreplServer.defineCommand()
method.
An internal method used to parse and execute REPLServer
keywords.\nReturns true
if keyword
is a valid keyword, otherwise false
.
Initializes a history log file for the REPL instance. When executing the\nNode.js binary and using the command-line REPL, a history file is initialized\nby default. However, this is not the case when creating a REPL\nprogrammatically. Use this method to initialize a history log file when working\nwith REPL instances programmatically.
" } ] } ], "properties": [ { "textRaw": "`builtinModules` {string\\[]}", "type": "string\\[]", "name": "builtinModules", "meta": { "added": [ "v14.5.0" ], "changes": [] }, "desc": "A list of the names of all Node.js modules, e.g., 'http'
.
The repl.start()
method creates and starts a repl.REPLServer
instance.
If options
is a string, then it specifies the input prompt:
const repl = require('node:repl');\n\n// a Unix style prompt\nrepl.start('$ ');\n
"
}
],
"type": "module",
"displayName": "REPL",
"source": "doc/api/repl.md"
},
{
"textRaw": "Single executable applications",
"name": "single_executable_applications",
"introduced_in": "v19.7.0",
"meta": {
"added": [
"v19.7.0",
"v18.16.0"
],
"changes": [
{
"version": "v20.6.0",
"pr-url": "https://github.com/nodejs/node/pull/46824",
"description": "Added support for \"useSnapshot\"."
},
{
"version": "v20.6.0",
"pr-url": "https://github.com/nodejs/node/pull/48191",
"description": "Added support for \"useCodeCache\"."
}
]
},
"stability": 1,
"stabilityText": ".1 - Active development",
"desc": "Source Code: src/node_sea.cc
\nThis feature allows the distribution of a Node.js application conveniently to a\nsystem that does not have Node.js installed.
\nNode.js supports the creation of single executable applications by allowing\nthe injection of a blob prepared by Node.js, which can contain a bundled script,\ninto the node
binary. During start up, the program checks if anything has been\ninjected. If the blob is found, it executes the script in the blob. Otherwise\nNode.js operates as it normally does.
The single executable application feature currently only supports running a\nsingle embedded script using the CommonJS module system.
\nUsers can create a single executable application from their bundled script\nwith the node
binary itself and any tool which can inject resources into the\nbinary.
Here are the steps for creating a single executable application using one such\ntool, postject:
\nCreate a JavaScript file:
\necho 'console.log(`Hello, ${process.argv[2]}!`);' > hello.js\n
\nCreate a configuration file building a blob that can be injected into the\nsingle executable application (see\nGenerating single executable preparation blobs for details):
\necho '{ \"main\": \"hello.js\", \"output\": \"sea-prep.blob\" }' > sea-config.json\n
\nGenerate the blob to be injected:
\nnode --experimental-sea-config sea-config.json\n
\nCreate a copy of the node
executable and name it according to your needs:
cp $(command -v node) hello\n
\nnode -e \"require('fs').copyFileSync(process.execPath, 'hello.exe')\"\n
\nThe .exe
extension is necessary.
Remove the signature of the binary (macOS and Windows only):
\ncodesign --remove-signature hello\n
\nsigntool can be used from the installed Windows SDK. If this step is\nskipped, ignore any signature-related warning from postject.
\nsigntool remove /s hello.exe\n
\nInject the blob into the copied binary by running postject
with\nthe following options:
hello
/ hello.exe
- The name of the copy of the node
executable\ncreated in step 4.NODE_SEA_BLOB
- The name of the resource / note / section in the binary\nwhere the contents of the blob will be stored.sea-prep.blob
- The name of the blob created in step 1.--sentinel-fuse NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2
- The\nfuse used by the Node.js project to detect if a file has been injected.--macho-segment-name NODE_SEA
(only needed on macOS) - The name of the\nsegment in the binary where the contents of the blob will be\nstored.To summarize, here is the required command for each platform:
\nOn Linux:
\nnpx postject hello NODE_SEA_BLOB sea-prep.blob \\\n --sentinel-fuse NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2\n
\nOn Windows - PowerShell:
\nnpx postject hello.exe NODE_SEA_BLOB sea-prep.blob `\n --sentinel-fuse NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2\n
\nOn Windows - Command Prompt:
\nnpx postject hello.exe NODE_SEA_BLOB sea-prep.blob ^\n --sentinel-fuse NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2\n
\nOn macOS:
\nnpx postject hello NODE_SEA_BLOB sea-prep.blob \\\n --sentinel-fuse NODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2 \\\n --macho-segment-name NODE_SEA\n
\nSign the binary (macOS and Windows only):
\ncodesign --sign - hello\n
\nA certificate needs to be present for this to work. However, the unsigned\nbinary would still be runnable.
\nsigntool sign /fd SHA256 hello.exe\n
\nRun the binary:
\n$ ./hello world\nHello, world!\n
\n$ .\\hello.exe world\nHello, world!\n
\nSingle executable preparation blobs that are injected into the application can\nbe generated using the --experimental-sea-config
flag of the Node.js binary\nthat will be used to build the single executable. It takes a path to a\nconfiguration file in JSON format. If the path passed to it isn't absolute,\nNode.js will use the path relative to the current working directory.
The configuration currently reads the following top-level fields:
\n{\n \"main\": \"/path/to/bundled/script.js\",\n \"output\": \"/path/to/write/the/generated/blob.blob\",\n \"disableExperimentalSEAWarning\": true, // Default: false\n \"useSnapshot\": false, // Default: false\n \"useCodeCache\": true, // Default: false\n \"assets\": { // Optional\n \"a.dat\": \"/path/to/a.dat\",\n \"b.txt\": \"/path/to/b.txt\"\n }\n}\n
\nIf the paths are not absolute, Node.js will use the path relative to the\ncurrent working directory. The version of the Node.js binary used to produce\nthe blob must be the same as the one to which the blob will be injected.
", "modules": [ { "textRaw": "Assets", "name": "assets", "desc": "Users can include assets by adding a key-path dictionary to the configuration\nas the assets
field. At build time, Node.js would read the assets from the\nspecified paths and bundle them into the preparation blob. In the generated\nexecutable, users can retrieve the assets using the sea.getAsset()
and\nsea.getAssetAsBlob()
APIs.
{\n \"main\": \"/path/to/bundled/script.js\",\n \"output\": \"/path/to/write/the/generated/blob.blob\",\n \"assets\": {\n \"a.jpg\": \"/path/to/a.jpg\",\n \"b.txt\": \"/path/to/b.txt\"\n }\n}\n
\nThe single-executable application can access the assets as follows:
\nconst { getAsset } = require('node:sea');\n// Returns a copy of the data in an ArrayBuffer.\nconst image = getAsset('a.jpg');\n// Returns a string decoded from the asset as UTF8.\nconst text = getAsset('b.txt', 'utf8');\n// Returns a Blob containing the asset.\nconst blob = getAssetAsBlob('a.jpg');\n// Returns an ArrayBuffer containing the raw asset without copying.\nconst raw = getRawAsset('a.jpg');\n
\nSee documentation of the sea.getAsset()
and sea.getAssetAsBlob()
\nAPIs for more information.
The useSnapshot
field can be used to enable startup snapshot support. In this\ncase the main
script would not be when the final executable is launched.\nInstead, it would be run when the single executable application preparation\nblob is generated on the building machine. The generated preparation blob would\nthen include a snapshot capturing the states initialized by the main
script.\nThe final executable with the preparation blob injected would deserialize\nthe snapshot at run time.
When useSnapshot
is true, the main script must invoke the\nv8.startupSnapshot.setDeserializeMainFunction()
API to configure code\nthat needs to be run when the final executable is launched by the users.
The typical pattern for an application to use snapshot in a single executable\napplication is:
\nv8.startupSnapshot.setDeserializeMainFunction()
. This function will be\ncompiled and serialized into the snapshot, but not invoked at build time.The general constraints of the startup snapshot scripts also apply to the main\nscript when it's used to build snapshot for the single executable application,\nand the main script can use the v8.startupSnapshot
API to adapt to\nthese constraints. See\ndocumentation about startup snapshot support in Node.js.
When useCodeCache
is set to true
in the configuration, during the generation\nof the single executable preparation blob, Node.js will compile the main
\nscript to generate the V8 code cache. The generated code cache would be part of\nthe preparation blob and get injected into the final executable. When the single\nexecutable application is launched, instead of compiling the main
script from\nscratch, Node.js would use the code cache to speed up the compilation, then\nexecute the script, which would improve the startup performance.
Note: import()
does not work when useCodeCache
is true
.
The node:sea
builtin allows interaction with the single-executable application\nfrom the JavaScript main script embedded into the executable.
require()
in the injected main script is not the same as the require()
\navailable to modules that are not injected. It also does not have any of the\nproperties that non-injected require()
has except require.main
. It\ncan only be used to load built-in modules. Attempting to load a module that can\nonly be found in the file system will throw an error.
Instead of relying on a file based require()
, users can bundle their\napplication into a standalone JavaScript file to inject into the executable.\nThis also ensures a more deterministic dependency graph.
However, if a file based require()
is still needed, that can also be achieved:
const { createRequire } = require('node:module');\nrequire = createRequire(__filename);\n
",
"type": "module",
"displayName": "`require(id)` in the injected main script is not file based"
},
{
"textRaw": "`__filename` and `module.filename` in the injected main script",
"name": "`__filename`_and_`module.filename`_in_the_injected_main_script",
"desc": "The values of __filename
and module.filename
in the injected main script\nare equal to process.execPath
.
The value of __dirname
in the injected main script is equal to the directory\nname of process.execPath
.
This method can be used to retrieve the assets configured to be bundled into the\nsingle-executable application at build time.\nAn error is thrown when no matching asset can be found.
\nkey
<string> the key for the asset in the dictionary specified by the\nassets
field in the single-executable application configuration.encoding
<string> If specified, the asset will be decoded as\na string. Any encoding supported by the TextDecoder
is accepted.\nIf unspecified, an ArrayBuffer
containing a copy of the asset would be\nreturned instead.Similar to sea.getAsset()
, but returns the result in a Blob
.\nAn error is thrown when no matching asset can be found.
key
<string> the key for the asset in the dictionary specified by the\nassets
field in the single-executable application configuration.options
<Object>\ntype
<string> An optional mime type for the blob.This method can be used to retrieve the assets configured to be bundled into the\nsingle-executable application at build time.\nAn error is thrown when no matching asset can be found.
\nUnlike sea.getRawAsset()
or sea.getAssetAsBlob()
, this method does not\nreturn a copy. Instead, it returns the raw asset bundled inside the executable.
For now, users should avoid writing to the returned array buffer. If the\ninjected section is not marked as writable or not aligned properly,\nwrites to the returned array buffer is likely to result in a crash.
\nkey
<string> the key for the asset in the dictionary specified by the\nassets
field in the single-executable application configuration.A tool aiming to create a single executable Node.js application must\ninject the contents of the blob prepared with --experimental-sea-config\"
\ninto:
NODE_SEA_BLOB
if the node
binary is a PE fileNODE_SEA_BLOB
in the NODE_SEA
segment if the node
binary\nis a Mach-O fileNODE_SEA_BLOB
if the node
binary is an ELF fileSearch the binary for the\nNODE_SEA_FUSE_fce680ab2cc467b6e072b8b5df1996b2:0
fuse string and flip the\nlast character to 1
to indicate that a resource has been injected.
Single-executable support is tested regularly on CI only on the following\nplatforms:
\nThis is due to a lack of better tools to generate single-executables that can be\nused to test this feature on other platforms.
\nSuggestions for other resource injection tools/workflows are welcomed. Please\nstart a discussion at https://github.com/nodejs/single-executable/discussions\nto help us document them.
", "type": "module", "displayName": "Platform support" } ], "type": "module", "displayName": "Notes" } ], "type": "module", "displayName": "Single executable applications", "source": "doc/api/single-executable-applications.md" }, { "textRaw": "Stream", "name": "stream", "introduced_in": "v0.10.0", "stability": 2, "stabilityText": "Stable", "desc": "Source Code: lib/stream.js
\nA stream is an abstract interface for working with streaming data in Node.js.\nThe node:stream
module provides an API for implementing the stream interface.
There are many stream objects provided by Node.js. For instance, a\nrequest to an HTTP server and process.stdout
\nare both stream instances.
Streams can be readable, writable, or both. All streams are instances of\nEventEmitter
.
To access the node:stream
module:
const stream = require('node:stream');\n
\nThe node:stream
module is useful for creating new types of stream instances.\nIt is usually not necessary to use the node:stream
module to consume streams.
This document contains two primary sections and a third section for notes. The\nfirst section explains how to use existing streams within an application. The\nsecond section explains how to create new types of streams.
", "type": "module", "displayName": "Organization of this document" }, { "textRaw": "Types of streams", "name": "types_of_streams", "desc": "There are four fundamental stream types within Node.js:
\nWritable
: streams to which data can be written (for example,\nfs.createWriteStream()
).Readable
: streams from which data can be read (for example,\nfs.createReadStream()
).Duplex
: streams that are both Readable
and Writable
(for example,\nnet.Socket
).Transform
: Duplex
streams that can modify or transform the data as it\nis written and read (for example, zlib.createDeflate()
).Additionally, this module includes the utility functions\nstream.pipeline()
, stream.finished()
, stream.Readable.from()
\nand stream.addAbortSignal()
.
The stream/promises
API provides an alternative set of asynchronous utility\nfunctions for streams that return Promise
objects rather than using\ncallbacks. The API is accessible via require('node:stream/promises')
\nor require('node:stream').promises
.
All streams created by Node.js APIs operate exclusively on strings and Buffer
\n(or Uint8Array
) objects. It is possible, however, for stream implementations\nto work with other types of JavaScript values (with the exception of null
,\nwhich serves a special purpose within streams). Such streams are considered to\noperate in \"object mode\".
Stream instances are switched into object mode using the objectMode
option\nwhen the stream is created. Attempting to switch an existing stream into\nobject mode is not safe.
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\nasync function run() {\n await pipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\n
\nimport { pipeline } from 'node:stream/promises';\nimport { createReadStream, createWriteStream } from 'node:fs';\nimport { createGzip } from 'node:zlib';\n\nawait pipeline(\n createReadStream('archive.tar'),\n createGzip(),\n createWriteStream('archive.tar.gz'),\n);\nconsole.log('Pipeline succeeded.');\n
\nTo use an AbortSignal
, pass it inside an options object, as the last argument.\nWhen the signal is aborted, destroy
will be called on the underlying pipeline,\nwith an AbortError
.
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\nasync function run() {\n const ac = new AbortController();\n const signal = ac.signal;\n\n setImmediate(() => ac.abort());\n await pipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n { signal },\n );\n}\n\nrun().catch(console.error); // AbortError\n
\nimport { pipeline } from 'node:stream/promises';\nimport { createReadStream, createWriteStream } from 'node:fs';\nimport { createGzip } from 'node:zlib';\n\nconst ac = new AbortController();\nconst { signal } = ac;\nsetImmediate(() => ac.abort());\ntry {\n await pipeline(\n createReadStream('archive.tar'),\n createGzip(),\n createWriteStream('archive.tar.gz'),\n { signal },\n );\n} catch (err) {\n console.error(err); // AbortError\n}\n
\nThe pipeline
API also supports async generators:
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\n\nasync function run() {\n await pipeline(\n fs.createReadStream('lowercase.txt'),\n async function* (source, { signal }) {\n source.setEncoding('utf8'); // Work with strings rather than `Buffer`s.\n for await (const chunk of source) {\n yield await processChunk(chunk, { signal });\n }\n },\n fs.createWriteStream('uppercase.txt'),\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\n
\nimport { pipeline } from 'node:stream/promises';\nimport { createReadStream, createWriteStream } from 'node:fs';\n\nawait pipeline(\n createReadStream('lowercase.txt'),\n async function* (source, { signal }) {\n source.setEncoding('utf8'); // Work with strings rather than `Buffer`s.\n for await (const chunk of source) {\n yield await processChunk(chunk, { signal });\n }\n },\n createWriteStream('uppercase.txt'),\n);\nconsole.log('Pipeline succeeded.');\n
\nRemember to handle the signal
argument passed into the async generator.\nEspecially in the case where the async generator is the source for the\npipeline (i.e. first argument) or the pipeline will never complete.
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\n\nasync function run() {\n await pipeline(\n async function* ({ signal }) {\n await someLongRunningfn({ signal });\n yield 'asd';\n },\n fs.createWriteStream('uppercase.txt'),\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\n
\nimport { pipeline } from 'node:stream/promises';\nimport fs from 'node:fs';\nawait pipeline(\n async function* ({ signal }) {\n await someLongRunningfn({ signal });\n yield 'asd';\n },\n fs.createWriteStream('uppercase.txt'),\n);\nconsole.log('Pipeline succeeded.');\n
\nThe pipeline
API provides callback version:
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\nasync function run() {\n await pipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\n
\nimport { pipeline } from 'node:stream/promises';\nimport { createReadStream, createWriteStream } from 'node:fs';\nimport { createGzip } from 'node:zlib';\n\nawait pipeline(\n createReadStream('archive.tar'),\n createGzip(),\n createWriteStream('archive.tar.gz'),\n);\nconsole.log('Pipeline succeeded.');\n
\nTo use an AbortSignal
, pass it inside an options object, as the last argument.\nWhen the signal is aborted, destroy
will be called on the underlying pipeline,\nwith an AbortError
.
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\nasync function run() {\n const ac = new AbortController();\n const signal = ac.signal;\n\n setImmediate(() => ac.abort());\n await pipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n { signal },\n );\n}\n\nrun().catch(console.error); // AbortError\n
\nimport { pipeline } from 'node:stream/promises';\nimport { createReadStream, createWriteStream } from 'node:fs';\nimport { createGzip } from 'node:zlib';\n\nconst ac = new AbortController();\nconst { signal } = ac;\nsetImmediate(() => ac.abort());\ntry {\n await pipeline(\n createReadStream('archive.tar'),\n createGzip(),\n createWriteStream('archive.tar.gz'),\n { signal },\n );\n} catch (err) {\n console.error(err); // AbortError\n}\n
\nThe pipeline
API also supports async generators:
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\n\nasync function run() {\n await pipeline(\n fs.createReadStream('lowercase.txt'),\n async function* (source, { signal }) {\n source.setEncoding('utf8'); // Work with strings rather than `Buffer`s.\n for await (const chunk of source) {\n yield await processChunk(chunk, { signal });\n }\n },\n fs.createWriteStream('uppercase.txt'),\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\n
\nimport { pipeline } from 'node:stream/promises';\nimport { createReadStream, createWriteStream } from 'node:fs';\n\nawait pipeline(\n createReadStream('lowercase.txt'),\n async function* (source, { signal }) {\n source.setEncoding('utf8'); // Work with strings rather than `Buffer`s.\n for await (const chunk of source) {\n yield await processChunk(chunk, { signal });\n }\n },\n createWriteStream('uppercase.txt'),\n);\nconsole.log('Pipeline succeeded.');\n
\nRemember to handle the signal
argument passed into the async generator.\nEspecially in the case where the async generator is the source for the\npipeline (i.e. first argument) or the pipeline will never complete.
const { pipeline } = require('node:stream/promises');\nconst fs = require('node:fs');\n\nasync function run() {\n await pipeline(\n async function* ({ signal }) {\n await someLongRunningfn({ signal });\n yield 'asd';\n },\n fs.createWriteStream('uppercase.txt'),\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\n
\nimport { pipeline } from 'node:stream/promises';\nimport fs from 'node:fs';\nawait pipeline(\n async function* ({ signal }) {\n await someLongRunningfn({ signal });\n yield 'asd';\n },\n fs.createWriteStream('uppercase.txt'),\n);\nconsole.log('Pipeline succeeded.');\n
\nThe pipeline
API provides callback version:
const { finished } = require('node:stream/promises');\nconst fs = require('node:fs');\n\nconst rs = fs.createReadStream('archive.tar');\n\nasync function run() {\n await finished(rs);\n console.log('Stream is done reading.');\n}\n\nrun().catch(console.error);\nrs.resume(); // Drain the stream.\n
\nimport { finished } from 'node:stream/promises';\nimport { createReadStream } from 'node:fs';\n\nconst rs = createReadStream('archive.tar');\n\nasync function run() {\n await finished(rs);\n console.log('Stream is done reading.');\n}\n\nrun().catch(console.error);\nrs.resume(); // Drain the stream.\n
\nThe finished
API also provides a callback version.
Both Writable
and Readable
streams will store data in an internal\nbuffer.
The amount of data potentially buffered depends on the highWaterMark
option\npassed into the stream's constructor. For normal streams, the highWaterMark
\noption specifies a total number of bytes. For streams operating\nin object mode, the highWaterMark
specifies a total number of objects.
Data is buffered in Readable
streams when the implementation calls\nstream.push(chunk)
. If the consumer of the Stream does not\ncall stream.read()
, the data will sit in the internal\nqueue until it is consumed.
Once the total size of the internal read buffer reaches the threshold specified\nby highWaterMark
, the stream will temporarily stop reading data from the\nunderlying resource until the data currently buffered can be consumed (that is,\nthe stream will stop calling the internal readable._read()
method that is\nused to fill the read buffer).
Data is buffered in Writable
streams when the\nwritable.write(chunk)
method is called repeatedly. While the\ntotal size of the internal write buffer is below the threshold set by\nhighWaterMark
, calls to writable.write()
will return true
. Once\nthe size of the internal buffer reaches or exceeds the highWaterMark
, false
\nwill be returned.
A key goal of the stream
API, particularly the stream.pipe()
method,\nis to limit the buffering of data to acceptable levels such that sources and\ndestinations of differing speeds will not overwhelm the available memory.
The highWaterMark
option is a threshold, not a limit: it dictates the amount\nof data that a stream buffers before it stops asking for more data. It does not\nenforce a strict memory limitation in general. Specific stream implementations\nmay choose to enforce stricter limits but doing so is optional.
Because Duplex
and Transform
streams are both Readable
and\nWritable
, each maintains two separate internal buffers used for reading and\nwriting, allowing each side to operate independently of the other while\nmaintaining an appropriate and efficient flow of data. For example,\nnet.Socket
instances are Duplex
streams whose Readable
side allows\nconsumption of data received from the socket and whose Writable
side allows\nwriting data to the socket. Because data may be written to the socket at a\nfaster or slower rate than data is received, each side should\noperate (and buffer) independently of the other.
The mechanics of the internal buffering are an internal implementation detail\nand may be changed at any time. However, for certain advanced implementations,\nthe internal buffers can be retrieved using writable.writableBuffer
or\nreadable.readableBuffer
. Use of these undocumented properties is discouraged.
A function to get notified when a stream is no longer readable, writable\nor has experienced an error or a premature close event.
\nconst { finished } = require('node:stream');\nconst fs = require('node:fs');\n\nconst rs = fs.createReadStream('archive.tar');\n\nfinished(rs, (err) => {\n if (err) {\n console.error('Stream failed.', err);\n } else {\n console.log('Stream is done reading.');\n }\n});\n\nrs.resume(); // Drain the stream.\n
\nEspecially useful in error handling scenarios where a stream is destroyed\nprematurely (like an aborted HTTP request), and will not emit 'end'
\nor 'finish'
.
The finished
API provides promise version.
stream.finished()
leaves dangling event listeners (in particular\n'error'
, 'end'
, 'finish'
and 'close'
) after callback
has been\ninvoked. The reason for this is so that unexpected 'error'
events (due to\nincorrect stream implementations) do not cause unexpected crashes.\nIf this is unwanted behavior then the returned cleanup function needs to be\ninvoked in the callback:
const cleanup = finished(rs, (err) => {\n cleanup();\n // ...\n});\n
"
},
{
"textRaw": "`stream.pipeline(source[, ...transforms], destination, callback)`",
"type": "method",
"name": "pipeline",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": [
"v19.7.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46307",
"description": "Added support for webstreams."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/32158",
"description": "The `pipeline(..., cb)` will wait for the `'close'` event before invoking the callback. The implementation tries to detect legacy streams and only apply this behavior to streams which are expected to emit `'close'`."
},
{
"version": "v13.10.0",
"pr-url": "https://github.com/nodejs/node/pull/31223",
"description": "Add support for async generators."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Stream}",
"name": "return",
"type": "Stream"
},
"params": [
{
"textRaw": "`streams` {Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]}",
"name": "streams",
"type": "Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]"
},
{
"textRaw": "`source` {Stream|Iterable|AsyncIterable|Function|ReadableStream}",
"name": "source",
"type": "Stream|Iterable|AsyncIterable|Function|ReadableStream",
"options": [
{
"textRaw": "Returns: {Iterable|AsyncIterable}",
"name": "return",
"type": "Iterable|AsyncIterable"
}
]
},
{
"textRaw": "`...transforms` {Stream|Function|TransformStream}",
"name": "...transforms",
"type": "Stream|Function|TransformStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable}",
"name": "return",
"type": "AsyncIterable"
}
]
},
{
"textRaw": "`destination` {Stream|Function|WritableStream}",
"name": "destination",
"type": "Stream|Function|WritableStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable|Promise}",
"name": "return",
"type": "AsyncIterable|Promise"
}
]
},
{
"textRaw": "`callback` {Function} Called when the pipeline is fully done.",
"name": "callback",
"type": "Function",
"desc": "Called when the pipeline is fully done.",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`val` Resolved value of `Promise` returned by `destination`.",
"name": "val",
"desc": "Resolved value of `Promise` returned by `destination`."
}
]
}
]
}
],
"desc": "A module method to pipe between streams and generators forwarding errors and\nproperly cleaning up and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('node:stream');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\n// Use the pipeline API to easily pipe a series of streams\n// together and get notified when the pipeline is fully done.\n\n// A pipeline to gzip a potentially huge tar file efficiently:\n\npipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n (err) => {\n if (err) {\n console.error('Pipeline failed.', err);\n } else {\n console.log('Pipeline succeeded.');\n }\n },\n);\n
\nThe pipeline
API provides a promise version.
stream.pipeline()
will call stream.destroy(err)
on all streams except:
Readable
streams which have emitted 'end'
or 'close'
.Writable
streams which have emitted 'finish'
or 'close'
.stream.pipeline()
leaves dangling event listeners on the streams\nafter the callback
has been invoked. In the case of reuse of streams after\nfailure, this can cause event listener leaks and swallowed errors. If the last\nstream is readable, dangling event listeners will be removed so that the last\nstream can be consumed later.
stream.pipeline()
closes all the streams when an error is raised.\nThe IncomingRequest
usage with pipeline
could lead to an unexpected behavior\nonce it would destroy the socket without sending the expected response.\nSee the example below:
const fs = require('node:fs');\nconst http = require('node:http');\nconst { pipeline } = require('node:stream');\n\nconst server = http.createServer((req, res) => {\n const fileStream = fs.createReadStream('./fileNotExist.txt');\n pipeline(fileStream, res, (err) => {\n if (err) {\n console.log(err); // No such file\n // this message can't be sent once `pipeline` already destroyed the socket\n return res.end('error!!!');\n }\n });\n});\n
"
},
{
"textRaw": "`stream.pipeline(streams, callback)`",
"type": "method",
"name": "pipeline",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": [
"v19.7.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46307",
"description": "Added support for webstreams."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/32158",
"description": "The `pipeline(..., cb)` will wait for the `'close'` event before invoking the callback. The implementation tries to detect legacy streams and only apply this behavior to streams which are expected to emit `'close'`."
},
{
"version": "v13.10.0",
"pr-url": "https://github.com/nodejs/node/pull/31223",
"description": "Add support for async generators."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Stream}",
"name": "return",
"type": "Stream"
},
"params": [
{
"textRaw": "`streams` {Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]}",
"name": "streams",
"type": "Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]"
},
{
"textRaw": "`source` {Stream|Iterable|AsyncIterable|Function|ReadableStream}",
"name": "source",
"type": "Stream|Iterable|AsyncIterable|Function|ReadableStream",
"options": [
{
"textRaw": "Returns: {Iterable|AsyncIterable}",
"name": "return",
"type": "Iterable|AsyncIterable"
}
]
},
{
"textRaw": "`...transforms` {Stream|Function|TransformStream}",
"name": "...transforms",
"type": "Stream|Function|TransformStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable}",
"name": "return",
"type": "AsyncIterable"
}
]
},
{
"textRaw": "`destination` {Stream|Function|WritableStream}",
"name": "destination",
"type": "Stream|Function|WritableStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable|Promise}",
"name": "return",
"type": "AsyncIterable|Promise"
}
]
},
{
"textRaw": "`callback` {Function} Called when the pipeline is fully done.",
"name": "callback",
"type": "Function",
"desc": "Called when the pipeline is fully done.",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`val` Resolved value of `Promise` returned by `destination`.",
"name": "val",
"desc": "Resolved value of `Promise` returned by `destination`."
}
]
}
]
}
],
"desc": "A module method to pipe between streams and generators forwarding errors and\nproperly cleaning up and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('node:stream');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\n// Use the pipeline API to easily pipe a series of streams\n// together and get notified when the pipeline is fully done.\n\n// A pipeline to gzip a potentially huge tar file efficiently:\n\npipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n (err) => {\n if (err) {\n console.error('Pipeline failed.', err);\n } else {\n console.log('Pipeline succeeded.');\n }\n },\n);\n
\nThe pipeline
API provides a promise version.
stream.pipeline()
will call stream.destroy(err)
on all streams except:
Readable
streams which have emitted 'end'
or 'close'
.Writable
streams which have emitted 'finish'
or 'close'
.stream.pipeline()
leaves dangling event listeners on the streams\nafter the callback
has been invoked. In the case of reuse of streams after\nfailure, this can cause event listener leaks and swallowed errors. If the last\nstream is readable, dangling event listeners will be removed so that the last\nstream can be consumed later.
stream.pipeline()
closes all the streams when an error is raised.\nThe IncomingRequest
usage with pipeline
could lead to an unexpected behavior\nonce it would destroy the socket without sending the expected response.\nSee the example below:
const fs = require('node:fs');\nconst http = require('node:http');\nconst { pipeline } = require('node:stream');\n\nconst server = http.createServer((req, res) => {\n const fileStream = fs.createReadStream('./fileNotExist.txt');\n pipeline(fileStream, res, (err) => {\n if (err) {\n console.log(err); // No such file\n // this message can't be sent once `pipeline` already destroyed the socket\n return res.end('error!!!');\n }\n });\n});\n
"
},
{
"textRaw": "`stream.compose(...streams)`",
"type": "method",
"name": "compose",
"meta": {
"added": [
"v16.9.0"
],
"changes": [
{
"version": "v21.1.0",
"pr-url": "https://github.com/nodejs/node/pull/50187",
"description": "Added support for stream class."
},
{
"version": [
"v19.8.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46675",
"description": "Added support for webstreams."
}
]
},
"stability": 1,
"stabilityText": "`stream.compose` is experimental.",
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Duplex}",
"name": "return",
"type": "stream.Duplex"
},
"params": [
{
"textRaw": "`streams` {Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]|Duplex\\[]|Function}",
"name": "streams",
"type": "Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]|Duplex\\[]|Function"
}
]
}
],
"desc": "Combines two or more streams into a Duplex
stream that writes to the\nfirst stream and reads from the last. Each provided stream is piped into\nthe next, using stream.pipeline
. If any of the streams error then all\nare destroyed, including the outer Duplex
stream.
Because stream.compose
returns a new stream that in turn can (and\nshould) be piped into other streams, it enables composition. In contrast,\nwhen passing streams to stream.pipeline
, typically the first stream is\na readable stream and the last a writable stream, forming a closed\ncircuit.
If passed a Function
it must be a factory method taking a source
\nIterable
.
import { compose, Transform } from 'node:stream';\n\nconst removeSpaces = new Transform({\n transform(chunk, encoding, callback) {\n callback(null, String(chunk).replace(' ', ''));\n },\n});\n\nasync function* toUpper(source) {\n for await (const chunk of source) {\n yield String(chunk).toUpperCase();\n }\n}\n\nlet res = '';\nfor await (const buf of compose(removeSpaces, toUpper).end('hello world')) {\n res += buf;\n}\n\nconsole.log(res); // prints 'HELLOWORLD'\n
\nstream.compose
can be used to convert async iterables, generators and\nfunctions into streams.
AsyncIterable
converts into a readable Duplex
. Cannot yield\nnull
.AsyncGeneratorFunction
converts into a readable/writable transform Duplex
.\nMust take a source AsyncIterable
as first parameter. Cannot yield\nnull
.AsyncFunction
converts into a writable Duplex
. Must return\neither null
or undefined
.import { compose } from 'node:stream';\nimport { finished } from 'node:stream/promises';\n\n// Convert AsyncIterable into readable Duplex.\nconst s1 = compose(async function*() {\n yield 'Hello';\n yield 'World';\n}());\n\n// Convert AsyncGenerator into transform Duplex.\nconst s2 = compose(async function*(source) {\n for await (const chunk of source) {\n yield String(chunk).toUpperCase();\n }\n});\n\nlet res = '';\n\n// Convert AsyncFunction into writable Duplex.\nconst s3 = compose(async function(source) {\n for await (const chunk of source) {\n res += chunk;\n }\n});\n\nawait finished(compose(s1, s2, s3));\n\nconsole.log(res); // prints 'HELLOWORLD'\n
\nSee readable.compose(stream)
for stream.compose
as operator.
A utility method for creating readable streams out of iterators.
\nconst { Readable } = require('node:stream');\n\nasync function * generate() {\n yield 'hello';\n yield 'streams';\n}\n\nconst readable = Readable.from(generate());\n\nreadable.on('data', (chunk) => {\n console.log(chunk);\n});\n
\nCalling Readable.from(string)
or Readable.from(buffer)
will not have\nthe strings or buffers be iterated to match the other streams semantics\nfor performance reasons.
If an Iterable
object containing promises is passed as an argument,\nit might result in unhandled rejection.
const { Readable } = require('node:stream');\n\nReadable.from([\n new Promise((resolve) => setTimeout(resolve('1'), 1500)),\n new Promise((_, reject) => setTimeout(reject(new Error('2')), 1000)), // Unhandled rejection\n]);\n
"
},
{
"textRaw": "`stream.Readable.fromWeb(readableStream[, options])`",
"type": "method",
"name": "fromWeb",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Readable}",
"name": "return",
"type": "stream.Readable"
},
"params": [
{
"textRaw": "`readableStream` {ReadableStream}",
"name": "readableStream",
"type": "ReadableStream"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`encoding` {string}",
"name": "encoding",
"type": "string"
},
{
"textRaw": "`highWaterMark` {number}",
"name": "highWaterMark",
"type": "number"
},
{
"textRaw": "`objectMode` {boolean}",
"name": "objectMode",
"type": "boolean"
},
{
"textRaw": "`signal` {AbortSignal}",
"name": "signal",
"type": "AbortSignal"
}
]
}
]
}
]
},
{
"textRaw": "`stream.Readable.isDisturbed(stream)`",
"type": "method",
"name": "isDisturbed",
"meta": {
"added": [
"v16.8.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: `boolean`",
"name": "return",
"desc": "`boolean`"
},
"params": [
{
"textRaw": "`stream` {stream.Readable|ReadableStream}",
"name": "stream",
"type": "stream.Readable|ReadableStream"
}
]
}
],
"desc": "Returns whether the stream has been read from or cancelled.
" }, { "textRaw": "`stream.isErrored(stream)`", "type": "method", "name": "isErrored", "meta": { "added": [ "v17.3.0", "v16.14.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`stream` {Readable|Writable|Duplex|WritableStream|ReadableStream}", "name": "stream", "type": "Readable|Writable|Duplex|WritableStream|ReadableStream" } ] } ], "desc": "Returns whether the stream has encountered an error.
" }, { "textRaw": "`stream.isReadable(stream)`", "type": "method", "name": "isReadable", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`stream` {Readable|Duplex|ReadableStream}", "name": "stream", "type": "Readable|Duplex|ReadableStream" } ] } ], "desc": "Returns whether the stream is readable.
" }, { "textRaw": "`stream.Readable.toWeb(streamReadable[, options])`", "type": "method", "name": "toWeb", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {ReadableStream}", "name": "return", "type": "ReadableStream" }, "params": [ { "textRaw": "`streamReadable` {stream.Readable}", "name": "streamReadable", "type": "stream.Readable" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`strategy` {Object}", "name": "strategy", "type": "Object", "options": [ { "textRaw": "`highWaterMark` {number} The maximum internal queue size (of the created `ReadableStream`) before backpressure is applied in reading from the given `stream.Readable`. If no value is provided, it will be taken from the given `stream.Readable`.", "name": "highWaterMark", "type": "number", "desc": "The maximum internal queue size (of the created `ReadableStream`) before backpressure is applied in reading from the given `stream.Readable`. If no value is provided, it will be taken from the given `stream.Readable`." }, { "textRaw": "`size` {Function} A function that size of the given chunk of data. If no value is provided, the size will be `1` for all the chunks.", "name": "size", "type": "Function", "desc": "A function that size of the given chunk of data. If no value is provided, the size will be `1` for all the chunks.", "options": [ { "textRaw": "`chunk` {any}", "name": "chunk", "type": "any" }, { "textRaw": "Returns: {number}", "name": "return", "type": "number" } ] } ] } ] } ] } ] }, { "textRaw": "`stream.Writable.fromWeb(writableStream[, options])`", "type": "method", "name": "fromWeb", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {stream.Writable}", "name": "return", "type": "stream.Writable" }, "params": [ { "textRaw": "`writableStream` {WritableStream}", "name": "writableStream", "type": "WritableStream" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`decodeStrings` {boolean}", "name": "decodeStrings", "type": "boolean" }, { "textRaw": "`highWaterMark` {number}", "name": "highWaterMark", "type": "number" }, { "textRaw": "`objectMode` {boolean}", "name": "objectMode", "type": "boolean" }, { "textRaw": "`signal` {AbortSignal}", "name": "signal", "type": "AbortSignal" } ] } ] } ] }, { "textRaw": "`stream.Writable.toWeb(streamWritable)`", "type": "method", "name": "toWeb", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {WritableStream}", "name": "return", "type": "WritableStream" }, "params": [ { "textRaw": "`streamWritable` {stream.Writable}", "name": "streamWritable", "type": "stream.Writable" } ] } ] }, { "textRaw": "`stream.Duplex.from(src)`", "type": "method", "name": "from", "meta": { "added": [ "v16.8.0" ], "changes": [ { "version": [ "v19.5.0", "v18.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/46190", "description": "The `src` argument can now be a `ReadableStream` or `WritableStream`." } ] }, "signatures": [ { "params": [ { "textRaw": "`src` {Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable| AsyncGeneratorFunction|AsyncFunction|Promise|Object| ReadableStream|WritableStream}", "name": "src", "type": "Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable| AsyncGeneratorFunction|AsyncFunction|Promise|Object| ReadableStream|WritableStream" } ] } ], "desc": "A utility method for creating duplex streams.
\nStream
converts writable stream into writable Duplex
and readable stream\nto Duplex
.Blob
converts into readable Duplex
.string
converts into readable Duplex
.ArrayBuffer
converts into readable Duplex
.AsyncIterable
converts into a readable Duplex
. Cannot yield\nnull
.AsyncGeneratorFunction
converts into a readable/writable transform\nDuplex
. Must take a source AsyncIterable
as first parameter. Cannot yield\nnull
.AsyncFunction
converts into a writable Duplex
. Must return\neither null
or undefined
Object ({ writable, readable })
converts readable
and\nwritable
into Stream
and then combines them into Duplex
where the\nDuplex
will write to the writable
and read from the readable
.Promise
converts into readable Duplex
. Value null
is ignored.ReadableStream
converts into readable Duplex
.WritableStream
converts into writable Duplex
.If an Iterable
object containing promises is passed as an argument,\nit might result in unhandled rejection.
const { Duplex } = require('node:stream');\n\nDuplex.from([\n new Promise((resolve) => setTimeout(resolve('1'), 1500)),\n new Promise((_, reject) => setTimeout(reject(new Error('2')), 1000)), // Unhandled rejection\n]);\n
"
},
{
"textRaw": "`stream.Duplex.fromWeb(pair[, options])`",
"type": "method",
"name": "fromWeb",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Duplex}",
"name": "return",
"type": "stream.Duplex"
},
"params": [
{
"textRaw": "`pair` {Object}",
"name": "pair",
"type": "Object",
"options": [
{
"textRaw": "`readable` {ReadableStream}",
"name": "readable",
"type": "ReadableStream"
},
{
"textRaw": "`writable` {WritableStream}",
"name": "writable",
"type": "WritableStream"
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`allowHalfOpen` {boolean}",
"name": "allowHalfOpen",
"type": "boolean"
},
{
"textRaw": "`decodeStrings` {boolean}",
"name": "decodeStrings",
"type": "boolean"
},
{
"textRaw": "`encoding` {string}",
"name": "encoding",
"type": "string"
},
{
"textRaw": "`highWaterMark` {number}",
"name": "highWaterMark",
"type": "number"
},
{
"textRaw": "`objectMode` {boolean}",
"name": "objectMode",
"type": "boolean"
},
{
"textRaw": "`signal` {AbortSignal}",
"name": "signal",
"type": "AbortSignal"
}
]
}
]
}
],
"desc": "import { Duplex } from 'node:stream';\nimport {\n ReadableStream,\n WritableStream,\n} from 'node:stream/web';\n\nconst readable = new ReadableStream({\n start(controller) {\n controller.enqueue('world');\n },\n});\n\nconst writable = new WritableStream({\n write(chunk) {\n console.log('writable', chunk);\n },\n});\n\nconst pair = {\n readable,\n writable,\n};\nconst duplex = Duplex.fromWeb(pair, { encoding: 'utf8', objectMode: true });\n\nduplex.write('hello');\n\nfor await (const chunk of duplex) {\n console.log('readable', chunk);\n}\n
\nconst { Duplex } = require('node:stream');\nconst {\n ReadableStream,\n WritableStream,\n} = require('node:stream/web');\n\nconst readable = new ReadableStream({\n start(controller) {\n controller.enqueue('world');\n },\n});\n\nconst writable = new WritableStream({\n write(chunk) {\n console.log('writable', chunk);\n },\n});\n\nconst pair = {\n readable,\n writable,\n};\nconst duplex = Duplex.fromWeb(pair, { encoding: 'utf8', objectMode: true });\n\nduplex.write('hello');\nduplex.once('readable', () => console.log('readable', duplex.read()));\n
"
},
{
"textRaw": "`stream.Duplex.toWeb(streamDuplex)`",
"type": "method",
"name": "toWeb",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object",
"options": [
{
"textRaw": "`readable` {ReadableStream}",
"name": "readable",
"type": "ReadableStream"
},
{
"textRaw": "`writable` {WritableStream}",
"name": "writable",
"type": "WritableStream"
}
]
},
"params": [
{
"textRaw": "`streamDuplex` {stream.Duplex}",
"name": "streamDuplex",
"type": "stream.Duplex"
}
]
}
],
"desc": "import { Duplex } from 'node:stream';\n\nconst duplex = Duplex({\n objectMode: true,\n read() {\n this.push('world');\n this.push(null);\n },\n write(chunk, encoding, callback) {\n console.log('writable', chunk);\n callback();\n },\n});\n\nconst { readable, writable } = Duplex.toWeb(duplex);\nwritable.getWriter().write('hello');\n\nconst { value } = await readable.getReader().read();\nconsole.log('readable', value);\n
\nconst { Duplex } = require('node:stream');\n\nconst duplex = Duplex({\n objectMode: true,\n read() {\n this.push('world');\n this.push(null);\n },\n write(chunk, encoding, callback) {\n console.log('writable', chunk);\n callback();\n },\n});\n\nconst { readable, writable } = Duplex.toWeb(duplex);\nwritable.getWriter().write('hello');\n\nreadable.getReader().read().then((result) => {\n console.log('readable', result.value);\n});\n
"
},
{
"textRaw": "`stream.addAbortSignal(signal, stream)`",
"type": "method",
"name": "addAbortSignal",
"meta": {
"added": [
"v15.4.0"
],
"changes": [
{
"version": [
"v19.7.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46273",
"description": "Added support for `ReadableStream` and `WritableStream`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`signal` {AbortSignal} A signal representing possible cancellation",
"name": "signal",
"type": "AbortSignal",
"desc": "A signal representing possible cancellation"
},
{
"textRaw": "`stream` {Stream|ReadableStream|WritableStream} A stream to attach a signal to.",
"name": "stream",
"type": "Stream|ReadableStream|WritableStream",
"desc": "A stream to attach a signal to."
}
]
}
],
"desc": "Attaches an AbortSignal to a readable or writeable stream. This lets code\ncontrol stream destruction using an AbortController
.
Calling abort
on the AbortController
corresponding to the passed\nAbortSignal
will behave the same way as calling .destroy(new AbortError())
\non the stream, and controller.error(new AbortError())
for webstreams.
const fs = require('node:fs');\n\nconst controller = new AbortController();\nconst read = addAbortSignal(\n controller.signal,\n fs.createReadStream(('object.json')),\n);\n// Later, abort the operation closing the stream\ncontroller.abort();\n
\nOr using an AbortSignal
with a readable stream as an async iterable:
const controller = new AbortController();\nsetTimeout(() => controller.abort(), 10_000); // set a timeout\nconst stream = addAbortSignal(\n controller.signal,\n fs.createReadStream(('object.json')),\n);\n(async () => {\n try {\n for await (const chunk of stream) {\n await process(chunk);\n }\n } catch (e) {\n if (e.name === 'AbortError') {\n // The operation was cancelled\n } else {\n throw e;\n }\n }\n})();\n
\nOr using an AbortSignal
with a ReadableStream:
const controller = new AbortController();\nconst rs = new ReadableStream({\n start(controller) {\n controller.enqueue('hello');\n controller.enqueue('world');\n controller.close();\n },\n});\n\naddAbortSignal(controller.signal, rs);\n\nfinished(rs, (err) => {\n if (err) {\n if (err.name === 'AbortError') {\n // The operation was cancelled\n }\n }\n});\n\nconst reader = rs.getReader();\n\nreader.read().then(({ value, done }) => {\n console.log(value); // hello\n console.log(done); // false\n controller.abort();\n});\n
"
},
{
"textRaw": "`stream.getDefaultHighWaterMark(objectMode)`",
"type": "method",
"name": "getDefaultHighWaterMark",
"meta": {
"added": [
"v19.9.0",
"v18.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`objectMode` {boolean}",
"name": "objectMode",
"type": "boolean"
}
]
}
],
"desc": "Returns the default highWaterMark used by streams.\nDefaults to 16384
(16 KiB), or 16
for objectMode
.
Sets the default highWaterMark used by streams.
" }, { "textRaw": "`readable.read(0)`", "type": "method", "name": "read", "signatures": [ { "params": [] } ], "desc": "There are some cases where it is necessary to trigger a refresh of the\nunderlying readable stream mechanisms, without actually consuming any\ndata. In such cases, it is possible to call readable.read(0)
, which will\nalways return null
.
If the internal read buffer is below the highWaterMark
, and the\nstream is not currently reading, then calling stream.read(0)
will trigger\na low-level stream._read()
call.
While most applications will almost never need to do this, there are\nsituations within Node.js where this is done, particularly in the\nReadable
stream class internals.
Use of readable.push('')
is not recommended.
Pushing a zero-byte string, Buffer
, or Uint8Array
to a stream that is not in\nobject mode has an interesting side effect. Because it is a call to\nreadable.push()
, the call will end the reading process.\nHowever, because the argument is an empty string, no data is added to the\nreadable buffer so there is nothing for a user to consume.
Almost all Node.js applications, no matter how simple, use streams in some\nmanner. The following is an example of using streams in a Node.js application\nthat implements an HTTP server:
\nconst http = require('node:http');\n\nconst server = http.createServer((req, res) => {\n // `req` is an http.IncomingMessage, which is a readable stream.\n // `res` is an http.ServerResponse, which is a writable stream.\n\n let body = '';\n // Get the data as utf8 strings.\n // If an encoding is not set, Buffer objects will be received.\n req.setEncoding('utf8');\n\n // Readable streams emit 'data' events once a listener is added.\n req.on('data', (chunk) => {\n body += chunk;\n });\n\n // The 'end' event indicates that the entire body has been received.\n req.on('end', () => {\n try {\n const data = JSON.parse(body);\n // Write back something interesting to the user:\n res.write(typeof data);\n res.end();\n } catch (er) {\n // uh oh! bad json!\n res.statusCode = 400;\n return res.end(`error: ${er.message}`);\n }\n });\n});\n\nserver.listen(1337);\n\n// $ curl localhost:1337 -d \"{}\"\n// object\n// $ curl localhost:1337 -d \"\\\"foo\\\"\"\n// string\n// $ curl localhost:1337 -d \"not json\"\n// error: Unexpected token 'o', \"not json\" is not valid JSON\n
\nWritable
streams (such as res
in the example) expose methods such as\nwrite()
and end()
that are used to write data onto the stream.
Readable
streams use the EventEmitter
API for notifying application\ncode when data is available to be read off the stream. That available data can\nbe read from the stream in multiple ways.
Both Writable
and Readable
streams use the EventEmitter
API in\nvarious ways to communicate the current state of the stream.
Duplex
and Transform
streams are both Writable
and\nReadable
.
Applications that are either writing data to or consuming data from a stream\nare not required to implement the stream interfaces directly and will generally\nhave no reason to call require('node:stream')
.
Developers wishing to implement new types of streams should refer to the\nsection API for stream implementers.
", "miscs": [ { "textRaw": "Writable streams", "name": "writable_streams", "desc": "Writable streams are an abstraction for a destination to which data is\nwritten.
\nExamples of Writable
streams include:
process.stdout
, process.stderr
Some of these examples are actually Duplex
streams that implement the\nWritable
interface.
All Writable
streams implement the interface defined by the\nstream.Writable
class.
While specific instances of Writable
streams may differ in various ways,\nall Writable
streams follow the same fundamental usage pattern as illustrated\nin the example below:
const myStream = getWritableStreamSomehow();\nmyStream.write('some data');\nmyStream.write('some more data');\nmyStream.end('done writing data');\n
",
"classes": [
{
"textRaw": "Class: `stream.Writable`",
"type": "class",
"name": "stream.Writable",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"events": [
{
"textRaw": "Event: `'close'`",
"type": "event",
"name": "close",
"meta": {
"added": [
"v0.9.4"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18438",
"description": "Add `emitClose` option to specify if `'close'` is emitted on destroy."
}
]
},
"params": [],
"desc": "The 'close'
event is emitted when the stream and any of its underlying\nresources (a file descriptor, for example) have been closed. The event indicates\nthat no more events will be emitted, and no further computation will occur.
A Writable
stream will always emit the 'close'
event if it is\ncreated with the emitClose
option.
If a call to stream.write(chunk)
returns false
, the\n'drain'
event will be emitted when it is appropriate to resume writing data\nto the stream.
// Write the data to the supplied writable stream one million times.\n// Be attentive to back-pressure.\nfunction writeOneMillionTimes(writer, data, encoding, callback) {\n let i = 1000000;\n write();\n function write() {\n let ok = true;\n do {\n i--;\n if (i === 0) {\n // Last time!\n writer.write(data, encoding, callback);\n } else {\n // See if we should continue, or wait.\n // Don't pass the callback, because we're not done yet.\n ok = writer.write(data, encoding);\n }\n } while (i > 0 && ok);\n if (i > 0) {\n // Had to stop early!\n // Write some more once it drains.\n writer.once('drain', write);\n }\n }\n}\n
"
},
{
"textRaw": "Event: `'error'`",
"type": "event",
"name": "error",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"params": [
{
"textRaw": "{Error}",
"type": "Error"
}
],
"desc": "The 'error'
event is emitted if an error occurred while writing or piping\ndata. The listener callback is passed a single Error
argument when called.
The stream is closed when the 'error'
event is emitted unless the\nautoDestroy
option was set to false
when creating the\nstream.
After 'error'
, no further events other than 'close'
should be emitted\n(including 'error'
events).
The 'finish'
event is emitted after the stream.end()
method\nhas been called, and all data has been flushed to the underlying system.
const writer = getWritableStreamSomehow();\nfor (let i = 0; i < 100; i++) {\n writer.write(`hello, #${i}!\\n`);\n}\nwriter.on('finish', () => {\n console.log('All writes are now complete.');\n});\nwriter.end('This is the end\\n');\n
"
},
{
"textRaw": "Event: `'pipe'`",
"type": "event",
"name": "pipe",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"params": [
{
"textRaw": "`src` {stream.Readable} source stream that is piping to this writable",
"name": "src",
"type": "stream.Readable",
"desc": "source stream that is piping to this writable"
}
],
"desc": "The 'pipe'
event is emitted when the stream.pipe()
method is called on\na readable stream, adding this writable to its set of destinations.
const writer = getWritableStreamSomehow();\nconst reader = getReadableStreamSomehow();\nwriter.on('pipe', (src) => {\n console.log('Something is piping into the writer.');\n assert.equal(src, reader);\n});\nreader.pipe(writer);\n
"
},
{
"textRaw": "Event: `'unpipe'`",
"type": "event",
"name": "unpipe",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"params": [
{
"textRaw": "`src` {stream.Readable} The source stream that [unpiped][`stream.unpipe()`] this writable",
"name": "src",
"type": "stream.Readable",
"desc": "The source stream that [unpiped][`stream.unpipe()`] this writable"
}
],
"desc": "The 'unpipe'
event is emitted when the stream.unpipe()
method is called\non a Readable
stream, removing this Writable
from its set of\ndestinations.
This is also emitted in case this Writable
stream emits an error when a\nReadable
stream pipes into it.
const writer = getWritableStreamSomehow();\nconst reader = getReadableStreamSomehow();\nwriter.on('unpipe', (src) => {\n console.log('Something has stopped piping into the writer.');\n assert.equal(src, reader);\n});\nreader.pipe(writer);\nreader.unpipe(writer);\n
"
}
],
"methods": [
{
"textRaw": "`writable.cork()`",
"type": "method",
"name": "cork",
"meta": {
"added": [
"v0.11.2"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "The writable.cork()
method forces all written data to be buffered in memory.\nThe buffered data will be flushed when either the stream.uncork()
or\nstream.end()
methods are called.
The primary intent of writable.cork()
is to accommodate a situation in which\nseveral small chunks are written to the stream in rapid succession. Instead of\nimmediately forwarding them to the underlying destination, writable.cork()
\nbuffers all the chunks until writable.uncork()
is called, which will pass them\nall to writable._writev()
, if present. This prevents a head-of-line blocking\nsituation where data is being buffered while waiting for the first small chunk\nto be processed. However, use of writable.cork()
without implementing\nwritable._writev()
may have an adverse effect on throughput.
See also: writable.uncork()
, writable._writev()
.
Destroy the stream. Optionally emit an 'error'
event, and emit a 'close'
\nevent (unless emitClose
is set to false
). After this call, the writable\nstream has ended and subsequent calls to write()
or end()
will result in\nan ERR_STREAM_DESTROYED
error.\nThis is a destructive and immediate way to destroy a stream. Previous calls to\nwrite()
may not have drained, and may trigger an ERR_STREAM_DESTROYED
error.\nUse end()
instead of destroy if data should flush before close, or wait for\nthe 'drain'
event before destroying the stream.
const { Writable } = require('node:stream');\n\nconst myStream = new Writable();\n\nconst fooErr = new Error('foo error');\nmyStream.destroy(fooErr);\nmyStream.on('error', (fooErr) => console.error(fooErr.message)); // foo error\n
\nconst { Writable } = require('node:stream');\n\nconst myStream = new Writable();\n\nmyStream.destroy();\nmyStream.on('error', function wontHappen() {});\n
\nconst { Writable } = require('node:stream');\n\nconst myStream = new Writable();\nmyStream.destroy();\n\nmyStream.write('foo', (error) => console.error(error.code));\n// ERR_STREAM_DESTROYED\n
\nOnce destroy()
has been called any further calls will be a no-op and no\nfurther errors except from _destroy()
may be emitted as 'error'
.
Implementors should not override this method,\nbut instead implement writable._destroy()
.
Calling the writable.end()
method signals that no more data will be written\nto the Writable
. The optional chunk
and encoding
arguments allow one\nfinal additional chunk of data to be written immediately before closing the\nstream.
Calling the stream.write()
method after calling\nstream.end()
will raise an error.
// Write 'hello, ' and then end with 'world!'.\nconst fs = require('node:fs');\nconst file = fs.createWriteStream('example.txt');\nfile.write('hello, ');\nfile.end('world!');\n// Writing more now is not allowed!\n
"
},
{
"textRaw": "`writable.setDefaultEncoding(encoding)`",
"type": "method",
"name": "setDefaultEncoding",
"meta": {
"added": [
"v0.11.15"
],
"changes": [
{
"version": "v6.1.0",
"pr-url": "https://github.com/nodejs/node/pull/5040",
"description": "This method now returns a reference to `writable`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {this}",
"name": "return",
"type": "this"
},
"params": [
{
"textRaw": "`encoding` {string} The new default encoding",
"name": "encoding",
"type": "string",
"desc": "The new default encoding"
}
]
}
],
"desc": "The writable.setDefaultEncoding()
method sets the default encoding
for a\nWritable
stream.
The writable.uncork()
method flushes all data buffered since\nstream.cork()
was called.
When using writable.cork()
and writable.uncork()
to manage the buffering\nof writes to a stream, defer calls to writable.uncork()
using\nprocess.nextTick()
. Doing so allows batching of all\nwritable.write()
calls that occur within a given Node.js event loop phase.
stream.cork();\nstream.write('some ');\nstream.write('data ');\nprocess.nextTick(() => stream.uncork());\n
\nIf the writable.cork()
method is called multiple times on a stream, the\nsame number of calls to writable.uncork()
must be called to flush the buffered\ndata.
stream.cork();\nstream.write('some ');\nstream.cork();\nstream.write('data ');\nprocess.nextTick(() => {\n stream.uncork();\n // The data will not be flushed until uncork() is called a second time.\n stream.uncork();\n});\n
\nSee also: writable.cork()
.
The writable.write()
method writes some data to the stream, and calls the\nsupplied callback
once the data has been fully handled. If an error\noccurs, the callback
will be called with the error as its\nfirst argument. The callback
is called asynchronously and before 'error'
is\nemitted.
The return value is true
if the internal buffer is less than the\nhighWaterMark
configured when the stream was created after admitting chunk
.\nIf false
is returned, further attempts to write data to the stream should\nstop until the 'drain'
event is emitted.
While a stream is not draining, calls to write()
will buffer chunk
, and\nreturn false. Once all currently buffered chunks are drained (accepted for\ndelivery by the operating system), the 'drain'
event will be emitted.\nOnce write()
returns false, do not write more chunks\nuntil the 'drain'
event is emitted. While calling write()
on a stream that\nis not draining is allowed, Node.js will buffer all written chunks until\nmaximum memory usage occurs, at which point it will abort unconditionally.\nEven before it aborts, high memory usage will cause poor garbage collector\nperformance and high RSS (which is not typically released back to the system,\neven after the memory is no longer required). Since TCP sockets may never\ndrain if the remote peer does not read the data, writing a socket that is\nnot draining may lead to a remotely exploitable vulnerability.
Writing data while the stream is not draining is particularly\nproblematic for a Transform
, because the Transform
streams are paused\nby default until they are piped or a 'data'
or 'readable'
event handler\nis added.
If the data to be written can be generated or fetched on demand, it is\nrecommended to encapsulate the logic into a Readable
and use\nstream.pipe()
. However, if calling write()
is preferred, it is\npossible to respect backpressure and avoid memory issues using the\n'drain'
event:
function write(data, cb) {\n if (!stream.write(data)) {\n stream.once('drain', cb);\n } else {\n process.nextTick(cb);\n }\n}\n\n// Wait for cb to be called before doing any other write.\nwrite('hello', () => {\n console.log('Write completed, do more writes now.');\n});\n
\nA Writable
stream in object mode will always ignore the encoding
argument.
Is true
after 'close'
has been emitted.
Is true
after writable.destroy()
has been called.
const { Writable } = require('node:stream');\n\nconst myStream = new Writable();\n\nconsole.log(myStream.destroyed); // false\nmyStream.destroy();\nconsole.log(myStream.destroyed); // true\n
"
},
{
"textRaw": "`writable` {boolean}",
"type": "boolean",
"name": "writable",
"meta": {
"added": [
"v11.4.0"
],
"changes": []
},
"desc": "Is true
if it is safe to call writable.write()
, which means\nthe stream has not been destroyed, errored, or ended.
Returns whether the stream was destroyed or errored before emitting 'finish'
.
Is true
after writable.end()
has been called. This property\ndoes not indicate whether the data has been flushed, for this use\nwritable.writableFinished
instead.
Number of times writable.uncork()
needs to be\ncalled in order to fully uncork the stream.
Returns error if the stream has been destroyed with an error.
" }, { "textRaw": "`writableFinished` {boolean}", "type": "boolean", "name": "writableFinished", "meta": { "added": [ "v12.6.0" ], "changes": [] }, "desc": "Is set to true
immediately before the 'finish'
event is emitted.
Return the value of highWaterMark
passed when creating this Writable
.
This property contains the number of bytes (or objects) in the queue\nready to be written. The value provides introspection data regarding\nthe status of the highWaterMark
.
Is true
if the stream's buffer has been full and stream will emit 'drain'
.
Getter for the property objectMode
of a given Writable
stream.
Readable streams are an abstraction for a source from which data is\nconsumed.
\nExamples of Readable
streams include:
process.stdin
All Readable
streams implement the interface defined by the\nstream.Readable
class.
Readable
streams effectively operate in one of two modes: flowing and\npaused. These modes are separate from object mode.\nA Readable
stream can be in object mode or not, regardless of whether\nit is in flowing mode or paused mode.
In flowing mode, data is read from the underlying system automatically\nand provided to an application as quickly as possible using events via the\nEventEmitter
interface.
In paused mode, the stream.read()
method must be called\nexplicitly to read chunks of data from the stream.
All Readable
streams begin in paused mode but can be switched to flowing\nmode in one of the following ways:
'data'
event handler.stream.resume()
method.stream.pipe()
method to send the data to a Writable
.The Readable
can switch back to paused mode using one of the following:
stream.pause()
method.stream.unpipe()
method.The important concept to remember is that a Readable
will not generate data\nuntil a mechanism for either consuming or ignoring that data is provided. If\nthe consuming mechanism is disabled or taken away, the Readable
will attempt\nto stop generating the data.
For backward compatibility reasons, removing 'data'
event handlers will\nnot automatically pause the stream. Also, if there are piped destinations,\nthen calling stream.pause()
will not guarantee that the\nstream will remain paused once those destinations drain and ask for more data.
If a Readable
is switched into flowing mode and there are no consumers\navailable to handle the data, that data will be lost. This can occur, for\ninstance, when the readable.resume()
method is called without a listener\nattached to the 'data'
event, or when a 'data'
event handler is removed\nfrom the stream.
Adding a 'readable'
event handler automatically makes the stream\nstop flowing, and the data has to be consumed via\nreadable.read()
. If the 'readable'
event handler is\nremoved, then the stream will start flowing again if there is a\n'data'
event handler.
The \"two modes\" of operation for a Readable
stream are a simplified\nabstraction for the more complicated internal state management that is happening\nwithin the Readable
stream implementation.
Specifically, at any given point in time, every Readable
is in one of three\npossible states:
readable.readableFlowing === null
readable.readableFlowing === false
readable.readableFlowing === true
When readable.readableFlowing
is null
, no mechanism for consuming the\nstream's data is provided. Therefore, the stream will not generate data.\nWhile in this state, attaching a listener for the 'data'
event, calling the\nreadable.pipe()
method, or calling the readable.resume()
method will switch\nreadable.readableFlowing
to true
, causing the Readable
to begin actively\nemitting events as data is generated.
Calling readable.pause()
, readable.unpipe()
, or receiving backpressure\nwill cause the readable.readableFlowing
to be set as false
,\ntemporarily halting the flowing of events but not halting the generation of\ndata. While in this state, attaching a listener for the 'data'
event\nwill not switch readable.readableFlowing
to true
.
const { PassThrough, Writable } = require('node:stream');\nconst pass = new PassThrough();\nconst writable = new Writable();\n\npass.pipe(writable);\npass.unpipe(writable);\n// readableFlowing is now false.\n\npass.on('data', (chunk) => { console.log(chunk.toString()); });\n// readableFlowing is still false.\npass.write('ok'); // Will not emit 'data'.\npass.resume(); // Must be called to make stream emit 'data'.\n// readableFlowing is now true.\n
\nWhile readable.readableFlowing
is false
, data may be accumulating\nwithin the stream's internal buffer.
The Readable
stream API evolved across multiple Node.js versions and provides\nmultiple methods of consuming stream data. In general, developers should choose\none of the methods of consuming data and should never use multiple methods\nto consume data from a single stream. Specifically, using a combination\nof on('data')
, on('readable')
, pipe()
, or async iterators could\nlead to unintuitive behavior.
The 'close'
event is emitted when the stream and any of its underlying\nresources (a file descriptor, for example) have been closed. The event indicates\nthat no more events will be emitted, and no further computation will occur.
A Readable
stream will always emit the 'close'
event if it is\ncreated with the emitClose
option.
The 'data'
event is emitted whenever the stream is relinquishing ownership of\na chunk of data to a consumer. This may occur whenever the stream is switched\nin flowing mode by calling readable.pipe()
, readable.resume()
, or by\nattaching a listener callback to the 'data'
event. The 'data'
event will\nalso be emitted whenever the readable.read()
method is called and a chunk of\ndata is available to be returned.
Attaching a 'data'
event listener to a stream that has not been explicitly\npaused will switch the stream into flowing mode. Data will then be passed as\nsoon as it is available.
The listener callback will be passed the chunk of data as a string if a default\nencoding has been specified for the stream using the\nreadable.setEncoding()
method; otherwise the data will be passed as a\nBuffer
.
const readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log(`Received ${chunk.length} bytes of data.`);\n});\n
"
},
{
"textRaw": "Event: `'end'`",
"type": "event",
"name": "end",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"params": [],
"desc": "The 'end'
event is emitted when there is no more data to be consumed from\nthe stream.
The 'end'
event will not be emitted unless the data is completely\nconsumed. This can be accomplished by switching the stream into flowing mode,\nor by calling stream.read()
repeatedly until all data has been\nconsumed.
const readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log(`Received ${chunk.length} bytes of data.`);\n});\nreadable.on('end', () => {\n console.log('There will be no more data.');\n});\n
"
},
{
"textRaw": "Event: `'error'`",
"type": "event",
"name": "error",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"params": [
{
"textRaw": "{Error}",
"type": "Error"
}
],
"desc": "The 'error'
event may be emitted by a Readable
implementation at any time.\nTypically, this may occur if the underlying stream is unable to generate data\ndue to an underlying internal failure, or when a stream implementation attempts\nto push an invalid chunk of data.
The listener callback will be passed a single Error
object.
The 'pause'
event is emitted when stream.pause()
is called\nand readableFlowing
is not false
.
The 'readable'
event is emitted when there is data available to be read from\nthe stream or when the end of the stream has been reached. Effectively, the\n'readable'
event indicates that the stream has new information. If data is\navailable, stream.read()
will return that data.
const readable = getReadableStreamSomehow();\nreadable.on('readable', function() {\n // There is some data to read now.\n let data;\n\n while ((data = this.read()) !== null) {\n console.log(data);\n }\n});\n
\nIf the end of the stream has been reached, calling\nstream.read()
will return null
and trigger the 'end'
\nevent. This is also true if there never was any data to be read. For instance,\nin the following example, foo.txt
is an empty file:
const fs = require('node:fs');\nconst rr = fs.createReadStream('foo.txt');\nrr.on('readable', () => {\n console.log(`readable: ${rr.read()}`);\n});\nrr.on('end', () => {\n console.log('end');\n});\n
\nThe output of running this script is:
\n$ node test.js\nreadable: null\nend\n
\nIn some cases, attaching a listener for the 'readable'
event will cause some\namount of data to be read into an internal buffer.
In general, the readable.pipe()
and 'data'
event mechanisms are easier to\nunderstand than the 'readable'
event. However, handling 'readable'
might\nresult in increased throughput.
If both 'readable'
and 'data'
are used at the same time, 'readable'
\ntakes precedence in controlling the flow, i.e. 'data'
will be emitted\nonly when stream.read()
is called. The\nreadableFlowing
property would become false
.\nIf there are 'data'
listeners when 'readable'
is removed, the stream\nwill start flowing, i.e. 'data'
events will be emitted without calling\n.resume()
.
The 'resume'
event is emitted when stream.resume()
is\ncalled and readableFlowing
is not true
.
Destroy the stream. Optionally emit an 'error'
event, and emit a 'close'
\nevent (unless emitClose
is set to false
). After this call, the readable\nstream will release any internal resources and subsequent calls to push()
\nwill be ignored.
Once destroy()
has been called any further calls will be a no-op and no\nfurther errors except from _destroy()
may be emitted as 'error'
.
Implementors should not override this method, but instead implement\nreadable._destroy()
.
The readable.isPaused()
method returns the current operating state of the\nReadable
. This is used primarily by the mechanism that underlies the\nreadable.pipe()
method. In most typical cases, there will be no reason to\nuse this method directly.
const readable = new stream.Readable();\n\nreadable.isPaused(); // === false\nreadable.pause();\nreadable.isPaused(); // === true\nreadable.resume();\nreadable.isPaused(); // === false\n
"
},
{
"textRaw": "`readable.pause()`",
"type": "method",
"name": "pause",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {this}",
"name": "return",
"type": "this"
},
"params": []
}
],
"desc": "The readable.pause()
method will cause a stream in flowing mode to stop\nemitting 'data'
events, switching out of flowing mode. Any data that\nbecomes available will remain in the internal buffer.
const readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log(`Received ${chunk.length} bytes of data.`);\n readable.pause();\n console.log('There will be no additional data for 1 second.');\n setTimeout(() => {\n console.log('Now data will start flowing again.');\n readable.resume();\n }, 1000);\n});\n
\nThe readable.pause()
method has no effect if there is a 'readable'
\nevent listener.
The readable.pipe()
method attaches a Writable
stream to the readable
,\ncausing it to switch automatically into flowing mode and push all of its data\nto the attached Writable
. The flow of data will be automatically managed\nso that the destination Writable
stream is not overwhelmed by a faster\nReadable
stream.
The following example pipes all of the data from the readable
into a file\nnamed file.txt
:
const fs = require('node:fs');\nconst readable = getReadableStreamSomehow();\nconst writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt'.\nreadable.pipe(writable);\n
\nIt is possible to attach multiple Writable
streams to a single Readable
\nstream.
The readable.pipe()
method returns a reference to the destination stream\nmaking it possible to set up chains of piped streams:
const fs = require('node:fs');\nconst zlib = require('node:zlib');\nconst r = fs.createReadStream('file.txt');\nconst z = zlib.createGzip();\nconst w = fs.createWriteStream('file.txt.gz');\nr.pipe(z).pipe(w);\n
\nBy default, stream.end()
is called on the destination Writable
\nstream when the source Readable
stream emits 'end'
, so that the\ndestination is no longer writable. To disable this default behavior, the end
\noption can be passed as false
, causing the destination stream to remain open:
reader.pipe(writer, { end: false });\nreader.on('end', () => {\n writer.end('Goodbye\\n');\n});\n
\nOne important caveat is that if the Readable
stream emits an error during\nprocessing, the Writable
destination is not closed automatically. If an\nerror occurs, it will be necessary to manually close each stream in order\nto prevent memory leaks.
The process.stderr
and process.stdout
Writable
streams are never\nclosed until the Node.js process exits, regardless of the specified options.
The readable.read()
method reads data out of the internal buffer and\nreturns it. If no data is available to be read, null
is returned. By default,\nthe data is returned as a Buffer
object unless an encoding has been\nspecified using the readable.setEncoding()
method or the stream is operating\nin object mode.
The optional size
argument specifies a specific number of bytes to read. If\nsize
bytes are not available to be read, null
will be returned unless\nthe stream has ended, in which case all of the data remaining in the internal\nbuffer will be returned.
If the size
argument is not specified, all of the data contained in the\ninternal buffer will be returned.
The size
argument must be less than or equal to 1 GiB.
The readable.read()
method should only be called on Readable
streams\noperating in paused mode. In flowing mode, readable.read()
is called\nautomatically until the internal buffer is fully drained.
const readable = getReadableStreamSomehow();\n\n// 'readable' may be triggered multiple times as data is buffered in\nreadable.on('readable', () => {\n let chunk;\n console.log('Stream is readable (new data received in buffer)');\n // Use a loop to make sure we read all currently available data\n while (null !== (chunk = readable.read())) {\n console.log(`Read ${chunk.length} bytes of data...`);\n }\n});\n\n// 'end' will be triggered once when there is no more data available\nreadable.on('end', () => {\n console.log('Reached end of stream.');\n});\n
\nEach call to readable.read()
returns a chunk of data, or null
. The chunks\nare not concatenated. A while
loop is necessary to consume all data\ncurrently in the buffer. When reading a large file .read()
may return null
,\nhaving consumed all buffered content so far, but there is still more data to\ncome not yet buffered. In this case a new 'readable'
event will be emitted\nwhen there is more data in the buffer. Finally the 'end'
event will be\nemitted when there is no more data to come.
Therefore to read a file's whole contents from a readable
, it is necessary\nto collect chunks across multiple 'readable'
events:
const chunks = [];\n\nreadable.on('readable', () => {\n let chunk;\n while (null !== (chunk = readable.read())) {\n chunks.push(chunk);\n }\n});\n\nreadable.on('end', () => {\n const content = chunks.join('');\n});\n
\nA Readable
stream in object mode will always return a single item from\na call to readable.read(size)
, regardless of the value of the\nsize
argument.
If the readable.read()
method returns a chunk of data, a 'data'
event will\nalso be emitted.
Calling stream.read([size])
after the 'end'
event has\nbeen emitted will return null
. No runtime error will be raised.
The readable.resume()
method causes an explicitly paused Readable
stream to\nresume emitting 'data'
events, switching the stream into flowing mode.
The readable.resume()
method can be used to fully consume the data from a\nstream without actually processing any of that data:
getReadableStreamSomehow()\n .resume()\n .on('end', () => {\n console.log('Reached the end, but did not read anything.');\n });\n
\nThe readable.resume()
method has no effect if there is a 'readable'
\nevent listener.
The readable.setEncoding()
method sets the character encoding for\ndata read from the Readable
stream.
By default, no encoding is assigned and stream data will be returned as\nBuffer
objects. Setting an encoding causes the stream data\nto be returned as strings of the specified encoding rather than as Buffer
\nobjects. For instance, calling readable.setEncoding('utf8')
will cause the\noutput data to be interpreted as UTF-8 data, and passed as strings. Calling\nreadable.setEncoding('hex')
will cause the data to be encoded in hexadecimal\nstring format.
The Readable
stream will properly handle multi-byte characters delivered\nthrough the stream that would otherwise become improperly decoded if simply\npulled from the stream as Buffer
objects.
const readable = getReadableStreamSomehow();\nreadable.setEncoding('utf8');\nreadable.on('data', (chunk) => {\n assert.equal(typeof chunk, 'string');\n console.log('Got %d characters of string data:', chunk.length);\n});\n
"
},
{
"textRaw": "`readable.unpipe([destination])`",
"type": "method",
"name": "unpipe",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {this}",
"name": "return",
"type": "this"
},
"params": [
{
"textRaw": "`destination` {stream.Writable} Optional specific stream to unpipe",
"name": "destination",
"type": "stream.Writable",
"desc": "Optional specific stream to unpipe"
}
]
}
],
"desc": "The readable.unpipe()
method detaches a Writable
stream previously attached\nusing the stream.pipe()
method.
If the destination
is not specified, then all pipes are detached.
If the destination
is specified, but no pipe is set up for it, then\nthe method does nothing.
const fs = require('node:fs');\nconst readable = getReadableStreamSomehow();\nconst writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt',\n// but only for the first second.\nreadable.pipe(writable);\nsetTimeout(() => {\n console.log('Stop writing to file.txt.');\n readable.unpipe(writable);\n console.log('Manually close the file stream.');\n writable.end();\n}, 1000);\n
"
},
{
"textRaw": "`readable.unshift(chunk[, encoding])`",
"type": "method",
"name": "unshift",
"meta": {
"added": [
"v0.9.11"
],
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/11608",
"description": "The `chunk` argument can now be a `Uint8Array` instance."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`chunk` {Buffer|Uint8Array|string|null|any} Chunk of data to unshift onto the read queue. For streams not operating in object mode, `chunk` must be a string, `Buffer`, `Uint8Array`, or `null`. For object mode streams, `chunk` may be any JavaScript value.",
"name": "chunk",
"type": "Buffer|Uint8Array|string|null|any",
"desc": "Chunk of data to unshift onto the read queue. For streams not operating in object mode, `chunk` must be a string, `Buffer`, `Uint8Array`, or `null`. For object mode streams, `chunk` may be any JavaScript value."
},
{
"textRaw": "`encoding` {string} Encoding of string chunks. Must be a valid `Buffer` encoding, such as `'utf8'` or `'ascii'`.",
"name": "encoding",
"type": "string",
"desc": "Encoding of string chunks. Must be a valid `Buffer` encoding, such as `'utf8'` or `'ascii'`."
}
]
}
],
"desc": "Passing chunk
as null
signals the end of the stream (EOF) and behaves the\nsame as readable.push(null)
, after which no more data can be written. The EOF\nsignal is put at the end of the buffer and any buffered data will still be\nflushed.
The readable.unshift()
method pushes a chunk of data back into the internal\nbuffer. This is useful in certain situations where a stream is being consumed by\ncode that needs to \"un-consume\" some amount of data that it has optimistically\npulled out of the source, so that the data can be passed on to some other party.
The stream.unshift(chunk)
method cannot be called after the 'end'
event\nhas been emitted or a runtime error will be thrown.
Developers using stream.unshift()
often should consider switching to\nuse of a Transform
stream instead. See the API for stream implementers\nsection for more information.
// Pull off a header delimited by \\n\\n.\n// Use unshift() if we get too much.\n// Call the callback with (error, header, stream).\nconst { StringDecoder } = require('node:string_decoder');\nfunction parseHeader(stream, callback) {\n stream.on('error', callback);\n stream.on('readable', onReadable);\n const decoder = new StringDecoder('utf8');\n let header = '';\n function onReadable() {\n let chunk;\n while (null !== (chunk = stream.read())) {\n const str = decoder.write(chunk);\n if (str.includes('\\n\\n')) {\n // Found the header boundary.\n const split = str.split(/\\n\\n/);\n header += split.shift();\n const remaining = split.join('\\n\\n');\n const buf = Buffer.from(remaining, 'utf8');\n stream.removeListener('error', callback);\n // Remove the 'readable' listener before unshifting.\n stream.removeListener('readable', onReadable);\n if (buf.length)\n stream.unshift(buf);\n // Now the body of the message can be read from the stream.\n callback(null, header, stream);\n return;\n }\n // Still reading the header.\n header += str;\n }\n }\n}\n
\nUnlike stream.push(chunk)
, stream.unshift(chunk)
will not\nend the reading process by resetting the internal reading state of the stream.\nThis can cause unexpected results if readable.unshift()
is called during a\nread (i.e. from within a stream._read()
implementation on a\ncustom stream). Following the call to readable.unshift()
with an immediate\nstream.push('')
will reset the reading state appropriately,\nhowever it is best to simply avoid calling readable.unshift()
while in the\nprocess of performing a read.
Prior to Node.js 0.10, streams did not implement the entire node:stream
\nmodule API as it is currently defined. (See Compatibility for more\ninformation.)
When using an older Node.js library that emits 'data'
events and has a\nstream.pause()
method that is advisory only, the\nreadable.wrap()
method can be used to create a Readable
stream that uses\nthe old stream as its data source.
It will rarely be necessary to use readable.wrap()
but the method has been\nprovided as a convenience for interacting with older Node.js applications and\nlibraries.
const { OldReader } = require('./old-api-module.js');\nconst { Readable } = require('node:stream');\nconst oreader = new OldReader();\nconst myReader = new Readable().wrap(oreader);\n\nmyReader.on('readable', () => {\n myReader.read(); // etc.\n});\n
"
},
{
"textRaw": "`readable[Symbol.asyncIterator]()`",
"type": "method",
"name": "[Symbol.asyncIterator]",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": "v11.14.0",
"pr-url": "https://github.com/nodejs/node/pull/26989",
"description": "Symbol.asyncIterator support is no longer experimental."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {AsyncIterator} to fully consume the stream.",
"name": "return",
"type": "AsyncIterator",
"desc": "to fully consume the stream."
},
"params": []
}
],
"desc": "const fs = require('node:fs');\n\nasync function print(readable) {\n readable.setEncoding('utf8');\n let data = '';\n for await (const chunk of readable) {\n data += chunk;\n }\n console.log(data);\n}\n\nprint(fs.createReadStream('file')).catch(console.error);\n
\nIf the loop terminates with a break
, return
, or a throw
, the stream will\nbe destroyed. In other terms, iterating over a stream will consume the stream\nfully. The stream will be read in chunks of size equal to the highWaterMark
\noption. In the code example above, data will be in a single chunk if the file\nhas less then 64 KiB of data because no highWaterMark
option is provided to\nfs.createReadStream()
.
Calls readable.destroy()
with an AbortError
and returns\na promise that fulfills when the stream is finished.
import { Readable } from 'node:stream';\n\nasync function* splitToWords(source) {\n for await (const chunk of source) {\n const words = String(chunk).split(' ');\n\n for (const word of words) {\n yield word;\n }\n }\n}\n\nconst wordsStream = Readable.from(['this is', 'compose as operator']).compose(splitToWords);\nconst words = await wordsStream.toArray();\n\nconsole.log(words); // prints ['this', 'is', 'compose', 'as', 'operator']\n
\nSee stream.compose
for more information.
The iterator created by this method gives users the option to cancel the\ndestruction of the stream if the for await...of
loop is exited by return
,\nbreak
, or throw
, or if the iterator should destroy the stream if the stream\nemitted an error during iteration.
const { Readable } = require('node:stream');\n\nasync function printIterator(readable) {\n for await (const chunk of readable.iterator({ destroyOnReturn: false })) {\n console.log(chunk); // 1\n break;\n }\n\n console.log(readable.destroyed); // false\n\n for await (const chunk of readable.iterator({ destroyOnReturn: false })) {\n console.log(chunk); // Will print 2 and then 3\n }\n\n console.log(readable.destroyed); // True, stream was totally consumed\n}\n\nasync function printSymbolAsyncIterator(readable) {\n for await (const chunk of readable) {\n console.log(chunk); // 1\n break;\n }\n\n console.log(readable.destroyed); // true\n}\n\nasync function showBoth() {\n await printIterator(Readable.from([1, 2, 3]));\n await printSymbolAsyncIterator(Readable.from([1, 2, 3]));\n}\n\nshowBoth();\n
"
},
{
"textRaw": "`readable.map(fn[, options])`",
"type": "method",
"name": "map",
"meta": {
"added": [
"v17.4.0",
"v16.14.0"
],
"changes": [
{
"version": "v20.7.0",
"pr-url": "https://github.com/nodejs/node/pull/49249",
"description": "added `highWaterMark` in options."
}
]
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Readable} a stream mapped with the function `fn`.",
"name": "return",
"type": "Readable",
"desc": "a stream mapped with the function `fn`."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a function to map over every chunk in the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a function to map over every chunk in the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`highWaterMark` {number} how many items to buffer while waiting for user consumption of the mapped items. **Default:** `concurrency * 2 - 1`.",
"name": "highWaterMark",
"type": "number",
"default": "`concurrency * 2 - 1`",
"desc": "how many items to buffer while waiting for user consumption of the mapped items."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method allows mapping over the stream. The fn
function will be called\nfor every chunk in the stream. If the fn
function returns a promise - that\npromise will be await
ed before being passed to the result stream.
import { Readable } from 'node:stream';\nimport { Resolver } from 'node:dns/promises';\n\n// With a synchronous mapper.\nfor await (const chunk of Readable.from([1, 2, 3, 4]).map((x) => x * 2)) {\n console.log(chunk); // 2, 4, 6, 8\n}\n// With an asynchronous mapper, making at most 2 queries at a time.\nconst resolver = new Resolver();\nconst dnsResults = Readable.from([\n 'nodejs.org',\n 'openjsf.org',\n 'www.linuxfoundation.org',\n]).map((domain) => resolver.resolve4(domain), { concurrency: 2 });\nfor await (const result of dnsResults) {\n console.log(result); // Logs the DNS result of resolver.resolve4.\n}\n
"
},
{
"textRaw": "`readable.filter(fn[, options])`",
"type": "method",
"name": "filter",
"meta": {
"added": [
"v17.4.0",
"v16.14.0"
],
"changes": [
{
"version": "v20.7.0",
"pr-url": "https://github.com/nodejs/node/pull/49249",
"description": "added `highWaterMark` in options."
}
]
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Readable} a stream filtered with the predicate `fn`.",
"name": "return",
"type": "Readable",
"desc": "a stream filtered with the predicate `fn`."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a function to filter chunks from the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a function to filter chunks from the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`highWaterMark` {number} how many items to buffer while waiting for user consumption of the filtered items. **Default:** `concurrency * 2 - 1`.",
"name": "highWaterMark",
"type": "number",
"default": "`concurrency * 2 - 1`",
"desc": "how many items to buffer while waiting for user consumption of the filtered items."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method allows filtering the stream. For each chunk in the stream the fn
\nfunction will be called and if it returns a truthy value, the chunk will be\npassed to the result stream. If the fn
function returns a promise - that\npromise will be await
ed.
import { Readable } from 'node:stream';\nimport { Resolver } from 'node:dns/promises';\n\n// With a synchronous predicate.\nfor await (const chunk of Readable.from([1, 2, 3, 4]).filter((x) => x > 2)) {\n console.log(chunk); // 3, 4\n}\n// With an asynchronous predicate, making at most 2 queries at a time.\nconst resolver = new Resolver();\nconst dnsResults = Readable.from([\n 'nodejs.org',\n 'openjsf.org',\n 'www.linuxfoundation.org',\n]).filter(async (domain) => {\n const { address } = await resolver.resolve4(domain, { ttl: true });\n return address.ttl > 60;\n}, { concurrency: 2 });\nfor await (const result of dnsResults) {\n // Logs domains with more than 60 seconds on the resolved dns record.\n console.log(result);\n}\n
"
},
{
"textRaw": "`readable.forEach(fn[, options])`",
"type": "method",
"name": "forEach",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} a promise for when the stream has finished.",
"name": "return",
"type": "Promise",
"desc": "a promise for when the stream has finished."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a function to call on each chunk of the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a function to call on each chunk of the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method allows iterating a stream. For each chunk in the stream the\nfn
function will be called. If the fn
function returns a promise - that\npromise will be await
ed.
This method is different from for await...of
loops in that it can optionally\nprocess chunks concurrently. In addition, a forEach
iteration can only be\nstopped by having passed a signal
option and aborting the related\nAbortController
while for await...of
can be stopped with break
or\nreturn
. In either case the stream will be destroyed.
This method is different from listening to the 'data'
event in that it\nuses the readable
event in the underlying machinary and can limit the\nnumber of concurrent fn
calls.
import { Readable } from 'node:stream';\nimport { Resolver } from 'node:dns/promises';\n\n// With a synchronous predicate.\nfor await (const chunk of Readable.from([1, 2, 3, 4]).filter((x) => x > 2)) {\n console.log(chunk); // 3, 4\n}\n// With an asynchronous predicate, making at most 2 queries at a time.\nconst resolver = new Resolver();\nconst dnsResults = Readable.from([\n 'nodejs.org',\n 'openjsf.org',\n 'www.linuxfoundation.org',\n]).map(async (domain) => {\n const { address } = await resolver.resolve4(domain, { ttl: true });\n return address;\n}, { concurrency: 2 });\nawait dnsResults.forEach((result) => {\n // Logs result, similar to `for await (const result of dnsResults)`\n console.log(result);\n});\nconsole.log('done'); // Stream has finished\n
"
},
{
"textRaw": "`readable.toArray([options])`",
"type": "method",
"name": "toArray",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} a promise containing an array with the contents of the stream.",
"name": "return",
"type": "Promise",
"desc": "a promise containing an array with the contents of the stream."
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} allows cancelling the toArray operation if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows cancelling the toArray operation if the signal is aborted."
}
]
}
]
}
],
"desc": "This method allows easily obtaining the contents of a stream.
\nAs this method reads the entire stream into memory, it negates the benefits of\nstreams. It's intended for interoperability and convenience, not as the primary\nway to consume streams.
\nimport { Readable } from 'node:stream';\nimport { Resolver } from 'node:dns/promises';\n\nawait Readable.from([1, 2, 3, 4]).toArray(); // [1, 2, 3, 4]\n\n// Make dns queries concurrently using .map and collect\n// the results into an array using toArray\nconst dnsResults = await Readable.from([\n 'nodejs.org',\n 'openjsf.org',\n 'www.linuxfoundation.org',\n]).map(async (domain) => {\n const { address } = await resolver.resolve4(domain, { ttl: true });\n return address;\n}, { concurrency: 2 }).toArray();\n
"
},
{
"textRaw": "`readable.some(fn[, options])`",
"type": "method",
"name": "some",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} a promise evaluating to `true` if `fn` returned a truthy value for at least one of the chunks.",
"name": "return",
"type": "Promise",
"desc": "a promise evaluating to `true` if `fn` returned a truthy value for at least one of the chunks."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a function to call on each chunk of the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a function to call on each chunk of the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method is similar to Array.prototype.some
and calls fn
on each chunk\nin the stream until the awaited return value is true
(or any truthy value).\nOnce an fn
call on a chunk awaited return value is truthy, the stream is\ndestroyed and the promise is fulfilled with true
. If none of the fn
\ncalls on the chunks return a truthy value, the promise is fulfilled with\nfalse
.
import { Readable } from 'node:stream';\nimport { stat } from 'node:fs/promises';\n\n// With a synchronous predicate.\nawait Readable.from([1, 2, 3, 4]).some((x) => x > 2); // true\nawait Readable.from([1, 2, 3, 4]).some((x) => x < 0); // false\n\n// With an asynchronous predicate, making at most 2 file checks at a time.\nconst anyBigFile = await Readable.from([\n 'file1',\n 'file2',\n 'file3',\n]).some(async (fileName) => {\n const stats = await stat(fileName);\n return stats.size > 1024 * 1024;\n}, { concurrency: 2 });\nconsole.log(anyBigFile); // `true` if any file in the list is bigger than 1MB\nconsole.log('done'); // Stream has finished\n
"
},
{
"textRaw": "`readable.find(fn[, options])`",
"type": "method",
"name": "find",
"meta": {
"added": [
"v17.5.0",
"v16.17.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} a promise evaluating to the first chunk for which `fn` evaluated with a truthy value, or `undefined` if no element was found.",
"name": "return",
"type": "Promise",
"desc": "a promise evaluating to the first chunk for which `fn` evaluated with a truthy value, or `undefined` if no element was found."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a function to call on each chunk of the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a function to call on each chunk of the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method is similar to Array.prototype.find
and calls fn
on each chunk\nin the stream to find a chunk with a truthy value for fn
. Once an fn
call's\nawaited return value is truthy, the stream is destroyed and the promise is\nfulfilled with value for which fn
returned a truthy value. If all of the\nfn
calls on the chunks return a falsy value, the promise is fulfilled with\nundefined
.
import { Readable } from 'node:stream';\nimport { stat } from 'node:fs/promises';\n\n// With a synchronous predicate.\nawait Readable.from([1, 2, 3, 4]).find((x) => x > 2); // 3\nawait Readable.from([1, 2, 3, 4]).find((x) => x > 0); // 1\nawait Readable.from([1, 2, 3, 4]).find((x) => x > 10); // undefined\n\n// With an asynchronous predicate, making at most 2 file checks at a time.\nconst foundBigFile = await Readable.from([\n 'file1',\n 'file2',\n 'file3',\n]).find(async (fileName) => {\n const stats = await stat(fileName);\n return stats.size > 1024 * 1024;\n}, { concurrency: 2 });\nconsole.log(foundBigFile); // File name of large file, if any file in the list is bigger than 1MB\nconsole.log('done'); // Stream has finished\n
"
},
{
"textRaw": "`readable.every(fn[, options])`",
"type": "method",
"name": "every",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} a promise evaluating to `true` if `fn` returned a truthy value for all of the chunks.",
"name": "return",
"type": "Promise",
"desc": "a promise evaluating to `true` if `fn` returned a truthy value for all of the chunks."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a function to call on each chunk of the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a function to call on each chunk of the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method is similar to Array.prototype.every
and calls fn
on each chunk\nin the stream to check if all awaited return values are truthy value for fn
.\nOnce an fn
call on a chunk awaited return value is falsy, the stream is\ndestroyed and the promise is fulfilled with false
. If all of the fn
calls\non the chunks return a truthy value, the promise is fulfilled with true
.
import { Readable } from 'node:stream';\nimport { stat } from 'node:fs/promises';\n\n// With a synchronous predicate.\nawait Readable.from([1, 2, 3, 4]).every((x) => x > 2); // false\nawait Readable.from([1, 2, 3, 4]).every((x) => x > 0); // true\n\n// With an asynchronous predicate, making at most 2 file checks at a time.\nconst allBigFiles = await Readable.from([\n 'file1',\n 'file2',\n 'file3',\n]).every(async (fileName) => {\n const stats = await stat(fileName);\n return stats.size > 1024 * 1024;\n}, { concurrency: 2 });\n// `true` if all files in the list are bigger than 1MiB\nconsole.log(allBigFiles);\nconsole.log('done'); // Stream has finished\n
"
},
{
"textRaw": "`readable.flatMap(fn[, options])`",
"type": "method",
"name": "flatMap",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Readable} a stream flat-mapped with the function `fn`.",
"name": "return",
"type": "Readable",
"desc": "a stream flat-mapped with the function `fn`."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncGeneratorFunction|AsyncFunction} a function to map over every chunk in the stream.",
"name": "fn",
"type": "Function|AsyncGeneratorFunction|AsyncFunction",
"desc": "a function to map over every chunk in the stream.",
"options": [
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`concurrency` {number} the maximum concurrent invocation of `fn` to call on the stream at once. **Default:** `1`.",
"name": "concurrency",
"type": "number",
"default": "`1`",
"desc": "the maximum concurrent invocation of `fn` to call on the stream at once."
},
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method returns a new stream by applying the given callback to each\nchunk of the stream and then flattening the result.
\nIt is possible to return a stream or another iterable or async iterable from\nfn
and the result streams will be merged (flattened) into the returned\nstream.
import { Readable } from 'node:stream';\nimport { createReadStream } from 'node:fs';\n\n// With a synchronous mapper.\nfor await (const chunk of Readable.from([1, 2, 3, 4]).flatMap((x) => [x, x])) {\n console.log(chunk); // 1, 1, 2, 2, 3, 3, 4, 4\n}\n// With an asynchronous mapper, combine the contents of 4 files\nconst concatResult = Readable.from([\n './1.mjs',\n './2.mjs',\n './3.mjs',\n './4.mjs',\n]).flatMap((fileName) => createReadStream(fileName));\nfor await (const result of concatResult) {\n // This will contain the contents (all chunks) of all 4 files\n console.log(result);\n}\n
"
},
{
"textRaw": "`readable.drop(limit[, options])`",
"type": "method",
"name": "drop",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Readable} a stream with `limit` chunks dropped.",
"name": "return",
"type": "Readable",
"desc": "a stream with `limit` chunks dropped."
},
"params": [
{
"textRaw": "`limit` {number} the number of chunks to drop from the readable.",
"name": "limit",
"type": "number",
"desc": "the number of chunks to drop from the readable."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method returns a new stream with the first limit
chunks dropped.
import { Readable } from 'node:stream';\n\nawait Readable.from([1, 2, 3, 4]).drop(2).toArray(); // [3, 4]\n
"
},
{
"textRaw": "`readable.take(limit[, options])`",
"type": "method",
"name": "take",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Readable} a stream with `limit` chunks taken.",
"name": "return",
"type": "Readable",
"desc": "a stream with `limit` chunks taken."
},
"params": [
{
"textRaw": "`limit` {number} the number of chunks to take from the readable.",
"name": "limit",
"type": "number",
"desc": "the number of chunks to take from the readable."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method returns a new stream with the first limit
chunks.
import { Readable } from 'node:stream';\n\nawait Readable.from([1, 2, 3, 4]).take(2).toArray(); // [1, 2]\n
"
},
{
"textRaw": "`readable.reduce(fn[, initial[, options]])`",
"type": "method",
"name": "reduce",
"meta": {
"added": [
"v17.5.0",
"v16.15.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} a promise for the final value of the reduction.",
"name": "return",
"type": "Promise",
"desc": "a promise for the final value of the reduction."
},
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} a reducer function to call over every chunk in the stream.",
"name": "fn",
"type": "Function|AsyncFunction",
"desc": "a reducer function to call over every chunk in the stream.",
"options": [
{
"textRaw": "`previous` {any} the value obtained from the last call to `fn` or the `initial` value if specified or the first chunk of the stream otherwise.",
"name": "previous",
"type": "any",
"desc": "the value obtained from the last call to `fn` or the `initial` value if specified or the first chunk of the stream otherwise."
},
{
"textRaw": "`data` {any} a chunk of data from the stream.",
"name": "data",
"type": "any",
"desc": "a chunk of data from the stream."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} aborted if the stream is destroyed allowing to abort the `fn` call early.",
"name": "signal",
"type": "AbortSignal",
"desc": "aborted if the stream is destroyed allowing to abort the `fn` call early."
}
]
}
]
},
{
"textRaw": "`initial` {any} the initial value to use in the reduction.",
"name": "initial",
"type": "any",
"desc": "the initial value to use in the reduction."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} allows destroying the stream if the signal is aborted.",
"name": "signal",
"type": "AbortSignal",
"desc": "allows destroying the stream if the signal is aborted."
}
]
}
]
}
],
"desc": "This method calls fn
on each chunk of the stream in order, passing it the\nresult from the calculation on the previous element. It returns a promise for\nthe final value of the reduction.
If no initial
value is supplied the first chunk of the stream is used as the\ninitial value. If the stream is empty, the promise is rejected with a\nTypeError
with the ERR_INVALID_ARGS
code property.
import { Readable } from 'node:stream';\nimport { readdir, stat } from 'node:fs/promises';\nimport { join } from 'node:path';\n\nconst directoryPath = './src';\nconst filesInDir = await readdir(directoryPath);\n\nconst folderSize = await Readable.from(filesInDir)\n .reduce(async (totalSize, file) => {\n const { size } = await stat(join(directoryPath, file));\n return totalSize + size;\n }, 0);\n\nconsole.log(folderSize);\n
\nThe reducer function iterates the stream element-by-element which means that\nthere is no concurrency
parameter or parallelism. To perform a reduce
\nconcurrently, you can extract the async function to readable.map
method.
import { Readable } from 'node:stream';\nimport { readdir, stat } from 'node:fs/promises';\nimport { join } from 'node:path';\n\nconst directoryPath = './src';\nconst filesInDir = await readdir(directoryPath);\n\nconst folderSize = await Readable.from(filesInDir)\n .map((file) => stat(join(directoryPath, file)), { concurrency: 2 })\n .reduce((totalSize, { size }) => totalSize + size, 0);\n\nconsole.log(folderSize);\n
"
}
],
"properties": [
{
"textRaw": "`closed` {boolean}",
"type": "boolean",
"name": "closed",
"meta": {
"added": [
"v18.0.0"
],
"changes": []
},
"desc": "Is true
after 'close'
has been emitted.
Is true
after readable.destroy()
has been called.
Is true
if it is safe to call readable.read()
, which means\nthe stream has not been destroyed or emitted 'error'
or 'end'
.
Returns whether the stream was destroyed or errored before emitting 'end'
.
Returns whether 'data'
has been emitted.
Getter for the property encoding
of a given Readable
stream. The encoding
\nproperty can be set using the readable.setEncoding()
method.
Becomes true
when 'end'
event is emitted.
Returns error if the stream has been destroyed with an error.
" }, { "textRaw": "`readableFlowing` {boolean}", "type": "boolean", "name": "readableFlowing", "meta": { "added": [ "v9.4.0" ], "changes": [] }, "desc": "This property reflects the current state of a Readable
stream as described\nin the Three states section.
Returns the value of highWaterMark
passed when creating this Readable
.
This property contains the number of bytes (or objects) in the queue\nready to be read. The value provides introspection data regarding\nthe status of the highWaterMark
.
Getter for the property objectMode
of a given Readable
stream.
Duplex streams are streams that implement both the Readable
and\nWritable
interfaces.
Examples of Duplex
streams include:
If false
then the stream will automatically end the writable side when the\nreadable side ends. Set initially by the allowHalfOpen
constructor option,\nwhich defaults to true
.
This can be changed manually to change the half-open behavior of an existing\nDuplex
stream instance, but must be changed before the 'end'
event is\nemitted.
Transform streams are Duplex
streams where the output is in some way\nrelated to the input. Like all Duplex
streams, Transform
streams\nimplement both the Readable
and Writable
interfaces.
Examples of Transform
streams include:
Destroy the stream, and optionally emit an 'error'
event. After this call, the\ntransform stream would release any internal resources.\nImplementors should not override this method, but instead implement\nreadable._destroy()
.\nThe default implementation of _destroy()
for Transform
also emit 'close'
\nunless emitClose
is set in false.
Once destroy()
has been called, any further calls will be a no-op and no\nfurther errors except from _destroy()
may be emitted as 'error'
.
A function to get notified when a stream is no longer readable, writable\nor has experienced an error or a premature close event.
\nconst { finished } = require('node:stream');\nconst fs = require('node:fs');\n\nconst rs = fs.createReadStream('archive.tar');\n\nfinished(rs, (err) => {\n if (err) {\n console.error('Stream failed.', err);\n } else {\n console.log('Stream is done reading.');\n }\n});\n\nrs.resume(); // Drain the stream.\n
\nEspecially useful in error handling scenarios where a stream is destroyed\nprematurely (like an aborted HTTP request), and will not emit 'end'
\nor 'finish'
.
The finished
API provides promise version.
stream.finished()
leaves dangling event listeners (in particular\n'error'
, 'end'
, 'finish'
and 'close'
) after callback
has been\ninvoked. The reason for this is so that unexpected 'error'
events (due to\nincorrect stream implementations) do not cause unexpected crashes.\nIf this is unwanted behavior then the returned cleanup function needs to be\ninvoked in the callback:
const cleanup = finished(rs, (err) => {\n cleanup();\n // ...\n});\n
"
},
{
"textRaw": "`stream.pipeline(source[, ...transforms], destination, callback)`",
"type": "method",
"name": "pipeline",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": [
"v19.7.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46307",
"description": "Added support for webstreams."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/32158",
"description": "The `pipeline(..., cb)` will wait for the `'close'` event before invoking the callback. The implementation tries to detect legacy streams and only apply this behavior to streams which are expected to emit `'close'`."
},
{
"version": "v13.10.0",
"pr-url": "https://github.com/nodejs/node/pull/31223",
"description": "Add support for async generators."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Stream}",
"name": "return",
"type": "Stream"
},
"params": [
{
"textRaw": "`streams` {Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]}",
"name": "streams",
"type": "Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]"
},
{
"textRaw": "`source` {Stream|Iterable|AsyncIterable|Function|ReadableStream}",
"name": "source",
"type": "Stream|Iterable|AsyncIterable|Function|ReadableStream",
"options": [
{
"textRaw": "Returns: {Iterable|AsyncIterable}",
"name": "return",
"type": "Iterable|AsyncIterable"
}
]
},
{
"textRaw": "`...transforms` {Stream|Function|TransformStream}",
"name": "...transforms",
"type": "Stream|Function|TransformStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable}",
"name": "return",
"type": "AsyncIterable"
}
]
},
{
"textRaw": "`destination` {Stream|Function|WritableStream}",
"name": "destination",
"type": "Stream|Function|WritableStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable|Promise}",
"name": "return",
"type": "AsyncIterable|Promise"
}
]
},
{
"textRaw": "`callback` {Function} Called when the pipeline is fully done.",
"name": "callback",
"type": "Function",
"desc": "Called when the pipeline is fully done.",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`val` Resolved value of `Promise` returned by `destination`.",
"name": "val",
"desc": "Resolved value of `Promise` returned by `destination`."
}
]
}
]
}
],
"desc": "A module method to pipe between streams and generators forwarding errors and\nproperly cleaning up and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('node:stream');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\n// Use the pipeline API to easily pipe a series of streams\n// together and get notified when the pipeline is fully done.\n\n// A pipeline to gzip a potentially huge tar file efficiently:\n\npipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n (err) => {\n if (err) {\n console.error('Pipeline failed.', err);\n } else {\n console.log('Pipeline succeeded.');\n }\n },\n);\n
\nThe pipeline
API provides a promise version.
stream.pipeline()
will call stream.destroy(err)
on all streams except:
Readable
streams which have emitted 'end'
or 'close'
.Writable
streams which have emitted 'finish'
or 'close'
.stream.pipeline()
leaves dangling event listeners on the streams\nafter the callback
has been invoked. In the case of reuse of streams after\nfailure, this can cause event listener leaks and swallowed errors. If the last\nstream is readable, dangling event listeners will be removed so that the last\nstream can be consumed later.
stream.pipeline()
closes all the streams when an error is raised.\nThe IncomingRequest
usage with pipeline
could lead to an unexpected behavior\nonce it would destroy the socket without sending the expected response.\nSee the example below:
const fs = require('node:fs');\nconst http = require('node:http');\nconst { pipeline } = require('node:stream');\n\nconst server = http.createServer((req, res) => {\n const fileStream = fs.createReadStream('./fileNotExist.txt');\n pipeline(fileStream, res, (err) => {\n if (err) {\n console.log(err); // No such file\n // this message can't be sent once `pipeline` already destroyed the socket\n return res.end('error!!!');\n }\n });\n});\n
"
},
{
"textRaw": "`stream.pipeline(streams, callback)`",
"type": "method",
"name": "pipeline",
"meta": {
"added": [
"v10.0.0"
],
"changes": [
{
"version": [
"v19.7.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46307",
"description": "Added support for webstreams."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/32158",
"description": "The `pipeline(..., cb)` will wait for the `'close'` event before invoking the callback. The implementation tries to detect legacy streams and only apply this behavior to streams which are expected to emit `'close'`."
},
{
"version": "v13.10.0",
"pr-url": "https://github.com/nodejs/node/pull/31223",
"description": "Add support for async generators."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Stream}",
"name": "return",
"type": "Stream"
},
"params": [
{
"textRaw": "`streams` {Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]}",
"name": "streams",
"type": "Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]"
},
{
"textRaw": "`source` {Stream|Iterable|AsyncIterable|Function|ReadableStream}",
"name": "source",
"type": "Stream|Iterable|AsyncIterable|Function|ReadableStream",
"options": [
{
"textRaw": "Returns: {Iterable|AsyncIterable}",
"name": "return",
"type": "Iterable|AsyncIterable"
}
]
},
{
"textRaw": "`...transforms` {Stream|Function|TransformStream}",
"name": "...transforms",
"type": "Stream|Function|TransformStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable}",
"name": "return",
"type": "AsyncIterable"
}
]
},
{
"textRaw": "`destination` {Stream|Function|WritableStream}",
"name": "destination",
"type": "Stream|Function|WritableStream",
"options": [
{
"textRaw": "`source` {AsyncIterable}",
"name": "source",
"type": "AsyncIterable"
},
{
"textRaw": "Returns: {AsyncIterable|Promise}",
"name": "return",
"type": "AsyncIterable|Promise"
}
]
},
{
"textRaw": "`callback` {Function} Called when the pipeline is fully done.",
"name": "callback",
"type": "Function",
"desc": "Called when the pipeline is fully done.",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`val` Resolved value of `Promise` returned by `destination`.",
"name": "val",
"desc": "Resolved value of `Promise` returned by `destination`."
}
]
}
]
}
],
"desc": "A module method to pipe between streams and generators forwarding errors and\nproperly cleaning up and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('node:stream');\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\n\n// Use the pipeline API to easily pipe a series of streams\n// together and get notified when the pipeline is fully done.\n\n// A pipeline to gzip a potentially huge tar file efficiently:\n\npipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n (err) => {\n if (err) {\n console.error('Pipeline failed.', err);\n } else {\n console.log('Pipeline succeeded.');\n }\n },\n);\n
\nThe pipeline
API provides a promise version.
stream.pipeline()
will call stream.destroy(err)
on all streams except:
Readable
streams which have emitted 'end'
or 'close'
.Writable
streams which have emitted 'finish'
or 'close'
.stream.pipeline()
leaves dangling event listeners on the streams\nafter the callback
has been invoked. In the case of reuse of streams after\nfailure, this can cause event listener leaks and swallowed errors. If the last\nstream is readable, dangling event listeners will be removed so that the last\nstream can be consumed later.
stream.pipeline()
closes all the streams when an error is raised.\nThe IncomingRequest
usage with pipeline
could lead to an unexpected behavior\nonce it would destroy the socket without sending the expected response.\nSee the example below:
const fs = require('node:fs');\nconst http = require('node:http');\nconst { pipeline } = require('node:stream');\n\nconst server = http.createServer((req, res) => {\n const fileStream = fs.createReadStream('./fileNotExist.txt');\n pipeline(fileStream, res, (err) => {\n if (err) {\n console.log(err); // No such file\n // this message can't be sent once `pipeline` already destroyed the socket\n return res.end('error!!!');\n }\n });\n});\n
"
},
{
"textRaw": "`stream.compose(...streams)`",
"type": "method",
"name": "compose",
"meta": {
"added": [
"v16.9.0"
],
"changes": [
{
"version": "v21.1.0",
"pr-url": "https://github.com/nodejs/node/pull/50187",
"description": "Added support for stream class."
},
{
"version": [
"v19.8.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46675",
"description": "Added support for webstreams."
}
]
},
"stability": 1,
"stabilityText": "`stream.compose` is experimental.",
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Duplex}",
"name": "return",
"type": "stream.Duplex"
},
"params": [
{
"textRaw": "`streams` {Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]|Duplex\\[]|Function}",
"name": "streams",
"type": "Stream\\[]|Iterable\\[]|AsyncIterable\\[]|Function\\[]| ReadableStream\\[]|WritableStream\\[]|TransformStream\\[]|Duplex\\[]|Function"
}
]
}
],
"desc": "Combines two or more streams into a Duplex
stream that writes to the\nfirst stream and reads from the last. Each provided stream is piped into\nthe next, using stream.pipeline
. If any of the streams error then all\nare destroyed, including the outer Duplex
stream.
Because stream.compose
returns a new stream that in turn can (and\nshould) be piped into other streams, it enables composition. In contrast,\nwhen passing streams to stream.pipeline
, typically the first stream is\na readable stream and the last a writable stream, forming a closed\ncircuit.
If passed a Function
it must be a factory method taking a source
\nIterable
.
import { compose, Transform } from 'node:stream';\n\nconst removeSpaces = new Transform({\n transform(chunk, encoding, callback) {\n callback(null, String(chunk).replace(' ', ''));\n },\n});\n\nasync function* toUpper(source) {\n for await (const chunk of source) {\n yield String(chunk).toUpperCase();\n }\n}\n\nlet res = '';\nfor await (const buf of compose(removeSpaces, toUpper).end('hello world')) {\n res += buf;\n}\n\nconsole.log(res); // prints 'HELLOWORLD'\n
\nstream.compose
can be used to convert async iterables, generators and\nfunctions into streams.
AsyncIterable
converts into a readable Duplex
. Cannot yield\nnull
.AsyncGeneratorFunction
converts into a readable/writable transform Duplex
.\nMust take a source AsyncIterable
as first parameter. Cannot yield\nnull
.AsyncFunction
converts into a writable Duplex
. Must return\neither null
or undefined
.import { compose } from 'node:stream';\nimport { finished } from 'node:stream/promises';\n\n// Convert AsyncIterable into readable Duplex.\nconst s1 = compose(async function*() {\n yield 'Hello';\n yield 'World';\n}());\n\n// Convert AsyncGenerator into transform Duplex.\nconst s2 = compose(async function*(source) {\n for await (const chunk of source) {\n yield String(chunk).toUpperCase();\n }\n});\n\nlet res = '';\n\n// Convert AsyncFunction into writable Duplex.\nconst s3 = compose(async function(source) {\n for await (const chunk of source) {\n res += chunk;\n }\n});\n\nawait finished(compose(s1, s2, s3));\n\nconsole.log(res); // prints 'HELLOWORLD'\n
\nSee readable.compose(stream)
for stream.compose
as operator.
A utility method for creating readable streams out of iterators.
\nconst { Readable } = require('node:stream');\n\nasync function * generate() {\n yield 'hello';\n yield 'streams';\n}\n\nconst readable = Readable.from(generate());\n\nreadable.on('data', (chunk) => {\n console.log(chunk);\n});\n
\nCalling Readable.from(string)
or Readable.from(buffer)
will not have\nthe strings or buffers be iterated to match the other streams semantics\nfor performance reasons.
If an Iterable
object containing promises is passed as an argument,\nit might result in unhandled rejection.
const { Readable } = require('node:stream');\n\nReadable.from([\n new Promise((resolve) => setTimeout(resolve('1'), 1500)),\n new Promise((_, reject) => setTimeout(reject(new Error('2')), 1000)), // Unhandled rejection\n]);\n
"
},
{
"textRaw": "`stream.Readable.fromWeb(readableStream[, options])`",
"type": "method",
"name": "fromWeb",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Readable}",
"name": "return",
"type": "stream.Readable"
},
"params": [
{
"textRaw": "`readableStream` {ReadableStream}",
"name": "readableStream",
"type": "ReadableStream"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`encoding` {string}",
"name": "encoding",
"type": "string"
},
{
"textRaw": "`highWaterMark` {number}",
"name": "highWaterMark",
"type": "number"
},
{
"textRaw": "`objectMode` {boolean}",
"name": "objectMode",
"type": "boolean"
},
{
"textRaw": "`signal` {AbortSignal}",
"name": "signal",
"type": "AbortSignal"
}
]
}
]
}
]
},
{
"textRaw": "`stream.Readable.isDisturbed(stream)`",
"type": "method",
"name": "isDisturbed",
"meta": {
"added": [
"v16.8.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: `boolean`",
"name": "return",
"desc": "`boolean`"
},
"params": [
{
"textRaw": "`stream` {stream.Readable|ReadableStream}",
"name": "stream",
"type": "stream.Readable|ReadableStream"
}
]
}
],
"desc": "Returns whether the stream has been read from or cancelled.
" }, { "textRaw": "`stream.isErrored(stream)`", "type": "method", "name": "isErrored", "meta": { "added": [ "v17.3.0", "v16.14.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`stream` {Readable|Writable|Duplex|WritableStream|ReadableStream}", "name": "stream", "type": "Readable|Writable|Duplex|WritableStream|ReadableStream" } ] } ], "desc": "Returns whether the stream has encountered an error.
" }, { "textRaw": "`stream.isReadable(stream)`", "type": "method", "name": "isReadable", "meta": { "added": [ "v17.4.0", "v16.14.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`stream` {Readable|Duplex|ReadableStream}", "name": "stream", "type": "Readable|Duplex|ReadableStream" } ] } ], "desc": "Returns whether the stream is readable.
" }, { "textRaw": "`stream.Readable.toWeb(streamReadable[, options])`", "type": "method", "name": "toWeb", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {ReadableStream}", "name": "return", "type": "ReadableStream" }, "params": [ { "textRaw": "`streamReadable` {stream.Readable}", "name": "streamReadable", "type": "stream.Readable" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`strategy` {Object}", "name": "strategy", "type": "Object", "options": [ { "textRaw": "`highWaterMark` {number} The maximum internal queue size (of the created `ReadableStream`) before backpressure is applied in reading from the given `stream.Readable`. If no value is provided, it will be taken from the given `stream.Readable`.", "name": "highWaterMark", "type": "number", "desc": "The maximum internal queue size (of the created `ReadableStream`) before backpressure is applied in reading from the given `stream.Readable`. If no value is provided, it will be taken from the given `stream.Readable`." }, { "textRaw": "`size` {Function} A function that size of the given chunk of data. If no value is provided, the size will be `1` for all the chunks.", "name": "size", "type": "Function", "desc": "A function that size of the given chunk of data. If no value is provided, the size will be `1` for all the chunks.", "options": [ { "textRaw": "`chunk` {any}", "name": "chunk", "type": "any" }, { "textRaw": "Returns: {number}", "name": "return", "type": "number" } ] } ] } ] } ] } ] }, { "textRaw": "`stream.Writable.fromWeb(writableStream[, options])`", "type": "method", "name": "fromWeb", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {stream.Writable}", "name": "return", "type": "stream.Writable" }, "params": [ { "textRaw": "`writableStream` {WritableStream}", "name": "writableStream", "type": "WritableStream" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`decodeStrings` {boolean}", "name": "decodeStrings", "type": "boolean" }, { "textRaw": "`highWaterMark` {number}", "name": "highWaterMark", "type": "number" }, { "textRaw": "`objectMode` {boolean}", "name": "objectMode", "type": "boolean" }, { "textRaw": "`signal` {AbortSignal}", "name": "signal", "type": "AbortSignal" } ] } ] } ] }, { "textRaw": "`stream.Writable.toWeb(streamWritable)`", "type": "method", "name": "toWeb", "meta": { "added": [ "v17.0.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "signatures": [ { "return": { "textRaw": "Returns: {WritableStream}", "name": "return", "type": "WritableStream" }, "params": [ { "textRaw": "`streamWritable` {stream.Writable}", "name": "streamWritable", "type": "stream.Writable" } ] } ] }, { "textRaw": "`stream.Duplex.from(src)`", "type": "method", "name": "from", "meta": { "added": [ "v16.8.0" ], "changes": [ { "version": [ "v19.5.0", "v18.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/46190", "description": "The `src` argument can now be a `ReadableStream` or `WritableStream`." } ] }, "signatures": [ { "params": [ { "textRaw": "`src` {Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable| AsyncGeneratorFunction|AsyncFunction|Promise|Object| ReadableStream|WritableStream}", "name": "src", "type": "Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable| AsyncGeneratorFunction|AsyncFunction|Promise|Object| ReadableStream|WritableStream" } ] } ], "desc": "A utility method for creating duplex streams.
\nStream
converts writable stream into writable Duplex
and readable stream\nto Duplex
.Blob
converts into readable Duplex
.string
converts into readable Duplex
.ArrayBuffer
converts into readable Duplex
.AsyncIterable
converts into a readable Duplex
. Cannot yield\nnull
.AsyncGeneratorFunction
converts into a readable/writable transform\nDuplex
. Must take a source AsyncIterable
as first parameter. Cannot yield\nnull
.AsyncFunction
converts into a writable Duplex
. Must return\neither null
or undefined
Object ({ writable, readable })
converts readable
and\nwritable
into Stream
and then combines them into Duplex
where the\nDuplex
will write to the writable
and read from the readable
.Promise
converts into readable Duplex
. Value null
is ignored.ReadableStream
converts into readable Duplex
.WritableStream
converts into writable Duplex
.If an Iterable
object containing promises is passed as an argument,\nit might result in unhandled rejection.
const { Duplex } = require('node:stream');\n\nDuplex.from([\n new Promise((resolve) => setTimeout(resolve('1'), 1500)),\n new Promise((_, reject) => setTimeout(reject(new Error('2')), 1000)), // Unhandled rejection\n]);\n
"
},
{
"textRaw": "`stream.Duplex.fromWeb(pair[, options])`",
"type": "method",
"name": "fromWeb",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Duplex}",
"name": "return",
"type": "stream.Duplex"
},
"params": [
{
"textRaw": "`pair` {Object}",
"name": "pair",
"type": "Object",
"options": [
{
"textRaw": "`readable` {ReadableStream}",
"name": "readable",
"type": "ReadableStream"
},
{
"textRaw": "`writable` {WritableStream}",
"name": "writable",
"type": "WritableStream"
}
]
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`allowHalfOpen` {boolean}",
"name": "allowHalfOpen",
"type": "boolean"
},
{
"textRaw": "`decodeStrings` {boolean}",
"name": "decodeStrings",
"type": "boolean"
},
{
"textRaw": "`encoding` {string}",
"name": "encoding",
"type": "string"
},
{
"textRaw": "`highWaterMark` {number}",
"name": "highWaterMark",
"type": "number"
},
{
"textRaw": "`objectMode` {boolean}",
"name": "objectMode",
"type": "boolean"
},
{
"textRaw": "`signal` {AbortSignal}",
"name": "signal",
"type": "AbortSignal"
}
]
}
]
}
],
"desc": "import { Duplex } from 'node:stream';\nimport {\n ReadableStream,\n WritableStream,\n} from 'node:stream/web';\n\nconst readable = new ReadableStream({\n start(controller) {\n controller.enqueue('world');\n },\n});\n\nconst writable = new WritableStream({\n write(chunk) {\n console.log('writable', chunk);\n },\n});\n\nconst pair = {\n readable,\n writable,\n};\nconst duplex = Duplex.fromWeb(pair, { encoding: 'utf8', objectMode: true });\n\nduplex.write('hello');\n\nfor await (const chunk of duplex) {\n console.log('readable', chunk);\n}\n
\nconst { Duplex } = require('node:stream');\nconst {\n ReadableStream,\n WritableStream,\n} = require('node:stream/web');\n\nconst readable = new ReadableStream({\n start(controller) {\n controller.enqueue('world');\n },\n});\n\nconst writable = new WritableStream({\n write(chunk) {\n console.log('writable', chunk);\n },\n});\n\nconst pair = {\n readable,\n writable,\n};\nconst duplex = Duplex.fromWeb(pair, { encoding: 'utf8', objectMode: true });\n\nduplex.write('hello');\nduplex.once('readable', () => console.log('readable', duplex.read()));\n
"
},
{
"textRaw": "`stream.Duplex.toWeb(streamDuplex)`",
"type": "method",
"name": "toWeb",
"meta": {
"added": [
"v17.0.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object",
"options": [
{
"textRaw": "`readable` {ReadableStream}",
"name": "readable",
"type": "ReadableStream"
},
{
"textRaw": "`writable` {WritableStream}",
"name": "writable",
"type": "WritableStream"
}
]
},
"params": [
{
"textRaw": "`streamDuplex` {stream.Duplex}",
"name": "streamDuplex",
"type": "stream.Duplex"
}
]
}
],
"desc": "import { Duplex } from 'node:stream';\n\nconst duplex = Duplex({\n objectMode: true,\n read() {\n this.push('world');\n this.push(null);\n },\n write(chunk, encoding, callback) {\n console.log('writable', chunk);\n callback();\n },\n});\n\nconst { readable, writable } = Duplex.toWeb(duplex);\nwritable.getWriter().write('hello');\n\nconst { value } = await readable.getReader().read();\nconsole.log('readable', value);\n
\nconst { Duplex } = require('node:stream');\n\nconst duplex = Duplex({\n objectMode: true,\n read() {\n this.push('world');\n this.push(null);\n },\n write(chunk, encoding, callback) {\n console.log('writable', chunk);\n callback();\n },\n});\n\nconst { readable, writable } = Duplex.toWeb(duplex);\nwritable.getWriter().write('hello');\n\nreadable.getReader().read().then((result) => {\n console.log('readable', result.value);\n});\n
"
},
{
"textRaw": "`stream.addAbortSignal(signal, stream)`",
"type": "method",
"name": "addAbortSignal",
"meta": {
"added": [
"v15.4.0"
],
"changes": [
{
"version": [
"v19.7.0",
"v18.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46273",
"description": "Added support for `ReadableStream` and `WritableStream`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`signal` {AbortSignal} A signal representing possible cancellation",
"name": "signal",
"type": "AbortSignal",
"desc": "A signal representing possible cancellation"
},
{
"textRaw": "`stream` {Stream|ReadableStream|WritableStream} A stream to attach a signal to.",
"name": "stream",
"type": "Stream|ReadableStream|WritableStream",
"desc": "A stream to attach a signal to."
}
]
}
],
"desc": "Attaches an AbortSignal to a readable or writeable stream. This lets code\ncontrol stream destruction using an AbortController
.
Calling abort
on the AbortController
corresponding to the passed\nAbortSignal
will behave the same way as calling .destroy(new AbortError())
\non the stream, and controller.error(new AbortError())
for webstreams.
const fs = require('node:fs');\n\nconst controller = new AbortController();\nconst read = addAbortSignal(\n controller.signal,\n fs.createReadStream(('object.json')),\n);\n// Later, abort the operation closing the stream\ncontroller.abort();\n
\nOr using an AbortSignal
with a readable stream as an async iterable:
const controller = new AbortController();\nsetTimeout(() => controller.abort(), 10_000); // set a timeout\nconst stream = addAbortSignal(\n controller.signal,\n fs.createReadStream(('object.json')),\n);\n(async () => {\n try {\n for await (const chunk of stream) {\n await process(chunk);\n }\n } catch (e) {\n if (e.name === 'AbortError') {\n // The operation was cancelled\n } else {\n throw e;\n }\n }\n})();\n
\nOr using an AbortSignal
with a ReadableStream:
const controller = new AbortController();\nconst rs = new ReadableStream({\n start(controller) {\n controller.enqueue('hello');\n controller.enqueue('world');\n controller.close();\n },\n});\n\naddAbortSignal(controller.signal, rs);\n\nfinished(rs, (err) => {\n if (err) {\n if (err.name === 'AbortError') {\n // The operation was cancelled\n }\n }\n});\n\nconst reader = rs.getReader();\n\nreader.read().then(({ value, done }) => {\n console.log(value); // hello\n console.log(done); // false\n controller.abort();\n});\n
"
},
{
"textRaw": "`stream.getDefaultHighWaterMark(objectMode)`",
"type": "method",
"name": "getDefaultHighWaterMark",
"meta": {
"added": [
"v19.9.0",
"v18.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`objectMode` {boolean}",
"name": "objectMode",
"type": "boolean"
}
]
}
],
"desc": "Returns the default highWaterMark used by streams.\nDefaults to 16384
(16 KiB), or 16
for objectMode
.
Sets the default highWaterMark used by streams.
" } ] }, { "textRaw": "API for stream implementers", "name": "API for stream implementers", "type": "misc", "desc": "The node:stream
module API has been designed to make it possible to easily\nimplement streams using JavaScript's prototypal inheritance model.
First, a stream developer would declare a new JavaScript class that extends one\nof the four basic stream classes (stream.Writable
, stream.Readable
,\nstream.Duplex
, or stream.Transform
), making sure they call the appropriate\nparent class constructor:
const { Writable } = require('node:stream');\n\nclass MyWritable extends Writable {\n constructor({ highWaterMark, ...options }) {\n super({ highWaterMark });\n // ...\n }\n}\n
\nWhen extending streams, keep in mind what options the user\ncan and should provide before forwarding these to the base constructor. For\nexample, if the implementation makes assumptions in regard to the\nautoDestroy
and emitClose
options, do not allow the\nuser to override these. Be explicit about what\noptions are forwarded instead of implicitly forwarding all options.
The new stream class must then implement one or more specific methods, depending\non the type of stream being created, as detailed in the chart below:
\nUse-case | \nClass | \nMethod(s) to implement | \n
---|---|---|
Reading only | \nReadable | \n_read() | \n
Writing only | \nWritable | \n_write() , _writev() , _final() | \n
Reading and writing | \nDuplex | \n_read() , _write() , _writev() , _final() | \n
Operate on written data, then read the result | \nTransform | \n_transform() , _flush() , _final() | \n
The implementation code for a stream should never call the \"public\" methods\nof a stream that are intended for use by consumers (as described in the\nAPI for stream consumers section). Doing so may lead to adverse side effects\nin application code consuming the stream.
\nAvoid overriding public methods such as write()
, end()
, cork()
,\nuncork()
, read()
and destroy()
, or emitting internal events such\nas 'error'
, 'data'
, 'end'
, 'finish'
and 'close'
through .emit()
.\nDoing so can break current and future stream invariants leading to behavior\nand/or compatibility issues with other streams, stream utilities, and user\nexpectations.
For many simple cases, it is possible to create a stream without relying on\ninheritance. This can be accomplished by directly creating instances of the\nstream.Writable
, stream.Readable
, stream.Duplex
, or stream.Transform
\nobjects and passing appropriate methods as constructor options.
const { Writable } = require('node:stream');\n\nconst myWritable = new Writable({\n construct(callback) {\n // Initialize state and load resources...\n },\n write(chunk, encoding, callback) {\n // ...\n },\n destroy() {\n // Free resources...\n },\n});\n
",
"type": "misc",
"displayName": "Simplified construction"
},
{
"textRaw": "Implementing a writable stream",
"name": "implementing_a_writable_stream",
"desc": "The stream.Writable
class is extended to implement a Writable
stream.
Custom Writable
streams must call the new stream.Writable([options])
\nconstructor and implement the writable._write()
and/or writable._writev()
\nmethod.
const { Writable } = require('node:stream');\n\nclass MyWritable extends Writable {\n constructor(options) {\n // Calls the stream.Writable() constructor.\n super(options);\n // ...\n }\n}\n
\nOr, when using pre-ES6 style constructors:
\nconst { Writable } = require('node:stream');\nconst util = require('node:util');\n\nfunction MyWritable(options) {\n if (!(this instanceof MyWritable))\n return new MyWritable(options);\n Writable.call(this, options);\n}\nutil.inherits(MyWritable, Writable);\n
\nOr, using the simplified constructor approach:
\nconst { Writable } = require('node:stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n // ...\n },\n writev(chunks, callback) {\n // ...\n },\n});\n
\nCalling abort
on the AbortController
corresponding to the passed\nAbortSignal
will behave the same way as calling .destroy(new AbortError())
\non the writeable stream.
const { Writable } = require('node:stream');\n\nconst controller = new AbortController();\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n // ...\n },\n writev(chunks, callback) {\n // ...\n },\n signal: controller.signal,\n});\n// Later, abort the operation closing the stream\ncontroller.abort();\n
"
}
],
"methods": [
{
"textRaw": "`writable._construct(callback)`",
"type": "method",
"name": "_construct",
"meta": {
"added": [
"v15.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`callback` {Function} Call this function (optionally with an error argument) when the stream has finished initializing.",
"name": "callback",
"type": "Function",
"desc": "Call this function (optionally with an error argument) when the stream has finished initializing."
}
]
}
],
"desc": "The _construct()
method MUST NOT be called directly. It may be implemented\nby child classes, and if so, will be called by the internal Writable
\nclass methods only.
This optional function will be called in a tick after the stream constructor\nhas returned, delaying any _write()
, _final()
and _destroy()
calls until\ncallback
is called. This is useful to initialize state or asynchronously\ninitialize resources before the stream can be used.
const { Writable } = require('node:stream');\nconst fs = require('node:fs');\n\nclass WriteStream extends Writable {\n constructor(filename) {\n super();\n this.filename = filename;\n this.fd = null;\n }\n _construct(callback) {\n fs.open(this.filename, (err, fd) => {\n if (err) {\n callback(err);\n } else {\n this.fd = fd;\n callback();\n }\n });\n }\n _write(chunk, encoding, callback) {\n fs.write(this.fd, chunk, callback);\n }\n _destroy(err, callback) {\n if (this.fd) {\n fs.close(this.fd, (er) => callback(er || err));\n } else {\n callback(err);\n }\n }\n}\n
"
},
{
"textRaw": "`writable._write(chunk, encoding, callback)`",
"type": "method",
"name": "_write",
"meta": {
"changes": [
{
"version": "v12.11.0",
"pr-url": "https://github.com/nodejs/node/pull/29639",
"description": "_write() is optional when providing _writev()."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`chunk` {Buffer|string|any} The `Buffer` to be written, converted from the `string` passed to [`stream.write()`][stream-write]. If the stream's `decodeStrings` option is `false` or the stream is operating in object mode, the chunk will not be converted & will be whatever was passed to [`stream.write()`][stream-write].",
"name": "chunk",
"type": "Buffer|string|any",
"desc": "The `Buffer` to be written, converted from the `string` passed to [`stream.write()`][stream-write]. If the stream's `decodeStrings` option is `false` or the stream is operating in object mode, the chunk will not be converted & will be whatever was passed to [`stream.write()`][stream-write]."
},
{
"textRaw": "`encoding` {string} If the chunk is a string, then `encoding` is the character encoding of that string. If chunk is a `Buffer`, or if the stream is operating in object mode, `encoding` may be ignored.",
"name": "encoding",
"type": "string",
"desc": "If the chunk is a string, then `encoding` is the character encoding of that string. If chunk is a `Buffer`, or if the stream is operating in object mode, `encoding` may be ignored."
},
{
"textRaw": "`callback` {Function} Call this function (optionally with an error argument) when processing is complete for the supplied chunk.",
"name": "callback",
"type": "Function",
"desc": "Call this function (optionally with an error argument) when processing is complete for the supplied chunk."
}
]
}
],
"desc": "All Writable
stream implementations must provide a\nwritable._write()
and/or\nwritable._writev()
method to send data to the underlying\nresource.
Transform
streams provide their own implementation of the\nwritable._write()
.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Writable
class\nmethods only.
The callback
function must be called synchronously inside of\nwritable._write()
or asynchronously (i.e. different tick) to signal either\nthat the write completed successfully or failed with an error.\nThe first argument passed to the callback
must be the Error
object if the\ncall failed or null
if the write succeeded.
All calls to writable.write()
that occur between the time writable._write()
\nis called and the callback
is called will cause the written data to be\nbuffered. When the callback
is invoked, the stream might emit a 'drain'
\nevent. If a stream implementation is capable of processing multiple chunks of\ndata at once, the writable._writev()
method should be implemented.
If the decodeStrings
property is explicitly set to false
in the constructor\noptions, then chunk
will remain the same object that is passed to .write()
,\nand may be a string rather than a Buffer
. This is to support implementations\nthat have an optimized handling for certain string data encodings. In that case,\nthe encoding
argument will indicate the character encoding of the string.\nOtherwise, the encoding
argument can be safely ignored.
The writable._write()
method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Writable
class\nmethods only.
The writable._writev()
method may be implemented in addition or alternatively\nto writable._write()
in stream implementations that are capable of processing\nmultiple chunks of data at once. If implemented and if there is buffered data\nfrom previous writes, _writev()
will be called instead of _write()
.
The writable._writev()
method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
The _destroy()
method is called by writable.destroy()
.\nIt can be overridden by child classes but it must not be called directly.\nFurthermore, the callback
should not be mixed with async/await\nonce it is executed when a promise is resolved.
The _final()
method must not be called directly. It may be implemented\nby child classes, and if so, will be called by the internal Writable
\nclass methods only.
This optional function will be called before the stream closes, delaying the\n'finish'
event until callback
is called. This is useful to close resources\nor write buffered data before a stream ends.
Errors occurring during the processing of the writable._write()
,\nwritable._writev()
and writable._final()
methods must be propagated\nby invoking the callback and passing the error as the first argument.\nThrowing an Error
from within these methods or manually emitting an 'error'
\nevent results in undefined behavior.
If a Readable
stream pipes into a Writable
stream when Writable
emits an\nerror, the Readable
stream will be unpiped.
const { Writable } = require('node:stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n if (chunk.toString().indexOf('a') >= 0) {\n callback(new Error('chunk is invalid'));\n } else {\n callback();\n }\n },\n});\n
",
"type": "module",
"displayName": "Errors while writing"
},
{
"textRaw": "An example writable stream",
"name": "an_example_writable_stream",
"desc": "The following illustrates a rather simplistic (and somewhat pointless) custom\nWritable
stream implementation. While this specific Writable
stream instance\nis not of any real particular usefulness, the example illustrates each of the\nrequired elements of a custom Writable
stream instance:
const { Writable } = require('node:stream');\n\nclass MyWritable extends Writable {\n _write(chunk, encoding, callback) {\n if (chunk.toString().indexOf('a') >= 0) {\n callback(new Error('chunk is invalid'));\n } else {\n callback();\n }\n }\n}\n
",
"type": "module",
"displayName": "An example writable stream"
},
{
"textRaw": "Decoding buffers in a writable stream",
"name": "decoding_buffers_in_a_writable_stream",
"desc": "Decoding buffers is a common task, for instance, when using transformers whose\ninput is a string. This is not a trivial process when using multi-byte\ncharacters encoding, such as UTF-8. The following example shows how to decode\nmulti-byte strings using StringDecoder
and Writable
.
const { Writable } = require('node:stream');\nconst { StringDecoder } = require('node:string_decoder');\n\nclass StringWritable extends Writable {\n constructor(options) {\n super(options);\n this._decoder = new StringDecoder(options && options.defaultEncoding);\n this.data = '';\n }\n _write(chunk, encoding, callback) {\n if (encoding === 'buffer') {\n chunk = this._decoder.write(chunk);\n }\n this.data += chunk;\n callback();\n }\n _final(callback) {\n this.data += this._decoder.end();\n callback();\n }\n}\n\nconst euro = [[0xE2, 0x82], [0xAC]].map(Buffer.from);\nconst w = new StringWritable();\n\nw.write('currency: ');\nw.write(euro[0]);\nw.end(euro[1]);\n\nconsole.log(w.data); // currency: €\n
",
"type": "module",
"displayName": "Decoding buffers in a writable stream"
}
],
"type": "misc",
"displayName": "Implementing a writable stream"
},
{
"textRaw": "Implementing a readable stream",
"name": "implementing_a_readable_stream",
"desc": "The stream.Readable
class is extended to implement a Readable
stream.
Custom Readable
streams must call the new stream.Readable([options])
\nconstructor and implement the readable._read()
method.
const { Readable } = require('node:stream');\n\nclass MyReadable extends Readable {\n constructor(options) {\n // Calls the stream.Readable(options) constructor.\n super(options);\n // ...\n }\n}\n
\nOr, when using pre-ES6 style constructors:
\nconst { Readable } = require('node:stream');\nconst util = require('node:util');\n\nfunction MyReadable(options) {\n if (!(this instanceof MyReadable))\n return new MyReadable(options);\n Readable.call(this, options);\n}\nutil.inherits(MyReadable, Readable);\n
\nOr, using the simplified constructor approach:
\nconst { Readable } = require('node:stream');\n\nconst myReadable = new Readable({\n read(size) {\n // ...\n },\n});\n
\nCalling abort
on the AbortController
corresponding to the passed\nAbortSignal
will behave the same way as calling .destroy(new AbortError())
\non the readable created.
const { Readable } = require('node:stream');\nconst controller = new AbortController();\nconst read = new Readable({\n read(size) {\n // ...\n },\n signal: controller.signal,\n});\n// Later, abort the operation closing the stream\ncontroller.abort();\n
"
}
],
"methods": [
{
"textRaw": "`readable._construct(callback)`",
"type": "method",
"name": "_construct",
"meta": {
"added": [
"v15.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`callback` {Function} Call this function (optionally with an error argument) when the stream has finished initializing.",
"name": "callback",
"type": "Function",
"desc": "Call this function (optionally with an error argument) when the stream has finished initializing."
}
]
}
],
"desc": "The _construct()
method MUST NOT be called directly. It may be implemented\nby child classes, and if so, will be called by the internal Readable
\nclass methods only.
This optional function will be scheduled in the next tick by the stream\nconstructor, delaying any _read()
and _destroy()
calls until callback
is\ncalled. This is useful to initialize state or asynchronously initialize\nresources before the stream can be used.
const { Readable } = require('node:stream');\nconst fs = require('node:fs');\n\nclass ReadStream extends Readable {\n constructor(filename) {\n super();\n this.filename = filename;\n this.fd = null;\n }\n _construct(callback) {\n fs.open(this.filename, (err, fd) => {\n if (err) {\n callback(err);\n } else {\n this.fd = fd;\n callback();\n }\n });\n }\n _read(n) {\n const buf = Buffer.alloc(n);\n fs.read(this.fd, buf, 0, n, null, (err, bytesRead) => {\n if (err) {\n this.destroy(err);\n } else {\n this.push(bytesRead > 0 ? buf.slice(0, bytesRead) : null);\n }\n });\n }\n _destroy(err, callback) {\n if (this.fd) {\n fs.close(this.fd, (er) => callback(er || err));\n } else {\n callback(err);\n }\n }\n}\n
"
},
{
"textRaw": "`readable._read(size)`",
"type": "method",
"name": "_read",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`size` {number} Number of bytes to read asynchronously",
"name": "size",
"type": "number",
"desc": "Number of bytes to read asynchronously"
}
]
}
],
"desc": "This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Readable
class\nmethods only.
All Readable
stream implementations must provide an implementation of the\nreadable._read()
method to fetch data from the underlying resource.
When readable._read()
is called, if data is available from the resource,\nthe implementation should begin pushing that data into the read queue using the\nthis.push(dataChunk)
method. _read()
will be called again\nafter each call to this.push(dataChunk)
once the stream is\nready to accept more data. _read()
may continue reading from the resource and\npushing data until readable.push()
returns false
. Only when _read()
is\ncalled again after it has stopped should it resume pushing additional data into\nthe queue.
Once the readable._read()
method has been called, it will not be called\nagain until more data is pushed through the readable.push()
\nmethod. Empty data such as empty buffers and strings will not cause\nreadable._read()
to be called.
The size
argument is advisory. For implementations where a \"read\" is a\nsingle operation that returns data can use the size
argument to determine how\nmuch data to fetch. Other implementations may ignore this argument and simply\nprovide data whenever it becomes available. There is no need to \"wait\" until\nsize
bytes are available before calling stream.push(chunk)
.
The readable._read()
method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
The _destroy()
method is called by readable.destroy()
.\nIt can be overridden by child classes but it must not be called directly.
When chunk
is a Buffer
, Uint8Array
, or string
, the chunk
of data will\nbe added to the internal queue for users of the stream to consume.\nPassing chunk
as null
signals the end of the stream (EOF), after which no\nmore data can be written.
When the Readable
is operating in paused mode, the data added with\nreadable.push()
can be read out by calling the\nreadable.read()
method when the 'readable'
event is\nemitted.
When the Readable
is operating in flowing mode, the data added with\nreadable.push()
will be delivered by emitting a 'data'
event.
The readable.push()
method is designed to be as flexible as possible. For\nexample, when wrapping a lower-level source that provides some form of\npause/resume mechanism, and a data callback, the low-level source can be wrapped\nby the custom Readable
instance:
// `_source` is an object with readStop() and readStart() methods,\n// and an `ondata` member that gets called when it has data, and\n// an `onend` member that gets called when the data is over.\n\nclass SourceWrapper extends Readable {\n constructor(options) {\n super(options);\n\n this._source = getLowLevelSourceObject();\n\n // Every time there's data, push it into the internal buffer.\n this._source.ondata = (chunk) => {\n // If push() returns false, then stop reading from source.\n if (!this.push(chunk))\n this._source.readStop();\n };\n\n // When the source ends, push the EOF-signaling `null` chunk.\n this._source.onend = () => {\n this.push(null);\n };\n }\n // _read() will be called when the stream wants to pull more data in.\n // The advisory size argument is ignored in this case.\n _read(size) {\n this._source.readStart();\n }\n}\n
\nThe readable.push()
method is used to push the content\ninto the internal buffer. It can be driven by the readable._read()
method.
For streams not operating in object mode, if the chunk
parameter of\nreadable.push()
is undefined
, it will be treated as empty string or\nbuffer. See readable.push('')
for more information.
Errors occurring during processing of the readable._read()
must be\npropagated through the readable.destroy(err)
method.\nThrowing an Error
from within readable._read()
or manually emitting an\n'error'
event results in undefined behavior.
const { Readable } = require('node:stream');\n\nconst myReadable = new Readable({\n read(size) {\n const err = checkSomeErrorCondition();\n if (err) {\n this.destroy(err);\n } else {\n // Do some work.\n }\n },\n});\n
",
"type": "module",
"displayName": "Errors while reading"
}
],
"examples": [
{
"textRaw": "An example counting stream",
"name": "An example counting stream",
"type": "example",
"desc": "The following is a basic example of a Readable
stream that emits the numerals\nfrom 1 to 1,000,000 in ascending order, and then ends.
const { Readable } = require('node:stream');\n\nclass Counter extends Readable {\n constructor(opt) {\n super(opt);\n this._max = 1000000;\n this._index = 1;\n }\n\n _read() {\n const i = this._index++;\n if (i > this._max)\n this.push(null);\n else {\n const str = String(i);\n const buf = Buffer.from(str, 'ascii');\n this.push(buf);\n }\n }\n}\n
"
}
],
"type": "misc",
"displayName": "Implementing a readable stream"
},
{
"textRaw": "Implementing a duplex stream",
"name": "implementing_a_duplex_stream",
"desc": "A Duplex
stream is one that implements both Readable
and\nWritable
, such as a TCP socket connection.
Because JavaScript does not have support for multiple inheritance, the\nstream.Duplex
class is extended to implement a Duplex
stream (as opposed\nto extending the stream.Readable
and stream.Writable
classes).
The stream.Duplex
class prototypically inherits from stream.Readable
and\nparasitically from stream.Writable
, but instanceof
will work properly for\nboth base classes due to overriding Symbol.hasInstance
on\nstream.Writable
.
Custom Duplex
streams must call the new stream.Duplex([options])
\nconstructor and implement both the readable._read()
and\nwritable._write()
methods.
const { Duplex } = require('node:stream');\n\nclass MyDuplex extends Duplex {\n constructor(options) {\n super(options);\n // ...\n }\n}\n
\nOr, when using pre-ES6 style constructors:
\nconst { Duplex } = require('node:stream');\nconst util = require('node:util');\n\nfunction MyDuplex(options) {\n if (!(this instanceof MyDuplex))\n return new MyDuplex(options);\n Duplex.call(this, options);\n}\nutil.inherits(MyDuplex, Duplex);\n
\nOr, using the simplified constructor approach:
\nconst { Duplex } = require('node:stream');\n\nconst myDuplex = new Duplex({\n read(size) {\n // ...\n },\n write(chunk, encoding, callback) {\n // ...\n },\n});\n
\nWhen using pipeline:
\nconst { Transform, pipeline } = require('node:stream');\nconst fs = require('node:fs');\n\npipeline(\n fs.createReadStream('object.json')\n .setEncoding('utf8'),\n new Transform({\n decodeStrings: false, // Accept string input rather than Buffers\n construct(callback) {\n this.data = '';\n callback();\n },\n transform(chunk, encoding, callback) {\n this.data += chunk;\n callback();\n },\n flush(callback) {\n try {\n // Make sure is valid json.\n JSON.parse(this.data);\n this.push(this.data);\n callback();\n } catch (err) {\n callback(err);\n }\n },\n }),\n fs.createWriteStream('valid-object.json'),\n (err) => {\n if (err) {\n console.error('failed', err);\n } else {\n console.log('completed');\n }\n },\n);\n
"
}
],
"modules": [
{
"textRaw": "An example duplex stream",
"name": "an_example_duplex_stream",
"desc": "The following illustrates a simple example of a Duplex
stream that wraps a\nhypothetical lower-level source object to which data can be written, and\nfrom which data can be read, albeit using an API that is not compatible with\nNode.js streams.\nThe following illustrates a simple example of a Duplex
stream that buffers\nincoming written data via the Writable
interface that is read back out\nvia the Readable
interface.
const { Duplex } = require('node:stream');\nconst kSource = Symbol('source');\n\nclass MyDuplex extends Duplex {\n constructor(source, options) {\n super(options);\n this[kSource] = source;\n }\n\n _write(chunk, encoding, callback) {\n // The underlying source only deals with strings.\n if (Buffer.isBuffer(chunk))\n chunk = chunk.toString();\n this[kSource].writeSomeData(chunk);\n callback();\n }\n\n _read(size) {\n this[kSource].fetchSomeData(size, (data, encoding) => {\n this.push(Buffer.from(data, encoding));\n });\n }\n}\n
\nThe most important aspect of a Duplex
stream is that the Readable
and\nWritable
sides operate independently of one another despite co-existing within\na single object instance.
For Duplex
streams, objectMode
can be set exclusively for either the\nReadable
or Writable
side using the readableObjectMode
and\nwritableObjectMode
options respectively.
In the following example, for instance, a new Transform
stream (which is a\ntype of Duplex
stream) is created that has an object mode Writable
side\nthat accepts JavaScript numbers that are converted to hexadecimal strings on\nthe Readable
side.
const { Transform } = require('node:stream');\n\n// All Transform streams are also Duplex Streams.\nconst myTransform = new Transform({\n writableObjectMode: true,\n\n transform(chunk, encoding, callback) {\n // Coerce the chunk to a number if necessary.\n chunk |= 0;\n\n // Transform the chunk into something else.\n const data = chunk.toString(16);\n\n // Push the data onto the readable queue.\n callback(null, '0'.repeat(data.length % 2) + data);\n },\n});\n\nmyTransform.setEncoding('ascii');\nmyTransform.on('data', (chunk) => console.log(chunk));\n\nmyTransform.write(1);\n// Prints: 01\nmyTransform.write(10);\n// Prints: 0a\nmyTransform.write(100);\n// Prints: 64\n
",
"type": "module",
"displayName": "Object mode duplex streams"
}
],
"type": "misc",
"displayName": "Implementing a duplex stream"
},
{
"textRaw": "Implementing a transform stream",
"name": "implementing_a_transform_stream",
"desc": "A Transform
stream is a Duplex
stream where the output is computed\nin some way from the input. Examples include zlib streams or crypto\nstreams that compress, encrypt, or decrypt data.
There is no requirement that the output be the same size as the input, the same\nnumber of chunks, or arrive at the same time. For example, a Hash
stream will\nonly ever have a single chunk of output which is provided when the input is\nended. A zlib
stream will produce output that is either much smaller or much\nlarger than its input.
The stream.Transform
class is extended to implement a Transform
stream.
The stream.Transform
class prototypically inherits from stream.Duplex
and\nimplements its own versions of the writable._write()
and\nreadable._read()
methods. Custom Transform
implementations must\nimplement the transform._transform()
method and may\nalso implement the transform._flush()
method.
Care must be taken when using Transform
streams in that data written to the\nstream can cause the Writable
side of the stream to become paused if the\noutput on the Readable
side is not consumed.
const { Transform } = require('node:stream');\n\nclass MyTransform extends Transform {\n constructor(options) {\n super(options);\n // ...\n }\n}\n
\nOr, when using pre-ES6 style constructors:
\nconst { Transform } = require('node:stream');\nconst util = require('node:util');\n\nfunction MyTransform(options) {\n if (!(this instanceof MyTransform))\n return new MyTransform(options);\n Transform.call(this, options);\n}\nutil.inherits(MyTransform, Transform);\n
\nOr, using the simplified constructor approach:
\nconst { Transform } = require('node:stream');\n\nconst myTransform = new Transform({\n transform(chunk, encoding, callback) {\n // ...\n },\n});\n
"
}
],
"events": [
{
"textRaw": "Event: `'end'`",
"type": "event",
"name": "end",
"params": [],
"desc": "The 'end'
event is from the stream.Readable
class. The 'end'
event is\nemitted after all data has been output, which occurs after the callback in\ntransform._flush()
has been called. In the case of an error,\n'end'
should not be emitted.
The 'finish'
event is from the stream.Writable
class. The 'finish'
\nevent is emitted after stream.end()
is called and all chunks\nhave been processed by stream._transform()
. In the case\nof an error, 'finish'
should not be emitted.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Readable
class\nmethods only.
In some cases, a transform operation may need to emit an additional bit of\ndata at the end of the stream. For example, a zlib
compression stream will\nstore an amount of internal state used to optimally compress the output. When\nthe stream ends, however, that additional data needs to be flushed so that the\ncompressed data will be complete.
Custom Transform
implementations may implement the transform._flush()
\nmethod. This will be called when there is no more written data to be consumed,\nbut before the 'end'
event is emitted signaling the end of the\nReadable
stream.
Within the transform._flush()
implementation, the transform.push()
method\nmay be called zero or more times, as appropriate. The callback
function must\nbe called when the flush operation is complete.
The transform._flush()
method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Readable
class\nmethods only.
All Transform
stream implementations must provide a _transform()
\nmethod to accept input and produce output. The transform._transform()
\nimplementation handles the bytes being written, computes an output, then passes\nthat output off to the readable portion using the transform.push()
method.
The transform.push()
method may be called zero or more times to generate\noutput from a single input chunk, depending on how much is to be output\nas a result of the chunk.
It is possible that no output is generated from any given chunk of input data.
\nThe callback
function must be called only when the current chunk is completely\nconsumed. The first argument passed to the callback
must be an Error
object\nif an error occurred while processing the input or null
otherwise. If a second\nargument is passed to the callback
, it will be forwarded on to the\ntransform.push()
method, but only if the first argument is falsy. In other\nwords, the following are equivalent:
transform.prototype._transform = function(data, encoding, callback) {\n this.push(data);\n callback();\n};\n\ntransform.prototype._transform = function(data, encoding, callback) {\n callback(null, data);\n};\n
\nThe transform._transform()
method is prefixed with an underscore because it\nis internal to the class that defines it, and should never be called directly by\nuser programs.
transform._transform()
is never called in parallel; streams implement a\nqueue mechanism, and to receive the next chunk, callback
must be\ncalled, either synchronously or asynchronously.
The stream.PassThrough
class is a trivial implementation of a Transform
\nstream that simply passes the input bytes across to the output. Its purpose is\nprimarily for examples and testing, but there are some use cases where\nstream.PassThrough
is useful as a building block for novel sorts of streams.
With the support of async generators and iterators in JavaScript, async\ngenerators are effectively a first-class language-level stream construct at\nthis point.
\nSome common interop cases of using Node.js streams with async generators\nand async iterators are provided below.
", "modules": [ { "textRaw": "Consuming readable streams with async iterators", "name": "consuming_readable_streams_with_async_iterators", "desc": "(async function() {\n for await (const chunk of readable) {\n console.log(chunk);\n }\n})();\n
\nAsync iterators register a permanent error handler on the stream to prevent any\nunhandled post-destroy errors.
", "type": "module", "displayName": "Consuming readable streams with async iterators" }, { "textRaw": "Creating readable streams with async generators", "name": "creating_readable_streams_with_async_generators", "desc": "A Node.js readable stream can be created from an asynchronous generator using\nthe Readable.from()
utility method:
const { Readable } = require('node:stream');\n\nconst ac = new AbortController();\nconst signal = ac.signal;\n\nasync function * generate() {\n yield 'a';\n await someLongRunningFn({ signal });\n yield 'b';\n yield 'c';\n}\n\nconst readable = Readable.from(generate());\nreadable.on('close', () => {\n ac.abort();\n});\n\nreadable.on('data', (chunk) => {\n console.log(chunk);\n});\n
",
"type": "module",
"displayName": "Creating readable streams with async generators"
}
],
"miscs": [
{
"textRaw": "Piping to writable streams from async iterators",
"name": "Piping to writable streams from async iterators",
"type": "misc",
"desc": "When writing to a writable stream from an async iterator, ensure correct\nhandling of backpressure and errors. stream.pipeline()
abstracts away\nthe handling of backpressure and backpressure-related errors:
const fs = require('node:fs');\nconst { pipeline } = require('node:stream');\nconst { pipeline: pipelinePromise } = require('node:stream/promises');\n\nconst writable = fs.createWriteStream('./file');\n\nconst ac = new AbortController();\nconst signal = ac.signal;\n\nconst iterator = createIterator({ signal });\n\n// Callback Pattern\npipeline(iterator, writable, (err, value) => {\n if (err) {\n console.error(err);\n } else {\n console.log(value, 'value returned');\n }\n}).on('close', () => {\n ac.abort();\n});\n\n// Promise Pattern\npipelinePromise(iterator, writable)\n .then((value) => {\n console.log(value, 'value returned');\n })\n .catch((err) => {\n console.error(err);\n ac.abort();\n });\n
"
}
],
"type": "misc",
"displayName": "Streams compatibility with async generators and async iterators"
},
{
"textRaw": "Compatibility with older Node.js versions",
"name": "Compatibility with older Node.js versions",
"type": "misc",
"desc": "Prior to Node.js 0.10, the Readable
stream interface was simpler, but also\nless powerful and less useful.
stream.read()
method,\n'data'
events would begin emitting immediately. Applications that\nwould need to perform some amount of work to decide how to handle data\nwere required to store read data into buffers so the data would not be lost.stream.pause()
method was advisory, rather than\nguaranteed. This meant that it was still necessary to be prepared to receive\n'data'
events even when the stream was in a paused state.In Node.js 0.10, the Readable
class was added. For backward\ncompatibility with older Node.js programs, Readable
streams switch into\n\"flowing mode\" when a 'data'
event handler is added, or when the\nstream.resume()
method is called. The effect is that, even\nwhen not using the new stream.read()
method and\n'readable'
event, it is no longer necessary to worry about losing\n'data'
chunks.
While most applications will continue to function normally, this introduces an\nedge case in the following conditions:
\n'data'
event listener is added.stream.resume()
method is never called.For example, consider the following code:
\n// WARNING! BROKEN!\nnet.createServer((socket) => {\n\n // We add an 'end' listener, but never consume the data.\n socket.on('end', () => {\n // It will never get here.\n socket.end('The message was received but was not processed.\\n');\n });\n\n}).listen(1337);\n
\nPrior to Node.js 0.10, the incoming message data would be simply discarded.\nHowever, in Node.js 0.10 and beyond, the socket remains paused forever.
\nThe workaround in this situation is to call the\nstream.resume()
method to begin the flow of data:
// Workaround.\nnet.createServer((socket) => {\n socket.on('end', () => {\n socket.end('The message was received but was not processed.\\n');\n });\n\n // Start the flow of data, discarding it.\n socket.resume();\n}).listen(1337);\n
\nIn addition to new Readable
streams switching into flowing mode,\npre-0.10 style streams can be wrapped in a Readable
class using the\nreadable.wrap()
method.
The use of readable.setEncoding()
will change the behavior of how the\nhighWaterMark
operates in non-object mode.
Typically, the size of the current buffer is measured against the\nhighWaterMark
in bytes. However, after setEncoding()
is called, the\ncomparison function will begin to measure the buffer's size in characters.
This is not a problem in common cases with latin1
or ascii
. But it is\nadvised to be mindful about this behavior when working with strings that could\ncontain multi-byte characters.
There are some cases where it is necessary to trigger a refresh of the\nunderlying readable stream mechanisms, without actually consuming any\ndata. In such cases, it is possible to call readable.read(0)
, which will\nalways return null
.
If the internal read buffer is below the highWaterMark
, and the\nstream is not currently reading, then calling stream.read(0)
will trigger\na low-level stream._read()
call.
While most applications will almost never need to do this, there are\nsituations within Node.js where this is done, particularly in the\nReadable
stream class internals.
Use of readable.push('')
is not recommended.
Pushing a zero-byte string, Buffer
, or Uint8Array
to a stream that is not in\nobject mode has an interesting side effect. Because it is a call to\nreadable.push()
, the call will end the reading process.\nHowever, because the argument is an empty string, no data is added to the\nreadable buffer so there is nothing for a user to consume.
Source Code: lib/string_decoder.js
\nThe node:string_decoder
module provides an API for decoding Buffer
objects\ninto strings in a manner that preserves encoded multi-byte UTF-8 and UTF-16\ncharacters. It can be accessed using:
const { StringDecoder } = require('node:string_decoder');\n
\nThe following example shows the basic use of the StringDecoder
class.
const { StringDecoder } = require('node:string_decoder');\nconst decoder = new StringDecoder('utf8');\n\nconst cent = Buffer.from([0xC2, 0xA2]);\nconsole.log(decoder.write(cent)); // Prints: ¢\n\nconst euro = Buffer.from([0xE2, 0x82, 0xAC]);\nconsole.log(decoder.write(euro)); // Prints: €\n
\nWhen a Buffer
instance is written to the StringDecoder
instance, an\ninternal buffer is used to ensure that the decoded string does not contain\nany incomplete multibyte characters. These are held in the buffer until the\nnext call to stringDecoder.write()
or until stringDecoder.end()
is called.
In the following example, the three UTF-8 encoded bytes of the European Euro\nsymbol (€
) are written over three separate operations:
const { StringDecoder } = require('node:string_decoder');\nconst decoder = new StringDecoder('utf8');\n\ndecoder.write(Buffer.from([0xE2]));\ndecoder.write(Buffer.from([0x82]));\nconsole.log(decoder.end(Buffer.from([0xAC]))); // Prints: €\n
",
"classes": [
{
"textRaw": "Class: `StringDecoder`",
"type": "class",
"name": "StringDecoder",
"methods": [
{
"textRaw": "`stringDecoder.end([buffer])`",
"type": "method",
"name": "end",
"meta": {
"added": [
"v0.9.3"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`buffer` {string|Buffer|TypedArray|DataView} The bytes to decode.",
"name": "buffer",
"type": "string|Buffer|TypedArray|DataView",
"desc": "The bytes to decode."
}
]
}
],
"desc": "Returns any remaining input stored in the internal buffer as a string. Bytes\nrepresenting incomplete UTF-8 and UTF-16 characters will be replaced with\nsubstitution characters appropriate for the character encoding.
\nIf the buffer
argument is provided, one final call to stringDecoder.write()
\nis performed before returning the remaining input.\nAfter end()
is called, the stringDecoder
object can be reused for new input.
Returns a decoded string, ensuring that any incomplete multibyte characters at\nthe end of the Buffer
, or TypedArray
, or DataView
are omitted from the\nreturned string and stored in an internal buffer for the next call to\nstringDecoder.write()
or stringDecoder.end()
.
Creates a new StringDecoder
instance.
Source Code: lib/test.js
\nThe node:test
module facilitates the creation of JavaScript tests.\nTo access it:
import test from 'node:test';\n
\nconst test = require('node:test');\n
\nThis module is only available under the node:
scheme. The following will not\nwork:
import test from 'test';\n
\nconst test = require('test');\n
\nTests created via the test
module consist of a single function that is\nprocessed in one of three ways:
Promise
that is considered failing if the\nPromise
rejects, and is considered passing if the Promise
fulfills.Promise
, the test will fail.The following example illustrates how tests are written using the\ntest
module.
test('synchronous passing test', (t) => {\n // This test passes because it does not throw an exception.\n assert.strictEqual(1, 1);\n});\n\ntest('synchronous failing test', (t) => {\n // This test fails because it throws an exception.\n assert.strictEqual(1, 2);\n});\n\ntest('asynchronous passing test', async (t) => {\n // This test passes because the Promise returned by the async\n // function is settled and not rejected.\n assert.strictEqual(1, 1);\n});\n\ntest('asynchronous failing test', async (t) => {\n // This test fails because the Promise returned by the async\n // function is rejected.\n assert.strictEqual(1, 2);\n});\n\ntest('failing test using Promises', (t) => {\n // Promises can be used directly as well.\n return new Promise((resolve, reject) => {\n setImmediate(() => {\n reject(new Error('this will cause the test to fail'));\n });\n });\n});\n\ntest('callback passing test', (t, done) => {\n // done() is the callback function. When the setImmediate() runs, it invokes\n // done() with no arguments.\n setImmediate(done);\n});\n\ntest('callback failing test', (t, done) => {\n // When the setImmediate() runs, done() is invoked with an Error object and\n // the test fails.\n setImmediate(() => {\n done(new Error('callback failure'));\n });\n});\n
\nIf any tests fail, the process exit code is set to 1
.
The test context's test()
method allows subtests to be created.\nIt allows you to structure your tests in a hierarchical manner,\nwhere you can create nested tests within a larger test.\nThis method behaves identically to the top level test()
function.\nThe following example demonstrates the creation of a\ntop level test with two subtests.
test('top level test', async (t) => {\n await t.test('subtest 1', (t) => {\n assert.strictEqual(1, 1);\n });\n\n await t.test('subtest 2', (t) => {\n assert.strictEqual(2, 2);\n });\n});\n
\n\n\nNote:
\nbeforeEach
andafterEach
hooks are triggered\nbetween each subtest execution.
In this example, await
is used to ensure that both subtests have completed.\nThis is necessary because parent tests do not wait for their subtests to\ncomplete, unlike tests created with the describe
and it
syntax.\nAny subtests that are still outstanding when their parent finishes\nare cancelled and treated as failures. Any subtest failures cause the parent\ntest to fail.
Individual tests can be skipped by passing the skip
option to the test, or by\ncalling the test context's skip()
method as shown in the\nfollowing example.
// The skip option is used, but no message is provided.\ntest('skip option', { skip: true }, (t) => {\n // This code is never executed.\n});\n\n// The skip option is used, and a message is provided.\ntest('skip option with message', { skip: 'this is skipped' }, (t) => {\n // This code is never executed.\n});\n\ntest('skip() method', (t) => {\n // Make sure to return here as well if the test contains additional logic.\n t.skip();\n});\n\ntest('skip() method with message', (t) => {\n // Make sure to return here as well if the test contains additional logic.\n t.skip('this is skipped');\n});\n
",
"type": "module",
"displayName": "Skipping tests"
},
{
"textRaw": "`describe`/`it` syntax",
"name": "`describe`/`it`_syntax",
"desc": "Running tests can also be done using describe
to declare a suite\nand it
to declare a test.\nA suite is used to organize and group related tests together.\nit
is a shorthand for test()
.
describe('A thing', () => {\n it('should work', () => {\n assert.strictEqual(1, 1);\n });\n\n it('should be ok', () => {\n assert.strictEqual(2, 2);\n });\n\n describe('a nested thing', () => {\n it('should work', () => {\n assert.strictEqual(3, 3);\n });\n });\n});\n
\ndescribe
and it
are imported from the node:test
module.
import { describe, it } from 'node:test';\n
\nconst { describe, it } = require('node:test');\n
",
"type": "module",
"displayName": "`describe`/`it` syntax"
},
{
"textRaw": "`only` tests",
"name": "`only`_tests",
"desc": "If Node.js is started with the --test-only
command-line option, it is\npossible to skip all top level tests except for a selected subset by passing\nthe only
option to the tests that should be run. When a test with the only
\noption set is run, all subtests are also run. The test context's runOnly()
\nmethod can be used to implement the same behavior at the subtest level.
// Assume Node.js is run with the --test-only command-line option.\n// The 'only' option is set, so this test is run.\ntest('this test is run', { only: true }, async (t) => {\n // Within this test, all subtests are run by default.\n await t.test('running subtest');\n\n // The test context can be updated to run subtests with the 'only' option.\n t.runOnly(true);\n await t.test('this subtest is now skipped');\n await t.test('this subtest is run', { only: true });\n\n // Switch the context back to execute all tests.\n t.runOnly(false);\n await t.test('this subtest is now run');\n\n // Explicitly do not run these tests.\n await t.test('skipped subtest 3', { only: false });\n await t.test('skipped subtest 4', { skip: true });\n});\n\n// The 'only' option is not set, so this test is skipped.\ntest('this test is not run', () => {\n // This code is not run.\n throw new Error('fail');\n});\n
",
"type": "module",
"displayName": "`only` tests"
},
{
"textRaw": "Filtering tests by name",
"name": "filtering_tests_by_name",
"desc": "The --test-name-pattern
command-line option can be used to only run tests\nwhose name matches the provided pattern. Test name patterns are interpreted as\nJavaScript regular expressions. The --test-name-pattern
option can be\nspecified multiple times in order to run nested tests. For each test that is\nexecuted, any corresponding test hooks, such as beforeEach()
, are also\nrun.
Given the following test file, starting Node.js with the\n--test-name-pattern=\"test [1-3]\"
option would cause the test runner to execute\ntest 1
, test 2
, and test 3
. If test 1
did not match the test name\npattern, then its subtests would not execute, despite matching the pattern. The\nsame set of tests could also be executed by passing --test-name-pattern
\nmultiple times (e.g. --test-name-pattern=\"test 1\"
,\n--test-name-pattern=\"test 2\"
, etc.).
test('test 1', async (t) => {\n await t.test('test 2');\n await t.test('test 3');\n});\n\ntest('Test 4', async (t) => {\n await t.test('Test 5');\n await t.test('test 6');\n});\n
\nTest name patterns can also be specified using regular expression literals. This\nallows regular expression flags to be used. In the previous example, starting\nNode.js with --test-name-pattern=\"/test [4-5]/i\"
would match Test 4
and\nTest 5
because the pattern is case-insensitive.
Test name patterns do not change the set of files that the test runner executes.
", "type": "module", "displayName": "Filtering tests by name" }, { "textRaw": "Extraneous asynchronous activity", "name": "extraneous_asynchronous_activity", "desc": "Once a test function finishes executing, the results are reported as quickly\nas possible while maintaining the order of the tests. However, it is possible\nfor the test function to generate asynchronous activity that outlives the test\nitself. The test runner handles this type of activity, but does not delay the\nreporting of test results in order to accommodate it.
\nIn the following example, a test completes with two setImmediate()
\noperations still outstanding. The first setImmediate()
attempts to create a\nnew subtest. Because the parent test has already finished and output its\nresults, the new subtest is immediately marked as failed, and reported later\nto the <TestsStream>.
The second setImmediate()
creates an uncaughtException
event.\nuncaughtException
and unhandledRejection
events originating from a completed\ntest are marked as failed by the test
module and reported as diagnostic\nwarnings at the top level by the <TestsStream>.
test('a test that creates asynchronous activity', (t) => {\n setImmediate(() => {\n t.test('subtest that is created too late', (t) => {\n throw new Error('error1');\n });\n });\n\n setImmediate(() => {\n throw new Error('error2');\n });\n\n // The test finishes after this line.\n});\n
",
"type": "module",
"displayName": "Extraneous asynchronous activity"
},
{
"textRaw": "Watch mode",
"name": "watch_mode",
"meta": {
"added": [
"v19.2.0",
"v18.13.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "The Node.js test runner supports running in watch mode by passing the --watch
flag:
node --test --watch\n
\nIn watch mode, the test runner will watch for changes to test files and\ntheir dependencies. When a change is detected, the test runner will\nrerun the tests affected by the change.\nThe test runner will continue to run until the process is terminated.
", "type": "module", "displayName": "Watch mode" }, { "textRaw": "Running tests from the command line", "name": "running_tests_from_the_command_line", "desc": "The Node.js test runner can be invoked from the command line by passing the\n--test
flag:
node --test\n
\nBy default Node.js will run all files matching these patterns:
\n**/*.test.?(c|m)js
**/*-test.?(c|m)js
**/*_test.?(c|m)js
**/test-*.?(c|m)js
**/test.?(c|m)js
**/test/**/*.?(c|m)js
Alternatively, one or more glob patterns can be provided as the\nfinal argument(s) to the Node.js command, as shown below.\nGlob patterns follow the behavior of glob(7)
.
node --test **/*.test.js **/*.spec.js\n
\nMatching files are executed as test files.\nMore information on the test file execution can be found\nin the test runner execution model section.
", "modules": [ { "textRaw": "Test runner execution model", "name": "test_runner_execution_model", "desc": "Each matching test file is executed in a separate child process. The maximum\nnumber of child processes running at any time is controlled by the\n--test-concurrency
flag. If the child process finishes with an exit code\nof 0, the test is considered passing. Otherwise, the test is considered to be a\nfailure. Test files must be executable by Node.js, but are not required to use\nthe node:test
module internally.
Each test file is executed as if it was a regular script. That is, if the test\nfile itself uses node:test
to define tests, all of those tests will be\nexecuted within a single application thread, regardless of the value of the\nconcurrency
option of test()
.
When Node.js is started with the --experimental-test-coverage
\ncommand-line flag, code coverage is collected and statistics are reported once\nall tests have completed. If the NODE_V8_COVERAGE
environment variable is\nused to specify a code coverage directory, the generated V8 coverage files are\nwritten to that directory. Node.js core modules and files within\nnode_modules/
directories are not included in the coverage report. If\ncoverage is enabled, the coverage report is sent to any test reporters via\nthe 'test:coverage'
event.
Coverage can be disabled on a series of lines using the following\ncomment syntax:
\n/* node:coverage disable */\nif (anAlwaysFalseCondition) {\n // Code in this branch will never be executed, but the lines are ignored for\n // coverage purposes. All lines following the 'disable' comment are ignored\n // until a corresponding 'enable' comment is encountered.\n console.log('this is never executed');\n}\n/* node:coverage enable */\n
\nCoverage can also be disabled for a specified number of lines. After the\nspecified number of lines, coverage will be automatically reenabled. If the\nnumber of lines is not explicitly provided, a single line is ignored.
\n/* node:coverage ignore next */\nif (anAlwaysFalseCondition) { console.log('this is never executed'); }\n\n/* node:coverage ignore next 3 */\nif (anAlwaysFalseCondition) {\n console.log('this is never executed');\n}\n
",
"modules": [
{
"textRaw": "Coverage reporters",
"name": "coverage_reporters",
"desc": "The tap and spec reporters will print a summary of the coverage statistics.\nThere is also an lcov reporter that will generate an lcov file which can be\nused as an in depth coverage report.
\nnode --test --experimental-test-coverage --test-reporter=lcov --test-reporter-destination=lcov.info\n
",
"type": "module",
"displayName": "Coverage reporters"
},
{
"textRaw": "Limitations",
"name": "limitations",
"desc": "The test runner's code coverage functionality has the following limitations,\nwhich will be addressed in a future Node.js release:
\nThe node:test
module supports mocking during testing via a top-level mock
\nobject. The following example creates a spy on a function that adds two numbers\ntogether. The spy is then used to assert that the function was called as\nexpected.
import assert from 'node:assert';\nimport { mock, test } from 'node:test';\n\ntest('spies on a function', () => {\n const sum = mock.fn((a, b) => {\n return a + b;\n });\n\n assert.strictEqual(sum.mock.calls.length, 0);\n assert.strictEqual(sum(3, 4), 7);\n assert.strictEqual(sum.mock.calls.length, 1);\n\n const call = sum.mock.calls[0];\n assert.deepStrictEqual(call.arguments, [3, 4]);\n assert.strictEqual(call.result, 7);\n assert.strictEqual(call.error, undefined);\n\n // Reset the globally tracked mocks.\n mock.reset();\n});\n
\n'use strict';\nconst assert = require('node:assert');\nconst { mock, test } = require('node:test');\n\ntest('spies on a function', () => {\n const sum = mock.fn((a, b) => {\n return a + b;\n });\n\n assert.strictEqual(sum.mock.calls.length, 0);\n assert.strictEqual(sum(3, 4), 7);\n assert.strictEqual(sum.mock.calls.length, 1);\n\n const call = sum.mock.calls[0];\n assert.deepStrictEqual(call.arguments, [3, 4]);\n assert.strictEqual(call.result, 7);\n assert.strictEqual(call.error, undefined);\n\n // Reset the globally tracked mocks.\n mock.reset();\n});\n
\nThe same mocking functionality is also exposed on the TestContext
object\nof each test. The following example creates a spy on an object method using the\nAPI exposed on the TestContext
. The benefit of mocking via the test context is\nthat the test runner will automatically restore all mocked functionality once\nthe test finishes.
test('spies on an object method', (t) => {\n const number = {\n value: 5,\n add(a) {\n return this.value + a;\n },\n };\n\n t.mock.method(number, 'add');\n assert.strictEqual(number.add.mock.calls.length, 0);\n assert.strictEqual(number.add(3), 8);\n assert.strictEqual(number.add.mock.calls.length, 1);\n\n const call = number.add.mock.calls[0];\n\n assert.deepStrictEqual(call.arguments, [3]);\n assert.strictEqual(call.result, 8);\n assert.strictEqual(call.target, undefined);\n assert.strictEqual(call.this, number);\n});\n
",
"modules": [
{
"textRaw": "Timers",
"name": "timers",
"desc": "Mocking timers is a technique commonly used in software testing to simulate and\ncontrol the behavior of timers, such as setInterval
and setTimeout
,\nwithout actually waiting for the specified time intervals.
Refer to the MockTimers
class for a full list of methods and features.
This allows developers to write more reliable and\npredictable tests for time-dependent functionality.
\nThe example below shows how to mock setTimeout
.\nUsing .enable({ apis: ['setTimeout'] });
\nit will mock the setTimeout
functions in the node:timers and\nnode:timers/promises modules,\nas well as from the Node.js global context.
Note: Destructuring functions such as\nimport { setTimeout } from 'node:timers'
\nis currently not supported by this API.
import assert from 'node:assert';\nimport { mock, test } from 'node:test';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', () => {\n const fn = mock.fn();\n\n // Optionally choose what to mock\n mock.timers.enable({ apis: ['setTimeout'] });\n setTimeout(fn, 9999);\n assert.strictEqual(fn.mock.callCount(), 0);\n\n // Advance in time\n mock.timers.tick(9999);\n assert.strictEqual(fn.mock.callCount(), 1);\n\n // Reset the globally tracked mocks.\n mock.timers.reset();\n\n // If you call reset mock instance, it will also reset timers instance\n mock.reset();\n});\n
\nconst assert = require('node:assert');\nconst { mock, test } = require('node:test');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', () => {\n const fn = mock.fn();\n\n // Optionally choose what to mock\n mock.timers.enable({ apis: ['setTimeout'] });\n setTimeout(fn, 9999);\n assert.strictEqual(fn.mock.callCount(), 0);\n\n // Advance in time\n mock.timers.tick(9999);\n assert.strictEqual(fn.mock.callCount(), 1);\n\n // Reset the globally tracked mocks.\n mock.timers.reset();\n\n // If you call reset mock instance, it'll also reset timers instance\n mock.reset();\n});\n
\nThe same mocking functionality is also exposed in the mock property on the TestContext
object\nof each test. The benefit of mocking via the test context is\nthat the test runner will automatically restore all mocked timers\nfunctionality once the test finishes.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout'] });\n setTimeout(fn, 9999);\n assert.strictEqual(fn.mock.callCount(), 0);\n\n // Advance in time\n context.mock.timers.tick(9999);\n assert.strictEqual(fn.mock.callCount(), 1);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout'] });\n setTimeout(fn, 9999);\n assert.strictEqual(fn.mock.callCount(), 0);\n\n // Advance in time\n context.mock.timers.tick(9999);\n assert.strictEqual(fn.mock.callCount(), 1);\n});\n
",
"type": "module",
"displayName": "Timers"
},
{
"textRaw": "Dates",
"name": "dates",
"desc": "The mock timers API also allows the mocking of the Date
object. This is a\nuseful feature for testing time-dependent functionality, or to simulate\ninternal calendar functions such as Date.now()
.
The dates implementation is also part of the MockTimers
class. Refer to it\nfor a full list of methods and features.
Note: Dates and timers are dependent when mocked together. This means that\nif you have both the Date
and setTimeout
mocked, advancing the time will\nalso advance the mocked date as they simulate a single internal clock.
The example below show how to mock the Date
object and obtain the current\nDate.now()
value.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks the Date object', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['Date'] });\n // If not specified, the initial date will be based on 0 in the UNIX epoch\n assert.strictEqual(Date.now(), 0);\n\n // Advance in time will also advance the date\n context.mock.timers.tick(9999);\n assert.strictEqual(Date.now(), 9999);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks the Date object', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['Date'] });\n // If not specified, the initial date will be based on 0 in the UNIX epoch\n assert.strictEqual(Date.now(), 0);\n\n // Advance in time will also advance the date\n context.mock.timers.tick(9999);\n assert.strictEqual(Date.now(), 9999);\n});\n
\nIf there is no initial epoch set, the initial date will be based on 0 in the\nUnix epoch. This is January 1st, 1970, 00:00:00 UTC. You can set an initial date\nby passing a now
property to the .enable()
method. This value will be used\nas the initial date for the mocked Date
object. It can either be a positive\ninteger, or another Date object.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks the Date object with initial time', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['Date'], now: 100 });\n assert.strictEqual(Date.now(), 100);\n\n // Advance in time will also advance the date\n context.mock.timers.tick(200);\n assert.strictEqual(Date.now(), 300);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks the Date object with initial time', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['Date'], now: 100 });\n assert.strictEqual(Date.now(), 100);\n\n // Advance in time will also advance the date\n context.mock.timers.tick(200);\n assert.strictEqual(Date.now(), 300);\n});\n
\nYou can use the .setTime()
method to manually move the mocked date to another\ntime. This method only accepts a positive integer.
Note: This method will execute any mocked timers that are in the past\nfrom the new time.
\nIn the below example we are setting a new time for the mocked date.
\nimport assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('sets the time of a date object', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['Date'], now: 100 });\n assert.strictEqual(Date.now(), 100);\n\n // Advance in time will also advance the date\n context.mock.timers.setTime(1000);\n context.mock.timers.tick(200);\n assert.strictEqual(Date.now(), 1200);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('sets the time of a date object', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['Date'], now: 100 });\n assert.strictEqual(Date.now(), 100);\n\n // Advance in time will also advance the date\n context.mock.timers.setTime(1000);\n context.mock.timers.tick(200);\n assert.strictEqual(Date.now(), 1200);\n});\n
\nIf you have any timer that's set to run in the past, it will be executed as if\nthe .tick()
method has been called. This is useful if you want to test\ntime-dependent functionality that's already in the past.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('runs timers as setTime passes ticks', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const fn = context.mock.fn();\n setTimeout(fn, 1000);\n\n context.mock.timers.setTime(800);\n // Timer is not executed as the time is not yet reached\n assert.strictEqual(fn.mock.callCount(), 0);\n assert.strictEqual(Date.now(), 800);\n\n context.mock.timers.setTime(1200);\n // Timer is executed as the time is now reached\n assert.strictEqual(fn.mock.callCount(), 1);\n assert.strictEqual(Date.now(), 1200);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('runs timers as setTime passes ticks', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const fn = context.mock.fn();\n setTimeout(fn, 1000);\n\n context.mock.timers.setTime(800);\n // Timer is not executed as the time is not yet reached\n assert.strictEqual(fn.mock.callCount(), 0);\n assert.strictEqual(Date.now(), 800);\n\n context.mock.timers.setTime(1200);\n // Timer is executed as the time is now reached\n assert.strictEqual(fn.mock.callCount(), 1);\n assert.strictEqual(Date.now(), 1200);\n});\n
\nUsing .runAll()
will execute all timers that are currently in the queue. This\nwill also advance the mocked date to the time of the last timer that was\nexecuted as if the time has passed.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('runs timers as setTime passes ticks', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const fn = context.mock.fn();\n setTimeout(fn, 1000);\n setTimeout(fn, 2000);\n setTimeout(fn, 3000);\n\n context.mock.timers.runAll();\n // All timers are executed as the time is now reached\n assert.strictEqual(fn.mock.callCount(), 3);\n assert.strictEqual(Date.now(), 3000);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('runs timers as setTime passes ticks', (context) => {\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const fn = context.mock.fn();\n setTimeout(fn, 1000);\n setTimeout(fn, 2000);\n setTimeout(fn, 3000);\n\n context.mock.timers.runAll();\n // All timers are executed as the time is now reached\n assert.strictEqual(fn.mock.callCount(), 3);\n assert.strictEqual(Date.now(), 3000);\n});\n
",
"type": "module",
"displayName": "Dates"
}
],
"type": "module",
"displayName": "Mocking"
},
{
"textRaw": "Test reporters",
"name": "test_reporters",
"meta": {
"added": [
"v19.6.0",
"v18.15.0"
],
"changes": [
{
"version": [
"v19.9.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47238",
"description": "Reporters are now exposed at `node:test/reporters`."
}
]
},
"desc": "The node:test
module supports passing --test-reporter
\nflags for the test runner to use a specific reporter.
The following built-reporters are supported:
\ntap
\nThe tap
reporter outputs the test results in the TAP format.
spec
\nThe spec
reporter outputs the test results in a human-readable format.
dot
\nThe dot
reporter outputs the test results in a compact format,\nwhere each passing test is represented by a .
,\nand each failing test is represented by a X
.
junit
\nThe junit reporter outputs test results in a jUnit XML format
lcov
\nThe lcov
reporter outputs test coverage when used with the\n--experimental-test-coverage
flag.
When stdout
is a TTY, the spec
reporter is used by default.\nOtherwise, the tap
reporter is used by default.
The exact output of these reporters is subject to change between versions of\nNode.js, and should not be relied on programmatically. If programmatic access\nto the test runner's output is required, use the events emitted by the\n<TestsStream>.
\nThe reporters are available via the node:test/reporters
module:
import { tap, spec, dot, junit, lcov } from 'node:test/reporters';\n
\nconst { tap, spec, dot, junit, lcov } = require('node:test/reporters');\n
",
"modules": [
{
"textRaw": "Custom reporters",
"name": "custom_reporters",
"desc": "--test-reporter
can be used to specify a path to custom reporter.\nA custom reporter is a module that exports a value\naccepted by stream.compose.\nReporters should transform events emitted by a <TestsStream>
Example of a custom reporter using <stream.Transform>:
\nimport { Transform } from 'node:stream';\n\nconst customReporter = new Transform({\n writableObjectMode: true,\n transform(event, encoding, callback) {\n switch (event.type) {\n case 'test:dequeue':\n callback(null, `test ${event.data.name} dequeued`);\n break;\n case 'test:enqueue':\n callback(null, `test ${event.data.name} enqueued`);\n break;\n case 'test:watch:drained':\n callback(null, 'test watch queue drained');\n break;\n case 'test:start':\n callback(null, `test ${event.data.name} started`);\n break;\n case 'test:pass':\n callback(null, `test ${event.data.name} passed`);\n break;\n case 'test:fail':\n callback(null, `test ${event.data.name} failed`);\n break;\n case 'test:plan':\n callback(null, 'test plan');\n break;\n case 'test:diagnostic':\n case 'test:stderr':\n case 'test:stdout':\n callback(null, event.data.message);\n break;\n case 'test:coverage': {\n const { totalLineCount } = event.data.summary.totals;\n callback(null, `total line count: ${totalLineCount}\\n`);\n break;\n }\n }\n },\n});\n\nexport default customReporter;\n
\nconst { Transform } = require('node:stream');\n\nconst customReporter = new Transform({\n writableObjectMode: true,\n transform(event, encoding, callback) {\n switch (event.type) {\n case 'test:dequeue':\n callback(null, `test ${event.data.name} dequeued`);\n break;\n case 'test:enqueue':\n callback(null, `test ${event.data.name} enqueued`);\n break;\n case 'test:watch:drained':\n callback(null, 'test watch queue drained');\n break;\n case 'test:start':\n callback(null, `test ${event.data.name} started`);\n break;\n case 'test:pass':\n callback(null, `test ${event.data.name} passed`);\n break;\n case 'test:fail':\n callback(null, `test ${event.data.name} failed`);\n break;\n case 'test:plan':\n callback(null, 'test plan');\n break;\n case 'test:diagnostic':\n case 'test:stderr':\n case 'test:stdout':\n callback(null, event.data.message);\n break;\n case 'test:coverage': {\n const { totalLineCount } = event.data.summary.totals;\n callback(null, `total line count: ${totalLineCount}\\n`);\n break;\n }\n }\n },\n});\n\nmodule.exports = customReporter;\n
\nExample of a custom reporter using a generator function:
\nexport default async function * customReporter(source) {\n for await (const event of source) {\n switch (event.type) {\n case 'test:dequeue':\n yield `test ${event.data.name} dequeued`;\n break;\n case 'test:enqueue':\n yield `test ${event.data.name} enqueued`;\n break;\n case 'test:watch:drained':\n yield 'test watch queue drained';\n break;\n case 'test:start':\n yield `test ${event.data.name} started\\n`;\n break;\n case 'test:pass':\n yield `test ${event.data.name} passed\\n`;\n break;\n case 'test:fail':\n yield `test ${event.data.name} failed\\n`;\n break;\n case 'test:plan':\n yield 'test plan';\n break;\n case 'test:diagnostic':\n case 'test:stderr':\n case 'test:stdout':\n yield `${event.data.message}\\n`;\n break;\n case 'test:coverage': {\n const { totalLineCount } = event.data.summary.totals;\n yield `total line count: ${totalLineCount}\\n`;\n break;\n }\n }\n }\n}\n
\nmodule.exports = async function * customReporter(source) {\n for await (const event of source) {\n switch (event.type) {\n case 'test:dequeue':\n yield `test ${event.data.name} dequeued`;\n break;\n case 'test:enqueue':\n yield `test ${event.data.name} enqueued`;\n break;\n case 'test:watch:drained':\n yield 'test watch queue drained';\n break;\n case 'test:start':\n yield `test ${event.data.name} started\\n`;\n break;\n case 'test:pass':\n yield `test ${event.data.name} passed\\n`;\n break;\n case 'test:fail':\n yield `test ${event.data.name} failed\\n`;\n break;\n case 'test:plan':\n yield 'test plan\\n';\n break;\n case 'test:diagnostic':\n case 'test:stderr':\n case 'test:stdout':\n yield `${event.data.message}\\n`;\n break;\n case 'test:coverage': {\n const { totalLineCount } = event.data.summary.totals;\n yield `total line count: ${totalLineCount}\\n`;\n break;\n }\n }\n }\n};\n
\nThe value provided to --test-reporter
should be a string like one used in an\nimport()
in JavaScript code, or a value provided for --import
.
The --test-reporter
flag can be specified multiple times to report test\nresults in several formats. In this situation\nit is required to specify a destination for each reporter\nusing --test-reporter-destination
.\nDestination can be stdout
, stderr
, or a file path.\nReporters and destinations are paired according\nto the order they were specified.
In the following example, the spec
reporter will output to stdout
,\nand the dot
reporter will output to file.txt
:
node --test-reporter=spec --test-reporter=dot --test-reporter-destination=stdout --test-reporter-destination=file.txt\n
\nWhen a single reporter is specified, the destination will default to stdout
,\nunless a destination is explicitly provided.
Note: shard
is used to horizontally parallelize test running across\nmachines or processes, ideal for large-scale executions across varied\nenvironments. It's incompatible with watch
mode, tailored for rapid\ncode iteration by automatically rerunning tests on file changes.
import { tap } from 'node:test/reporters';\nimport { run } from 'node:test';\nimport process from 'node:process';\nimport path from 'node:path';\n\nrun({ files: [path.resolve('./tests/test.js')] })\n .on('test:fail', () => {\n process.exitCode = 1;\n })\n .compose(tap)\n .pipe(process.stdout);\n
\nconst { tap } = require('node:test/reporters');\nconst { run } = require('node:test');\nconst path = require('node:path');\n\nrun({ files: [path.resolve('./tests/test.js')] })\n .on('test:fail', () => {\n process.exitCode = 1;\n })\n .compose(tap)\n .pipe(process.stdout);\n
"
},
{
"textRaw": "`test([name][, options][, fn])`",
"type": "method",
"name": "test",
"meta": {
"added": [
"v18.0.0",
"v16.17.0"
],
"changes": [
{
"version": [
"v20.2.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47909",
"description": "Added the `skip`, `todo`, and `only` shorthands."
},
{
"version": [
"v18.8.0",
"v16.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/43554",
"description": "Add a `signal` option."
},
{
"version": [
"v18.7.0",
"v16.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/43505",
"description": "Add a `timeout` option."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfilled with `undefined` once the test completes, or immediately if the test runs within [`describe()`][].",
"name": "return",
"type": "Promise",
"desc": "Fulfilled with `undefined` once the test completes, or immediately if the test runs within [`describe()`][]."
},
"params": [
{
"textRaw": "`name` {string} The name of the test, which is displayed when reporting test results. **Default:** The `name` property of `fn`, or `'The test()
function is the value imported from the test
module. Each\ninvocation of this function results in reporting the test to the <TestsStream>.
The TestContext
object passed to the fn
argument can be used to perform\nactions related to the current test. Examples include skipping the test, adding\nadditional diagnostic information, or creating subtests.
test()
returns a Promise
that fulfills once the test completes.\nif test()
is called within a describe()
block, it fulfills immediately.\nThe return value can usually be discarded for top level tests.\nHowever, the return value from subtests should be used to prevent the parent\ntest from finishing first and cancelling the subtest\nas shown in the following example.
test('top level test', async (t) => {\n // The setTimeout() in the following subtest would cause it to outlive its\n // parent test if 'await' is removed on the next line. Once the parent test\n // completes, it will cancel any outstanding subtests.\n await t.test('longer running subtest', async (t) => {\n return new Promise((resolve, reject) => {\n setTimeout(resolve, 1000);\n });\n });\n});\n
\nThe timeout
option can be used to fail the test if it takes longer than\ntimeout
milliseconds to complete. However, it is not a reliable mechanism for\ncanceling tests because a running test might block the application thread and\nthus prevent the scheduled cancellation.
Shorthand for skipping a test,\nsame as test([name], { skip: true }[, fn])
.
Shorthand for marking a test as TODO
,\nsame as test([name], { todo: true }[, fn])
.
Shorthand for marking a test as only
,\nsame as test([name], { only: true }[, fn])
.
The describe()
function imported from the node:test
module. Each\ninvocation of this function results in the creation of a Subtest.\nAfter invocation of top level describe
functions,\nall top level tests and suites will execute.
Shorthand for skipping a suite, same as describe([name], { skip: true }[, fn])
.
Shorthand for marking a suite as TODO
, same as\ndescribe([name], { todo: true }[, fn])
.
Shorthand for marking a suite as only
, same as\ndescribe([name], { only: true }[, fn])
.
Shorthand for test()
.
The it()
function is imported from the node:test
module.
Shorthand for skipping a test,\nsame as it([name], { skip: true }[, fn])
.
Shorthand for marking a test as TODO
,\nsame as it([name], { todo: true }[, fn])
.
Shorthand for marking a test as only
,\nsame as it([name], { only: true }[, fn])
.
This function is used to create a hook running before running a suite.
\ndescribe('tests', async () => {\n before(() => console.log('about to run some test'));\n it('is a subtest', () => {\n assert.ok('some relevant assertion here');\n });\n});\n
"
},
{
"textRaw": "`after([fn][, options])`",
"type": "method",
"name": "after",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} The hook function. If the hook uses callbacks, the callback function is passed as the second argument. **Default:** A no-op function.",
"name": "fn",
"type": "Function|AsyncFunction",
"default": "A no-op function",
"desc": "The hook function. If the hook uses callbacks, the callback function is passed as the second argument."
},
{
"textRaw": "`options` {Object} Configuration options for the hook. The following properties are supported:",
"name": "options",
"type": "Object",
"desc": "Configuration options for the hook. The following properties are supported:",
"options": [
{
"textRaw": "`signal` {AbortSignal} Allows aborting an in-progress hook.",
"name": "signal",
"type": "AbortSignal",
"desc": "Allows aborting an in-progress hook."
},
{
"textRaw": "`timeout` {number} A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. **Default:** `Infinity`.",
"name": "timeout",
"type": "number",
"default": "`Infinity`",
"desc": "A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent."
}
]
}
]
}
],
"desc": "This function is used to create a hook running after running a suite.
\ndescribe('tests', async () => {\n after(() => console.log('finished running tests'));\n it('is a subtest', () => {\n assert.ok('some relevant assertion here');\n });\n});\n
\nNote: The after
hook is guaranteed to run,\neven if tests within the suite fail.
This function is used to create a hook running\nbefore each subtest of the current suite.
\ndescribe('tests', async () => {\n beforeEach(() => console.log('about to run a test'));\n it('is a subtest', () => {\n assert.ok('some relevant assertion here');\n });\n});\n
"
},
{
"textRaw": "`afterEach([fn][, options])`",
"type": "method",
"name": "afterEach",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} The hook function. If the hook uses callbacks, the callback function is passed as the second argument. **Default:** A no-op function.",
"name": "fn",
"type": "Function|AsyncFunction",
"default": "A no-op function",
"desc": "The hook function. If the hook uses callbacks, the callback function is passed as the second argument."
},
{
"textRaw": "`options` {Object} Configuration options for the hook. The following properties are supported:",
"name": "options",
"type": "Object",
"desc": "Configuration options for the hook. The following properties are supported:",
"options": [
{
"textRaw": "`signal` {AbortSignal} Allows aborting an in-progress hook.",
"name": "signal",
"type": "AbortSignal",
"desc": "Allows aborting an in-progress hook."
},
{
"textRaw": "`timeout` {number} A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. **Default:** `Infinity`.",
"name": "timeout",
"type": "number",
"default": "`Infinity`",
"desc": "A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent."
}
]
}
]
}
],
"desc": "This function is used to create a hook running\nafter each subtest of the current test.
\nNote: The afterEach
hook is guaranteed to run after every test,\neven if any of the tests fail.
describe('tests', async () => {\n afterEach(() => console.log('finished running a test'));\n it('is a subtest', () => {\n assert.ok('some relevant assertion here');\n });\n});\n
"
}
],
"classes": [
{
"textRaw": "Class: `MockFunctionContext`",
"type": "class",
"name": "MockFunctionContext",
"meta": {
"added": [
"v19.1.0",
"v18.13.0"
],
"changes": []
},
"desc": "The MockFunctionContext
class is used to inspect or manipulate the behavior of\nmocks created via the MockTracker
APIs.
A getter that returns a copy of the internal array used to track calls to the\nmock. Each entry in the array is an object with the following properties.
\narguments
<Array> An array of the arguments passed to the mock function.error
<any> If the mocked function threw then this property contains the\nthrown value. Default: undefined
.result
<any> The value returned by the mocked function.stack
<Error> An Error
object whose stack can be used to determine the\ncallsite of the mocked function invocation.target
<Function> | <undefined> If the mocked function is a constructor, this\nfield contains the class being constructed. Otherwise this will be\nundefined
.this
<any> The mocked function's this
value.This function returns the number of times that this mock has been invoked. This\nfunction is more efficient than checking ctx.calls.length
because ctx.calls
\nis a getter that creates a copy of the internal call tracking array.
This function is used to change the behavior of an existing mock.
\nThe following example creates a mock function using t.mock.fn()
, calls the\nmock function, and then changes the mock implementation to a different function.
test('changes a mock behavior', (t) => {\n let cnt = 0;\n\n function addOne() {\n cnt++;\n return cnt;\n }\n\n function addTwo() {\n cnt += 2;\n return cnt;\n }\n\n const fn = t.mock.fn(addOne);\n\n assert.strictEqual(fn(), 1);\n fn.mock.mockImplementation(addTwo);\n assert.strictEqual(fn(), 3);\n assert.strictEqual(fn(), 5);\n});\n
"
},
{
"textRaw": "`ctx.mockImplementationOnce(implementation[, onCall])`",
"type": "method",
"name": "mockImplementationOnce",
"meta": {
"added": [
"v19.1.0",
"v18.13.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`implementation` {Function|AsyncFunction} The function to be used as the mock's implementation for the invocation number specified by `onCall`.",
"name": "implementation",
"type": "Function|AsyncFunction",
"desc": "The function to be used as the mock's implementation for the invocation number specified by `onCall`."
},
{
"textRaw": "`onCall` {integer} The invocation number that will use `implementation`. If the specified invocation has already occurred then an exception is thrown. **Default:** The number of the next invocation.",
"name": "onCall",
"type": "integer",
"default": "The number of the next invocation",
"desc": "The invocation number that will use `implementation`. If the specified invocation has already occurred then an exception is thrown."
}
]
}
],
"desc": "This function is used to change the behavior of an existing mock for a single\ninvocation. Once invocation onCall
has occurred, the mock will revert to\nwhatever behavior it would have used had mockImplementationOnce()
not been\ncalled.
The following example creates a mock function using t.mock.fn()
, calls the\nmock function, changes the mock implementation to a different function for the\nnext invocation, and then resumes its previous behavior.
test('changes a mock behavior once', (t) => {\n let cnt = 0;\n\n function addOne() {\n cnt++;\n return cnt;\n }\n\n function addTwo() {\n cnt += 2;\n return cnt;\n }\n\n const fn = t.mock.fn(addOne);\n\n assert.strictEqual(fn(), 1);\n fn.mock.mockImplementationOnce(addTwo);\n assert.strictEqual(fn(), 3);\n assert.strictEqual(fn(), 4);\n});\n
"
},
{
"textRaw": "`ctx.resetCalls()`",
"type": "method",
"name": "resetCalls",
"meta": {
"added": [
"v19.3.0",
"v18.13.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Resets the call history of the mock function.
" }, { "textRaw": "`ctx.restore()`", "type": "method", "name": "restore", "meta": { "added": [ "v19.1.0", "v18.13.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Resets the implementation of the mock function to its original behavior. The\nmock can still be used after calling this function.
" } ] }, { "textRaw": "Class: `MockTracker`", "type": "class", "name": "MockTracker", "meta": { "added": [ "v19.1.0", "v18.13.0" ], "changes": [] }, "desc": "The MockTracker
class is used to manage mocking functionality. The test runner\nmodule provides a top level mock
export which is a MockTracker
instance.\nEach test also provides its own MockTracker
instance via the test context's\nmock
property.
This function is used to create a mock function.
\nThe following example creates a mock function that increments a counter by one\non each invocation. The times
option is used to modify the mock behavior such\nthat the first two invocations add two to the counter instead of one.
test('mocks a counting function', (t) => {\n let cnt = 0;\n\n function addOne() {\n cnt++;\n return cnt;\n }\n\n function addTwo() {\n cnt += 2;\n return cnt;\n }\n\n const fn = t.mock.fn(addOne, addTwo, { times: 2 });\n\n assert.strictEqual(fn(), 2);\n assert.strictEqual(fn(), 4);\n assert.strictEqual(fn(), 5);\n assert.strictEqual(fn(), 6);\n});\n
"
},
{
"textRaw": "`mock.getter(object, methodName[, implementation][, options])`",
"type": "method",
"name": "getter",
"meta": {
"added": [
"v19.3.0",
"v18.13.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "This function is syntax sugar for MockTracker.method
with options.getter
\nset to true
.
This function is used to create a mock on an existing object method. The\nfollowing example demonstrates how a mock is created on an existing object\nmethod.
\ntest('spies on an object method', (t) => {\n const number = {\n value: 5,\n subtract(a) {\n return this.value - a;\n },\n };\n\n t.mock.method(number, 'subtract');\n assert.strictEqual(number.subtract.mock.calls.length, 0);\n assert.strictEqual(number.subtract(3), 2);\n assert.strictEqual(number.subtract.mock.calls.length, 1);\n\n const call = number.subtract.mock.calls[0];\n\n assert.deepStrictEqual(call.arguments, [3]);\n assert.strictEqual(call.result, 2);\n assert.strictEqual(call.error, undefined);\n assert.strictEqual(call.target, undefined);\n assert.strictEqual(call.this, number);\n});\n
"
},
{
"textRaw": "`mock.reset()`",
"type": "method",
"name": "reset",
"meta": {
"added": [
"v19.1.0",
"v18.13.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "This function restores the default behavior of all mocks that were previously\ncreated by this MockTracker
and disassociates the mocks from the\nMockTracker
instance. Once disassociated, the mocks can still be used, but the\nMockTracker
instance can no longer be used to reset their behavior or\notherwise interact with them.
After each test completes, this function is called on the test context's\nMockTracker
. If the global MockTracker
is used extensively, calling this\nfunction manually is recommended.
This function restores the default behavior of all mocks that were previously\ncreated by this MockTracker
. Unlike mock.reset()
, mock.restoreAll()
does\nnot disassociate the mocks from the MockTracker
instance.
This function is syntax sugar for MockTracker.method
with options.setter
\nset to true
.
Mocking timers is a technique commonly used in software testing to simulate and\ncontrol the behavior of timers, such as setInterval
and setTimeout
,\nwithout actually waiting for the specified time intervals.
MockTimers is also able to mock the Date
object.
The MockTracker
provides a top-level timers
export\nwhich is a MockTimers
instance.
Enables timer mocking for the specified timers.
\nenableOptions
<Object> Optional configuration options for enabling timer\nmocking. The following properties are supported:\napis
<Array> An optional array containing the timers to mock.\nThe currently supported timer values are 'setInterval'
, 'setTimeout'
, 'setImmediate'
,\nand 'Date'
. Default: ['setInterval', 'setTimeout', 'setImmediate', 'Date']
.\nIf no array is provided, all time related APIs ('setInterval'
, 'clearInterval'
,\n'setTimeout'
, 'clearTimeout'
, and 'Date'
) will be mocked by default.now
<number> | <Date> An optional number or Date object representing the\ninitial time (in milliseconds) to use as the value\nfor Date.now()
. Default: 0
.Note: When you enable mocking for a specific timer, its associated\nclear function will also be implicitly mocked.
\nNote: Mocking Date
will affect the behavior of the mocked timers\nas they use the same internal clock.
Example usage without setting initial time:
\nimport { mock } from 'node:test';\nmock.timers.enable({ apis: ['setInterval'] });\n
\nconst { mock } = require('node:test');\nmock.timers.enable({ apis: ['setInterval'] });\n
\nThe above example enables mocking for the setInterval
timer and\nimplicitly mocks the clearInterval
function. Only the setInterval
\nand clearInterval
functions from node:timers,\nnode:timers/promises, and\nglobalThis
will be mocked.
Example usage with initial time set
\nimport { mock } from 'node:test';\nmock.timers.enable({ apis: ['Date'], now: 1000 });\n
\nconst { mock } = require('node:test');\nmock.timers.enable({ apis: ['Date'], now: 1000 });\n
\nExample usage with initial Date object as time set
\nimport { mock } from 'node:test';\nmock.timers.enable({ apis: ['Date'], now: new Date() });\n
\nconst { mock } = require('node:test');\nmock.timers.enable({ apis: ['Date'], now: new Date() });\n
\nAlternatively, if you call mock.timers.enable()
without any parameters:
All timers ('setInterval'
, 'clearInterval'
, 'setTimeout'
, and 'clearTimeout'
)\nwill be mocked. The setInterval
, clearInterval
, setTimeout
, and clearTimeout
\nfunctions from node:timers
, node:timers/promises
,\nand globalThis
will be mocked. As well as the global Date
object.
This function restores the default behavior of all mocks that were previously\ncreated by this MockTimers
instance and disassociates the mocks\nfrom the MockTracker
instance.
Note: After each test completes, this function is called on\nthe test context's MockTracker
.
import { mock } from 'node:test';\nmock.timers.reset();\n
\nconst { mock } = require('node:test');\nmock.timers.reset();\n
"
},
{
"textRaw": "`timers[Symbol.dispose]()`",
"type": "method",
"name": "[Symbol.dispose]",
"signatures": [
{
"params": []
}
],
"desc": "Calls timers.reset()
.
Advances time for all mocked timers.
\nmilliseconds
<number> The amount of time, in milliseconds,\nto advance the timers.Note: This diverges from how setTimeout
in Node.js behaves and accepts\nonly positive numbers. In Node.js, setTimeout
with negative numbers is\nonly supported for web compatibility reasons.
The following example mocks a setTimeout
function and\nby using .tick
advances in\ntime triggering all pending timers.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n\n context.mock.timers.enable({ apis: ['setTimeout'] });\n\n setTimeout(fn, 9999);\n\n assert.strictEqual(fn.mock.callCount(), 0);\n\n // Advance in time\n context.mock.timers.tick(9999);\n\n assert.strictEqual(fn.mock.callCount(), 1);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n context.mock.timers.enable({ apis: ['setTimeout'] });\n\n setTimeout(fn, 9999);\n assert.strictEqual(fn.mock.callCount(), 0);\n\n // Advance in time\n context.mock.timers.tick(9999);\n\n assert.strictEqual(fn.mock.callCount(), 1);\n});\n
\nAlternativelly, the .tick
function can be called many times
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n context.mock.timers.enable({ apis: ['setTimeout'] });\n const nineSecs = 9000;\n setTimeout(fn, nineSecs);\n\n const twoSeconds = 3000;\n context.mock.timers.tick(twoSeconds);\n context.mock.timers.tick(twoSeconds);\n context.mock.timers.tick(twoSeconds);\n\n assert.strictEqual(fn.mock.callCount(), 1);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n context.mock.timers.enable({ apis: ['setTimeout'] });\n const nineSecs = 9000;\n setTimeout(fn, nineSecs);\n\n const twoSeconds = 3000;\n context.mock.timers.tick(twoSeconds);\n context.mock.timers.tick(twoSeconds);\n context.mock.timers.tick(twoSeconds);\n\n assert.strictEqual(fn.mock.callCount(), 1);\n});\n
\nAdvancing time using .tick
will also advance the time for any Date
object\ncreated after the mock was enabled (if Date
was also set to be mocked).
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n setTimeout(fn, 9999);\n\n assert.strictEqual(fn.mock.callCount(), 0);\n assert.strictEqual(Date.now(), 0);\n\n // Advance in time\n context.mock.timers.tick(9999);\n assert.strictEqual(fn.mock.callCount(), 1);\n assert.strictEqual(Date.now(), 9999);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n\n setTimeout(fn, 9999);\n assert.strictEqual(fn.mock.callCount(), 0);\n assert.strictEqual(Date.now(), 0);\n\n // Advance in time\n context.mock.timers.tick(9999);\n assert.strictEqual(fn.mock.callCount(), 1);\n assert.strictEqual(Date.now(), 9999);\n});\n
",
"modules": [
{
"textRaw": "Using clear functions",
"name": "using_clear_functions",
"desc": "As mentioned, all clear functions from timers (clearTimeout
and clearInterval
)\nare implicity mocked. Take a look at this example using setTimeout
:
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout'] });\n const id = setTimeout(fn, 9999);\n\n // Implicity mocked as well\n clearTimeout(id);\n context.mock.timers.tick(9999);\n\n // As that setTimeout was cleared the mock function will never be called\n assert.strictEqual(fn.mock.callCount(), 0);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {\n const fn = context.mock.fn();\n\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout'] });\n const id = setTimeout(fn, 9999);\n\n // Implicity mocked as well\n clearTimeout(id);\n context.mock.timers.tick(9999);\n\n // As that setTimeout was cleared the mock function will never be called\n assert.strictEqual(fn.mock.callCount(), 0);\n});\n
",
"type": "module",
"displayName": "Using clear functions"
},
{
"textRaw": "Working with Node.js timers modules",
"name": "working_with_node.js_timers_modules",
"desc": "Once you enable mocking timers, node:timers,\nnode:timers/promises modules,\nand timers from the Node.js global context are enabled:
\nNote: Destructuring functions such as\nimport { setTimeout } from 'node:timers'
is currently\nnot supported by this API.
import assert from 'node:assert';\nimport { test } from 'node:test';\nimport nodeTimers from 'node:timers';\nimport nodeTimersPromises from 'node:timers/promises';\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', async (context) => {\n const globalTimeoutObjectSpy = context.mock.fn();\n const nodeTimerSpy = context.mock.fn();\n const nodeTimerPromiseSpy = context.mock.fn();\n\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout'] });\n setTimeout(globalTimeoutObjectSpy, 9999);\n nodeTimers.setTimeout(nodeTimerSpy, 9999);\n\n const promise = nodeTimersPromises.setTimeout(9999).then(nodeTimerPromiseSpy);\n\n // Advance in time\n context.mock.timers.tick(9999);\n assert.strictEqual(globalTimeoutObjectSpy.mock.callCount(), 1);\n assert.strictEqual(nodeTimerSpy.mock.callCount(), 1);\n await promise;\n assert.strictEqual(nodeTimerPromiseSpy.mock.callCount(), 1);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\nconst nodeTimers = require('node:timers');\nconst nodeTimersPromises = require('node:timers/promises');\n\ntest('mocks setTimeout to be executed synchronously without having to actually wait for it', async (context) => {\n const globalTimeoutObjectSpy = context.mock.fn();\n const nodeTimerSpy = context.mock.fn();\n const nodeTimerPromiseSpy = context.mock.fn();\n\n // Optionally choose what to mock\n context.mock.timers.enable({ apis: ['setTimeout'] });\n setTimeout(globalTimeoutObjectSpy, 9999);\n nodeTimers.setTimeout(nodeTimerSpy, 9999);\n\n const promise = nodeTimersPromises.setTimeout(9999).then(nodeTimerPromiseSpy);\n\n // Advance in time\n context.mock.timers.tick(9999);\n assert.strictEqual(globalTimeoutObjectSpy.mock.callCount(), 1);\n assert.strictEqual(nodeTimerSpy.mock.callCount(), 1);\n await promise;\n assert.strictEqual(nodeTimerPromiseSpy.mock.callCount(), 1);\n});\n
\nIn Node.js, setInterval
from node:timers/promises\nis an AsyncGenerator
and is also supported by this API:
import assert from 'node:assert';\nimport { test } from 'node:test';\nimport nodeTimersPromises from 'node:timers/promises';\ntest('should tick five times testing a real use case', async (context) => {\n context.mock.timers.enable({ apis: ['setInterval'] });\n\n const expectedIterations = 3;\n const interval = 1000;\n const startedAt = Date.now();\n async function run() {\n const times = [];\n for await (const time of nodeTimersPromises.setInterval(interval, startedAt)) {\n times.push(time);\n if (times.length === expectedIterations) break;\n }\n return times;\n }\n\n const r = run();\n context.mock.timers.tick(interval);\n context.mock.timers.tick(interval);\n context.mock.timers.tick(interval);\n\n const timeResults = await r;\n assert.strictEqual(timeResults.length, expectedIterations);\n for (let it = 1; it < expectedIterations; it++) {\n assert.strictEqual(timeResults[it - 1], startedAt + (interval * it));\n }\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\nconst nodeTimersPromises = require('node:timers/promises');\ntest('should tick five times testing a real use case', async (context) => {\n context.mock.timers.enable({ apis: ['setInterval'] });\n\n const expectedIterations = 3;\n const interval = 1000;\n const startedAt = Date.now();\n async function run() {\n const times = [];\n for await (const time of nodeTimersPromises.setInterval(interval, startedAt)) {\n times.push(time);\n if (times.length === expectedIterations) break;\n }\n return times;\n }\n\n const r = run();\n context.mock.timers.tick(interval);\n context.mock.timers.tick(interval);\n context.mock.timers.tick(interval);\n\n const timeResults = await r;\n assert.strictEqual(timeResults.length, expectedIterations);\n for (let it = 1; it < expectedIterations; it++) {\n assert.strictEqual(timeResults[it - 1], startedAt + (interval * it));\n }\n});\n
",
"type": "module",
"displayName": "Working with Node.js timers modules"
}
]
},
{
"textRaw": "`timers.runAll()`",
"type": "method",
"name": "runAll",
"meta": {
"added": [
"v20.4.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Triggers all pending mocked timers immediately. If the Date
object is also\nmocked, it will also advance the Date
object to the furthest timer's time.
The example below triggers all pending timers immediately,\ncausing them to execute without any delay.
\nimport assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('runAll functions following the given order', (context) => {\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const results = [];\n setTimeout(() => results.push(1), 9999);\n\n // Notice that if both timers have the same timeout,\n // the order of execution is guaranteed\n setTimeout(() => results.push(3), 8888);\n setTimeout(() => results.push(2), 8888);\n\n assert.deepStrictEqual(results, []);\n\n context.mock.timers.runAll();\n assert.deepStrictEqual(results, [3, 2, 1]);\n // The Date object is also advanced to the furthest timer's time\n assert.strictEqual(Date.now(), 9999);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('runAll functions following the given order', (context) => {\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const results = [];\n setTimeout(() => results.push(1), 9999);\n\n // Notice that if both timers have the same timeout,\n // the order of execution is guaranteed\n setTimeout(() => results.push(3), 8888);\n setTimeout(() => results.push(2), 8888);\n\n assert.deepStrictEqual(results, []);\n\n context.mock.timers.runAll();\n assert.deepStrictEqual(results, [3, 2, 1]);\n // The Date object is also advanced to the furthest timer's time\n assert.strictEqual(Date.now(), 9999);\n});\n
\nNote: The runAll()
function is specifically designed for\ntriggering timers in the context of timer mocking.\nIt does not have any effect on real-time system\nclocks or actual timers outside of the mocking environment.
Sets the current Unix timestamp that will be used as reference for any mocked\nDate
objects.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('runAll functions following the given order', (context) => {\n const now = Date.now();\n const setTime = 1000;\n // Date.now is not mocked\n assert.deepStrictEqual(Date.now(), now);\n\n context.mock.timers.enable({ apis: ['Date'] });\n context.mock.timers.setTime(setTime);\n // Date.now is now 1000\n assert.strictEqual(Date.now(), setTime);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('setTime replaces current time', (context) => {\n const now = Date.now();\n const setTime = 1000;\n // Date.now is not mocked\n assert.deepStrictEqual(Date.now(), now);\n\n context.mock.timers.enable({ apis: ['Date'] });\n context.mock.timers.setTime(setTime);\n // Date.now is now 1000\n assert.strictEqual(Date.now(), setTime);\n});\n
",
"modules": [
{
"textRaw": "Dates and Timers working together",
"name": "dates_and_timers_working_together",
"desc": "Dates and timer objects are dependent on each other. If you use setTime()
to\npass the current time to the mocked Date
object, the set timers with\nsetTimeout
and setInterval
will not be affected.
However, the tick
method will advanced the mocked Date
object.
import assert from 'node:assert';\nimport { test } from 'node:test';\n\ntest('runAll functions following the given order', (context) => {\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const results = [];\n setTimeout(() => results.push(1), 9999);\n\n assert.deepStrictEqual(results, []);\n context.mock.timers.setTime(12000);\n assert.deepStrictEqual(results, []);\n // The date is advanced but the timers don't tick\n assert.strictEqual(Date.now(), 12000);\n});\n
\nconst assert = require('node:assert');\nconst { test } = require('node:test');\n\ntest('runAll functions following the given order', (context) => {\n context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });\n const results = [];\n setTimeout(() => results.push(1), 9999);\n\n assert.deepStrictEqual(results, []);\n context.mock.timers.setTime(12000);\n assert.deepStrictEqual(results, []);\n // The date is advanced but the timers don't tick\n assert.strictEqual(Date.now(), 12000);\n});\n
",
"type": "module",
"displayName": "Dates and Timers working together"
}
]
}
]
},
{
"textRaw": "Class: `TestsStream`",
"type": "class",
"name": "TestsStream",
"meta": {
"added": [
"v18.9.0",
"v16.19.0"
],
"changes": [
{
"version": [
"v20.0.0",
"v19.9.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47094",
"description": "added type to test:pass and test:fail events for when the test is a suite."
}
]
},
"desc": "A successful call to run()
method will return a new <TestsStream>\nobject, streaming a series of events representing the execution of the tests.\nTestsStream
will emit events, in the order of the tests definition
Emitted when code coverage is enabled and all tests have completed.
" }, { "textRaw": "Event: `'test:dequeue'`", "type": "event", "name": "test:dequeue", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`file` {string|undefined} The path of the test file, `undefined` if test was run through the REPL.", "name": "file", "type": "string|undefined", "desc": "The path of the test file, `undefined` if test was run through the REPL." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`name` {string} The test name.", "name": "name", "type": "string", "desc": "The test name." }, { "textRaw": "`nesting` {number} The nesting level of the test.", "name": "nesting", "type": "number", "desc": "The nesting level of the test." } ] } ], "desc": "Emitted when a test is dequeued, right before it is executed.
" }, { "textRaw": "Event: `'test:diagnostic'`", "type": "event", "name": "test:diagnostic", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`file` {string|undefined} The path of the test file, `undefined` if test was run through the REPL.", "name": "file", "type": "string|undefined", "desc": "The path of the test file, `undefined` if test was run through the REPL." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`message` {string} The diagnostic message.", "name": "message", "type": "string", "desc": "The diagnostic message." }, { "textRaw": "`nesting` {number} The nesting level of the test.", "name": "nesting", "type": "number", "desc": "The nesting level of the test." } ] } ], "desc": "Emitted when context.diagnostic
is called.
Emitted when a test is enqueued for execution.
" }, { "textRaw": "Event: `'test:fail'`", "type": "event", "name": "test:fail", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`details` {Object} Additional execution metadata.", "name": "details", "type": "Object", "desc": "Additional execution metadata.", "options": [ { "textRaw": "`duration_ms` {number} The duration of the test in milliseconds.", "name": "duration_ms", "type": "number", "desc": "The duration of the test in milliseconds." }, { "textRaw": "`error` {Error} An error wrapping the error thrown by the test.", "name": "error", "type": "Error", "desc": "An error wrapping the error thrown by the test.", "options": [ { "textRaw": "`cause` {Error} The actual error thrown by the test.", "name": "cause", "type": "Error", "desc": "The actual error thrown by the test." } ] }, { "textRaw": "`type` {string|undefined} The type of the test, used to denote whether this is a suite.", "name": "type", "type": "string|undefined", "desc": "The type of the test, used to denote whether this is a suite." } ] }, { "textRaw": "`file` {string|undefined} The path of the test file, `undefined` if test was run through the REPL.", "name": "file", "type": "string|undefined", "desc": "The path of the test file, `undefined` if test was run through the REPL." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`name` {string} The test name.", "name": "name", "type": "string", "desc": "The test name." }, { "textRaw": "`nesting` {number} The nesting level of the test.", "name": "nesting", "type": "number", "desc": "The nesting level of the test." }, { "textRaw": "`testNumber` {number} The ordinal number of the test.", "name": "testNumber", "type": "number", "desc": "The ordinal number of the test." }, { "textRaw": "`todo` {string|boolean|undefined} Present if [`context.todo`][] is called", "name": "todo", "type": "string|boolean|undefined", "desc": "Present if [`context.todo`][] is called" }, { "textRaw": "`skip` {string|boolean|undefined} Present if [`context.skip`][] is called", "name": "skip", "type": "string|boolean|undefined", "desc": "Present if [`context.skip`][] is called" } ] } ], "desc": "Emitted when a test fails.
" }, { "textRaw": "Event: `'test:pass'`", "type": "event", "name": "test:pass", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`details` {Object} Additional execution metadata.", "name": "details", "type": "Object", "desc": "Additional execution metadata.", "options": [ { "textRaw": "`duration_ms` {number} The duration of the test in milliseconds.", "name": "duration_ms", "type": "number", "desc": "The duration of the test in milliseconds." }, { "textRaw": "`type` {string|undefined} The type of the test, used to denote whether this is a suite.", "name": "type", "type": "string|undefined", "desc": "The type of the test, used to denote whether this is a suite." } ] }, { "textRaw": "`file` {string|undefined} The path of the test file, `undefined` if test was run through the REPL.", "name": "file", "type": "string|undefined", "desc": "The path of the test file, `undefined` if test was run through the REPL." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`name` {string} The test name.", "name": "name", "type": "string", "desc": "The test name." }, { "textRaw": "`nesting` {number} The nesting level of the test.", "name": "nesting", "type": "number", "desc": "The nesting level of the test." }, { "textRaw": "`testNumber` {number} The ordinal number of the test.", "name": "testNumber", "type": "number", "desc": "The ordinal number of the test." }, { "textRaw": "`todo` {string|boolean|undefined} Present if [`context.todo`][] is called", "name": "todo", "type": "string|boolean|undefined", "desc": "Present if [`context.todo`][] is called" }, { "textRaw": "`skip` {string|boolean|undefined} Present if [`context.skip`][] is called", "name": "skip", "type": "string|boolean|undefined", "desc": "Present if [`context.skip`][] is called" } ] } ], "desc": "Emitted when a test passes.
" }, { "textRaw": "Event: `'test:plan'`", "type": "event", "name": "test:plan", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`file` {string|undefined} The path of the test file, `undefined` if test was run through the REPL.", "name": "file", "type": "string|undefined", "desc": "The path of the test file, `undefined` if test was run through the REPL." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`nesting` {number} The nesting level of the test.", "name": "nesting", "type": "number", "desc": "The nesting level of the test." }, { "textRaw": "`count` {number} The number of subtests that have ran.", "name": "count", "type": "number", "desc": "The number of subtests that have ran." } ] } ], "desc": "Emitted when all subtests have completed for a given test.
" }, { "textRaw": "Event: `'test:start'`", "type": "event", "name": "test:start", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`file` {string|undefined} The path of the test file, `undefined` if test was run through the REPL.", "name": "file", "type": "string|undefined", "desc": "The path of the test file, `undefined` if test was run through the REPL." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`name` {string} The test name.", "name": "name", "type": "string", "desc": "The test name." }, { "textRaw": "`nesting` {number} The nesting level of the test.", "name": "nesting", "type": "number", "desc": "The nesting level of the test." } ] } ], "desc": "Emitted when a test starts reporting its own and its subtests status.\nThis event is guaranteed to be emitted in the same order as the tests are\ndefined.
" }, { "textRaw": "Event: `'test:stderr'`", "type": "event", "name": "test:stderr", "params": [ { "textRaw": "`data` {Object}", "name": "data", "type": "Object", "options": [ { "textRaw": "`column` {number|undefined} The column number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "column", "type": "number|undefined", "desc": "The column number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`file` {string} The path of the test file.", "name": "file", "type": "string", "desc": "The path of the test file." }, { "textRaw": "`line` {number|undefined} The line number where the test is defined, or `undefined` if the test was run through the REPL.", "name": "line", "type": "number|undefined", "desc": "The line number where the test is defined, or `undefined` if the test was run through the REPL." }, { "textRaw": "`message` {string} The message written to `stderr`.", "name": "message", "type": "string", "desc": "The message written to `stderr`." } ] } ], "desc": "Emitted when a running test writes to stderr
.\nThis event is only emitted if --test
flag is passed.
Emitted when a running test writes to stdout
.\nThis event is only emitted if --test
flag is passed.
Emitted when no more tests are queued for execution in watch mode.
" } ] }, { "textRaw": "Class: `TestContext`", "type": "class", "name": "TestContext", "meta": { "added": [ "v18.0.0", "v16.17.0" ], "changes": [ { "version": [ "v20.1.0", "v18.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/47586", "description": "The `before` function was added to TestContext." } ] }, "desc": "An instance of TestContext
is passed to each test function in order to\ninteract with the test runner. However, the TestContext
constructor is not\nexposed as part of the API.
This function is used to create a hook running before\nsubtest of the current test.
" }, { "textRaw": "`context.beforeEach([fn][, options])`", "type": "method", "name": "beforeEach", "meta": { "added": [ "v18.8.0", "v16.18.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`fn` {Function|AsyncFunction} The hook function. The first argument to this function is a [`TestContext`][] object. If the hook uses callbacks, the callback function is passed as the second argument. **Default:** A no-op function.", "name": "fn", "type": "Function|AsyncFunction", "default": "A no-op function", "desc": "The hook function. The first argument to this function is a [`TestContext`][] object. If the hook uses callbacks, the callback function is passed as the second argument." }, { "textRaw": "`options` {Object} Configuration options for the hook. The following properties are supported:", "name": "options", "type": "Object", "desc": "Configuration options for the hook. The following properties are supported:", "options": [ { "textRaw": "`signal` {AbortSignal} Allows aborting an in-progress hook.", "name": "signal", "type": "AbortSignal", "desc": "Allows aborting an in-progress hook." }, { "textRaw": "`timeout` {number} A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. **Default:** `Infinity`.", "name": "timeout", "type": "number", "default": "`Infinity`", "desc": "A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent." } ] } ] } ], "desc": "This function is used to create a hook running\nbefore each subtest of the current test.
\ntest('top level test', async (t) => {\n t.beforeEach((t) => t.diagnostic(`about to run ${t.name}`));\n await t.test(\n 'This is a subtest',\n (t) => {\n assert.ok('some relevant assertion here');\n },\n );\n});\n
"
},
{
"textRaw": "`context.after([fn][, options])`",
"type": "method",
"name": "after",
"meta": {
"added": [
"v19.3.0",
"v18.13.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} The hook function. The first argument to this function is a [`TestContext`][] object. If the hook uses callbacks, the callback function is passed as the second argument. **Default:** A no-op function.",
"name": "fn",
"type": "Function|AsyncFunction",
"default": "A no-op function",
"desc": "The hook function. The first argument to this function is a [`TestContext`][] object. If the hook uses callbacks, the callback function is passed as the second argument."
},
{
"textRaw": "`options` {Object} Configuration options for the hook. The following properties are supported:",
"name": "options",
"type": "Object",
"desc": "Configuration options for the hook. The following properties are supported:",
"options": [
{
"textRaw": "`signal` {AbortSignal} Allows aborting an in-progress hook.",
"name": "signal",
"type": "AbortSignal",
"desc": "Allows aborting an in-progress hook."
},
{
"textRaw": "`timeout` {number} A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. **Default:** `Infinity`.",
"name": "timeout",
"type": "number",
"default": "`Infinity`",
"desc": "A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent."
}
]
}
]
}
],
"desc": "This function is used to create a hook that runs after the current test\nfinishes.
\ntest('top level test', async (t) => {\n t.after((t) => t.diagnostic(`finished running ${t.name}`));\n assert.ok('some relevant assertion here');\n});\n
"
},
{
"textRaw": "`context.afterEach([fn][, options])`",
"type": "method",
"name": "afterEach",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function|AsyncFunction} The hook function. The first argument to this function is a [`TestContext`][] object. If the hook uses callbacks, the callback function is passed as the second argument. **Default:** A no-op function.",
"name": "fn",
"type": "Function|AsyncFunction",
"default": "A no-op function",
"desc": "The hook function. The first argument to this function is a [`TestContext`][] object. If the hook uses callbacks, the callback function is passed as the second argument."
},
{
"textRaw": "`options` {Object} Configuration options for the hook. The following properties are supported:",
"name": "options",
"type": "Object",
"desc": "Configuration options for the hook. The following properties are supported:",
"options": [
{
"textRaw": "`signal` {AbortSignal} Allows aborting an in-progress hook.",
"name": "signal",
"type": "AbortSignal",
"desc": "Allows aborting an in-progress hook."
},
{
"textRaw": "`timeout` {number} A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. **Default:** `Infinity`.",
"name": "timeout",
"type": "number",
"default": "`Infinity`",
"desc": "A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent."
}
]
}
]
}
],
"desc": "This function is used to create a hook running\nafter each subtest of the current test.
\ntest('top level test', async (t) => {\n t.afterEach((t) => t.diagnostic(`finished running ${t.name}`));\n await t.test(\n 'This is a subtest',\n (t) => {\n assert.ok('some relevant assertion here');\n },\n );\n});\n
"
},
{
"textRaw": "`context.diagnostic(message)`",
"type": "method",
"name": "diagnostic",
"meta": {
"added": [
"v18.0.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`message` {string} Message to be reported.",
"name": "message",
"type": "string",
"desc": "Message to be reported."
}
]
}
],
"desc": "This function is used to write diagnostics to the output. Any diagnostic\ninformation is included at the end of the test's results. This function does\nnot return a value.
\ntest('top level test', (t) => {\n t.diagnostic('A diagnostic message');\n});\n
"
},
{
"textRaw": "`context.runOnly(shouldRunOnlyTests)`",
"type": "method",
"name": "runOnly",
"meta": {
"added": [
"v18.0.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`shouldRunOnlyTests` {boolean} Whether or not to run `only` tests.",
"name": "shouldRunOnlyTests",
"type": "boolean",
"desc": "Whether or not to run `only` tests."
}
]
}
],
"desc": "If shouldRunOnlyTests
is truthy, the test context will only run tests that\nhave the only
option set. Otherwise, all tests are run. If Node.js was not\nstarted with the --test-only
command-line option, this function is a\nno-op.
test('top level test', (t) => {\n // The test context can be set to run subtests with the 'only' option.\n t.runOnly(true);\n return Promise.all([\n t.test('this subtest is now skipped'),\n t.test('this subtest is run', { only: true }),\n ]);\n});\n
"
},
{
"textRaw": "`context.skip([message])`",
"type": "method",
"name": "skip",
"meta": {
"added": [
"v18.0.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`message` {string} Optional skip message.",
"name": "message",
"type": "string",
"desc": "Optional skip message."
}
]
}
],
"desc": "This function causes the test's output to indicate the test as skipped. If\nmessage
is provided, it is included in the output. Calling skip()
does\nnot terminate execution of the test function. This function does not return a\nvalue.
test('top level test', (t) => {\n // Make sure to return here as well if the test contains additional logic.\n t.skip('this is skipped');\n});\n
"
},
{
"textRaw": "`context.todo([message])`",
"type": "method",
"name": "todo",
"meta": {
"added": [
"v18.0.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`message` {string} Optional `TODO` message.",
"name": "message",
"type": "string",
"desc": "Optional `TODO` message."
}
]
}
],
"desc": "This function adds a TODO
directive to the test's output. If message
is\nprovided, it is included in the output. Calling todo()
does not terminate\nexecution of the test function. This function does not return a value.
test('top level test', (t) => {\n // This test is marked as `TODO`\n t.todo('this is a todo');\n});\n
"
},
{
"textRaw": "`context.test([name][, options][, fn])`",
"type": "method",
"name": "test",
"meta": {
"added": [
"v18.0.0",
"v16.17.0"
],
"changes": [
{
"version": [
"v18.8.0",
"v16.18.0"
],
"pr-url": "https://github.com/nodejs/node/pull/43554",
"description": "Add a `signal` option."
},
{
"version": [
"v18.7.0",
"v16.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/43505",
"description": "Add a `timeout` option."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfilled with `undefined` once the test completes.",
"name": "return",
"type": "Promise",
"desc": "Fulfilled with `undefined` once the test completes."
},
"params": [
{
"textRaw": "`name` {string} The name of the subtest, which is displayed when reporting test results. **Default:** The `name` property of `fn`, or `'This function is used to create subtests under the current test. This function\nbehaves in the same fashion as the top level test()
function.
test('top level test', async (t) => {\n await t.test(\n 'This is a subtest',\n { only: false, skip: false, concurrency: 1, todo: false },\n (t) => {\n assert.ok('some relevant assertion here');\n },\n );\n});\n
"
}
],
"properties": [
{
"textRaw": "`context.name`",
"name": "name",
"meta": {
"added": [
"v18.8.0",
"v16.18.0"
],
"changes": []
},
"desc": "The name of the test.
" }, { "textRaw": "`signal` Type: {AbortSignal}", "type": "AbortSignal", "name": "Type", "meta": { "added": [ "v18.7.0", "v16.17.0" ], "changes": [] }, "desc": "Can be used to abort test subtasks when the test has been aborted.
\ntest('top level test', async (t) => {\n await fetch('some/uri', { signal: t.signal });\n});\n
"
}
]
},
{
"textRaw": "Class: `SuiteContext`",
"type": "class",
"name": "SuiteContext",
"meta": {
"added": [
"v18.7.0",
"v16.17.0"
],
"changes": []
},
"desc": "An instance of SuiteContext
is passed to each suite function in order to\ninteract with the test runner. However, the SuiteContext
constructor is not\nexposed as part of the API.
The name of the suite.
" }, { "textRaw": "`signal` Type: {AbortSignal}", "type": "AbortSignal", "name": "Type", "meta": { "added": [ "v18.7.0", "v16.17.0" ], "changes": [] }, "desc": "Can be used to abort test subtasks when the test has been aborted.
" } ] } ], "type": "module", "displayName": "Test runner", "source": "doc/api/test.md" }, { "textRaw": "Timers", "name": "timers", "introduced_in": "v0.10.0", "stability": 2, "stabilityText": "Stable", "desc": "Source Code: lib/timers.js
\nThe timer
module exposes a global API for scheduling functions to\nbe called at some future period of time. Because the timer functions are\nglobals, there is no need to call require('node:timers')
to use the API.
The timer functions within Node.js implement a similar API as the timers API\nprovided by Web Browsers but use a different internal implementation that is\nbuilt around the Node.js Event Loop.
", "classes": [ { "textRaw": "Class: `Immediate`", "type": "class", "name": "Immediate", "desc": "This object is created internally and is returned from setImmediate()
. It\ncan be passed to clearImmediate()
in order to cancel the scheduled\nactions.
By default, when an immediate is scheduled, the Node.js event loop will continue\nrunning as long as the immediate is active. The Immediate
object returned by\nsetImmediate()
exports both immediate.ref()
and immediate.unref()
\nfunctions that can be used to control this default behavior.
If true, the Immediate
object will keep the Node.js event loop active.
When called, requests that the Node.js event loop not exit so long as the\nImmediate
is active. Calling immediate.ref()
multiple times will have no\neffect.
By default, all Immediate
objects are \"ref'ed\", making it normally unnecessary\nto call immediate.ref()
unless immediate.unref()
had been called previously.
When called, the active Immediate
object will not require the Node.js event\nloop to remain active. If there is no other activity keeping the event loop\nrunning, the process may exit before the Immediate
object's callback is\ninvoked. Calling immediate.unref()
multiple times will have no effect.
Cancels the immediate. This is similar to calling clearImmediate()
.
This object is created internally and is returned from setTimeout()
and\nsetInterval()
. It can be passed to either clearTimeout()
or\nclearInterval()
in order to cancel the scheduled actions.
By default, when a timer is scheduled using either setTimeout()
or\nsetInterval()
, the Node.js event loop will continue running as long as the\ntimer is active. Each of the Timeout
objects returned by these functions\nexport both timeout.ref()
and timeout.unref()
functions that can be used to\ncontrol this default behavior.
Cancels the timeout.
" }, { "textRaw": "`timeout.hasRef()`", "type": "method", "name": "hasRef", "meta": { "added": [ "v11.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [] } ], "desc": "If true, the Timeout
object will keep the Node.js event loop active.
When called, requests that the Node.js event loop not exit so long as the\nTimeout
is active. Calling timeout.ref()
multiple times will have no effect.
By default, all Timeout
objects are \"ref'ed\", making it normally unnecessary\nto call timeout.ref()
unless timeout.unref()
had been called previously.
Sets the timer's start time to the current time, and reschedules the timer to\ncall its callback at the previously specified duration adjusted to the current\ntime. This is useful for refreshing a timer without allocating a new\nJavaScript object.
\nUsing this on a timer that has already called its callback will reactivate the\ntimer.
" }, { "textRaw": "`timeout.unref()`", "type": "method", "name": "unref", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Timeout} a reference to `timeout`", "name": "return", "type": "Timeout", "desc": "a reference to `timeout`" }, "params": [] } ], "desc": "When called, the active Timeout
object will not require the Node.js event loop\nto remain active. If there is no other activity keeping the event loop running,\nthe process may exit before the Timeout
object's callback is invoked. Calling\ntimeout.unref()
multiple times will have no effect.
Coerce a Timeout
to a primitive. The primitive can be used to\nclear the Timeout
. The primitive can only be used in the\nsame thread where the timeout was created. Therefore, to use it\nacross worker_threads
it must first be passed to the correct\nthread. This allows enhanced compatibility with browser\nsetTimeout()
and setInterval()
implementations.
Cancels the timeout.
" } ] } ], "modules": [ { "textRaw": "Scheduling timers", "name": "scheduling_timers", "desc": "A timer in Node.js is an internal construct that calls a given function after\na certain period of time. When a timer's function is called varies depending on\nwhich method was used to create the timer and what other work the Node.js\nevent loop is doing.
", "methods": [ { "textRaw": "`setImmediate(callback[, ...args])`", "type": "method", "name": "setImmediate", "meta": { "added": [ "v0.9.1" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Immediate} for use with [`clearImmediate()`][]", "name": "return", "type": "Immediate", "desc": "for use with [`clearImmediate()`][]" }, "params": [ { "textRaw": "`callback` {Function} The function to call at the end of this turn of the Node.js [Event Loop][]", "name": "callback", "type": "Function", "desc": "The function to call at the end of this turn of the Node.js [Event Loop][]" }, { "textRaw": "`...args` {any} Optional arguments to pass when the `callback` is called.", "name": "...args", "type": "any", "desc": "Optional arguments to pass when the `callback` is called." } ] } ], "desc": "Schedules the \"immediate\" execution of the callback
after I/O events'\ncallbacks.
When multiple calls to setImmediate()
are made, the callback
functions are\nqueued for execution in the order in which they are created. The entire callback\nqueue is processed every event loop iteration. If an immediate timer is queued\nfrom inside an executing callback, that timer will not be triggered until the\nnext event loop iteration.
If callback
is not a function, a TypeError
will be thrown.
This method has a custom variant for promises that is available using\ntimersPromises.setImmediate()
.
Schedules repeated execution of callback
every delay
milliseconds.
When delay
is larger than 2147483647
or less than 1
, the delay
will be\nset to 1
. Non-integer delays are truncated to an integer.
If callback
is not a function, a TypeError
will be thrown.
This method has a custom variant for promises that is available using\ntimersPromises.setInterval()
.
Schedules execution of a one-time callback
after delay
milliseconds.
The callback
will likely not be invoked in precisely delay
milliseconds.\nNode.js makes no guarantees about the exact timing of when callbacks will fire,\nnor of their ordering. The callback will be called as close as possible to the\ntime specified.
When delay
is larger than 2147483647
or less than 1
, the delay
\nwill be set to 1
. Non-integer delays are truncated to an integer.
If callback
is not a function, a TypeError
will be thrown.
This method has a custom variant for promises that is available using\ntimersPromises.setTimeout()
.
The setImmediate()
, setInterval()
, and setTimeout()
methods\neach return objects that represent the scheduled timers. These can be used to\ncancel the timer and prevent it from triggering.
For the promisified variants of setImmediate()
and setTimeout()
,\nan AbortController
may be used to cancel the timer. When canceled, the\nreturned Promises will be rejected with an 'AbortError'
.
For setImmediate()
:
const { setImmediate: setImmediatePromise } = require('node:timers/promises');\n\nconst ac = new AbortController();\nconst signal = ac.signal;\n\nsetImmediatePromise('foobar', { signal })\n .then(console.log)\n .catch((err) => {\n if (err.name === 'AbortError')\n console.error('The immediate was aborted');\n });\n\nac.abort();\n
\nFor setTimeout()
:
const { setTimeout: setTimeoutPromise } = require('node:timers/promises');\n\nconst ac = new AbortController();\nconst signal = ac.signal;\n\nsetTimeoutPromise(1000, 'foobar', { signal })\n .then(console.log)\n .catch((err) => {\n if (err.name === 'AbortError')\n console.error('The timeout was aborted');\n });\n\nac.abort();\n
",
"methods": [
{
"textRaw": "`clearImmediate(immediate)`",
"type": "method",
"name": "clearImmediate",
"meta": {
"added": [
"v0.9.1"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`immediate` {Immediate} An `Immediate` object as returned by [`setImmediate()`][].",
"name": "immediate",
"type": "Immediate",
"desc": "An `Immediate` object as returned by [`setImmediate()`][]."
}
]
}
],
"desc": "Cancels an Immediate
object created by setImmediate()
.
Cancels a Timeout
object created by setInterval()
.
Cancels a Timeout
object created by setTimeout()
.
The timers/promises
API provides an alternative set of timer functions\nthat return Promise
objects. The API is accessible via\nrequire('node:timers/promises')
.
import {\n setTimeout,\n setImmediate,\n setInterval,\n} from 'timers/promises';\n
\nconst {\n setTimeout,\n setImmediate,\n setInterval,\n} = require('node:timers/promises');\n
",
"methods": [
{
"textRaw": "`timersPromises.setTimeout([delay[, value[, options]]])`",
"type": "method",
"name": "setTimeout",
"meta": {
"added": [
"v15.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`delay` {number} The number of milliseconds to wait before fulfilling the promise. **Default:** `1`.",
"name": "delay",
"type": "number",
"default": "`1`",
"desc": "The number of milliseconds to wait before fulfilling the promise."
},
{
"textRaw": "`value` {any} A value with which the promise is fulfilled.",
"name": "value",
"type": "any",
"desc": "A value with which the promise is fulfilled."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`ref` {boolean} Set to `false` to indicate that the scheduled `Timeout` should not require the Node.js event loop to remain active. **Default:** `true`.",
"name": "ref",
"type": "boolean",
"default": "`true`",
"desc": "Set to `false` to indicate that the scheduled `Timeout` should not require the Node.js event loop to remain active."
},
{
"textRaw": "`signal` {AbortSignal} An optional `AbortSignal` that can be used to cancel the scheduled `Timeout`.",
"name": "signal",
"type": "AbortSignal",
"desc": "An optional `AbortSignal` that can be used to cancel the scheduled `Timeout`."
}
]
}
]
}
],
"desc": "import {\n setTimeout,\n} from 'timers/promises';\n\nconst res = await setTimeout(100, 'result');\n\nconsole.log(res); // Prints 'result'\n
\nconst {\n setTimeout,\n} = require('node:timers/promises');\n\nsetTimeout(100, 'result').then((res) => {\n console.log(res); // Prints 'result'\n});\n
"
},
{
"textRaw": "`timersPromises.setImmediate([value[, options]])`",
"type": "method",
"name": "setImmediate",
"meta": {
"added": [
"v15.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`value` {any} A value with which the promise is fulfilled.",
"name": "value",
"type": "any",
"desc": "A value with which the promise is fulfilled."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`ref` {boolean} Set to `false` to indicate that the scheduled `Immediate` should not require the Node.js event loop to remain active. **Default:** `true`.",
"name": "ref",
"type": "boolean",
"default": "`true`",
"desc": "Set to `false` to indicate that the scheduled `Immediate` should not require the Node.js event loop to remain active."
},
{
"textRaw": "`signal` {AbortSignal} An optional `AbortSignal` that can be used to cancel the scheduled `Immediate`.",
"name": "signal",
"type": "AbortSignal",
"desc": "An optional `AbortSignal` that can be used to cancel the scheduled `Immediate`."
}
]
}
]
}
],
"desc": "import {\n setImmediate,\n} from 'timers/promises';\n\nconst res = await setImmediate('result');\n\nconsole.log(res); // Prints 'result'\n
\nconst {\n setImmediate,\n} = require('node:timers/promises');\n\nsetImmediate('result').then((res) => {\n console.log(res); // Prints 'result'\n});\n
"
},
{
"textRaw": "`timersPromises.setInterval([delay[, value[, options]]])`",
"type": "method",
"name": "setInterval",
"meta": {
"added": [
"v15.9.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Returns an async iterator that generates values in an interval of delay
ms.\nIf ref
is true
, you need to call next()
of async iterator explicitly\nor implicitly to keep the event loop alive.
delay
<number> The number of milliseconds to wait between iterations.\nDefault: 1
.value
<any> A value with which the iterator returns.options
<Object>\nref
<boolean> Set to false
to indicate that the scheduled Timeout
\nbetween iterations should not require the Node.js event loop to\nremain active.\nDefault: true
.signal
<AbortSignal> An optional AbortSignal
that can be used to\ncancel the scheduled Timeout
between operations.import {\n setInterval,\n} from 'timers/promises';\n\nconst interval = 100;\nfor await (const startTime of setInterval(interval, Date.now())) {\n const now = Date.now();\n console.log(now);\n if ((now - startTime) > 1000)\n break;\n}\nconsole.log(Date.now());\n
\nconst {\n setInterval,\n} = require('node:timers/promises');\nconst interval = 100;\n\n(async function() {\n for await (const startTime of setInterval(interval, Date.now())) {\n const now = Date.now();\n console.log(now);\n if ((now - startTime) > 1000)\n break;\n }\n console.log(Date.now());\n})();\n
"
},
{
"textRaw": "`timersPromises.scheduler.wait(delay[, options])`",
"type": "method",
"name": "wait",
"meta": {
"added": [
"v17.3.0",
"v16.14.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise}",
"name": "return",
"type": "Promise"
},
"params": [
{
"textRaw": "`delay` {number} The number of milliseconds to wait before resolving the promise.",
"name": "delay",
"type": "number",
"desc": "The number of milliseconds to wait before resolving the promise."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`signal` {AbortSignal} An optional `AbortSignal` that can be used to cancel waiting.",
"name": "signal",
"type": "AbortSignal",
"desc": "An optional `AbortSignal` that can be used to cancel waiting."
}
]
}
]
}
],
"desc": "An experimental API defined by the Scheduling APIs draft specification\nbeing developed as a standard Web Platform API.
\nCalling timersPromises.scheduler.wait(delay, options)
is roughly equivalent\nto calling timersPromises.setTimeout(delay, undefined, options)
except that\nthe ref
option is not supported.
import { scheduler } from 'node:timers/promises';\n\nawait scheduler.wait(1000); // Wait one second before continuing\n
"
},
{
"textRaw": "`timersPromises.scheduler.yield()`",
"type": "method",
"name": "yield",
"meta": {
"added": [
"v17.3.0",
"v16.14.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise}",
"name": "return",
"type": "Promise"
},
"params": []
}
],
"desc": "An experimental API defined by the Scheduling APIs draft specification\nbeing developed as a standard Web Platform API.
\nCalling timersPromises.scheduler.yield()
is equivalent to calling\ntimersPromises.setImmediate()
with no arguments.
Source Code: lib/tls.js
\nThe node:tls
module provides an implementation of the Transport Layer Security\n(TLS) and Secure Socket Layer (SSL) protocols that is built on top of OpenSSL.\nThe module can be accessed using:
const tls = require('node:tls');\n
",
"modules": [
{
"textRaw": "Determining if crypto support is unavailable",
"name": "determining_if_crypto_support_is_unavailable",
"desc": "It is possible for Node.js to be built without including support for the\nnode:crypto
module. In such cases, attempting to import
from tls
or\ncalling require('node:tls')
will result in an error being thrown.
When using CommonJS, the error thrown can be caught using try/catch:
\nlet tls;\ntry {\n tls = require('node:tls');\n} catch (err) {\n console.error('tls support is disabled!');\n}\n
\nWhen using the lexical ESM import
keyword, the error can only be\ncaught if a handler for process.on('uncaughtException')
is registered\nbefore any attempt to load the module is made (using, for instance,\na preload module).
When using ESM, if there is a chance that the code may be run on a build\nof Node.js where crypto support is not enabled, consider using the\nimport()
function instead of the lexical import
keyword:
let tls;\ntry {\n tls = await import('node:tls');\n} catch (err) {\n console.error('tls support is disabled!');\n}\n
",
"type": "module",
"displayName": "Determining if crypto support is unavailable"
},
{
"textRaw": "TLS/SSL concepts",
"name": "tls/ssl_concepts",
"desc": "TLS/SSL is a set of protocols that rely on a public key infrastructure (PKI) to\nenable secure communication between a client and a server. For most common\ncases, each server must have a private key.
\nPrivate keys can be generated in multiple ways. The example below illustrates\nuse of the OpenSSL command-line interface to generate a 2048-bit RSA private\nkey:
\nopenssl genrsa -out ryans-key.pem 2048\n
\nWith TLS/SSL, all servers (and some clients) must have a certificate.\nCertificates are public keys that correspond to a private key, and that are\ndigitally signed either by a Certificate Authority or by the owner of the\nprivate key (such certificates are referred to as \"self-signed\"). The first\nstep to obtaining a certificate is to create a Certificate Signing Request\n(CSR) file.
\nThe OpenSSL command-line interface can be used to generate a CSR for a private\nkey:
\nopenssl req -new -sha256 -key ryans-key.pem -out ryans-csr.pem\n
\nOnce the CSR file is generated, it can either be sent to a Certificate\nAuthority for signing or used to generate a self-signed certificate.
\nCreating a self-signed certificate using the OpenSSL command-line interface\nis illustrated in the example below:
\nopenssl x509 -req -in ryans-csr.pem -signkey ryans-key.pem -out ryans-cert.pem\n
\nOnce the certificate is generated, it can be used to generate a .pfx
or\n.p12
file:
openssl pkcs12 -export -in ryans-cert.pem -inkey ryans-key.pem \\\n -certfile ca-cert.pem -out ryans.pfx\n
\nWhere:
\nin
: is the signed certificateinkey
: is the associated private keycertfile
: is a concatenation of all Certificate Authority (CA) certs into\na single file, e.g. cat ca1-cert.pem ca2-cert.pem > ca-cert.pem
The term forward secrecy or perfect forward secrecy describes a feature\nof key-agreement (i.e., key-exchange) methods. That is, the server and client\nkeys are used to negotiate new temporary keys that are used specifically and\nonly for the current communication session. Practically, this means that even\nif the server's private key is compromised, communication can only be decrypted\nby eavesdroppers if the attacker manages to obtain the key-pair specifically\ngenerated for the session.
\nPerfect forward secrecy is achieved by randomly generating a key pair for\nkey-agreement on every TLS/SSL handshake (in contrast to using the same key for\nall sessions). Methods implementing this technique are called \"ephemeral\".
\nCurrently two methods are commonly used to achieve perfect forward secrecy (note\nthe character \"E\" appended to the traditional abbreviations):
\nPerfect forward secrecy using ECDHE is enabled by default. The ecdhCurve
\noption can be used when creating a TLS server to customize the list of supported\nECDH curves to use. See tls.createServer()
for more info.
DHE is disabled by default but can be enabled alongside ECDHE by setting the\ndhparam
option to 'auto'
. Custom DHE parameters are also supported but\ndiscouraged in favor of automatically selected, well-known parameters.
Perfect forward secrecy was optional up to TLSv1.2. As of TLSv1.3, (EC)DHE is\nalways used (with the exception of PSK-only connections).
" }, { "textRaw": "ALPN and SNI", "name": "ALPN and SNI", "type": "misc", "desc": "ALPN (Application-Layer Protocol Negotiation Extension) and\nSNI (Server Name Indication) are TLS handshake extensions:
\nTLS-PSK support is available as an alternative to normal certificate-based\nauthentication. It uses a pre-shared key instead of certificates to\nauthenticate a TLS connection, providing mutual authentication.\nTLS-PSK and public key infrastructure are not mutually exclusive. Clients and\nservers can accommodate both, choosing either of them during the normal cipher\nnegotiation step.
\nTLS-PSK is only a good choice where means exist to securely share a\nkey with every connecting machine, so it does not replace the public key\ninfrastructure (PKI) for the majority of TLS uses.\nThe TLS-PSK implementation in OpenSSL has seen many security flaws in\nrecent years, mostly because it is used only by a minority of applications.\nPlease consider all alternative solutions before switching to PSK ciphers.\nUpon generating PSK it is of critical importance to use sufficient entropy as\ndiscussed in RFC 4086. Deriving a shared secret from a password or other\nlow-entropy sources is not secure.
\nPSK ciphers are disabled by default, and using TLS-PSK thus requires explicitly\nspecifying a cipher suite with the ciphers
option. The list of available\nciphers can be retrieved via openssl ciphers -v 'PSK'
. All TLS 1.3\nciphers are eligible for PSK and can be retrieved via\nopenssl ciphers -v -s -tls1_3 -psk
.
According to the RFC 4279, PSK identities up to 128 bytes in length and\nPSKs up to 64 bytes in length must be supported. As of OpenSSL 1.1.0\nmaximum identity size is 128 bytes, and maximum PSK length is 256 bytes.
\nThe current implementation doesn't support asynchronous PSK callbacks due to the\nlimitations of the underlying OpenSSL API.
" }, { "textRaw": "Client-initiated renegotiation attack mitigation", "name": "Client-initiated renegotiation attack mitigation", "type": "misc", "desc": "The TLS protocol allows clients to renegotiate certain aspects of the TLS\nsession. Unfortunately, session renegotiation requires a disproportionate amount\nof server-side resources, making it a potential vector for denial-of-service\nattacks.
\nTo mitigate the risk, renegotiation is limited to three times every ten minutes.\nAn 'error'
event is emitted on the tls.TLSSocket
instance when this\nthreshold is exceeded. The limits are configurable:
tls.CLIENT_RENEG_LIMIT
<number> Specifies the number of renegotiation\nrequests. Default: 3
.tls.CLIENT_RENEG_WINDOW
<number> Specifies the time renegotiation window\nin seconds. Default: 600
(10 minutes).The default renegotiation limits should not be modified without a full\nunderstanding of the implications and risks.
\nTLSv1.3 does not support renegotiation.
" } ], "modules": [ { "textRaw": "Session resumption", "name": "session_resumption", "desc": "Establishing a TLS session can be relatively slow. The process can be sped\nup by saving and later reusing the session state. There are several mechanisms\nto do so, discussed here from oldest to newest (and preferred).
", "modules": [ { "textRaw": "Session identifiers", "name": "session_identifiers", "desc": "Servers generate a unique ID for new connections and\nsend it to the client. Clients and servers save the session state. When\nreconnecting, clients send the ID of their saved session state and if the server\nalso has the state for that ID, it can agree to use it. Otherwise, the server\nwill create a new session. See RFC 2246 for more information, page 23 and\n30.
\nResumption using session identifiers is supported by most web browsers when\nmaking HTTPS requests.
\nFor Node.js, clients wait for the 'session'
event to get the session data,\nand provide the data to the session
option of a subsequent tls.connect()
\nto reuse the session. Servers must\nimplement handlers for the 'newSession'
and 'resumeSession'
events\nto save and restore the session data using the session ID as the lookup key to\nreuse sessions. To reuse sessions across load balancers or cluster workers,\nservers must use a shared session cache (such as Redis) in their session\nhandlers.
The servers encrypt the entire session state and send it\nto the client as a \"ticket\". When reconnecting, the state is sent to the server\nin the initial connection. This mechanism avoids the need for a server-side\nsession cache. If the server doesn't use the ticket, for any reason (failure\nto decrypt it, it's too old, etc.), it will create a new session and send a new\nticket. See RFC 5077 for more information.
\nResumption using session tickets is becoming commonly supported by many web\nbrowsers when making HTTPS requests.
\nFor Node.js, clients use the same APIs for resumption with session identifiers\nas for resumption with session tickets. For debugging, if\ntls.TLSSocket.getTLSTicket()
returns a value, the session data contains a\nticket, otherwise it contains client-side session state.
With TLSv1.3, be aware that multiple tickets may be sent by the server,\nresulting in multiple 'session'
events, see 'session'
for more\ninformation.
Single process servers need no specific implementation to use session tickets.\nTo use session tickets across server restarts or load balancers, servers must\nall have the same ticket keys. There are three 16-byte keys internally, but the\ntls API exposes them as a single 48-byte buffer for convenience.
\nIt's possible to get the ticket keys by calling server.getTicketKeys()
on\none server instance and then distribute them, but it is more reasonable to\nsecurely generate 48 bytes of secure random data and set them with the\nticketKeys
option of tls.createServer()
. The keys should be regularly\nregenerated and server's keys can be reset with\nserver.setTicketKeys()
.
Session ticket keys are cryptographic keys, and they must be stored\nsecurely. With TLS 1.2 and below, if they are compromised all sessions that\nused tickets encrypted with them can be decrypted. They should not be stored\non disk, and they should be regenerated regularly.
\nIf clients advertise support for tickets, the server will send them. The\nserver can disable tickets by supplying\nrequire('node:constants').SSL_OP_NO_TICKET
in secureOptions
.
Both session identifiers and session tickets timeout, causing the server to\ncreate new sessions. The timeout can be configured with the sessionTimeout
\noption of tls.createServer()
.
For all the mechanisms, when resumption fails, servers will create new sessions.\nSince failing to resume the session does not cause TLS/HTTPS connection\nfailures, it is easy to not notice unnecessarily poor TLS performance. The\nOpenSSL CLI can be used to verify that servers are resuming sessions. Use the\n-reconnect
option to openssl s_client
, for example:
openssl s_client -connect localhost:443 -reconnect\n
\nRead through the debug output. The first connection should say \"New\", for\nexample:
\nNew, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256\n
\nSubsequent connections should say \"Reused\", for example:
\nReused, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256\n
",
"type": "module",
"displayName": "Session tickets"
}
],
"type": "module",
"displayName": "Session resumption"
}
],
"type": "module",
"displayName": "TLS/SSL concepts"
},
{
"textRaw": "Modifying the default TLS cipher suite",
"name": "modifying_the_default_tls_cipher_suite",
"desc": "Node.js is built with a default suite of enabled and disabled TLS ciphers. This\ndefault cipher list can be configured when building Node.js to allow\ndistributions to provide their own default list.
\nThe following command can be used to show the default cipher suite:
\nnode -p crypto.constants.defaultCoreCipherList | tr ':' '\\n'\nTLS_AES_256_GCM_SHA384\nTLS_CHACHA20_POLY1305_SHA256\nTLS_AES_128_GCM_SHA256\nECDHE-RSA-AES128-GCM-SHA256\nECDHE-ECDSA-AES128-GCM-SHA256\nECDHE-RSA-AES256-GCM-SHA384\nECDHE-ECDSA-AES256-GCM-SHA384\nDHE-RSA-AES128-GCM-SHA256\nECDHE-RSA-AES128-SHA256\nDHE-RSA-AES128-SHA256\nECDHE-RSA-AES256-SHA384\nDHE-RSA-AES256-SHA384\nECDHE-RSA-AES256-SHA256\nDHE-RSA-AES256-SHA256\nHIGH\n!aNULL\n!eNULL\n!EXPORT\n!DES\n!RC4\n!MD5\n!PSK\n!SRP\n!CAMELLIA\n
\nThis default can be replaced entirely using the --tls-cipher-list
\ncommand-line switch (directly, or via the NODE_OPTIONS
environment\nvariable). For instance, the following makes ECDHE-RSA-AES128-GCM-SHA256:!RC4
\nthe default TLS cipher suite:
node --tls-cipher-list='ECDHE-RSA-AES128-GCM-SHA256:!RC4' server.js\n\nexport NODE_OPTIONS=--tls-cipher-list='ECDHE-RSA-AES128-GCM-SHA256:!RC4'\nnode server.js\n
\nTo verify, use the following command to show the set cipher list, note the\ndifference between defaultCoreCipherList
and defaultCipherList
:
node --tls-cipher-list='ECDHE-RSA-AES128-GCM-SHA256:!RC4' -p crypto.constants.defaultCipherList | tr ':' '\\n'\nECDHE-RSA-AES128-GCM-SHA256\n!RC4\n
\ni.e. the defaultCoreCipherList
list is set at compilation time and the\ndefaultCipherList
is set at runtime.
To modify the default cipher suites from within the runtime, modify the\ntls.DEFAULT_CIPHERS
variable, this must be performed before listening on any\nsockets, it will not affect sockets already opened. For example:
// Remove Obsolete CBC Ciphers and RSA Key Exchange based Ciphers as they don't provide Forward Secrecy\ntls.DEFAULT_CIPHERS +=\n ':!ECDHE-RSA-AES128-SHA:!ECDHE-RSA-AES128-SHA256:!ECDHE-RSA-AES256-SHA:!ECDHE-RSA-AES256-SHA384' +\n ':!ECDHE-ECDSA-AES128-SHA:!ECDHE-ECDSA-AES128-SHA256:!ECDHE-ECDSA-AES256-SHA:!ECDHE-ECDSA-AES256-SHA384' +\n ':!kRSA';\n
\nThe default can also be replaced on a per client or server basis using the\nciphers
option from tls.createSecureContext()
, which is also available\nin tls.createServer()
, tls.connect()
, and when creating new\ntls.TLSSocket
s.
The ciphers list can contain a mixture of TLSv1.3 cipher suite names, the ones\nthat start with 'TLS_'
, and specifications for TLSv1.2 and below cipher\nsuites. The TLSv1.2 ciphers support a legacy specification format, consult\nthe OpenSSL cipher list format documentation for details, but those\nspecifications do not apply to TLSv1.3 ciphers. The TLSv1.3 suites can only\nbe enabled by including their full name in the cipher list. They cannot, for\nexample, be enabled or disabled by using the legacy TLSv1.2 'EECDH'
or\n'!EECDH'
specification.
Despite the relative order of TLSv1.3 and TLSv1.2 cipher suites, the TLSv1.3\nprotocol is significantly more secure than TLSv1.2, and will always be chosen\nover TLSv1.2 if the handshake indicates it is supported, and if any TLSv1.3\ncipher suites are enabled.
\nThe default cipher suite included within Node.js has been carefully\nselected to reflect current security best practices and risk mitigation.\nChanging the default cipher suite can have a significant impact on the security\nof an application. The --tls-cipher-list
switch and ciphers
option should by\nused only if absolutely necessary.
The default cipher suite prefers GCM ciphers for Chrome's 'modern\ncryptography' setting and also prefers ECDHE and DHE ciphers for perfect\nforward secrecy, while offering some backward compatibility.
\nOld clients that rely on insecure and deprecated RC4 or DES-based ciphers\n(like Internet Explorer 6) cannot complete the handshaking process with\nthe default configuration. If these clients must be supported, the\nTLS recommendations may offer a compatible cipher suite. For more details\non the format, see the OpenSSL cipher list format documentation.
\nThere are only five TLSv1.3 cipher suites:
\n'TLS_AES_256_GCM_SHA384'
'TLS_CHACHA20_POLY1305_SHA256'
'TLS_AES_128_GCM_SHA256'
'TLS_AES_128_CCM_SHA256'
'TLS_AES_128_CCM_8_SHA256'
The first three are enabled by default. The two CCM
-based suites are supported\nby TLSv1.3 because they may be more performant on constrained systems, but they\nare not enabled by default since they offer less security.
Multiple functions can fail due to certificate errors that are reported by\nOpenSSL. In such a case, the function provides an <Error> via its callback that\nhas the property code
which can take one of the following values:
'UNABLE_TO_GET_ISSUER_CERT'
: Unable to get issuer certificate.'UNABLE_TO_GET_CRL'
: Unable to get certificate CRL.'UNABLE_TO_DECRYPT_CERT_SIGNATURE'
: Unable to decrypt certificate's\nsignature.'UNABLE_TO_DECRYPT_CRL_SIGNATURE'
: Unable to decrypt CRL's signature.'UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY'
: Unable to decode issuer public key.'CERT_SIGNATURE_FAILURE'
: Certificate signature failure.'CRL_SIGNATURE_FAILURE'
: CRL signature failure.'CERT_NOT_YET_VALID'
: Certificate is not yet valid.'CERT_HAS_EXPIRED'
: Certificate has expired.'CRL_NOT_YET_VALID'
: CRL is not yet valid.'CRL_HAS_EXPIRED'
: CRL has expired.'ERROR_IN_CERT_NOT_BEFORE_FIELD'
: Format error in certificate's notBefore\nfield.'ERROR_IN_CERT_NOT_AFTER_FIELD'
: Format error in certificate's notAfter\nfield.'ERROR_IN_CRL_LAST_UPDATE_FIELD'
: Format error in CRL's lastUpdate field.'ERROR_IN_CRL_NEXT_UPDATE_FIELD'
: Format error in CRL's nextUpdate field.'OUT_OF_MEM'
: Out of memory.'DEPTH_ZERO_SELF_SIGNED_CERT'
: Self signed certificate.'SELF_SIGNED_CERT_IN_CHAIN'
: Self signed certificate in certificate chain.'UNABLE_TO_GET_ISSUER_CERT_LOCALLY'
: Unable to get local issuer certificate.'UNABLE_TO_VERIFY_LEAF_SIGNATURE'
: Unable to verify the first certificate.'CERT_CHAIN_TOO_LONG'
: Certificate chain too long.'CERT_REVOKED'
: Certificate revoked.'INVALID_CA'
: Invalid CA certificate.'PATH_LENGTH_EXCEEDED'
: Path length constraint exceeded.'INVALID_PURPOSE'
: Unsupported certificate purpose.'CERT_UNTRUSTED'
: Certificate not trusted.'CERT_REJECTED'
: Certificate rejected.'HOSTNAME_MISMATCH'
: Hostname mismatch.The tls.CryptoStream
class represents a stream of encrypted data. This class\nis deprecated and should no longer be used.
The cryptoStream.bytesWritten
property returns the total number of bytes\nwritten to the underlying socket including the bytes required for the\nimplementation of the TLS protocol.
Returned by tls.createSecurePair()
.
The 'secure'
event is emitted by the SecurePair
object once a secure\nconnection has been established.
As with checking for the server\n'secureConnection'
\nevent, pair.cleartext.authorized
should be inspected to confirm whether the\ncertificate used is properly authorized.
Accepts encrypted connections using TLS or SSL.
", "events": [ { "textRaw": "Event: `'connection'`", "type": "event", "name": "connection", "meta": { "added": [ "v0.3.2" ], "changes": [] }, "params": [ { "textRaw": "`socket` {stream.Duplex}", "name": "socket", "type": "stream.Duplex" } ], "desc": "This event is emitted when a new TCP stream is established, before the TLS\nhandshake begins. socket
is typically an object of type net.Socket
but\nwill not receive events unlike the socket created from the net.Server
\n'connection'
event. Usually users will not want to access this event.
This event can also be explicitly emitted by users to inject connections\ninto the TLS server. In that case, any Duplex
stream can be passed.
The keylog
event is emitted when key material is generated or received by\na connection to this server (typically before handshake has completed, but not\nnecessarily). This keying material can be stored for debugging, as it allows\ncaptured TLS traffic to be decrypted. It may be emitted multiple times for\neach socket.
A typical use case is to append received lines to a common text file, which\nis later used by software (such as Wireshark) to decrypt the traffic:
\nconst logFile = fs.createWriteStream('/tmp/ssl-keys.log', { flags: 'a' });\n// ...\nserver.on('keylog', (line, tlsSocket) => {\n if (tlsSocket.remoteAddress !== '...')\n return; // Only log keys for a particular IP\n logFile.write(line);\n});\n
"
},
{
"textRaw": "Event: `'newSession'`",
"type": "event",
"name": "newSession",
"meta": {
"added": [
"v0.9.2"
],
"changes": [
{
"version": "v0.11.12",
"pr-url": "https://github.com/nodejs/node-v0.x-archive/pull/7118",
"description": "The `callback` argument is now supported."
}
]
},
"params": [],
"desc": "The 'newSession'
event is emitted upon creation of a new TLS session. This may\nbe used to store sessions in external storage. The data should be provided to\nthe 'resumeSession'
callback.
The listener callback is passed three arguments when called:
\nsessionId
<Buffer> The TLS session identifiersessionData
<Buffer> The TLS session datacallback
<Function> A callback function taking no arguments that must be\ninvoked in order for data to be sent or received over the secure connection.Listening for this event will have an effect only on connections established\nafter the addition of the event listener.
" }, { "textRaw": "Event: `'OCSPRequest'`", "type": "event", "name": "OCSPRequest", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "params": [], "desc": "The 'OCSPRequest'
event is emitted when the client sends a certificate status\nrequest. The listener callback is passed three arguments when called:
certificate
<Buffer> The server certificateissuer
<Buffer> The issuer's certificatecallback
<Function> A callback function that must be invoked to provide\nthe results of the OCSP request.The server's current certificate can be parsed to obtain the OCSP URL\nand certificate ID; after obtaining an OCSP response, callback(null, resp)
is\nthen invoked, where resp
is a Buffer
instance containing the OCSP response.\nBoth certificate
and issuer
are Buffer
DER-representations of the\nprimary and issuer's certificates. These can be used to obtain the OCSP\ncertificate ID and OCSP endpoint URL.
Alternatively, callback(null, null)
may be called, indicating that there was\nno OCSP response.
Calling callback(err)
will result in a socket.destroy(err)
call.
The typical flow of an OCSP request is as follows:
\n'OCSPRequest'
(via the status\ninfo extension in ClientHello).'OCSPRequest'
event, calling the\nlistener if registered.certificate
or issuer
and\nperforms an OCSP request to the CA.'OCSPResponse'
from the CA and sends it back to the client\nvia the callback
argumentThe issuer
can be null
if the certificate is either self-signed or the\nissuer is not in the root certificates list. (An issuer may be provided\nvia the ca
option when establishing the TLS connection.)
Listening for this event will have an effect only on connections established\nafter the addition of the event listener.
\nAn npm module like asn1.js may be used to parse the certificates.
" }, { "textRaw": "Event: `'resumeSession'`", "type": "event", "name": "resumeSession", "meta": { "added": [ "v0.9.2" ], "changes": [] }, "params": [], "desc": "The 'resumeSession'
event is emitted when the client requests to resume a\nprevious TLS session. The listener callback is passed two arguments when\ncalled:
sessionId
<Buffer> The TLS session identifiercallback
<Function> A callback function to be called when the prior session\nhas been recovered: callback([err[, sessionData]])
\n\nThe event listener should perform a lookup in external storage for the\nsessionData
saved by the 'newSession'
event handler using the given\nsessionId
. If found, call callback(null, sessionData)
to resume the session.\nIf not found, the session cannot be resumed. callback()
must be called\nwithout sessionData
so that the handshake can continue and a new session can\nbe created. It is possible to call callback(err)
to terminate the incoming\nconnection and destroy the socket.
Listening for this event will have an effect only on connections established\nafter the addition of the event listener.
\nThe following illustrates resuming a TLS session:
\nconst tlsSessionStore = {};\nserver.on('newSession', (id, data, cb) => {\n tlsSessionStore[id.toString('hex')] = data;\n cb();\n});\nserver.on('resumeSession', (id, cb) => {\n cb(null, tlsSessionStore[id.toString('hex')] || null);\n});\n
"
},
{
"textRaw": "Event: `'secureConnection'`",
"type": "event",
"name": "secureConnection",
"meta": {
"added": [
"v0.3.2"
],
"changes": []
},
"params": [],
"desc": "The 'secureConnection'
event is emitted after the handshaking process for a\nnew connection has successfully completed. The listener callback is passed a\nsingle argument when called:
tlsSocket
<tls.TLSSocket> The established TLS socket.The tlsSocket.authorized
property is a boolean
indicating whether the\nclient has been verified by one of the supplied Certificate Authorities for the\nserver. If tlsSocket.authorized
is false
, then socket.authorizationError
\nis set to describe how authorization failed. Depending on the settings\nof the TLS server, unauthorized connections may still be accepted.
The tlsSocket.alpnProtocol
property is a string that contains the selected\nALPN protocol. When ALPN has no selected protocol because the client or the\nserver did not send an ALPN extension, tlsSocket.alpnProtocol
equals false
.
The tlsSocket.servername
property is a string containing the server name\nrequested via SNI.
The 'tlsClientError'
event is emitted when an error occurs before a secure\nconnection is established. The listener callback is passed two arguments when\ncalled:
exception
<Error> The Error
object describing the errortlsSocket
<tls.TLSSocket> The tls.TLSSocket
instance from which the\nerror originated.The server.addContext()
method adds a secure context that will be used if\nthe client request's SNI name matches the supplied hostname
(or wildcard).
When there are multiple matching contexts, the most recently added one is\nused.
" }, { "textRaw": "`server.address()`", "type": "method", "name": "address", "meta": { "added": [ "v0.6.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "Returns the bound address, the address family name, and port of the\nserver as reported by the operating system. See net.Server.address()
for\nmore information.
The server.close()
method stops the server from accepting new connections.
This function operates asynchronously. The 'close'
event will be emitted\nwhen the server has no more open connections.
Returns the session ticket keys.
\nSee Session Resumption for more information.
" }, { "textRaw": "`server.listen()`", "type": "method", "name": "listen", "signatures": [ { "params": [] } ], "desc": "Starts the server listening for encrypted connections.\nThis method is identical to server.listen()
from net.Server
.
The server.setSecureContext()
method replaces the secure context of an\nexisting server. Existing connections to the server are not interrupted.
Sets the session ticket keys.
\nChanges to the ticket keys are effective only for future server connections.\nExisting or currently pending server connections will use the previous keys.
\nSee Session Resumption for more information.
" } ] }, { "textRaw": "Class: `tls.TLSSocket`", "type": "class", "name": "tls.TLSSocket", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Performs transparent encryption of written data and all required TLS\nnegotiation.
\nInstances of tls.TLSSocket
implement the duplex Stream interface.
Methods that return TLS connection metadata (e.g.\ntls.TLSSocket.getPeerCertificate()
) will only return data while the\nconnection is open.
The keylog
event is emitted on a tls.TLSSocket
when key material\nis generated or received by the socket. This keying material can be stored\nfor debugging, as it allows captured TLS traffic to be decrypted. It may\nbe emitted multiple times, before or after the handshake completes.
A typical use case is to append received lines to a common text file, which\nis later used by software (such as Wireshark) to decrypt the traffic:
\nconst logFile = fs.createWriteStream('/tmp/ssl-keys.log', { flags: 'a' });\n// ...\ntlsSocket.on('keylog', (line) => logFile.write(line));\n
"
},
{
"textRaw": "Event: `'OCSPResponse'`",
"type": "event",
"name": "OCSPResponse",
"meta": {
"added": [
"v0.11.13"
],
"changes": []
},
"params": [],
"desc": "The 'OCSPResponse'
event is emitted if the requestOCSP
option was set\nwhen the tls.TLSSocket
was created and an OCSP response has been received.\nThe listener callback is passed a single argument when called:
response
<Buffer> The server's OCSP responseTypically, the response
is a digitally signed object from the server's CA that\ncontains information about server's certificate revocation status.
The 'secureConnect'
event is emitted after the handshaking process for a new\nconnection has successfully completed. The listener callback will be called\nregardless of whether or not the server's certificate has been authorized. It\nis the client's responsibility to check the tlsSocket.authorized
property to\ndetermine if the server certificate was signed by one of the specified CAs. If\ntlsSocket.authorized === false
, then the error can be found by examining the\ntlsSocket.authorizationError
property. If ALPN was used, the\ntlsSocket.alpnProtocol
property can be checked to determine the negotiated\nprotocol.
The 'secureConnect'
event is not emitted when a <tls.TLSSocket> is created\nusing the new tls.TLSSocket()
constructor.
The 'session'
event is emitted on a client tls.TLSSocket
when a new session\nor TLS ticket is available. This may or may not be before the handshake is\ncomplete, depending on the TLS protocol version that was negotiated. The event\nis not emitted on the server, or if a new session was not created, for example,\nwhen the connection was resumed. For some TLS protocol versions the event may be\nemitted multiple times, in which case all the sessions can be used for\nresumption.
On the client, the session
can be provided to the session
option of\ntls.connect()
to resume the connection.
See Session Resumption for more information.
\nFor TLSv1.2 and below, tls.TLSSocket.getSession()
can be called once\nthe handshake is complete. For TLSv1.3, only ticket-based resumption is allowed\nby the protocol, multiple tickets are sent, and the tickets aren't sent until\nafter the handshake completes. So it is necessary to wait for the\n'session'
event to get a resumable session. Applications\nshould use the 'session'
event instead of getSession()
to ensure\nthey will work for all TLS versions. Applications that only expect to\nget or use one session should listen for this event only once:
tlsSocket.once('session', (session) => {\n // The session can be used immediately or later.\n tls.connect({\n session: session,\n // Other connect options...\n });\n});\n
"
}
],
"methods": [
{
"textRaw": "`tlsSocket.address()`",
"type": "method",
"name": "address",
"meta": {
"added": [
"v0.11.4"
],
"changes": [
{
"version": "v18.4.0",
"pr-url": "https://github.com/nodejs/node/pull/43054",
"description": "The `family` property now returns a string instead of a number."
},
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41431",
"description": "The `family` property now returns a number instead of a string."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Returns the bound address
, the address family
name, and port
of the\nunderlying socket as reported by the operating system:\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
.
Disables TLS renegotiation for this TLSSocket
instance. Once called, attempts\nto renegotiate will trigger an 'error'
event on the TLSSocket
.
When enabled, TLS packet trace information is written to stderr
. This can be\nused to debug TLS connection problems.
The format of the output is identical to the output of\nopenssl s_client -trace
or openssl s_server -trace
. While it is produced by\nOpenSSL's SSL_trace()
function, the format is undocumented, can change\nwithout notice, and should not be relied on.
Keying material is used for validations to prevent different kind of attacks in\nnetwork protocols, for example in the specifications of IEEE 802.1X.
\nExample
\nconst keyingMaterial = tlsSocket.exportKeyingMaterial(\n 128,\n 'client finished');\n\n/*\n Example return value of keyingMaterial:\n <Buffer 76 26 af 99 c5 56 8e 42 09 91 ef 9f 93 cb ad 6c 7b 65 f8 53 f1 d8 d9\n 12 5a 33 b8 b5 25 df 7b 37 9f e0 e2 4f b8 67 83 a3 2f cd 5d 41 42 4c 91\n 74 ef 2c ... 78 more bytes>\n*/\n
\nSee the OpenSSL SSL_export_keying_material
documentation for more\ninformation.
Returns an object representing the local certificate. The returned object has\nsome properties corresponding to the fields of the certificate.
\nSee tls.TLSSocket.getPeerCertificate()
for an example of the certificate\nstructure.
If there is no local certificate, an empty object will be returned. If the\nsocket has been destroyed, null
will be returned.
Returns an object containing information on the negotiated cipher suite.
\nFor example, a TLSv1.2 protocol with AES256-SHA cipher:
\n{\n \"name\": \"AES256-SHA\",\n \"standardName\": \"TLS_RSA_WITH_AES_256_CBC_SHA\",\n \"version\": \"SSLv3\"\n}\n
\nSee\nSSL_CIPHER_get_name\nfor more information.
" }, { "textRaw": "`tlsSocket.getEphemeralKeyInfo()`", "type": "method", "name": "getEphemeralKeyInfo", "meta": { "added": [ "v5.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "Returns an object representing the type, name, and size of parameter of\nan ephemeral key exchange in perfect forward secrecy on a client\nconnection. It returns an empty object when the key exchange is not\nephemeral. As this is only supported on a client socket; null
is returned\nif called on a server socket. The supported types are 'DH'
and 'ECDH'
. The\nname
property is available only when type is 'ECDH'
.
For example: { type: 'ECDH', name: 'prime256v1', size: 256 }
.
As the Finished
messages are message digests of the complete handshake\n(with a total of 192 bits for TLS 1.0 and more for SSL 3.0), they can\nbe used for external authentication procedures when the authentication\nprovided by SSL/TLS is not desired or is not enough.
Corresponds to the SSL_get_finished
routine in OpenSSL and may be used\nto implement the tls-unique
channel binding from RFC 5929.
Returns an object representing the peer's certificate. If the peer does not\nprovide a certificate, an empty object will be returned. If the socket has been\ndestroyed, null
will be returned.
If the full certificate chain was requested, each certificate will include an\nissuerCertificate
property containing an object representing its issuer's\ncertificate.
A certificate object has properties corresponding to the fields of the\ncertificate.
\nca
<boolean> true
if a Certificate Authority (CA), false
otherwise.raw
<Buffer> The DER encoded X.509 certificate data.subject
<Object> The certificate subject, described in terms of\nCountry (C
), StateOrProvince (ST
), Locality (L
), Organization (O
),\nOrganizationalUnit (OU
), and CommonName (CN
). The CommonName is typically\na DNS name with TLS certificates. Example:\n{C: 'UK', ST: 'BC', L: 'Metro', O: 'Node Fans', OU: 'Docs', CN: 'example.com'}
.issuer
<Object> The certificate issuer, described in the same terms as the\nsubject
.valid_from
<string> The date-time the certificate is valid from.valid_to
<string> The date-time the certificate is valid to.serialNumber
<string> The certificate serial number, as a hex string.\nExample: 'B9B0D332A1AA5635'
.fingerprint
<string> The SHA-1 digest of the DER encoded certificate. It is\nreturned as a :
separated hexadecimal string. Example: '2A:7A:C2:DD:...'
.fingerprint256
<string> The SHA-256 digest of the DER encoded certificate.\nIt is returned as a :
separated hexadecimal string. Example:\n'2A:7A:C2:DD:...'
.fingerprint512
<string> The SHA-512 digest of the DER encoded certificate.\nIt is returned as a :
separated hexadecimal string. Example:\n'2A:7A:C2:DD:...'
.ext_key_usage
<Array> (Optional) The extended key usage, a set of OIDs.subjectaltname
<string> (Optional) A string containing concatenated names\nfor the subject, an alternative to the subject
names.infoAccess
<Array> (Optional) An array describing the AuthorityInfoAccess,\nused with OCSP.issuerCertificate
<Object> (Optional) The issuer certificate object. For\nself-signed certificates, this may be a circular reference.The certificate may contain information about the public key, depending on\nthe key type.
\nFor RSA keys, the following properties may be defined:
\nbits
<number> The RSA bit size. Example: 1024
.exponent
<string> The RSA exponent, as a string in hexadecimal number\nnotation. Example: '0x010001'
.modulus
<string> The RSA modulus, as a hexadecimal string. Example:\n'B56CE45CB7...'
.pubkey
<Buffer> The public key.For EC keys, the following properties may be defined:
\npubkey
<Buffer> The public key.bits
<number> The key size in bits. Example: 256
.asn1Curve
<string> (Optional) The ASN.1 name of the OID of the elliptic\ncurve. Well-known curves are identified by an OID. While it is unusual, it is\npossible that the curve is identified by its mathematical properties, in which\ncase it will not have an OID. Example: 'prime256v1'
.nistCurve
<string> (Optional) The NIST name for the elliptic curve, if it\nhas one (not all well-known curves have been assigned names by NIST). Example:\n'P-256'
.Example certificate:
\n\n{ subject:\n { OU: [ 'Domain Control Validated', 'PositiveSSL Wildcard' ],\n CN: '*.nodejs.org' },\n issuer:\n { C: 'GB',\n ST: 'Greater Manchester',\n L: 'Salford',\n O: 'COMODO CA Limited',\n CN: 'COMODO RSA Domain Validation Secure Server CA' },\n subjectaltname: 'DNS:*.nodejs.org, DNS:nodejs.org',\n infoAccess:\n { 'CA Issuers - URI':\n [ 'http://crt.comodoca.com/COMODORSADomainValidationSecureServerCA.crt' ],\n 'OCSP - URI': [ 'http://ocsp.comodoca.com' ] },\n modulus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n exponent: '0x10001',\n pubkey: <Buffer ... >,\n valid_from: 'Aug 14 00:00:00 2017 GMT',\n valid_to: 'Nov 20 23:59:59 2019 GMT',\n fingerprint: '01:02:59:D9:C3:D2:0D:08:F7:82:4E:44:A4:B4:53:C5:E2:3A:87:4D',\n fingerprint256: '69:AE:1A:6A:D4:3D:C6:C1:1B:EA:C6:23:DE:BA:2A:14:62:62:93:5C:7A:EA:06:41:9B:0B:BC:87:CE:48:4E:02',\n fingerprint512: '19:2B:3E:C3:B3:5B:32:E8:AE:BB:78:97:27:E4:BA:6C:39:C9:92:79:4F:31:46:39:E2:70:E5:5F:89:42:17:C9:E8:64:CA:FF:BB:72:56:73:6E:28:8A:92:7E:A3:2A:15:8B:C2:E0:45:CA:C3:BC:EA:40:52:EC:CA:A2:68:CB:32',\n ext_key_usage: [ '1.3.6.1.5.5.7.3.1', '1.3.6.1.5.5.7.3.2' ],\n serialNumber: '66593D57F20CBC573E433381B5FEC280',\n raw: <Buffer ... > }\n
",
"type": "module",
"displayName": "Certificate object"
}
]
},
{
"textRaw": "`tlsSocket.getPeerFinished()`",
"type": "method",
"name": "getPeerFinished",
"meta": {
"added": [
"v9.9.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer|undefined} The latest `Finished` message that is expected or has actually been received from the socket as part of a SSL/TLS handshake, or `undefined` if there is no `Finished` message so far.",
"name": "return",
"type": "Buffer|undefined",
"desc": "The latest `Finished` message that is expected or has actually been received from the socket as part of a SSL/TLS handshake, or `undefined` if there is no `Finished` message so far."
},
"params": []
}
],
"desc": "As the Finished
messages are message digests of the complete handshake\n(with a total of 192 bits for TLS 1.0 and more for SSL 3.0), they can\nbe used for external authentication procedures when the authentication\nprovided by SSL/TLS is not desired or is not enough.
Corresponds to the SSL_get_peer_finished
routine in OpenSSL and may be used\nto implement the tls-unique
channel binding from RFC 5929.
Returns the peer certificate as an <X509Certificate> object.
\nIf there is no peer certificate, or the socket has been destroyed,\nundefined
will be returned.
Returns a string containing the negotiated SSL/TLS protocol version of the\ncurrent connection. The value 'unknown'
will be returned for connected\nsockets that have not completed the handshaking process. The value null
will\nbe returned for server sockets or disconnected client sockets.
Protocol versions are:
\n'SSLv3'
'TLSv1'
'TLSv1.1'
'TLSv1.2'
'TLSv1.3'
See the OpenSSL SSL_get_version
documentation for more information.
Returns the TLS session data or undefined
if no session was\nnegotiated. On the client, the data can be provided to the session
option of\ntls.connect()
to resume the connection. On the server, it may be useful\nfor debugging.
See Session Resumption for more information.
\nNote: getSession()
works only for TLSv1.2 and below. For TLSv1.3, applications\nmust use the 'session'
event (it also works for TLSv1.2 and below).
See\nSSL_get_shared_sigalgs\nfor more information.
" }, { "textRaw": "`tlsSocket.getTLSTicket()`", "type": "method", "name": "getTLSTicket", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "{Buffer}", "type": "Buffer" } ] } ], "desc": "For a client, returns the TLS session ticket if one is available, or\nundefined
. For a server, always returns undefined
.
It may be useful for debugging.
\nSee Session Resumption for more information.
" }, { "textRaw": "`tlsSocket.getX509Certificate()`", "type": "method", "name": "getX509Certificate", "meta": { "added": [ "v15.9.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {X509Certificate}", "name": "return", "type": "X509Certificate" }, "params": [] } ], "desc": "Returns the local certificate as an <X509Certificate> object.
\nIf there is no local certificate, or the socket has been destroyed,\nundefined
will be returned.
See Session Resumption for more information.
" }, { "textRaw": "`tlsSocket.renegotiate(options, callback)`", "type": "method", "name": "renegotiate", "meta": { "added": [ "v0.11.8" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/41678", "description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean} `true` if renegotiation was initiated, `false` otherwise.", "name": "return", "type": "boolean", "desc": "`true` if renegotiation was initiated, `false` otherwise." }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`rejectUnauthorized` {boolean} If not `false`, the server certificate is verified against the list of supplied CAs. An `'error'` event is emitted if verification fails; `err.code` contains the OpenSSL error code. **Default:** `true`.", "name": "rejectUnauthorized", "type": "boolean", "default": "`true`", "desc": "If not `false`, the server certificate is verified against the list of supplied CAs. An `'error'` event is emitted if verification fails; `err.code` contains the OpenSSL error code." }, { "textRaw": "`requestCert`", "name": "requestCert" } ] }, { "textRaw": "`callback` {Function} If `renegotiate()` returned `true`, callback is attached once to the `'secure'` event. If `renegotiate()` returned `false`, `callback` will be called in the next tick with an error, unless the `tlsSocket` has been destroyed, in which case `callback` will not be called at all.", "name": "callback", "type": "Function", "desc": "If `renegotiate()` returned `true`, callback is attached once to the `'secure'` event. If `renegotiate()` returned `false`, `callback` will be called in the next tick with an error, unless the `tlsSocket` has been destroyed, in which case `callback` will not be called at all." } ] } ], "desc": "The tlsSocket.renegotiate()
method initiates a TLS renegotiation process.\nUpon completion, the callback
function will be passed a single argument\nthat is either an Error
(if the request failed) or null
.
This method can be used to request a peer's certificate after the secure\nconnection has been established.
\nWhen running as the server, the socket will be destroyed with an error after\nhandshakeTimeout
timeout.
For TLSv1.3, renegotiation cannot be initiated, it is not supported by the\nprotocol.
" }, { "textRaw": "`tlsSocket.setMaxSendFragment(size)`", "type": "method", "name": "setMaxSendFragment", "meta": { "added": [ "v0.11.11" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`size` {number} The maximum TLS fragment size. The maximum value is `16384`. **Default:** `16384`.", "name": "size", "type": "number", "default": "`16384`", "desc": "The maximum TLS fragment size. The maximum value is `16384`." } ] } ], "desc": "The tlsSocket.setMaxSendFragment()
method sets the maximum TLS fragment size.\nReturns true
if setting the limit succeeded; false
otherwise.
Smaller fragment sizes decrease the buffering latency on the client: larger\nfragments are buffered by the TLS layer until the entire fragment is received\nand its integrity is verified; large fragments can span multiple roundtrips\nand their processing can be delayed due to packet loss or reordering. However,\nsmaller fragments add extra TLS framing bytes and CPU overhead, which may\ndecrease overall server throughput.
" } ], "properties": [ { "textRaw": "`tlsSocket.authorizationError`", "name": "authorizationError", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Returns the reason why the peer's certificate was not been verified. This\nproperty is set only when tlsSocket.authorized === false
.
This property is true
if the peer certificate was signed by one of the CAs\nspecified when creating the tls.TLSSocket
instance, otherwise false
.
Always returns true
. This may be used to distinguish TLS sockets from regular\nnet.Socket
instances.
Returns the string representation of the local IP address.
" }, { "textRaw": "`localPort` {integer}", "type": "integer", "name": "localPort", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Returns the numeric representation of the local port.
" }, { "textRaw": "`remoteAddress` {string}", "type": "string", "name": "remoteAddress", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Returns the string representation of the remote IP address. For example,\n'74.125.127.100'
or '2001:4860:a005::68'
.
Returns the string representation of the remote IP family. 'IPv4'
or 'IPv6'
.
Returns the numeric representation of the remote port. For example, 443
.
Construct a new tls.TLSSocket
object from an existing TCP socket.
Verifies the certificate cert
is issued to hostname
.
Returns <Error> object, populating it with reason
, host
, and cert
on\nfailure. On success, returns <undefined>.
This function is intended to be used in combination with the\ncheckServerIdentity
option that can be passed to tls.connect()
and as\nsuch operates on a certificate object. For other purposes, consider using\nx509.checkHost()
instead.
This function can be overwritten by providing an alternative function as the\noptions.checkServerIdentity
option that is passed to tls.connect()
. The\noverwriting function can call tls.checkServerIdentity()
of course, to augment\nthe checks done with additional verification.
This function is only called if the certificate passed all other checks, such as\nbeing issued by trusted CA (options.ca
).
Earlier versions of Node.js incorrectly accepted certificates for a given\nhostname
if a matching uniformResourceIdentifier
subject alternative name\nwas present (see CVE-2021-44531). Applications that wish to accept\nuniformResourceIdentifier
subject alternative names can use a custom\noptions.checkServerIdentity
function that implements the desired behavior.
The callback
function, if specified, will be added as a listener for the\n'secureConnect'
event.
tls.connect()
returns a tls.TLSSocket
object.
Unlike the https
API, tls.connect()
does not enable the\nSNI (Server Name Indication) extension by default, which may cause some\nservers to return an incorrect certificate or reject the connection\naltogether. To enable SNI, set the servername
option in addition\nto host
.
The following illustrates a client for the echo server example from\ntls.createServer()
:
// Assumes an echo server that is listening on port 8000.\nconst tls = require('node:tls');\nconst fs = require('node:fs');\n\nconst options = {\n // Necessary only if the server requires client certificate authentication.\n key: fs.readFileSync('client-key.pem'),\n cert: fs.readFileSync('client-cert.pem'),\n\n // Necessary only if the server uses a self-signed certificate.\n ca: [ fs.readFileSync('server-cert.pem') ],\n\n // Necessary only if the server's cert isn't for \"localhost\".\n checkServerIdentity: () => { return null; },\n};\n\nconst socket = tls.connect(8000, options, () => {\n console.log('client connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n process.stdin.pipe(socket);\n process.stdin.resume();\n});\nsocket.setEncoding('utf8');\nsocket.on('data', (data) => {\n console.log(data);\n});\nsocket.on('end', () => {\n console.log('server ends connection');\n});\n
"
},
{
"textRaw": "`tls.connect(path[, options][, callback])`",
"type": "method",
"name": "connect",
"meta": {
"added": [
"v0.11.3"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {tls.TLSSocket}",
"name": "return",
"type": "tls.TLSSocket"
},
"params": [
{
"textRaw": "`path` {string} Default value for `options.path`.",
"name": "path",
"type": "string",
"desc": "Default value for `options.path`."
},
{
"textRaw": "`options` {Object} See [`tls.connect()`][].",
"name": "options",
"type": "Object",
"desc": "See [`tls.connect()`][]."
},
{
"textRaw": "`callback` {Function} See [`tls.connect()`][].",
"name": "callback",
"type": "Function",
"desc": "See [`tls.connect()`][]."
}
]
}
],
"desc": "Same as tls.connect()
except that path
can be provided\nas an argument instead of an option.
A path option, if specified, will take precedence over the path argument.
" }, { "textRaw": "`tls.connect(port[, host][, options][, callback])`", "type": "method", "name": "connect", "meta": { "added": [ "v0.11.3" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {tls.TLSSocket}", "name": "return", "type": "tls.TLSSocket" }, "params": [ { "textRaw": "`port` {number} Default value for `options.port`.", "name": "port", "type": "number", "desc": "Default value for `options.port`." }, { "textRaw": "`host` {string} Default value for `options.host`.", "name": "host", "type": "string", "desc": "Default value for `options.host`." }, { "textRaw": "`options` {Object} See [`tls.connect()`][].", "name": "options", "type": "Object", "desc": "See [`tls.connect()`][]." }, { "textRaw": "`callback` {Function} See [`tls.connect()`][].", "name": "callback", "type": "Function", "desc": "See [`tls.connect()`][]." } ] } ], "desc": "Same as tls.connect()
except that port
and host
can be provided\nas arguments instead of options.
A port or host option, if specified, will take precedence over any port or host\nargument.
" }, { "textRaw": "`tls.createSecureContext([options])`", "type": "method", "name": "createSecureContext", "meta": { "added": [ "v0.11.13" ], "changes": [ { "version": [ "v19.8.0", "v18.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/46978", "description": "The `dhparam` option can now be set to `'auto'` to enable DHE with appropriate well-known parameters." }, { "version": "v12.12.0", "pr-url": "https://github.com/nodejs/node/pull/28973", "description": "Added `privateKeyIdentifier` and `privateKeyEngine` options to get private key from an OpenSSL engine." }, { "version": "v12.11.0", "pr-url": "https://github.com/nodejs/node/pull/29598", "description": "Added `sigalgs` option to override supported signature algorithms." }, { "version": "v12.0.0", "pr-url": "https://github.com/nodejs/node/pull/26209", "description": "TLSv1.3 support added." }, { "version": "v11.5.0", "pr-url": "https://github.com/nodejs/node/pull/24733", "description": "The `ca:` option now supports `BEGIN TRUSTED CERTIFICATE`." }, { "version": [ "v11.4.0", "v10.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/24405", "description": "The `minVersion` and `maxVersion` can be used to restrict the allowed TLS protocol versions." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/19794", "description": "The `ecdhCurve` cannot be set to `false` anymore due to a change in OpenSSL." }, { "version": "v9.3.0", "pr-url": "https://github.com/nodejs/node/pull/14903", "description": "The `options` parameter can now include `clientCertEngine`." }, { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/15206", "description": "The `ecdhCurve` option can now be multiple `':'` separated curve names or `'auto'`." }, { "version": "v7.3.0", "pr-url": "https://github.com/nodejs/node/pull/10294", "description": "If the `key` option is an array, individual entries do not need a `passphrase` property anymore. `Array` entries can also just be `string`s or `Buffer`s now." }, { "version": "v5.2.0", "pr-url": "https://github.com/nodejs/node/pull/4099", "description": "The `ca` option can now be a single string containing multiple CA certificates." } ] }, "signatures": [ { "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`ca` {string|string\\[]|Buffer|Buffer\\[]} Optionally override the trusted CA certificates. Default is to trust the well-known CAs curated by Mozilla. Mozilla's CAs are completely replaced when CAs are explicitly specified using this option. The value can be a string or `Buffer`, or an `Array` of strings and/or `Buffer`s. Any string or `Buffer` can contain multiple PEM CAs concatenated together. The peer's certificate must be chainable to a CA trusted by the server for the connection to be authenticated. When using certificates that are not chainable to a well-known CA, the certificate's CA must be explicitly specified as a trusted or the connection will fail to authenticate. If the peer uses a certificate that doesn't match or chain to one of the default CAs, use the `ca` option to provide a CA certificate that the peer's certificate can match or chain to. For self-signed certificates, the certificate is its own CA, and must be provided. For PEM encoded certificates, supported types are \"TRUSTED CERTIFICATE\", \"X509 CERTIFICATE\", and \"CERTIFICATE\". See also [`tls.rootCertificates`][].", "name": "ca", "type": "string|string\\[]|Buffer|Buffer\\[]", "desc": "Optionally override the trusted CA certificates. Default is to trust the well-known CAs curated by Mozilla. Mozilla's CAs are completely replaced when CAs are explicitly specified using this option. The value can be a string or `Buffer`, or an `Array` of strings and/or `Buffer`s. Any string or `Buffer` can contain multiple PEM CAs concatenated together. The peer's certificate must be chainable to a CA trusted by the server for the connection to be authenticated. When using certificates that are not chainable to a well-known CA, the certificate's CA must be explicitly specified as a trusted or the connection will fail to authenticate. If the peer uses a certificate that doesn't match or chain to one of the default CAs, use the `ca` option to provide a CA certificate that the peer's certificate can match or chain to. For self-signed certificates, the certificate is its own CA, and must be provided. For PEM encoded certificates, supported types are \"TRUSTED CERTIFICATE\", \"X509 CERTIFICATE\", and \"CERTIFICATE\". See also [`tls.rootCertificates`][]." }, { "textRaw": "`cert` {string|string\\[]|Buffer|Buffer\\[]} Cert chains in PEM format. One cert chain should be provided per private key. Each cert chain should consist of the PEM formatted certificate for a provided private `key`, followed by the PEM formatted intermediate certificates (if any), in order, and not including the root CA (the root CA must be pre-known to the peer, see `ca`). When providing multiple cert chains, they do not have to be in the same order as their private keys in `key`. If the intermediate certificates are not provided, the peer will not be able to validate the certificate, and the handshake will fail.", "name": "cert", "type": "string|string\\[]|Buffer|Buffer\\[]", "desc": "Cert chains in PEM format. One cert chain should be provided per private key. Each cert chain should consist of the PEM formatted certificate for a provided private `key`, followed by the PEM formatted intermediate certificates (if any), in order, and not including the root CA (the root CA must be pre-known to the peer, see `ca`). When providing multiple cert chains, they do not have to be in the same order as their private keys in `key`. If the intermediate certificates are not provided, the peer will not be able to validate the certificate, and the handshake will fail." }, { "textRaw": "`sigalgs` {string} Colon-separated list of supported signature algorithms. The list can contain digest algorithms (`SHA256`, `MD5` etc.), public key algorithms (`RSA-PSS`, `ECDSA` etc.), combination of both (e.g 'RSA+SHA384') or TLS v1.3 scheme names (e.g. `rsa_pss_pss_sha512`). See [OpenSSL man pages](https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set1_sigalgs_list.html) for more info.", "name": "sigalgs", "type": "string", "desc": "Colon-separated list of supported signature algorithms. The list can contain digest algorithms (`SHA256`, `MD5` etc.), public key algorithms (`RSA-PSS`, `ECDSA` etc.), combination of both (e.g 'RSA+SHA384') or TLS v1.3 scheme names (e.g. `rsa_pss_pss_sha512`). See [OpenSSL man pages](https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set1_sigalgs_list.html) for more info." }, { "textRaw": "`ciphers` {string} Cipher suite specification, replacing the default. For more information, see [Modifying the default TLS cipher suite][]. Permitted ciphers can be obtained via [`tls.getCiphers()`][]. Cipher names must be uppercased in order for OpenSSL to accept them.", "name": "ciphers", "type": "string", "desc": "Cipher suite specification, replacing the default. For more information, see [Modifying the default TLS cipher suite][]. Permitted ciphers can be obtained via [`tls.getCiphers()`][]. Cipher names must be uppercased in order for OpenSSL to accept them." }, { "textRaw": "`clientCertEngine` {string} Name of an OpenSSL engine which can provide the client certificate.", "name": "clientCertEngine", "type": "string", "desc": "Name of an OpenSSL engine which can provide the client certificate." }, { "textRaw": "`crl` {string|string\\[]|Buffer|Buffer\\[]} PEM formatted CRLs (Certificate Revocation Lists).", "name": "crl", "type": "string|string\\[]|Buffer|Buffer\\[]", "desc": "PEM formatted CRLs (Certificate Revocation Lists)." }, { "textRaw": "`dhparam` {string|Buffer} `'auto'` or custom Diffie-Hellman parameters, required for non-ECDHE [perfect forward secrecy][]. If omitted or invalid, the parameters are silently discarded and DHE ciphers will not be available. [ECDHE][]-based [perfect forward secrecy][] will still be available.", "name": "dhparam", "type": "string|Buffer", "desc": "`'auto'` or custom Diffie-Hellman parameters, required for non-ECDHE [perfect forward secrecy][]. If omitted or invalid, the parameters are silently discarded and DHE ciphers will not be available. [ECDHE][]-based [perfect forward secrecy][] will still be available." }, { "textRaw": "`ecdhCurve` {string} A string describing a named curve or a colon separated list of curve NIDs or names, for example `P-521:P-384:P-256`, to use for ECDH key agreement. Set to `auto` to select the curve automatically. Use [`crypto.getCurves()`][] to obtain a list of available curve names. On recent releases, `openssl ecparam -list_curves` will also display the name and description of each available elliptic curve. **Default:** [`tls.DEFAULT_ECDH_CURVE`][].", "name": "ecdhCurve", "type": "string", "default": "[`tls.DEFAULT_ECDH_CURVE`][]", "desc": "A string describing a named curve or a colon separated list of curve NIDs or names, for example `P-521:P-384:P-256`, to use for ECDH key agreement. Set to `auto` to select the curve automatically. Use [`crypto.getCurves()`][] to obtain a list of available curve names. On recent releases, `openssl ecparam -list_curves` will also display the name and description of each available elliptic curve." }, { "textRaw": "`honorCipherOrder` {boolean} Attempt to use the server's cipher suite preferences instead of the client's. When `true`, causes `SSL_OP_CIPHER_SERVER_PREFERENCE` to be set in `secureOptions`, see [OpenSSL Options][] for more information.", "name": "honorCipherOrder", "type": "boolean", "desc": "Attempt to use the server's cipher suite preferences instead of the client's. When `true`, causes `SSL_OP_CIPHER_SERVER_PREFERENCE` to be set in `secureOptions`, see [OpenSSL Options][] for more information." }, { "textRaw": "`key` {string|string\\[]|Buffer|Buffer\\[]|Object\\[]} Private keys in PEM format. PEM allows the option of private keys being encrypted. Encrypted keys will be decrypted with `options.passphrase`. Multiple keys using different algorithms can be provided either as an array of unencrypted key strings or buffers, or an array of objects in the form `{pem:tls.createServer()
sets the default value of the honorCipherOrder
option\nto true
, other APIs that create secure contexts leave it unset.
tls.createServer()
uses a 128 bit truncated SHA1 hash value generated\nfrom process.argv
as the default value of the sessionIdContext
option, other\nAPIs that create secure contexts have no default value.
The tls.createSecureContext()
method creates a SecureContext
object. It is\nusable as an argument to several tls
APIs, such as server.addContext()
,\nbut has no public methods. The tls.Server
constructor and the\ntls.createServer()
method do not support the secureContext
option.
A key is required for ciphers that use certificates. Either key
or\npfx
can be used to provide it.
If the ca
option is not given, then Node.js will default to using\nMozilla's publicly trusted list of CAs.
Custom DHE parameters are discouraged in favor of the new dhparam: 'auto'
\noption. When set to 'auto'
, well-known DHE parameters of sufficient strength\nwill be selected automatically. Otherwise, if necessary, openssl dhparam
can\nbe used to create custom parameters. The key length must be greater than or\nequal to 1024 bits or else an error will be thrown. Although 1024 bits is\npermissible, use 2048 bits or larger for stronger security.
Creates a new secure pair object with two streams, one of which reads and writes\nthe encrypted data and the other of which reads and writes the cleartext data.\nGenerally, the encrypted stream is piped to/from an incoming encrypted data\nstream and the cleartext one is used as a replacement for the initial encrypted\nstream.
\ntls.createSecurePair()
returns a tls.SecurePair
object with cleartext
and\nencrypted
stream properties.
Using cleartext
has the same API as tls.TLSSocket
.
The tls.createSecurePair()
method is now deprecated in favor of\ntls.TLSSocket()
. For example, the code:
pair = tls.createSecurePair(/* ... */);\npair.encrypted.pipe(socket);\nsocket.pipe(pair.encrypted);\n
\ncan be replaced by:
\nsecureSocket = tls.TLSSocket(socket, options);\n
\nwhere secureSocket
has the same API as pair.cleartext
.
Creates a new tls.Server
. The secureConnectionListener
, if provided, is\nautomatically set as a listener for the 'secureConnection'
event.
The ticketKeys
options is automatically shared between node:cluster
module\nworkers.
The following illustrates a simple echo server:
\nconst tls = require('node:tls');\nconst fs = require('node:fs');\n\nconst options = {\n key: fs.readFileSync('server-key.pem'),\n cert: fs.readFileSync('server-cert.pem'),\n\n // This is necessary only if using client certificate authentication.\n requestCert: true,\n\n // This is necessary only if the client uses a self-signed certificate.\n ca: [ fs.readFileSync('client-cert.pem') ],\n};\n\nconst server = tls.createServer(options, (socket) => {\n console.log('server connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n socket.write('welcome!\\n');\n socket.setEncoding('utf8');\n socket.pipe(socket);\n});\nserver.listen(8000, () => {\n console.log('server bound');\n});\n
\nThe server can be tested by connecting to it using the example client from\ntls.connect()
.
Returns an array with the names of the supported TLS ciphers. The names are\nlower-case for historical reasons, but must be uppercased to be used in\nthe ciphers
option of tls.createSecureContext()
.
Not all supported ciphers are enabled by default. See\nModifying the default TLS cipher suite.
\nCipher names that start with 'tls_'
are for TLSv1.3, all the others are for\nTLSv1.2 and below.
console.log(tls.getCiphers()); // ['aes128-gcm-sha256', 'aes128-sha', ...]\n
"
}
],
"properties": [
{
"textRaw": "`rootCertificates` {string\\[]}",
"type": "string\\[]",
"name": "rootCertificates",
"meta": {
"added": [
"v12.3.0"
],
"changes": []
},
"desc": "An immutable array of strings representing the root certificates (in PEM format)\nfrom the bundled Mozilla CA store as supplied by the current Node.js version.
\nThe bundled CA store, as supplied by Node.js, is a snapshot of Mozilla CA store\nthat is fixed at release time. It is identical on all supported platforms.
" }, { "textRaw": "`tls.DEFAULT_ECDH_CURVE`", "name": "DEFAULT_ECDH_CURVE", "meta": { "added": [ "v0.11.13" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/16853", "description": "Default value changed to `'auto'`." } ] }, "desc": "The default curve name to use for ECDH key agreement in a tls server. The\ndefault value is 'auto'
. See tls.createSecureContext()
for further\ninformation.
Source Code: lib/trace_events.js
\nThe node:trace_events
module provides a mechanism to centralize tracing\ninformation generated by V8, Node.js core, and userspace code.
Tracing can be enabled with the --trace-event-categories
command-line flag\nor by using the node:trace_events
module. The --trace-event-categories
flag\naccepts a list of comma-separated category names.
The available categories are:
\nnode
: An empty placeholder.node.async_hooks
: Enables capture of detailed async_hooks
trace data.\nThe async_hooks
events have a unique asyncId
and a special triggerId
\ntriggerAsyncId
property.node.bootstrap
: Enables capture of Node.js bootstrap milestones.node.console
: Enables capture of console.time()
and console.count()
\noutput.node.threadpoolwork.sync
: Enables capture of trace data for threadpool\nsynchronous operations, such as blob
, zlib
, crypto
and node_api
.node.threadpoolwork.async
: Enables capture of trace data for threadpool\nasynchronous operations, such as blob
, zlib
, crypto
and node_api
.node.dns.native
: Enables capture of trace data for DNS queries.node.net.native
: Enables capture of trace data for network.node.environment
: Enables capture of Node.js Environment milestones.node.fs.sync
: Enables capture of trace data for file system sync methods.node.fs_dir.sync
: Enables capture of trace data for file system sync\ndirectory methods.node.fs.async
: Enables capture of trace data for file system async methods.node.fs_dir.async
: Enables capture of trace data for file system async\ndirectory methods.node.perf
: Enables capture of Performance API measurements.\nnode.perf.usertiming
: Enables capture of only Performance API User Timing\nmeasures and marks.node.perf.timerify
: Enables capture of only Performance API timerify\nmeasurements.node.promises.rejections
: Enables capture of trace data tracking the number\nof unhandled Promise rejections and handled-after-rejections.node.vm.script
: Enables capture of trace data for the node:vm
module's\nrunInNewContext()
, runInContext()
, and runInThisContext()
methods.v8
: The V8 events are GC, compiling, and execution related.node.http
: Enables capture of trace data for http request / response.By default the node
, node.async_hooks
, and v8
categories are enabled.
node --trace-event-categories v8,node,node.async_hooks server.js\n
\nPrior versions of Node.js required the use of the --trace-events-enabled
\nflag to enable trace events. This requirement has been removed. However, the\n--trace-events-enabled
flag may still be used and will enable the\nnode
, node.async_hooks
, and v8
trace event categories by default.
node --trace-events-enabled\n\n# is equivalent to\n\nnode --trace-event-categories v8,node,node.async_hooks\n
\nAlternatively, trace events may be enabled using the node:trace_events
module:
const trace_events = require('node:trace_events');\nconst tracing = trace_events.createTracing({ categories: ['node.perf'] });\ntracing.enable(); // Enable trace event capture for the 'node.perf' category\n\n// do work\n\ntracing.disable(); // Disable trace event capture for the 'node.perf' category\n
\nRunning Node.js with tracing enabled will produce log files that can be opened\nin the chrome://tracing
\ntab of Chrome.
The logging file is by default called node_trace.${rotation}.log
, where\n${rotation}
is an incrementing log-rotation id. The filepath pattern can\nbe specified with --trace-event-file-pattern
that accepts a template\nstring that supports ${rotation}
and ${pid}
:
node --trace-event-categories v8 --trace-event-file-pattern '${pid}-${rotation}.log' server.js\n
\nTo guarantee that the log file is properly generated after signal events like\nSIGINT
, SIGTERM
, or SIGBREAK
, make sure to have the appropriate handlers\nin your code, such as:
process.on('SIGINT', function onSigint() {\n console.info('Received SIGINT.');\n process.exit(130); // Or applicable exit code depending on OS and signal\n});\n
\nThe tracing system uses the same time source\nas the one used by process.hrtime()
.\nHowever the trace-event timestamps are expressed in microseconds,\nunlike process.hrtime()
which returns nanoseconds.
The features from this module are not available in Worker
threads.
The Tracing
object is used to enable or disable tracing for sets of\ncategories. Instances are created using the trace_events.createTracing()
\nmethod.
When created, the Tracing
object is disabled. Calling the\ntracing.enable()
method adds the categories to the set of enabled trace event\ncategories. Calling tracing.disable()
will remove the categories from the\nset of enabled trace event categories.
A comma-separated list of the trace event categories covered by this\nTracing
object.
Disables this Tracing
object.
Only trace event categories not covered by other enabled Tracing
objects\nand not specified by the --trace-event-categories
flag will be disabled.
const trace_events = require('node:trace_events');\nconst t1 = trace_events.createTracing({ categories: ['node', 'v8'] });\nconst t2 = trace_events.createTracing({ categories: ['node.perf', 'node'] });\nt1.enable();\nt2.enable();\n\n// Prints 'node,node.perf,v8'\nconsole.log(trace_events.getEnabledCategories());\n\nt2.disable(); // Will only disable emission of the 'node.perf' category\n\n// Prints 'node,v8'\nconsole.log(trace_events.getEnabledCategories());\n
"
},
{
"textRaw": "`tracing.enable()`",
"type": "method",
"name": "enable",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Enables this Tracing
object for the set of categories covered by the\nTracing
object.
'use strict';\n\nconst { Session } = require('inspector');\nconst session = new Session();\nsession.connect();\n\nfunction post(message, data) {\n return new Promise((resolve, reject) => {\n session.post(message, data, (err, result) => {\n if (err)\n reject(new Error(JSON.stringify(err)));\n else\n resolve(result);\n });\n });\n}\n\nasync function collect() {\n const data = [];\n session.on('NodeTracing.dataCollected', (chunk) => data.push(chunk));\n session.on('NodeTracing.tracingComplete', () => {\n // done\n });\n const traceConfig = { includedCategories: ['v8'] };\n await post('NodeTracing.start', { traceConfig });\n // do something\n setTimeout(() => {\n post('NodeTracing.stop').then(() => {\n session.disconnect();\n console.log(data);\n });\n }, 1000);\n}\n\ncollect();\n
",
"type": "module",
"displayName": "Collect trace events data by inspector"
}
],
"methods": [
{
"textRaw": "`trace_events.createTracing(options)`",
"type": "method",
"name": "createTracing",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Tracing}.",
"name": "return",
"type": "Tracing",
"desc": "."
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`categories` {string\\[]} An array of trace category names. Values included in the array are coerced to a string when possible. An error will be thrown if the value cannot be coerced.",
"name": "categories",
"type": "string\\[]",
"desc": "An array of trace category names. Values included in the array are coerced to a string when possible. An error will be thrown if the value cannot be coerced."
}
]
}
]
}
],
"desc": "Creates and returns a Tracing
object for the given set of categories
.
const trace_events = require('node:trace_events');\nconst categories = ['node.perf', 'node.async_hooks'];\nconst tracing = trace_events.createTracing({ categories });\ntracing.enable();\n// do stuff\ntracing.disable();\n
"
},
{
"textRaw": "`trace_events.getEnabledCategories()`",
"type": "method",
"name": "getEnabledCategories",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": []
}
],
"desc": "Returns a comma-separated list of all currently-enabled trace event\ncategories. The current set of enabled trace event categories is determined\nby the union of all currently-enabled Tracing
objects and any categories\nenabled using the --trace-event-categories
flag.
Given the file test.js
below, the command\nnode --trace-event-categories node.perf test.js
will print\n'node.async_hooks,node.perf'
to the console.
const trace_events = require('node:trace_events');\nconst t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });\nconst t2 = trace_events.createTracing({ categories: ['node.perf'] });\nconst t3 = trace_events.createTracing({ categories: ['v8'] });\n\nt1.enable();\nt2.enable();\n\nconsole.log(trace_events.getEnabledCategories());\n
\nSource Code: lib/tty.js
\nThe node:tty
module provides the tty.ReadStream
and tty.WriteStream
\nclasses. In most cases, it will not be necessary or possible to use this module\ndirectly. However, it can be accessed using:
const tty = require('node:tty');\n
\nWhen Node.js detects that it is being run with a text terminal (\"TTY\")\nattached, process.stdin
will, by default, be initialized as an instance of\ntty.ReadStream
and both process.stdout
and process.stderr
will, by\ndefault, be instances of tty.WriteStream
. The preferred method of determining\nwhether Node.js is being run within a TTY context is to check that the value of\nthe process.stdout.isTTY
property is true
:
$ node -p -e \"Boolean(process.stdout.isTTY)\"\ntrue\n$ node -p -e \"Boolean(process.stdout.isTTY)\" | cat\nfalse\n
\nIn most cases, there should be little to no reason for an application to\nmanually create instances of the tty.ReadStream
and tty.WriteStream
\nclasses.
Represents the readable side of a TTY. In normal circumstances\nprocess.stdin
will be the only tty.ReadStream
instance in a Node.js\nprocess and there should be no reason to create additional instances.
A boolean
that is true
if the TTY is currently configured to operate as a\nraw device.
This flag is always false
when a process starts, even if the terminal is\noperating in raw mode. Its value will change with subsequent calls to\nsetRawMode
.
A boolean
that is always true
for tty.ReadStream
instances.
Allows configuration of tty.ReadStream
so that it operates as a raw device.
When in raw mode, input is always available character-by-character, not\nincluding modifiers. Additionally, all special processing of characters by the\nterminal is disabled, including echoing input\ncharacters. Ctrl+C will no longer cause a SIGINT
when\nin this mode.
Represents the writable side of a TTY. In normal circumstances,\nprocess.stdout
and process.stderr
will be the only\ntty.WriteStream
instances created for a Node.js process and there\nshould be no reason to create additional instances.
The 'resize'
event is emitted whenever either of the writeStream.columns
\nor writeStream.rows
properties have changed. No arguments are passed to the\nlistener callback when called.
process.stdout.on('resize', () => {\n console.log('screen size has changed!');\n console.log(`${process.stdout.columns}x${process.stdout.rows}`);\n});\n
"
}
],
"methods": [
{
"textRaw": "`writeStream.clearLine(dir[, callback])`",
"type": "method",
"name": "clearLine",
"meta": {
"added": [
"v0.7.7"
],
"changes": [
{
"version": "v12.7.0",
"pr-url": "https://github.com/nodejs/node/pull/28721",
"description": "The stream's write() callback and return value are exposed."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `false` if the stream wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`.",
"name": "return",
"type": "boolean",
"desc": "`false` if the stream wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`."
},
"params": [
{
"textRaw": "`dir` {number}",
"name": "dir",
"type": "number",
"options": [
{
"textRaw": "`-1`: to the left from cursor",
"name": "-1",
"desc": "to the left from cursor"
},
{
"textRaw": "`1`: to the right from cursor",
"name": "1",
"desc": "to the right from cursor"
},
{
"textRaw": "`0`: the entire line",
"name": "0",
"desc": "the entire line"
}
]
},
{
"textRaw": "`callback` {Function} Invoked once the operation completes.",
"name": "callback",
"type": "Function",
"desc": "Invoked once the operation completes."
}
]
}
],
"desc": "writeStream.clearLine()
clears the current line of this WriteStream
in a\ndirection identified by dir
.
writeStream.clearScreenDown()
clears this WriteStream
from the current\ncursor down.
writeStream.cursorTo()
moves this WriteStream
's cursor to the specified\nposition.
Returns:
\n1
for 2,4
for 16,8
for 256,24
for 16,777,216 colors supported.Use this to determine what colors the terminal supports. Due to the nature of\ncolors in terminals it is possible to either have false positives or false\nnegatives. It depends on process information and the environment variables that\nmay lie about what terminal is used.\nIt is possible to pass in an env
object to simulate the usage of a specific\nterminal. This can be useful to check how specific environment settings behave.
To enforce a specific color support, use one of the below environment settings.
\nFORCE_COLOR = 0
(Disables colors)FORCE_COLOR = 1
FORCE_COLOR = 2
FORCE_COLOR = 3
Disabling color support is also possible by using the NO_COLOR
and\nNODE_DISABLE_COLORS
environment variables.
writeStream.getWindowSize()
returns the size of the TTY\ncorresponding to this WriteStream
. The array is of the type\n[numColumns, numRows]
where numColumns
and numRows
represent the number\nof columns and rows in the corresponding TTY.
Returns true
if the writeStream
supports at least as many colors as provided\nin count
. Minimum support is 2 (black and white).
This has the same false positives and negatives as described in\nwriteStream.getColorDepth()
.
process.stdout.hasColors();\n// Returns true or false depending on if `stdout` supports at least 16 colors.\nprocess.stdout.hasColors(256);\n// Returns true or false depending on if `stdout` supports at least 256 colors.\nprocess.stdout.hasColors({ TMUX: '1' });\n// Returns true.\nprocess.stdout.hasColors(2 ** 24, { TMUX: '1' });\n// Returns false (the environment setting pretends to support 2 ** 8 colors).\n
"
},
{
"textRaw": "`writeStream.moveCursor(dx, dy[, callback])`",
"type": "method",
"name": "moveCursor",
"meta": {
"added": [
"v0.7.7"
],
"changes": [
{
"version": "v12.7.0",
"pr-url": "https://github.com/nodejs/node/pull/28721",
"description": "The stream's write() callback and return value are exposed."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean} `false` if the stream wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`.",
"name": "return",
"type": "boolean",
"desc": "`false` if the stream wishes for the calling code to wait for the `'drain'` event to be emitted before continuing to write additional data; otherwise `true`."
},
"params": [
{
"textRaw": "`dx` {number}",
"name": "dx",
"type": "number"
},
{
"textRaw": "`dy` {number}",
"name": "dy",
"type": "number"
},
{
"textRaw": "`callback` {Function} Invoked once the operation completes.",
"name": "callback",
"type": "Function",
"desc": "Invoked once the operation completes."
}
]
}
],
"desc": "writeStream.moveCursor()
moves this WriteStream
's cursor relative to its\ncurrent position.
A number
specifying the number of columns the TTY currently has. This property\nis updated whenever the 'resize'
event is emitted.
A boolean
that is always true
.
A number
specifying the number of rows the TTY currently has. This property\nis updated whenever the 'resize'
event is emitted.
The tty.isatty()
method returns true
if the given fd
is associated with\na TTY and false
if it is not, including whenever fd
is not a non-negative\ninteger.
Source Code: lib/dgram.js
\nThe node:dgram
module provides an implementation of UDP datagram sockets.
import dgram from 'node:dgram';\n\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.error(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n const address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// Prints: server listening 0.0.0.0:41234\n
\nconst dgram = require('node:dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.error(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n const address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// Prints: server listening 0.0.0.0:41234\n
",
"classes": [
{
"textRaw": "Class: `dgram.Socket`",
"type": "class",
"name": "dgram.Socket",
"meta": {
"added": [
"v0.1.99"
],
"changes": []
},
"desc": "Encapsulates the datagram functionality.
\nNew instances of dgram.Socket
are created using dgram.createSocket()
.\nThe new
keyword is not to be used to create dgram.Socket
instances.
The 'close'
event is emitted after a socket is closed with close()
.\nOnce triggered, no new 'message'
events will be emitted on this socket.
The 'connect'
event is emitted after a socket is associated to a remote\naddress as a result of a successful connect()
call.
The 'error'
event is emitted whenever any error occurs. The event handler\nfunction is passed a single Error
object.
The 'listening'
event is emitted once the dgram.Socket
is addressable and\ncan receive data. This happens either explicitly with socket.bind()
or\nimplicitly the first time data is sent using socket.send()
.\nUntil the dgram.Socket
is listening, the underlying system resources do not\nexist and calls such as socket.address()
and socket.setTTL()
will fail.
The 'message'
event is emitted when a new datagram is available on a socket.\nThe event handler function is passed two arguments: msg
and rinfo
.
If the source address of the incoming packet is an IPv6 link-local\naddress, the interface name is added to the address
. For\nexample, a packet received on the en0
interface might have the\naddress field set to 'fe80::2618:1234:ab11:3b9c%en0'
, where '%en0'
\nis the interface name as a zone ID suffix.
Tells the kernel to join a multicast group at the given multicastAddress
and\nmulticastInterface
using the IP_ADD_MEMBERSHIP
socket option. If the\nmulticastInterface
argument is not specified, the operating system will choose\none interface and will add membership to it. To add membership to every\navailable interface, call addMembership
multiple times, once per interface.
When called on an unbound socket, this method will implicitly bind to a random\nport, listening on all interfaces.
\nWhen sharing a UDP socket across multiple cluster
workers, the\nsocket.addMembership()
function must be called only once or an\nEADDRINUSE
error will occur:
import cluster from 'node:cluster';\nimport dgram from 'node:dgram';\n\nif (cluster.isPrimary) {\n cluster.fork(); // Works ok.\n cluster.fork(); // Fails with EADDRINUSE.\n} else {\n const s = dgram.createSocket('udp4');\n s.bind(1234, () => {\n s.addMembership('224.0.0.114');\n });\n}\n
\nconst cluster = require('node:cluster');\nconst dgram = require('node:dgram');\n\nif (cluster.isPrimary) {\n cluster.fork(); // Works ok.\n cluster.fork(); // Fails with EADDRINUSE.\n} else {\n const s = dgram.createSocket('udp4');\n s.bind(1234, () => {\n s.addMembership('224.0.0.114');\n });\n}\n
"
},
{
"textRaw": "`socket.addSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])`",
"type": "method",
"name": "addSourceSpecificMembership",
"meta": {
"added": [
"v13.1.0",
"v12.16.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`sourceAddress` {string}",
"name": "sourceAddress",
"type": "string"
},
{
"textRaw": "`groupAddress` {string}",
"name": "groupAddress",
"type": "string"
},
{
"textRaw": "`multicastInterface` {string}",
"name": "multicastInterface",
"type": "string"
}
]
}
],
"desc": "Tells the kernel to join a source-specific multicast channel at the given\nsourceAddress
and groupAddress
, using the multicastInterface
with the\nIP_ADD_SOURCE_MEMBERSHIP
socket option. If the multicastInterface
argument\nis not specified, the operating system will choose one interface and will add\nmembership to it. To add membership to every available interface, call\nsocket.addSourceSpecificMembership()
multiple times, once per interface.
When called on an unbound socket, this method will implicitly bind to a random\nport, listening on all interfaces.
" }, { "textRaw": "`socket.address()`", "type": "method", "name": "address", "meta": { "added": [ "v0.1.99" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "Returns an object containing the address information for a socket.\nFor UDP sockets, this object will contain address
, family
, and port
\nproperties.
This method throws EBADF
if called on an unbound socket.
For UDP sockets, causes the dgram.Socket
to listen for datagram\nmessages on a named port
and optional address
. If port
is not\nspecified or is 0
, the operating system will attempt to bind to a\nrandom port. If address
is not specified, the operating system will\nattempt to listen on all addresses. Once binding is complete, a\n'listening'
event is emitted and the optional callback
function is\ncalled.
Specifying both a 'listening'
event listener and passing a\ncallback
to the socket.bind()
method is not harmful but not very\nuseful.
A bound datagram socket keeps the Node.js process running to receive\ndatagram messages.
\nIf binding fails, an 'error'
event is generated. In rare case (e.g.\nattempting to bind with a closed socket), an Error
may be thrown.
Example of a UDP server listening on port 41234:
\nimport dgram from 'node:dgram';\n\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.error(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n const address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// Prints: server listening 0.0.0.0:41234\n
\nconst dgram = require('node:dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.error(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n const address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// Prints: server listening 0.0.0.0:41234\n
"
},
{
"textRaw": "`socket.bind(options[, callback])`",
"type": "method",
"name": "bind",
"meta": {
"added": [
"v0.11.14"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`options` {Object} Required. Supports the following properties:",
"name": "options",
"type": "Object",
"desc": "Required. Supports the following properties:",
"options": [
{
"textRaw": "`port` {integer}",
"name": "port",
"type": "integer"
},
{
"textRaw": "`address` {string}",
"name": "address",
"type": "string"
},
{
"textRaw": "`exclusive` {boolean}",
"name": "exclusive",
"type": "boolean"
},
{
"textRaw": "`fd` {integer}",
"name": "fd",
"type": "integer"
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "For UDP sockets, causes the dgram.Socket
to listen for datagram\nmessages on a named port
and optional address
that are passed as\nproperties of an options
object passed as the first argument. If\nport
is not specified or is 0
, the operating system will attempt\nto bind to a random port. If address
is not specified, the operating\nsystem will attempt to listen on all addresses. Once binding is\ncomplete, a 'listening'
event is emitted and the optional callback
\nfunction is called.
The options
object may contain a fd
property. When a fd
greater\nthan 0
is set, it will wrap around an existing socket with the given\nfile descriptor. In this case, the properties of port
and address
\nwill be ignored.
Specifying both a 'listening'
event listener and passing a\ncallback
to the socket.bind()
method is not harmful but not very\nuseful.
The options
object may contain an additional exclusive
property that is\nused when using dgram.Socket
objects with the cluster
module. When\nexclusive
is set to false
(the default), cluster workers will use the same\nunderlying socket handle allowing connection handling duties to be shared.\nWhen exclusive
is true
, however, the handle is not shared and attempted\nport sharing results in an error.
A bound datagram socket keeps the Node.js process running to receive\ndatagram messages.
\nIf binding fails, an 'error'
event is generated. In rare case (e.g.\nattempting to bind with a closed socket), an Error
may be thrown.
An example socket listening on an exclusive port is shown below.
\nsocket.bind({\n address: 'localhost',\n port: 8000,\n exclusive: true,\n});\n
"
},
{
"textRaw": "`socket.close([callback])`",
"type": "method",
"name": "close",
"meta": {
"added": [
"v0.1.99"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`callback` {Function} Called when the socket has been closed.",
"name": "callback",
"type": "Function",
"desc": "Called when the socket has been closed."
}
]
}
],
"desc": "Close the underlying socket and stop listening for data on it. If a callback is\nprovided, it is added as a listener for the 'close'
event.
Calls socket.close()
and returns a promise that fulfills when the\nsocket has closed.
Associates the dgram.Socket
to a remote address and port. Every\nmessage sent by this handle is automatically sent to that destination. Also,\nthe socket will only receive messages from that remote peer.\nTrying to call connect()
on an already connected socket will result\nin an ERR_SOCKET_DGRAM_IS_CONNECTED
exception. If address
is not\nprovided, '127.0.0.1'
(for udp4
sockets) or '::1'
(for udp6
sockets)\nwill be used by default. Once the connection is complete, a 'connect'
event\nis emitted and the optional callback
function is called. In case of failure,\nthe callback
is called or, failing this, an 'error'
event is emitted.
A synchronous function that disassociates a connected dgram.Socket
from\nits remote address. Trying to call disconnect()
on an unbound or already\ndisconnected socket will result in an ERR_SOCKET_DGRAM_NOT_CONNECTED
\nexception.
Instructs the kernel to leave a multicast group at multicastAddress
using the\nIP_DROP_MEMBERSHIP
socket option. This method is automatically called by the\nkernel when the socket is closed or the process terminates, so most apps will\nnever have reason to call this.
If multicastInterface
is not specified, the operating system will attempt to\ndrop membership on all valid interfaces.
Instructs the kernel to leave a source-specific multicast channel at the given\nsourceAddress
and groupAddress
using the IP_DROP_SOURCE_MEMBERSHIP
\nsocket option. This method is automatically called by the kernel when the\nsocket is closed or the process terminates, so most apps will never have\nreason to call this.
If multicastInterface
is not specified, the operating system will attempt to\ndrop membership on all valid interfaces.
This method throws ERR_SOCKET_BUFFER_SIZE
if called on an unbound socket.
This method throws ERR_SOCKET_BUFFER_SIZE
if called on an unbound socket.
By default, binding a socket will cause it to block the Node.js process from\nexiting as long as the socket is open. The socket.unref()
method can be used\nto exclude the socket from the reference counting that keeps the Node.js\nprocess active. The socket.ref()
method adds the socket back to the reference\ncounting and restores the default behavior.
Calling socket.ref()
multiples times will have no additional effect.
The socket.ref()
method returns a reference to the socket so calls can be\nchained.
Returns an object containing the address
, family
, and port
of the remote\nendpoint. This method throws an ERR_SOCKET_DGRAM_NOT_CONNECTED
exception\nif the socket is not connected.
Broadcasts a datagram on the socket.\nFor connectionless sockets, the destination port
and address
must be\nspecified. Connected sockets, on the other hand, will use their associated\nremote endpoint, so the port
and address
arguments must not be set.
The msg
argument contains the message to be sent.\nDepending on its type, different behavior can apply. If msg
is a Buffer
,\nany TypedArray
or a DataView
,\nthe offset
and length
specify the offset within the Buffer
where the\nmessage begins and the number of bytes in the message, respectively.\nIf msg
is a String
, then it is automatically converted to a Buffer
\nwith 'utf8'
encoding. With messages that\ncontain multi-byte characters, offset
and length
will be calculated with\nrespect to byte length and not the character position.\nIf msg
is an array, offset
and length
must not be specified.
The address
argument is a string. If the value of address
is a host name,\nDNS will be used to resolve the address of the host. If address
is not\nprovided or otherwise nullish, '127.0.0.1'
(for udp4
sockets) or '::1'
\n(for udp6
sockets) will be used by default.
If the socket has not been previously bound with a call to bind
, the socket\nis assigned a random port number and is bound to the \"all interfaces\" address\n('0.0.0.0'
for udp4
sockets, '::0'
for udp6
sockets.)
An optional callback
function may be specified to as a way of reporting\nDNS errors or for determining when it is safe to reuse the buf
object.\nDNS lookups delay the time to send for at least one tick of the\nNode.js event loop.
The only way to know for sure that the datagram has been sent is by using a\ncallback
. If an error occurs and a callback
is given, the error will be\npassed as the first argument to the callback
. If a callback
is not given,\nthe error is emitted as an 'error'
event on the socket
object.
Offset and length are optional but both must be set if either are used.\nThey are supported only when the first argument is a Buffer
, a TypedArray
,\nor a DataView
.
This method throws ERR_SOCKET_BAD_PORT
if called on an unbound socket.
Example of sending a UDP packet to a port on localhost
;
import dgram from 'node:dgram';\nimport { Buffer } from 'node:buffer';\n\nconst message = Buffer.from('Some bytes');\nconst client = dgram.createSocket('udp4');\nclient.send(message, 41234, 'localhost', (err) => {\n client.close();\n});\n
\nconst dgram = require('node:dgram');\nconst { Buffer } = require('node:buffer');\n\nconst message = Buffer.from('Some bytes');\nconst client = dgram.createSocket('udp4');\nclient.send(message, 41234, 'localhost', (err) => {\n client.close();\n});\n
\nExample of sending a UDP packet composed of multiple buffers to a port on\n127.0.0.1
;
import dgram from 'node:dgram';\nimport { Buffer } from 'node:buffer';\n\nconst buf1 = Buffer.from('Some ');\nconst buf2 = Buffer.from('bytes');\nconst client = dgram.createSocket('udp4');\nclient.send([buf1, buf2], 41234, (err) => {\n client.close();\n});\n
\nconst dgram = require('node:dgram');\nconst { Buffer } = require('node:buffer');\n\nconst buf1 = Buffer.from('Some ');\nconst buf2 = Buffer.from('bytes');\nconst client = dgram.createSocket('udp4');\nclient.send([buf1, buf2], 41234, (err) => {\n client.close();\n});\n
\nSending multiple buffers might be faster or slower depending on the\napplication and operating system. Run benchmarks to\ndetermine the optimal strategy on a case-by-case basis. Generally speaking,\nhowever, sending multiple buffers is faster.
\nExample of sending a UDP packet using a socket connected to a port on\nlocalhost
:
import dgram from 'node:dgram';\nimport { Buffer } from 'node:buffer';\n\nconst message = Buffer.from('Some bytes');\nconst client = dgram.createSocket('udp4');\nclient.connect(41234, 'localhost', (err) => {\n client.send(message, (err) => {\n client.close();\n });\n});\n
\nconst dgram = require('node:dgram');\nconst { Buffer } = require('node:buffer');\n\nconst message = Buffer.from('Some bytes');\nconst client = dgram.createSocket('udp4');\nclient.connect(41234, 'localhost', (err) => {\n client.send(message, (err) => {\n client.close();\n });\n});\n
",
"modules": [
{
"textRaw": "Note about UDP datagram size",
"name": "note_about_udp_datagram_size",
"desc": "The maximum size of an IPv4/v6 datagram depends on the MTU
\n(Maximum Transmission Unit) and on the Payload Length
field size.
The Payload Length
field is 16 bits wide, which means that a normal\npayload cannot exceed 64K octets including the internet header and data\n(65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header);\nthis is generally true for loopback interfaces, but such long datagram\nmessages are impractical for most hosts and networks.
The MTU
is the largest size a given link layer technology can support for\ndatagram messages. For any link, IPv4 mandates a minimum MTU
of 68\noctets, while the recommended MTU
for IPv4 is 576 (typically recommended\nas the MTU
for dial-up type applications), whether they arrive whole or in\nfragments.
For IPv6, the minimum MTU
is 1280 octets. However, the mandatory minimum\nfragment reassembly buffer size is 1500 octets. The value of 68 octets is\nvery small, since most current link layer technologies, like Ethernet, have a\nminimum MTU
of 1500.
It is impossible to know in advance the MTU of each link through which\na packet might travel. Sending a datagram greater than the receiver MTU
will\nnot work because the packet will get silently dropped without informing the\nsource that the data did not reach its intended recipient.
Sets or clears the SO_BROADCAST
socket option. When set to true
, UDP\npackets may be sent to a local interface's broadcast address.
This method throws EBADF
if called on an unbound socket.
All references to scope in this section are referring to\nIPv6 Zone Indices, which are defined by RFC 4007. In string form, an IP\nwith a scope index is written as 'IP%scope'
where scope is an interface name\nor interface number.
Sets the default outgoing multicast interface of the socket to a chosen\ninterface or back to system interface selection. The multicastInterface
must\nbe a valid string representation of an IP from the socket's family.
For IPv4 sockets, this should be the IP configured for the desired physical\ninterface. All packets sent to multicast on the socket will be sent on the\ninterface determined by the most recent successful use of this call.
\nFor IPv6 sockets, multicastInterface
should include a scope to indicate the\ninterface as in the examples that follow. In IPv6, individual send
calls can\nalso use explicit scope in addresses, so only packets sent to a multicast\naddress without specifying an explicit scope are affected by the most recent\nsuccessful use of this call.
This method throws EBADF
if called on an unbound socket.
On most systems, where scope format uses the interface name:
\nconst socket = dgram.createSocket('udp6');\n\nsocket.bind(1234, () => {\n socket.setMulticastInterface('::%eth1');\n});\n
\nOn Windows, where scope format uses an interface number:
\nconst socket = dgram.createSocket('udp6');\n\nsocket.bind(1234, () => {\n socket.setMulticastInterface('::%2');\n});\n
\nAll systems use an IP of the host on the desired physical interface:
\nconst socket = dgram.createSocket('udp4');\n\nsocket.bind(1234, () => {\n socket.setMulticastInterface('10.0.0.2');\n});\n
",
"modules": [
{
"textRaw": "Call results",
"name": "call_results",
"desc": "A call on a socket that is not ready to send or no longer open may throw a Not\nrunning Error
.
If multicastInterface
can not be parsed into an IP then an EINVAL\nSystem Error
is thrown.
On IPv4, if multicastInterface
is a valid address but does not match any\ninterface, or if the address does not match the family then\na System Error
such as EADDRNOTAVAIL
or EPROTONOSUP
is thrown.
On IPv6, most errors with specifying or omitting scope will result in the socket\ncontinuing to use (or returning to) the system's default interface selection.
\nA socket's address family's ANY address (IPv4 '0.0.0.0'
or IPv6 '::'
) can be\nused to return control of the sockets default outgoing interface to the system\nfor future multicast packets.
Sets or clears the IP_MULTICAST_LOOP
socket option. When set to true
,\nmulticast packets will also be received on the local interface.
This method throws EBADF
if called on an unbound socket.
Sets the IP_MULTICAST_TTL
socket option. While TTL generally stands for\n\"Time to Live\", in this context it specifies the number of IP hops that a\npacket is allowed to travel through, specifically for multicast traffic. Each\nrouter or gateway that forwards a packet decrements the TTL. If the TTL is\ndecremented to 0 by a router, it will not be forwarded.
The ttl
argument may be between 0 and 255. The default on most systems is 1
.
This method throws EBADF
if called on an unbound socket.
Sets the SO_RCVBUF
socket option. Sets the maximum socket receive buffer\nin bytes.
This method throws ERR_SOCKET_BUFFER_SIZE
if called on an unbound socket.
Sets the SO_SNDBUF
socket option. Sets the maximum socket send buffer\nin bytes.
This method throws ERR_SOCKET_BUFFER_SIZE
if called on an unbound socket.
Sets the IP_TTL
socket option. While TTL generally stands for \"Time to Live\",\nin this context it specifies the number of IP hops that a packet is allowed to\ntravel through. Each router or gateway that forwards a packet decrements the\nTTL. If the TTL is decremented to 0 by a router, it will not be forwarded.\nChanging TTL values is typically done for network probes or when multicasting.
The ttl
argument may be between 1 and 255. The default on most systems\nis 64.
This method throws EBADF
if called on an unbound socket.
By default, binding a socket will cause it to block the Node.js process from\nexiting as long as the socket is open. The socket.unref()
method can be used\nto exclude the socket from the reference counting that keeps the Node.js\nprocess active, allowing the process to exit even if the socket is still\nlistening.
Calling socket.unref()
multiple times will have no additional effect.
The socket.unref()
method returns a reference to the socket so calls can be\nchained.
Creates a dgram.Socket
object. Once the socket is created, calling\nsocket.bind()
will instruct the socket to begin listening for datagram\nmessages. When address
and port
are not passed to socket.bind()
the\nmethod will bind the socket to the \"all interfaces\" address on a random port\n(it does the right thing for both udp4
and udp6
sockets). The bound address\nand port can be retrieved using socket.address().address
and\nsocket.address().port
.
If the signal
option is enabled, calling .abort()
on the corresponding\nAbortController
is similar to calling .close()
on the socket:
const controller = new AbortController();\nconst { signal } = controller;\nconst server = dgram.createSocket({ type: 'udp4', signal });\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n// Later, when you want to close the server.\ncontroller.abort();\n
"
},
{
"textRaw": "`dgram.createSocket(type[, callback])`",
"type": "method",
"name": "createSocket",
"meta": {
"added": [
"v0.1.99"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {dgram.Socket}",
"name": "return",
"type": "dgram.Socket"
},
"params": [
{
"textRaw": "`type` {string} Either `'udp4'` or `'udp6'`.",
"name": "type",
"type": "string",
"desc": "Either `'udp4'` or `'udp6'`."
},
{
"textRaw": "`callback` {Function} Attached as a listener to `'message'` events.",
"name": "callback",
"type": "Function",
"desc": "Attached as a listener to `'message'` events."
}
]
}
],
"desc": "Creates a dgram.Socket
object of the specified type
.
Once the socket is created, calling socket.bind()
will instruct the\nsocket to begin listening for datagram messages. When address
and port
are\nnot passed to socket.bind()
the method will bind the socket to the \"all\ninterfaces\" address on a random port (it does the right thing for both udp4
\nand udp6
sockets). The bound address and port can be retrieved using\nsocket.address().address
and socket.address().port
.
Source Code: lib/url.js
\nThe node:url
module provides utilities for URL resolution and parsing. It can\nbe accessed using:
import url from 'node:url';\n
\nconst url = require('node:url');\n
",
"modules": [
{
"textRaw": "URL strings and URL objects",
"name": "url_strings_and_url_objects",
"desc": "A URL string is a structured string containing multiple meaningful components.\nWhen parsed, a URL object is returned containing properties for each of these\ncomponents.
\nThe node:url
module provides two APIs for working with URLs: a legacy API that\nis Node.js specific, and a newer API that implements the same\nWHATWG URL Standard used by web browsers.
A comparison between the WHATWG and legacy APIs is provided below. Above the URL\n'https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash'
, properties\nof an object returned by the legacy url.parse()
are shown. Below it are\nproperties of a WHATWG URL
object.
WHATWG URL's origin
property includes protocol
and host
, but not\nusername
or password
.
┌────────────────────────────────────────────────────────────────────────────────────────────────┐\n│ href │\n├──────────┬──┬─────────────────────┬────────────────────────┬───────────────────────────┬───────┤\n│ protocol │ │ auth │ host │ path │ hash │\n│ │ │ ├─────────────────┬──────┼──────────┬────────────────┤ │\n│ │ │ │ hostname │ port │ pathname │ search │ │\n│ │ │ │ │ │ ├─┬──────────────┤ │\n│ │ │ │ │ │ │ │ query │ │\n\" https: // user : pass @ sub.example.com : 8080 /p/a/t/h ? query=string #hash \"\n│ │ │ │ │ hostname │ port │ │ │ │\n│ │ │ │ ├─────────────────┴──────┤ │ │ │\n│ protocol │ │ username │ password │ host │ │ │ │\n├──────────┴──┼──────────┴──────────┼────────────────────────┤ │ │ │\n│ origin │ │ origin │ pathname │ search │ hash │\n├─────────────┴─────────────────────┴────────────────────────┴──────────┴────────────────┴───────┤\n│ href │\n└────────────────────────────────────────────────────────────────────────────────────────────────┘\n(All spaces in the \"\" line should be ignored. They are purely for formatting.)\n
\nParsing the URL string using the WHATWG API:
\nconst myURL =\n new URL('https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash');\n
\nParsing the URL string using the legacy API:
\nimport url from 'node:url';\nconst myURL =\n url.parse('https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash');\n
\nconst url = require('node:url');\nconst myURL =\n url.parse('https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash');\n
",
"modules": [
{
"textRaw": "Constructing a URL from component parts and getting the constructed string",
"name": "constructing_a_url_from_component_parts_and_getting_the_constructed_string",
"desc": "It is possible to construct a WHATWG URL from component parts using either the\nproperty setters or a template literal string:
\nconst myURL = new URL('https://example.org');\nmyURL.pathname = '/a/b/c';\nmyURL.search = '?d=e';\nmyURL.hash = '#fgh';\n
\nconst pathname = '/a/b/c';\nconst search = '?d=e';\nconst hash = '#fgh';\nconst myURL = new URL(`https://example.org${pathname}${search}${hash}`);\n
\nTo get the constructed URL string, use the href
property accessor:
console.log(myURL.href);\n
",
"type": "module",
"displayName": "Constructing a URL from component parts and getting the constructed string"
}
],
"type": "module",
"displayName": "URL strings and URL objects"
},
{
"textRaw": "The WHATWG URL API",
"name": "the_whatwg_url_api",
"classes": [
{
"textRaw": "Class: `URL`",
"type": "class",
"name": "URL",
"meta": {
"added": [
"v7.0.0",
"v6.13.0"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18281",
"description": "The class is now available on the global object."
}
]
},
"desc": "Browser-compatible URL
class, implemented by following the WHATWG URL\nStandard. Examples of parsed URLs may be found in the Standard itself.\nThe URL
class is also available on the global object.
In accordance with browser conventions, all properties of URL
objects\nare implemented as getters and setters on the class prototype, rather than as\ndata properties on the object itself. Thus, unlike legacy urlObject
s,\nusing the delete
keyword on any properties of URL
objects (e.g. delete myURL.protocol
, delete myURL.pathname
, etc) has no effect but will still\nreturn true
.
Gets and sets the fragment portion of the URL.
\nconst myURL = new URL('https://example.org/foo#bar');\nconsole.log(myURL.hash);\n// Prints #bar\n\nmyURL.hash = 'baz';\nconsole.log(myURL.href);\n// Prints https://example.org/foo#baz\n
\nInvalid URL characters included in the value assigned to the hash
property\nare percent-encoded. The selection of which characters to\npercent-encode may vary somewhat from what the url.parse()
and\nurl.format()
methods would produce.
Gets and sets the host portion of the URL.
\nconst myURL = new URL('https://example.org:81/foo');\nconsole.log(myURL.host);\n// Prints example.org:81\n\nmyURL.host = 'example.com:82';\nconsole.log(myURL.href);\n// Prints https://example.com:82/foo\n
\nInvalid host values assigned to the host
property are ignored.
Gets and sets the host name portion of the URL. The key difference between\nurl.host
and url.hostname
is that url.hostname
does not include the\nport.
const myURL = new URL('https://example.org:81/foo');\nconsole.log(myURL.hostname);\n// Prints example.org\n\n// Setting the hostname does not change the port\nmyURL.hostname = 'example.com';\nconsole.log(myURL.href);\n// Prints https://example.com:81/foo\n\n// Use myURL.host to change the hostname and port\nmyURL.host = 'example.org:82';\nconsole.log(myURL.href);\n// Prints https://example.org:82/foo\n
\nInvalid host name values assigned to the hostname
property are ignored.
Gets and sets the serialized URL.
\nconst myURL = new URL('https://example.org/foo');\nconsole.log(myURL.href);\n// Prints https://example.org/foo\n\nmyURL.href = 'https://example.com/bar';\nconsole.log(myURL.href);\n// Prints https://example.com/bar\n
\nGetting the value of the href
property is equivalent to calling\nurl.toString()
.
Setting the value of this property to a new value is equivalent to creating a\nnew URL
object using new URL(value)
. Each of the URL
\nobject's properties will be modified.
If the value assigned to the href
property is not a valid URL, a TypeError
\nwill be thrown.
Gets the read-only serialization of the URL's origin.
\nconst myURL = new URL('https://example.org/foo/bar?baz');\nconsole.log(myURL.origin);\n// Prints https://example.org\n
\nconst idnURL = new URL('https://測試');\nconsole.log(idnURL.origin);\n// Prints https://xn--g6w251d\n\nconsole.log(idnURL.hostname);\n// Prints xn--g6w251d\n
"
},
{
"textRaw": "`password` {string}",
"type": "string",
"name": "password",
"desc": "Gets and sets the password portion of the URL.
\nconst myURL = new URL('https://abc:xyz@example.com');\nconsole.log(myURL.password);\n// Prints xyz\n\nmyURL.password = '123';\nconsole.log(myURL.href);\n// Prints https://abc:123@example.com/\n
\nInvalid URL characters included in the value assigned to the password
property\nare percent-encoded. The selection of which characters to\npercent-encode may vary somewhat from what the url.parse()
and\nurl.format()
methods would produce.
Gets and sets the path portion of the URL.
\nconst myURL = new URL('https://example.org/abc/xyz?123');\nconsole.log(myURL.pathname);\n// Prints /abc/xyz\n\nmyURL.pathname = '/abcdef';\nconsole.log(myURL.href);\n// Prints https://example.org/abcdef?123\n
\nInvalid URL characters included in the value assigned to the pathname
\nproperty are percent-encoded. The selection of which characters\nto percent-encode may vary somewhat from what the url.parse()
and\nurl.format()
methods would produce.
Gets and sets the port portion of the URL.
\nThe port value may be a number or a string containing a number in the range\n0
to 65535
(inclusive). Setting the value to the default port of the\nURL
objects given protocol
will result in the port
value becoming\nthe empty string (''
).
The port value can be an empty string in which case the port depends on\nthe protocol/scheme:
\nprotocol | \nport | \n
---|---|
\"ftp\" | \n21 | \n
\"file\" | \n\n |
\"http\" | \n80 | \n
\"https\" | \n443 | \n
\"ws\" | \n80 | \n
\"wss\" | \n443 | \n
Upon assigning a value to the port, the value will first be converted to a\nstring using .toString()
.
If that string is invalid but it begins with a number, the leading number is\nassigned to port
.\nIf the number lies outside the range denoted above, it is ignored.
const myURL = new URL('https://example.org:8888');\nconsole.log(myURL.port);\n// Prints 8888\n\n// Default ports are automatically transformed to the empty string\n// (HTTPS protocol's default port is 443)\nmyURL.port = '443';\nconsole.log(myURL.port);\n// Prints the empty string\nconsole.log(myURL.href);\n// Prints https://example.org/\n\nmyURL.port = 1234;\nconsole.log(myURL.port);\n// Prints 1234\nconsole.log(myURL.href);\n// Prints https://example.org:1234/\n\n// Completely invalid port strings are ignored\nmyURL.port = 'abcd';\nconsole.log(myURL.port);\n// Prints 1234\n\n// Leading numbers are treated as a port number\nmyURL.port = '5678abcd';\nconsole.log(myURL.port);\n// Prints 5678\n\n// Non-integers are truncated\nmyURL.port = 1234.5678;\nconsole.log(myURL.port);\n// Prints 1234\n\n// Out-of-range numbers which are not represented in scientific notation\n// will be ignored.\nmyURL.port = 1e10; // 10000000000, will be range-checked as described below\nconsole.log(myURL.port);\n// Prints 1234\n
\nNumbers which contain a decimal point,\nsuch as floating-point numbers or numbers in scientific notation,\nare not an exception to this rule.\nLeading numbers up to the decimal point will be set as the URL's port,\nassuming they are valid:
\nmyURL.port = 4.567e21;\nconsole.log(myURL.port);\n// Prints 4 (because it is the leading number in the string '4.567e21')\n
"
},
{
"textRaw": "`protocol` {string}",
"type": "string",
"name": "protocol",
"desc": "Gets and sets the protocol portion of the URL.
\nconst myURL = new URL('https://example.org');\nconsole.log(myURL.protocol);\n// Prints https:\n\nmyURL.protocol = 'ftp';\nconsole.log(myURL.href);\n// Prints ftp://example.org/\n
\nInvalid URL protocol values assigned to the protocol
property are ignored.
The WHATWG URL Standard considers a handful of URL protocol schemes to be\nspecial in terms of how they are parsed and serialized. When a URL is\nparsed using one of these special protocols, the url.protocol
property\nmay be changed to another special protocol but cannot be changed to a\nnon-special protocol, and vice versa.
For instance, changing from http
to https
works:
const u = new URL('http://example.org');\nu.protocol = 'https';\nconsole.log(u.href);\n// https://example.org/\n
\nHowever, changing from http
to a hypothetical fish
protocol does not\nbecause the new protocol is not special.
const u = new URL('http://example.org');\nu.protocol = 'fish';\nconsole.log(u.href);\n// http://example.org/\n
\nLikewise, changing from a non-special protocol to a special protocol is also\nnot permitted:
\nconst u = new URL('fish://example.org');\nu.protocol = 'http';\nconsole.log(u.href);\n// fish://example.org\n
\nAccording to the WHATWG URL Standard, special protocol schemes are ftp
,\nfile
, http
, https
, ws
, and wss
.
Gets and sets the serialized query portion of the URL.
\nconst myURL = new URL('https://example.org/abc?123');\nconsole.log(myURL.search);\n// Prints ?123\n\nmyURL.search = 'abc=xyz';\nconsole.log(myURL.href);\n// Prints https://example.org/abc?abc=xyz\n
\nAny invalid URL characters appearing in the value assigned the search
\nproperty will be percent-encoded. The selection of which\ncharacters to percent-encode may vary somewhat from what the url.parse()
\nand url.format()
methods would produce.
Gets the URLSearchParams
object representing the query parameters of the\nURL. This property is read-only but the URLSearchParams
object it provides\ncan be used to mutate the URL instance; to replace the entirety of query\nparameters of the URL, use the url.search
setter. See\nURLSearchParams
documentation for details.
Use care when using .searchParams
to modify the URL
because,\nper the WHATWG specification, the URLSearchParams
object uses\ndifferent rules to determine which characters to percent-encode. For\ninstance, the URL
object will not percent encode the ASCII tilde (~
)\ncharacter, while URLSearchParams
will always encode it:
const myURL = new URL('https://example.org/abc?foo=~bar');\n\nconsole.log(myURL.search); // prints ?foo=~bar\n\n// Modify the URL via searchParams...\nmyURL.searchParams.sort();\n\nconsole.log(myURL.search); // prints ?foo=%7Ebar\n
"
},
{
"textRaw": "`username` {string}",
"type": "string",
"name": "username",
"desc": "Gets and sets the username portion of the URL.
\nconst myURL = new URL('https://abc:xyz@example.com');\nconsole.log(myURL.username);\n// Prints abc\n\nmyURL.username = '123';\nconsole.log(myURL.href);\n// Prints https://123:xyz@example.com/\n
\nAny invalid URL characters appearing in the value assigned the username
\nproperty will be percent-encoded. The selection of which\ncharacters to percent-encode may vary somewhat from what the url.parse()
\nand url.format()
methods would produce.
The toString()
method on the URL
object returns the serialized URL. The\nvalue returned is equivalent to that of url.href
and url.toJSON()
.
The toJSON()
method on the URL
object returns the serialized URL. The\nvalue returned is equivalent to that of url.href
and\nurl.toString()
.
This method is automatically called when an URL
object is serialized\nwith JSON.stringify()
.
const myURLs = [\n new URL('https://www.example.com'),\n new URL('https://test.example.org'),\n];\nconsole.log(JSON.stringify(myURLs));\n// Prints [\"https://www.example.com/\",\"https://test.example.org/\"]\n
"
},
{
"textRaw": "`URL.createObjectURL(blob)`",
"type": "method",
"name": "createObjectURL",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`blob` {Blob}",
"name": "blob",
"type": "Blob"
}
]
}
],
"desc": "Creates a 'blob:nodedata:...'
URL string that represents the given <Blob>\nobject and can be used to retrieve the Blob
later.
const {\n Blob,\n resolveObjectURL,\n} = require('node:buffer');\n\nconst blob = new Blob(['hello']);\nconst id = URL.createObjectURL(blob);\n\n// later...\n\nconst otherBlob = resolveObjectURL(id);\nconsole.log(otherBlob.size);\n
\nThe data stored by the registered <Blob> will be retained in memory until\nURL.revokeObjectURL()
is called to remove it.
Blob
objects are registered within the current thread. If using Worker\nThreads, Blob
objects registered within one Worker will not be available\nto other workers or the main thread.
Removes the stored <Blob> identified by the given ID. Attempting to revoke a\nID that isn't registered will silently fail.
" }, { "textRaw": "`URL.canParse(input[, base])`", "type": "method", "name": "canParse", "meta": { "added": [ "v19.9.0", "v18.17.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`input` {string} The absolute or relative input URL to parse. If `input` is relative, then `base` is required. If `input` is absolute, the `base` is ignored. If `input` is not a string, it is [converted to a string][] first.", "name": "input", "type": "string", "desc": "The absolute or relative input URL to parse. If `input` is relative, then `base` is required. If `input` is absolute, the `base` is ignored. If `input` is not a string, it is [converted to a string][] first." }, { "textRaw": "`base` {string} The base URL to resolve against if the `input` is not absolute. If `base` is not a string, it is [converted to a string][] first.", "name": "base", "type": "string", "desc": "The base URL to resolve against if the `input` is not absolute. If `base` is not a string, it is [converted to a string][] first." } ] } ], "desc": "Checks if an input
relative to the base
can be parsed to a URL
.
const isValid = URL.canParse('/foo', 'https://example.org/'); // true\n\nconst isNotValid = URL.canParse('/foo'); // false\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`input` {string} The absolute or relative input URL to parse. If `input` is relative, then `base` is required. If `input` is absolute, the `base` is ignored. If `input` is not a string, it is [converted to a string][] first.",
"name": "input",
"type": "string",
"desc": "The absolute or relative input URL to parse. If `input` is relative, then `base` is required. If `input` is absolute, the `base` is ignored. If `input` is not a string, it is [converted to a string][] first."
},
{
"textRaw": "`base` {string} The base URL to resolve against if the `input` is not absolute. If `base` is not a string, it is [converted to a string][] first.",
"name": "base",
"type": "string",
"desc": "The base URL to resolve against if the `input` is not absolute. If `base` is not a string, it is [converted to a string][] first."
}
],
"desc": "Creates a new URL
object by parsing the input
relative to the base
. If\nbase
is passed as a string, it will be parsed equivalent to new URL(base)
.
const myURL = new URL('/foo', 'https://example.org/');\n// https://example.org/foo\n
\nThe URL constructor is accessible as a property on the global object.\nIt can also be imported from the built-in url module:
\nimport { URL } from 'node:url';\nconsole.log(URL === globalThis.URL); // Prints 'true'.\n
\nconsole.log(URL === require('node:url').URL); // Prints 'true'.\n
\nA TypeError
will be thrown if the input
or base
are not valid URLs. Note\nthat an effort will be made to coerce the given values into strings. For\ninstance:
const myURL = new URL({ toString: () => 'https://example.org/' });\n// https://example.org/\n
\nUnicode characters appearing within the host name of input
will be\nautomatically converted to ASCII using the Punycode algorithm.
const myURL = new URL('https://測試');\n// https://xn--g6w251d/\n
\nIn cases where it is not known in advance if input
is an absolute URL\nand a base
is provided, it is advised to validate that the origin
of\nthe URL
object is what is expected.
let myURL = new URL('http://Example.com/', 'https://example.org/');\n// http://example.com/\n\nmyURL = new URL('https://Example.com/', 'https://example.org/');\n// https://example.com/\n\nmyURL = new URL('foo://Example.com/', 'https://example.org/');\n// foo://Example.com/\n\nmyURL = new URL('http:Example.com/', 'https://example.org/');\n// http://example.com/\n\nmyURL = new URL('https:Example.com/', 'https://example.org/');\n// https://example.org/Example.com/\n\nmyURL = new URL('foo:Example.com/', 'https://example.org/');\n// foo:Example.com/\n
"
}
]
},
{
"textRaw": "Class: `URLSearchParams`",
"type": "class",
"name": "URLSearchParams",
"meta": {
"added": [
"v7.5.0",
"v6.13.0"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18281",
"description": "The class is now available on the global object."
}
]
},
"desc": "The URLSearchParams
API provides read and write access to the query of a\nURL
. The URLSearchParams
class can also be used standalone with one of the\nfour following constructors.\nThe URLSearchParams
class is also available on the global object.
The WHATWG URLSearchParams
interface and the querystring
module have\nsimilar purpose, but the purpose of the querystring
module is more\ngeneral, as it allows the customization of delimiter characters (&
and =
).\nOn the other hand, this API is designed purely for URL query strings.
const myURL = new URL('https://example.org/?abc=123');\nconsole.log(myURL.searchParams.get('abc'));\n// Prints 123\n\nmyURL.searchParams.append('abc', 'xyz');\nconsole.log(myURL.href);\n// Prints https://example.org/?abc=123&abc=xyz\n\nmyURL.searchParams.delete('abc');\nmyURL.searchParams.set('a', 'b');\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b\n\nconst newSearchParams = new URLSearchParams(myURL.searchParams);\n// The above is equivalent to\n// const newSearchParams = new URLSearchParams(myURL.search);\n\nnewSearchParams.append('a', 'c');\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b\nconsole.log(newSearchParams.toString());\n// Prints a=b&a=c\n\n// newSearchParams.toString() is implicitly called\nmyURL.search = newSearchParams;\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b&a=c\nnewSearchParams.delete('a');\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b&a=c\n
",
"methods": [
{
"textRaw": "`urlSearchParams.append(name, value)`",
"type": "method",
"name": "append",
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {string}",
"name": "value",
"type": "string"
}
]
}
],
"desc": "Append a new name-value pair to the query string.
" }, { "textRaw": "`urlSearchParams.delete(name[, value])`", "type": "method", "name": "delete", "meta": { "changes": [ { "version": [ "v20.2.0", "v18.18.0" ], "pr-url": "https://github.com/nodejs/node/pull/47885", "description": "Add support for optional `value` argument." } ] }, "signatures": [ { "params": [ { "textRaw": "`name` {string}", "name": "name", "type": "string" }, { "textRaw": "`value` {string}", "name": "value", "type": "string" } ] } ], "desc": "If value
is provided, removes all name-value pairs\nwhere name is name
and value is value
..
If value
is not provided, removes all name-value pairs whose name is name
.
Returns an ES6 Iterator
over each of the name-value pairs in the query.\nEach item of the iterator is a JavaScript Array
. The first item of the Array
\nis the name
, the second item of the Array
is the value
.
Alias for urlSearchParams[@@iterator]()
.
Iterates over each name-value pair in the query and invokes the given function.
\nconst myURL = new URL('https://example.org/?a=b&c=d');\nmyURL.searchParams.forEach((value, name, searchParams) => {\n console.log(name, value, myURL.searchParams === searchParams);\n});\n// Prints:\n// a b true\n// c d true\n
"
},
{
"textRaw": "`urlSearchParams.get(name)`",
"type": "method",
"name": "get",
"signatures": [
{
"return": {
"textRaw": "Returns: {string | null} A string or `null` if there is no name-value pair with the given `name`.",
"name": "return",
"type": "string | null",
"desc": "A string or `null` if there is no name-value pair with the given `name`."
},
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
}
]
}
],
"desc": "Returns the value of the first name-value pair whose name is name
. If there\nare no such pairs, null
is returned.
Returns the values of all name-value pairs whose name is name
. If there are\nno such pairs, an empty array is returned.
Checks if the URLSearchParams
object contains key-value pair(s) based on\nname
and an optional value
argument.
If value
is provided, returns true
when name-value pair with\nsame name
and value
exists.
If value
is not provided, returns true
if there is at least one name-value\npair whose name is name
.
Returns an ES6 Iterator
over the names of each name-value pair.
const params = new URLSearchParams('foo=bar&foo=baz');\nfor (const name of params.keys()) {\n console.log(name);\n}\n// Prints:\n// foo\n// foo\n
"
},
{
"textRaw": "`urlSearchParams.set(name, value)`",
"type": "method",
"name": "set",
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {string}",
"name": "value",
"type": "string"
}
]
}
],
"desc": "Sets the value in the URLSearchParams
object associated with name
to\nvalue
. If there are any pre-existing name-value pairs whose names are name
,\nset the first such pair's value to value
and remove all others. If not,\nappend the name-value pair to the query string.
const params = new URLSearchParams();\nparams.append('foo', 'bar');\nparams.append('foo', 'baz');\nparams.append('abc', 'def');\nconsole.log(params.toString());\n// Prints foo=bar&foo=baz&abc=def\n\nparams.set('foo', 'def');\nparams.set('xyz', 'opq');\nconsole.log(params.toString());\n// Prints foo=def&abc=def&xyz=opq\n
"
},
{
"textRaw": "`urlSearchParams.sort()`",
"type": "method",
"name": "sort",
"meta": {
"added": [
"v7.7.0",
"v6.13.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Sort all existing name-value pairs in-place by their names. Sorting is done\nwith a stable sorting algorithm, so relative order between name-value pairs\nwith the same name is preserved.
\nThis method can be used, in particular, to increase cache hits.
\nconst params = new URLSearchParams('query[]=abc&type=search&query[]=123');\nparams.sort();\nconsole.log(params.toString());\n// Prints query%5B%5D=abc&query%5B%5D=123&type=search\n
"
},
{
"textRaw": "`urlSearchParams.toString()`",
"type": "method",
"name": "toString",
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": []
}
],
"desc": "Returns the search parameters serialized as a string, with characters\npercent-encoded where necessary.
" }, { "textRaw": "`urlSearchParams.values()`", "type": "method", "name": "values", "signatures": [ { "return": { "textRaw": "Returns: {Iterator}", "name": "return", "type": "Iterator" }, "params": [] } ], "desc": "Returns an ES6 Iterator
over the values of each name-value pair.
Returns an ES6 Iterator
over each of the name-value pairs in the query string.\nEach item of the iterator is a JavaScript Array
. The first item of the Array
\nis the name
, the second item of the Array
is the value
.
Alias for urlSearchParams.entries()
.
const params = new URLSearchParams('foo=bar&xyz=baz');\nfor (const [name, value] of params) {\n console.log(name, value);\n}\n// Prints:\n// foo bar\n// xyz baz\n
"
}
],
"properties": [
{
"textRaw": "`urlSearchParams.size`",
"name": "size",
"meta": {
"added": [
"v19.8.0",
"v18.16.0"
],
"changes": []
},
"desc": "The total number of parameter entries.
" } ], "signatures": [ { "params": [], "desc": "Instantiate a new empty URLSearchParams
object.
Parse the string
as a query string, and use it to instantiate a new\nURLSearchParams
object. A leading '?'
, if present, is ignored.
let params;\n\nparams = new URLSearchParams('user=abc&query=xyz');\nconsole.log(params.get('user'));\n// Prints 'abc'\nconsole.log(params.toString());\n// Prints 'user=abc&query=xyz'\n\nparams = new URLSearchParams('?user=abc&query=xyz');\nconsole.log(params.toString());\n// Prints 'user=abc&query=xyz'\n
"
},
{
"params": [
{
"textRaw": "`obj` {Object} An object representing a collection of key-value pairs",
"name": "obj",
"type": "Object",
"desc": "An object representing a collection of key-value pairs"
}
],
"desc": "Instantiate a new URLSearchParams
object with a query hash map. The key and\nvalue of each property of obj
are always coerced to strings.
Unlike querystring
module, duplicate keys in the form of array values are\nnot allowed. Arrays are stringified using array.toString()
, which simply\njoins all array elements with commas.
const params = new URLSearchParams({\n user: 'abc',\n query: ['first', 'second'],\n});\nconsole.log(params.getAll('query'));\n// Prints [ 'first,second' ]\nconsole.log(params.toString());\n// Prints 'user=abc&query=first%2Csecond'\n
"
},
{
"params": [
{
"textRaw": "`iterable` {Iterable} An iterable object whose elements are key-value pairs",
"name": "iterable",
"type": "Iterable",
"desc": "An iterable object whose elements are key-value pairs"
}
],
"desc": "Instantiate a new URLSearchParams
object with an iterable map in a way that\nis similar to Map
's constructor. iterable
can be an Array
or any\niterable object. That means iterable
can be another URLSearchParams
, in\nwhich case the constructor will simply create a clone of the provided\nURLSearchParams
. Elements of iterable
are key-value pairs, and can\nthemselves be any iterable object.
Duplicate keys are allowed.
\nlet params;\n\n// Using an array\nparams = new URLSearchParams([\n ['user', 'abc'],\n ['query', 'first'],\n ['query', 'second'],\n]);\nconsole.log(params.toString());\n// Prints 'user=abc&query=first&query=second'\n\n// Using a Map object\nconst map = new Map();\nmap.set('user', 'abc');\nmap.set('query', 'xyz');\nparams = new URLSearchParams(map);\nconsole.log(params.toString());\n// Prints 'user=abc&query=xyz'\n\n// Using a generator function\nfunction* getQueryPairs() {\n yield ['user', 'abc'];\n yield ['query', 'first'];\n yield ['query', 'second'];\n}\nparams = new URLSearchParams(getQueryPairs());\nconsole.log(params.toString());\n// Prints 'user=abc&query=first&query=second'\n\n// Each key-value pair must have exactly two elements\nnew URLSearchParams([\n ['user', 'abc', 'error'],\n]);\n// Throws TypeError [ERR_INVALID_TUPLE]:\n// Each query pair must be an iterable [name, value] tuple\n
"
}
]
}
],
"methods": [
{
"textRaw": "`url.domainToASCII(domain)`",
"type": "method",
"name": "domainToASCII",
"meta": {
"added": [
"v7.4.0",
"v6.13.0"
],
"changes": [
{
"version": [
"v20.0.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47339",
"description": "ICU requirement is removed."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`domain` {string}",
"name": "domain",
"type": "string"
}
]
}
],
"desc": "Returns the Punycode ASCII serialization of the domain
. If domain
is an\ninvalid domain, the empty string is returned.
It performs the inverse operation to url.domainToUnicode()
.
import url from 'node:url';\n\nconsole.log(url.domainToASCII('español.com'));\n// Prints xn--espaol-zwa.com\nconsole.log(url.domainToASCII('中文.com'));\n// Prints xn--fiq228c.com\nconsole.log(url.domainToASCII('xn--iñvalid.com'));\n// Prints an empty string\n
\nconst url = require('node:url');\n\nconsole.log(url.domainToASCII('español.com'));\n// Prints xn--espaol-zwa.com\nconsole.log(url.domainToASCII('中文.com'));\n// Prints xn--fiq228c.com\nconsole.log(url.domainToASCII('xn--iñvalid.com'));\n// Prints an empty string\n
"
},
{
"textRaw": "`url.domainToUnicode(domain)`",
"type": "method",
"name": "domainToUnicode",
"meta": {
"added": [
"v7.4.0",
"v6.13.0"
],
"changes": [
{
"version": [
"v20.0.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/47339",
"description": "ICU requirement is removed."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`domain` {string}",
"name": "domain",
"type": "string"
}
]
}
],
"desc": "Returns the Unicode serialization of the domain
. If domain
is an invalid\ndomain, the empty string is returned.
It performs the inverse operation to url.domainToASCII()
.
import url from 'node:url';\n\nconsole.log(url.domainToUnicode('xn--espaol-zwa.com'));\n// Prints español.com\nconsole.log(url.domainToUnicode('xn--fiq228c.com'));\n// Prints 中文.com\nconsole.log(url.domainToUnicode('xn--iñvalid.com'));\n// Prints an empty string\n
\nconst url = require('node:url');\n\nconsole.log(url.domainToUnicode('xn--espaol-zwa.com'));\n// Prints español.com\nconsole.log(url.domainToUnicode('xn--fiq228c.com'));\n// Prints 中文.com\nconsole.log(url.domainToUnicode('xn--iñvalid.com'));\n// Prints an empty string\n
"
},
{
"textRaw": "`url.fileURLToPath(url)`",
"type": "method",
"name": "fileURLToPath",
"meta": {
"added": [
"v10.12.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string} The fully-resolved platform-specific Node.js file path.",
"name": "return",
"type": "string",
"desc": "The fully-resolved platform-specific Node.js file path."
},
"params": [
{
"textRaw": "`url` {URL | string} The file URL string or URL object to convert to a path.",
"name": "url",
"type": "URL | string",
"desc": "The file URL string or URL object to convert to a path."
}
]
}
],
"desc": "This function ensures the correct decodings of percent-encoded characters as\nwell as ensuring a cross-platform valid absolute path string.
\nimport { fileURLToPath } from 'node:url';\n\nconst __filename = fileURLToPath(import.meta.url);\n\nnew URL('file:///C:/path/').pathname; // Incorrect: /C:/path/\nfileURLToPath('file:///C:/path/'); // Correct: C:\\path\\ (Windows)\n\nnew URL('file://nas/foo.txt').pathname; // Incorrect: /foo.txt\nfileURLToPath('file://nas/foo.txt'); // Correct: \\\\nas\\foo.txt (Windows)\n\nnew URL('file:///你好.txt').pathname; // Incorrect: /%E4%BD%A0%E5%A5%BD.txt\nfileURLToPath('file:///你好.txt'); // Correct: /你好.txt (POSIX)\n\nnew URL('file:///hello world').pathname; // Incorrect: /hello%20world\nfileURLToPath('file:///hello world'); // Correct: /hello world (POSIX)\n
\nconst { fileURLToPath } = require('node:url');\nnew URL('file:///C:/path/').pathname; // Incorrect: /C:/path/\nfileURLToPath('file:///C:/path/'); // Correct: C:\\path\\ (Windows)\n\nnew URL('file://nas/foo.txt').pathname; // Incorrect: /foo.txt\nfileURLToPath('file://nas/foo.txt'); // Correct: \\\\nas\\foo.txt (Windows)\n\nnew URL('file:///你好.txt').pathname; // Incorrect: /%E4%BD%A0%E5%A5%BD.txt\nfileURLToPath('file:///你好.txt'); // Correct: /你好.txt (POSIX)\n\nnew URL('file:///hello world').pathname; // Incorrect: /hello%20world\nfileURLToPath('file:///hello world'); // Correct: /hello world (POSIX)\n
"
},
{
"textRaw": "`url.format(URL[, options])`",
"type": "method",
"name": "format",
"meta": {
"added": [
"v7.6.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`URL` {URL} A [WHATWG URL][] object",
"name": "URL",
"type": "URL",
"desc": "A [WHATWG URL][] object"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`auth` {boolean} `true` if the serialized URL string should include the username and password, `false` otherwise. **Default:** `true`.",
"name": "auth",
"type": "boolean",
"default": "`true`",
"desc": "`true` if the serialized URL string should include the username and password, `false` otherwise."
},
{
"textRaw": "`fragment` {boolean} `true` if the serialized URL string should include the fragment, `false` otherwise. **Default:** `true`.",
"name": "fragment",
"type": "boolean",
"default": "`true`",
"desc": "`true` if the serialized URL string should include the fragment, `false` otherwise."
},
{
"textRaw": "`search` {boolean} `true` if the serialized URL string should include the search query, `false` otherwise. **Default:** `true`.",
"name": "search",
"type": "boolean",
"default": "`true`",
"desc": "`true` if the serialized URL string should include the search query, `false` otherwise."
},
{
"textRaw": "`unicode` {boolean} `true` if Unicode characters appearing in the host component of the URL string should be encoded directly as opposed to being Punycode encoded. **Default:** `false`.",
"name": "unicode",
"type": "boolean",
"default": "`false`",
"desc": "`true` if Unicode characters appearing in the host component of the URL string should be encoded directly as opposed to being Punycode encoded."
}
]
}
]
}
],
"desc": "Returns a customizable serialization of a URL String
representation of a\nWHATWG URL object.
The URL object has both a toString()
method and href
property that return\nstring serializations of the URL. These are not, however, customizable in\nany way. The url.format(URL[, options])
method allows for basic customization\nof the output.
import url from 'node:url';\nconst myURL = new URL('https://a:b@測試?abc#foo');\n\nconsole.log(myURL.href);\n// Prints https://a:b@xn--g6w251d/?abc#foo\n\nconsole.log(myURL.toString());\n// Prints https://a:b@xn--g6w251d/?abc#foo\n\nconsole.log(url.format(myURL, { fragment: false, unicode: true, auth: false }));\n// Prints 'https://測試/?abc'\n
\nconst url = require('node:url');\nconst myURL = new URL('https://a:b@測試?abc#foo');\n\nconsole.log(myURL.href);\n// Prints https://a:b@xn--g6w251d/?abc#foo\n\nconsole.log(myURL.toString());\n// Prints https://a:b@xn--g6w251d/?abc#foo\n\nconsole.log(url.format(myURL, { fragment: false, unicode: true, auth: false }));\n// Prints 'https://測試/?abc'\n
"
},
{
"textRaw": "`url.pathToFileURL(path)`",
"type": "method",
"name": "pathToFileURL",
"meta": {
"added": [
"v10.12.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {URL} The file URL object.",
"name": "return",
"type": "URL",
"desc": "The file URL object."
},
"params": [
{
"textRaw": "`path` {string} The path to convert to a File URL.",
"name": "path",
"type": "string",
"desc": "The path to convert to a File URL."
}
]
}
],
"desc": "This function ensures that path
is resolved absolutely, and that the URL\ncontrol characters are correctly encoded when converting into a File URL.
import { pathToFileURL } from 'node:url';\n\nnew URL('/foo#1', 'file:'); // Incorrect: file:///foo#1\npathToFileURL('/foo#1'); // Correct: file:///foo%231 (POSIX)\n\nnew URL('/some/path%.c', 'file:'); // Incorrect: file:///some/path%.c\npathToFileURL('/some/path%.c'); // Correct: file:///some/path%25.c (POSIX)\n
\nconst { pathToFileURL } = require('node:url');\nnew URL(__filename); // Incorrect: throws (POSIX)\nnew URL(__filename); // Incorrect: C:\\... (Windows)\npathToFileURL(__filename); // Correct: file:///... (POSIX)\npathToFileURL(__filename); // Correct: file:///C:/... (Windows)\n\nnew URL('/foo#1', 'file:'); // Incorrect: file:///foo#1\npathToFileURL('/foo#1'); // Correct: file:///foo%231 (POSIX)\n\nnew URL('/some/path%.c', 'file:'); // Incorrect: file:///some/path%.c\npathToFileURL('/some/path%.c'); // Correct: file:///some/path%25.c (POSIX)\n
"
},
{
"textRaw": "`url.urlToHttpOptions(url)`",
"type": "method",
"name": "urlToHttpOptions",
"meta": {
"added": [
"v15.7.0",
"v14.18.0"
],
"changes": [
{
"version": [
"v19.9.0",
"v18.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/46989",
"description": "The returned object will also contain all the own enumerable properties of the `url` argument."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object} Options object",
"name": "return",
"type": "Object",
"desc": "Options object",
"options": [
{
"textRaw": "`protocol` {string} Protocol to use.",
"name": "protocol",
"type": "string",
"desc": "Protocol to use."
},
{
"textRaw": "`hostname` {string} A domain name or IP address of the server to issue the request to.",
"name": "hostname",
"type": "string",
"desc": "A domain name or IP address of the server to issue the request to."
},
{
"textRaw": "`hash` {string} The fragment portion of the URL.",
"name": "hash",
"type": "string",
"desc": "The fragment portion of the URL."
},
{
"textRaw": "`search` {string} The serialized query portion of the URL.",
"name": "search",
"type": "string",
"desc": "The serialized query portion of the URL."
},
{
"textRaw": "`pathname` {string} The path portion of the URL.",
"name": "pathname",
"type": "string",
"desc": "The path portion of the URL."
},
{
"textRaw": "`path` {string} Request path. Should include query string if any. E.G. `'/index.html?page=12'`. An exception is thrown when the request path contains illegal characters. Currently, only spaces are rejected but that may change in the future.",
"name": "path",
"type": "string",
"desc": "Request path. Should include query string if any. E.G. `'/index.html?page=12'`. An exception is thrown when the request path contains illegal characters. Currently, only spaces are rejected but that may change in the future."
},
{
"textRaw": "`href` {string} The serialized URL.",
"name": "href",
"type": "string",
"desc": "The serialized URL."
},
{
"textRaw": "`port` {number} Port of remote server.",
"name": "port",
"type": "number",
"desc": "Port of remote server."
},
{
"textRaw": "`auth` {string} Basic authentication i.e. `'user:password'` to compute an Authorization header.",
"name": "auth",
"type": "string",
"desc": "Basic authentication i.e. `'user:password'` to compute an Authorization header."
}
]
},
"params": [
{
"textRaw": "`url` {URL} The [WHATWG URL][] object to convert to an options object.",
"name": "url",
"type": "URL",
"desc": "The [WHATWG URL][] object to convert to an options object."
}
]
}
],
"desc": "This utility function converts a URL object into an ordinary options object as\nexpected by the http.request()
and https.request()
APIs.
import { urlToHttpOptions } from 'node:url';\nconst myURL = new URL('https://a:b@測試?abc#foo');\n\nconsole.log(urlToHttpOptions(myURL));\n/*\n{\n protocol: 'https:',\n hostname: 'xn--g6w251d',\n hash: '#foo',\n search: '?abc',\n pathname: '/',\n path: '/?abc',\n href: 'https://a:b@xn--g6w251d/?abc#foo',\n auth: 'a:b'\n}\n*/\n
\nconst { urlToHttpOptions } = require('node:url');\nconst myURL = new URL('https://a:b@測試?abc#foo');\n\nconsole.log(urlToHttpOptions(myURL));\n/*\n{\n protocol: 'https:',\n hostname: 'xn--g6w251d',\n hash: '#foo',\n search: '?abc',\n pathname: '/',\n path: '/?abc',\n href: 'https://a:b@xn--g6w251d/?abc#foo',\n auth: 'a:b'\n}\n*/\n
"
}
],
"type": "module",
"displayName": "The WHATWG URL API"
},
{
"textRaw": "Legacy URL API",
"name": "legacy_url_api",
"meta": {
"changes": [
{
"version": [
"v15.13.0",
"v14.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/37784",
"description": "Deprecation revoked. Status changed to \"Legacy\"."
},
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/22715",
"description": "This API is deprecated."
}
]
},
"stability": 3,
"stabilityText": "Legacy: Use the WHATWG URL API instead.",
"modules": [
{
"textRaw": "Legacy `urlObject`",
"name": "legacy_`urlobject`",
"meta": {
"changes": [
{
"version": [
"v15.13.0",
"v14.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/37784",
"description": "Deprecation revoked. Status changed to \"Legacy\"."
},
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/22715",
"description": "The Legacy URL API is deprecated. Use the WHATWG URL API."
}
]
},
"stability": 3,
"stabilityText": "Legacy: Use the WHATWG URL API instead.",
"desc": "The legacy urlObject
(require('node:url').Url
or\nimport { Url } from 'node:url'
) is\ncreated and returned by the url.parse()
function.
The auth
property is the username and password portion of the URL, also\nreferred to as userinfo. This string subset follows the protocol
and\ndouble slashes (if present) and precedes the host
component, delimited by @
.\nThe string is either the username, or it is the username and password separated\nby :
.
For example: 'user:pass'
.
The hash
property is the fragment identifier portion of the URL including the\nleading #
character.
For example: '#hash'
.
The host
property is the full lower-cased host portion of the URL, including\nthe port
if specified.
For example: 'sub.example.com:8080'
.
The hostname
property is the lower-cased host name portion of the host
\ncomponent without the port
included.
For example: 'sub.example.com'
.
The href
property is the full URL string that was parsed with both the\nprotocol
and host
components converted to lower-case.
For example: 'http://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash'
.
The path
property is a concatenation of the pathname
and search
\ncomponents.
For example: '/p/a/t/h?query=string'
.
No decoding of the path
is performed.
The pathname
property consists of the entire path section of the URL. This\nis everything following the host
(including the port
) and before the start\nof the query
or hash
components, delimited by either the ASCII question\nmark (?
) or hash (#
) characters.
For example: '/p/a/t/h'
.
No decoding of the path string is performed.
" }, { "textRaw": "`urlObject.port`", "name": "port", "desc": "The port
property is the numeric port portion of the host
component.
For example: '8080'
.
The protocol
property identifies the URL's lower-cased protocol scheme.
For example: 'http:'
.
The query
property is either the query string without the leading ASCII\nquestion mark (?
), or an object returned by the querystring
module's\nparse()
method. Whether the query
property is a string or object is\ndetermined by the parseQueryString
argument passed to url.parse()
.
For example: 'query=string'
or {'query': 'string'}
.
If returned as a string, no decoding of the query string is performed. If\nreturned as an object, both keys and values are decoded.
" }, { "textRaw": "`urlObject.search`", "name": "search", "desc": "The search
property consists of the entire \"query string\" portion of the\nURL, including the leading ASCII question mark (?
) character.
For example: '?query=string'
.
No decoding of the query string is performed.
" }, { "textRaw": "`urlObject.slashes`", "name": "slashes", "desc": "The slashes
property is a boolean
with a value of true
if two ASCII\nforward-slash characters (/
) are required following the colon in the\nprotocol
.
The url.format()
method returns a formatted URL string derived from\nurlObject
.
const url = require('node:url');\nurl.format({\n protocol: 'https',\n hostname: 'example.com',\n pathname: '/some/path',\n query: {\n page: 1,\n format: 'json',\n },\n});\n\n// => 'https://example.com/some/path?page=1&format=json'\n
\nIf urlObject
is not an object or a string, url.format()
will throw a\nTypeError
.
The formatting process operates as follows:
\nresult
is created.urlObject.protocol
is a string, it is appended as-is to result
.urlObject.protocol
is not undefined
and is not a string, an\nError
is thrown.urlObject.protocol
that do not end with an ASCII\ncolon (:
) character, the literal string :
will be appended to result
.//
\nwill be appended to result
:\nurlObject.slashes
property is true;urlObject.protocol
begins with http
, https
, ftp
, gopher
, or\nfile
;urlObject.auth
property is truthy, and either\nurlObject.host
or urlObject.hostname
are not undefined
, the value of\nurlObject.auth
will be coerced into a string and appended to result
\nfollowed by the literal string @
.urlObject.host
property is undefined
then:\nurlObject.hostname
is a string, it is appended to result
.urlObject.hostname
is not undefined
and is not a string,\nan Error
is thrown.urlObject.port
property value is truthy, and urlObject.hostname
\nis not undefined
:\n:
is appended to result
, andurlObject.port
is coerced to a string and appended to\nresult
.urlObject.host
property value is truthy, the value of\nurlObject.host
is coerced to a string and appended to result
.urlObject.pathname
property is a string that is not an empty string:\nurlObject.pathname
does not start with an ASCII forward slash\n(/
), then the literal string '/'
is appended to result
.urlObject.pathname
is appended to result
.urlObject.pathname
is not undefined
and is not a string, an\nError
is thrown.urlObject.search
property is undefined
and if the urlObject.query
\nproperty is an Object
, the literal string ?
is appended to result
\nfollowed by the output of calling the querystring
module's stringify()
\nmethod passing the value of urlObject.query
.urlObject.search
is a string:\nurlObject.search
does not start with the ASCII question\nmark (?
) character, the literal string ?
is appended to result
.urlObject.search
is appended to result
.urlObject.search
is not undefined
and is not a string, an\nError
is thrown.urlObject.hash
property is a string:\nurlObject.hash
does not start with the ASCII hash (#
)\ncharacter, the literal string #
is appended to result
.urlObject.hash
is appended to result
.urlObject.hash
property is not undefined
and is not a\nstring, an Error
is thrown.result
is returned.The url.parse()
method takes a URL string, parses it, and returns a URL\nobject.
A TypeError
is thrown if urlString
is not a string.
A URIError
is thrown if the auth
property is present but cannot be decoded.
url.parse()
uses a lenient, non-standard algorithm for parsing URL\nstrings. It is prone to security issues such as host name spoofing\nand incorrect handling of usernames and passwords. Do not use with untrusted\ninput. CVEs are not issued for url.parse()
vulnerabilities. Use the\nWHATWG URL API instead.
The url.resolve()
method resolves a target URL relative to a base URL in a\nmanner similar to that of a web browser resolving an anchor tag.
const url = require('node:url');\nurl.resolve('/one/two/three', 'four'); // '/one/two/four'\nurl.resolve('http://example.com/', '/one'); // 'http://example.com/one'\nurl.resolve('http://example.com/one', '/two'); // 'http://example.com/two'\n
\nTo achieve the same result using the WHATWG URL API:
\nfunction resolve(from, to) {\n const resolvedUrl = new URL(to, new URL(from, 'resolve://'));\n if (resolvedUrl.protocol === 'resolve:') {\n // `from` is a relative URL.\n const { pathname, search, hash } = resolvedUrl;\n return pathname + search + hash;\n }\n return resolvedUrl.toString();\n}\n\nresolve('/one/two/three', 'four'); // '/one/two/four'\nresolve('http://example.com/', '/one'); // 'http://example.com/one'\nresolve('http://example.com/one', '/two'); // 'http://example.com/two'\n
\n"
}
],
"type": "module",
"displayName": "Legacy URL API"
},
{
"textRaw": "Percent-encoding in URLs",
"name": "percent-encoding_in_urls",
"desc": "URLs are permitted to only contain a certain range of characters. Any character\nfalling outside of that range must be encoded. How such characters are encoded,\nand which characters to encode depends entirely on where the character is\nlocated within the structure of the URL.
", "modules": [ { "textRaw": "Legacy API", "name": "legacy_api", "desc": "Within the Legacy API, spaces (' '
) and the following characters will be\nautomatically escaped in the properties of URL objects:
< > \" ` \\r \\n \\t { } | \\ ^ '\n
\nFor example, the ASCII space character (' '
) is encoded as %20
. The ASCII\nforward slash (/
) character is encoded as %3C
.
The WHATWG URL Standard uses a more selective and fine grained approach to\nselecting encoded characters than that used by the Legacy API.
\nThe WHATWG algorithm defines four \"percent-encode sets\" that describe ranges\nof characters that must be percent-encoded:
\nThe C0 control percent-encode set includes code points in range U+0000 to\nU+001F (inclusive) and all code points greater than U+007E (~).
\nThe fragment percent-encode set includes the C0 control percent-encode set\nand code points U+0020 SPACE, U+0022 (\"), U+003C (<), U+003E (>),\nand U+0060 (`).
\nThe path percent-encode set includes the C0 control percent-encode set\nand code points U+0020 SPACE, U+0022 (\"), U+0023 (#), U+003C (<), U+003E (>),\nU+003F (?), U+0060 (`), U+007B ({), and U+007D (}).
\nThe userinfo encode set includes the path percent-encode set and code\npoints U+002F (/), U+003A (:), U+003B (;), U+003D (=), U+0040 (@),\nU+005B ([) to U+005E(^), and U+007C (|).
\nThe userinfo percent-encode set is used exclusively for username and\npasswords encoded within the URL. The path percent-encode set is used for the\npath of most URLs. The fragment percent-encode set is used for URL fragments.\nThe C0 control percent-encode set is used for host and path under certain\nspecific conditions, in addition to all other cases.
\nWhen non-ASCII characters appear within a host name, the host name is encoded\nusing the Punycode algorithm. Note, however, that a host name may contain\nboth Punycode encoded and percent-encoded characters:
\nconst myURL = new URL('https://%CF%80.example.com/foo');\nconsole.log(myURL.href);\n// Prints https://xn--1xa.example.com/foo\nconsole.log(myURL.origin);\n// Prints https://xn--1xa.example.com\n
",
"type": "module",
"displayName": "WHATWG API"
}
],
"type": "module",
"displayName": "Percent-encoding in URLs"
}
],
"type": "module",
"displayName": "URL",
"source": "doc/api/url.md"
},
{
"textRaw": "Util",
"name": "util",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/util.js
\nThe node:util
module supports the needs of Node.js internal APIs. Many of the\nutilities are useful for application and module developers as well. To access\nit:
const util = require('node:util');\n
",
"methods": [
{
"textRaw": "`util.callbackify(original)`",
"type": "method",
"name": "callbackify",
"meta": {
"added": [
"v8.2.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} a callback style function",
"name": "return",
"type": "Function",
"desc": "a callback style function"
},
"params": [
{
"textRaw": "`original` {Function} An `async` function",
"name": "original",
"type": "Function",
"desc": "An `async` function"
}
]
}
],
"desc": "Takes an async
function (or a function that returns a Promise
) and returns a\nfunction following the error-first callback style, i.e. taking\nan (err, value) => ...
callback as the last argument. In the callback, the\nfirst argument will be the rejection reason (or null
if the Promise
\nresolved), and the second argument will be the resolved value.
const util = require('node:util');\n\nasync function fn() {\n return 'hello world';\n}\nconst callbackFunction = util.callbackify(fn);\n\ncallbackFunction((err, ret) => {\n if (err) throw err;\n console.log(ret);\n});\n
\nWill print:
\nhello world\n
\nThe callback is executed asynchronously, and will have a limited stack trace.\nIf the callback throws, the process will emit an 'uncaughtException'
\nevent, and if not handled will exit.
Since null
has a special meaning as the first argument to a callback, if a\nwrapped function rejects a Promise
with a falsy value as a reason, the value\nis wrapped in an Error
with the original value stored in a field named\nreason
.
function fn() {\n return Promise.reject(null);\n}\nconst callbackFunction = util.callbackify(fn);\n\ncallbackFunction((err, ret) => {\n // When the Promise was rejected with `null` it is wrapped with an Error and\n // the original value is stored in `reason`.\n err && Object.hasOwn(err, 'reason') && err.reason === null; // true\n});\n
"
},
{
"textRaw": "`util.debuglog(section[, callback])`",
"type": "method",
"name": "debuglog",
"meta": {
"added": [
"v0.11.3"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} The logging function",
"name": "return",
"type": "Function",
"desc": "The logging function"
},
"params": [
{
"textRaw": "`section` {string} A string identifying the portion of the application for which the `debuglog` function is being created.",
"name": "section",
"type": "string",
"desc": "A string identifying the portion of the application for which the `debuglog` function is being created."
},
{
"textRaw": "`callback` {Function} A callback invoked the first time the logging function is called with a function argument that is a more optimized logging function.",
"name": "callback",
"type": "Function",
"desc": "A callback invoked the first time the logging function is called with a function argument that is a more optimized logging function."
}
]
}
],
"desc": "The util.debuglog()
method is used to create a function that conditionally\nwrites debug messages to stderr
based on the existence of the NODE_DEBUG
\nenvironment variable. If the section
name appears within the value of that\nenvironment variable, then the returned function operates similar to\nconsole.error()
. If not, then the returned function is a no-op.
const util = require('node:util');\nconst debuglog = util.debuglog('foo');\n\ndebuglog('hello from foo [%d]', 123);\n
\nIf this program is run with NODE_DEBUG=foo
in the environment, then\nit will output something like:
FOO 3245: hello from foo [123]\n
\nwhere 3245
is the process id. If it is not run with that\nenvironment variable set, then it will not print anything.
The section
supports wildcard also:
const util = require('node:util');\nconst debuglog = util.debuglog('foo-bar');\n\ndebuglog('hi there, it\\'s foo-bar [%d]', 2333);\n
\nif it is run with NODE_DEBUG=foo*
in the environment, then it will output\nsomething like:
FOO-BAR 3257: hi there, it's foo-bar [2333]\n
\nMultiple comma-separated section
names may be specified in the NODE_DEBUG
\nenvironment variable: NODE_DEBUG=fs,net,tls
.
The optional callback
argument can be used to replace the logging function\nwith a different function that doesn't have any initialization or\nunnecessary wrapping.
const util = require('node:util');\nlet debuglog = util.debuglog('internals', (debug) => {\n // Replace with a logging function that optimizes out\n // testing if the section is enabled\n debuglog = debug;\n});\n
",
"modules": [
{
"textRaw": "`debuglog().enabled`",
"name": "`debuglog().enabled`",
"meta": {
"added": [
"v14.9.0"
],
"changes": []
},
"desc": "The util.debuglog().enabled
getter is used to create a test that can be used\nin conditionals based on the existence of the NODE_DEBUG
environment variable.\nIf the section
name appears within the value of that environment variable,\nthen the returned value will be true
. If not, then the returned value will be\nfalse
.
const util = require('node:util');\nconst enabled = util.debuglog('foo').enabled;\nif (enabled) {\n console.log('hello from foo [%d]', 123);\n}\n
\nIf this program is run with NODE_DEBUG=foo
in the environment, then it will\noutput something like:
hello from foo [123]\n
",
"type": "module",
"displayName": "`debuglog().enabled`"
}
]
},
{
"textRaw": "`util.debug(section)`",
"type": "method",
"name": "debug",
"meta": {
"added": [
"v14.9.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Alias for util.debuglog
. Usage allows for readability of that doesn't imply\nlogging when only using util.debuglog().enabled
.
The util.deprecate()
method wraps fn
(which may be a function or class) in\nsuch a way that it is marked as deprecated.
const util = require('node:util');\n\nexports.obsoleteFunction = util.deprecate(() => {\n // Do something here.\n}, 'obsoleteFunction() is deprecated. Use newShinyFunction() instead.');\n
\nWhen called, util.deprecate()
will return a function that will emit a\nDeprecationWarning
using the 'warning'
event. The warning will\nbe emitted and printed to stderr
the first time the returned function is\ncalled. After the warning is emitted, the wrapped function is called without\nemitting a warning.
If the same optional code
is supplied in multiple calls to util.deprecate()
,\nthe warning will be emitted only once for that code
.
const util = require('node:util');\n\nconst fn1 = util.deprecate(someFunction, someMessage, 'DEP0001');\nconst fn2 = util.deprecate(someOtherFunction, someOtherMessage, 'DEP0001');\nfn1(); // Emits a deprecation warning with code DEP0001\nfn2(); // Does not emit a deprecation warning because it has the same code\n
\nIf either the --no-deprecation
or --no-warnings
command-line flags are\nused, or if the process.noDeprecation
property is set to true
prior to\nthe first deprecation warning, the util.deprecate()
method does nothing.
If the --trace-deprecation
or --trace-warnings
command-line flags are set,\nor the process.traceDeprecation
property is set to true
, a warning and a\nstack trace are printed to stderr
the first time the deprecated function is\ncalled.
If the --throw-deprecation
command-line flag is set, or the\nprocess.throwDeprecation
property is set to true
, then an exception will be\nthrown when the deprecated function is called.
The --throw-deprecation
command-line flag and process.throwDeprecation
\nproperty take precedence over --trace-deprecation
and\nprocess.traceDeprecation
.
The util.format()
method returns a formatted string using the first argument\nas a printf
-like format string which can contain zero or more format\nspecifiers. Each specifier is replaced with the converted value from the\ncorresponding argument. Supported specifiers are:
%s
: String
will be used to convert all values except BigInt
, Object
\nand -0
. BigInt
values will be represented with an n
and Objects that\nhave no user defined toString
function are inspected using util.inspect()
\nwith options { depth: 0, colors: false, compact: 3 }
.%d
: Number
will be used to convert all values except BigInt
and\nSymbol
.%i
: parseInt(value, 10)
is used for all values except BigInt
and\nSymbol
.%f
: parseFloat(value)
is used for all values expect Symbol
.%j
: JSON. Replaced with the string '[Circular]'
if the argument contains\ncircular references.%o
: Object
. A string representation of an object with generic JavaScript\nobject formatting. Similar to util.inspect()
with options\n{ showHidden: true, showProxy: true }
. This will show the full object\nincluding non-enumerable properties and proxies.%O
: Object
. A string representation of an object with generic JavaScript\nobject formatting. Similar to util.inspect()
without options. This will show\nthe full object not including non-enumerable properties and proxies.%c
: CSS
. This specifier is ignored and will skip any CSS passed in.%%
: single percent sign ('%'
). This does not consume an argument.If a specifier does not have a corresponding argument, it is not replaced:
\nutil.format('%s:%s', 'foo');\n// Returns: 'foo:%s'\n
\nValues that are not part of the format string are formatted using\nutil.inspect()
if their type is not string
.
If there are more arguments passed to the util.format()
method than the\nnumber of specifiers, the extra arguments are concatenated to the returned\nstring, separated by spaces:
util.format('%s:%s', 'foo', 'bar', 'baz');\n// Returns: 'foo:bar baz'\n
\nIf the first argument does not contain a valid format specifier, util.format()
\nreturns a string that is the concatenation of all arguments separated by spaces:
util.format(1, 2, 3);\n// Returns: '1 2 3'\n
\nIf only one argument is passed to util.format()
, it is returned as it is\nwithout any formatting:
util.format('%% %s');\n// Returns: '%% %s'\n
\nutil.format()
is a synchronous method that is intended as a debugging tool.\nSome input values can have a significant performance overhead that can block the\nevent loop. Use this function with care and never in a hot code path.
This function is identical to util.format()
, except in that it takes\nan inspectOptions
argument which specifies options that are passed along to\nutil.inspect()
.
util.formatWithOptions({ colors: true }, 'See object %O', { foo: 42 });\n// Returns 'See object { foo: 42 }', where `42` is colored as a number\n// when printed to a terminal.\n
"
},
{
"textRaw": "`util.getSystemErrorName(err)`",
"type": "method",
"name": "getSystemErrorName",
"meta": {
"added": [
"v9.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`err` {number}",
"name": "err",
"type": "number"
}
]
}
],
"desc": "Returns the string name for a numeric error code that comes from a Node.js API.\nThe mapping between error codes and error names is platform-dependent.\nSee Common System Errors for the names of common errors.
\nfs.access('file/that/does/not/exist', (err) => {\n const name = util.getSystemErrorName(err.errno);\n console.error(name); // ENOENT\n});\n
"
},
{
"textRaw": "`util.getSystemErrorMap()`",
"type": "method",
"name": "getSystemErrorMap",
"meta": {
"added": [
"v16.0.0",
"v14.17.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Map}",
"name": "return",
"type": "Map"
},
"params": []
}
],
"desc": "Returns a Map of all system error codes available from the Node.js API.\nThe mapping between error codes and error names is platform-dependent.\nSee Common System Errors for the names of common errors.
\nfs.access('file/that/does/not/exist', (err) => {\n const errorMap = util.getSystemErrorMap();\n const name = errorMap.get(err.errno);\n console.error(name); // ENOENT\n});\n
"
},
{
"textRaw": "`util.inherits(constructor, superConstructor)`",
"type": "method",
"name": "inherits",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"version": "v5.0.0",
"pr-url": "https://github.com/nodejs/node/pull/3455",
"description": "The `constructor` parameter can refer to an ES6 class now."
}
]
},
"stability": 3,
"stabilityText": "Legacy: Use ES2015 class syntax and `extends` keyword instead.",
"signatures": [
{
"params": [
{
"textRaw": "`constructor` {Function}",
"name": "constructor",
"type": "Function"
},
{
"textRaw": "`superConstructor` {Function}",
"name": "superConstructor",
"type": "Function"
}
]
}
],
"desc": "Usage of util.inherits()
is discouraged. Please use the ES6 class
and\nextends
keywords to get language level inheritance support. Also note\nthat the two styles are semantically incompatible.
Inherit the prototype methods from one constructor into another. The\nprototype of constructor
will be set to a new object created from\nsuperConstructor
.
This mainly adds some input validation on top of\nObject.setPrototypeOf(constructor.prototype, superConstructor.prototype)
.\nAs an additional convenience, superConstructor
will be accessible\nthrough the constructor.super_
property.
const util = require('node:util');\nconst EventEmitter = require('node:events');\n\nfunction MyStream() {\n EventEmitter.call(this);\n}\n\nutil.inherits(MyStream, EventEmitter);\n\nMyStream.prototype.write = function(data) {\n this.emit('data', data);\n};\n\nconst stream = new MyStream();\n\nconsole.log(stream instanceof EventEmitter); // true\nconsole.log(MyStream.super_ === EventEmitter); // true\n\nstream.on('data', (data) => {\n console.log(`Received data: \"${data}\"`);\n});\nstream.write('It works!'); // Received data: \"It works!\"\n
\nES6 example using class
and extends
:
const EventEmitter = require('node:events');\n\nclass MyStream extends EventEmitter {\n write(data) {\n this.emit('data', data);\n }\n}\n\nconst stream = new MyStream();\n\nstream.on('data', (data) => {\n console.log(`Received data: \"${data}\"`);\n});\nstream.write('With ES6');\n
"
},
{
"textRaw": "`util.inspect(object[, options])`",
"type": "method",
"name": "inspect",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"version": [
"v17.3.0",
"v16.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/41003",
"description": "The `numericSeparator` option is supported now."
},
{
"version": "v16.18.0",
"pr-url": "https://github.com/nodejs/node/pull/43576",
"description": "add support for `maxArrayLength` when inspecting `Set` and `Map`."
},
{
"version": [
"v14.6.0",
"v12.19.0"
],
"pr-url": "https://github.com/nodejs/node/pull/33690",
"description": "If `object` is from a different `vm.Context` now, a custom inspection function on it will not receive context-specific arguments anymore."
},
{
"version": [
"v13.13.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32392",
"description": "The `maxStringLength` option is supported now."
},
{
"version": [
"v13.5.0",
"v12.16.0"
],
"pr-url": "https://github.com/nodejs/node/pull/30768",
"description": "User defined prototype properties are inspected in case `showHidden` is `true`."
},
{
"version": "v13.0.0",
"pr-url": "https://github.com/nodejs/node/pull/27685",
"description": "Circular references now include a marker to the reference."
},
{
"version": "v12.0.0",
"pr-url": "https://github.com/nodejs/node/pull/27109",
"description": "The `compact` options default is changed to `3` and the `breakLength` options default is changed to `80`."
},
{
"version": "v12.0.0",
"pr-url": "https://github.com/nodejs/node/pull/24971",
"description": "Internal properties no longer appear in the context argument of a custom inspection function."
},
{
"version": "v11.11.0",
"pr-url": "https://github.com/nodejs/node/pull/26269",
"description": "The `compact` option accepts numbers for a new output mode."
},
{
"version": "v11.7.0",
"pr-url": "https://github.com/nodejs/node/pull/25006",
"description": "ArrayBuffers now also show their binary contents."
},
{
"version": "v11.5.0",
"pr-url": "https://github.com/nodejs/node/pull/24852",
"description": "The `getters` option is supported now."
},
{
"version": "v11.4.0",
"pr-url": "https://github.com/nodejs/node/pull/24326",
"description": "The `depth` default changed back to `2`."
},
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/22846",
"description": "The `depth` default changed to `20`."
},
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/22756",
"description": "The inspection output is now limited to about 128 MiB. Data above that size will not be fully inspected."
},
{
"version": "v10.12.0",
"pr-url": "https://github.com/nodejs/node/pull/22788",
"description": "The `sorted` option is supported now."
},
{
"version": "v10.6.0",
"pr-url": "https://github.com/nodejs/node/pull/20725",
"description": "Inspecting linked lists and similar objects is now possible up to the maximum call stack size."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/19259",
"description": "The `WeakMap` and `WeakSet` entries can now be inspected as well."
},
{
"version": "v9.9.0",
"pr-url": "https://github.com/nodejs/node/pull/17576",
"description": "The `compact` option is supported now."
},
{
"version": "v6.6.0",
"pr-url": "https://github.com/nodejs/node/pull/8174",
"description": "Custom inspection functions can now return `this`."
},
{
"version": "v6.3.0",
"pr-url": "https://github.com/nodejs/node/pull/7499",
"description": "The `breakLength` option is supported now."
},
{
"version": "v6.1.0",
"pr-url": "https://github.com/nodejs/node/pull/6334",
"description": "The `maxArrayLength` option is supported now; in particular, long arrays are truncated by default."
},
{
"version": "v6.1.0",
"pr-url": "https://github.com/nodejs/node/pull/6465",
"description": "The `showProxy` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string} The representation of `object`.",
"name": "return",
"type": "string",
"desc": "The representation of `object`."
},
"params": [
{
"textRaw": "`object` {any} Any JavaScript primitive or `Object`.",
"name": "object",
"type": "any",
"desc": "Any JavaScript primitive or `Object`."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`showHidden` {boolean} If `true`, `object`'s non-enumerable symbols and properties are included in the formatted result. [`WeakMap`][] and [`WeakSet`][] entries are also included as well as user defined prototype properties (excluding method properties). **Default:** `false`.",
"name": "showHidden",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, `object`'s non-enumerable symbols and properties are included in the formatted result. [`WeakMap`][] and [`WeakSet`][] entries are also included as well as user defined prototype properties (excluding method properties)."
},
{
"textRaw": "`depth` {number} Specifies the number of times to recurse while formatting `object`. This is useful for inspecting large objects. To recurse up to the maximum call stack size pass `Infinity` or `null`. **Default:** `2`.",
"name": "depth",
"type": "number",
"default": "`2`",
"desc": "Specifies the number of times to recurse while formatting `object`. This is useful for inspecting large objects. To recurse up to the maximum call stack size pass `Infinity` or `null`."
},
{
"textRaw": "`colors` {boolean} If `true`, the output is styled with ANSI color codes. Colors are customizable. See [Customizing `util.inspect` colors][]. **Default:** `false`.",
"name": "colors",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, the output is styled with ANSI color codes. Colors are customizable. See [Customizing `util.inspect` colors][]."
},
{
"textRaw": "`customInspect` {boolean} If `false`, `[util.inspect.custom](depth, opts, inspect)` functions are not invoked. **Default:** `true`.",
"name": "customInspect",
"type": "boolean",
"default": "`true`",
"desc": "If `false`, `[util.inspect.custom](depth, opts, inspect)` functions are not invoked."
},
{
"textRaw": "`showProxy` {boolean} If `true`, `Proxy` inspection includes the [`target` and `handler`][] objects. **Default:** `false`.",
"name": "showProxy",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, `Proxy` inspection includes the [`target` and `handler`][] objects."
},
{
"textRaw": "`maxArrayLength` {integer} Specifies the maximum number of `Array`, [`TypedArray`][], [`Map`][], [`Set`][], [`WeakMap`][], and [`WeakSet`][] elements to include when formatting. Set to `null` or `Infinity` to show all elements. Set to `0` or negative to show no elements. **Default:** `100`.",
"name": "maxArrayLength",
"type": "integer",
"default": "`100`",
"desc": "Specifies the maximum number of `Array`, [`TypedArray`][], [`Map`][], [`Set`][], [`WeakMap`][], and [`WeakSet`][] elements to include when formatting. Set to `null` or `Infinity` to show all elements. Set to `0` or negative to show no elements."
},
{
"textRaw": "`maxStringLength` {integer} Specifies the maximum number of characters to include when formatting. Set to `null` or `Infinity` to show all elements. Set to `0` or negative to show no characters. **Default:** `10000`.",
"name": "maxStringLength",
"type": "integer",
"default": "`10000`",
"desc": "Specifies the maximum number of characters to include when formatting. Set to `null` or `Infinity` to show all elements. Set to `0` or negative to show no characters."
},
{
"textRaw": "`breakLength` {integer} The length at which input values are split across multiple lines. Set to `Infinity` to format the input as a single line (in combination with `compact` set to `true` or any number >= `1`). **Default:** `80`.",
"name": "breakLength",
"type": "integer",
"default": "`80`",
"desc": "The length at which input values are split across multiple lines. Set to `Infinity` to format the input as a single line (in combination with `compact` set to `true` or any number >= `1`)."
},
{
"textRaw": "`compact` {boolean|integer} Setting this to `false` causes each object key to be displayed on a new line. It will break on new lines in text that is longer than `breakLength`. If set to a number, the most `n` inner elements are united on a single line as long as all properties fit into `breakLength`. Short array elements are also grouped together. For more information, see the example below. **Default:** `3`.",
"name": "compact",
"type": "boolean|integer",
"default": "`3`",
"desc": "Setting this to `false` causes each object key to be displayed on a new line. It will break on new lines in text that is longer than `breakLength`. If set to a number, the most `n` inner elements are united on a single line as long as all properties fit into `breakLength`. Short array elements are also grouped together. For more information, see the example below."
},
{
"textRaw": "`sorted` {boolean|Function} If set to `true` or a function, all properties of an object, and `Set` and `Map` entries are sorted in the resulting string. If set to `true` the [default sort][] is used. If set to a function, it is used as a [compare function][].",
"name": "sorted",
"type": "boolean|Function",
"desc": "If set to `true` or a function, all properties of an object, and `Set` and `Map` entries are sorted in the resulting string. If set to `true` the [default sort][] is used. If set to a function, it is used as a [compare function][]."
},
{
"textRaw": "`getters` {boolean|string} If set to `true`, getters are inspected. If set to `'get'`, only getters without a corresponding setter are inspected. If set to `'set'`, only getters with a corresponding setter are inspected. This might cause side effects depending on the getter function. **Default:** `false`.",
"name": "getters",
"type": "boolean|string",
"default": "`false`",
"desc": "If set to `true`, getters are inspected. If set to `'get'`, only getters without a corresponding setter are inspected. If set to `'set'`, only getters with a corresponding setter are inspected. This might cause side effects depending on the getter function."
},
{
"textRaw": "`numericSeparator` {boolean} If set to `true`, an underscore is used to separate every three digits in all bigints and numbers. **Default:** `false`.",
"name": "numericSeparator",
"type": "boolean",
"default": "`false`",
"desc": "If set to `true`, an underscore is used to separate every three digits in all bigints and numbers."
}
]
}
]
}
],
"desc": "The util.inspect()
method returns a string representation of object
that is\nintended for debugging. The output of util.inspect
may change at any time\nand should not be depended upon programmatically. Additional options
may be\npassed that alter the result.\nutil.inspect()
will use the constructor's name and/or @@toStringTag
to make\nan identifiable tag for an inspected value.
class Foo {\n get [Symbol.toStringTag]() {\n return 'bar';\n }\n}\n\nclass Bar {}\n\nconst baz = Object.create(null, { [Symbol.toStringTag]: { value: 'foo' } });\n\nutil.inspect(new Foo()); // 'Foo [bar] {}'\nutil.inspect(new Bar()); // 'Bar {}'\nutil.inspect(baz); // '[foo] {}'\n
\nCircular references point to their anchor by using a reference index:
\nconst { inspect } = require('node:util');\n\nconst obj = {};\nobj.a = [obj];\nobj.b = {};\nobj.b.inner = obj.b;\nobj.b.obj = obj;\n\nconsole.log(inspect(obj));\n// <ref *1> {\n// a: [ [Circular *1] ],\n// b: <ref *2> { inner: [Circular *2], obj: [Circular *1] }\n// }\n
\nThe following example inspects all properties of the util
object:
const util = require('node:util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));\n
\nThe following example highlights the effect of the compact
option:
const util = require('node:util');\n\nconst o = {\n a: [1, 2, [[\n 'Lorem ipsum dolor sit amet,\\nconsectetur adipiscing elit, sed do ' +\n 'eiusmod \\ntempor incididunt ut labore et dolore magna aliqua.',\n 'test',\n 'foo']], 4],\n b: new Map([['za', 1], ['zb', 'test']]),\n};\nconsole.log(util.inspect(o, { compact: true, depth: 5, breakLength: 80 }));\n\n// { a:\n// [ 1,\n// 2,\n// [ [ 'Lorem ipsum dolor sit amet,\\nconsectetur [...]', // A long line\n// 'test',\n// 'foo' ] ],\n// 4 ],\n// b: Map(2) { 'za' => 1, 'zb' => 'test' } }\n\n// Setting `compact` to false or an integer creates more reader friendly output.\nconsole.log(util.inspect(o, { compact: false, depth: 5, breakLength: 80 }));\n\n// {\n// a: [\n// 1,\n// 2,\n// [\n// [\n// 'Lorem ipsum dolor sit amet,\\n' +\n// 'consectetur adipiscing elit, sed do eiusmod \\n' +\n// 'tempor incididunt ut labore et dolore magna aliqua.',\n// 'test',\n// 'foo'\n// ]\n// ],\n// 4\n// ],\n// b: Map(2) {\n// 'za' => 1,\n// 'zb' => 'test'\n// }\n// }\n\n// Setting `breakLength` to e.g. 150 will print the \"Lorem ipsum\" text in a\n// single line.\n
\nThe showHidden
option allows WeakMap
and WeakSet
entries to be\ninspected. If there are more entries than maxArrayLength
, there is no\nguarantee which entries are displayed. That means retrieving the same\nWeakSet
entries twice may result in different output. Furthermore, entries\nwith no remaining strong references may be garbage collected at any time.
const { inspect } = require('node:util');\n\nconst obj = { a: 1 };\nconst obj2 = { b: 2 };\nconst weakSet = new WeakSet([obj, obj2]);\n\nconsole.log(inspect(weakSet, { showHidden: true }));\n// WeakSet { { a: 1 }, { b: 2 } }\n
\nThe sorted
option ensures that an object's property insertion order does not\nimpact the result of util.inspect()
.
const { inspect } = require('node:util');\nconst assert = require('node:assert');\n\nconst o1 = {\n b: [2, 3, 1],\n a: '`a` comes before `b`',\n c: new Set([2, 3, 1]),\n};\nconsole.log(inspect(o1, { sorted: true }));\n// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set(3) { 1, 2, 3 } }\nconsole.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));\n// { c: Set(3) { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }\n\nconst o2 = {\n c: new Set([2, 1, 3]),\n a: '`a` comes before `b`',\n b: [2, 3, 1],\n};\nassert.strict.equal(\n inspect(o1, { sorted: true }),\n inspect(o2, { sorted: true }),\n);\n
\nThe numericSeparator
option adds an underscore every three digits to all\nnumbers.
const { inspect } = require('node:util');\n\nconst thousand = 1_000;\nconst million = 1_000_000;\nconst bigNumber = 123_456_789n;\nconst bigDecimal = 1_234.123_45;\n\nconsole.log(inspect(thousand, { numericSeparator: true }));\n// 1_000\nconsole.log(inspect(million, { numericSeparator: true }));\n// 1_000_000\nconsole.log(inspect(bigNumber, { numericSeparator: true }));\n// 123_456_789n\nconsole.log(inspect(bigDecimal, { numericSeparator: true }));\n// 1_234.123_45\n
\nutil.inspect()
is a synchronous method intended for debugging. Its maximum\noutput length is approximately 128 MiB. Inputs that result in longer output will\nbe truncated.
The util.inspect()
method returns a string representation of object
that is\nintended for debugging. The output of util.inspect
may change at any time\nand should not be depended upon programmatically. Additional options
may be\npassed that alter the result.\nutil.inspect()
will use the constructor's name and/or @@toStringTag
to make\nan identifiable tag for an inspected value.
class Foo {\n get [Symbol.toStringTag]() {\n return 'bar';\n }\n}\n\nclass Bar {}\n\nconst baz = Object.create(null, { [Symbol.toStringTag]: { value: 'foo' } });\n\nutil.inspect(new Foo()); // 'Foo [bar] {}'\nutil.inspect(new Bar()); // 'Bar {}'\nutil.inspect(baz); // '[foo] {}'\n
\nCircular references point to their anchor by using a reference index:
\nconst { inspect } = require('node:util');\n\nconst obj = {};\nobj.a = [obj];\nobj.b = {};\nobj.b.inner = obj.b;\nobj.b.obj = obj;\n\nconsole.log(inspect(obj));\n// <ref *1> {\n// a: [ [Circular *1] ],\n// b: <ref *2> { inner: [Circular *2], obj: [Circular *1] }\n// }\n
\nThe following example inspects all properties of the util
object:
const util = require('node:util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));\n
\nThe following example highlights the effect of the compact
option:
const util = require('node:util');\n\nconst o = {\n a: [1, 2, [[\n 'Lorem ipsum dolor sit amet,\\nconsectetur adipiscing elit, sed do ' +\n 'eiusmod \\ntempor incididunt ut labore et dolore magna aliqua.',\n 'test',\n 'foo']], 4],\n b: new Map([['za', 1], ['zb', 'test']]),\n};\nconsole.log(util.inspect(o, { compact: true, depth: 5, breakLength: 80 }));\n\n// { a:\n// [ 1,\n// 2,\n// [ [ 'Lorem ipsum dolor sit amet,\\nconsectetur [...]', // A long line\n// 'test',\n// 'foo' ] ],\n// 4 ],\n// b: Map(2) { 'za' => 1, 'zb' => 'test' } }\n\n// Setting `compact` to false or an integer creates more reader friendly output.\nconsole.log(util.inspect(o, { compact: false, depth: 5, breakLength: 80 }));\n\n// {\n// a: [\n// 1,\n// 2,\n// [\n// [\n// 'Lorem ipsum dolor sit amet,\\n' +\n// 'consectetur adipiscing elit, sed do eiusmod \\n' +\n// 'tempor incididunt ut labore et dolore magna aliqua.',\n// 'test',\n// 'foo'\n// ]\n// ],\n// 4\n// ],\n// b: Map(2) {\n// 'za' => 1,\n// 'zb' => 'test'\n// }\n// }\n\n// Setting `breakLength` to e.g. 150 will print the \"Lorem ipsum\" text in a\n// single line.\n
\nThe showHidden
option allows WeakMap
and WeakSet
entries to be\ninspected. If there are more entries than maxArrayLength
, there is no\nguarantee which entries are displayed. That means retrieving the same\nWeakSet
entries twice may result in different output. Furthermore, entries\nwith no remaining strong references may be garbage collected at any time.
const { inspect } = require('node:util');\n\nconst obj = { a: 1 };\nconst obj2 = { b: 2 };\nconst weakSet = new WeakSet([obj, obj2]);\n\nconsole.log(inspect(weakSet, { showHidden: true }));\n// WeakSet { { a: 1 }, { b: 2 } }\n
\nThe sorted
option ensures that an object's property insertion order does not\nimpact the result of util.inspect()
.
const { inspect } = require('node:util');\nconst assert = require('node:assert');\n\nconst o1 = {\n b: [2, 3, 1],\n a: '`a` comes before `b`',\n c: new Set([2, 3, 1]),\n};\nconsole.log(inspect(o1, { sorted: true }));\n// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set(3) { 1, 2, 3 } }\nconsole.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));\n// { c: Set(3) { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }\n\nconst o2 = {\n c: new Set([2, 1, 3]),\n a: '`a` comes before `b`',\n b: [2, 3, 1],\n};\nassert.strict.equal(\n inspect(o1, { sorted: true }),\n inspect(o2, { sorted: true }),\n);\n
\nThe numericSeparator
option adds an underscore every three digits to all\nnumbers.
const { inspect } = require('node:util');\n\nconst thousand = 1_000;\nconst million = 1_000_000;\nconst bigNumber = 123_456_789n;\nconst bigDecimal = 1_234.123_45;\n\nconsole.log(inspect(thousand, { numericSeparator: true }));\n// 1_000\nconsole.log(inspect(million, { numericSeparator: true }));\n// 1_000_000\nconsole.log(inspect(bigNumber, { numericSeparator: true }));\n// 123_456_789n\nconsole.log(inspect(bigDecimal, { numericSeparator: true }));\n// 1_234.123_45\n
\nutil.inspect()
is a synchronous method intended for debugging. Its maximum\noutput length is approximately 128 MiB. Inputs that result in longer output will\nbe truncated.
Color output (if enabled) of util.inspect
is customizable globally\nvia the util.inspect.styles
and util.inspect.colors
properties.
util.inspect.styles
is a map associating a style name to a color from\nutil.inspect.colors
.
The default styles and associated colors are:
\nbigint
: yellow
boolean
: yellow
date
: magenta
module
: underline
name
: (no styling)null
: bold
number
: yellow
regexp
: red
special
: cyan
(e.g., Proxies
)string
: green
symbol
: green
undefined
: grey
Color styling uses ANSI control codes that may not be supported on all\nterminals. To verify color support use tty.hasColors()
.
Predefined control codes are listed below (grouped as \"Modifiers\", \"Foreground\ncolors\", and \"Background colors\").
", "miscs": [ { "textRaw": "Modifiers", "name": "modifiers", "desc": "Modifier support varies throughout different terminals. They will mostly be\nignored, if not supported.
\nreset
- Resets all (color) modifiers to their defaultsstrikeThrough
, crossedout
, crossedOut
)hidden
- Prints the text, but makes it invisible (Alias: conceal)faint
)swapcolors
, swapColors
)doubleUnderline
)black
red
green
yellow
blue
magenta
cyan
white
gray
(alias: grey
, blackBright
)redBright
greenBright
yellowBright
blueBright
magentaBright
cyanBright
whiteBright
bgBlack
bgRed
bgGreen
bgYellow
bgBlue
bgMagenta
bgCyan
bgWhite
bgGray
(alias: bgGrey
, bgBlackBright
)bgRedBright
bgGreenBright
bgYellowBright
bgBlueBright
bgMagentaBright
bgCyanBright
bgWhiteBright
Objects may also define their own\n[util.inspect.custom](depth, opts, inspect)
function,\nwhich util.inspect()
will invoke and use the result of when inspecting\nthe object.
const util = require('node:util');\n\nclass Box {\n constructor(value) {\n this.value = value;\n }\n\n [util.inspect.custom](depth, options, inspect) {\n if (depth < 0) {\n return options.stylize('[Box]', 'special');\n }\n\n const newOptions = Object.assign({}, options, {\n depth: options.depth === null ? null : options.depth - 1,\n });\n\n // Five space padding because that's the size of \"Box< \".\n const padding = ' '.repeat(5);\n const inner = inspect(this.value, newOptions)\n .replace(/\\n/g, `\\n${padding}`);\n return `${options.stylize('Box', 'special')}< ${inner} >`;\n }\n}\n\nconst box = new Box(true);\n\nutil.inspect(box);\n// Returns: \"Box< true >\"\n
\nCustom [util.inspect.custom](depth, opts, inspect)
functions typically return\na string but may return a value of any type that will be formatted accordingly\nby util.inspect()
.
const util = require('node:util');\n\nconst obj = { foo: 'this will not show up in the inspect() output' };\nobj[util.inspect.custom] = (depth) => {\n return { bar: 'baz' };\n};\n\nutil.inspect(obj);\n// Returns: \"{ bar: 'baz' }\"\n
"
}
],
"properties": [
{
"textRaw": "`custom` {symbol} that can be used to declare custom inspect functions.",
"type": "symbol",
"name": "custom",
"meta": {
"added": [
"v6.6.0"
],
"changes": [
{
"version": "v10.12.0",
"pr-url": "https://github.com/nodejs/node/pull/20857",
"description": "This is now defined as a shared symbol."
}
]
},
"desc": "In addition to being accessible through util.inspect.custom
, this\nsymbol is registered globally and can be\naccessed in any environment as Symbol.for('nodejs.util.inspect.custom')
.
Using this allows code to be written in a portable fashion, so that the custom\ninspect function is used in an Node.js environment and ignored in the browser.\nThe util.inspect()
function itself is passed as third argument to the custom\ninspect function to allow further portability.
const customInspectSymbol = Symbol.for('nodejs.util.inspect.custom');\n\nclass Password {\n constructor(value) {\n this.value = value;\n }\n\n toString() {\n return 'xxxxxxxx';\n }\n\n [customInspectSymbol](depth, inspectOptions, inspect) {\n return `Password <${this.toString()}>`;\n }\n}\n\nconst password = new Password('r0sebud');\nconsole.log(password);\n// Prints Password <xxxxxxxx>\n
\nSee Custom inspection functions on Objects for more details.
", "shortDesc": "that can be used to declare custom inspect functions." }, { "textRaw": "`util.inspect.defaultOptions`", "name": "defaultOptions", "meta": { "added": [ "v6.4.0" ], "changes": [] }, "desc": "The defaultOptions
value allows customization of the default options used by\nutil.inspect
. This is useful for functions like console.log
or\nutil.format
which implicitly call into util.inspect
. It shall be set to an\nobject containing one or more valid util.inspect()
options. Setting\noption properties directly is also supported.
const util = require('node:util');\nconst arr = Array(101).fill(0);\n\nconsole.log(arr); // Logs the truncated array\nutil.inspect.defaultOptions.maxArrayLength = null;\nconsole.log(arr); // logs the full array\n
"
}
]
},
{
"textRaw": "`util.isDeepStrictEqual(val1, val2)`",
"type": "method",
"name": "isDeepStrictEqual",
"meta": {
"added": [
"v9.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`val1` {any}",
"name": "val1",
"type": "any"
},
{
"textRaw": "`val2` {any}",
"name": "val2",
"type": "any"
}
]
}
],
"desc": "Returns true
if there is deep strict equality between val1
and val2
.\nOtherwise, returns false
.
See assert.deepStrictEqual()
for more information about deep strict\nequality.
Provides a higher level API for command-line argument parsing than interacting\nwith process.argv
directly. Takes a specification for the expected arguments\nand returns a structured object with the parsed options and positionals.
import { parseArgs } from 'node:util';\nconst args = ['-f', '--bar', 'b'];\nconst options = {\n foo: {\n type: 'boolean',\n short: 'f',\n },\n bar: {\n type: 'string',\n },\n};\nconst {\n values,\n positionals,\n} = parseArgs({ args, options });\nconsole.log(values, positionals);\n// Prints: [Object: null prototype] { foo: true, bar: 'b' } []\n
\nconst { parseArgs } = require('node:util');\nconst args = ['-f', '--bar', 'b'];\nconst options = {\n foo: {\n type: 'boolean',\n short: 'f',\n },\n bar: {\n type: 'string',\n },\n};\nconst {\n values,\n positionals,\n} = parseArgs({ args, options });\nconsole.log(values, positionals);\n// Prints: [Object: null prototype] { foo: true, bar: 'b' } []\n
",
"modules": [
{
"textRaw": "`parseArgs` `tokens`",
"name": "`parseargs`_`tokens`",
"desc": "Detailed parse information is available for adding custom behaviors by\nspecifying tokens: true
in the configuration.\nThe returned tokens have properties describing:
name
<string> Long name of option.rawName
<string> How option used in args, like -f
of --foo
.value
<string> | <undefined> Option value specified in args.\nUndefined for boolean options.inlineValue
<boolean> | <undefined> Whether option value specified inline,\nlike --foo=bar
.value
<string> The value of the positional argument in args (i.e. args[index]
).The returned tokens are in the order encountered in the input args. Options\nthat appear more than once in args produce a token for each use. Short option\ngroups like -xy
expand to a token for each option. So -xxx
produces\nthree tokens.
For example to use the returned tokens to add support for a negated option\nlike --no-color
, the tokens can be reprocessed to change the value stored\nfor the negated option.
import { parseArgs } from 'node:util';\n\nconst options = {\n 'color': { type: 'boolean' },\n 'no-color': { type: 'boolean' },\n 'logfile': { type: 'string' },\n 'no-logfile': { type: 'boolean' },\n};\nconst { values, tokens } = parseArgs({ options, tokens: true });\n\n// Reprocess the option tokens and overwrite the returned values.\ntokens\n .filter((token) => token.kind === 'option')\n .forEach((token) => {\n if (token.name.startsWith('no-')) {\n // Store foo:false for --no-foo\n const positiveName = token.name.slice(3);\n values[positiveName] = false;\n delete values[token.name];\n } else {\n // Resave value so last one wins if both --foo and --no-foo.\n values[token.name] = token.value ?? true;\n }\n });\n\nconst color = values.color;\nconst logfile = values.logfile ?? 'default.log';\n\nconsole.log({ logfile, color });\n
\nconst { parseArgs } = require('node:util');\n\nconst options = {\n 'color': { type: 'boolean' },\n 'no-color': { type: 'boolean' },\n 'logfile': { type: 'string' },\n 'no-logfile': { type: 'boolean' },\n};\nconst { values, tokens } = parseArgs({ options, tokens: true });\n\n// Reprocess the option tokens and overwrite the returned values.\ntokens\n .filter((token) => token.kind === 'option')\n .forEach((token) => {\n if (token.name.startsWith('no-')) {\n // Store foo:false for --no-foo\n const positiveName = token.name.slice(3);\n values[positiveName] = false;\n delete values[token.name];\n } else {\n // Resave value so last one wins if both --foo and --no-foo.\n values[token.name] = token.value ?? true;\n }\n });\n\nconst color = values.color;\nconst logfile = values.logfile ?? 'default.log';\n\nconsole.log({ logfile, color });\n
\nExample usage showing negated options, and when an option is used\nmultiple ways then last one wins.
\n$ node negate.js\n{ logfile: 'default.log', color: undefined }\n$ node negate.js --no-logfile --no-color\n{ logfile: false, color: false }\n$ node negate.js --logfile=test.log --color\n{ logfile: 'test.log', color: true }\n$ node negate.js --no-logfile --logfile=test.log --color --no-color\n{ logfile: 'test.log', color: false }\n
",
"type": "module",
"displayName": "`parseArgs` `tokens`"
}
]
},
{
"textRaw": "`util.parseEnv(content)`",
"type": "method",
"name": "parseEnv",
"stability": 1,
"stabilityText": ".1 - Active development",
"meta": {
"added": [
"v21.7.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`content` {string}",
"name": "content",
"type": "string"
}
]
}
],
"desc": "The raw contents of a .env
file.
Given an example .env
file:
const { parseEnv } = require('node:util');\n\nparseEnv('HELLO=world\\nHELLO=oh my\\n');\n// Returns: { HELLO: 'oh my' }\n
\nimport { parseEnv } from 'node:util';\n\nparseEnv('HELLO=world\\nHELLO=oh my\\n');\n// Returns: { HELLO: 'oh my' }\n
"
},
{
"textRaw": "`util.promisify(original)`",
"type": "method",
"name": "promisify",
"meta": {
"added": [
"v8.0.0"
],
"changes": [
{
"version": "v20.8.0",
"pr-url": "https://github.com/nodejs/node/pull/49647",
"description": "Calling `promisify` on a function that returns a `Promise` is deprecated."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function}",
"name": "return",
"type": "Function"
},
"params": [
{
"textRaw": "`original` {Function}",
"name": "original",
"type": "Function"
}
]
}
],
"desc": "Takes a function following the common error-first callback style, i.e. taking\nan (err, value) => ...
callback as the last argument, and returns a version\nthat returns promises.
const util = require('node:util');\nconst fs = require('node:fs');\n\nconst stat = util.promisify(fs.stat);\nstat('.').then((stats) => {\n // Do something with `stats`\n}).catch((error) => {\n // Handle the error.\n});\n
\nOr, equivalently using async function
s:
const util = require('node:util');\nconst fs = require('node:fs');\n\nconst stat = util.promisify(fs.stat);\n\nasync function callStat() {\n const stats = await stat('.');\n console.log(`This directory is owned by ${stats.uid}`);\n}\n\ncallStat();\n
\nIf there is an original[util.promisify.custom]
property present, promisify
\nwill return its value, see Custom promisified functions.
promisify()
assumes that original
is a function taking a callback as its\nfinal argument in all cases. If original
is not a function, promisify()
\nwill throw an error. If original
is a function but its last argument is not\nan error-first callback, it will still be passed an error-first\ncallback as its last argument.
Using promisify()
on class methods or other methods that use this
may not\nwork as expected unless handled specially:
const util = require('node:util');\n\nclass Foo {\n constructor() {\n this.a = 42;\n }\n\n bar(callback) {\n callback(null, this.a);\n }\n}\n\nconst foo = new Foo();\n\nconst naiveBar = util.promisify(foo.bar);\n// TypeError: Cannot read property 'a' of undefined\n// naiveBar().then(a => console.log(a));\n\nnaiveBar.call(foo).then((a) => console.log(a)); // '42'\n\nconst bindBar = naiveBar.bind(foo);\nbindBar().then((a) => console.log(a)); // '42'\n
",
"modules": [
{
"textRaw": "Custom promisified functions",
"name": "custom_promisified_functions",
"desc": "Using the util.promisify.custom
symbol one can override the return value of\nutil.promisify()
:
const util = require('node:util');\n\nfunction doSomething(foo, callback) {\n // ...\n}\n\ndoSomething[util.promisify.custom] = (foo) => {\n return getPromiseSomehow();\n};\n\nconst promisified = util.promisify(doSomething);\nconsole.log(promisified === doSomething[util.promisify.custom]);\n// prints 'true'\n
\nThis can be useful for cases where the original function does not follow the\nstandard format of taking an error-first callback as the last argument.
\nFor example, with a function that takes in\n(foo, onSuccessCallback, onErrorCallback)
:
doSomething[util.promisify.custom] = (foo) => {\n return new Promise((resolve, reject) => {\n doSomething(foo, resolve, reject);\n });\n};\n
\nIf promisify.custom
is defined but is not a function, promisify()
will\nthrow an error.
In addition to being accessible through util.promisify.custom
, this\nsymbol is registered globally and can be\naccessed in any environment as Symbol.for('nodejs.util.promisify.custom')
.
For example, with a function that takes in\n(foo, onSuccessCallback, onErrorCallback)
:
const kCustomPromisifiedSymbol = Symbol.for('nodejs.util.promisify.custom');\n\ndoSomething[kCustomPromisifiedSymbol] = (foo) => {\n return new Promise((resolve, reject) => {\n doSomething(foo, resolve, reject);\n });\n};\n
",
"shortDesc": "that can be used to declare custom promisified variants of functions, see [Custom promisified functions][]."
}
]
},
{
"textRaw": "`util.stripVTControlCharacters(str)`",
"type": "method",
"name": "stripVTControlCharacters",
"meta": {
"added": [
"v16.11.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`str` {string}",
"name": "str",
"type": "string"
}
]
}
],
"desc": "Returns str
with any ANSI escape codes removed.
console.log(util.stripVTControlCharacters('\\u001B[4mvalue\\u001B[0m'));\n// Prints \"value\"\n
"
},
{
"textRaw": "`util.styleText(format, text)`",
"type": "method",
"name": "styleText",
"stability": 1,
"stabilityText": ".1 - Active development",
"meta": {
"added": [
"v21.7.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`format` {string} A text format defined in `util.inspect.colors`.",
"name": "format",
"type": "string",
"desc": "A text format defined in `util.inspect.colors`."
},
{
"textRaw": "`text` {string} The text to to be formatted.",
"name": "text",
"type": "string",
"desc": "The text to to be formatted."
}
]
}
],
"desc": "This function returns a formatted text considering the format
passed.
import { styleText } from 'node:util';\nconst errorMessage = styleText('red', 'Error! Error!');\nconsole.log(errorMessage);\n
\nconst { styleText } = require('node:util');\nconst errorMessage = styleText('red', 'Error! Error!');\nconsole.log(errorMessage);\n
\nutil.inspect.colors
also provides text formats such as italic
, and\nunderline
and you can combine both:
console.log(\n util.styleText('underline', util.styleText('italic', 'My italic underlined message')),\n);\n
\nThe full list of formats can be found in modifiers.
" }, { "textRaw": "`util.toUSVString(string)`", "type": "method", "name": "toUSVString", "meta": { "added": [ "v16.8.0", "v14.18.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`string` {string}", "name": "string", "type": "string" } ] } ], "desc": "Returns the string
after replacing any surrogate code points\n(or equivalently, any unpaired surrogate code units) with the\nUnicode \"replacement character\" U+FFFD.
Creates and returns an <AbortController> instance whose <AbortSignal> is marked\nas transferable and can be used with structuredClone()
or postMessage()
.
Marks the given <AbortSignal> as transferable so that it can be used with\nstructuredClone()
and postMessage()
.
const signal = transferableAbortSignal(AbortSignal.timeout(100));\nconst channel = new MessageChannel();\nchannel.port2.postMessage(signal, [signal]);\n
"
},
{
"textRaw": "`util.aborted(signal, resource)`",
"type": "method",
"name": "aborted",
"meta": {
"added": [
"v19.7.0",
"v18.16.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise}",
"name": "return",
"type": "Promise"
},
"params": [
{
"textRaw": "`signal` {AbortSignal}",
"name": "signal",
"type": "AbortSignal"
},
{
"textRaw": "`resource` {Object} Any non-null entity, reference to which is held weakly.",
"name": "resource",
"type": "Object",
"desc": "Any non-null entity, reference to which is held weakly."
}
]
}
],
"desc": "Listens to abort event on the provided signal
and\nreturns a promise that is fulfilled when the signal
is\naborted. If the passed resource
is garbage collected before the signal
is\naborted, the returned promise shall remain pending indefinitely.
const { aborted } = require('node:util');\n\nconst dependent = obtainSomethingAbortable();\n\naborted(dependent.signal, dependent).then(() => {\n // Do something when dependent is aborted.\n});\n\ndependent.on('event', () => {\n dependent.abort();\n});\n
\nimport { aborted } from 'node:util';\n\nconst dependent = obtainSomethingAbortable();\n\naborted(dependent.signal, dependent).then(() => {\n // Do something when dependent is aborted.\n});\n\ndependent.on('event', () => {\n dependent.abort();\n});\n
"
}
],
"classes": [
{
"textRaw": "Class: `util.MIMEType`",
"type": "class",
"name": "util.MIMEType",
"meta": {
"added": [
"v19.1.0",
"v18.13.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "An implementation of the MIMEType class.
\nIn accordance with browser conventions, all properties of MIMEType
objects\nare implemented as getters and setters on the class prototype, rather than as\ndata properties on the object itself.
A MIME string is a structured string containing multiple meaningful\ncomponents. When parsed, a MIMEType
object is returned containing\nproperties for each of these components.
Gets and sets the type portion of the MIME.
\nimport { MIMEType } from 'node:util';\n\nconst myMIME = new MIMEType('text/javascript');\nconsole.log(myMIME.type);\n// Prints: text\nmyMIME.type = 'application';\nconsole.log(myMIME.type);\n// Prints: application\nconsole.log(String(myMIME));\n// Prints: application/javascript\n
\nconst { MIMEType } = require('node:util');\n\nconst myMIME = new MIMEType('text/javascript');\nconsole.log(myMIME.type);\n// Prints: text\nmyMIME.type = 'application';\nconsole.log(myMIME.type);\n// Prints: application\nconsole.log(String(myMIME));\n// Prints: application/javascript\n
"
},
{
"textRaw": "`subtype` {string}",
"type": "string",
"name": "subtype",
"desc": "Gets and sets the subtype portion of the MIME.
\nimport { MIMEType } from 'node:util';\n\nconst myMIME = new MIMEType('text/ecmascript');\nconsole.log(myMIME.subtype);\n// Prints: ecmascript\nmyMIME.subtype = 'javascript';\nconsole.log(myMIME.subtype);\n// Prints: javascript\nconsole.log(String(myMIME));\n// Prints: text/javascript\n
\nconst { MIMEType } = require('node:util');\n\nconst myMIME = new MIMEType('text/ecmascript');\nconsole.log(myMIME.subtype);\n// Prints: ecmascript\nmyMIME.subtype = 'javascript';\nconsole.log(myMIME.subtype);\n// Prints: javascript\nconsole.log(String(myMIME));\n// Prints: text/javascript\n
"
},
{
"textRaw": "`essence` {string}",
"type": "string",
"name": "essence",
"desc": "Gets the essence of the MIME. This property is read only.\nUse mime.type
or mime.subtype
to alter the MIME.
import { MIMEType } from 'node:util';\n\nconst myMIME = new MIMEType('text/javascript;key=value');\nconsole.log(myMIME.essence);\n// Prints: text/javascript\nmyMIME.type = 'application';\nconsole.log(myMIME.essence);\n// Prints: application/javascript\nconsole.log(String(myMIME));\n// Prints: application/javascript;key=value\n
\nconst { MIMEType } = require('node:util');\n\nconst myMIME = new MIMEType('text/javascript;key=value');\nconsole.log(myMIME.essence);\n// Prints: text/javascript\nmyMIME.type = 'application';\nconsole.log(myMIME.essence);\n// Prints: application/javascript\nconsole.log(String(myMIME));\n// Prints: application/javascript;key=value\n
"
},
{
"textRaw": "`params` {MIMEParams}",
"type": "MIMEParams",
"name": "params",
"desc": "Gets the MIMEParams
object representing the\nparameters of the MIME. This property is read-only. See\nMIMEParams
documentation for details.
The toString()
method on the MIMEType
object returns the serialized MIME.
Because of the need for standard compliance, this method does not allow users\nto customize the serialization process of the MIME.
" }, { "textRaw": "`mime.toJSON()`", "type": "method", "name": "toJSON", "signatures": [ { "return": { "textRaw": "Returns: {string}", "name": "return", "type": "string" }, "params": [] } ], "desc": "Alias for mime.toString()
.
This method is automatically called when an MIMEType
object is serialized\nwith JSON.stringify()
.
import { MIMEType } from 'node:util';\n\nconst myMIMES = [\n new MIMEType('image/png'),\n new MIMEType('image/gif'),\n];\nconsole.log(JSON.stringify(myMIMES));\n// Prints: [\"image/png\", \"image/gif\"]\n
\nconst { MIMEType } = require('node:util');\n\nconst myMIMES = [\n new MIMEType('image/png'),\n new MIMEType('image/gif'),\n];\nconsole.log(JSON.stringify(myMIMES));\n// Prints: [\"image/png\", \"image/gif\"]\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`input` {string} The input MIME to parse",
"name": "input",
"type": "string",
"desc": "The input MIME to parse"
}
],
"desc": "Creates a new MIMEType
object by parsing the input
.
import { MIMEType } from 'node:util';\n\nconst myMIME = new MIMEType('text/plain');\n
\nconst { MIMEType } = require('node:util');\n\nconst myMIME = new MIMEType('text/plain');\n
\nA TypeError
will be thrown if the input
is not a valid MIME. Note\nthat an effort will be made to coerce the given values into strings. For\ninstance:
import { MIMEType } from 'node:util';\nconst myMIME = new MIMEType({ toString: () => 'text/plain' });\nconsole.log(String(myMIME));\n// Prints: text/plain\n
\nconst { MIMEType } = require('node:util');\nconst myMIME = new MIMEType({ toString: () => 'text/plain' });\nconsole.log(String(myMIME));\n// Prints: text/plain\n
"
}
]
},
{
"textRaw": "Class: `util.MIMEParams`",
"type": "class",
"name": "util.MIMEParams",
"meta": {
"added": [
"v19.1.0",
"v18.13.0"
],
"changes": []
},
"desc": "The MIMEParams
API provides read and write access to the parameters of a\nMIMEType
.
Remove all name-value pairs whose name is name
.
Returns an iterator over each of the name-value pairs in the parameters.\nEach item of the iterator is a JavaScript Array
. The first item of the array\nis the name
, the second item of the array is the value
.
Returns the value of the first name-value pair whose name is name
. If there\nare no such pairs, null
is returned.
Returns true
if there is at least one name-value pair whose name is name
.
Returns an iterator over the names of each name-value pair.
\nimport { MIMEType } from 'node:util';\n\nconst { params } = new MIMEType('text/plain;foo=0;bar=1');\nfor (const name of params.keys()) {\n console.log(name);\n}\n// Prints:\n// foo\n// bar\n
\nconst { MIMEType } = require('node:util');\n\nconst { params } = new MIMEType('text/plain;foo=0;bar=1');\nfor (const name of params.keys()) {\n console.log(name);\n}\n// Prints:\n// foo\n// bar\n
"
},
{
"textRaw": "`mimeParams.set(name, value)`",
"type": "method",
"name": "set",
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {string}",
"name": "value",
"type": "string"
}
]
}
],
"desc": "Sets the value in the MIMEParams
object associated with name
to\nvalue
. If there are any pre-existing name-value pairs whose names are name
,\nset the first such pair's value to value
.
import { MIMEType } from 'node:util';\n\nconst { params } = new MIMEType('text/plain;foo=0;bar=1');\nparams.set('foo', 'def');\nparams.set('baz', 'xyz');\nconsole.log(params.toString());\n// Prints: foo=def;bar=1;baz=xyz\n
\nconst { MIMEType } = require('node:util');\n\nconst { params } = new MIMEType('text/plain;foo=0;bar=1');\nparams.set('foo', 'def');\nparams.set('baz', 'xyz');\nconsole.log(params.toString());\n// Prints: foo=def;bar=1;baz=xyz\n
"
},
{
"textRaw": "`mimeParams.values()`",
"type": "method",
"name": "values",
"signatures": [
{
"return": {
"textRaw": "Returns: {Iterator}",
"name": "return",
"type": "Iterator"
},
"params": []
}
],
"desc": "Returns an iterator over the values of each name-value pair.
" } ], "modules": [ { "textRaw": "`mimeParams[@@iterator]()`", "name": "`mimeparams[@@iterator]()`", "desc": "Alias for mimeParams.entries()
.
import { MIMEType } from 'node:util';\n\nconst { params } = new MIMEType('text/plain;foo=bar;xyz=baz');\nfor (const [name, value] of params) {\n console.log(name, value);\n}\n// Prints:\n// foo bar\n// xyz baz\n
\nconst { MIMEType } = require('node:util');\n\nconst { params } = new MIMEType('text/plain;foo=bar;xyz=baz');\nfor (const [name, value] of params) {\n console.log(name, value);\n}\n// Prints:\n// foo bar\n// xyz baz\n
",
"type": "module",
"displayName": "`mimeParams[@@iterator]()`"
}
],
"signatures": [
{
"params": [],
"desc": "Creates a new MIMEParams
object by with empty parameters
import { MIMEParams } from 'node:util';\n\nconst myParams = new MIMEParams();\n
\nconst { MIMEParams } = require('node:util');\n\nconst myParams = new MIMEParams();\n
"
}
]
},
{
"textRaw": "Class: `util.TextDecoder`",
"type": "class",
"name": "util.TextDecoder",
"meta": {
"added": [
"v8.3.0"
],
"changes": []
},
"desc": "An implementation of the WHATWG Encoding Standard TextDecoder
API.
const decoder = new TextDecoder();\nconst u8arr = new Uint8Array([72, 101, 108, 108, 111]);\nconsole.log(decoder.decode(u8arr)); // Hello\n
",
"modules": [
{
"textRaw": "WHATWG supported encodings",
"name": "whatwg_supported_encodings",
"desc": "Per the WHATWG Encoding Standard, the encodings supported by the\nTextDecoder
API are outlined in the tables below. For each encoding,\none or more aliases may be used.
Different Node.js build configurations support different sets of encodings.\n(see Internationalization)
", "modules": [ { "textRaw": "Encodings supported by default (with full ICU data)", "name": "encodings_supported_by_default_(with_full_icu_data)", "desc": "Encoding | \nAliases | \n
---|---|
'ibm866' | \n'866' , 'cp866' , 'csibm866' | \n
'iso-8859-2' | \n'csisolatin2' , 'iso-ir-101' , 'iso8859-2' , 'iso88592' , 'iso_8859-2' , 'iso_8859-2:1987' , 'l2' , 'latin2' | \n
'iso-8859-3' | \n'csisolatin3' , 'iso-ir-109' , 'iso8859-3' , 'iso88593' , 'iso_8859-3' , 'iso_8859-3:1988' , 'l3' , 'latin3' | \n
'iso-8859-4' | \n'csisolatin4' , 'iso-ir-110' , 'iso8859-4' , 'iso88594' , 'iso_8859-4' , 'iso_8859-4:1988' , 'l4' , 'latin4' | \n
'iso-8859-5' | \n'csisolatincyrillic' , 'cyrillic' , 'iso-ir-144' , 'iso8859-5' , 'iso88595' , 'iso_8859-5' , 'iso_8859-5:1988' | \n
'iso-8859-6' | \n'arabic' , 'asmo-708' , 'csiso88596e' , 'csiso88596i' , 'csisolatinarabic' , 'ecma-114' , 'iso-8859-6-e' , 'iso-8859-6-i' , 'iso-ir-127' , 'iso8859-6' , 'iso88596' , 'iso_8859-6' , 'iso_8859-6:1987' | \n
'iso-8859-7' | \n'csisolatingreek' , 'ecma-118' , 'elot_928' , 'greek' , 'greek8' , 'iso-ir-126' , 'iso8859-7' , 'iso88597' , 'iso_8859-7' , 'iso_8859-7:1987' , 'sun_eu_greek' | \n
'iso-8859-8' | \n'csiso88598e' , 'csisolatinhebrew' , 'hebrew' , 'iso-8859-8-e' , 'iso-ir-138' , 'iso8859-8' , 'iso88598' , 'iso_8859-8' , 'iso_8859-8:1988' , 'visual' | \n
'iso-8859-8-i' | \n'csiso88598i' , 'logical' | \n
'iso-8859-10' | \n'csisolatin6' , 'iso-ir-157' , 'iso8859-10' , 'iso885910' , 'l6' , 'latin6' | \n
'iso-8859-13' | \n'iso8859-13' , 'iso885913' | \n
'iso-8859-14' | \n'iso8859-14' , 'iso885914' | \n
'iso-8859-15' | \n'csisolatin9' , 'iso8859-15' , 'iso885915' , 'iso_8859-15' , 'l9' | \n
'koi8-r' | \n'cskoi8r' , 'koi' , 'koi8' , 'koi8_r' | \n
'koi8-u' | \n'koi8-ru' | \n
'macintosh' | \n'csmacintosh' , 'mac' , 'x-mac-roman' | \n
'windows-874' | \n'dos-874' , 'iso-8859-11' , 'iso8859-11' , 'iso885911' , 'tis-620' | \n
'windows-1250' | \n'cp1250' , 'x-cp1250' | \n
'windows-1251' | \n'cp1251' , 'x-cp1251' | \n
'windows-1252' | \n'ansi_x3.4-1968' , 'ascii' , 'cp1252' , 'cp819' , 'csisolatin1' , 'ibm819' , 'iso-8859-1' , 'iso-ir-100' , 'iso8859-1' , 'iso88591' , 'iso_8859-1' , 'iso_8859-1:1987' , 'l1' , 'latin1' , 'us-ascii' , 'x-cp1252' | \n
'windows-1253' | \n'cp1253' , 'x-cp1253' | \n
'windows-1254' | \n'cp1254' , 'csisolatin5' , 'iso-8859-9' , 'iso-ir-148' , 'iso8859-9' , 'iso88599' , 'iso_8859-9' , 'iso_8859-9:1989' , 'l5' , 'latin5' , 'x-cp1254' | \n
'windows-1255' | \n'cp1255' , 'x-cp1255' | \n
'windows-1256' | \n'cp1256' , 'x-cp1256' | \n
'windows-1257' | \n'cp1257' , 'x-cp1257' | \n
'windows-1258' | \n'cp1258' , 'x-cp1258' | \n
'x-mac-cyrillic' | \n'x-mac-ukrainian' | \n
'gbk' | \n'chinese' , 'csgb2312' , 'csiso58gb231280' , 'gb2312' , 'gb_2312' , 'gb_2312-80' , 'iso-ir-58' , 'x-gbk' | \n
'gb18030' | \n\n |
'big5' | \n'big5-hkscs' , 'cn-big5' , 'csbig5' , 'x-x-big5' | \n
'euc-jp' | \n'cseucpkdfmtjapanese' , 'x-euc-jp' | \n
'iso-2022-jp' | \n'csiso2022jp' | \n
'shift_jis' | \n'csshiftjis' , 'ms932' , 'ms_kanji' , 'shift-jis' , 'sjis' , 'windows-31j' , 'x-sjis' | \n
'euc-kr' | \n'cseuckr' , 'csksc56011987' , 'iso-ir-149' , 'korean' , 'ks_c_5601-1987' , 'ks_c_5601-1989' , 'ksc5601' , 'ksc_5601' , 'windows-949' | \n
Encoding | \nAliases | \n
---|---|
'utf-8' | \n'unicode-1-1-utf-8' , 'utf8' | \n
'utf-16le' | \n'utf-16' | \n
'utf-16be' | \n\n |
Encoding | \nAliases | \n
---|---|
'utf-8' | \n'unicode-1-1-utf-8' , 'utf8' | \n
'utf-16le' | \n'utf-16' | \n
The 'iso-8859-16'
encoding listed in the WHATWG Encoding Standard\nis not supported.
Decodes the input
and returns a string. If options.stream
is true
, any\nincomplete byte sequences occurring at the end of the input
are buffered\ninternally and emitted after the next call to textDecoder.decode()
.
If textDecoder.fatal
is true
, decoding errors that occur will result in a\nTypeError
being thrown.
The encoding supported by the TextDecoder
instance.
The value will be true
if decoding errors result in a TypeError
being\nthrown.
The value will be true
if the decoding result will include the byte order\nmark.
Creates a new TextDecoder
instance. The encoding
may specify one of the\nsupported encodings or an alias.
The TextDecoder
class is also available on the global object.
An implementation of the WHATWG Encoding Standard TextEncoder
API. All\ninstances of TextEncoder
only support UTF-8 encoding.
const encoder = new TextEncoder();\nconst uint8array = encoder.encode('this is some data');\n
\nThe TextEncoder
class is also available on the global object.
UTF-8 encodes the input
string and returns a Uint8Array
containing the\nencoded bytes.
UTF-8 encodes the src
string to the dest
Uint8Array and returns an object\ncontaining the read Unicode code units and written UTF-8 bytes.
const encoder = new TextEncoder();\nconst src = 'this is some data';\nconst dest = new Uint8Array(10);\nconst { read, written } = encoder.encodeInto(src, dest);\n
"
}
],
"properties": [
{
"textRaw": "`encoding` {string}",
"type": "string",
"name": "encoding",
"desc": "The encoding supported by the TextEncoder
instance. Always set to 'utf-8'
.
util.types
provides type checks for different kinds of built-in objects.\nUnlike instanceof
or Object.prototype.toString.call(value)
, these checks do\nnot inspect properties of the object that are accessible from JavaScript (like\ntheir prototype), and usually have the overhead of calling into C++.
The result generally does not make any guarantees about what kinds of\nproperties or behavior a value exposes in JavaScript. They are primarily\nuseful for addon developers who prefer to do type checking in JavaScript.
\nThe API is accessible via require('node:util').types
or require('node:util/types')
.
Returns true
if the value is a built-in ArrayBuffer
or\nSharedArrayBuffer
instance.
See also util.types.isArrayBuffer()
and\nutil.types.isSharedArrayBuffer()
.
util.types.isAnyArrayBuffer(new ArrayBuffer()); // Returns true\nutil.types.isAnyArrayBuffer(new SharedArrayBuffer()); // Returns true\n
"
},
{
"textRaw": "`util.types.isArrayBufferView(value)`",
"type": "method",
"name": "isArrayBufferView",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is an instance of one of the ArrayBuffer
\nviews, such as typed array objects or DataView
. Equivalent to\nArrayBuffer.isView()
.
util.types.isArrayBufferView(new Int8Array()); // true\nutil.types.isArrayBufferView(Buffer.from('hello world')); // true\nutil.types.isArrayBufferView(new DataView(new ArrayBuffer(16))); // true\nutil.types.isArrayBufferView(new ArrayBuffer()); // false\n
"
},
{
"textRaw": "`util.types.isArgumentsObject(value)`",
"type": "method",
"name": "isArgumentsObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is an arguments
object.
function foo() {\n util.types.isArgumentsObject(arguments); // Returns true\n}\n
"
},
{
"textRaw": "`util.types.isArrayBuffer(value)`",
"type": "method",
"name": "isArrayBuffer",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in ArrayBuffer
instance.\nThis does not include SharedArrayBuffer
instances. Usually, it is\ndesirable to test for both; See util.types.isAnyArrayBuffer()
for that.
util.types.isArrayBuffer(new ArrayBuffer()); // Returns true\nutil.types.isArrayBuffer(new SharedArrayBuffer()); // Returns false\n
"
},
{
"textRaw": "`util.types.isAsyncFunction(value)`",
"type": "method",
"name": "isAsyncFunction",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is an async function.\nThis only reports back what the JavaScript engine is seeing;\nin particular, the return value may not match the original source code if\na transpilation tool was used.
util.types.isAsyncFunction(function foo() {}); // Returns false\nutil.types.isAsyncFunction(async function foo() {}); // Returns true\n
"
},
{
"textRaw": "`util.types.isBigInt64Array(value)`",
"type": "method",
"name": "isBigInt64Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a BigInt64Array
instance.
util.types.isBigInt64Array(new BigInt64Array()); // Returns true\nutil.types.isBigInt64Array(new BigUint64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isBigUint64Array(value)`",
"type": "method",
"name": "isBigUint64Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a BigUint64Array
instance.
util.types.isBigUint64Array(new BigInt64Array()); // Returns false\nutil.types.isBigUint64Array(new BigUint64Array()); // Returns true\n
"
},
{
"textRaw": "`util.types.isBooleanObject(value)`",
"type": "method",
"name": "isBooleanObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a boolean object, e.g. created\nby new Boolean()
.
util.types.isBooleanObject(false); // Returns false\nutil.types.isBooleanObject(true); // Returns false\nutil.types.isBooleanObject(new Boolean(false)); // Returns true\nutil.types.isBooleanObject(new Boolean(true)); // Returns true\nutil.types.isBooleanObject(Boolean(false)); // Returns false\nutil.types.isBooleanObject(Boolean(true)); // Returns false\n
"
},
{
"textRaw": "`util.types.isBoxedPrimitive(value)`",
"type": "method",
"name": "isBoxedPrimitive",
"meta": {
"added": [
"v10.11.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is any boxed primitive object, e.g. created\nby new Boolean()
, new String()
or Object(Symbol())
.
For example:
\nutil.types.isBoxedPrimitive(false); // Returns false\nutil.types.isBoxedPrimitive(new Boolean(false)); // Returns true\nutil.types.isBoxedPrimitive(Symbol('foo')); // Returns false\nutil.types.isBoxedPrimitive(Object(Symbol('foo'))); // Returns true\nutil.types.isBoxedPrimitive(Object(BigInt(5))); // Returns true\n
"
},
{
"textRaw": "`util.types.isCryptoKey(value)`",
"type": "method",
"name": "isCryptoKey",
"meta": {
"added": [
"v16.2.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {Object}",
"name": "value",
"type": "Object"
}
]
}
],
"desc": "Returns true
if value
is a <CryptoKey>, false
otherwise.
Returns true
if the value is a built-in DataView
instance.
const ab = new ArrayBuffer(20);\nutil.types.isDataView(new DataView(ab)); // Returns true\nutil.types.isDataView(new Float64Array()); // Returns false\n
\nSee also ArrayBuffer.isView()
.
Returns true
if the value is a built-in Date
instance.
util.types.isDate(new Date()); // Returns true\n
"
},
{
"textRaw": "`util.types.isExternal(value)`",
"type": "method",
"name": "isExternal",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a native External
value.
A native External
value is a special type of object that contains a\nraw C++ pointer (void*
) for access from native code, and has no other\nproperties. Such objects are created either by Node.js internals or native\naddons. In JavaScript, they are frozen objects with a\nnull
prototype.
#include <js_native_api.h>\n#include <stdlib.h>\nnapi_value result;\nstatic napi_value MyNapi(napi_env env, napi_callback_info info) {\n int* raw = (int*) malloc(1024);\n napi_status status = napi_create_external(env, (void*) raw, NULL, NULL, &result);\n if (status != napi_ok) {\n napi_throw_error(env, NULL, \"napi_create_external failed\");\n return NULL;\n }\n return result;\n}\n...\nDECLARE_NAPI_PROPERTY(\"myNapi\", MyNapi)\n...\n
\nconst native = require('napi_addon.node');\nconst data = native.myNapi();\nutil.types.isExternal(data); // returns true\nutil.types.isExternal(0); // returns false\nutil.types.isExternal(new String('foo')); // returns false\n
\nFor further information on napi_create_external
, refer to\nnapi_create_external()
.
Returns true
if the value is a built-in Float32Array
instance.
util.types.isFloat32Array(new ArrayBuffer()); // Returns false\nutil.types.isFloat32Array(new Float32Array()); // Returns true\nutil.types.isFloat32Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isFloat64Array(value)`",
"type": "method",
"name": "isFloat64Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Float64Array
instance.
util.types.isFloat64Array(new ArrayBuffer()); // Returns false\nutil.types.isFloat64Array(new Uint8Array()); // Returns false\nutil.types.isFloat64Array(new Float64Array()); // Returns true\n
"
},
{
"textRaw": "`util.types.isGeneratorFunction(value)`",
"type": "method",
"name": "isGeneratorFunction",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a generator function.\nThis only reports back what the JavaScript engine is seeing;\nin particular, the return value may not match the original source code if\na transpilation tool was used.
util.types.isGeneratorFunction(function foo() {}); // Returns false\nutil.types.isGeneratorFunction(function* foo() {}); // Returns true\n
"
},
{
"textRaw": "`util.types.isGeneratorObject(value)`",
"type": "method",
"name": "isGeneratorObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a generator object as returned from a\nbuilt-in generator function.\nThis only reports back what the JavaScript engine is seeing;\nin particular, the return value may not match the original source code if\na transpilation tool was used.
function* foo() {}\nconst generator = foo();\nutil.types.isGeneratorObject(generator); // Returns true\n
"
},
{
"textRaw": "`util.types.isInt8Array(value)`",
"type": "method",
"name": "isInt8Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Int8Array
instance.
util.types.isInt8Array(new ArrayBuffer()); // Returns false\nutil.types.isInt8Array(new Int8Array()); // Returns true\nutil.types.isInt8Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isInt16Array(value)`",
"type": "method",
"name": "isInt16Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Int16Array
instance.
util.types.isInt16Array(new ArrayBuffer()); // Returns false\nutil.types.isInt16Array(new Int16Array()); // Returns true\nutil.types.isInt16Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isInt32Array(value)`",
"type": "method",
"name": "isInt32Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Int32Array
instance.
util.types.isInt32Array(new ArrayBuffer()); // Returns false\nutil.types.isInt32Array(new Int32Array()); // Returns true\nutil.types.isInt32Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isKeyObject(value)`",
"type": "method",
"name": "isKeyObject",
"meta": {
"added": [
"v16.2.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {Object}",
"name": "value",
"type": "Object"
}
]
}
],
"desc": "Returns true
if value
is a <KeyObject>, false
otherwise.
Returns true
if the value is a built-in Map
instance.
util.types.isMap(new Map()); // Returns true\n
"
},
{
"textRaw": "`util.types.isMapIterator(value)`",
"type": "method",
"name": "isMapIterator",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is an iterator returned for a built-in\nMap
instance.
const map = new Map();\nutil.types.isMapIterator(map.keys()); // Returns true\nutil.types.isMapIterator(map.values()); // Returns true\nutil.types.isMapIterator(map.entries()); // Returns true\nutil.types.isMapIterator(map[Symbol.iterator]()); // Returns true\n
"
},
{
"textRaw": "`util.types.isModuleNamespaceObject(value)`",
"type": "method",
"name": "isModuleNamespaceObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is an instance of a Module Namespace Object.
import * as ns from './a.js';\n\nutil.types.isModuleNamespaceObject(ns); // Returns true\n
"
},
{
"textRaw": "`util.types.isNativeError(value)`",
"type": "method",
"name": "isNativeError",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value was returned by the constructor of a\nbuilt-in Error
type.
console.log(util.types.isNativeError(new Error())); // true\nconsole.log(util.types.isNativeError(new TypeError())); // true\nconsole.log(util.types.isNativeError(new RangeError())); // true\n
\nSubclasses of the native error types are also native errors:
\nclass MyError extends Error {}\nconsole.log(util.types.isNativeError(new MyError())); // true\n
\nA value being instanceof
a native error class is not equivalent to isNativeError()
\nreturning true
for that value. isNativeError()
returns true
for errors\nwhich come from a different realm while instanceof Error
returns false
\nfor these errors:
const vm = require('node:vm');\nconst context = vm.createContext({});\nconst myError = vm.runInContext('new Error()', context);\nconsole.log(util.types.isNativeError(myError)); // true\nconsole.log(myError instanceof Error); // false\n
\nConversely, isNativeError()
returns false
for all objects which were not\nreturned by the constructor of a native error. That includes values\nwhich are instanceof
native errors:
const myError = { __proto__: Error.prototype };\nconsole.log(util.types.isNativeError(myError)); // false\nconsole.log(myError instanceof Error); // true\n
"
},
{
"textRaw": "`util.types.isNumberObject(value)`",
"type": "method",
"name": "isNumberObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a number object, e.g. created\nby new Number()
.
util.types.isNumberObject(0); // Returns false\nutil.types.isNumberObject(new Number(0)); // Returns true\n
"
},
{
"textRaw": "`util.types.isPromise(value)`",
"type": "method",
"name": "isPromise",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Promise
.
util.types.isPromise(Promise.resolve(42)); // Returns true\n
"
},
{
"textRaw": "`util.types.isProxy(value)`",
"type": "method",
"name": "isProxy",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a Proxy
instance.
const target = {};\nconst proxy = new Proxy(target, {});\nutil.types.isProxy(target); // Returns false\nutil.types.isProxy(proxy); // Returns true\n
"
},
{
"textRaw": "`util.types.isRegExp(value)`",
"type": "method",
"name": "isRegExp",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a regular expression object.
util.types.isRegExp(/abc/); // Returns true\nutil.types.isRegExp(new RegExp('abc')); // Returns true\n
"
},
{
"textRaw": "`util.types.isSet(value)`",
"type": "method",
"name": "isSet",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Set
instance.
util.types.isSet(new Set()); // Returns true\n
"
},
{
"textRaw": "`util.types.isSetIterator(value)`",
"type": "method",
"name": "isSetIterator",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is an iterator returned for a built-in\nSet
instance.
const set = new Set();\nutil.types.isSetIterator(set.keys()); // Returns true\nutil.types.isSetIterator(set.values()); // Returns true\nutil.types.isSetIterator(set.entries()); // Returns true\nutil.types.isSetIterator(set[Symbol.iterator]()); // Returns true\n
"
},
{
"textRaw": "`util.types.isSharedArrayBuffer(value)`",
"type": "method",
"name": "isSharedArrayBuffer",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in SharedArrayBuffer
instance.\nThis does not include ArrayBuffer
instances. Usually, it is\ndesirable to test for both; See util.types.isAnyArrayBuffer()
for that.
util.types.isSharedArrayBuffer(new ArrayBuffer()); // Returns false\nutil.types.isSharedArrayBuffer(new SharedArrayBuffer()); // Returns true\n
"
},
{
"textRaw": "`util.types.isStringObject(value)`",
"type": "method",
"name": "isStringObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a string object, e.g. created\nby new String()
.
util.types.isStringObject('foo'); // Returns false\nutil.types.isStringObject(new String('foo')); // Returns true\n
"
},
{
"textRaw": "`util.types.isSymbolObject(value)`",
"type": "method",
"name": "isSymbolObject",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a symbol object, created\nby calling Object()
on a Symbol
primitive.
const symbol = Symbol('foo');\nutil.types.isSymbolObject(symbol); // Returns false\nutil.types.isSymbolObject(Object(symbol)); // Returns true\n
"
},
{
"textRaw": "`util.types.isTypedArray(value)`",
"type": "method",
"name": "isTypedArray",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in TypedArray
instance.
util.types.isTypedArray(new ArrayBuffer()); // Returns false\nutil.types.isTypedArray(new Uint8Array()); // Returns true\nutil.types.isTypedArray(new Float64Array()); // Returns true\n
\nSee also ArrayBuffer.isView()
.
Returns true
if the value is a built-in Uint8Array
instance.
util.types.isUint8Array(new ArrayBuffer()); // Returns false\nutil.types.isUint8Array(new Uint8Array()); // Returns true\nutil.types.isUint8Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isUint8ClampedArray(value)`",
"type": "method",
"name": "isUint8ClampedArray",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Uint8ClampedArray
instance.
util.types.isUint8ClampedArray(new ArrayBuffer()); // Returns false\nutil.types.isUint8ClampedArray(new Uint8ClampedArray()); // Returns true\nutil.types.isUint8ClampedArray(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isUint16Array(value)`",
"type": "method",
"name": "isUint16Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Uint16Array
instance.
util.types.isUint16Array(new ArrayBuffer()); // Returns false\nutil.types.isUint16Array(new Uint16Array()); // Returns true\nutil.types.isUint16Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isUint32Array(value)`",
"type": "method",
"name": "isUint32Array",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in Uint32Array
instance.
util.types.isUint32Array(new ArrayBuffer()); // Returns false\nutil.types.isUint32Array(new Uint32Array()); // Returns true\nutil.types.isUint32Array(new Float64Array()); // Returns false\n
"
},
{
"textRaw": "`util.types.isWeakMap(value)`",
"type": "method",
"name": "isWeakMap",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in WeakMap
instance.
util.types.isWeakMap(new WeakMap()); // Returns true\n
"
},
{
"textRaw": "`util.types.isWeakSet(value)`",
"type": "method",
"name": "isWeakSet",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"desc": "Returns true
if the value is a built-in WeakSet
instance.
util.types.isWeakSet(new WeakSet()); // Returns true\n
"
}
]
}
],
"modules": [
{
"textRaw": "Deprecated APIs",
"name": "deprecated_apis",
"desc": "The following APIs are deprecated and should no longer be used. Existing\napplications and modules should be updated to find alternative approaches.
", "methods": [ { "textRaw": "`util._extend(target, source)`", "type": "method", "name": "_extend", "meta": { "added": [ "v0.7.5" ], "deprecated": [ "v6.0.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`Object.assign()`][] instead.", "signatures": [ { "params": [ { "textRaw": "`target` {Object}", "name": "target", "type": "Object" }, { "textRaw": "`source` {Object}", "name": "source", "type": "Object" } ] } ], "desc": "The util._extend()
method was never intended to be used outside of internal\nNode.js modules. The community found and used it anyway.
It is deprecated and should not be used in new code. JavaScript comes with very\nsimilar built-in functionality through Object.assign()
.
Alias for Array.isArray()
.
Returns true
if the given object
is an Array
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isArray([]);\n// Returns: true\nutil.isArray(new Array());\n// Returns: true\nutil.isArray({});\n// Returns: false\n
"
},
{
"textRaw": "`util.isBoolean(object)`",
"type": "method",
"name": "isBoolean",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `typeof value === 'boolean'` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a Boolean
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isBoolean(1);\n// Returns: false\nutil.isBoolean(0);\n// Returns: false\nutil.isBoolean(false);\n// Returns: true\n
"
},
{
"textRaw": "`util.isBuffer(object)`",
"type": "method",
"name": "isBuffer",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`Buffer.isBuffer()`][] instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a Buffer
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isBuffer({ length: 0 });\n// Returns: false\nutil.isBuffer([]);\n// Returns: false\nutil.isBuffer(Buffer.from('hello world'));\n// Returns: true\n
"
},
{
"textRaw": "`util.isDate(object)`",
"type": "method",
"name": "isDate",
"meta": {
"added": [
"v0.6.0"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`util.types.isDate()`][] instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a Date
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isDate(new Date());\n// Returns: true\nutil.isDate(Date());\n// false (without 'new' returns a String)\nutil.isDate({});\n// Returns: false\n
"
},
{
"textRaw": "`util.isError(object)`",
"type": "method",
"name": "isError",
"meta": {
"added": [
"v0.6.0"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`util.types.isNativeError()`][] instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is an Error
. Otherwise, returns\nfalse
.
const util = require('node:util');\n\nutil.isError(new Error());\n// Returns: true\nutil.isError(new TypeError());\n// Returns: true\nutil.isError({ name: 'Error', message: 'an error occurred' });\n// Returns: false\n
\nThis method relies on Object.prototype.toString()
behavior. It is\npossible to obtain an incorrect result when the object
argument manipulates\n@@toStringTag
.
const util = require('node:util');\nconst obj = { name: 'Error', message: 'an error occurred' };\n\nutil.isError(obj);\n// Returns: false\nobj[Symbol.toStringTag] = 'Error';\nutil.isError(obj);\n// Returns: true\n
"
},
{
"textRaw": "`util.isFunction(object)`",
"type": "method",
"name": "isFunction",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `typeof value === 'function'` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a Function
. Otherwise, returns\nfalse
.
const util = require('node:util');\n\nfunction Foo() {}\nconst Bar = () => {};\n\nutil.isFunction({});\n// Returns: false\nutil.isFunction(Foo);\n// Returns: true\nutil.isFunction(Bar);\n// Returns: true\n
"
},
{
"textRaw": "`util.isNull(object)`",
"type": "method",
"name": "isNull",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `value === null` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is strictly null
. Otherwise, returns\nfalse
.
const util = require('node:util');\n\nutil.isNull(0);\n// Returns: false\nutil.isNull(undefined);\n// Returns: false\nutil.isNull(null);\n// Returns: true\n
"
},
{
"textRaw": "`util.isNullOrUndefined(object)`",
"type": "method",
"name": "isNullOrUndefined",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `value === undefined || value === null` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is null
or undefined
. Otherwise,\nreturns false
.
const util = require('node:util');\n\nutil.isNullOrUndefined(0);\n// Returns: false\nutil.isNullOrUndefined(undefined);\n// Returns: true\nutil.isNullOrUndefined(null);\n// Returns: true\n
"
},
{
"textRaw": "`util.isNumber(object)`",
"type": "method",
"name": "isNumber",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `typeof value === 'number'` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a Number
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isNumber(false);\n// Returns: false\nutil.isNumber(Infinity);\n// Returns: true\nutil.isNumber(0);\n// Returns: true\nutil.isNumber(NaN);\n// Returns: true\n
"
},
{
"textRaw": "`util.isObject(object)`",
"type": "method",
"name": "isObject",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `value !== null && typeof value === 'object'` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is strictly an Object
and not a\nFunction
(even though functions are objects in JavaScript).\nOtherwise, returns false
.
const util = require('node:util');\n\nutil.isObject(5);\n// Returns: false\nutil.isObject(null);\n// Returns: false\nutil.isObject({});\n// Returns: true\nutil.isObject(() => {});\n// Returns: false\n
"
},
{
"textRaw": "`util.isPrimitive(object)`",
"type": "method",
"name": "isPrimitive",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `(typeof value !== 'object' && typeof value !== 'function') || value === null` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a primitive type. Otherwise, returns\nfalse
.
const util = require('node:util');\n\nutil.isPrimitive(5);\n// Returns: true\nutil.isPrimitive('foo');\n// Returns: true\nutil.isPrimitive(false);\n// Returns: true\nutil.isPrimitive(null);\n// Returns: true\nutil.isPrimitive(undefined);\n// Returns: true\nutil.isPrimitive({});\n// Returns: false\nutil.isPrimitive(() => {});\n// Returns: false\nutil.isPrimitive(/^$/);\n// Returns: false\nutil.isPrimitive(new Date());\n// Returns: false\n
"
},
{
"textRaw": "`util.isRegExp(object)`",
"type": "method",
"name": "isRegExp",
"meta": {
"added": [
"v0.6.0"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a RegExp
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isRegExp(/some regexp/);\n// Returns: true\nutil.isRegExp(new RegExp('another regexp'));\n// Returns: true\nutil.isRegExp({});\n// Returns: false\n
"
},
{
"textRaw": "`util.isString(object)`",
"type": "method",
"name": "isString",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `typeof value === 'string'` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a string
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isString('');\n// Returns: true\nutil.isString('foo');\n// Returns: true\nutil.isString(String('foo'));\n// Returns: true\nutil.isString(5);\n// Returns: false\n
"
},
{
"textRaw": "`util.isSymbol(object)`",
"type": "method",
"name": "isSymbol",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `typeof value === 'symbol'` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is a Symbol
. Otherwise, returns false
.
const util = require('node:util');\n\nutil.isSymbol(5);\n// Returns: false\nutil.isSymbol('foo');\n// Returns: false\nutil.isSymbol(Symbol('foo'));\n// Returns: true\n
"
},
{
"textRaw": "`util.isUndefined(object)`",
"type": "method",
"name": "isUndefined",
"meta": {
"added": [
"v0.11.5"
],
"deprecated": [
"v4.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use `value === undefined` instead.",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`object` {any}",
"name": "object",
"type": "any"
}
]
}
],
"desc": "Returns true
if the given object
is undefined
. Otherwise, returns false
.
const util = require('node:util');\n\nconst foo = undefined;\nutil.isUndefined(5);\n// Returns: false\nutil.isUndefined(foo);\n// Returns: true\nutil.isUndefined(null);\n// Returns: false\n
"
},
{
"textRaw": "`util.log(string)`",
"type": "method",
"name": "log",
"meta": {
"added": [
"v0.3.0"
],
"deprecated": [
"v6.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use a third party module instead.",
"signatures": [
{
"params": [
{
"textRaw": "`string` {string}",
"name": "string",
"type": "string"
}
]
}
],
"desc": "The util.log()
method prints the given string
to stdout
with an included\ntimestamp.
const util = require('node:util');\n\nutil.log('Timestamped message.');\n
"
}
],
"type": "module",
"displayName": "Deprecated APIs"
}
],
"type": "module",
"displayName": "Util",
"source": "doc/api/util.md"
},
{
"textRaw": "V8",
"name": "v8",
"introduced_in": "v4.0.0",
"desc": "Source Code: lib/v8.js
\nThe node:v8
module exposes APIs that are specific to the version of V8\nbuilt into the Node.js binary. It can be accessed using:
const v8 = require('node:v8');\n
",
"methods": [
{
"textRaw": "`v8.cachedDataVersionTag()`",
"type": "method",
"name": "cachedDataVersionTag",
"meta": {
"added": [
"v8.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": []
}
],
"desc": "Returns an integer representing a version tag derived from the V8 version,\ncommand-line flags, and detected CPU features. This is useful for determining\nwhether a vm.Script
cachedData
buffer is compatible with this instance\nof V8.
console.log(v8.cachedDataVersionTag()); // 3947234607\n// The value returned by v8.cachedDataVersionTag() is derived from the V8\n// version, command-line flags, and detected CPU features. Test that the value\n// does indeed update when flags are toggled.\nv8.setFlagsFromString('--allow_natives_syntax');\nconsole.log(v8.cachedDataVersionTag()); // 183726201\n
"
},
{
"textRaw": "`v8.getHeapCodeStatistics()`",
"type": "method",
"name": "getHeapCodeStatistics",
"meta": {
"added": [
"v12.8.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Get statistics about code and its metadata in the heap, see V8\nGetHeapCodeAndMetadataStatistics
API. Returns an object with the\nfollowing properties:
code_and_metadata_size
<number>bytecode_and_metadata_size
<number>external_script_source_size
<number>cpu_profiler_metadata_size
<number>{\n code_and_metadata_size: 212208,\n bytecode_and_metadata_size: 161368,\n external_script_source_size: 1410794,\n cpu_profiler_metadata_size: 0,\n}\n
"
},
{
"textRaw": "`v8.getHeapSnapshot([options])`",
"type": "method",
"name": "getHeapSnapshot",
"meta": {
"added": [
"v11.13.0"
],
"changes": [
{
"version": "v19.1.0",
"pr-url": "https://github.com/nodejs/node/pull/44989",
"description": "Support options to configure the heap snapshot."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {stream.Readable} A Readable containing the V8 heap snapshot.",
"name": "return",
"type": "stream.Readable",
"desc": "A Readable containing the V8 heap snapshot."
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`exposeInternals` {boolean} If true, expose internals in the heap snapshot. **Default:** `false`.",
"name": "exposeInternals",
"type": "boolean",
"default": "`false`",
"desc": "If true, expose internals in the heap snapshot."
},
{
"textRaw": "`exposeNumericValues` {boolean} If true, expose numeric values in artificial fields. **Default:** `false`.",
"name": "exposeNumericValues",
"type": "boolean",
"default": "`false`",
"desc": "If true, expose numeric values in artificial fields."
}
]
}
]
}
],
"desc": "Generates a snapshot of the current V8 heap and returns a Readable\nStream that may be used to read the JSON serialized representation.\nThis JSON stream format is intended to be used with tools such as\nChrome DevTools. The JSON schema is undocumented and specific to the\nV8 engine. Therefore, the schema may change from one version of V8 to the next.
\nCreating a heap snapshot requires memory about twice the size of the heap at\nthe time the snapshot is created. This results in the risk of OOM killers\nterminating the process.
\nGenerating a snapshot is a synchronous operation which blocks the event loop\nfor a duration depending on the heap size.
\n// Print heap snapshot to the console\nconst v8 = require('node:v8');\nconst stream = v8.getHeapSnapshot();\nstream.pipe(process.stdout);\n
"
},
{
"textRaw": "`v8.getHeapSpaceStatistics()`",
"type": "method",
"name": "getHeapSpaceStatistics",
"meta": {
"added": [
"v6.0.0"
],
"changes": [
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10186",
"description": "Support values exceeding the 32-bit unsigned integer range."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object\\[]}",
"name": "return",
"type": "Object\\[]"
},
"params": []
}
],
"desc": "Returns statistics about the V8 heap spaces, i.e. the segments which make up\nthe V8 heap. Neither the ordering of heap spaces, nor the availability of a\nheap space can be guaranteed as the statistics are provided via the V8\nGetHeapSpaceStatistics
function and may change from one V8 version to the\nnext.
The value returned is an array of objects containing the following properties:
\nspace_name
<string>space_size
<number>space_used_size
<number>space_available_size
<number>physical_space_size
<number>[\n {\n \"space_name\": \"new_space\",\n \"space_size\": 2063872,\n \"space_used_size\": 951112,\n \"space_available_size\": 80824,\n \"physical_space_size\": 2063872\n },\n {\n \"space_name\": \"old_space\",\n \"space_size\": 3090560,\n \"space_used_size\": 2493792,\n \"space_available_size\": 0,\n \"physical_space_size\": 3090560\n },\n {\n \"space_name\": \"code_space\",\n \"space_size\": 1260160,\n \"space_used_size\": 644256,\n \"space_available_size\": 960,\n \"physical_space_size\": 1260160\n },\n {\n \"space_name\": \"map_space\",\n \"space_size\": 1094160,\n \"space_used_size\": 201608,\n \"space_available_size\": 0,\n \"physical_space_size\": 1094160\n },\n {\n \"space_name\": \"large_object_space\",\n \"space_size\": 0,\n \"space_used_size\": 0,\n \"space_available_size\": 1490980608,\n \"physical_space_size\": 0\n }\n]\n
"
},
{
"textRaw": "`v8.getHeapStatistics()`",
"type": "method",
"name": "getHeapStatistics",
"meta": {
"added": [
"v1.0.0"
],
"changes": [
{
"version": "v7.5.0",
"pr-url": "https://github.com/nodejs/node/pull/10186",
"description": "Support values exceeding the 32-bit unsigned integer range."
},
{
"version": "v7.2.0",
"pr-url": "https://github.com/nodejs/node/pull/8610",
"description": "Added `malloced_memory`, `peak_malloced_memory`, and `does_zap_garbage`."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": []
}
],
"desc": "Returns an object with the following properties:
\ntotal_heap_size
<number>total_heap_size_executable
<number>total_physical_size
<number>total_available_size
<number>used_heap_size
<number>heap_size_limit
<number>malloced_memory
<number>peak_malloced_memory
<number>does_zap_garbage
<number>number_of_native_contexts
<number>number_of_detached_contexts
<number>total_global_handles_size
<number>used_global_handles_size
<number>external_memory
<number>does_zap_garbage
is a 0/1 boolean, which signifies whether the\n--zap_code_space
option is enabled or not. This makes V8 overwrite heap\ngarbage with a bit pattern. The RSS footprint (resident set size) gets bigger\nbecause it continuously touches all heap pages and that makes them less likely\nto get swapped out by the operating system.
number_of_native_contexts
The value of native_context is the number of the\ntop-level contexts currently active. Increase of this number over time indicates\na memory leak.
number_of_detached_contexts
The value of detached_context is the number\nof contexts that were detached and not yet garbage collected. This number\nbeing non-zero indicates a potential memory leak.
total_global_handles_size
The value of total_global_handles_size is the\ntotal memory size of V8 global handles.
used_global_handles_size
The value of used_global_handles_size is the\nused memory size of V8 global handles.
external_memory
The value of external_memory is the memory size of array\nbuffers and external strings.
{\n total_heap_size: 7326976,\n total_heap_size_executable: 4194304,\n total_physical_size: 7326976,\n total_available_size: 1152656,\n used_heap_size: 3476208,\n heap_size_limit: 1535115264,\n malloced_memory: 16384,\n peak_malloced_memory: 1127496,\n does_zap_garbage: 0,\n number_of_native_contexts: 1,\n number_of_detached_contexts: 0,\n total_global_handles_size: 8192,\n used_global_handles_size: 3296,\n external_memory: 318824\n}\n
"
},
{
"textRaw": "`v8.setFlagsFromString(flags)`",
"type": "method",
"name": "setFlagsFromString",
"meta": {
"added": [
"v1.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`flags` {string}",
"name": "flags",
"type": "string"
}
]
}
],
"desc": "The v8.setFlagsFromString()
method can be used to programmatically set\nV8 command-line flags. This method should be used with care. Changing settings\nafter the VM has started may result in unpredictable behavior, including\ncrashes and data loss; or it may simply do nothing.
The V8 options available for a version of Node.js may be determined by running\nnode --v8-options
.
Usage:
\n// Print GC events to stdout for one minute.\nconst v8 = require('node:v8');\nv8.setFlagsFromString('--trace_gc');\nsetTimeout(() => { v8.setFlagsFromString('--notrace_gc'); }, 60e3);\n
"
},
{
"textRaw": "`v8.stopCoverage()`",
"type": "method",
"name": "stopCoverage",
"meta": {
"added": [
"v15.1.0",
"v14.18.0",
"v12.22.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "The v8.stopCoverage()
method allows the user to stop the coverage collection\nstarted by NODE_V8_COVERAGE
, so that V8 can release the execution count\nrecords and optimize code. This can be used in conjunction with\nv8.takeCoverage()
if the user wants to collect the coverage on demand.
The v8.takeCoverage()
method allows the user to write the coverage started by\nNODE_V8_COVERAGE
to disk on demand. This method can be invoked multiple\ntimes during the lifetime of the process. Each time the execution counter will\nbe reset and a new coverage report will be written to the directory specified\nby NODE_V8_COVERAGE
.
When the process is about to exit, one last coverage will still be written to\ndisk unless v8.stopCoverage()
is invoked before the process exits.
Generates a snapshot of the current V8 heap and writes it to a JSON\nfile. This file is intended to be used with tools such as Chrome\nDevTools. The JSON schema is undocumented and specific to the V8\nengine, and may change from one version of V8 to the next.
\nA heap snapshot is specific to a single V8 isolate. When using\nworker threads, a heap snapshot generated from the main thread will\nnot contain any information about the workers, and vice versa.
\nCreating a heap snapshot requires memory about twice the size of the heap at\nthe time the snapshot is created. This results in the risk of OOM killers\nterminating the process.
\nGenerating a snapshot is a synchronous operation which blocks the event loop\nfor a duration depending on the heap size.
\nconst { writeHeapSnapshot } = require('node:v8');\nconst {\n Worker,\n isMainThread,\n parentPort,\n} = require('node:worker_threads');\n\nif (isMainThread) {\n const worker = new Worker(__filename);\n\n worker.once('message', (filename) => {\n console.log(`worker heapdump: ${filename}`);\n // Now get a heapdump for the main thread.\n console.log(`main thread heapdump: ${writeHeapSnapshot()}`);\n });\n\n // Tell the worker to create a heapdump.\n worker.postMessage('heapdump');\n} else {\n parentPort.once('message', (message) => {\n if (message === 'heapdump') {\n // Generate a heapdump for the worker\n // and return the filename to the parent.\n parentPort.postMessage(writeHeapSnapshot());\n }\n });\n}\n
"
},
{
"textRaw": "`v8.setHeapSnapshotNearHeapLimit(limit)`",
"type": "method",
"name": "setHeapSnapshotNearHeapLimit",
"meta": {
"added": [
"v18.10.0",
"v16.18.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"params": [
{
"textRaw": "`limit` {integer}",
"name": "limit",
"type": "integer"
}
]
}
],
"desc": "The API is a no-op if --heapsnapshot-near-heap-limit
is already set from the\ncommand line or the API is called more than once. limit
must be a positive\ninteger. See --heapsnapshot-near-heap-limit
for more information.
The serialization API provides means of serializing JavaScript values in a way\nthat is compatible with the HTML structured clone algorithm.
\nThe format is backward-compatible (i.e. safe to store to disk).\nEqual JavaScript values may result in different serialized output.
", "methods": [ { "textRaw": "`v8.serialize(value)`", "type": "method", "name": "serialize", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer}", "name": "return", "type": "Buffer" }, "params": [ { "textRaw": "`value` {any}", "name": "value", "type": "any" } ] } ], "desc": "Uses a DefaultSerializer
to serialize value
into a buffer.
ERR_BUFFER_TOO_LARGE
will be thrown when trying to\nserialize a huge object which requires buffer\nlarger than buffer.constants.MAX_LENGTH
.
Uses a DefaultDeserializer
with default options to read a JS value\nfrom a buffer.
Writes out a header, which includes the serialization format version.
" }, { "textRaw": "`serializer.writeValue(value)`", "type": "method", "name": "writeValue", "signatures": [ { "params": [ { "textRaw": "`value` {any}", "name": "value", "type": "any" } ] } ], "desc": "Serializes a JavaScript value and adds the serialized representation to the\ninternal buffer.
\nThis throws an error if value
cannot be serialized.
Returns the stored internal buffer. This serializer should not be used once\nthe buffer is released. Calling this method results in undefined behavior\nif a previous write has failed.
" }, { "textRaw": "`serializer.transferArrayBuffer(id, arrayBuffer)`", "type": "method", "name": "transferArrayBuffer", "signatures": [ { "params": [ { "textRaw": "`id` {integer} A 32-bit unsigned integer.", "name": "id", "type": "integer", "desc": "A 32-bit unsigned integer." }, { "textRaw": "`arrayBuffer` {ArrayBuffer} An `ArrayBuffer` instance.", "name": "arrayBuffer", "type": "ArrayBuffer", "desc": "An `ArrayBuffer` instance." } ] } ], "desc": "Marks an ArrayBuffer
as having its contents transferred out of band.\nPass the corresponding ArrayBuffer
in the deserializing context to\ndeserializer.transferArrayBuffer()
.
Write a raw 32-bit unsigned integer.\nFor use inside of a custom serializer._writeHostObject()
.
Write a raw 64-bit unsigned integer, split into high and low 32-bit parts.\nFor use inside of a custom serializer._writeHostObject()
.
Write a JS number
value.\nFor use inside of a custom serializer._writeHostObject()
.
Write raw bytes into the serializer's internal buffer. The deserializer\nwill require a way to compute the length of the buffer.\nFor use inside of a custom serializer._writeHostObject()
.
This method is called to write some kind of host object, i.e. an object created\nby native C++ bindings. If it is not possible to serialize object
, a suitable\nexception should be thrown.
This method is not present on the Serializer
class itself but can be provided\nby subclasses.
This method is called to generate error objects that will be thrown when an\nobject can not be cloned.
\nThis method defaults to the Error
constructor and can be overridden on\nsubclasses.
This method is called when the serializer is going to serialize a\nSharedArrayBuffer
object. It must return an unsigned 32-bit integer ID for\nthe object, using the same ID if this SharedArrayBuffer
has already been\nserialized. When deserializing, this ID will be passed to\ndeserializer.transferArrayBuffer()
.
If the object cannot be serialized, an exception should be thrown.
\nThis method is not present on the Serializer
class itself but can be provided\nby subclasses.
Indicate whether to treat TypedArray
and DataView
objects as\nhost objects, i.e. pass them to serializer._writeHostObject()
.
Creates a new Serializer
object.
Reads and validates a header (including the format version).\nMay, for example, reject an invalid or unsupported wire format. In that case,\nan Error
is thrown.
Deserializes a JavaScript value from the buffer and returns it.
" }, { "textRaw": "`deserializer.transferArrayBuffer(id, arrayBuffer)`", "type": "method", "name": "transferArrayBuffer", "signatures": [ { "params": [ { "textRaw": "`id` {integer} A 32-bit unsigned integer.", "name": "id", "type": "integer", "desc": "A 32-bit unsigned integer." }, { "textRaw": "`arrayBuffer` {ArrayBuffer|SharedArrayBuffer} An `ArrayBuffer` instance.", "name": "arrayBuffer", "type": "ArrayBuffer|SharedArrayBuffer", "desc": "An `ArrayBuffer` instance." } ] } ], "desc": "Marks an ArrayBuffer
as having its contents transferred out of band.\nPass the corresponding ArrayBuffer
in the serializing context to\nserializer.transferArrayBuffer()
(or return the id
from\nserializer._getSharedArrayBufferId()
in the case of SharedArrayBuffer
s).
Reads the underlying wire format version. Likely mostly to be useful to\nlegacy code reading old wire format versions. May not be called before\n.readHeader()
.
Read a raw 32-bit unsigned integer and return it.\nFor use inside of a custom deserializer._readHostObject()
.
Read a raw 64-bit unsigned integer and return it as an array [hi, lo]
\nwith two 32-bit unsigned integer entries.\nFor use inside of a custom deserializer._readHostObject()
.
Read a JS number
value.\nFor use inside of a custom deserializer._readHostObject()
.
Read raw bytes from the deserializer's internal buffer. The length
parameter\nmust correspond to the length of the buffer that was passed to\nserializer.writeRawBytes()
.\nFor use inside of a custom deserializer._readHostObject()
.
This method is called to read some kind of host object, i.e. an object that is\ncreated by native C++ bindings. If it is not possible to deserialize the data,\na suitable exception should be thrown.
\nThis method is not present on the Deserializer
class itself but can be\nprovided by subclasses.
Creates a new Deserializer
object.
A subclass of Serializer
that serializes TypedArray
\n(in particular Buffer
) and DataView
objects as host objects, and only\nstores the part of their underlying ArrayBuffer
s that they are referring to.
A subclass of Deserializer
corresponding to the format written by\nDefaultSerializer
.
The promiseHooks
interface can be used to track promise lifecycle events.\nTo track all async activity, see async_hooks
which internally uses this\nmodule to produce promise lifecycle events in addition to events for other\nasync resources. For request context management, see AsyncLocalStorage
.
import { promiseHooks } from 'node:v8';\n\n// There are four lifecycle events produced by promises:\n\n// The `init` event represents the creation of a promise. This could be a\n// direct creation such as with `new Promise(...)` or a continuation such\n// as `then()` or `catch()`. It also happens whenever an async function is\n// called or does an `await`. If a continuation promise is created, the\n// `parent` will be the promise it is a continuation from.\nfunction init(promise, parent) {\n console.log('a promise was created', { promise, parent });\n}\n\n// The `settled` event happens when a promise receives a resolution or\n// rejection value. This may happen synchronously such as when using\n// `Promise.resolve()` on non-promise input.\nfunction settled(promise) {\n console.log('a promise resolved or rejected', { promise });\n}\n\n// The `before` event runs immediately before a `then()` or `catch()` handler\n// runs or an `await` resumes execution.\nfunction before(promise) {\n console.log('a promise is about to call a then handler', { promise });\n}\n\n// The `after` event runs immediately after a `then()` handler runs or when\n// an `await` begins after resuming from another.\nfunction after(promise) {\n console.log('a promise is done calling a then handler', { promise });\n}\n\n// Lifecycle hooks may be started and stopped individually\nconst stopWatchingInits = promiseHooks.onInit(init);\nconst stopWatchingSettleds = promiseHooks.onSettled(settled);\nconst stopWatchingBefores = promiseHooks.onBefore(before);\nconst stopWatchingAfters = promiseHooks.onAfter(after);\n\n// Or they may be started and stopped in groups\nconst stopHookSet = promiseHooks.createHook({\n init,\n settled,\n before,\n after,\n});\n\n// To stop a hook, call the function returned at its creation.\nstopWatchingInits();\nstopWatchingSettleds();\nstopWatchingBefores();\nstopWatchingAfters();\nstopHookSet();\n
",
"methods": [
{
"textRaw": "`promiseHooks.onInit(init)`",
"type": "method",
"name": "onInit",
"meta": {
"added": [
"v17.1.0",
"v16.14.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} Call to stop the hook.",
"name": "return",
"type": "Function",
"desc": "Call to stop the hook."
},
"params": [
{
"textRaw": "`init` {Function} The [`init` callback][] to call when a promise is created.",
"name": "init",
"type": "Function",
"desc": "The [`init` callback][] to call when a promise is created."
}
]
}
],
"desc": "The init
hook must be a plain function. Providing an async function will\nthrow as it would produce an infinite microtask loop.
import { promiseHooks } from 'node:v8';\n\nconst stop = promiseHooks.onInit((promise, parent) => {});\n
\nconst { promiseHooks } = require('node:v8');\n\nconst stop = promiseHooks.onInit((promise, parent) => {});\n
"
},
{
"textRaw": "`promiseHooks.onSettled(settled)`",
"type": "method",
"name": "onSettled",
"meta": {
"added": [
"v17.1.0",
"v16.14.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} Call to stop the hook.",
"name": "return",
"type": "Function",
"desc": "Call to stop the hook."
},
"params": [
{
"textRaw": "`settled` {Function} The [`settled` callback][] to call when a promise is resolved or rejected.",
"name": "settled",
"type": "Function",
"desc": "The [`settled` callback][] to call when a promise is resolved or rejected."
}
]
}
],
"desc": "The settled
hook must be a plain function. Providing an async function will\nthrow as it would produce an infinite microtask loop.
import { promiseHooks } from 'node:v8';\n\nconst stop = promiseHooks.onSettled((promise) => {});\n
\nconst { promiseHooks } = require('node:v8');\n\nconst stop = promiseHooks.onSettled((promise) => {});\n
"
},
{
"textRaw": "`promiseHooks.onBefore(before)`",
"type": "method",
"name": "onBefore",
"meta": {
"added": [
"v17.1.0",
"v16.14.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} Call to stop the hook.",
"name": "return",
"type": "Function",
"desc": "Call to stop the hook."
},
"params": [
{
"textRaw": "`before` {Function} The [`before` callback][] to call before a promise continuation executes.",
"name": "before",
"type": "Function",
"desc": "The [`before` callback][] to call before a promise continuation executes."
}
]
}
],
"desc": "The before
hook must be a plain function. Providing an async function will\nthrow as it would produce an infinite microtask loop.
import { promiseHooks } from 'node:v8';\n\nconst stop = promiseHooks.onBefore((promise) => {});\n
\nconst { promiseHooks } = require('node:v8');\n\nconst stop = promiseHooks.onBefore((promise) => {});\n
"
},
{
"textRaw": "`promiseHooks.onAfter(after)`",
"type": "method",
"name": "onAfter",
"meta": {
"added": [
"v17.1.0",
"v16.14.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} Call to stop the hook.",
"name": "return",
"type": "Function",
"desc": "Call to stop the hook."
},
"params": [
{
"textRaw": "`after` {Function} The [`after` callback][] to call after a promise continuation executes.",
"name": "after",
"type": "Function",
"desc": "The [`after` callback][] to call after a promise continuation executes."
}
]
}
],
"desc": "The after
hook must be a plain function. Providing an async function will\nthrow as it would produce an infinite microtask loop.
import { promiseHooks } from 'node:v8';\n\nconst stop = promiseHooks.onAfter((promise) => {});\n
\nconst { promiseHooks } = require('node:v8');\n\nconst stop = promiseHooks.onAfter((promise) => {});\n
"
},
{
"textRaw": "`promiseHooks.createHook(callbacks)`",
"type": "method",
"name": "createHook",
"meta": {
"added": [
"v17.1.0",
"v16.14.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Function} Used for disabling hooks",
"name": "return",
"type": "Function",
"desc": "Used for disabling hooks"
},
"params": [
{
"textRaw": "`callbacks` {Object} The [Hook Callbacks][] to register",
"name": "callbacks",
"type": "Object",
"desc": "The [Hook Callbacks][] to register",
"options": [
{
"textRaw": "`init` {Function} The [`init` callback][].",
"name": "init",
"type": "Function",
"desc": "The [`init` callback][]."
},
{
"textRaw": "`before` {Function} The [`before` callback][].",
"name": "before",
"type": "Function",
"desc": "The [`before` callback][]."
},
{
"textRaw": "`after` {Function} The [`after` callback][].",
"name": "after",
"type": "Function",
"desc": "The [`after` callback][]."
},
{
"textRaw": "`settled` {Function} The [`settled` callback][].",
"name": "settled",
"type": "Function",
"desc": "The [`settled` callback][]."
}
]
}
]
}
],
"desc": "The hook callbacks must be plain functions. Providing async functions will\nthrow as it would produce an infinite microtask loop.
\nRegisters functions to be called for different lifetime events of each promise.
\nThe callbacks init()
/before()
/after()
/settled()
are called for the\nrespective events during a promise's lifetime.
All callbacks are optional. For example, if only promise creation needs to\nbe tracked, then only the init
callback needs to be passed. The\nspecifics of all functions that can be passed to callbacks
is in the\nHook Callbacks section.
import { promiseHooks } from 'node:v8';\n\nconst stopAll = promiseHooks.createHook({\n init(promise, parent) {},\n});\n
\nconst { promiseHooks } = require('node:v8');\n\nconst stopAll = promiseHooks.createHook({\n init(promise, parent) {},\n});\n
"
}
],
"modules": [
{
"textRaw": "Hook callbacks",
"name": "hook_callbacks",
"desc": "Key events in the lifetime of a promise have been categorized into four areas:\ncreation of a promise, before/after a continuation handler is called or around\nan await, and when the promise resolves or rejects.
\nWhile these hooks are similar to those of async_hooks
they lack a\ndestroy
hook. Other types of async resources typically represent sockets or\nfile descriptors which have a distinct \"closed\" state to express the destroy
\nlifecycle event while promises remain usable for as long as code can still\nreach them. Garbage collection tracking is used to make promises fit into the\nasync_hooks
event model, however this tracking is very expensive and they may\nnot necessarily ever even be garbage collected.
Because promises are asynchronous resources whose lifecycle is tracked\nvia the promise hooks mechanism, the init()
, before()
, after()
, and\nsettled()
callbacks must not be async functions as they create more\npromises which would produce an infinite loop.
While this API is used to feed promise events into async_hooks
, the\nordering between the two is undefined. Both APIs are multi-tenant\nand therefore could produce events in any order relative to each other.
Called when a promise is constructed. This does not mean that corresponding\nbefore
/after
events will occur, only that the possibility exists. This will\nhappen if a promise is created without ever getting a continuation.
Called before a promise continuation executes. This can be in the form of\nthen()
, catch()
, or finally()
handlers or an await
resuming.
The before
callback will be called 0 to N times. The before
callback\nwill typically be called 0 times if no continuation was ever made for the\npromise. The before
callback may be called many times in the case where\nmany continuations have been made from the same promise.
Called immediately after a promise continuation executes. This may be after a\nthen()
, catch()
, or finally()
handler or before an await
after another\nawait
.
Called when the promise receives a resolution or rejection value. This may\noccur synchronously in the case of Promise.resolve()
or Promise.reject()
.
The v8.startupSnapshot
interface can be used to add serialization and\ndeserialization hooks for custom startup snapshots.
$ node --snapshot-blob snapshot.blob --build-snapshot entry.js\n# This launches a process with the snapshot\n$ node --snapshot-blob snapshot.blob\n
\nIn the example above, entry.js
can use methods from the v8.startupSnapshot
\ninterface to specify how to save information for custom objects in the snapshot\nduring serialization and how the information can be used to synchronize these\nobjects during deserialization of the snapshot. For example, if the entry.js
\ncontains the following script:
'use strict';\n\nconst fs = require('node:fs');\nconst zlib = require('node:zlib');\nconst path = require('node:path');\nconst assert = require('node:assert');\n\nconst v8 = require('node:v8');\n\nclass BookShelf {\n storage = new Map();\n\n // Reading a series of files from directory and store them into storage.\n constructor(directory, books) {\n for (const book of books) {\n this.storage.set(book, fs.readFileSync(path.join(directory, book)));\n }\n }\n\n static compressAll(shelf) {\n for (const [ book, content ] of shelf.storage) {\n shelf.storage.set(book, zlib.gzipSync(content));\n }\n }\n\n static decompressAll(shelf) {\n for (const [ book, content ] of shelf.storage) {\n shelf.storage.set(book, zlib.gunzipSync(content));\n }\n }\n}\n\n// __dirname here is where the snapshot script is placed\n// during snapshot building time.\nconst shelf = new BookShelf(__dirname, [\n 'book1.en_US.txt',\n 'book1.es_ES.txt',\n 'book2.zh_CN.txt',\n]);\n\nassert(v8.startupSnapshot.isBuildingSnapshot());\n// On snapshot serialization, compress the books to reduce size.\nv8.startupSnapshot.addSerializeCallback(BookShelf.compressAll, shelf);\n// On snapshot deserialization, decompress the books.\nv8.startupSnapshot.addDeserializeCallback(BookShelf.decompressAll, shelf);\nv8.startupSnapshot.setDeserializeMainFunction((shelf) => {\n // process.env and process.argv are refreshed during snapshot\n // deserialization.\n const lang = process.env.BOOK_LANG || 'en_US';\n const book = process.argv[1];\n const name = `${book}.${lang}.txt`;\n console.log(shelf.storage.get(name));\n}, shelf);\n
\nThe resulted binary will get print the data deserialized from the snapshot\nduring start up, using the refreshed process.env
and process.argv
of\nthe launched process:
$ BOOK_LANG=es_ES node --snapshot-blob snapshot.blob book1\n# Prints content of book1.es_ES.txt deserialized from the snapshot.\n
\nCurrently the application deserialized from a user-land snapshot cannot\nbe snapshotted again, so these APIs are only available to applications\nthat are not deserialized from a user-land snapshot.
", "methods": [ { "textRaw": "`v8.startupSnapshot.addSerializeCallback(callback[, data])`", "type": "method", "name": "addSerializeCallback", "meta": { "added": [ "v18.6.0", "v16.17.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function} Callback to be invoked before serialization.", "name": "callback", "type": "Function", "desc": "Callback to be invoked before serialization." }, { "textRaw": "`data` {any} Optional data that will be passed to the `callback` when it gets called.", "name": "data", "type": "any", "desc": "Optional data that will be passed to the `callback` when it gets called." } ] } ], "desc": "Add a callback that will be called when the Node.js instance is about to\nget serialized into a snapshot and exit. This can be used to release\nresources that should not or cannot be serialized or to convert user data\ninto a form more suitable for serialization.
\nCallbacks are run in the order in which they are added.
" }, { "textRaw": "`v8.startupSnapshot.addDeserializeCallback(callback[, data])`", "type": "method", "name": "addDeserializeCallback", "meta": { "added": [ "v18.6.0", "v16.17.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function} Callback to be invoked after the snapshot is deserialized.", "name": "callback", "type": "Function", "desc": "Callback to be invoked after the snapshot is deserialized." }, { "textRaw": "`data` {any} Optional data that will be passed to the `callback` when it gets called.", "name": "data", "type": "any", "desc": "Optional data that will be passed to the `callback` when it gets called." } ] } ], "desc": "Add a callback that will be called when the Node.js instance is deserialized\nfrom a snapshot. The callback
and the data
(if provided) will be\nserialized into the snapshot, they can be used to re-initialize the state\nof the application or to re-acquire resources that the application needs\nwhen the application is restarted from the snapshot.
Callbacks are run in the order in which they are added.
" }, { "textRaw": "`v8.startupSnapshot.setDeserializeMainFunction(callback[, data])`", "type": "method", "name": "setDeserializeMainFunction", "meta": { "added": [ "v18.6.0", "v16.17.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`callback` {Function} Callback to be invoked as the entry point after the snapshot is deserialized.", "name": "callback", "type": "Function", "desc": "Callback to be invoked as the entry point after the snapshot is deserialized." }, { "textRaw": "`data` {any} Optional data that will be passed to the `callback` when it gets called.", "name": "data", "type": "any", "desc": "Optional data that will be passed to the `callback` when it gets called." } ] } ], "desc": "This sets the entry point of the Node.js application when it is deserialized\nfrom a snapshot. This can be called only once in the snapshot building\nscript. If called, the deserialized application no longer needs an additional\nentry point script to start up and will simply invoke the callback along with\nthe deserialized data (if provided), otherwise an entry point script still\nneeds to be provided to the deserialized application.
" }, { "textRaw": "`v8.startupSnapshot.isBuildingSnapshot()`", "type": "method", "name": "isBuildingSnapshot", "meta": { "added": [ "v18.6.0", "v16.17.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [] } ], "desc": "Returns true if the Node.js instance is run to build a snapshot.
" } ], "type": "module", "displayName": "Startup Snapshot API" } ], "classes": [ { "textRaw": "Class: `v8.GCProfiler`", "type": "class", "name": "v8.GCProfiler", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "desc": "This API collects GC data in current thread.
", "methods": [ { "textRaw": "`profiler.start()`", "type": "method", "name": "start", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Start collecting GC data.
" }, { "textRaw": "`profiler.stop()`", "type": "method", "name": "stop", "meta": { "added": [ "v19.6.0", "v18.15.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Stop collecting GC data and return an object.The content of object\nis as follows.
\n{\n \"version\": 1,\n \"startTime\": 1674059033862,\n \"statistics\": [\n {\n \"gcType\": \"Scavenge\",\n \"beforeGC\": {\n \"heapStatistics\": {\n \"totalHeapSize\": 5005312,\n \"totalHeapSizeExecutable\": 524288,\n \"totalPhysicalSize\": 5226496,\n \"totalAvailableSize\": 4341325216,\n \"totalGlobalHandlesSize\": 8192,\n \"usedGlobalHandlesSize\": 2112,\n \"usedHeapSize\": 4883840,\n \"heapSizeLimit\": 4345298944,\n \"mallocedMemory\": 254128,\n \"externalMemory\": 225138,\n \"peakMallocedMemory\": 181760\n },\n \"heapSpaceStatistics\": [\n {\n \"spaceName\": \"read_only_space\",\n \"spaceSize\": 0,\n \"spaceUsedSize\": 0,\n \"spaceAvailableSize\": 0,\n \"physicalSpaceSize\": 0\n }\n ]\n },\n \"cost\": 1574.14,\n \"afterGC\": {\n \"heapStatistics\": {\n \"totalHeapSize\": 6053888,\n \"totalHeapSizeExecutable\": 524288,\n \"totalPhysicalSize\": 5500928,\n \"totalAvailableSize\": 4341101384,\n \"totalGlobalHandlesSize\": 8192,\n \"usedGlobalHandlesSize\": 2112,\n \"usedHeapSize\": 4059096,\n \"heapSizeLimit\": 4345298944,\n \"mallocedMemory\": 254128,\n \"externalMemory\": 225138,\n \"peakMallocedMemory\": 181760\n },\n \"heapSpaceStatistics\": [\n {\n \"spaceName\": \"read_only_space\",\n \"spaceSize\": 0,\n \"spaceUsedSize\": 0,\n \"spaceAvailableSize\": 0,\n \"physicalSpaceSize\": 0\n }\n ]\n }\n }\n ],\n \"endTime\": 1674059036865\n}\n
\nHere's an example.
\nconst { GCProfiler } = require('v8');\nconst profiler = new GCProfiler();\nprofiler.start();\nsetTimeout(() => {\n console.log(profiler.stop());\n}, 1000);\n
"
}
],
"signatures": [
{
"params": [],
"desc": "Create a new instance of the v8.GCProfiler
class.
Source Code: lib/vm.js
\nThe node:vm
module enables compiling and running code within V8 Virtual\nMachine contexts.
The node:vm
module is not a security\nmechanism. Do not use it to run untrusted code.
JavaScript code can be compiled and run immediately or\ncompiled, saved, and run later.
\nA common use case is to run the code in a different V8 Context. This means\ninvoked code has a different global object than the invoking code.
\nOne can provide the context by contextifying an\nobject. The invoked code treats any property in the context like a\nglobal variable. Any changes to global variables caused by the invoked\ncode are reflected in the context object.
\nconst vm = require('node:vm');\n\nconst x = 1;\n\nconst context = { x: 2 };\nvm.createContext(context); // Contextify the object.\n\nconst code = 'x += 40; var y = 17;';\n// `x` and `y` are global variables in the context.\n// Initially, x has the value 2 because that is the value of context.x.\nvm.runInContext(code, context);\n\nconsole.log(context.x); // 42\nconsole.log(context.y); // 17\n\nconsole.log(x); // 1; y is not defined.\n
",
"classes": [
{
"textRaw": "Class: `vm.Script`",
"type": "class",
"name": "vm.Script",
"meta": {
"added": [
"v0.3.1"
],
"changes": []
},
"desc": "Instances of the vm.Script
class contain precompiled scripts that can be\nexecuted in specific contexts.
When cachedData
is supplied to create the vm.Script
, this value will be set\nto either true
or false
depending on acceptance of the data by V8.\nOtherwise the value is undefined
.
When the script is compiled from a source that contains a source map magic\ncomment, this property will be set to the URL of the source map.
\nimport vm from 'node:vm';\n\nconst script = new vm.Script(`\nfunction myFunc() {}\n//# sourceMappingURL=sourcemap.json\n`);\n\nconsole.log(script.sourceMapURL);\n// Prints: sourcemap.json\n
\nconst vm = require('node:vm');\n\nconst script = new vm.Script(`\nfunction myFunc() {}\n//# sourceMappingURL=sourcemap.json\n`);\n\nconsole.log(script.sourceMapURL);\n// Prints: sourcemap.json\n
"
}
],
"methods": [
{
"textRaw": "`script.createCachedData()`",
"type": "method",
"name": "createCachedData",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer}",
"name": "return",
"type": "Buffer"
},
"params": []
}
],
"desc": "Creates a code cache that can be used with the Script
constructor's\ncachedData
option. Returns a Buffer
. This method may be called at any\ntime and any number of times.
The code cache of the Script
doesn't contain any JavaScript observable\nstates. The code cache is safe to be saved along side the script source and\nused to construct new Script
instances multiple times.
Functions in the Script
source can be marked as lazily compiled and they are\nnot compiled at construction of the Script
. These functions are going to be\ncompiled when they are invoked the first time. The code cache serializes the\nmetadata that V8 currently knows about the Script
that it can use to speed up\nfuture compilations.
const script = new vm.Script(`\nfunction add(a, b) {\n return a + b;\n}\n\nconst x = add(1, 2);\n`);\n\nconst cacheWithoutAdd = script.createCachedData();\n// In `cacheWithoutAdd` the function `add()` is marked for full compilation\n// upon invocation.\n\nscript.runInThisContext();\n\nconst cacheWithAdd = script.createCachedData();\n// `cacheWithAdd` contains fully compiled function `add()`.\n
"
},
{
"textRaw": "`script.runInContext(contextifiedObject[, options])`",
"type": "method",
"name": "runInContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": [
{
"version": "v6.3.0",
"pr-url": "https://github.com/nodejs/node/pull/6635",
"description": "The `breakOnSigint` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {any} the result of the very last statement executed in the script.",
"name": "return",
"type": "any",
"desc": "the result of the very last statement executed in the script."
},
"params": [
{
"textRaw": "`contextifiedObject` {Object} A [contextified][] object as returned by the `vm.createContext()` method.",
"name": "contextifiedObject",
"type": "Object",
"desc": "A [contextified][] object as returned by the `vm.createContext()` method."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`displayErrors` {boolean} When `true`, if an [`Error`][] occurs while compiling the `code`, the line of code causing the error is attached to the stack trace. **Default:** `true`.",
"name": "displayErrors",
"type": "boolean",
"default": "`true`",
"desc": "When `true`, if an [`Error`][] occurs while compiling the `code`, the line of code causing the error is attached to the stack trace."
},
{
"textRaw": "`timeout` {integer} Specifies the number of milliseconds to execute `code` before terminating execution. If execution is terminated, an [`Error`][] will be thrown. This value must be a strictly positive integer.",
"name": "timeout",
"type": "integer",
"desc": "Specifies the number of milliseconds to execute `code` before terminating execution. If execution is terminated, an [`Error`][] will be thrown. This value must be a strictly positive integer."
},
{
"textRaw": "`breakOnSigint` {boolean} If `true`, receiving `SIGINT` (Ctrl+C) will terminate execution and throw an [`Error`][]. Existing handlers for the event that have been attached via `process.on('SIGINT')` are disabled during script execution, but continue to work after that. **Default:** `false`.",
"name": "breakOnSigint",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, receiving `SIGINT` (Ctrl+C) will terminate execution and throw an [`Error`][]. Existing handlers for the event that have been attached via `process.on('SIGINT')` are disabled during script execution, but continue to work after that."
}
]
}
]
}
],
"desc": "Runs the compiled code contained by the vm.Script
object within the given\ncontextifiedObject
and returns the result. Running code does not have access\nto local scope.
The following example compiles code that increments a global variable, sets\nthe value of another global variable, then execute the code multiple times.\nThe globals are contained in the context
object.
const vm = require('node:vm');\n\nconst context = {\n animal: 'cat',\n count: 2,\n};\n\nconst script = new vm.Script('count += 1; name = \"kitty\";');\n\nvm.createContext(context);\nfor (let i = 0; i < 10; ++i) {\n script.runInContext(context);\n}\n\nconsole.log(context);\n// Prints: { animal: 'cat', count: 12, name: 'kitty' }\n
\nUsing the timeout
or breakOnSigint
options will result in new event loops\nand corresponding threads being started, which have a non-zero performance\noverhead.
First contextifies the given contextObject
, runs the compiled code contained\nby the vm.Script
object within the created context, and returns the result.\nRunning code does not have access to local scope.
The following example compiles code that sets a global variable, then executes\nthe code multiple times in different contexts. The globals are set on and\ncontained within each individual context
.
const vm = require('node:vm');\n\nconst script = new vm.Script('globalVar = \"set\"');\n\nconst contexts = [{}, {}, {}];\ncontexts.forEach((context) => {\n script.runInNewContext(context);\n});\n\nconsole.log(contexts);\n// Prints: [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]\n
"
},
{
"textRaw": "`script.runInThisContext([options])`",
"type": "method",
"name": "runInThisContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": [
{
"version": "v6.3.0",
"pr-url": "https://github.com/nodejs/node/pull/6635",
"description": "The `breakOnSigint` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {any} the result of the very last statement executed in the script.",
"name": "return",
"type": "any",
"desc": "the result of the very last statement executed in the script."
},
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`displayErrors` {boolean} When `true`, if an [`Error`][] occurs while compiling the `code`, the line of code causing the error is attached to the stack trace. **Default:** `true`.",
"name": "displayErrors",
"type": "boolean",
"default": "`true`",
"desc": "When `true`, if an [`Error`][] occurs while compiling the `code`, the line of code causing the error is attached to the stack trace."
},
{
"textRaw": "`timeout` {integer} Specifies the number of milliseconds to execute `code` before terminating execution. If execution is terminated, an [`Error`][] will be thrown. This value must be a strictly positive integer.",
"name": "timeout",
"type": "integer",
"desc": "Specifies the number of milliseconds to execute `code` before terminating execution. If execution is terminated, an [`Error`][] will be thrown. This value must be a strictly positive integer."
},
{
"textRaw": "`breakOnSigint` {boolean} If `true`, receiving `SIGINT` (Ctrl+C) will terminate execution and throw an [`Error`][]. Existing handlers for the event that have been attached via `process.on('SIGINT')` are disabled during script execution, but continue to work after that. **Default:** `false`.",
"name": "breakOnSigint",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, receiving `SIGINT` (Ctrl+C) will terminate execution and throw an [`Error`][]. Existing handlers for the event that have been attached via `process.on('SIGINT')` are disabled during script execution, but continue to work after that."
}
]
}
]
}
],
"desc": "Runs the compiled code contained by the vm.Script
within the context of the\ncurrent global
object. Running code does not have access to local scope, but\ndoes have access to the current global
object.
The following example compiles code that increments a global
variable then\nexecutes that code multiple times:
const vm = require('node:vm');\n\nglobal.globalVar = 0;\n\nconst script = new vm.Script('globalVar += 1', { filename: 'myfile.vm' });\n\nfor (let i = 0; i < 1000; ++i) {\n script.runInThisContext();\n}\n\nconsole.log(globalVar);\n\n// 1000\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`code` {string} The JavaScript code to compile.",
"name": "code",
"type": "string",
"desc": "The JavaScript code to compile."
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script. **Default:** `'evalmachine.If options
is a string, then it specifies the filename.
Creating a new vm.Script
object compiles code
but does not run it. The\ncompiled vm.Script
can be run later multiple times. The code
is not bound to\nany global object; rather, it is bound before each run, just for that run.
This feature is only available with the --experimental-vm-modules
command\nflag enabled.
The vm.Module
class provides a low-level interface for using\nECMAScript modules in VM contexts. It is the counterpart of the vm.Script
\nclass that closely mirrors Module Records as defined in the ECMAScript\nspecification.
Unlike vm.Script
however, every vm.Module
object is bound to a context from\nits creation. Operations on vm.Module
objects are intrinsically asynchronous,\nin contrast with the synchronous nature of vm.Script
objects. The use of\n'async' functions can help with manipulating vm.Module
objects.
Using a vm.Module
object requires three distinct steps: creation/parsing,\nlinking, and evaluation. These three steps are illustrated in the following\nexample.
This implementation lies at a lower level than the ECMAScript Module\nloader. There is also no way to interact with the Loader yet, though\nsupport is planned.
\nimport vm from 'node:vm';\n\nconst contextifiedObject = vm.createContext({\n secret: 42,\n print: console.log,\n});\n\n// Step 1\n//\n// Create a Module by constructing a new `vm.SourceTextModule` object. This\n// parses the provided source text, throwing a `SyntaxError` if anything goes\n// wrong. By default, a Module is created in the top context. But here, we\n// specify `contextifiedObject` as the context this Module belongs to.\n//\n// Here, we attempt to obtain the default export from the module \"foo\", and\n// put it into local binding \"secret\".\n\nconst bar = new vm.SourceTextModule(`\n import s from 'foo';\n s;\n print(s);\n`, { context: contextifiedObject });\n\n// Step 2\n//\n// \"Link\" the imported dependencies of this Module to it.\n//\n// The provided linking callback (the \"linker\") accepts two arguments: the\n// parent module (`bar` in this case) and the string that is the specifier of\n// the imported module. The callback is expected to return a Module that\n// corresponds to the provided specifier, with certain requirements documented\n// in `module.link()`.\n//\n// If linking has not started for the returned Module, the same linker\n// callback will be called on the returned Module.\n//\n// Even top-level Modules without dependencies must be explicitly linked. The\n// callback provided would never be called, however.\n//\n// The link() method returns a Promise that will be resolved when all the\n// Promises returned by the linker resolve.\n//\n// Note: This is a contrived example in that the linker function creates a new\n// \"foo\" module every time it is called. In a full-fledged module system, a\n// cache would probably be used to avoid duplicated modules.\n\nasync function linker(specifier, referencingModule) {\n if (specifier === 'foo') {\n return new vm.SourceTextModule(`\n // The \"secret\" variable refers to the global variable we added to\n // \"contextifiedObject\" when creating the context.\n export default secret;\n `, { context: referencingModule.context });\n\n // Using `contextifiedObject` instead of `referencingModule.context`\n // here would work as well.\n }\n throw new Error(`Unable to resolve dependency: ${specifier}`);\n}\nawait bar.link(linker);\n\n// Step 3\n//\n// Evaluate the Module. The evaluate() method returns a promise which will\n// resolve after the module has finished evaluating.\n\n// Prints 42.\nawait bar.evaluate();\n
\nconst vm = require('node:vm');\n\nconst contextifiedObject = vm.createContext({\n secret: 42,\n print: console.log,\n});\n\n(async () => {\n // Step 1\n //\n // Create a Module by constructing a new `vm.SourceTextModule` object. This\n // parses the provided source text, throwing a `SyntaxError` if anything goes\n // wrong. By default, a Module is created in the top context. But here, we\n // specify `contextifiedObject` as the context this Module belongs to.\n //\n // Here, we attempt to obtain the default export from the module \"foo\", and\n // put it into local binding \"secret\".\n\n const bar = new vm.SourceTextModule(`\n import s from 'foo';\n s;\n print(s);\n `, { context: contextifiedObject });\n\n // Step 2\n //\n // \"Link\" the imported dependencies of this Module to it.\n //\n // The provided linking callback (the \"linker\") accepts two arguments: the\n // parent module (`bar` in this case) and the string that is the specifier of\n // the imported module. The callback is expected to return a Module that\n // corresponds to the provided specifier, with certain requirements documented\n // in `module.link()`.\n //\n // If linking has not started for the returned Module, the same linker\n // callback will be called on the returned Module.\n //\n // Even top-level Modules without dependencies must be explicitly linked. The\n // callback provided would never be called, however.\n //\n // The link() method returns a Promise that will be resolved when all the\n // Promises returned by the linker resolve.\n //\n // Note: This is a contrived example in that the linker function creates a new\n // \"foo\" module every time it is called. In a full-fledged module system, a\n // cache would probably be used to avoid duplicated modules.\n\n async function linker(specifier, referencingModule) {\n if (specifier === 'foo') {\n return new vm.SourceTextModule(`\n // The \"secret\" variable refers to the global variable we added to\n // \"contextifiedObject\" when creating the context.\n export default secret;\n `, { context: referencingModule.context });\n\n // Using `contextifiedObject` instead of `referencingModule.context`\n // here would work as well.\n }\n throw new Error(`Unable to resolve dependency: ${specifier}`);\n }\n await bar.link(linker);\n\n // Step 3\n //\n // Evaluate the Module. The evaluate() method returns a promise which will\n // resolve after the module has finished evaluating.\n\n // Prints 42.\n await bar.evaluate();\n})();\n
",
"properties": [
{
"textRaw": "`dependencySpecifiers` {string\\[]}",
"type": "string\\[]",
"name": "dependencySpecifiers",
"desc": "The specifiers of all dependencies of this module. The returned array is frozen\nto disallow any changes to it.
\nCorresponds to the [[RequestedModules]]
field of Cyclic Module Records in\nthe ECMAScript specification.
If the module.status
is 'errored'
, this property contains the exception\nthrown by the module during evaluation. If the status is anything else,\naccessing this property will result in a thrown exception.
The value undefined
cannot be used for cases where there is not a thrown\nexception due to possible ambiguity with throw undefined;
.
Corresponds to the [[EvaluationError]]
field of Cyclic Module Records\nin the ECMAScript specification.
The identifier of the current module, as set in the constructor.
" }, { "textRaw": "`namespace` {Object}", "type": "Object", "name": "namespace", "desc": "The namespace object of the module. This is only available after linking\n(module.link()
) has completed.
Corresponds to the GetModuleNamespace abstract operation in the ECMAScript\nspecification.
" }, { "textRaw": "`status` {string}", "type": "string", "name": "status", "desc": "The current status of the module. Will be one of:
\n'unlinked'
: module.link()
has not yet been called.
'linking'
: module.link()
has been called, but not all Promises returned\nby the linker function have been resolved yet.
'linked'
: The module has been linked successfully, and all of its\ndependencies are linked, but module.evaluate()
has not yet been called.
'evaluating'
: The module is being evaluated through a module.evaluate()
on\nitself or a parent module.
'evaluated'
: The module has been successfully evaluated.
'errored'
: The module has been evaluated, but an exception was thrown.
Other than 'errored'
, this status string corresponds to the specification's\nCyclic Module Record's [[Status]]
field. 'errored'
corresponds to\n'evaluated'
in the specification, but with [[EvaluationError]]
set to a\nvalue that is not undefined
.
Evaluate the module.
\nThis must be called after the module has been linked; otherwise it will reject.\nIt could be called also when the module has already been evaluated, in which\ncase it will either do nothing if the initial evaluation ended in success\n(module.status
is 'evaluated'
) or it will re-throw the exception that the\ninitial evaluation resulted in (module.status
is 'errored'
).
This method cannot be called while the module is being evaluated\n(module.status
is 'evaluating'
).
Corresponds to the Evaluate() concrete method field of Cyclic Module\nRecords in the ECMAScript specification.
" }, { "textRaw": "`module.link(linker)`", "type": "method", "name": "link", "meta": { "changes": [ { "version": "v21.1.0", "pr-url": "https://github.com/nodejs/node/pull/50141", "description": "The option `extra.assert` is renamed to `extra.attributes`. The former name is still provided for backward compatibility." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`linker` {Function}", "name": "linker", "type": "Function", "options": [ { "textRaw": "`specifier` {string} The specifier of the requested module:```mjs import foo from 'foo'; // ^^^^^ the module specifier ```", "name": "specifier", "type": "string", "desc": "The specifier of the requested module:```mjs import foo from 'foo'; // ^^^^^ the module specifier ```" }, { "textRaw": "`referencingModule` {vm.Module} The `Module` object `link()` is called on.", "name": "referencingModule", "type": "vm.Module", "desc": "The `Module` object `link()` is called on." }, { "textRaw": "`extra` {Object}", "name": "extra", "type": "Object", "options": [ { "textRaw": "`attributes` {Object} The data from the attribute:```mjs import foo from 'foo' with { name: 'value' }; // ^^^^^^^^^^^^^^^^^ the attribute ```Per ECMA-262, hosts are expected to trigger an error if an unsupported attribute is present.", "name": "attributes", "type": "Object", "desc": "The data from the attribute:```mjs import foo from 'foo' with { name: 'value' }; // ^^^^^^^^^^^^^^^^^ the attribute ```Per ECMA-262, hosts are expected to trigger an error if an unsupported attribute is present." }, { "textRaw": "`assert` {Object} Alias for `extra.attributes`.", "name": "assert", "type": "Object", "desc": "Alias for `extra.attributes`." } ] }, { "textRaw": "Returns: {vm.Module|Promise}", "name": "return", "type": "vm.Module|Promise" } ] } ] } ], "desc": "Link module dependencies. This method must be called before evaluation, and\ncan only be called once per module.
\nThe function is expected to return a Module
object or a Promise
that\neventually resolves to a Module
object. The returned Module
must satisfy the\nfollowing two invariants:
Module
.status
must not be 'errored'
.If the returned Module
's status
is 'unlinked'
, this method will be\nrecursively called on the returned Module
with the same provided linker
\nfunction.
link()
returns a Promise
that will either get resolved when all linking\ninstances resolve to a valid Module
, or rejected if the linker function either\nthrows an exception or returns an invalid Module
.
The linker function roughly corresponds to the implementation-defined\nHostResolveImportedModule abstract operation in the ECMAScript\nspecification, with a few key differences:
\nThe actual HostResolveImportedModule implementation used during module\nlinking is one that returns the modules linked during linking. Since at\nthat point all modules would have been fully linked already, the\nHostResolveImportedModule implementation is fully synchronous per\nspecification.
\nCorresponds to the Link() concrete method field of Cyclic Module\nRecords in the ECMAScript specification.
" } ] }, { "textRaw": "Class: `vm.SourceTextModule`", "type": "class", "name": "vm.SourceTextModule", "meta": { "added": [ "v9.6.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "desc": "This feature is only available with the --experimental-vm-modules
command\nflag enabled.
The vm.SourceTextModule
class provides the Source Text Module Record as\ndefined in the ECMAScript specification.
Creates a code cache that can be used with the SourceTextModule
constructor's\ncachedData
option. Returns a Buffer
. This method may be called any number\nof times before the module has been evaluated.
The code cache of the SourceTextModule
doesn't contain any JavaScript\nobservable states. The code cache is safe to be saved along side the script\nsource and used to construct new SourceTextModule
instances multiple times.
Functions in the SourceTextModule
source can be marked as lazily compiled\nand they are not compiled at construction of the SourceTextModule
. These\nfunctions are going to be compiled when they are invoked the first time. The\ncode cache serializes the metadata that V8 currently knows about the\nSourceTextModule
that it can use to speed up future compilations.
// Create an initial module\nconst module = new vm.SourceTextModule('const a = 1;');\n\n// Create cached data from this module\nconst cachedData = module.createCachedData();\n\n// Create a new module using the cached data. The code must be the same.\nconst module2 = new vm.SourceTextModule('const a = 1;', { cachedData });\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`code` {string} JavaScript Module code to parse",
"name": "code",
"type": "string",
"desc": "JavaScript Module code to parse"
},
{
"textRaw": "`options`",
"name": "options",
"options": [
{
"textRaw": "`identifier` {string} String used in stack traces. **Default:** `'vm:module(i)'` where `i` is a context-specific ascending index.",
"name": "identifier",
"type": "string",
"default": "`'vm:module(i)'` where `i` is a context-specific ascending index",
"desc": "String used in stack traces."
},
{
"textRaw": "`cachedData` {Buffer|TypedArray|DataView} Provides an optional `Buffer` or `TypedArray`, or `DataView` with V8's code cache data for the supplied source. The `code` must be the same as the module from which this `cachedData` was created.",
"name": "cachedData",
"type": "Buffer|TypedArray|DataView",
"desc": "Provides an optional `Buffer` or `TypedArray`, or `DataView` with V8's code cache data for the supplied source. The `code` must be the same as the module from which this `cachedData` was created."
},
{
"textRaw": "`context` {Object} The [contextified][] object as returned by the `vm.createContext()` method, to compile and evaluate this `Module` in. If no context is specified, the module is evaluated in the current execution context.",
"name": "context",
"type": "Object",
"desc": "The [contextified][] object as returned by the `vm.createContext()` method, to compile and evaluate this `Module` in. If no context is specified, the module is evaluated in the current execution context."
},
{
"textRaw": "`lineOffset` {integer} Specifies the line number offset that is displayed in stack traces produced by this `Module`. **Default:** `0`.",
"name": "lineOffset",
"type": "integer",
"default": "`0`",
"desc": "Specifies the line number offset that is displayed in stack traces produced by this `Module`."
},
{
"textRaw": "`columnOffset` {integer} Specifies the first-line column number offset that is displayed in stack traces produced by this `Module`. **Default:** `0`.",
"name": "columnOffset",
"type": "integer",
"default": "`0`",
"desc": "Specifies the first-line column number offset that is displayed in stack traces produced by this `Module`."
},
{
"textRaw": "`initializeImportMeta` {Function} Called during evaluation of this `Module` to initialize the `import.meta`.",
"name": "initializeImportMeta",
"type": "Function",
"desc": "Called during evaluation of this `Module` to initialize the `import.meta`.",
"options": [
{
"textRaw": "`meta` {import.meta}",
"name": "meta",
"type": "import.meta"
},
{
"textRaw": "`module` {vm.SourceTextModule}",
"name": "module",
"type": "vm.SourceTextModule"
}
]
},
{
"textRaw": "`importModuleDynamically` {Function} Used to specify the how the modules should be loaded during the evaluation of this module when `import()` is called. This option is part of the experimental modules API. We do not recommend using it in a production environment. For detailed information, see [Support of dynamic `import()` in compilation APIs][].",
"name": "importModuleDynamically",
"type": "Function",
"desc": "Used to specify the how the modules should be loaded during the evaluation of this module when `import()` is called. This option is part of the experimental modules API. We do not recommend using it in a production environment. For detailed information, see [Support of dynamic `import()` in compilation APIs][]."
}
]
}
],
"desc": "Creates a new SourceTextModule
instance.
Properties assigned to the import.meta
object that are objects may\nallow the module to access information outside the specified context
. Use\nvm.runInContext()
to create objects in a specific context.
import vm from 'node:vm';\n\nconst contextifiedObject = vm.createContext({ secret: 42 });\n\nconst module = new vm.SourceTextModule(\n 'Object.getPrototypeOf(import.meta.prop).secret = secret;',\n {\n initializeImportMeta(meta) {\n // Note: this object is created in the top context. As such,\n // Object.getPrototypeOf(import.meta.prop) points to the\n // Object.prototype in the top context rather than that in\n // the contextified object.\n meta.prop = {};\n },\n });\n// Since module has no dependencies, the linker function will never be called.\nawait module.link(() => {});\nawait module.evaluate();\n\n// Now, Object.prototype.secret will be equal to 42.\n//\n// To fix this problem, replace\n// meta.prop = {};\n// above with\n// meta.prop = vm.runInContext('{}', contextifiedObject);\n
\nconst vm = require('node:vm');\nconst contextifiedObject = vm.createContext({ secret: 42 });\n(async () => {\n const module = new vm.SourceTextModule(\n 'Object.getPrototypeOf(import.meta.prop).secret = secret;',\n {\n initializeImportMeta(meta) {\n // Note: this object is created in the top context. As such,\n // Object.getPrototypeOf(import.meta.prop) points to the\n // Object.prototype in the top context rather than that in\n // the contextified object.\n meta.prop = {};\n },\n });\n // Since module has no dependencies, the linker function will never be called.\n await module.link(() => {});\n await module.evaluate();\n // Now, Object.prototype.secret will be equal to 42.\n //\n // To fix this problem, replace\n // meta.prop = {};\n // above with\n // meta.prop = vm.runInContext('{}', contextifiedObject);\n})();\n
"
}
]
},
{
"textRaw": "Class: `vm.SyntheticModule`",
"type": "class",
"name": "vm.SyntheticModule",
"meta": {
"added": [
"v13.0.0",
"v12.16.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"desc": "This feature is only available with the --experimental-vm-modules
command\nflag enabled.
The vm.SyntheticModule
class provides the Synthetic Module Record as\ndefined in the WebIDL specification. The purpose of synthetic modules is to\nprovide a generic interface for exposing non-JavaScript sources to ECMAScript\nmodule graphs.
const vm = require('node:vm');\n\nconst source = '{ \"a\": 1 }';\nconst module = new vm.SyntheticModule(['default'], function() {\n const obj = JSON.parse(source);\n this.setExport('default', obj);\n});\n\n// Use `module` in linking...\n
",
"methods": [
{
"textRaw": "`syntheticModule.setExport(name, value)`",
"type": "method",
"name": "setExport",
"meta": {
"added": [
"v13.0.0",
"v12.16.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string} Name of the export to set.",
"name": "name",
"type": "string",
"desc": "Name of the export to set."
},
{
"textRaw": "`value` {any} The value to set the export to.",
"name": "value",
"type": "any",
"desc": "The value to set the export to."
}
]
}
],
"desc": "This method is used after the module is linked to set the values of exports. If\nit is called before the module is linked, an ERR_VM_MODULE_STATUS
error\nwill be thrown.
import vm from 'node:vm';\n\nconst m = new vm.SyntheticModule(['x'], () => {\n m.setExport('x', 1);\n});\n\nawait m.link(() => {});\nawait m.evaluate();\n\nassert.strictEqual(m.namespace.x, 1);\n
\nconst vm = require('node:vm');\n(async () => {\n const m = new vm.SyntheticModule(['x'], () => {\n m.setExport('x', 1);\n });\n await m.link(() => {});\n await m.evaluate();\n assert.strictEqual(m.namespace.x, 1);\n})();\n
"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`exportNames` {string\\[]} Array of names that will be exported from the module.",
"name": "exportNames",
"type": "string\\[]",
"desc": "Array of names that will be exported from the module."
},
{
"textRaw": "`evaluateCallback` {Function} Called when the module is evaluated.",
"name": "evaluateCallback",
"type": "Function",
"desc": "Called when the module is evaluated."
},
{
"textRaw": "`options`",
"name": "options",
"options": [
{
"textRaw": "`identifier` {string} String used in stack traces. **Default:** `'vm:module(i)'` where `i` is a context-specific ascending index.",
"name": "identifier",
"type": "string",
"default": "`'vm:module(i)'` where `i` is a context-specific ascending index",
"desc": "String used in stack traces."
},
{
"textRaw": "`context` {Object} The [contextified][] object as returned by the `vm.createContext()` method, to compile and evaluate this `Module` in.",
"name": "context",
"type": "Object",
"desc": "The [contextified][] object as returned by the `vm.createContext()` method, to compile and evaluate this `Module` in."
}
]
}
],
"desc": "Creates a new SyntheticModule
instance.
Objects assigned to the exports of this instance may allow importers of\nthe module to access information outside the specified context
. Use\nvm.runInContext()
to create objects in a specific context.
Compiles the given code into the provided context (if no context is\nsupplied, the current context is used), and returns it wrapped inside a\nfunction with the given params
.
If given a contextObject
, the vm.createContext()
method will prepare\nthat object so that it can be used in calls to\nvm.runInContext()
or script.runInContext()
. Inside such scripts,\nthe contextObject
will be the global object, retaining all of its existing\nproperties but also having the built-in objects and functions any standard\nglobal object has. Outside of scripts run by the vm module, global variables\nwill remain unchanged.
const vm = require('node:vm');\n\nglobal.globalVar = 3;\n\nconst context = { globalVar: 1 };\nvm.createContext(context);\n\nvm.runInContext('globalVar *= 2;', context);\n\nconsole.log(context);\n// Prints: { globalVar: 2 }\n\nconsole.log(global.globalVar);\n// Prints: 3\n
\nIf contextObject
is omitted (or passed explicitly as undefined
), a new,\nempty contextified object will be returned.
The vm.createContext()
method is primarily useful for creating a single\ncontext that can be used to run multiple scripts. For instance, if emulating a\nweb browser, the method can be used to create a single context representing a\nwindow's global object, then run all <script>
tags together within that\ncontext.
The provided name
and origin
of the context are made visible through the\nInspector API.
Returns true
if the given object
object has been contextified using\nvm.createContext()
.
Measure the memory known to V8 and used by all contexts known to the\ncurrent V8 isolate, or the main context.
\noptions
<Object> Optional.\nmode
<string> Either 'summary'
or 'detailed'
. In summary mode,\nonly the memory measured for the main context will be returned. In\ndetailed mode, the memory measured for all contexts known to the\ncurrent V8 isolate will be returned.\nDefault: 'summary'
execution
<string> Either 'default'
or 'eager'
. With default\nexecution, the promise will not resolve until after the next scheduled\ngarbage collection starts, which may take a while (or never if the program\nexits before the next GC). With eager execution, the GC will be started\nright away to measure the memory.\nDefault: 'default'
ERR_CONTEXT_NOT_INITIALIZED
error.The format of the object that the returned Promise may resolve with is\nspecific to the V8 engine and may change from one version of V8 to the next.
\nThe returned result is different from the statistics returned by\nv8.getHeapSpaceStatistics()
in that vm.measureMemory()
measure the\nmemory reachable by each V8 specific contexts in the current instance of\nthe V8 engine, while the result of v8.getHeapSpaceStatistics()
measure\nthe memory occupied by each heap space in the current V8 instance.
const vm = require('node:vm');\n// Measure the memory used by the main context.\nvm.measureMemory({ mode: 'summary' })\n // This is the same as vm.measureMemory()\n .then((result) => {\n // The current format is:\n // {\n // total: {\n // jsMemoryEstimate: 2418479, jsMemoryRange: [ 2418479, 2745799 ]\n // }\n // }\n console.log(result);\n });\n\nconst context = vm.createContext({ a: 1 });\nvm.measureMemory({ mode: 'detailed', execution: 'eager' })\n .then((result) => {\n // Reference the context here so that it won't be GC'ed\n // until the measurement is complete.\n console.log(context.a);\n // {\n // total: {\n // jsMemoryEstimate: 2574732,\n // jsMemoryRange: [ 2574732, 2904372 ]\n // },\n // current: {\n // jsMemoryEstimate: 2438996,\n // jsMemoryRange: [ 2438996, 2768636 ]\n // },\n // other: [\n // {\n // jsMemoryEstimate: 135736,\n // jsMemoryRange: [ 135736, 465376 ]\n // }\n // ]\n // }\n console.log(result);\n });\n
"
},
{
"textRaw": "`vm.runInContext(code, contextifiedObject[, options])`",
"type": "method",
"name": "runInContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": [
{
"version": [
"v21.7.0"
],
"pr-url": "https://github.com/nodejs/node/pull/51244",
"description": "Added support for `vm.constants.USE_MAIN_CONTEXT_DEFAULT_LOADER`."
},
{
"version": [
"v17.0.0",
"v16.12.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40249",
"description": "Added support for import attributes to the `importModuleDynamically` parameter."
},
{
"version": "v6.3.0",
"pr-url": "https://github.com/nodejs/node/pull/6635",
"description": "The `breakOnSigint` option is supported now."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`code` {string} The JavaScript code to compile and run.",
"name": "code",
"type": "string",
"desc": "The JavaScript code to compile and run."
},
{
"textRaw": "`contextifiedObject` {Object} The [contextified][] object that will be used as the `global` when the `code` is compiled and run.",
"name": "contextifiedObject",
"type": "Object",
"desc": "The [contextified][] object that will be used as the `global` when the `code` is compiled and run."
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script. **Default:** `'evalmachine.The vm.runInContext()
method compiles code
, runs it within the context of\nthe contextifiedObject
, then returns the result. Running code does not have\naccess to the local scope. The contextifiedObject
object must have been\npreviously contextified using the vm.createContext()
method.
If options
is a string, then it specifies the filename.
The following example compiles and executes different scripts using a single\ncontextified object:
\nconst vm = require('node:vm');\n\nconst contextObject = { globalVar: 1 };\nvm.createContext(contextObject);\n\nfor (let i = 0; i < 10; ++i) {\n vm.runInContext('globalVar *= 2;', contextObject);\n}\nconsole.log(contextObject);\n// Prints: { globalVar: 1024 }\n
"
},
{
"textRaw": "`vm.runInNewContext(code[, contextObject[, options]])`",
"type": "method",
"name": "runInNewContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": [
{
"version": [
"v21.7.0"
],
"pr-url": "https://github.com/nodejs/node/pull/51244",
"description": "Added support for `vm.constants.USE_MAIN_CONTEXT_DEFAULT_LOADER`."
},
{
"version": [
"v17.0.0",
"v16.12.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40249",
"description": "Added support for import attributes to the `importModuleDynamically` parameter."
},
{
"version": "v14.6.0",
"pr-url": "https://github.com/nodejs/node/pull/34023",
"description": "The `microtaskMode` option is supported now."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/19016",
"description": "The `contextCodeGeneration` option is supported now."
},
{
"version": "v6.3.0",
"pr-url": "https://github.com/nodejs/node/pull/6635",
"description": "The `breakOnSigint` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {any} the result of the very last statement executed in the script.",
"name": "return",
"type": "any",
"desc": "the result of the very last statement executed in the script."
},
"params": [
{
"textRaw": "`code` {string} The JavaScript code to compile and run.",
"name": "code",
"type": "string",
"desc": "The JavaScript code to compile and run."
},
{
"textRaw": "`contextObject` {Object} An object that will be [contextified][]. If `undefined`, a new object will be created.",
"name": "contextObject",
"type": "Object",
"desc": "An object that will be [contextified][]. If `undefined`, a new object will be created."
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script. **Default:** `'evalmachine.The vm.runInNewContext()
first contextifies the given contextObject
(or\ncreates a new contextObject
if passed as undefined
), compiles the code
,\nruns it within the created context, then returns the result. Running code\ndoes not have access to the local scope.
If options
is a string, then it specifies the filename.
The following example compiles and executes code that increments a global\nvariable and sets a new one. These globals are contained in the contextObject
.
const vm = require('node:vm');\n\nconst contextObject = {\n animal: 'cat',\n count: 2,\n};\n\nvm.runInNewContext('count += 1; name = \"kitty\"', contextObject);\nconsole.log(contextObject);\n// Prints: { animal: 'cat', count: 3, name: 'kitty' }\n
"
},
{
"textRaw": "`vm.runInThisContext(code[, options])`",
"type": "method",
"name": "runInThisContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": [
{
"version": [
"v21.7.0"
],
"pr-url": "https://github.com/nodejs/node/pull/51244",
"description": "Added support for `vm.constants.USE_MAIN_CONTEXT_DEFAULT_LOADER`."
},
{
"version": [
"v17.0.0",
"v16.12.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40249",
"description": "Added support for import attributes to the `importModuleDynamically` parameter."
},
{
"version": "v6.3.0",
"pr-url": "https://github.com/nodejs/node/pull/6635",
"description": "The `breakOnSigint` option is supported now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {any} the result of the very last statement executed in the script.",
"name": "return",
"type": "any",
"desc": "the result of the very last statement executed in the script."
},
"params": [
{
"textRaw": "`code` {string} The JavaScript code to compile and run.",
"name": "code",
"type": "string",
"desc": "The JavaScript code to compile and run."
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script. **Default:** `'evalmachine.vm.runInThisContext()
compiles code
, runs it within the context of the\ncurrent global
and returns the result. Running code does not have access to\nlocal scope, but does have access to the current global
object.
If options
is a string, then it specifies the filename.
The following example illustrates using both vm.runInThisContext()
and\nthe JavaScript eval()
function to run the same code:
const vm = require('node:vm');\nlet localVar = 'initial value';\n\nconst vmResult = vm.runInThisContext('localVar = \"vm\";');\nconsole.log(`vmResult: '${vmResult}', localVar: '${localVar}'`);\n// Prints: vmResult: 'vm', localVar: 'initial value'\n\nconst evalResult = eval('localVar = \"eval\";');\nconsole.log(`evalResult: '${evalResult}', localVar: '${localVar}'`);\n// Prints: evalResult: 'eval', localVar: 'eval'\n
\nBecause vm.runInThisContext()
does not have access to the local scope,\nlocalVar
is unchanged. In contrast, eval()
does have access to the\nlocal scope, so the value localVar
is changed. In this way\nvm.runInThisContext()
is much like an indirect eval()
call, e.g.\n(0,eval)('code')
.
When using either script.runInThisContext()
or\nvm.runInThisContext()
, the code is executed within the current V8 global\ncontext. The code passed to this VM context will have its own isolated scope.
In order to run a simple web server using the node:http
module the code passed\nto the context must either call require('node:http')
on its own, or have a\nreference to the node:http
module passed to it. For instance:
'use strict';\nconst vm = require('node:vm');\n\nconst code = `\n((require) => {\n const http = require('node:http');\n\n http.createServer((request, response) => {\n response.writeHead(200, { 'Content-Type': 'text/plain' });\n response.end('Hello World\\\\n');\n }).listen(8124);\n\n console.log('Server running at http://127.0.0.1:8124/');\n})`;\n\nvm.runInThisContext(code)(require);\n
\nThe require()
in the above case shares the state with the context it is\npassed from. This may introduce risks when untrusted code is executed, e.g.\naltering objects in the context in unwanted ways.
Returns an object containing commonly used constants for VM operations.
", "properties": [ { "textRaw": "`vm.constants.USE_MAIN_CONTEXT_DEFAULT_LOADER`", "name": "USE_MAIN_CONTEXT_DEFAULT_LOADER", "meta": { "added": [ "v21.7.0" ], "changes": [] }, "stability": 1, "stabilityText": ".1 - Active development", "desc": "A constant that can be used as the importModuleDynamically
option to\nvm.Script
and vm.compileFunction()
so that Node.js uses the default\nESM loader from the main context to load the requested module.
For detailed information, see\nSupport of dynamic import()
in compilation APIs.
All JavaScript executed within Node.js runs within the scope of a \"context\".\nAccording to the V8 Embedder's Guide:
\n\n\nIn V8, a context is an execution environment that allows separate, unrelated,\nJavaScript applications to run in a single instance of V8. You must explicitly\nspecify the context in which you want any JavaScript code to be run.
\n
When the method vm.createContext()
is called, the contextObject
argument\n(or a newly-created object if contextObject
is undefined
) is associated\ninternally with a new instance of a V8 Context. This V8 Context provides the\ncode
run using the node:vm
module's methods with an isolated global\nenvironment within which it can operate. The process of creating the V8 Context\nand associating it with the contextObject
is what this document refers to as\n\"contextifying\" the object.
Promise
s and async function
s can schedule tasks run by the JavaScript\nengine asynchronously. By default, these tasks are run after all JavaScript\nfunctions on the current stack are done executing.\nThis allows escaping the functionality of the timeout
and\nbreakOnSigint
options.
For example, the following code executed by vm.runInNewContext()
with a\ntimeout of 5 milliseconds schedules an infinite loop to run after a promise\nresolves. The scheduled loop is never interrupted by the timeout:
const vm = require('node:vm');\n\nfunction loop() {\n console.log('entering loop');\n while (1) console.log(Date.now());\n}\n\nvm.runInNewContext(\n 'Promise.resolve().then(() => loop());',\n { loop, console },\n { timeout: 5 },\n);\n// This is printed *before* 'entering loop' (!)\nconsole.log('done executing');\n
\nThis can be addressed by passing microtaskMode: 'afterEvaluate'
to the code\nthat creates the Context
:
const vm = require('node:vm');\n\nfunction loop() {\n while (1) console.log(Date.now());\n}\n\nvm.runInNewContext(\n 'Promise.resolve().then(() => loop());',\n { loop, console },\n { timeout: 5, microtaskMode: 'afterEvaluate' },\n);\n
\nIn this case, the microtask scheduled through promise.then()
will be run\nbefore returning from vm.runInNewContext()
, and will be interrupted\nby the timeout
functionality. This applies only to code running in a\nvm.Context
, so e.g. vm.runInThisContext()
does not take this option.
Promise callbacks are entered into the microtask queue of the context in which\nthey were created. For example, if () => loop()
is replaced with just loop
\nin the above example, then loop
will be pushed into the global microtask\nqueue, because it is a function from the outer (main) context, and thus will\nalso be able to escape the timeout.
If asynchronous scheduling functions such as process.nextTick()
,\nqueueMicrotask()
, setTimeout()
, setImmediate()
, etc. are made available\ninside a vm.Context
, functions passed to them will be added to global queues,\nwhich are shared by all contexts. Therefore, callbacks passed to those functions\nare not controllable through the timeout either.
The following APIs support an importModuleDynamically
option to enable dynamic\nimport()
in code compiled by the vm module.
new vm.Script
vm.compileFunction()
new vm.SourceTextModule
vm.runInThisContext()
vm.runInContext()
vm.runInNewContext()
vm.createContext()
This option is still part of the experimental modules API. We do not recommend\nusing it in a production environment.
", "modules": [ { "textRaw": "When the `importModuleDynamically` option is not specified or undefined", "name": "when_the_`importmoduledynamically`_option_is_not_specified_or_undefined", "desc": "If this option is not specified, or if it's undefined
, code containing\nimport()
can still be compiled by the vm APIs, but when the compiled code is\nexecuted and it actually calls import()
, the result will reject with\nERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING
.
This option is currently not supported for vm.SourceTextModule
.
With this option, when an import()
is initiated in the compiled code, Node.js\nwould use the default ESM loader from the main context to load the requested\nmodule and return it to the code being executed.
This gives access to Node.js built-in modules such as fs
or http
\nto the code being compiled. If the code is executed in a different context,\nbe aware that the objects created by modules loaded from the main context\nare still from the main context and not instanceof
built-in classes in the\nnew context.
const { Script, constants } = require('node:vm');\nconst script = new Script(\n 'import(\"node:fs\").then(({readFile}) => readFile instanceof Function)',\n { importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER });\n\n// false: URL loaded from the main context is not an instance of the Function\n// class in the new context.\nscript.runInNewContext().then(console.log);\n
\nimport { Script, constants } from 'node:vm';\n\nconst script = new Script(\n 'import(\"node:fs\").then(({readFile}) => readFile instanceof Function)',\n { importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER });\n\n// false: URL loaded from the main context is not an instance of the Function\n// class in the new context.\nscript.runInNewContext().then(console.log);\n
\nThis option also allows the script or function to load user modules:
\nimport { Script, constants } from 'node:vm';\nimport { resolve } from 'node:path';\nimport { writeFileSync } from 'node:fs';\n\n// Write test.js and test.txt to the directory where the current script\n// being run is located.\nwriteFileSync(resolve(import.meta.dirname, 'test.mjs'),\n 'export const filename = \"./test.json\";');\nwriteFileSync(resolve(import.meta.dirname, 'test.json'),\n '{\"hello\": \"world\"}');\n\n// Compile a script that loads test.mjs and then test.json\n// as if the script is placed in the same directory.\nconst script = new Script(\n `(async function() {\n const { filename } = await import('./test.mjs');\n return import(filename, { with: { type: 'json' } })\n })();`,\n {\n filename: resolve(import.meta.dirname, 'test-with-default.js'),\n importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER,\n });\n\n// { default: { hello: 'world' } }\nscript.runInThisContext().then(console.log);\n
\nconst { Script, constants } = require('node:vm');\nconst { resolve } = require('node:path');\nconst { writeFileSync } = require('node:fs');\n\n// Write test.js and test.txt to the directory where the current script\n// being run is located.\nwriteFileSync(resolve(__dirname, 'test.mjs'),\n 'export const filename = \"./test.json\";');\nwriteFileSync(resolve(__dirname, 'test.json'),\n '{\"hello\": \"world\"}');\n\n// Compile a script that loads test.mjs and then test.json\n// as if the script is placed in the same directory.\nconst script = new Script(\n `(async function() {\n const { filename } = await import('./test.mjs');\n return import(filename, { with: { type: 'json' } })\n })();`,\n {\n filename: resolve(__dirname, 'test-with-default.js'),\n importModuleDynamically: constants.USE_MAIN_CONTEXT_DEFAULT_LOADER,\n });\n\n// { default: { hello: 'world' } }\nscript.runInThisContext().then(console.log);\n
\nThere are a few caveats with loading user modules using the default loader\nfrom the main context:
\nfilename
option passed\nto vm.Script
or vm.compileFunction()
. The resolution can work with a\nfilename
that's either an absolute path or a URL string. If filename
is\na string that's neither an absolute path or a URL, or if it's undefined,\nthe resolution will be relative to the current working directory\nof the process. In the case of vm.createContext()
, the resolution is always\nrelative to the current working directory since this option is only used when\nthere isn't a referrer script or module.filename
that resolves to a specific path, once the process\nmanages to load a particular module from that path, the result may be cached,\nand subsequent load of the same module from the same path would return the\nsame thing. If the filename
is a URL string, the cache would not be hit\nif it has different search parameters. For filename
s that are not URL\nstrings, there is currently no way to bypass the caching behavior.When importModuleDynamically
is a function, it will be invoked when import()
\nis called in the compiled code for users to customize how the requested module\nshould be compiled and evaluated. Currently, the Node.js instance must be\nlaunched with the --experimental-vm-modules
flag for this option to work. If\nthe flag isn't set, this callback will be ignored. If the code evaluated\nactually calls to import()
, the result will reject with\nERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING_FLAG
.
The callback importModuleDynamically(specifier, referrer, importAttributes)
\nhas the following signature:
specifier
<string> specifier passed to import()
referrer
<vm.Script> | <Function> | <vm.SourceTextModule> | <Object>\nThe referrer is the compiled vm.Script
for new vm.Script
,\nvm.runInThisContext
, vm.runInContext
and vm.runInNewContext
. It's the\ncompiled Function
for vm.compileFunction
, the compiled\nvm.SourceTextModule
for new vm.SourceTextModule
, and the context Object
\nfor vm.createContext()
.importAttributes
<Object> The \"with\"
value passed to the\noptionsExpression
optional parameter, or an empty object if no value was\nprovided.vm.Module
is\nrecommended in order to take advantage of error tracking, and to avoid issues\nwith namespaces that contain then
function exports.// This script must be run with --experimental-vm-modules.\nimport { Script, SyntheticModule } from 'node:vm';\n\nconst script = new Script('import(\"foo.json\", { with: { type: \"json\" } })', {\n async importModuleDynamically(specifier, referrer, importAttributes) {\n console.log(specifier); // 'foo.json'\n console.log(referrer); // The compiled script\n console.log(importAttributes); // { type: 'json' }\n const m = new SyntheticModule(['bar'], () => { });\n await m.link(() => { });\n m.setExport('bar', { hello: 'world' });\n return m;\n },\n});\nconst result = await script.runInThisContext();\nconsole.log(result); // { bar: { hello: 'world' } }\n
\n// This script must be run with --experimental-vm-modules.\nconst { Script, SyntheticModule } = require('node:vm');\n\n(async function main() {\n const script = new Script('import(\"foo.json\", { with: { type: \"json\" } })', {\n async importModuleDynamically(specifier, referrer, importAttributes) {\n console.log(specifier); // 'foo.json'\n console.log(referrer); // The compiled script\n console.log(importAttributes); // { type: 'json' }\n const m = new SyntheticModule(['bar'], () => { });\n await m.link(() => { });\n m.setExport('bar', { hello: 'world' });\n return m;\n },\n });\n const result = await script.runInThisContext();\n console.log(result); // { bar: { hello: 'world' } }\n})();\n
",
"type": "module",
"displayName": "When `importModuleDynamically` is a function"
}
],
"type": "module",
"displayName": "Support of dynamic `import()` in compilation APIs"
}
],
"type": "module",
"displayName": "vm",
"source": "doc/api/vm.md"
},
{
"textRaw": "WebAssembly System Interface (WASI)",
"name": "webassembly_system_interface_(wasi)",
"introduced_in": "v12.16.0",
"stability": 1,
"stabilityText": "Experimental",
"desc": "The node:wasi
module does not currently provide the\ncomprehensive file system security properties provided by some WASI runtimes.\nFull support for secure file system sandboxing may or may not be implemented in\nfuture. In the mean time, do not rely on it to run untrusted code.
Source Code: lib/wasi.js
\nThe WASI API provides an implementation of the WebAssembly System Interface\nspecification. WASI gives WebAssembly applications access to the underlying\noperating system via a collection of POSIX-like functions.
\nimport { readFile } from 'node:fs/promises';\nimport { WASI } from 'wasi';\nimport { argv, env } from 'node:process';\n\nconst wasi = new WASI({\n version: 'preview1',\n args: argv,\n env,\n preopens: {\n '/local': '/some/real/path/that/wasm/can/access',\n },\n});\n\nconst wasm = await WebAssembly.compile(\n await readFile(new URL('./demo.wasm', import.meta.url)),\n);\nconst instance = await WebAssembly.instantiate(wasm, wasi.getImportObject());\n\nwasi.start(instance);\n
\n'use strict';\nconst { readFile } = require('node:fs/promises');\nconst { WASI } = require('wasi');\nconst { argv, env } = require('node:process');\nconst { join } = require('node:path');\n\nconst wasi = new WASI({\n version: 'preview1',\n args: argv,\n env,\n preopens: {\n '/local': '/some/real/path/that/wasm/can/access',\n },\n});\n\n(async () => {\n const wasm = await WebAssembly.compile(\n await readFile(join(__dirname, 'demo.wasm')),\n );\n const instance = await WebAssembly.instantiate(wasm, wasi.getImportObject());\n\n wasi.start(instance);\n})();\n
\nTo run the above example, create a new WebAssembly text format file named\ndemo.wat
:
(module\n ;; Import the required fd_write WASI function which will write the given io vectors to stdout\n ;; The function signature for fd_write is:\n ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written\n (import \"wasi_snapshot_preview1\" \"fd_write\" (func $fd_write (param i32 i32 i32 i32) (result i32)))\n\n (memory 1)\n (export \"memory\" (memory 0))\n\n ;; Write 'hello world\\n' to memory at an offset of 8 bytes\n ;; Note the trailing newline which is required for the text to appear\n (data (i32.const 8) \"hello world\\n\")\n\n (func $main (export \"_start\")\n ;; Creating a new io vector within linear memory\n (i32.store (i32.const 0) (i32.const 8)) ;; iov.iov_base - This is a pointer to the start of the 'hello world\\n' string\n (i32.store (i32.const 4) (i32.const 12)) ;; iov.iov_len - The length of the 'hello world\\n' string\n\n (call $fd_write\n (i32.const 1) ;; file_descriptor - 1 for stdout\n (i32.const 0) ;; *iovs - The pointer to the iov array, which is stored at memory location 0\n (i32.const 1) ;; iovs_len - We're printing 1 string stored in an iov - so one.\n (i32.const 20) ;; nwritten - A place in memory to store the number of bytes written\n )\n drop ;; Discard the number of bytes written from the top of the stack\n )\n)\n
\nUse wabt to compile .wat
to .wasm
wat2wasm demo.wat\n
",
"modules": [
{
"textRaw": "Security",
"name": "security",
"meta": {
"added": [
"v21.2.0"
],
"changes": [
{
"version": "v21.2.0",
"pr-url": "https://github.com/nodejs/node/pull/50396",
"description": "Clarify WASI security properties."
}
]
},
"desc": "WASI provides a capabilities-based model through which applications are provided\ntheir own custom env
, preopens
, stdin
, stdout
, stderr
, and exit
\ncapabilities.
The current Node.js threat model does not provide secure sandboxing as is\npresent in some WASI runtimes.
\nWhile the capability features are supported, they do not form a security model\nin Node.js. For example, the file system sandboxing can be escaped with various\ntechniques. The project is exploring whether these security guarantees could be\nadded in future.
", "type": "module", "displayName": "Security" } ], "classes": [ { "textRaw": "Class: `WASI`", "type": "class", "name": "WASI", "meta": { "added": [ "v13.3.0", "v12.16.0" ], "changes": [] }, "desc": "The WASI
class provides the WASI system call API and additional convenience\nmethods for working with WASI-based applications. Each WASI
instance\nrepresents a distinct environment.
Return an import object that can be passed to WebAssembly.instantiate()
if\nno other WASM imports are needed beyond those provided by WASI.
If version unstable
was passed into the constructor it will return:
{ wasi_unstable: wasi.wasiImport }\n
\nIf version preview1
was passed into the constructor or no version was\nspecified it will return:
{ wasi_snapshot_preview1: wasi.wasiImport }\n
"
},
{
"textRaw": "`wasi.start(instance)`",
"type": "method",
"name": "start",
"meta": {
"added": [
"v13.3.0",
"v12.16.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`instance` {WebAssembly.Instance}",
"name": "instance",
"type": "WebAssembly.Instance"
}
]
}
],
"desc": "Attempt to begin execution of instance
as a WASI command by invoking its\n_start()
export. If instance
does not contain a _start()
export, or if\ninstance
contains an _initialize()
export, then an exception is thrown.
start()
requires that instance
exports a WebAssembly.Memory
named\nmemory
. If instance
does not have a memory
export an exception is thrown.
If start()
is called more than once, an exception is thrown.
Attempt to initialize instance
as a WASI reactor by invoking its\n_initialize()
export, if it is present. If instance
contains a _start()
\nexport, then an exception is thrown.
initialize()
requires that instance
exports a WebAssembly.Memory
named\nmemory
. If instance
does not have a memory
export an exception is thrown.
If initialize()
is called more than once, an exception is thrown.
wasiImport
is an object that implements the WASI system call API. This object\nshould be passed as the wasi_snapshot_preview1
import during the instantiation\nof a WebAssembly.Instance
.
Node.js provides an implementation of the standard Web Crypto API.
\nUse globalThis.crypto
or require('node:crypto').webcrypto
to access this\nmodule.
const { subtle } = globalThis.crypto;\n\n(async function() {\n\n const key = await subtle.generateKey({\n name: 'HMAC',\n hash: 'SHA-256',\n length: 256,\n }, true, ['sign', 'verify']);\n\n const enc = new TextEncoder();\n const message = enc.encode('I love cupcakes');\n\n const digest = await subtle.sign({\n name: 'HMAC',\n }, key, message);\n\n})();\n
\nThe <SubtleCrypto> class can be used to generate symmetric (secret) keys\nor asymmetric key pairs (public key and private key).
", "modules": [ { "textRaw": "AES keys", "name": "aes_keys", "desc": "const { subtle } = globalThis.crypto;\n\nasync function generateAesKey(length = 256) {\n const key = await subtle.generateKey({\n name: 'AES-CBC',\n length,\n }, true, ['encrypt', 'decrypt']);\n\n return key;\n}\n
",
"type": "module",
"displayName": "AES keys"
},
{
"textRaw": "ECDSA key pairs",
"name": "ecdsa_key_pairs",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function generateEcKey(namedCurve = 'P-521') {\n const {\n publicKey,\n privateKey,\n } = await subtle.generateKey({\n name: 'ECDSA',\n namedCurve,\n }, true, ['sign', 'verify']);\n\n return { publicKey, privateKey };\n}\n
",
"type": "module",
"displayName": "ECDSA key pairs"
},
{
"textRaw": "Ed25519/Ed448/X25519/X448 key pairs",
"name": "ed25519/ed448/x25519/x448_key_pairs",
"stability": 1,
"stabilityText": "Experimental",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function generateEd25519Key() {\n return subtle.generateKey({\n name: 'Ed25519',\n }, true, ['sign', 'verify']);\n}\n\nasync function generateX25519Key() {\n return subtle.generateKey({\n name: 'X25519',\n }, true, ['deriveKey']);\n}\n
",
"type": "module",
"displayName": "Ed25519/Ed448/X25519/X448 key pairs"
},
{
"textRaw": "HMAC keys",
"name": "hmac_keys",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function generateHmacKey(hash = 'SHA-256') {\n const key = await subtle.generateKey({\n name: 'HMAC',\n hash,\n }, true, ['sign', 'verify']);\n\n return key;\n}\n
",
"type": "module",
"displayName": "HMAC keys"
},
{
"textRaw": "RSA key pairs",
"name": "rsa_key_pairs",
"desc": "const { subtle } = globalThis.crypto;\nconst publicExponent = new Uint8Array([1, 0, 1]);\n\nasync function generateRsaKey(modulusLength = 2048, hash = 'SHA-256') {\n const {\n publicKey,\n privateKey,\n } = await subtle.generateKey({\n name: 'RSASSA-PKCS1-v1_5',\n modulusLength,\n publicExponent,\n hash,\n }, true, ['sign', 'verify']);\n\n return { publicKey, privateKey };\n}\n
",
"type": "module",
"displayName": "RSA key pairs"
}
],
"type": "module",
"displayName": "Generating keys"
},
{
"textRaw": "Encryption and decryption",
"name": "encryption_and_decryption",
"desc": "const crypto = globalThis.crypto;\n\nasync function aesEncrypt(plaintext) {\n const ec = new TextEncoder();\n const key = await generateAesKey();\n const iv = crypto.getRandomValues(new Uint8Array(16));\n\n const ciphertext = await crypto.subtle.encrypt({\n name: 'AES-CBC',\n iv,\n }, key, ec.encode(plaintext));\n\n return {\n key,\n iv,\n ciphertext,\n };\n}\n\nasync function aesDecrypt(ciphertext, key, iv) {\n const dec = new TextDecoder();\n const plaintext = await crypto.subtle.decrypt({\n name: 'AES-CBC',\n iv,\n }, key, ciphertext);\n\n return dec.decode(plaintext);\n}\n
",
"type": "module",
"displayName": "Encryption and decryption"
},
{
"textRaw": "Exporting and importing keys",
"name": "exporting_and_importing_keys",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function generateAndExportHmacKey(format = 'jwk', hash = 'SHA-512') {\n const key = await subtle.generateKey({\n name: 'HMAC',\n hash,\n }, true, ['sign', 'verify']);\n\n return subtle.exportKey(format, key);\n}\n\nasync function importHmacKey(keyData, format = 'jwk', hash = 'SHA-512') {\n const key = await subtle.importKey(format, keyData, {\n name: 'HMAC',\n hash,\n }, true, ['sign', 'verify']);\n\n return key;\n}\n
",
"type": "module",
"displayName": "Exporting and importing keys"
},
{
"textRaw": "Wrapping and unwrapping keys",
"name": "wrapping_and_unwrapping_keys",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function generateAndWrapHmacKey(format = 'jwk', hash = 'SHA-512') {\n const [\n key,\n wrappingKey,\n ] = await Promise.all([\n subtle.generateKey({\n name: 'HMAC', hash,\n }, true, ['sign', 'verify']),\n subtle.generateKey({\n name: 'AES-KW',\n length: 256,\n }, true, ['wrapKey', 'unwrapKey']),\n ]);\n\n const wrappedKey = await subtle.wrapKey(format, key, wrappingKey, 'AES-KW');\n\n return { wrappedKey, wrappingKey };\n}\n\nasync function unwrapHmacKey(\n wrappedKey,\n wrappingKey,\n format = 'jwk',\n hash = 'SHA-512') {\n\n const key = await subtle.unwrapKey(\n format,\n wrappedKey,\n wrappingKey,\n 'AES-KW',\n { name: 'HMAC', hash },\n true,\n ['sign', 'verify']);\n\n return key;\n}\n
",
"type": "module",
"displayName": "Wrapping and unwrapping keys"
},
{
"textRaw": "Sign and verify",
"name": "sign_and_verify",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function sign(key, data) {\n const ec = new TextEncoder();\n const signature =\n await subtle.sign('RSASSA-PKCS1-v1_5', key, ec.encode(data));\n return signature;\n}\n\nasync function verify(key, signature, data) {\n const ec = new TextEncoder();\n const verified =\n await subtle.verify(\n 'RSASSA-PKCS1-v1_5',\n key,\n signature,\n ec.encode(data));\n return verified;\n}\n
",
"type": "module",
"displayName": "Sign and verify"
},
{
"textRaw": "Deriving bits and keys",
"name": "deriving_bits_and_keys",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function pbkdf2(pass, salt, iterations = 1000, length = 256) {\n const ec = new TextEncoder();\n const key = await subtle.importKey(\n 'raw',\n ec.encode(pass),\n 'PBKDF2',\n false,\n ['deriveBits']);\n const bits = await subtle.deriveBits({\n name: 'PBKDF2',\n hash: 'SHA-512',\n salt: ec.encode(salt),\n iterations,\n }, key, length);\n return bits;\n}\n\nasync function pbkdf2Key(pass, salt, iterations = 1000, length = 256) {\n const ec = new TextEncoder();\n const keyMaterial = await subtle.importKey(\n 'raw',\n ec.encode(pass),\n 'PBKDF2',\n false,\n ['deriveKey']);\n const key = await subtle.deriveKey({\n name: 'PBKDF2',\n hash: 'SHA-512',\n salt: ec.encode(salt),\n iterations,\n }, keyMaterial, {\n name: 'AES-GCM',\n length,\n }, true, ['encrypt', 'decrypt']);\n return key;\n}\n
",
"type": "module",
"displayName": "Deriving bits and keys"
},
{
"textRaw": "Digest",
"name": "digest",
"desc": "const { subtle } = globalThis.crypto;\n\nasync function digest(data, algorithm = 'SHA-512') {\n const ec = new TextEncoder();\n const digest = await subtle.digest(algorithm, ec.encode(data));\n return digest;\n}\n
",
"type": "module",
"displayName": "Digest"
},
{
"textRaw": "Algorithm matrix",
"name": "algorithm_matrix",
"desc": "The table details the algorithms supported by the Node.js Web Crypto API\nimplementation and the APIs supported for each:
\nAlgorithm | \ngenerateKey | \nexportKey | \nimportKey | \nencrypt | \ndecrypt | \nwrapKey | \nunwrapKey | \nderiveBits | \nderiveKey | \nsign | \nverify | \ndigest | \n
---|---|---|---|---|---|---|---|---|---|---|---|---|
'RSASSA-PKCS1-v1_5' | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n\n |
'RSA-PSS' | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n\n |
'RSA-OAEP' | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n |
'ECDSA' | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n\n |
'Ed25519' 1 | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n\n |
'Ed448' 1 | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n\n |
'ECDH' | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n | \n |
'X25519' 1 | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n | \n |
'X448' 1 | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n | \n |
'AES-CTR' | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n |
'AES-CBC' | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n |
'AES-GCM' | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n |
'AES-KW' | \n✔ | \n✔ | \n✔ | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n | \n |
'HMAC' | \n✔ | \n✔ | \n✔ | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n\n |
'HKDF' | \n\n | ✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n | \n |
'PBKDF2' | \n\n | ✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n | \n |
'SHA-1' | \n\n | \n | \n | \n | \n | \n | \n | \n | \n | \n | \n | ✔ | \n
'SHA-256' | \n\n | \n | \n | \n | \n | \n | \n | \n | \n | \n | \n | ✔ | \n
'SHA-384' | \n\n | \n | \n | \n | \n | \n | \n | \n | \n | \n | \n | ✔ | \n
'SHA-512' | \n\n | \n | \n | \n | \n | \n | \n | \n | \n | \n | \n | ✔ | \n
The algorithm parameter objects define the methods and parameters used by\nthe various <SubtleCrypto> methods. While described here as \"classes\", they\nare simple JavaScript dictionary objects.
", "classes": [ { "textRaw": "Class: `AlgorithmIdentifier`", "type": "class", "name": "AlgorithmIdentifier", "meta": { "added": [ "v18.4.0", "v16.17.0" ], "changes": [] }, "properties": [ { "textRaw": "`name` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v18.4.0", "v16.17.0" ], "changes": [] } } ] }, { "textRaw": "Class: `AesCbcParams`", "type": "class", "name": "AesCbcParams", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`iv` Type: {ArrayBuffer|TypedArray|DataView|Buffer}", "type": "ArrayBuffer|TypedArray|DataView|Buffer", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Provides the initialization vector. It must be exactly 16-bytes in length\nand should be unpredictable and cryptographically random.
" }, { "textRaw": "`name` Type: {string} Must be `'AES-CBC'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Must be `'AES-CBC'`." } ] }, { "textRaw": "Class: `AesCtrParams`", "type": "class", "name": "AesCtrParams", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`counter` Type: {ArrayBuffer|TypedArray|DataView|Buffer}", "type": "ArrayBuffer|TypedArray|DataView|Buffer", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "The initial value of the counter block. This must be exactly 16 bytes long.
\nThe AES-CTR
method uses the rightmost length
bits of the block as the\ncounter and the remaining bits as the nonce.
With the AES-GCM method, the additionalData
is extra input that is not\nencrypted but is included in the authentication of the data. The use of\nadditionalData
is optional.
The initialization vector must be unique for every encryption operation using a\ngiven key.
\nIdeally, this is a deterministic 12-byte value that is computed in such a way\nthat it is guaranteed to be unique across all invocations that use the same key.\nAlternatively, the initialization vector may consist of at least 12\ncryptographically random bytes. For more information on constructing\ninitialization vectors for AES-GCM, refer to Section 8 of NIST SP 800-38D.
" }, { "textRaw": "`name` Type: {string} Must be `'AES-GCM'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Must be `'AES-GCM'`." }, { "textRaw": "`tagLength` Type: {number} The size in bits of the generated authentication tag. This values must be one of `32`, `64`, `96`, `104`, `112`, `120`, or `128`. **Default:** `128`.", "type": "number", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "default": "`128`", "desc": "The size in bits of the generated authentication tag. This values must be one of `32`, `64`, `96`, `104`, `112`, `120`, or `128`." } ] }, { "textRaw": "Class: `AesKeyGenParams`", "type": "class", "name": "AesKeyGenParams", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`length` Type: {number}", "type": "number", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "The length of the AES key to be generated. This must be either 128
, 192
,\nor 256
.
ECDH key derivation operates by taking as input one parties private key and\nanother parties public key -- using both to generate a common shared secret.\nThe ecdhKeyDeriveParams.public
property is set to the other parties public\nkey.
If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
The context
member represents the optional context data to associate with\nthe message.\nThe Node.js Web Crypto API implementation only supports zero-length context\nwhich is equivalent to not providing context at all.
If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
Provides application-specific contextual input to the HKDF algorithm.\nThis can be zero-length but must be provided.
" }, { "textRaw": "`name` Type: {string} Must be `'HKDF'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Must be `'HKDF'`." }, { "textRaw": "`salt` Type: {ArrayBuffer|TypedArray|DataView|Buffer}", "type": "ArrayBuffer|TypedArray|DataView|Buffer", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "The salt value significantly improves the strength of the HKDF algorithm.\nIt should be random or pseudorandom and should be the same length as the\noutput of the digest function (for instance, if using 'SHA-256'
as the\ndigest, the salt should be 256-bits of random data).
If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
The optional number of bits in the HMAC key. This is optional and should\nbe omitted for most cases.
" }, { "textRaw": "`name` Type: {string} Must be `'HMAC'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Must be `'HMAC'`." } ] }, { "textRaw": "Class: `HmacKeyGenParams`", "type": "class", "name": "HmacKeyGenParams", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`hash` Type: {string|Object}", "type": "string|Object", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
The number of bits to generate for the HMAC key. If omitted,\nthe length will be determined by the hash algorithm used.\nThis is optional and should be omitted for most cases.
" }, { "textRaw": "`name` Type: {string} Must be `'HMAC'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Must be `'HMAC'`." } ] }, { "textRaw": "Class: `Pbkdf2Params`", "type": "class", "name": "Pbkdf2Params", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`hash` Type: {string|Object}", "type": "string|Object", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
The number of iterations the PBKDF2 algorithm should make when deriving bits.
" }, { "textRaw": "`name` Type: {string} Must be `'PBKDF2'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Must be `'PBKDF2'`." }, { "textRaw": "`salt` Type: {ArrayBuffer|TypedArray|DataView|Buffer}", "type": "ArrayBuffer|TypedArray|DataView|Buffer", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "Should be at least 16 random or pseudorandom bytes.
" } ] }, { "textRaw": "Class: `RsaHashedImportParams`", "type": "class", "name": "RsaHashedImportParams", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`hash` Type: {string|Object}", "type": "string|Object", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
If represented as a <string>, the value must be one of:
\n'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If represented as an <Object>, the object must have a name
property\nwhose value is one of the above listed values.
The length in bits of the RSA modulus. As a best practice, this should be\nat least 2048
.
The RSA public exponent. This must be a <Uint8Array> containing a big-endian,\nunsigned integer that must fit within 32-bits. The <Uint8Array> may contain an\narbitrary number of leading zero-bits. The value must be a prime number. Unless\nthere is reason to use a different value, use new Uint8Array([1, 0, 1])
\n(65537) as the public exponent.
An additional collection of bytes that will not be encrypted, but will be bound\nto the generated ciphertext.
\nThe rsaOaepParams.label
parameter is optional.
The length (in bytes) of the random salt to use.
" } ] } ], "type": "module", "displayName": "Algorithm parameters" } ], "classes": [ { "textRaw": "Class: `Crypto`", "type": "class", "name": "Crypto", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "globalThis.crypto
is an instance of the Crypto
\nclass. Crypto
is a singleton that provides access to the remainder of the\ncrypto API.
Provides access to the SubtleCrypto
API.
Generates cryptographically strong random values. The given typedArray
is\nfilled with random values, and a reference to typedArray
is returned.
The given typedArray
must be an integer-based instance of <TypedArray>,\ni.e. Float32Array
and Float64Array
are not accepted.
An error will be thrown if the given typedArray
is larger than 65,536 bytes.
Generates a random RFC 4122 version 4 UUID. The UUID is generated using a\ncryptographic pseudorandom number generator.
" } ] }, { "textRaw": "Class: `CryptoKey`", "type": "class", "name": "CryptoKey", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "properties": [ { "textRaw": "`cryptoKey.algorithm`", "name": "algorithm", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "\nAn object detailing the algorithm for which the key can be used along with\nadditional algorithm-specific parameters.
\nRead-only.
" }, { "textRaw": "`extractable` Type: {boolean}", "type": "boolean", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "When true
, the <CryptoKey> can be extracted using either\nsubtleCrypto.exportKey()
or subtleCrypto.wrapKey()
.
Read-only.
" }, { "textRaw": "`type` Type: {string} One of `'secret'`, `'private'`, or `'public'`.", "type": "string", "name": "Type", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "desc": "A string identifying whether the key is a symmetric ('secret'
) or\nasymmetric ('private'
or 'public'
) key.
An array of strings identifying the operations for which the\nkey may be used.
\nThe possible usages are:
\n'encrypt'
- The key may be used to encrypt data.'decrypt'
- The key may be used to decrypt data.'sign'
- The key may be used to generate digital signatures.'verify'
- The key may be used to verify digital signatures.'deriveKey'
- The key may be used to derive a new key.'deriveBits'
- The key may be used to derive bits.'wrapKey'
- The key may be used to wrap another key.'unwrapKey'
- The key may be used to unwrap another key.Valid key usages depend on the key algorithm (identified by\ncryptokey.algorithm.name
).
Key Type | \n'encrypt' | \n'decrypt' | \n'sign' | \n'verify' | \n'deriveKey' | \n'deriveBits' | \n'wrapKey' | \n'unwrapKey' | \n
---|---|---|---|---|---|---|---|---|
'AES-CBC' | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n
'AES-CTR' | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n
'AES-GCM' | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n
'AES-KW' | \n\n | \n | \n | \n | \n | \n | ✔ | \n✔ | \n
'ECDH' | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n |
'X25519' 1 | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n |
'X448' 1 | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n |
'ECDSA' | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n |
'Ed25519' 1 | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n |
'Ed448' 1 | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n |
'HDKF' | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n |
'HMAC' | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n |
'PBKDF2' | \n\n | \n | \n | \n | ✔ | \n✔ | \n\n | \n |
'RSA-OAEP' | \n✔ | \n✔ | \n\n | \n | \n | \n | ✔ | \n✔ | \n
'RSA-PSS' | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n |
'RSASSA-PKCS1-v1_5' | \n\n | \n | ✔ | \n✔ | \n\n | \n | \n | \n |
The CryptoKeyPair
is a simple dictionary object with publicKey
and\nprivateKey
properties, representing an asymmetric key pair.
Using the method and parameters specified in algorithm
and the keying\nmaterial provided by key
, subtle.decrypt()
attempts to decipher the\nprovided data
. If successful, the returned promise will be resolved with\nan <ArrayBuffer> containing the plaintext result.
The algorithms currently supported include:
\n'RSA-OAEP'
'AES-CTR'
'AES-CBC'
'AES-GCM
'algorithm
: <AlgorithmIdentifier> | <EcdhKeyDeriveParams> | <HkdfParams> | <Pbkdf2Params>baseKey
: <CryptoKey>length
: <number> | <null>Using the method and parameters specified in algorithm
and the keying\nmaterial provided by baseKey
, subtle.deriveBits()
attempts to generate\nlength
bits.
The Node.js implementation requires that when length
is a\nnumber it must be multiple of 8
.
When length
is null
the maximum number of bits for a given algorithm is\ngenerated. This is allowed for the 'ECDH'
, 'X25519'
, and 'X448'
\nalgorithms.
If successful, the returned promise will be resolved with an <ArrayBuffer>\ncontaining the generated data.
\nThe algorithms currently supported include:
\n" }, { "textRaw": "`subtle.deriveKey(algorithm, baseKey, derivedKeyAlgorithm, extractable, keyUsages)`", "type": "method", "name": "deriveKey", "meta": { "added": [ "v15.0.0" ], "changes": [ { "version": [ "v18.4.0", "v16.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/42507", "description": "Added `'X25519'`, and `'X448'` algorithms." } ] }, "signatures": [ { "params": [] } ], "desc": "\nalgorithm
: <AlgorithmIdentifier> | <EcdhKeyDeriveParams> | <HkdfParams> | <Pbkdf2Params>baseKey
: <CryptoKey>derivedKeyAlgorithm
: <HmacKeyGenParams> | <AesKeyGenParams>extractable
: <boolean>keyUsages
: <string[]> See Key usages.Using the method and parameters specified in algorithm
, and the keying\nmaterial provided by baseKey
, subtle.deriveKey()
attempts to generate\na new <CryptoKey> based on the method and parameters in derivedKeyAlgorithm
.
Calling subtle.deriveKey()
is equivalent to calling subtle.deriveBits()
to\ngenerate raw keying material, then passing the result into the\nsubtle.importKey()
method using the deriveKeyAlgorithm
, extractable
, and\nkeyUsages
parameters as input.
The algorithms currently supported include:
\n" }, { "textRaw": "`subtle.digest(algorithm, data)`", "type": "method", "name": "digest", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise} Fulfills with an {ArrayBuffer}", "name": "return", "type": "Promise", "desc": "Fulfills with an {ArrayBuffer}" }, "params": [ { "textRaw": "`algorithm`: {string|Object}", "name": "algorithm", "type": "string|Object" }, { "textRaw": "`data`: {ArrayBuffer|TypedArray|DataView|Buffer}", "name": "data", "type": "ArrayBuffer|TypedArray|DataView|Buffer" } ] } ], "desc": "Using the method identified by algorithm
, subtle.digest()
attempts to\ngenerate a digest of data
. If successful, the returned promise is resolved\nwith an <ArrayBuffer> containing the computed digest.
If algorithm
is provided as a <string>, it must be one of:
'SHA-1'
'SHA-256'
'SHA-384'
'SHA-512'
If algorithm
is provided as an <Object>, it must have a name
property\nwhose value is one of the above.
Using the method and parameters specified by algorithm
and the keying\nmaterial provided by key
, subtle.encrypt()
attempts to encipher data
.\nIf successful, the returned promise is resolved with an <ArrayBuffer>\ncontaining the encrypted result.
The algorithms currently supported include:
\n'RSA-OAEP'
'AES-CTR'
'AES-CBC'
'AES-GCM
'Exports the given key into the specified format, if supported.
\nIf the <CryptoKey> is not extractable, the returned promise will reject.
\nWhen format
is either 'pkcs8'
or 'spki'
and the export is successful,\nthe returned promise will be resolved with an <ArrayBuffer> containing the\nexported key data.
When format
is 'jwk'
and the export is successful, the returned promise\nwill be resolved with a JavaScript object conforming to the JSON Web Key\nspecification.
Key Type | \n'spki' | \n'pkcs8' | \n'jwk' | \n'raw' | \n
---|---|---|---|---|
'AES-CBC' | \n\n | \n | ✔ | \n✔ | \n
'AES-CTR' | \n\n | \n | ✔ | \n✔ | \n
'AES-GCM' | \n\n | \n | ✔ | \n✔ | \n
'AES-KW' | \n\n | \n | ✔ | \n✔ | \n
'ECDH' | \n✔ | \n✔ | \n✔ | \n✔ | \n
'ECDSA' | \n✔ | \n✔ | \n✔ | \n✔ | \n
'Ed25519' 1 | \n✔ | \n✔ | \n✔ | \n✔ | \n
'Ed448' 1 | \n✔ | \n✔ | \n✔ | \n✔ | \n
'HDKF' | \n\n | \n | \n | \n |
'HMAC' | \n\n | \n | ✔ | \n✔ | \n
'PBKDF2' | \n\n | \n | \n | \n |
'RSA-OAEP' | \n✔ | \n✔ | \n✔ | \n\n |
'RSA-PSS' | \n✔ | \n✔ | \n✔ | \n\n |
'RSASSA-PKCS1-v1_5' | \n✔ | \n✔ | \n✔ | \n\n |
algorithm
: <AlgorithmIdentifier> | <RsaHashedKeyGenParams> | <EcKeyGenParams> | <HmacKeyGenParams> | <AesKeyGenParams>extractable
: <boolean>keyUsages
: <string[]> See Key usages.Using the method and parameters provided in algorithm
, subtle.generateKey()
\nattempts to generate new keying material. Depending the method used, the method\nmay generate either a single <CryptoKey> or a <CryptoKeyPair>.
The <CryptoKeyPair> (public and private key) generating algorithms supported\ninclude:
\n'RSASSA-PKCS1-v1_5'
'RSA-PSS'
'RSA-OAEP'
'ECDSA'
'Ed25519'
1'Ed448'
1'ECDH'
'X25519'
1'X448'
1The <CryptoKey> (secret key) generating algorithms supported include:
\n'HMAC'
'AES-CTR'
'AES-CBC'
'AES-GCM'
'AES-KW'
algorithm
: <AlgorithmIdentifier> | <RsaHashedImportParams> | <EcKeyImportParams> | <HmacImportParams>extractable
: <boolean>keyUsages
: <string[]> See Key usages.The subtle.importKey()
method attempts to interpret the provided keyData
\nas the given format
to create a <CryptoKey> instance using the provided\nalgorithm
, extractable
, and keyUsages
arguments. If the import is\nsuccessful, the returned promise will be resolved with the created <CryptoKey>.
If importing a 'PBKDF2'
key, extractable
must be false
.
The algorithms currently supported include:
\nKey Type | \n'spki' | \n'pkcs8' | \n'jwk' | \n'raw' | \n
---|---|---|---|---|
'AES-CBC' | \n\n | \n | ✔ | \n✔ | \n
'AES-CTR' | \n\n | \n | ✔ | \n✔ | \n
'AES-GCM' | \n\n | \n | ✔ | \n✔ | \n
'AES-KW' | \n\n | \n | ✔ | \n✔ | \n
'ECDH' | \n✔ | \n✔ | \n✔ | \n✔ | \n
'X25519' 1 | \n✔ | \n✔ | \n✔ | \n✔ | \n
'X448' 1 | \n✔ | \n✔ | \n✔ | \n✔ | \n
'ECDSA' | \n✔ | \n✔ | \n✔ | \n✔ | \n
'Ed25519' 1 | \n✔ | \n✔ | \n✔ | \n✔ | \n
'Ed448' 1 | \n✔ | \n✔ | \n✔ | \n✔ | \n
'HDKF' | \n\n | \n | \n | ✔ | \n
'HMAC' | \n\n | \n | ✔ | \n✔ | \n
'PBKDF2' | \n\n | \n | \n | ✔ | \n
'RSA-OAEP' | \n✔ | \n✔ | \n✔ | \n\n |
'RSA-PSS' | \n✔ | \n✔ | \n✔ | \n\n |
'RSASSA-PKCS1-v1_5' | \n✔ | \n✔ | \n✔ | \n\n |
algorithm
: <AlgorithmIdentifier> | <RsaPssParams> | <EcdsaParams> | <Ed448Params>key
: <CryptoKey>data
: <ArrayBuffer> | <TypedArray> | <DataView> | <Buffer>Using the method and parameters given by algorithm
and the keying material\nprovided by key
, subtle.sign()
attempts to generate a cryptographic\nsignature of data
. If successful, the returned promise is resolved with\nan <ArrayBuffer> containing the generated signature.
The algorithms currently supported include:
\n" }, { "textRaw": "`subtle.unwrapKey(format, wrappedKey, unwrappingKey, unwrapAlgo, unwrappedKeyAlgo, extractable, keyUsages)`", "type": "method", "name": "unwrapKey", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`format`: {string} Must be one of `'raw'`, `'pkcs8'`, `'spki'`, or `'jwk'`.", "name": "format", "type": "string", "desc": "Must be one of `'raw'`, `'pkcs8'`, `'spki'`, or `'jwk'`." }, { "textRaw": "`wrappedKey`: {ArrayBuffer|TypedArray|DataView|Buffer}", "name": "wrappedKey", "type": "ArrayBuffer|TypedArray|DataView|Buffer" }, { "textRaw": "`unwrappingKey`: {CryptoKey}", "name": "unwrappingKey", "type": "CryptoKey" } ] } ], "desc": "\nunwrapAlgo
: <AlgorithmIdentifier> | <RsaOaepParams> | <AesCtrParams> | <AesCbcParams> | <AesGcmParams>unwrappedKeyAlgo
: <AlgorithmIdentifier> | <RsaHashedImportParams> | <EcKeyImportParams> | <HmacImportParams>extractable
: <boolean>keyUsages
: <string[]> See Key usages.In cryptography, \"wrapping a key\" refers to exporting and then encrypting the\nkeying material. The subtle.unwrapKey()
method attempts to decrypt a wrapped\nkey and create a <CryptoKey> instance. It is equivalent to calling\nsubtle.decrypt()
first on the encrypted key data (using the wrappedKey
,\nunwrapAlgo
, and unwrappingKey
arguments as input) then passing the results\nin to the subtle.importKey()
method using the unwrappedKeyAlgo
,\nextractable
, and keyUsages
arguments as inputs. If successful, the returned\npromise is resolved with a <CryptoKey> object.
The wrapping algorithms currently supported include:
\n'RSA-OAEP'
'AES-CTR'
'AES-CBC'
'AES-GCM'
'AES-KW'
The unwrapped key algorithms supported include:
\n'RSASSA-PKCS1-v1_5'
'RSA-PSS'
'RSA-OAEP'
'ECDSA'
'Ed25519'
1'Ed448'
1'ECDH'
'X25519'
1'X448'
1'HMAC'
'AES-CTR'
'AES-CBC'
'AES-GCM'
'AES-KW'
algorithm
: <AlgorithmIdentifier> | <RsaPssParams> | <EcdsaParams> | <Ed448Params>key
: <CryptoKey>signature
: <ArrayBuffer> | <TypedArray> | <DataView> | <Buffer>data
: <ArrayBuffer> | <TypedArray> | <DataView> | <Buffer>Using the method and parameters given in algorithm
and the keying material\nprovided by key
, subtle.verify()
attempts to verify that signature
is\na valid cryptographic signature of data
. The returned promise is resolved\nwith either true
or false
.
The algorithms currently supported include:
\n" }, { "textRaw": "`subtle.wrapKey(format, key, wrappingKey, wrapAlgo)`", "type": "method", "name": "wrapKey", "meta": { "added": [ "v15.0.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "\nformat
: <string> Must be one of 'raw'
, 'pkcs8'
, 'spki'
, or 'jwk'
.key
: <CryptoKey>wrappingKey
: <CryptoKey>wrapAlgo
: <AlgorithmIdentifier> | <RsaOaepParams> | <AesCtrParams> | <AesCbcParams> | <AesGcmParams>In cryptography, \"wrapping a key\" refers to exporting and then encrypting the\nkeying material. The subtle.wrapKey()
method exports the keying material into\nthe format identified by format
, then encrypts it using the method and\nparameters specified by wrapAlgo
and the keying material provided by\nwrappingKey
. It is the equivalent to calling subtle.exportKey()
using\nformat
and key
as the arguments, then passing the result to the\nsubtle.encrypt()
method using wrappingKey
and wrapAlgo
as inputs. If\nsuccessful, the returned promise will be resolved with an <ArrayBuffer>\ncontaining the encrypted key data.
The wrapping algorithms currently supported include:
\n'RSA-OAEP'
'AES-CTR'
'AES-CBC'
'AES-GCM'
'AES-KW'
An implementation of the WHATWG Streams Standard.
", "modules": [ { "textRaw": "Overview", "name": "overview", "desc": "The WHATWG Streams Standard (or \"web streams\") defines an API for handling\nstreaming data. It is similar to the Node.js Streams API but emerged later\nand has become the \"standard\" API for streaming data across many JavaScript\nenvironments.
\nThere are three primary types of objects:
\nReadableStream
- Represents a source of streaming data.WritableStream
- Represents a destination for streaming data.TransformStream
- Represents an algorithm for transforming streaming data.ReadableStream
This example creates a simple ReadableStream
that pushes the current\nperformance.now()
timestamp once every second forever. An async iterable\nis used to read the data from the stream.
import {\n ReadableStream,\n} from 'node:stream/web';\n\nimport {\n setInterval as every,\n} from 'node:timers/promises';\n\nimport {\n performance,\n} from 'node:perf_hooks';\n\nconst SECOND = 1000;\n\nconst stream = new ReadableStream({\n async start(controller) {\n for await (const _ of every(SECOND))\n controller.enqueue(performance.now());\n },\n});\n\nfor await (const value of stream)\n console.log(value);\n
\nconst {\n ReadableStream,\n} = require('node:stream/web');\n\nconst {\n setInterval: every,\n} = require('node:timers/promises');\n\nconst {\n performance,\n} = require('node:perf_hooks');\n\nconst SECOND = 1000;\n\nconst stream = new ReadableStream({\n async start(controller) {\n for await (const _ of every(SECOND))\n controller.enqueue(performance.now());\n },\n});\n\n(async () => {\n for await (const value of stream)\n console.log(value);\n})();\n
",
"type": "module",
"displayName": "Overview"
},
{
"textRaw": "API",
"name": "api",
"classes": [
{
"textRaw": "Class: `ReadableStream`",
"type": "class",
"name": "ReadableStream",
"meta": {
"added": [
"v16.5.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/42225",
"description": "This class is now exposed on the global object."
}
]
},
"properties": [
{
"textRaw": "`locked` Type: {boolean} Set to `true` if there is an active reader for this {ReadableStream}.",
"type": "boolean",
"name": "Type",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
},
"desc": "The readableStream.locked
property is false
by default, and is\nswitched to true
while there is an active reader consuming the\nstream's data.
import { ReadableStream } from 'node:stream/web';\n\nconst stream = new ReadableStream();\n\nconst reader = stream.getReader();\n\nconsole.log(await reader.read());\n
\nconst { ReadableStream } = require('node:stream/web');\n\nconst stream = new ReadableStream();\n\nconst reader = stream.getReader();\n\nreader.read().then(console.log);\n
\nCauses the readableStream.locked
to be true
.
Connects this <ReadableStream> to the pair of <ReadableStream> and\n<WritableStream> provided in the transform
argument such that the\ndata from this <ReadableStream> is written in to transform.writable
,\npossibly transformed, then pushed to transform.readable
. Once the\npipeline is configured, transform.readable
is returned.
Causes the readableStream.locked
to be true
while the pipe operation\nis active.
import {\n ReadableStream,\n TransformStream,\n} from 'node:stream/web';\n\nconst stream = new ReadableStream({\n start(controller) {\n controller.enqueue('a');\n },\n});\n\nconst transform = new TransformStream({\n transform(chunk, controller) {\n controller.enqueue(chunk.toUpperCase());\n },\n});\n\nconst transformedStream = stream.pipeThrough(transform);\n\nfor await (const chunk of transformedStream)\n console.log(chunk);\n // Prints: A\n
\nconst {\n ReadableStream,\n TransformStream,\n} = require('node:stream/web');\n\nconst stream = new ReadableStream({\n start(controller) {\n controller.enqueue('a');\n },\n});\n\nconst transform = new TransformStream({\n transform(chunk, controller) {\n controller.enqueue(chunk.toUpperCase());\n },\n});\n\nconst transformedStream = stream.pipeThrough(transform);\n\n(async () => {\n for await (const chunk of transformedStream)\n console.log(chunk);\n // Prints: A\n})();\n
"
},
{
"textRaw": "`readableStream.pipeTo(destination[, options])`",
"type": "method",
"name": "pipeTo",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: A promise fulfilled with `undefined`",
"name": "return",
"desc": "A promise fulfilled with `undefined`"
},
"params": [
{
"textRaw": "`destination` {WritableStream} A {WritableStream} to which this `ReadableStream`'s data will be written.",
"name": "destination",
"type": "WritableStream",
"desc": "A {WritableStream} to which this `ReadableStream`'s data will be written."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`preventAbort` {boolean} When `true`, errors in this `ReadableStream` will not cause `destination` to be aborted.",
"name": "preventAbort",
"type": "boolean",
"desc": "When `true`, errors in this `ReadableStream` will not cause `destination` to be aborted."
},
{
"textRaw": "`preventCancel` {boolean} When `true`, errors in the `destination` will not cause this `ReadableStream` to be canceled.",
"name": "preventCancel",
"type": "boolean",
"desc": "When `true`, errors in the `destination` will not cause this `ReadableStream` to be canceled."
},
{
"textRaw": "`preventClose` {boolean} When `true`, closing this `ReadableStream` does not cause `destination` to be closed.",
"name": "preventClose",
"type": "boolean",
"desc": "When `true`, closing this `ReadableStream` does not cause `destination` to be closed."
},
{
"textRaw": "`signal` {AbortSignal} Allows the transfer of data to be canceled using an {AbortController}.",
"name": "signal",
"type": "AbortSignal",
"desc": "Allows the transfer of data to be canceled using an {AbortController}."
}
]
}
]
}
],
"desc": "Causes the readableStream.locked
to be true
while the pipe operation\nis active.
Returns a pair of new <ReadableStream> instances to which this\nReadableStream
's data will be forwarded. Each will receive the\nsame data.
Causes the readableStream.locked
to be true
.
Creates and returns an async iterator usable for consuming this\nReadableStream
's data.
Causes the readableStream.locked
to be true
while the async iterator\nis active.
import { Buffer } from 'node:buffer';\n\nconst stream = new ReadableStream(getSomeSource());\n\nfor await (const chunk of stream.values({ preventCancel: true }))\n console.log(Buffer.from(chunk).toString());\n
"
}
],
"modules": [
{
"textRaw": "Async Iteration",
"name": "async_iteration",
"desc": "The <ReadableStream> object supports the async iterator protocol using\nfor await
syntax.
import { Buffer } from 'node:buffer';\n\nconst stream = new ReadableStream(getSomeSource());\n\nfor await (const chunk of stream)\n console.log(Buffer.from(chunk).toString());\n
\nThe async iterator will consume the <ReadableStream> until it terminates.
\nBy default, if the async iterator exits early (via either a break
,\nreturn
, or a throw
), the <ReadableStream> will be closed. To prevent\nautomatic closing of the <ReadableStream>, use the readableStream.values()
\nmethod to acquire the async iterator and set the preventCancel
option to\ntrue
.
The <ReadableStream> must not be locked (that is, it must not have an existing\nactive reader). During the async iteration, the <ReadableStream> will be locked.
", "type": "module", "displayName": "Async Iteration" }, { "textRaw": "Transferring with `postMessage()`", "name": "transferring_with_`postmessage()`", "desc": "A <ReadableStream> instance can be transferred using a <MessagePort>.
\nconst stream = new ReadableStream(getReadableSourceSomehow());\n\nconst { port1, port2 } = new MessageChannel();\n\nport1.onmessage = ({ data }) => {\n data.getReader().read().then((chunk) => {\n console.log(chunk);\n });\n};\n\nport2.postMessage(stream, [stream]);\n
",
"type": "module",
"displayName": "Transferring with `postMessage()`"
}
],
"signatures": [
{
"params": [],
"desc": "\nunderlyingSource
<Object>\nstart
<Function> A user-defined function that is invoked immediately when\nthe ReadableStream
is created.\ncontroller
<ReadableStreamDefaultController> | <ReadableByteStreamController>undefined
or a promise fulfilled with undefined
.pull
<Function> A user-defined function that is called repeatedly when the\nReadableStream
internal queue is not full. The operation may be sync or\nasync. If async, the function will not be called again until the previously\nreturned promise is fulfilled.\ncontroller
<ReadableStreamDefaultController> | <ReadableByteStreamController>undefined
.cancel
<Function> A user-defined function that is called when the\nReadableStream
is canceled.\nreason
<any>undefined
.type
<string> Must be 'bytes'
or undefined
.autoAllocateChunkSize
<number> Used only when type
is equal to\n'bytes'
. When set to a non-zero value a view buffer is automatically\nallocated to ReadableByteStreamController.byobRequest
. When not set\none must use stream's internal queues to transfer data via the default\nreader ReadableStreamDefaultReader
.strategy
<Object>\nhighWaterMark
<number> The maximum internal queue size before backpressure\nis applied.size
<Function> A user-defined function used to identify the size of each\nchunk of data.\n\nBy default, calling readableStream.getReader()
with no arguments\nwill return an instance of ReadableStreamDefaultReader
. The default\nreader treats the chunks of data passed through the stream as opaque\nvalues, which allows the <ReadableStream> to work with generally any\nJavaScript value.
Cancels the <ReadableStream> and returns a promise that is fulfilled\nwhen the underlying stream has been canceled.
" }, { "textRaw": "`readableStreamDefaultReader.read()`", "type": "method", "name": "read", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: A promise fulfilled with an object:", "name": "return", "desc": "A promise fulfilled with an object:", "options": [ { "textRaw": "`value` {any}", "name": "value", "type": "any" }, { "textRaw": "`done` {boolean}", "name": "done", "type": "boolean" } ] }, "params": [] } ], "desc": "Requests the next chunk of data from the underlying <ReadableStream>\nand returns a promise that is fulfilled with the data once it is\navailable.
" }, { "textRaw": "`readableStreamDefaultReader.releaseLock()`", "type": "method", "name": "releaseLock", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Releases this reader's lock on the underlying <ReadableStream>.
" } ], "properties": [ { "textRaw": "`closed` Type: {Promise} Fulfilled with `undefined` when the associated {ReadableStream} is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing.", "type": "Promise", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "Fulfilled with `undefined` when the associated {ReadableStream} is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing." } ], "signatures": [ { "params": [ { "textRaw": "`stream` {ReadableStream}", "name": "stream", "type": "ReadableStream" } ], "desc": "Creates a new <ReadableStreamDefaultReader> that is locked to the\ngiven <ReadableStream>.
" } ] }, { "textRaw": "Class: `ReadableStreamBYOBReader`", "type": "class", "name": "ReadableStreamBYOBReader", "meta": { "added": [ "v16.5.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/42225", "description": "This class is now exposed on the global object." } ] }, "desc": "The ReadableStreamBYOBReader
is an alternative consumer for\nbyte-oriented <ReadableStream>s (those that are created with\nunderlyingSource.type
set equal to 'bytes'
when the\nReadableStream
was created).
The BYOB
is short for \"bring your own buffer\". This is a\npattern that allows for more efficient reading of byte-oriented\ndata that avoids extraneous copying.
import {\n open,\n} from 'node:fs/promises';\n\nimport {\n ReadableStream,\n} from 'node:stream/web';\n\nimport { Buffer } from 'node:buffer';\n\nclass Source {\n type = 'bytes';\n autoAllocateChunkSize = 1024;\n\n async start(controller) {\n this.file = await open(new URL(import.meta.url));\n this.controller = controller;\n }\n\n async pull(controller) {\n const view = controller.byobRequest?.view;\n const {\n bytesRead,\n } = await this.file.read({\n buffer: view,\n offset: view.byteOffset,\n length: view.byteLength,\n });\n\n if (bytesRead === 0) {\n await this.file.close();\n this.controller.close();\n }\n controller.byobRequest.respond(bytesRead);\n }\n}\n\nconst stream = new ReadableStream(new Source());\n\nasync function read(stream) {\n const reader = stream.getReader({ mode: 'byob' });\n\n const chunks = [];\n let result;\n do {\n result = await reader.read(Buffer.alloc(100));\n if (result.value !== undefined)\n chunks.push(Buffer.from(result.value));\n } while (!result.done);\n\n return Buffer.concat(chunks);\n}\n\nconst data = await read(stream);\nconsole.log(Buffer.from(data).toString());\n
",
"methods": [
{
"textRaw": "`readableStreamBYOBReader.cancel([reason])`",
"type": "method",
"name": "cancel",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
},
"params": [
{
"textRaw": "`reason` {any}",
"name": "reason",
"type": "any"
}
]
}
],
"desc": "Cancels the <ReadableStream> and returns a promise that is fulfilled\nwhen the underlying stream has been canceled.
" }, { "textRaw": "`readableStreamBYOBReader.read(view[, options])`", "type": "method", "name": "read", "meta": { "added": [ "v16.5.0" ], "changes": [ { "version": "v21.7.0", "pr-url": "https://github.com/nodejs/node/pull/50888", "description": "Added `min` option." } ] }, "signatures": [ { "return": { "textRaw": "Returns: A promise fulfilled with an object:", "name": "return", "desc": "A promise fulfilled with an object:", "options": [ { "textRaw": "`value` {TypedArray|DataView}", "name": "value", "type": "TypedArray|DataView" }, { "textRaw": "`done` {boolean}", "name": "done", "type": "boolean" } ] }, "params": [ { "textRaw": "`view` {Buffer|TypedArray|DataView}", "name": "view", "type": "Buffer|TypedArray|DataView" }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`min` {number} When set, the returned promise will only be fulfilled as soon as `min` number of elements are available. When not set, the promise fulfills when at least one element is available.", "name": "min", "type": "number", "desc": "When set, the returned promise will only be fulfilled as soon as `min` number of elements are available. When not set, the promise fulfills when at least one element is available." } ] } ] } ], "desc": "Requests the next chunk of data from the underlying <ReadableStream>\nand returns a promise that is fulfilled with the data once it is\navailable.
\nDo not pass a pooled <Buffer> object instance in to this method.\nPooled Buffer
objects are created using Buffer.allocUnsafe()
,\nor Buffer.from()
, or are often returned by various node:fs
module\ncallbacks. These types of Buffer
s use a shared underlying\n<ArrayBuffer> object that contains all of the data from all of\nthe pooled Buffer
instances. When a Buffer
, <TypedArray>,\nor <DataView> is passed in to readableStreamBYOBReader.read()
,\nthe view's underlying ArrayBuffer
is detached, invalidating\nall existing views that may exist on that ArrayBuffer
. This\ncan have disastrous consequences for your application.
Releases this reader's lock on the underlying <ReadableStream>.
" } ], "properties": [ { "textRaw": "`closed` Type: {Promise} Fulfilled with `undefined` when the associated {ReadableStream} is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing.", "type": "Promise", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "Fulfilled with `undefined` when the associated {ReadableStream} is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing." } ], "signatures": [ { "params": [ { "textRaw": "`stream` {ReadableStream}", "name": "stream", "type": "ReadableStream" } ], "desc": "Creates a new ReadableStreamBYOBReader
that is locked to the\ngiven <ReadableStream>.
Every <ReadableStream> has a controller that is responsible for\nthe internal state and management of the stream's queue. The\nReadableStreamDefaultController
is the default controller\nimplementation for ReadableStream
s that are not byte-oriented.
Closes the <ReadableStream> to which this controller is associated.
" }, { "textRaw": "`readableStreamDefaultController.enqueue([chunk])`", "type": "method", "name": "enqueue", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`chunk` {any}", "name": "chunk", "type": "any" } ] } ], "desc": "Appends a new chunk of data to the <ReadableStream>'s queue.
" }, { "textRaw": "`readableStreamDefaultController.error([error])`", "type": "method", "name": "error", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`error` {any}", "name": "error", "type": "any" } ] } ], "desc": "Signals an error that causes the <ReadableStream> to error and close.
" } ], "properties": [ { "textRaw": "`desiredSize` Type: {number}", "type": "number", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "Returns the amount of data remaining to fill the <ReadableStream>'s\nqueue.
" } ] }, { "textRaw": "Class: `ReadableByteStreamController`", "type": "class", "name": "ReadableByteStreamController", "meta": { "added": [ "v16.5.0" ], "changes": [ { "version": "v18.10.0", "pr-url": "https://github.com/nodejs/node/pull/44702", "description": "Support handling a BYOB pull request from a released reader." } ] }, "desc": "Every <ReadableStream> has a controller that is responsible for\nthe internal state and management of the stream's queue. The\nReadableByteStreamController
is for byte-oriented ReadableStream
s.
Returns the amount of data remaining to fill the <ReadableStream>'s\nqueue.
" }, { "textRaw": "`desiredSize` Type: {number}", "type": "number", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "Returns the amount of data remaining to fill the <ReadableStream>'s\nqueue.
" } ], "methods": [ { "textRaw": "`readableByteStreamController.close()`", "type": "method", "name": "close", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Closes the <ReadableStream> to which this controller is associated.
" }, { "textRaw": "`readableByteStreamController.enqueue(chunk)`", "type": "method", "name": "enqueue", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`chunk`: {Buffer|TypedArray|DataView}", "name": "chunk", "type": "Buffer|TypedArray|DataView" } ] } ], "desc": "Appends a new chunk of data to the <ReadableStream>'s queue.
" }, { "textRaw": "`readableByteStreamController.error([error])`", "type": "method", "name": "error", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`error` {any}", "name": "error", "type": "any" } ] } ], "desc": "Signals an error that causes the <ReadableStream> to error and close.
" } ] }, { "textRaw": "Class: `ReadableStreamBYOBRequest`", "type": "class", "name": "ReadableStreamBYOBRequest", "meta": { "added": [ "v16.5.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/42225", "description": "This class is now exposed on the global object." } ] }, "desc": "When using ReadableByteStreamController
in byte-oriented\nstreams, and when using the ReadableStreamBYOBReader
,\nthe readableByteStreamController.byobRequest
property\nprovides access to a ReadableStreamBYOBRequest
instance\nthat represents the current read request. The object\nis used to gain access to the ArrayBuffer
/TypedArray
\nthat has been provided for the read request to fill,\nand provides methods for signaling that the data has\nbeen provided.
Signals that a bytesWritten
number of bytes have been written\nto readableStreamBYOBRequest.view
.
Signals that the request has been fulfilled with bytes written\nto a new Buffer
, TypedArray
, or DataView
.
The WritableStream
is a destination to which stream data is sent.
import {\n WritableStream,\n} from 'node:stream/web';\n\nconst stream = new WritableStream({\n write(chunk) {\n console.log(chunk);\n },\n});\n\nawait stream.getWriter().write('Hello World');\n
",
"methods": [
{
"textRaw": "`writableStream.abort([reason])`",
"type": "method",
"name": "abort",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
},
"params": [
{
"textRaw": "`reason` {any}",
"name": "reason",
"type": "any"
}
]
}
],
"desc": "Abruptly terminates the WritableStream
. All queued writes will be\ncanceled with their associated promises rejected.
Closes the WritableStream
when no additional writes are expected.
Creates and returns a new writer instance that can be used to write\ndata into the WritableStream
.
The writableStream.locked
property is false
by default, and is\nswitched to true
while there is an active writer attached to this\nWritableStream
.
A <WritableStream> instance can be transferred using a <MessagePort>.
\nconst stream = new WritableStream(getWritableSinkSomehow());\n\nconst { port1, port2 } = new MessageChannel();\n\nport1.onmessage = ({ data }) => {\n data.getWriter().write('hello');\n};\n\nport2.postMessage(stream, [stream]);\n
",
"type": "module",
"displayName": "Transferring with postMessage()"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`underlyingSink` {Object}",
"name": "underlyingSink",
"type": "Object",
"options": [
{
"textRaw": "`start` {Function} A user-defined function that is invoked immediately when the `WritableStream` is created.",
"name": "start",
"type": "Function",
"desc": "A user-defined function that is invoked immediately when the `WritableStream` is created.",
"options": [
{
"textRaw": "`controller` {WritableStreamDefaultController}",
"name": "controller",
"type": "WritableStreamDefaultController"
},
{
"textRaw": "Returns: `undefined` or a promise fulfilled with `undefined`.",
"name": "return",
"desc": "`undefined` or a promise fulfilled with `undefined`."
}
]
},
{
"textRaw": "`write` {Function} A user-defined function that is invoked when a chunk of data has been written to the `WritableStream`.",
"name": "write",
"type": "Function",
"desc": "A user-defined function that is invoked when a chunk of data has been written to the `WritableStream`.",
"options": [
{
"textRaw": "`chunk` {any}",
"name": "chunk",
"type": "any"
},
{
"textRaw": "`controller` {WritableStreamDefaultController}",
"name": "controller",
"type": "WritableStreamDefaultController"
},
{
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
}
]
},
{
"textRaw": "`close` {Function} A user-defined function that is called when the `WritableStream` is closed.",
"name": "close",
"type": "Function",
"desc": "A user-defined function that is called when the `WritableStream` is closed.",
"options": [
{
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
}
]
},
{
"textRaw": "`abort` {Function} A user-defined function that is called to abruptly close the `WritableStream`.",
"name": "abort",
"type": "Function",
"desc": "A user-defined function that is called to abruptly close the `WritableStream`.",
"options": [
{
"textRaw": "`reason` {any}",
"name": "reason",
"type": "any"
},
{
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
}
]
},
{
"textRaw": "`type` {any} The `type` option is reserved for future use and _must_ be undefined.",
"name": "type",
"type": "any",
"desc": "The `type` option is reserved for future use and _must_ be undefined."
}
]
},
{
"textRaw": "`strategy` {Object}",
"name": "strategy",
"type": "Object",
"options": [
{
"textRaw": "`highWaterMark` {number} The maximum internal queue size before backpressure is applied.",
"name": "highWaterMark",
"type": "number",
"desc": "The maximum internal queue size before backpressure is applied."
},
{
"textRaw": "`size` {Function} A user-defined function used to identify the size of each chunk of data.",
"name": "size",
"type": "Function",
"desc": "A user-defined function used to identify the size of each chunk of data.",
"options": [
{
"textRaw": "`chunk` {any}",
"name": "chunk",
"type": "any"
},
{
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
}
]
}
]
}
]
}
]
},
{
"textRaw": "Class: `WritableStreamDefaultWriter`",
"type": "class",
"name": "WritableStreamDefaultWriter",
"meta": {
"added": [
"v16.5.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/42225",
"description": "This class is now exposed on the global object."
}
]
},
"methods": [
{
"textRaw": "`writableStreamDefaultWriter.abort([reason])`",
"type": "method",
"name": "abort",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
},
"params": [
{
"textRaw": "`reason` {any}",
"name": "reason",
"type": "any"
}
]
}
],
"desc": "Abruptly terminates the WritableStream
. All queued writes will be\ncanceled with their associated promises rejected.
Closes the WritableStream
when no additional writes are expected.
Releases this writer's lock on the underlying <ReadableStream>.
" }, { "textRaw": "`writableStreamDefaultWriter.write([chunk])`", "type": "method", "name": "write", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: A promise fulfilled with `undefined`.", "name": "return", "desc": "A promise fulfilled with `undefined`." }, "params": [ { "textRaw": "`chunk`: {any}", "name": "chunk", "type": "any" } ] } ], "desc": "Appends a new chunk of data to the <WritableStream>'s queue.
" } ], "properties": [ { "textRaw": "`closed` Type: {Promise} Fulfilled with `undefined` when the associated {WritableStream} is closed or rejected if the stream errors or the writer's lock is released before the stream finishes closing.", "type": "Promise", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "Fulfilled with `undefined` when the associated {WritableStream} is closed or rejected if the stream errors or the writer's lock is released before the stream finishes closing." }, { "textRaw": "`desiredSize` Type: {number}", "type": "number", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "The amount of data required to fill the <WritableStream>'s queue.
" }, { "textRaw": "`ready` Type: {Promise} Fulfilled with `undefined` when the writer is ready to be used.", "type": "Promise", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "desc": "Fulfilled with `undefined` when the writer is ready to be used." } ], "signatures": [ { "params": [ { "textRaw": "`stream` {WritableStream}", "name": "stream", "type": "WritableStream" } ], "desc": "Creates a new WritableStreamDefaultWriter
that is locked to the given\nWritableStream
.
The WritableStreamDefaultController
manage's the <WritableStream>'s\ninternal state.
Called by user-code to signal that an error has occurred while processing\nthe WritableStream
data. When called, the <WritableStream> will be aborted,\nwith currently pending writes canceled.
A TransformStream
consists of a <ReadableStream> and a <WritableStream> that\nare connected such that the data written to the WritableStream
is received,\nand potentially transformed, before being pushed into the ReadableStream
's\nqueue.
import {\n TransformStream,\n} from 'node:stream/web';\n\nconst transform = new TransformStream({\n transform(chunk, controller) {\n controller.enqueue(chunk.toUpperCase());\n },\n});\n\nawait Promise.all([\n transform.writable.getWriter().write('A'),\n transform.readable.getReader().read(),\n]);\n
",
"properties": [
{
"textRaw": "`readable` Type: {ReadableStream}",
"type": "ReadableStream",
"name": "Type",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
}
},
{
"textRaw": "`writable` Type: {WritableStream}",
"type": "WritableStream",
"name": "Type",
"meta": {
"added": [
"v16.5.0"
],
"changes": []
}
}
],
"modules": [
{
"textRaw": "Transferring with postMessage()",
"name": "transferring_with_postmessage()",
"desc": "A <TransformStream> instance can be transferred using a <MessagePort>.
\nconst stream = new TransformStream();\n\nconst { port1, port2 } = new MessageChannel();\n\nport1.onmessage = ({ data }) => {\n const { writable, readable } = data;\n // ...\n};\n\nport2.postMessage(stream, [stream]);\n
",
"type": "module",
"displayName": "Transferring with postMessage()"
}
],
"signatures": [
{
"params": [
{
"textRaw": "`transformer` {Object}",
"name": "transformer",
"type": "Object",
"options": [
{
"textRaw": "`start` {Function} A user-defined function that is invoked immediately when the `TransformStream` is created.",
"name": "start",
"type": "Function",
"desc": "A user-defined function that is invoked immediately when the `TransformStream` is created.",
"options": [
{
"textRaw": "`controller` {TransformStreamDefaultController}",
"name": "controller",
"type": "TransformStreamDefaultController"
},
{
"textRaw": "Returns: `undefined` or a promise fulfilled with `undefined`",
"name": "return",
"desc": "`undefined` or a promise fulfilled with `undefined`"
}
]
},
{
"textRaw": "`transform` {Function} A user-defined function that receives, and potentially modifies, a chunk of data written to `transformStream.writable`, before forwarding that on to `transformStream.readable`.",
"name": "transform",
"type": "Function",
"desc": "A user-defined function that receives, and potentially modifies, a chunk of data written to `transformStream.writable`, before forwarding that on to `transformStream.readable`.",
"options": [
{
"textRaw": "`chunk` {any}",
"name": "chunk",
"type": "any"
},
{
"textRaw": "`controller` {TransformStreamDefaultController}",
"name": "controller",
"type": "TransformStreamDefaultController"
},
{
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
}
]
},
{
"textRaw": "`flush` {Function} A user-defined function that is called immediately before the writable side of the `TransformStream` is closed, signaling the end of the transformation process.",
"name": "flush",
"type": "Function",
"desc": "A user-defined function that is called immediately before the writable side of the `TransformStream` is closed, signaling the end of the transformation process.",
"options": [
{
"textRaw": "`controller` {TransformStreamDefaultController}",
"name": "controller",
"type": "TransformStreamDefaultController"
},
{
"textRaw": "Returns: A promise fulfilled with `undefined`.",
"name": "return",
"desc": "A promise fulfilled with `undefined`."
}
]
},
{
"textRaw": "`readableType` {any} the `readableType` option is reserved for future use and _must_ be `undefined`.",
"name": "readableType",
"type": "any",
"desc": "the `readableType` option is reserved for future use and _must_ be `undefined`."
},
{
"textRaw": "`writableType` {any} the `writableType` option is reserved for future use and _must_ be `undefined`.",
"name": "writableType",
"type": "any",
"desc": "the `writableType` option is reserved for future use and _must_ be `undefined`."
}
]
},
{
"textRaw": "`writableStrategy` {Object}",
"name": "writableStrategy",
"type": "Object",
"options": [
{
"textRaw": "`highWaterMark` {number} The maximum internal queue size before backpressure is applied.",
"name": "highWaterMark",
"type": "number",
"desc": "The maximum internal queue size before backpressure is applied."
},
{
"textRaw": "`size` {Function} A user-defined function used to identify the size of each chunk of data.",
"name": "size",
"type": "Function",
"desc": "A user-defined function used to identify the size of each chunk of data.",
"options": [
{
"textRaw": "`chunk` {any}",
"name": "chunk",
"type": "any"
},
{
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
}
]
}
]
},
{
"textRaw": "`readableStrategy` {Object}",
"name": "readableStrategy",
"type": "Object",
"options": [
{
"textRaw": "`highWaterMark` {number} The maximum internal queue size before backpressure is applied.",
"name": "highWaterMark",
"type": "number",
"desc": "The maximum internal queue size before backpressure is applied."
},
{
"textRaw": "`size` {Function} A user-defined function used to identify the size of each chunk of data.",
"name": "size",
"type": "Function",
"desc": "A user-defined function used to identify the size of each chunk of data.",
"options": [
{
"textRaw": "`chunk` {any}",
"name": "chunk",
"type": "any"
},
{
"textRaw": "Returns: {number}",
"name": "return",
"type": "number"
}
]
}
]
}
]
}
]
},
{
"textRaw": "Class: `TransformStreamDefaultController`",
"type": "class",
"name": "TransformStreamDefaultController",
"meta": {
"added": [
"v16.5.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/42225",
"description": "This class is now exposed on the global object."
}
]
},
"desc": "The TransformStreamDefaultController
manages the internal state\nof the TransformStream
.
The amount of data required to fill the readable side's queue.
" } ], "methods": [ { "textRaw": "`transformStreamDefaultController.enqueue([chunk])`", "type": "method", "name": "enqueue", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`chunk` {any}", "name": "chunk", "type": "any" } ] } ], "desc": "Appends a chunk of data to the readable side's queue.
" }, { "textRaw": "`transformStreamDefaultController.error([reason])`", "type": "method", "name": "error", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`reason` {any}", "name": "reason", "type": "any" } ] } ], "desc": "Signals to both the readable and writable side that an error has occurred\nwhile processing the transform data, causing both sides to be abruptly\nclosed.
" }, { "textRaw": "`transformStreamDefaultController.terminate()`", "type": "method", "name": "terminate", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Closes the readable side of the transport and causes the writable side\nto be abruptly closed with an error.
" } ] }, { "textRaw": "Class: `ByteLengthQueuingStrategy`", "type": "class", "name": "ByteLengthQueuingStrategy", "meta": { "added": [ "v16.5.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/42225", "description": "This class is now exposed on the global object." } ] }, "properties": [ { "textRaw": "`highWaterMark` Type: {number}", "type": "number", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] } }, { "textRaw": "`size` Type: {Function}", "type": "Function", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "options": [ { "textRaw": "`chunk` {any}", "name": "chunk", "type": "any" }, { "textRaw": "Returns: {number}", "name": "return", "type": "number" } ] } ], "signatures": [ { "params": [ { "textRaw": "`init` {Object}", "name": "init", "type": "Object", "options": [ { "textRaw": "`highWaterMark` {number}", "name": "highWaterMark", "type": "number" } ] } ] } ] }, { "textRaw": "Class: `CountQueuingStrategy`", "type": "class", "name": "CountQueuingStrategy", "meta": { "added": [ "v16.5.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/42225", "description": "This class is now exposed on the global object." } ] }, "properties": [ { "textRaw": "`highWaterMark` Type: {number}", "type": "number", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] } }, { "textRaw": "`size` Type: {Function}", "type": "Function", "name": "Type", "meta": { "added": [ "v16.5.0" ], "changes": [] }, "options": [ { "textRaw": "`chunk` {any}", "name": "chunk", "type": "any" }, { "textRaw": "Returns: {number}", "name": "return", "type": "number" } ] } ], "signatures": [ { "params": [ { "textRaw": "`init` {Object}", "name": "init", "type": "Object", "options": [ { "textRaw": "`highWaterMark` {number}", "name": "highWaterMark", "type": "number" } ] } ] } ] }, { "textRaw": "Class: `TextEncoderStream`", "type": "class", "name": "TextEncoderStream", "meta": { "added": [ "v16.6.0" ], "changes": [ { "version": "v18.0.0", "pr-url": "https://github.com/nodejs/node/pull/42225", "description": "This class is now exposed on the global object." } ] }, "properties": [ { "textRaw": "`encoding` Type: {string}", "type": "string", "name": "Type", "meta": { "added": [ "v16.6.0" ], "changes": [] }, "desc": "The encoding supported by the TextEncoderStream
instance.
Creates a new TextEncoderStream
instance.
The encoding supported by the TextDecoderStream
instance.
The value will be true
if decoding errors result in a TypeError
being\nthrown.
The value will be true
if the decoding result will include the byte order\nmark.
Creates a new TextDecoderStream
instance.
A utility method that creates a new <ReadableStream> from an iterable.
\nimport { ReadableStream } from 'node:stream/web';\n\nasync function* asyncIterableGenerator() {\n yield 'a';\n yield 'b';\n yield 'c';\n}\n\nconst stream = ReadableStream.from(asyncIterableGenerator());\n\nfor await (const chunk of stream)\n console.log(chunk); // Prints: 'a', 'b', 'c'\n
\nconst { ReadableStream } = require('node:stream/web');\n\nasync function* asyncIterableGenerator() {\n yield 'a';\n yield 'b';\n yield 'c';\n}\n\n(async () => {\n const stream = ReadableStream.from(asyncIterableGenerator());\n\n for await (const chunk of stream)\n console.log(chunk); // Prints: 'a', 'b', 'c'\n})();\n
"
}
],
"modules": [
{
"textRaw": "Utility Consumers",
"name": "utility_consumers",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"desc": "The utility consumer functions provide common options for consuming\nstreams.
\nThey are accessed using:
\nimport {\n arrayBuffer,\n blob,\n buffer,\n json,\n text,\n} from 'node:stream/consumers';\n
\nconst {\n arrayBuffer,\n blob,\n buffer,\n json,\n text,\n} = require('node:stream/consumers');\n
",
"methods": [
{
"textRaw": "`streamConsumers.arrayBuffer(stream)`",
"type": "method",
"name": "arrayBuffer",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with an `ArrayBuffer` containing the full contents of the stream.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with an `ArrayBuffer` containing the full contents of the stream."
},
"params": [
{
"textRaw": "`stream` {ReadableStream|stream.Readable|AsyncIterator}",
"name": "stream",
"type": "ReadableStream|stream.Readable|AsyncIterator"
}
]
}
],
"desc": "import { arrayBuffer } from 'node:stream/consumers';\nimport { Readable } from 'node:stream';\nimport { TextEncoder } from 'node:util';\n\nconst encoder = new TextEncoder();\nconst dataArray = encoder.encode('hello world from consumers!');\n\nconst readable = Readable.from(dataArray);\nconst data = await arrayBuffer(readable);\nconsole.log(`from readable: ${data.byteLength}`);\n// Prints: from readable: 76\n
\nconst { arrayBuffer } = require('node:stream/consumers');\nconst { Readable } = require('node:stream');\nconst { TextEncoder } = require('node:util');\n\nconst encoder = new TextEncoder();\nconst dataArray = encoder.encode('hello world from consumers!');\nconst readable = Readable.from(dataArray);\narrayBuffer(readable).then((data) => {\n console.log(`from readable: ${data.byteLength}`);\n // Prints: from readable: 76\n});\n
"
},
{
"textRaw": "`streamConsumers.blob(stream)`",
"type": "method",
"name": "blob",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with a {Blob} containing the full contents of the stream.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with a {Blob} containing the full contents of the stream."
},
"params": [
{
"textRaw": "`stream` {ReadableStream|stream.Readable|AsyncIterator}",
"name": "stream",
"type": "ReadableStream|stream.Readable|AsyncIterator"
}
]
}
],
"desc": "import { blob } from 'node:stream/consumers';\n\nconst dataBlob = new Blob(['hello world from consumers!']);\n\nconst readable = dataBlob.stream();\nconst data = await blob(readable);\nconsole.log(`from readable: ${data.size}`);\n// Prints: from readable: 27\n
\nconst { blob } = require('node:stream/consumers');\n\nconst dataBlob = new Blob(['hello world from consumers!']);\n\nconst readable = dataBlob.stream();\nblob(readable).then((data) => {\n console.log(`from readable: ${data.size}`);\n // Prints: from readable: 27\n});\n
"
},
{
"textRaw": "`streamConsumers.buffer(stream)`",
"type": "method",
"name": "buffer",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with a {Buffer} containing the full contents of the stream.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with a {Buffer} containing the full contents of the stream."
},
"params": [
{
"textRaw": "`stream` {ReadableStream|stream.Readable|AsyncIterator}",
"name": "stream",
"type": "ReadableStream|stream.Readable|AsyncIterator"
}
]
}
],
"desc": "import { buffer } from 'node:stream/consumers';\nimport { Readable } from 'node:stream';\nimport { Buffer } from 'node:buffer';\n\nconst dataBuffer = Buffer.from('hello world from consumers!');\n\nconst readable = Readable.from(dataBuffer);\nconst data = await buffer(readable);\nconsole.log(`from readable: ${data.length}`);\n// Prints: from readable: 27\n
\nconst { buffer } = require('node:stream/consumers');\nconst { Readable } = require('node:stream');\nconst { Buffer } = require('node:buffer');\n\nconst dataBuffer = Buffer.from('hello world from consumers!');\n\nconst readable = Readable.from(dataBuffer);\nbuffer(readable).then((data) => {\n console.log(`from readable: ${data.length}`);\n // Prints: from readable: 27\n});\n
"
},
{
"textRaw": "`streamConsumers.json(stream)`",
"type": "method",
"name": "json",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with the contents of the stream parsed as a UTF-8 encoded string that is then passed through `JSON.parse()`.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with the contents of the stream parsed as a UTF-8 encoded string that is then passed through `JSON.parse()`."
},
"params": [
{
"textRaw": "`stream` {ReadableStream|stream.Readable|AsyncIterator}",
"name": "stream",
"type": "ReadableStream|stream.Readable|AsyncIterator"
}
]
}
],
"desc": "import { json } from 'node:stream/consumers';\nimport { Readable } from 'node:stream';\n\nconst items = Array.from(\n {\n length: 100,\n },\n () => ({\n message: 'hello world from consumers!',\n }),\n);\n\nconst readable = Readable.from(JSON.stringify(items));\nconst data = await json(readable);\nconsole.log(`from readable: ${data.length}`);\n// Prints: from readable: 100\n
\nconst { json } = require('node:stream/consumers');\nconst { Readable } = require('node:stream');\n\nconst items = Array.from(\n {\n length: 100,\n },\n () => ({\n message: 'hello world from consumers!',\n }),\n);\n\nconst readable = Readable.from(JSON.stringify(items));\njson(readable).then((data) => {\n console.log(`from readable: ${data.length}`);\n // Prints: from readable: 100\n});\n
"
},
{
"textRaw": "`streamConsumers.text(stream)`",
"type": "method",
"name": "text",
"meta": {
"added": [
"v16.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise} Fulfills with the contents of the stream parsed as a UTF-8 encoded string.",
"name": "return",
"type": "Promise",
"desc": "Fulfills with the contents of the stream parsed as a UTF-8 encoded string."
},
"params": [
{
"textRaw": "`stream` {ReadableStream|stream.Readable|AsyncIterator}",
"name": "stream",
"type": "ReadableStream|stream.Readable|AsyncIterator"
}
]
}
],
"desc": "import { text } from 'node:stream/consumers';\nimport { Readable } from 'node:stream';\n\nconst readable = Readable.from('Hello world from consumers!');\nconst data = await text(readable);\nconsole.log(`from readable: ${data.length}`);\n// Prints: from readable: 27\n
\nconst { text } = require('node:stream/consumers');\nconst { Readable } = require('node:stream');\n\nconst readable = Readable.from('Hello world from consumers!');\ntext(readable).then((data) => {\n console.log(`from readable: ${data.length}`);\n // Prints: from readable: 27\n});\n
"
}
],
"type": "module",
"displayName": "Utility Consumers"
}
],
"type": "module",
"displayName": "API"
}
],
"type": "module",
"displayName": "Web Streams API",
"source": "doc/api/webstreams.md"
},
{
"textRaw": "Worker threads",
"name": "worker_threads",
"introduced_in": "v10.5.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "Source Code: lib/worker_threads.js
\nThe node:worker_threads
module enables the use of threads that execute\nJavaScript in parallel. To access it:
const worker = require('node:worker_threads');\n
\nWorkers (threads) are useful for performing CPU-intensive JavaScript operations.\nThey do not help much with I/O-intensive work. The Node.js built-in\nasynchronous I/O operations are more efficient than Workers can be.
\nUnlike child_process
or cluster
, worker_threads
can share memory. They do\nso by transferring ArrayBuffer
instances or sharing SharedArrayBuffer
\ninstances.
const {\n Worker, isMainThread, parentPort, workerData,\n} = require('node:worker_threads');\n\nif (isMainThread) {\n module.exports = function parseJSAsync(script) {\n return new Promise((resolve, reject) => {\n const worker = new Worker(__filename, {\n workerData: script,\n });\n worker.on('message', resolve);\n worker.on('error', reject);\n worker.on('exit', (code) => {\n if (code !== 0)\n reject(new Error(`Worker stopped with exit code ${code}`));\n });\n });\n };\n} else {\n const { parse } = require('some-js-parsing-library');\n const script = workerData;\n parentPort.postMessage(parse(script));\n}\n
\nThe above example spawns a Worker thread for each parseJSAsync()
call. In\npractice, use a pool of Workers for these kinds of tasks. Otherwise, the\noverhead of creating Workers would likely exceed their benefit.
When implementing a worker pool, use the AsyncResource
API to inform\ndiagnostic tools (e.g. to provide asynchronous stack traces) about the\ncorrelation between tasks and their outcomes. See\n\"Using AsyncResource
for a Worker
thread pool\"\nin the async_hooks
documentation for an example implementation.
Worker threads inherit non-process-specific options by default. Refer to\nWorker constructor options
to know how to customize worker thread options,\nspecifically argv
and execArgv
options.
Within a worker thread, worker.getEnvironmentData()
returns a clone\nof data passed to the spawning thread's worker.setEnvironmentData()
.\nEvery new Worker
receives its own copy of the environment data\nautomatically.
const {\n Worker,\n isMainThread,\n setEnvironmentData,\n getEnvironmentData,\n} = require('node:worker_threads');\n\nif (isMainThread) {\n setEnvironmentData('Hello', 'World!');\n const worker = new Worker(__filename);\n} else {\n console.log(getEnvironmentData('Hello')); // Prints 'World!'.\n}\n
"
},
{
"textRaw": "`worker.markAsUntransferable(object)`",
"type": "method",
"name": "markAsUntransferable",
"meta": {
"added": [
"v14.5.0",
"v12.19.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`object` {any} Any arbitrary JavaScript value.",
"name": "object",
"type": "any",
"desc": "Any arbitrary JavaScript value."
}
]
}
],
"desc": "Mark an object as not transferable. If object
occurs in the transfer list of\na port.postMessage()
call, an error is thrown. This is a no-op if\nobject
is a primitive value.
In particular, this makes sense for objects that can be cloned, rather than\ntransferred, and which are used by other objects on the sending side.\nFor example, Node.js marks the ArrayBuffer
s it uses for its\nBuffer
pool with this.
This operation cannot be undone.
\nconst { MessageChannel, markAsUntransferable } = require('node:worker_threads');\n\nconst pooledBuffer = new ArrayBuffer(8);\nconst typedArray1 = new Uint8Array(pooledBuffer);\nconst typedArray2 = new Float64Array(pooledBuffer);\n\nmarkAsUntransferable(pooledBuffer);\n\nconst { port1 } = new MessageChannel();\ntry {\n // This will throw an error, because pooledBuffer is not transferable.\n port1.postMessage(typedArray1, [ typedArray1.buffer ]);\n} catch (error) {\n // error.name === 'DataCloneError'\n}\n\n// The following line prints the contents of typedArray1 -- it still owns\n// its memory and has not been transferred. Without\n// `markAsUntransferable()`, this would print an empty Uint8Array and the\n// postMessage call would have succeeded.\n// typedArray2 is intact as well.\nconsole.log(typedArray1);\nconsole.log(typedArray2);\n
\nThere is no equivalent to this API in browsers.
" }, { "textRaw": "`worker.isMarkedAsUntransferable(object)`", "type": "method", "name": "isMarkedAsUntransferable", "meta": { "added": [ "v21.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`object` {any} Any JavaScript value.", "name": "object", "type": "any", "desc": "Any JavaScript value." } ] } ], "desc": "Check if an object is marked as not transferable with\nmarkAsUntransferable()
.
const { markAsUntransferable, isMarkedAsUntransferable } = require('node:worker_threads');\n\nconst pooledBuffer = new ArrayBuffer(8);\nmarkAsUntransferable(pooledBuffer);\n\nisMarkedAsUntransferable(pooledBuffer); // Returns true.\n
\nThere is no equivalent to this API in browsers.
" }, { "textRaw": "`worker.moveMessagePortToContext(port, contextifiedSandbox)`", "type": "method", "name": "moveMessagePortToContext", "meta": { "added": [ "v11.13.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {MessagePort}", "name": "return", "type": "MessagePort" }, "params": [ { "textRaw": "`port` {MessagePort} The message port to transfer.", "name": "port", "type": "MessagePort", "desc": "The message port to transfer." }, { "textRaw": "`contextifiedSandbox` {Object} A [contextified][] object as returned by the `vm.createContext()` method.", "name": "contextifiedSandbox", "type": "Object", "desc": "A [contextified][] object as returned by the `vm.createContext()` method." } ] } ], "desc": "Transfer a MessagePort
to a different vm
Context. The original port
\nobject is rendered unusable, and the returned MessagePort
instance\ntakes its place.
The returned MessagePort
is an object in the target context and\ninherits from its global Object
class. Objects passed to the\nport.onmessage()
listener are also created in the target context\nand inherit from its global Object
class.
However, the created MessagePort
no longer inherits from\nEventTarget
, and only port.onmessage()
can be used to receive\nevents using it.
Receive a single message from a given MessagePort
. If no message is available,\nundefined
is returned, otherwise an object with a single message
property\nthat contains the message payload, corresponding to the oldest message in the\nMessagePort
's queue.
const { MessageChannel, receiveMessageOnPort } = require('node:worker_threads');\nconst { port1, port2 } = new MessageChannel();\nport1.postMessage({ hello: 'world' });\n\nconsole.log(receiveMessageOnPort(port2));\n// Prints: { message: { hello: 'world' } }\nconsole.log(receiveMessageOnPort(port2));\n// Prints: undefined\n
\nWhen this function is used, no 'message'
event is emitted and the\nonmessage
listener is not invoked.
The worker.setEnvironmentData()
API sets the content of\nworker.getEnvironmentData()
in the current thread and all new Worker
\ninstances spawned from the current context.
Is true
if this code is not running inside of a Worker
thread.
const { Worker, isMainThread } = require('node:worker_threads');\n\nif (isMainThread) {\n // This re-loads the current file inside a Worker instance.\n new Worker(__filename);\n} else {\n console.log('Inside Worker!');\n console.log(isMainThread); // Prints 'false'.\n}\n
"
},
{
"textRaw": "`parentPort` {null|MessagePort}",
"type": "null|MessagePort",
"name": "parentPort",
"meta": {
"added": [
"v10.5.0"
],
"changes": []
},
"desc": "If this thread is a Worker
, this is a MessagePort
\nallowing communication with the parent thread. Messages sent using\nparentPort.postMessage()
are available in the parent thread\nusing worker.on('message')
, and messages sent from the parent thread\nusing worker.postMessage()
are available in this thread using\nparentPort.on('message')
.
const { Worker, isMainThread, parentPort } = require('node:worker_threads');\n\nif (isMainThread) {\n const worker = new Worker(__filename);\n worker.once('message', (message) => {\n console.log(message); // Prints 'Hello, world!'.\n });\n worker.postMessage('Hello, world!');\n} else {\n // When a message from the parent thread is received, send it back:\n parentPort.once('message', (message) => {\n parentPort.postMessage(message);\n });\n}\n
"
},
{
"textRaw": "`resourceLimits` {Object}",
"type": "Object",
"name": "resourceLimits",
"meta": {
"added": [
"v13.2.0",
"v12.16.0"
],
"changes": []
},
"options": [
{
"textRaw": "`maxYoungGenerationSizeMb` {number}",
"name": "maxYoungGenerationSizeMb",
"type": "number"
},
{
"textRaw": "`maxOldGenerationSizeMb` {number}",
"name": "maxOldGenerationSizeMb",
"type": "number"
},
{
"textRaw": "`codeRangeSizeMb` {number}",
"name": "codeRangeSizeMb",
"type": "number"
},
{
"textRaw": "`stackSizeMb` {number}",
"name": "stackSizeMb",
"type": "number"
}
],
"desc": "Provides the set of JS engine resource constraints inside this Worker thread.\nIf the resourceLimits
option was passed to the Worker
constructor,\nthis matches its values.
If this is used in the main thread, its value is an empty object.
" }, { "textRaw": "`SHARE_ENV` {symbol}", "type": "symbol", "name": "SHARE_ENV", "meta": { "added": [ "v11.14.0" ], "changes": [] }, "desc": "A special value that can be passed as the env
option of the Worker
\nconstructor, to indicate that the current thread and the Worker thread should\nshare read and write access to the same set of environment variables.
const { Worker, SHARE_ENV } = require('node:worker_threads');\nnew Worker('process.env.SET_IN_WORKER = \"foo\"', { eval: true, env: SHARE_ENV })\n .on('exit', () => {\n console.log(process.env.SET_IN_WORKER); // Prints 'foo'.\n });\n
"
},
{
"textRaw": "`threadId` {integer}",
"type": "integer",
"name": "threadId",
"meta": {
"added": [
"v10.5.0"
],
"changes": []
},
"desc": "An integer identifier for the current thread. On the corresponding worker object\n(if there is any), it is available as worker.threadId
.\nThis value is unique for each Worker
instance inside a single process.
An arbitrary JavaScript value that contains a clone of the data passed\nto this thread's Worker
constructor.
The data is cloned as if using postMessage()
,\naccording to the HTML structured clone algorithm.
const { Worker, isMainThread, workerData } = require('node:worker_threads');\n\nif (isMainThread) {\n const worker = new Worker(__filename, { workerData: 'Hello, world!' });\n} else {\n console.log(workerData); // Prints 'Hello, world!'.\n}\n
"
}
],
"classes": [
{
"textRaw": "Class: `BroadcastChannel extends EventTarget`",
"type": "class",
"name": "BroadcastChannel",
"meta": {
"added": [
"v15.4.0"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41271",
"description": "No longer experimental."
}
]
},
"desc": "Instances of BroadcastChannel
allow asynchronous one-to-many communication\nwith all other BroadcastChannel
instances bound to the same channel name.
'use strict';\n\nconst {\n isMainThread,\n BroadcastChannel,\n Worker,\n} = require('node:worker_threads');\n\nconst bc = new BroadcastChannel('hello');\n\nif (isMainThread) {\n let c = 0;\n bc.onmessage = (event) => {\n console.log(event.data);\n if (++c === 10) bc.close();\n };\n for (let n = 0; n < 10; n++)\n new Worker(__filename);\n} else {\n bc.postMessage('hello from every worker');\n bc.close();\n}\n
",
"methods": [
{
"textRaw": "`broadcastChannel.close()`",
"type": "method",
"name": "close",
"meta": {
"added": [
"v15.4.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Closes the BroadcastChannel
connection.
Opposite of unref()
. Calling ref()
on a previously unref()
ed\nBroadcastChannel does not let the program exit if it's the only active handle\nleft (the default behavior). If the port is ref()
ed, calling ref()
again\nhas no effect.
Calling unref()
on a BroadcastChannel allows the thread to exit if this\nis the only active handle in the event system. If the BroadcastChannel is\nalready unref()
ed calling unref()
again has no effect.
Instances of the worker.MessageChannel
class represent an asynchronous,\ntwo-way communications channel.\nThe MessageChannel
has no methods of its own. new MessageChannel()
\nyields an object with port1
and port2
properties, which refer to linked\nMessagePort
instances.
const { MessageChannel } = require('node:worker_threads');\n\nconst { port1, port2 } = new MessageChannel();\nport1.on('message', (message) => console.log('received', message));\nport2.postMessage({ foo: 'bar' });\n// Prints: received { foo: 'bar' } from the `port1.on('message')` listener\n
"
},
{
"textRaw": "Class: `MessagePort`",
"type": "class",
"name": "MessagePort",
"meta": {
"added": [
"v10.5.0"
],
"changes": [
{
"version": [
"v14.7.0"
],
"pr-url": "https://github.com/nodejs/node/pull/34057",
"description": "This class now inherits from `EventTarget` rather than from `EventEmitter`."
}
]
},
"desc": "Instances of the worker.MessagePort
class represent one end of an\nasynchronous, two-way communications channel. It can be used to transfer\nstructured data, memory regions and other MessagePort
s between different\nWorker
s.
This implementation matches browser MessagePort
s.
The 'close'
event is emitted once either side of the channel has been\ndisconnected.
const { MessageChannel } = require('node:worker_threads');\nconst { port1, port2 } = new MessageChannel();\n\n// Prints:\n// foobar\n// closed!\nport2.on('message', (message) => console.log(message));\nport2.on('close', () => console.log('closed!'));\n\nport1.postMessage('foobar');\nport1.close();\n
"
},
{
"textRaw": "Event: `'message'`",
"type": "event",
"name": "message",
"meta": {
"added": [
"v10.5.0"
],
"changes": []
},
"params": [
{
"textRaw": "`value` {any} The transmitted value",
"name": "value",
"type": "any",
"desc": "The transmitted value"
}
],
"desc": "The 'message'
event is emitted for any incoming message, containing the cloned\ninput of port.postMessage()
.
Listeners on this event receive a clone of the value
parameter as passed\nto postMessage()
and no further arguments.
The 'messageerror'
event is emitted when deserializing a message failed.
Currently, this event is emitted when there is an error occurring while\ninstantiating the posted JS object on the receiving end. Such situations\nare rare, but can happen, for instance, when certain Node.js API objects\nare received in a vm.Context
(where Node.js APIs are currently\nunavailable).
Disables further sending of messages on either side of the connection.\nThis method can be called when no further communication will happen over this\nMessagePort
.
The 'close'
event is emitted on both MessagePort
instances that\nare part of the channel.
Sends a JavaScript value to the receiving side of this channel.\nvalue
is transferred in a way which is compatible with\nthe HTML structured clone algorithm.
In particular, the significant differences to JSON
are:
value
may contain circular references.value
may contain instances of builtin JS types such as RegExp
s,\nBigInt
s, Map
s, Set
s, etc.value
may contain typed arrays, both using ArrayBuffer
s\nand SharedArrayBuffer
s.value
may contain WebAssembly.Module
instances.value
may not contain native (C++-backed) objects other than:\nconst { MessageChannel } = require('node:worker_threads');\nconst { port1, port2 } = new MessageChannel();\n\nport1.on('message', (message) => console.log(message));\n\nconst circularData = {};\ncircularData.foo = circularData;\n// Prints: { foo: [Circular] }\nport2.postMessage(circularData);\n
\ntransferList
may be a list of ArrayBuffer
, MessagePort
, and\nFileHandle
objects.\nAfter transferring, they are not usable on the sending side of the channel\nanymore (even if they are not contained in value
). Unlike with\nchild processes, transferring handles such as network sockets is currently\nnot supported.
If value
contains SharedArrayBuffer
instances, those are accessible\nfrom either thread. They cannot be listed in transferList
.
value
may still contain ArrayBuffer
instances that are not in\ntransferList
; in that case, the underlying memory is copied rather than moved.
const { MessageChannel } = require('node:worker_threads');\nconst { port1, port2 } = new MessageChannel();\n\nport1.on('message', (message) => console.log(message));\n\nconst uint8Array = new Uint8Array([ 1, 2, 3, 4 ]);\n// This posts a copy of `uint8Array`:\nport2.postMessage(uint8Array);\n// This does not copy data, but renders `uint8Array` unusable:\nport2.postMessage(uint8Array, [ uint8Array.buffer ]);\n\n// The memory for the `sharedUint8Array` is accessible from both the\n// original and the copy received by `.on('message')`:\nconst sharedUint8Array = new Uint8Array(new SharedArrayBuffer(4));\nport2.postMessage(sharedUint8Array);\n\n// This transfers a freshly created message port to the receiver.\n// This can be used, for example, to create communication channels between\n// multiple `Worker` threads that are children of the same parent thread.\nconst otherChannel = new MessageChannel();\nport2.postMessage({ port: otherChannel.port1 }, [ otherChannel.port1 ]);\n
\nThe message object is cloned immediately, and can be modified after\nposting without having side effects.
\nFor more information on the serialization and deserialization mechanisms\nbehind this API, see the serialization API of the node:v8
module.
All TypedArray
and Buffer
instances are views over an underlying\nArrayBuffer
. That is, it is the ArrayBuffer
that actually stores\nthe raw data while the TypedArray
and Buffer
objects provide a\nway of viewing and manipulating the data. It is possible and common\nfor multiple views to be created over the same ArrayBuffer
instance.\nGreat care must be taken when using a transfer list to transfer an\nArrayBuffer
as doing so causes all TypedArray
and Buffer
\ninstances that share that same ArrayBuffer
to become unusable.
const ab = new ArrayBuffer(10);\n\nconst u1 = new Uint8Array(ab);\nconst u2 = new Uint16Array(ab);\n\nconsole.log(u2.length); // prints 5\n\nport.postMessage(u1, [u1.buffer]);\n\nconsole.log(u2.length); // prints 0\n
\nFor Buffer
instances, specifically, whether the underlying\nArrayBuffer
can be transferred or cloned depends entirely on how\ninstances were created, which often cannot be reliably determined.
An ArrayBuffer
can be marked with markAsUntransferable()
to indicate\nthat it should always be cloned and never transferred.
Depending on how a Buffer
instance was created, it may or may\nnot own its underlying ArrayBuffer
. An ArrayBuffer
must not\nbe transferred unless it is known that the Buffer
instance\nowns it. In particular, for Buffer
s created from the internal\nBuffer
pool (using, for instance Buffer.from()
or Buffer.allocUnsafe()
),\ntransferring them is not possible and they are always cloned,\nwhich sends a copy of the entire Buffer
pool.\nThis behavior may come with unintended higher memory\nusage and possible security concerns.
See Buffer.allocUnsafe()
for more details on Buffer
pooling.
The ArrayBuffer
s for Buffer
instances created using\nBuffer.alloc()
or Buffer.allocUnsafeSlow()
can always be\ntransferred but doing so renders all other existing views of\nthose ArrayBuffer
s unusable.
Because object cloning uses the HTML structured clone algorithm,\nnon-enumerable properties, property accessors, and object prototypes are\nnot preserved. In particular, Buffer
objects will be read as\nplain Uint8Array
s on the receiving side, and instances of JavaScript\nclasses will be cloned as plain JavaScript objects.
const b = Symbol('b');\n\nclass Foo {\n #a = 1;\n constructor() {\n this[b] = 2;\n this.c = 3;\n }\n\n get d() { return 4; }\n}\n\nconst { port1, port2 } = new MessageChannel();\n\nport1.onmessage = ({ data }) => console.log(data);\n\nport2.postMessage(new Foo());\n\n// Prints: { c: 3 }\n
\nThis limitation extends to many built-in objects, such as the global URL
\nobject:
const { port1, port2 } = new MessageChannel();\n\nport1.onmessage = ({ data }) => console.log(data);\n\nport2.postMessage(new URL('https://example.org'));\n\n// Prints: { }\n
",
"type": "module",
"displayName": "Considerations when cloning objects with prototypes, classes, and accessors"
}
]
},
{
"textRaw": "`port.hasRef()`",
"type": "method",
"name": "hasRef",
"meta": {
"added": [
"v18.1.0",
"v16.17.0"
],
"changes": []
},
"stability": 1,
"stabilityText": "Experimental",
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": []
}
],
"desc": "If true, the MessagePort
object will keep the Node.js event loop active.
Opposite of unref()
. Calling ref()
on a previously unref()
ed port does\nnot let the program exit if it's the only active handle left (the default\nbehavior). If the port is ref()
ed, calling ref()
again has no effect.
If listeners are attached or removed using .on('message')
, the port\nis ref()
ed and unref()
ed automatically depending on whether\nlisteners for the event exist.
Starts receiving messages on this MessagePort
. When using this port\nas an event emitter, this is called automatically once 'message'
\nlisteners are attached.
This method exists for parity with the Web MessagePort
API. In Node.js,\nit is only useful for ignoring messages when no event listener is present.\nNode.js also diverges in its handling of .onmessage
. Setting it\nautomatically calls .start()
, but unsetting it lets messages queue up\nuntil a new handler is set or the port is discarded.
Calling unref()
on a port allows the thread to exit if this is the only\nactive handle in the event system. If the port is already unref()
ed calling\nunref()
again has no effect.
If listeners are attached or removed using .on('message')
, the port is\nref()
ed and unref()
ed automatically depending on whether\nlisteners for the event exist.
The Worker
class represents an independent JavaScript execution thread.\nMost Node.js APIs are available inside of it.
Notable differences inside a Worker environment are:
\nprocess.stdin
, process.stdout
, and process.stderr
\nstreams may be redirected by the parent thread.require('node:worker_threads').isMainThread
property is set to false
.require('node:worker_threads').parentPort
message port is available.process.exit()
does not stop the whole program, just the single thread,\nand process.abort()
is not available.process.chdir()
and process
methods that set group or user ids\nare not available.process.env
is a copy of the parent thread's environment variables,\nunless otherwise specified. Changes to one copy are not visible in other\nthreads, and are not visible to native add-ons (unless\nworker.SHARE_ENV
is passed as the env
option to the\nWorker
constructor). On Windows, unlike the main thread, a copy of the\nenvironment variables operates in a case-sensitive manner.process.title
cannot be modified.process.on('...')
.worker.terminate()
\nbeing invoked.trace_events
module is not supported.Creating Worker
instances inside of other Worker
s is possible.
Like Web Workers and the node:cluster
module, two-way communication\ncan be achieved through inter-thread message passing. Internally, a Worker
has\na built-in pair of MessagePort
s that are already associated with each\nother when the Worker
is created. While the MessagePort
object on the parent\nside is not directly exposed, its functionalities are exposed through\nworker.postMessage()
and the worker.on('message')
event\non the Worker
object for the parent thread.
To create custom messaging channels (which is encouraged over using the default\nglobal channel because it facilitates separation of concerns), users can create\na MessageChannel
object on either thread and pass one of the\nMessagePort
s on that MessageChannel
to the other thread through a\npre-existing channel, such as the global one.
See port.postMessage()
for more information on how messages are passed,\nand what kind of JavaScript values can be successfully transported through\nthe thread barrier.
const assert = require('node:assert');\nconst {\n Worker, MessageChannel, MessagePort, isMainThread, parentPort,\n} = require('node:worker_threads');\nif (isMainThread) {\n const worker = new Worker(__filename);\n const subChannel = new MessageChannel();\n worker.postMessage({ hereIsYourPort: subChannel.port1 }, [subChannel.port1]);\n subChannel.port2.on('message', (value) => {\n console.log('received:', value);\n });\n} else {\n parentPort.once('message', (value) => {\n assert(value.hereIsYourPort instanceof MessagePort);\n value.hereIsYourPort.postMessage('the worker is sending this');\n value.hereIsYourPort.close();\n });\n}\n
",
"events": [
{
"textRaw": "Event: `'error'`",
"type": "event",
"name": "error",
"meta": {
"added": [
"v10.5.0"
],
"changes": []
},
"params": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
}
],
"desc": "The 'error'
event is emitted if the worker thread throws an uncaught\nexception. In that case, the worker is terminated.
The 'exit'
event is emitted once the worker has stopped. If the worker\nexited by calling process.exit()
, the exitCode
parameter is the\npassed exit code. If the worker was terminated, the exitCode
parameter is\n1
.
This is the final event emitted by any Worker
instance.
The 'message'
event is emitted when the worker thread has invoked\nrequire('node:worker_threads').parentPort.postMessage()
.\nSee the port.on('message')
event for more details.
All messages sent from the worker thread are emitted before the\n'exit'
event is emitted on the Worker
object.
The 'messageerror'
event is emitted when deserializing a message failed.
The 'online'
event is emitted when the worker thread has started executing\nJavaScript code.
Returns a readable stream for a V8 snapshot of the current state of the Worker.\nSee v8.getHeapSnapshot()
for more details.
If the Worker thread is no longer running, which may occur before the\n'exit'
event is emitted, the returned Promise
is rejected\nimmediately with an ERR_WORKER_NOT_RUNNING
error.
Send a message to the worker that is received via\nrequire('node:worker_threads').parentPort.on('message')
.\nSee port.postMessage()
for more details.
Opposite of unref()
, calling ref()
on a previously unref()
ed worker does\nnot let the program exit if it's the only active handle left (the default\nbehavior). If the worker is ref()
ed, calling ref()
again has\nno effect.
Stop all JavaScript execution in the worker thread as soon as possible.\nReturns a Promise for the exit code that is fulfilled when the\n'exit'
event is emitted.
Calling unref()
on a worker allows the thread to exit if this is the only\nactive handle in the event system. If the worker is already unref()
ed calling\nunref()
again has no effect.
An object that can be used to query performance information from a worker\ninstance. Similar to perf_hooks.performance
.
The same call as perf_hooks
eventLoopUtilization()
, except the values\nof the worker instance are returned.
One difference is that, unlike the main thread, bootstrapping within a worker\nis done within the event loop. So the event loop utilization is\nimmediately available once the worker's script begins execution.
\nAn idle
time that does not increase does not indicate that the worker is\nstuck in bootstrap. The following examples shows how the worker's entire\nlifetime never accumulates any idle
time, but is still be able to process\nmessages.
const { Worker, isMainThread, parentPort } = require('node:worker_threads');\n\nif (isMainThread) {\n const worker = new Worker(__filename);\n setInterval(() => {\n worker.postMessage('hi');\n console.log(worker.performance.eventLoopUtilization());\n }, 100).unref();\n return;\n}\n\nparentPort.on('message', () => console.log('msg')).unref();\n(function r(n) {\n if (--n < 0) return;\n const t = Date.now();\n while (Date.now() - t < 300);\n setImmediate(r, n);\n})(10);\n
\nThe event loop utilization of a worker is available only after the 'online'
\nevent emitted, and if called before this, or after the 'exit'
\nevent, then all properties have the value of 0
.
Provides the set of JS engine resource constraints for this Worker thread.\nIf the resourceLimits
option was passed to the Worker
constructor,\nthis matches its values.
If the worker has stopped, the return value is an empty object.
" }, { "textRaw": "`stderr` {stream.Readable}", "type": "stream.Readable", "name": "stderr", "meta": { "added": [ "v10.5.0" ], "changes": [] }, "desc": "This is a readable stream which contains data written to process.stderr
\ninside the worker thread. If stderr: true
was not passed to the\nWorker
constructor, then data is piped to the parent thread's\nprocess.stderr
stream.
If stdin: true
was passed to the Worker
constructor, this is a\nwritable stream. The data written to this stream will be made available in\nthe worker thread as process.stdin
.
This is a readable stream which contains data written to process.stdout
\ninside the worker thread. If stdout: true
was not passed to the\nWorker
constructor, then data is piped to the parent thread's\nprocess.stdout
stream.
An integer identifier for the referenced thread. Inside the worker thread,\nit is available as require('node:worker_threads').threadId
.\nThis value is unique for each Worker
instance inside a single process.
Worker
s utilize message passing via <MessagePort> to implement interactions\nwith stdio
. This means that stdio
output originating from a Worker
can\nget blocked by synchronous code on the receiving end that is blocking the\nNode.js event loop.
import {\n Worker,\n isMainThread,\n} from 'worker_threads';\n\nif (isMainThread) {\n new Worker(new URL(import.meta.url));\n for (let n = 0; n < 1e10; n++) {\n // Looping to simulate work.\n }\n} else {\n // This output will be blocked by the for loop in the main thread.\n console.log('foo');\n}\n
\n'use strict';\n\nconst {\n Worker,\n isMainThread,\n} = require('node:worker_threads');\n\nif (isMainThread) {\n new Worker(__filename);\n for (let n = 0; n < 1e10; n++) {\n // Looping to simulate work.\n }\n} else {\n // This output will be blocked by the for loop in the main thread.\n console.log('foo');\n}\n
",
"type": "module",
"displayName": "Synchronous blocking of stdio"
},
{
"textRaw": "Launching worker threads from preload scripts",
"name": "launching_worker_threads_from_preload_scripts",
"desc": "Take care when launching worker threads from preload scripts (scripts loaded\nand run using the -r
command line flag). Unless the execArgv
option is\nexplicitly set, new Worker threads automatically inherit the command line flags\nfrom the running process and will preload the same preload scripts as the main\nthread. If the preload script unconditionally launches a worker thread, every\nthread spawned will spawn another until the application crashes.
Source Code: lib/zlib.js
\nThe node:zlib
module provides compression functionality implemented using\nGzip, Deflate/Inflate, and Brotli.
To access it:
\nconst zlib = require('node:zlib');\n
\nCompression and decompression are built around the Node.js Streams API.
\nCompressing or decompressing a stream (such as a file) can be accomplished by\npiping the source stream through a zlib
Transform
stream into a destination\nstream:
const { createGzip } = require('node:zlib');\nconst { pipeline } = require('node:stream');\nconst {\n createReadStream,\n createWriteStream,\n} = require('node:fs');\n\nconst gzip = createGzip();\nconst source = createReadStream('input.txt');\nconst destination = createWriteStream('input.txt.gz');\n\npipeline(source, gzip, destination, (err) => {\n if (err) {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n }\n});\n\n// Or, Promisified\n\nconst { promisify } = require('node:util');\nconst pipe = promisify(pipeline);\n\nasync function do_gzip(input, output) {\n const gzip = createGzip();\n const source = createReadStream(input);\n const destination = createWriteStream(output);\n await pipe(source, gzip, destination);\n}\n\ndo_gzip('input.txt', 'input.txt.gz')\n .catch((err) => {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n });\n
\nIt is also possible to compress or decompress data in a single step:
\nconst { deflate, unzip } = require('node:zlib');\n\nconst input = '.................................';\ndeflate(input, (err, buffer) => {\n if (err) {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n }\n console.log(buffer.toString('base64'));\n});\n\nconst buffer = Buffer.from('eJzT0yMAAGTvBe8=', 'base64');\nunzip(buffer, (err, buffer) => {\n if (err) {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n }\n console.log(buffer.toString());\n});\n\n// Or, Promisified\n\nconst { promisify } = require('node:util');\nconst do_unzip = promisify(unzip);\n\ndo_unzip(buffer)\n .then((buf) => console.log(buf.toString()))\n .catch((err) => {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n });\n
",
"modules": [
{
"textRaw": "Threadpool usage and performance considerations",
"name": "threadpool_usage_and_performance_considerations",
"desc": "All zlib
APIs, except those that are explicitly synchronous, use the Node.js\ninternal threadpool. This can lead to surprising effects and performance\nlimitations in some applications.
Creating and using a large number of zlib objects simultaneously can cause\nsignificant memory fragmentation.
\nconst zlib = require('node:zlib');\n\nconst payload = Buffer.from('This is some data');\n\n// WARNING: DO NOT DO THIS!\nfor (let i = 0; i < 30000; ++i) {\n zlib.deflate(payload, (err, buffer) => {});\n}\n
\nIn the preceding example, 30,000 deflate instances are created concurrently.\nBecause of how some operating systems handle memory allocation and\ndeallocation, this may lead to significant memory fragmentation.
\nIt is strongly recommended that the results of compression\noperations be cached to avoid duplication of effort.
", "type": "module", "displayName": "Threadpool usage and performance considerations" }, { "textRaw": "Compressing HTTP requests and responses", "name": "compressing_http_requests_and_responses", "desc": "The node:zlib
module can be used to implement support for the gzip
, deflate
\nand br
content-encoding mechanisms defined by\nHTTP.
The HTTP Accept-Encoding
header is used within an HTTP request to identify\nthe compression encodings accepted by the client. The Content-Encoding
\nheader is used to identify the compression encodings actually applied to a\nmessage.
The examples given below are drastically simplified to show the basic concept.\nUsing zlib
encoding can be expensive, and the results ought to be cached.\nSee Memory usage tuning for more information on the speed/memory/compression\ntradeoffs involved in zlib
usage.
// Client request example\nconst zlib = require('node:zlib');\nconst http = require('node:http');\nconst fs = require('node:fs');\nconst { pipeline } = require('node:stream');\n\nconst request = http.get({ host: 'example.com',\n path: '/',\n port: 80,\n headers: { 'Accept-Encoding': 'br,gzip,deflate' } });\nrequest.on('response', (response) => {\n const output = fs.createWriteStream('example.com_index.html');\n\n const onError = (err) => {\n if (err) {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n }\n };\n\n switch (response.headers['content-encoding']) {\n case 'br':\n pipeline(response, zlib.createBrotliDecompress(), output, onError);\n break;\n // Or, just use zlib.createUnzip() to handle both of the following cases:\n case 'gzip':\n pipeline(response, zlib.createGunzip(), output, onError);\n break;\n case 'deflate':\n pipeline(response, zlib.createInflate(), output, onError);\n break;\n default:\n pipeline(response, output, onError);\n break;\n }\n});\n
\n// server example\n// Running a gzip operation on every request is quite expensive.\n// It would be much more efficient to cache the compressed buffer.\nconst zlib = require('node:zlib');\nconst http = require('node:http');\nconst fs = require('node:fs');\nconst { pipeline } = require('node:stream');\n\nhttp.createServer((request, response) => {\n const raw = fs.createReadStream('index.html');\n // Store both a compressed and an uncompressed version of the resource.\n response.setHeader('Vary', 'Accept-Encoding');\n let acceptEncoding = request.headers['accept-encoding'];\n if (!acceptEncoding) {\n acceptEncoding = '';\n }\n\n const onError = (err) => {\n if (err) {\n // If an error occurs, there's not much we can do because\n // the server has already sent the 200 response code and\n // some amount of data has already been sent to the client.\n // The best we can do is terminate the response immediately\n // and log the error.\n response.end();\n console.error('An error occurred:', err);\n }\n };\n\n // Note: This is not a conformant accept-encoding parser.\n // See https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3\n if (/\\bdeflate\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'deflate' });\n pipeline(raw, zlib.createDeflate(), response, onError);\n } else if (/\\bgzip\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'gzip' });\n pipeline(raw, zlib.createGzip(), response, onError);\n } else if (/\\bbr\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'br' });\n pipeline(raw, zlib.createBrotliCompress(), response, onError);\n } else {\n response.writeHead(200, {});\n pipeline(raw, response, onError);\n }\n}).listen(1337);\n
\nBy default, the zlib
methods will throw an error when decompressing\ntruncated data. However, if it is known that the data is incomplete, or\nthe desire is to inspect only the beginning of a compressed file, it is\npossible to suppress the default error handling by changing the flushing\nmethod that is used to decompress the last chunk of input data:
// This is a truncated version of the buffer from the above examples\nconst buffer = Buffer.from('eJzT0yMA', 'base64');\n\nzlib.unzip(\n buffer,\n // For Brotli, the equivalent is zlib.constants.BROTLI_OPERATION_FLUSH.\n { finishFlush: zlib.constants.Z_SYNC_FLUSH },\n (err, buffer) => {\n if (err) {\n console.error('An error occurred:', err);\n process.exitCode = 1;\n }\n console.log(buffer.toString());\n });\n
\nThis will not change the behavior in other error-throwing situations, e.g.\nwhen the input data has an invalid format. Using this method, it will not be\npossible to determine whether the input ended prematurely or lacks the\nintegrity checks, making it necessary to manually check that the\ndecompressed result is valid.
", "type": "module", "displayName": "Compressing HTTP requests and responses" }, { "textRaw": "Flushing", "name": "flushing", "desc": "Calling .flush()
on a compression stream will make zlib
return as much\noutput as currently possible. This may come at the cost of degraded compression\nquality, but can be useful when data needs to be available as soon as possible.
In the following example, flush()
is used to write a compressed partial\nHTTP response to the client:
const zlib = require('node:zlib');\nconst http = require('node:http');\nconst { pipeline } = require('node:stream');\n\nhttp.createServer((request, response) => {\n // For the sake of simplicity, the Accept-Encoding checks are omitted.\n response.writeHead(200, { 'content-encoding': 'gzip' });\n const output = zlib.createGzip();\n let i;\n\n pipeline(output, response, (err) => {\n if (err) {\n // If an error occurs, there's not much we can do because\n // the server has already sent the 200 response code and\n // some amount of data has already been sent to the client.\n // The best we can do is terminate the response immediately\n // and log the error.\n clearInterval(i);\n response.end();\n console.error('An error occurred:', err);\n }\n });\n\n i = setInterval(() => {\n output.write(`The current time is ${Date()}\\n`, () => {\n // The data has been passed to zlib, but the compression algorithm may\n // have decided to buffer the data for more efficient compression.\n // Calling .flush() will make the data available as soon as the client\n // is ready to receive it.\n output.flush();\n });\n }, 1000);\n}).listen(1337);\n
",
"type": "module",
"displayName": "Flushing"
}
],
"miscs": [
{
"textRaw": "Memory usage tuning",
"name": "Memory usage tuning",
"type": "misc",
"miscs": [
{
"textRaw": "For zlib-based streams",
"name": "for_zlib-based_streams",
"desc": "From zlib/zconf.h
, modified for Node.js usage:
The memory requirements for deflate are (in bytes):
\n\n(1 << (windowBits + 2)) + (1 << (memLevel + 9))\n
\nThat is: 128K for windowBits
= 15 + 128K for memLevel
= 8\n(default values) plus a few kilobytes for small objects.
For example, to reduce the default memory requirements from 256K to 128K, the\noptions should be set to:
\nconst options = { windowBits: 14, memLevel: 7 };\n
\nThis will, however, generally degrade compression.
\nThe memory requirements for inflate are (in bytes) 1 << windowBits
.\nThat is, 32K for windowBits
= 15 (default value) plus a few kilobytes\nfor small objects.
This is in addition to a single internal output slab buffer of size\nchunkSize
, which defaults to 16K.
The speed of zlib
compression is affected most dramatically by the\nlevel
setting. A higher level will result in better compression, but\nwill take longer to complete. A lower level will result in less\ncompression, but will be much faster.
In general, greater memory usage options will mean that Node.js has to make\nfewer calls to zlib
because it will be able to process more data on\neach write
operation. So, this is another factor that affects the\nspeed, at the cost of memory usage.
There are equivalents to the zlib options for Brotli-based streams, although\nthese options have different ranges than the zlib ones:
\nlevel
option matches Brotli's BROTLI_PARAM_QUALITY
option.windowBits
option matches Brotli's BROTLI_PARAM_LGWIN
option.See below for more details on Brotli-specific options.
", "type": "misc", "displayName": "For Brotli-based streams" } ] }, { "textRaw": "Constants", "name": "Constants", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "type": "misc", "miscs": [ { "textRaw": "zlib constants", "name": "zlib_constants", "desc": "All of the constants defined in zlib.h
are also defined on\nrequire('node:zlib').constants
. In the normal course of operations, it will\nnot be necessary to use these constants. They are documented so that their\npresence is not surprising. This section is taken almost directly from the\nzlib documentation.
Previously, the constants were available directly from require('node:zlib')
,\nfor instance zlib.Z_NO_FLUSH
. Accessing the constants directly from the module\nis currently still possible but is deprecated.
Allowed flush values.
\nzlib.constants.Z_NO_FLUSH
zlib.constants.Z_PARTIAL_FLUSH
zlib.constants.Z_SYNC_FLUSH
zlib.constants.Z_FULL_FLUSH
zlib.constants.Z_FINISH
zlib.constants.Z_BLOCK
zlib.constants.Z_TREES
Return codes for the compression/decompression functions. Negative\nvalues are errors, positive values are used for special but normal\nevents.
\nzlib.constants.Z_OK
zlib.constants.Z_STREAM_END
zlib.constants.Z_NEED_DICT
zlib.constants.Z_ERRNO
zlib.constants.Z_STREAM_ERROR
zlib.constants.Z_DATA_ERROR
zlib.constants.Z_MEM_ERROR
zlib.constants.Z_BUF_ERROR
zlib.constants.Z_VERSION_ERROR
Compression levels.
\nzlib.constants.Z_NO_COMPRESSION
zlib.constants.Z_BEST_SPEED
zlib.constants.Z_BEST_COMPRESSION
zlib.constants.Z_DEFAULT_COMPRESSION
Compression strategy.
\nzlib.constants.Z_FILTERED
zlib.constants.Z_HUFFMAN_ONLY
zlib.constants.Z_RLE
zlib.constants.Z_FIXED
zlib.constants.Z_DEFAULT_STRATEGY
There are several options and other constants available for Brotli-based\nstreams:
", "modules": [ { "textRaw": "Flush operations", "name": "flush_operations", "desc": "The following values are valid flush operations for Brotli-based streams:
\nzlib.constants.BROTLI_OPERATION_PROCESS
(default for all operations)zlib.constants.BROTLI_OPERATION_FLUSH
(default when calling .flush()
)zlib.constants.BROTLI_OPERATION_FINISH
(default for the last chunk)zlib.constants.BROTLI_OPERATION_EMIT_METADATA
\nThere are several options that can be set on Brotli encoders, affecting\ncompression efficiency and speed. Both the keys and the values can be accessed\nas properties of the zlib.constants
object.
The most important options are:
\nBROTLI_PARAM_MODE
\nBROTLI_MODE_GENERIC
(default)BROTLI_MODE_TEXT
, adjusted for UTF-8 textBROTLI_MODE_FONT
, adjusted for WOFF 2.0 fontsBROTLI_PARAM_QUALITY
\nBROTLI_MIN_QUALITY
to BROTLI_MAX_QUALITY
,\nwith a default of BROTLI_DEFAULT_QUALITY
.BROTLI_PARAM_SIZE_HINT
\n0
for an unknown input size.The following flags can be set for advanced control over the compression\nalgorithm and memory usage tuning:
\nBROTLI_PARAM_LGWIN
\nBROTLI_MIN_WINDOW_BITS
to BROTLI_MAX_WINDOW_BITS
,\nwith a default of BROTLI_DEFAULT_WINDOW
, or up to\nBROTLI_LARGE_MAX_WINDOW_BITS
if the BROTLI_PARAM_LARGE_WINDOW
flag\nis set.BROTLI_PARAM_LGBLOCK
\nBROTLI_MIN_INPUT_BLOCK_BITS
to BROTLI_MAX_INPUT_BLOCK_BITS
.BROTLI_PARAM_DISABLE_LITERAL_CONTEXT_MODELING
\nBROTLI_PARAM_LARGE_WINDOW
\nBROTLI_PARAM_NPOSTFIX
\n0
to BROTLI_MAX_NPOSTFIX
.BROTLI_PARAM_NDIRECT
\n0
to 15 << NPOSTFIX
in steps of 1 << NPOSTFIX
.These advanced options are available for controlling decompression:
\nBROTLI_DECODER_PARAM_DISABLE_RING_BUFFER_REALLOCATION
\nBROTLI_DECODER_PARAM_LARGE_WINDOW
\nEach zlib-based class takes an options
object. No options are required.
Some options are only relevant when compressing and are\nignored by the decompression classes.
\nflush
<integer> Default: zlib.constants.Z_NO_FLUSH
finishFlush
<integer> Default: zlib.constants.Z_FINISH
chunkSize
<integer> Default: 16 * 1024
windowBits
<integer>level
<integer> (compression only)memLevel
<integer> (compression only)strategy
<integer> (compression only)dictionary
<Buffer> | <TypedArray> | <DataView> | <ArrayBuffer> (deflate/inflate only,\nempty dictionary by default)info
<boolean> (If true
, returns an object with buffer
and engine
.)maxOutputLength
<integer> Limits output size when using\nconvenience methods. Default: buffer.kMaxLength
See the deflateInit2
and inflateInit2
documentation for more\ninformation.
Each Brotli-based class takes an options
object. All options are optional.
flush
<integer> Default: zlib.constants.BROTLI_OPERATION_PROCESS
finishFlush
<integer> Default: zlib.constants.BROTLI_OPERATION_FINISH
chunkSize
<integer> Default: 16 * 1024
params
<Object> Key-value object containing indexed Brotli parameters.maxOutputLength
<integer> Limits output size when using\nconvenience methods. Default: buffer.kMaxLength
For example:
\nconst stream = zlib.createBrotliCompress({\n chunkSize: 32 * 1024,\n params: {\n [zlib.constants.BROTLI_PARAM_MODE]: zlib.constants.BROTLI_MODE_TEXT,\n [zlib.constants.BROTLI_PARAM_QUALITY]: 4,\n [zlib.constants.BROTLI_PARAM_SIZE_HINT]: fs.statSync(inputFile).size,\n },\n});\n
"
},
{
"textRaw": "Convenience methods",
"name": "Convenience methods",
"type": "misc",
"desc": "All of these take a Buffer
, TypedArray
, DataView
,\nArrayBuffer
or string as the first argument, an optional second argument\nto supply options to the zlib
classes and will call the supplied callback\nwith callback(error, result)
.
Every method has a *Sync
counterpart, which accept the same arguments, but\nwithout a callback.
Compress a chunk of data with BrotliCompress
.
Decompress a chunk of data with BrotliDecompress
.
Compress a chunk of data with Deflate
.
Compress a chunk of data with DeflateRaw
.
Decompress a chunk of data with Gunzip
.
Compress a chunk of data with Gzip
.
Decompress a chunk of data with Inflate
.
Decompress a chunk of data with InflateRaw
.
Decompress a chunk of data with Unzip
.
Compress data using the Brotli algorithm.
" }, { "textRaw": "Class: `zlib.BrotliDecompress`", "type": "class", "name": "zlib.BrotliDecompress", "meta": { "added": [ "v11.7.0", "v10.16.0" ], "changes": [] }, "desc": "Decompress data using the Brotli algorithm.
" }, { "textRaw": "Class: `zlib.Deflate`", "type": "class", "name": "zlib.Deflate", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Compress data using deflate.
" }, { "textRaw": "Class: `zlib.DeflateRaw`", "type": "class", "name": "zlib.DeflateRaw", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Compress data using deflate, and do not append a zlib
header.
Decompress a gzip stream.
" }, { "textRaw": "Class: `zlib.Gzip`", "type": "class", "name": "zlib.Gzip", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Compress data using gzip.
" }, { "textRaw": "Class: `zlib.Inflate`", "type": "class", "name": "zlib.Inflate", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v5.0.0", "pr-url": "https://github.com/nodejs/node/pull/2595", "description": "A truncated input stream will now result in an `'error'` event." } ] }, "desc": "Decompress a deflate stream.
" }, { "textRaw": "Class: `zlib.InflateRaw`", "type": "class", "name": "zlib.InflateRaw", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v6.8.0", "pr-url": "https://github.com/nodejs/node/pull/8512", "description": "Custom dictionaries are now supported by `InflateRaw`." }, { "version": "v5.0.0", "pr-url": "https://github.com/nodejs/node/pull/2595", "description": "A truncated input stream will now result in an `'error'` event." } ] }, "desc": "Decompress a raw deflate stream.
" }, { "textRaw": "Class: `zlib.Unzip`", "type": "class", "name": "zlib.Unzip", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Decompress either a Gzip- or Deflate-compressed stream by auto-detecting\nthe header.
" }, { "textRaw": "Class: `zlib.ZlibBase`", "type": "class", "name": "zlib.ZlibBase", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": [ "v11.7.0", "v10.16.0" ], "pr-url": "https://github.com/nodejs/node/pull/24939", "description": "This class was renamed from `Zlib` to `ZlibBase`." } ] }, "desc": "Not exported by the node:zlib
module. It is documented here because it is the\nbase class of the compressor/decompressor classes.
This class inherits from stream.Transform
, allowing node:zlib
objects to\nbe used in pipes and similar stream operations.
Deprecated alias for zlib.bytesWritten
. This original name was chosen\nbecause it also made sense to interpret the value as the number of bytes\nread by the engine, but is inconsistent with other streams in Node.js that\nexpose values under these names.
The zlib.bytesWritten
property specifies the number of bytes written to\nthe engine, before the bytes are processed (compressed or decompressed,\nas appropriate for the derived class).
Close the underlying handle.
" }, { "textRaw": "`zlib.flush([kind, ]callback)`", "type": "method", "name": "flush", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`kind` **Default:** `zlib.constants.Z_FULL_FLUSH` for zlib-based streams, `zlib.constants.BROTLI_OPERATION_FLUSH` for Brotli-based streams.", "name": "kind", "default": "`zlib.constants.Z_FULL_FLUSH` for zlib-based streams, `zlib.constants.BROTLI_OPERATION_FLUSH` for Brotli-based streams" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function" } ] } ], "desc": "Flush pending data. Don't call this frivolously, premature flushes negatively\nimpact the effectiveness of the compression algorithm.
\nCalling this only flushes data from the internal zlib
state, and does not\nperform flushing of any kind on the streams level. Rather, it behaves like a\nnormal call to .write()
, i.e. it will be queued up behind other pending\nwrites and will only produce output when data is being read from the stream.
This function is only available for zlib-based streams, i.e. not Brotli.
\nDynamically update the compression level and compression strategy.\nOnly applicable to deflate algorithm.
" }, { "textRaw": "`zlib.reset()`", "type": "method", "name": "reset", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Reset the compressor/decompressor to factory defaults. Only applicable to\nthe inflate and deflate algorithms.
" } ] } ], "properties": [ { "textRaw": "`zlib.constants`", "name": "constants", "meta": { "added": [ "v7.0.0" ], "changes": [] }, "desc": "Provides an object enumerating Zlib-related constants.
" } ], "methods": [ { "textRaw": "`zlib.createBrotliCompress([options])`", "type": "method", "name": "createBrotliCompress", "meta": { "added": [ "v11.7.0", "v10.16.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`options` {brotli options}", "name": "options", "type": "brotli options" } ] } ], "desc": "Creates and returns a new BrotliCompress
object.
Creates and returns a new BrotliDecompress
object.
Creates and returns a new Deflate
object.
Creates and returns a new DeflateRaw
object.
An upgrade of zlib from 1.2.8 to 1.2.11 changed behavior when windowBits
\nis set to 8 for raw deflate streams. zlib would automatically set windowBits
\nto 9 if was initially set to 8. Newer versions of zlib will throw an exception,\nso Node.js restored the original behavior of upgrading a value of 8 to 9,\nsince passing windowBits = 9
to zlib actually results in a compressed stream\nthat effectively uses an 8-bit window only.
Creates and returns a new Gunzip
object.
Creates and returns a new Gzip
object.\nSee example.
Creates and returns a new Inflate
object.
Creates and returns a new InflateRaw
object.
Creates and returns a new Unzip
object.
Compress a chunk of data with BrotliCompress
.
Decompress a chunk of data with BrotliDecompress
.
Compress a chunk of data with Deflate
.
Compress a chunk of data with DeflateRaw
.
Decompress a chunk of data with Gunzip
.
Compress a chunk of data with Gzip
.
Decompress a chunk of data with Inflate
.
Decompress a chunk of data with InflateRaw
.
Decompress a chunk of data with Unzip
.
A generic JavaScript <Error> object that does not denote any specific\ncircumstance of why the error occurred. Error
objects capture a \"stack trace\"\ndetailing the point in the code at which the Error
was instantiated, and may\nprovide a text description of the error.
All errors generated by Node.js, including all system and JavaScript errors,\nwill either be instances of, or inherit from, the Error
class.
Creates a .stack
property on targetObject
, which when accessed returns\na string representing the location in the code at which\nError.captureStackTrace()
was called.
const myObject = {};\nError.captureStackTrace(myObject);\nmyObject.stack; // Similar to `new Error().stack`\n
\nThe first line of the trace will be prefixed with\n${myObject.name}: ${myObject.message}
.
The optional constructorOpt
argument accepts a function. If given, all frames\nabove constructorOpt
, including constructorOpt
, will be omitted from the\ngenerated stack trace.
The constructorOpt
argument is useful for hiding implementation\ndetails of error generation from the user. For instance:
function a() {\n b();\n}\n\nfunction b() {\n c();\n}\n\nfunction c() {\n // Create an error without stack trace to avoid calculating the stack trace twice.\n const { stackTraceLimit } = Error;\n Error.stackTraceLimit = 0;\n const error = new Error();\n Error.stackTraceLimit = stackTraceLimit;\n\n // Capture the stack trace above function b\n Error.captureStackTrace(error, b); // Neither function c, nor b is included in the stack trace\n throw error;\n}\n\na();\n
"
}
],
"properties": [
{
"textRaw": "`stackTraceLimit` {number}",
"type": "number",
"name": "stackTraceLimit",
"desc": "The Error.stackTraceLimit
property specifies the number of stack frames\ncollected by a stack trace (whether generated by new Error().stack
or\nError.captureStackTrace(obj)
).
The default value is 10
but may be set to any valid JavaScript number. Changes\nwill affect any stack trace captured after the value has been changed.
If set to a non-number value, or set to a negative number, stack traces will\nnot capture any frames.
" }, { "textRaw": "`cause` {any}", "type": "any", "name": "cause", "meta": { "added": [ "v16.9.0" ], "changes": [] }, "desc": "If present, the error.cause
property is the underlying cause of the Error
.\nIt is used when catching an error and throwing a new one with a different\nmessage or code in order to still have access to the original error.
The error.cause
property is typically set by calling\nnew Error(message, { cause })
. It is not set by the constructor if the\ncause
option is not provided.
This property allows errors to be chained. When serializing Error
objects,\nutil.inspect()
recursively serializes error.cause
if it is set.
const cause = new Error('The remote HTTP server responded with a 500 status');\nconst symptom = new Error('The message failed to send', { cause });\n\nconsole.log(symptom);\n// Prints:\n// Error: The message failed to send\n// at REPL2:1:17\n// at Script.runInThisContext (node:vm:130:12)\n// ... 7 lines matching cause stack trace ...\n// at [_line] [as _line] (node:internal/readline/interface:886:18) {\n// [cause]: Error: The remote HTTP server responded with a 500 status\n// at REPL1:1:15\n// at Script.runInThisContext (node:vm:130:12)\n// at REPLServer.defaultEval (node:repl:574:29)\n// at bound (node:domain:426:15)\n// at REPLServer.runBound [as eval] (node:domain:437:12)\n// at REPLServer.onLine (node:repl:902:10)\n// at REPLServer.emit (node:events:549:35)\n// at REPLServer.emit (node:domain:482:12)\n// at [_onLine] [as _onLine] (node:internal/readline/interface:425:12)\n// at [_line] [as _line] (node:internal/readline/interface:886:18)\n
"
},
{
"textRaw": "`code` {string}",
"type": "string",
"name": "code",
"desc": "The error.code
property is a string label that identifies the kind of error.\nerror.code
is the most stable way to identify an error. It will only change\nbetween major versions of Node.js. In contrast, error.message
strings may\nchange between any versions of Node.js. See Node.js error codes for details\nabout specific codes.
The error.message
property is the string description of the error as set by\ncalling new Error(message)
. The message
passed to the constructor will also\nappear in the first line of the stack trace of the Error
, however changing\nthis property after the Error
object is created may not change the first\nline of the stack trace (for example, when error.stack
is read before this\nproperty is changed).
const err = new Error('The message');\nconsole.error(err.message);\n// Prints: The message\n
"
},
{
"textRaw": "`stack` {string}",
"type": "string",
"name": "stack",
"desc": "The error.stack
property is a string describing the point in the code at which\nthe Error
was instantiated.
Error: Things keep happening!\n at /home/gbusey/file.js:525:2\n at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)\n at Actor.<anonymous> (/home/gbusey/actors.js:400:8)\n at increaseSynergy (/home/gbusey/actors.js:701:6)\n
\nThe first line is formatted as <error class name>: <error message>
, and\nis followed by a series of stack frames (each line beginning with \"at \").\nEach frame describes a call site within the code that lead to the error being\ngenerated. V8 attempts to display a name for each function (by variable name,\nfunction name, or object method name), but occasionally it will not be able to\nfind a suitable name. If V8 cannot determine a name for the function, only\nlocation information will be displayed for that frame. Otherwise, the\ndetermined function name will be displayed with location information appended\nin parentheses.
Frames are only generated for JavaScript functions. If, for example, execution\nsynchronously passes through a C++ addon function called cheetahify
which\nitself calls a JavaScript function, the frame representing the cheetahify
call\nwill not be present in the stack traces:
const cheetahify = require('./native-binding.node');\n\nfunction makeFaster() {\n // `cheetahify()` *synchronously* calls speedy.\n cheetahify(function speedy() {\n throw new Error('oh no!');\n });\n}\n\nmakeFaster();\n// will throw:\n// /home/gbusey/file.js:6\n// throw new Error('oh no!');\n// ^\n// Error: oh no!\n// at speedy (/home/gbusey/file.js:6:11)\n// at makeFaster (/home/gbusey/file.js:5:3)\n// at Object.<anonymous> (/home/gbusey/file.js:10:1)\n// at Module._compile (module.js:456:26)\n// at Object.Module._extensions..js (module.js:474:10)\n// at Module.load (module.js:356:32)\n// at Function.Module._load (module.js:312:12)\n// at Function.Module.runMain (module.js:497:10)\n// at startup (node.js:119:16)\n// at node.js:906:3\n
\nThe location information will be one of:
\nnative
, if the frame represents a call internal to V8 (as in [].forEach
).plain-filename.js:line:column
, if the frame represents a call internal\nto Node.js./absolute/path/to/file.js:line:column
, if the frame represents a call in\na user program (using CommonJS module system), or its dependencies.<transport-protocol>:///url/to/module/file.mjs:line:column
, if the frame\nrepresents a call in a user program (using ES module system), or\nits dependencies.The string representing the stack trace is lazily generated when the\nerror.stack
property is accessed.
The number of frames captured by the stack trace is bounded by the smaller of\nError.stackTraceLimit
or the number of available frames on the current event\nloop tick.
Creates a new Error
object and sets the error.message
property to the\nprovided text message. If an object is passed as message
, the text message\nis generated by calling String(message)
. If the cause
option is provided,\nit is assigned to the error.cause
property. The error.stack
property will\nrepresent the point in the code at which new Error()
was called. Stack traces\nare dependent on V8's stack trace API. Stack traces extend only to either\n(a) the beginning of synchronous code execution, or (b) the number of frames\ngiven by the property Error.stackTraceLimit
, whichever is smaller.
Indicates the failure of an assertion. For details, see\nClass: assert.AssertionError
.
Indicates that a provided argument was not within the set or range of\nacceptable values for a function; whether that is a numeric range, or\noutside the set of options for a given function parameter.
\nrequire('node:net').connect(-1);\n// Throws \"RangeError: \"port\" option should be >= 0 and < 65536: -1\"\n
\nNode.js will generate and throw RangeError
instances immediately as a form\nof argument validation.
Indicates that an attempt is being made to access a variable that is not\ndefined. Such errors commonly indicate typos in code, or an otherwise broken\nprogram.
\nWhile client code may generate and propagate these errors, in practice, only V8\nwill do so.
\ndoesNotExist;\n// Throws ReferenceError, doesNotExist is not a variable in this program.\n
\nUnless an application is dynamically generating and running code,\nReferenceError
instances indicate a bug in the code or its dependencies.
Indicates that a program is not valid JavaScript. These errors may only be\ngenerated and propagated as a result of code evaluation. Code evaluation may\nhappen as a result of eval
, Function
, require
, or vm. These errors\nare almost always indicative of a broken program.
try {\n require('node:vm').runInThisContext('binary ! isNotOk');\n} catch (err) {\n // 'err' will be a SyntaxError.\n}\n
\nSyntaxError
instances are unrecoverable in the context that created them –\nthey may only be caught by other contexts.
Node.js generates system errors when exceptions occur within its runtime\nenvironment. These usually occur when an application violates an operating\nsystem constraint. For example, a system error will occur if an application\nattempts to read a file that does not exist.
\naddress
<string> If present, the address to which a network connection\nfailedcode
<string> The string error codedest
<string> If present, the file path destination when reporting a file\nsystem errorerrno
<number> The system-provided error numberinfo
<Object> If present, extra details about the error conditionmessage
<string> A system-provided human-readable description of the errorpath
<string> If present, the file path when reporting a file system errorport
<number> If present, the network connection port that is not availablesyscall
<string> The name of the system call that triggered the errorIf present, error.address
is a string describing the address to which a\nnetwork connection failed.
The error.code
property is a string representing the error code.
If present, error.dest
is the file path destination when reporting a file\nsystem error.
The error.errno
property is a negative number which corresponds\nto the error code defined in libuv Error handling
.
On Windows the error number provided by the system will be normalized by libuv.
\nTo get the string representation of the error code, use\nutil.getSystemErrorName(error.errno)
.
If present, error.info
is an object with details about the error condition.
error.message
is a system-provided human-readable description of the error.
If present, error.path
is a string containing a relevant invalid pathname.
If present, error.port
is the network connection port that is not available.
The error.syscall
property is a string describing the syscall that failed.
This is a list of system errors commonly-encountered when writing a Node.js\nprogram. For a comprehensive list, see the errno
(3) man page.
EACCES
(Permission denied): An attempt was made to access a file in a way\nforbidden by its file access permissions.
EADDRINUSE
(Address already in use): An attempt to bind a server\n(net
, http
, or https
) to a local address failed due to\nanother server on the local system already occupying that address.
ECONNREFUSED
(Connection refused): No connection could be made because the\ntarget machine actively refused it. This usually results from trying to\nconnect to a service that is inactive on the foreign host.
ECONNRESET
(Connection reset by peer): A connection was forcibly closed by\na peer. This normally results from a loss of the connection on the remote\nsocket due to a timeout or reboot. Commonly encountered via the http
\nand net
modules.
EEXIST
(File exists): An existing file was the target of an operation that\nrequired that the target not exist.
EISDIR
(Is a directory): An operation expected a file, but the given\npathname was a directory.
EMFILE
(Too many open files in system): Maximum number of\nfile descriptors allowable on the system has been reached, and\nrequests for another descriptor cannot be fulfilled until at least one\nhas been closed. This is encountered when opening many files at once in\nparallel, especially on systems (in particular, macOS) where there is a low\nfile descriptor limit for processes. To remedy a low limit, run\nulimit -n 2048
in the same shell that will run the Node.js process.
ENOENT
(No such file or directory): Commonly raised by fs
operations\nto indicate that a component of the specified pathname does not exist. No\nentity (file or directory) could be found by the given path.
ENOTDIR
(Not a directory): A component of the given pathname existed, but\nwas not a directory as expected. Commonly raised by fs.readdir
.
ENOTEMPTY
(Directory not empty): A directory with entries was the target\nof an operation that requires an empty directory, usually fs.unlink
.
ENOTFOUND
(DNS lookup failed): Indicates a DNS failure of either\nEAI_NODATA
or EAI_NONAME
. This is not a standard POSIX error.
EPERM
(Operation not permitted): An attempt was made to perform an\noperation that requires elevated privileges.
EPIPE
(Broken pipe): A write on a pipe, socket, or FIFO for which there is\nno process to read the data. Commonly encountered at the net
and\nhttp
layers, indicative that the remote side of the stream being\nwritten to has been closed.
ETIMEDOUT
(Operation timed out): A connect or send request failed because\nthe connected party did not properly respond after a period of time. Usually\nencountered by http
or net
. Often a sign that a socket.end()
\nwas not properly called.
Indicates that a provided argument is not an allowable type. For example,\npassing a function to a parameter which expects a string would be a TypeError
.
require('node:url').parse(() => { });\n// Throws TypeError, since it expected a string.\n
\nNode.js will generate and throw TypeError
instances immediately as a form\nof argument validation.
A browser-compatible implementation of ByteLengthQueuingStrategy
.
A browser-compatible implementation of CompressionStream
.
A browser-compatible implementation of CountQueuingStrategy
.
A browser-compatible implementation of DecompressionStream
.
A browser-compatible implementation of ReadableByteStreamController
.
A browser-compatible implementation of ReadableStream
.
A browser-compatible implementation of ReadableStreamBYOBReader
.
A browser-compatible implementation of ReadableStreamBYOBRequest
.
A browser-compatible implementation of ReadableStreamDefaultController
.
A browser-compatible implementation of ReadableStreamDefaultReader
.
A browser-compatible implementation of TextDecoderStream
.
A browser-compatible implementation of TextEncoderStream
.
A browser-compatible implementation of TransformStream
.
A browser-compatible implementation of TransformStreamDefaultController
.
A browser-compatible implementation of WritableStream
.
A browser-compatible implementation of WritableStreamDefaultController
.
A browser-compatible implementation of WritableStreamDefaultWriter
.
A utility class used to signal cancelation in selected Promise
-based APIs.\nThe API is based on the Web API AbortController
.
const ac = new AbortController();\n\nac.signal.addEventListener('abort', () => console.log('Aborted!'),\n { once: true });\n\nac.abort();\n\nconsole.log(ac.signal.aborted); // Prints true\n
",
"methods": [
{
"textRaw": "`abortController.abort([reason])`",
"type": "method",
"name": "abort",
"meta": {
"added": [
"v15.0.0",
"v14.17.0"
],
"changes": [
{
"version": [
"v17.2.0",
"v16.14.0"
],
"pr-url": "https://github.com/nodejs/node/pull/40807",
"description": "Added the new optional reason argument."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`reason` {any} An optional reason, retrievable on the `AbortSignal`'s `reason` property.",
"name": "reason",
"type": "any",
"desc": "An optional reason, retrievable on the `AbortSignal`'s `reason` property."
}
]
}
],
"desc": "Triggers the abort signal, causing the abortController.signal
to emit\nthe 'abort'
event.
The AbortSignal
is used to notify observers when the\nabortController.abort()
method is called.
Returns a new already aborted AbortSignal
.
Returns a new AbortSignal
which will be aborted in delay
milliseconds.
Returns a new AbortSignal
which will be aborted if any of the provided\nsignals are aborted. Its abortSignal.reason
will be set to whichever\none of the signals
caused it to be aborted.
The 'abort'
event is emitted when the abortController.abort()
method\nis called. The callback is invoked with a single object argument with a\nsingle type
property set to 'abort'
:
const ac = new AbortController();\n\n// Use either the onabort property...\nac.signal.onabort = () => console.log('aborted!');\n\n// Or the EventTarget API...\nac.signal.addEventListener('abort', (event) => {\n console.log(event.type); // Prints 'abort'\n}, { once: true });\n\nac.abort();\n
\nThe AbortController
with which the AbortSignal
is associated will only\never trigger the 'abort'
event once. We recommended that code check\nthat the abortSignal.aborted
attribute is false
before adding an 'abort'
\nevent listener.
Any event listeners attached to the AbortSignal
should use the\n{ once: true }
option (or, if using the EventEmitter
APIs to attach a\nlistener, use the once()
method) to ensure that the event listener is\nremoved as soon as the 'abort'
event is handled. Failure to do so may\nresult in memory leaks.
An optional callback function that may be set by user code to be notified\nwhen the abortController.abort()
function has been called.
An optional reason specified when the AbortSignal
was triggered.
const ac = new AbortController();\nac.abort(new Error('boom!'));\nconsole.log(ac.signal.reason); // Error: boom!\n
"
}
],
"methods": [
{
"textRaw": "`abortSignal.throwIfAborted()`",
"type": "method",
"name": "throwIfAborted",
"meta": {
"added": [
"v17.3.0",
"v16.17.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "If abortSignal.aborted
is true
, throws abortSignal.reason
.
See <Blob>.
", "source": "doc/api/globals.md" }, { "textRaw": "Class: `Buffer`", "type": "global", "name": "Buffer", "meta": { "added": [ "v0.1.103" ], "changes": [] }, "desc": "Used to handle binary data. See the buffer section.
", "source": "doc/api/globals.md" }, { "textRaw": "`clearImmediate(immediateObject)`", "type": "global", "name": "clearImmediate", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "desc": "clearImmediate
is described in the timers section.
clearInterval
is described in the timers section.
clearTimeout
is described in the timers section.
Used to print to stdout and stderr. See the console
section.
A browser-compatible implementation of the CustomEvent
Web API.
A browser-compatible implementation of the Event
class. See\nEventTarget
and Event
API for more details.
A browser-compatible implementation of the EventTarget
class. See\nEventTarget
and Event
API for more details.
See <File>.
", "source": "doc/api/globals.md" }, { "textRaw": "`global`", "name": "`global`", "meta": { "added": [ "v0.1.27" ], "changes": [] }, "type": "global", "stability": 3, "stabilityText": "Legacy. Use [`globalThis`][] instead.", "desc": "In browsers, the top-level scope has traditionally been the global scope. This\nmeans that var something
will define a new global variable, except within\nECMAScript modules. In Node.js, this is different. The top-level scope is not\nthe global scope; var something
inside a Node.js module will be local to that\nmodule, regardless of whether it is a CommonJS module or an\nECMAScript module.
The MessageChannel
class. See MessageChannel
for more details.
The MessageEvent
class. See MessageEvent
for more details.
The MessagePort
class. See MessagePort
for more details.
The PerformanceEntry
class. See PerformanceEntry
for more details.
The PerformanceMark
class. See PerformanceMark
for more details.
The PerformanceMeasure
class. See PerformanceMeasure
for more details.
The PerformanceObserver
class. See PerformanceObserver
for more details.
The PerformanceObserverEntryList
class. See\nPerformanceObserverEntryList
for more details.
The PerformanceResourceTiming
class. See PerformanceResourceTiming
for\nmore details.
The process object. See the process
object section.
callback
<Function> Function to be queued.The queueMicrotask()
method queues a microtask to invoke callback
. If\ncallback
throws an exception, the process
object 'uncaughtException'
\nevent will be emitted.
The microtask queue is managed by V8 and may be used in a similar manner to\nthe process.nextTick()
queue, which is managed by Node.js. The\nprocess.nextTick()
queue is always processed before the microtask queue\nwithin each turn of the Node.js event loop.
// Here, `queueMicrotask()` is used to ensure the 'load' event is always\n// emitted asynchronously, and therefore consistently. Using\n// `process.nextTick()` here would result in the 'load' event always emitting\n// before any other promise jobs.\n\nDataHandler.prototype.load = async function load(key) {\n const hit = this._cache.get(key);\n if (hit !== undefined) {\n queueMicrotask(() => {\n this.emit('load', hit);\n });\n return;\n }\n\n const data = await fetchData(key);\n this._cache.set(key, data);\n this.emit('load', data);\n};\n
",
"source": "doc/api/globals.md"
},
{
"textRaw": "`setImmediate(callback[, ...args])`",
"type": "global",
"name": "setImmediate",
"meta": {
"added": [
"v0.9.1"
],
"changes": []
},
"desc": "setImmediate
is described in the timers section.
setInterval
is described in the timers section.
setTimeout
is described in the timers section.
The WHATWG structuredClone
method.
The WHATWG DOMException
class. See DOMException
for more details.
The WHATWG TextDecoder
class. See the TextDecoder
section.
The WHATWG TextEncoder
class. See the TextEncoder
section.
The WHATWG URL
class. See the URL
section.
The WHATWG URLSearchParams
class. See the URLSearchParams
section.
The object that acts as the namespace for all W3C\nWebAssembly related functionality. See the\nMozilla Developer Network for usage and compatibility.
", "source": "doc/api/globals.md" }, { "textRaw": "Process", "name": "Process", "introduced_in": "v0.10.0", "type": "global", "desc": "Source Code: lib/process.js
\nThe process
object provides information about, and control over, the current\nNode.js process.
import process from 'node:process';\n
\nconst process = require('node:process');\n
",
"modules": [
{
"textRaw": "Process events",
"name": "process_events",
"desc": "The process
object is an instance of EventEmitter
.
The 'beforeExit'
event is emitted when Node.js empties its event loop and has\nno additional work to schedule. Normally, the Node.js process will exit when\nthere is no work scheduled, but a listener registered on the 'beforeExit'
\nevent can make asynchronous calls, and thereby cause the Node.js process to\ncontinue.
The listener callback function is invoked with the value of\nprocess.exitCode
passed as the only argument.
The 'beforeExit'
event is not emitted for conditions causing explicit\ntermination, such as calling process.exit()
or uncaught exceptions.
The 'beforeExit'
should not be used as an alternative to the 'exit'
event\nunless the intention is to schedule additional work.
import process from 'node:process';\n\nprocess.on('beforeExit', (code) => {\n console.log('Process beforeExit event with code: ', code);\n});\n\nprocess.on('exit', (code) => {\n console.log('Process exit event with code: ', code);\n});\n\nconsole.log('This message is displayed first.');\n\n// Prints:\n// This message is displayed first.\n// Process beforeExit event with code: 0\n// Process exit event with code: 0\n
\nconst process = require('node:process');\n\nprocess.on('beforeExit', (code) => {\n console.log('Process beforeExit event with code: ', code);\n});\n\nprocess.on('exit', (code) => {\n console.log('Process exit event with code: ', code);\n});\n\nconsole.log('This message is displayed first.');\n\n// Prints:\n// This message is displayed first.\n// Process beforeExit event with code: 0\n// Process exit event with code: 0\n
"
},
{
"textRaw": "Event: `'disconnect'`",
"type": "event",
"name": "disconnect",
"meta": {
"added": [
"v0.7.7"
],
"changes": []
},
"params": [],
"desc": "If the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the 'disconnect'
event will be emitted when\nthe IPC channel is closed.
The 'exit'
event is emitted when the Node.js process is about to exit as a\nresult of either:
process.exit()
method being called explicitly;There is no way to prevent the exiting of the event loop at this point, and once\nall 'exit'
listeners have finished running the Node.js process will terminate.
The listener callback function is invoked with the exit code specified either\nby the process.exitCode
property, or the exitCode
argument passed to the\nprocess.exit()
method.
import process from 'node:process';\n\nprocess.on('exit', (code) => {\n console.log(`About to exit with code: ${code}`);\n});\n
\nconst process = require('node:process');\n\nprocess.on('exit', (code) => {\n console.log(`About to exit with code: ${code}`);\n});\n
\nListener functions must only perform synchronous operations. The Node.js\nprocess will exit immediately after calling the 'exit'
event listeners\ncausing any additional work still queued in the event loop to be abandoned.\nIn the following example, for instance, the timeout will never occur:
import process from 'node:process';\n\nprocess.on('exit', (code) => {\n setTimeout(() => {\n console.log('This will not run');\n }, 0);\n});\n
\nconst process = require('node:process');\n\nprocess.on('exit', (code) => {\n setTimeout(() => {\n console.log('This will not run');\n }, 0);\n});\n
"
},
{
"textRaw": "Event: `'message'`",
"type": "event",
"name": "message",
"meta": {
"added": [
"v0.5.10"
],
"changes": []
},
"params": [
{
"textRaw": "`message` { Object | boolean | number | string | null } a parsed JSON object or a serializable primitive value.",
"name": "message",
"type": " Object | boolean | number | string | null ",
"desc": "a parsed JSON object or a serializable primitive value."
},
{
"textRaw": "`sendHandle` {net.Server|net.Socket} a [`net.Server`][] or [`net.Socket`][] object, or undefined.",
"name": "sendHandle",
"type": "net.Server|net.Socket",
"desc": "a [`net.Server`][] or [`net.Socket`][] object, or undefined."
}
],
"desc": "If the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the 'message'
event is emitted whenever a\nmessage sent by a parent process using childprocess.send()
is received by\nthe child process.
The message goes through serialization and parsing. The resulting message might\nnot be the same as what is originally sent.
\nIf the serialization
option was set to advanced
used when spawning the\nprocess, the message
argument can contain data that JSON is not able\nto represent.\nSee Advanced serialization for child_process
for more details.
The 'multipleResolves'
event is emitted whenever a Promise
has been either:
This is useful for tracking potential errors in an application while using the\nPromise
constructor, as multiple resolutions are silently swallowed. However,\nthe occurrence of this event does not necessarily indicate an error. For\nexample, Promise.race()
can trigger a 'multipleResolves'
event.
Because of the unreliability of the event in cases like the\nPromise.race()
example above it has been deprecated.
import process from 'node:process';\n\nprocess.on('multipleResolves', (type, promise, reason) => {\n console.error(type, promise, reason);\n setImmediate(() => process.exit(1));\n});\n\nasync function main() {\n try {\n return await new Promise((resolve, reject) => {\n resolve('First call');\n resolve('Swallowed resolve');\n reject(new Error('Swallowed reject'));\n });\n } catch {\n throw new Error('Failed');\n }\n}\n\nmain().then(console.log);\n// resolve: Promise { 'First call' } 'Swallowed resolve'\n// reject: Promise { 'First call' } Error: Swallowed reject\n// at Promise (*)\n// at new Promise (<anonymous>)\n// at main (*)\n// First call\n
\nconst process = require('node:process');\n\nprocess.on('multipleResolves', (type, promise, reason) => {\n console.error(type, promise, reason);\n setImmediate(() => process.exit(1));\n});\n\nasync function main() {\n try {\n return await new Promise((resolve, reject) => {\n resolve('First call');\n resolve('Swallowed resolve');\n reject(new Error('Swallowed reject'));\n });\n } catch {\n throw new Error('Failed');\n }\n}\n\nmain().then(console.log);\n// resolve: Promise { 'First call' } 'Swallowed resolve'\n// reject: Promise { 'First call' } Error: Swallowed reject\n// at Promise (*)\n// at new Promise (<anonymous>)\n// at main (*)\n// First call\n
"
},
{
"textRaw": "Event: `'rejectionHandled'`",
"type": "event",
"name": "rejectionHandled",
"meta": {
"added": [
"v1.4.1"
],
"changes": []
},
"params": [
{
"textRaw": "`promise` {Promise} The late handled promise.",
"name": "promise",
"type": "Promise",
"desc": "The late handled promise."
}
],
"desc": "The 'rejectionHandled'
event is emitted whenever a Promise
has been rejected\nand an error handler was attached to it (using promise.catch()
, for\nexample) later than one turn of the Node.js event loop.
The Promise
object would have previously been emitted in an\n'unhandledRejection'
event, but during the course of processing gained a\nrejection handler.
There is no notion of a top level for a Promise
chain at which rejections can\nalways be handled. Being inherently asynchronous in nature, a Promise
\nrejection can be handled at a future point in time, possibly much later than\nthe event loop turn it takes for the 'unhandledRejection'
event to be emitted.
Another way of stating this is that, unlike in synchronous code where there is\nan ever-growing list of unhandled exceptions, with Promises there can be a\ngrowing-and-shrinking list of unhandled rejections.
\nIn synchronous code, the 'uncaughtException'
event is emitted when the list of\nunhandled exceptions grows.
In asynchronous code, the 'unhandledRejection'
event is emitted when the list\nof unhandled rejections grows, and the 'rejectionHandled'
event is emitted\nwhen the list of unhandled rejections shrinks.
import process from 'node:process';\n\nconst unhandledRejections = new Map();\nprocess.on('unhandledRejection', (reason, promise) => {\n unhandledRejections.set(promise, reason);\n});\nprocess.on('rejectionHandled', (promise) => {\n unhandledRejections.delete(promise);\n});\n
\nconst process = require('node:process');\n\nconst unhandledRejections = new Map();\nprocess.on('unhandledRejection', (reason, promise) => {\n unhandledRejections.set(promise, reason);\n});\nprocess.on('rejectionHandled', (promise) => {\n unhandledRejections.delete(promise);\n});\n
\nIn this example, the unhandledRejections
Map
will grow and shrink over time,\nreflecting rejections that start unhandled and then become handled. It is\npossible to record such errors in an error log, either periodically (which is\nlikely best for long-running application) or upon process exit (which is likely\nmost convenient for scripts).
The 'uncaughtException'
event is emitted when an uncaught JavaScript\nexception bubbles all the way back to the event loop. By default, Node.js\nhandles such exceptions by printing the stack trace to stderr
and exiting\nwith code 1, overriding any previously set process.exitCode
.\nAdding a handler for the 'uncaughtException'
event overrides this default\nbehavior. Alternatively, change the process.exitCode
in the\n'uncaughtException'
handler which will result in the process exiting with the\nprovided exit code. Otherwise, in the presence of such handler the process will\nexit with 0.
import process from 'node:process';\nimport fs from 'node:fs';\n\nprocess.on('uncaughtException', (err, origin) => {\n fs.writeSync(\n process.stderr.fd,\n `Caught exception: ${err}\\n` +\n `Exception origin: ${origin}\\n`,\n );\n});\n\nsetTimeout(() => {\n console.log('This will still run.');\n}, 500);\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\nconsole.log('This will not run.');\n
\nconst process = require('node:process');\nconst fs = require('node:fs');\n\nprocess.on('uncaughtException', (err, origin) => {\n fs.writeSync(\n process.stderr.fd,\n `Caught exception: ${err}\\n` +\n `Exception origin: ${origin}\\n`,\n );\n});\n\nsetTimeout(() => {\n console.log('This will still run.');\n}, 500);\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\nconsole.log('This will not run.');\n
\nIt is possible to monitor 'uncaughtException'
events without overriding the\ndefault behavior to exit the process by installing a\n'uncaughtExceptionMonitor'
listener.
'uncaughtException'
is a crude mechanism for exception handling\nintended to be used only as a last resort. The event should not be used as\nan equivalent to On Error Resume Next
. Unhandled exceptions inherently mean\nthat an application is in an undefined state. Attempting to resume application\ncode without properly recovering from the exception can cause additional\nunforeseen and unpredictable issues.
Exceptions thrown from within the event handler will not be caught. Instead the\nprocess will exit with a non-zero exit code and the stack trace will be printed.\nThis is to avoid infinite recursion.
\nAttempting to resume normally after an uncaught exception can be similar to\npulling out the power cord when upgrading a computer. Nine out of ten\ntimes, nothing happens. But the tenth time, the system becomes corrupted.
\nThe correct use of 'uncaughtException'
is to perform synchronous cleanup\nof allocated resources (e.g. file descriptors, handles, etc) before shutting\ndown the process. It is not safe to resume normal operation after\n'uncaughtException'
.
To restart a crashed application in a more reliable way, whether\n'uncaughtException'
is emitted or not, an external monitor should be employed\nin a separate process to detect application failures and recover or restart as\nneeded.
The 'uncaughtExceptionMonitor'
event is emitted before an\n'uncaughtException'
event is emitted or a hook installed via\nprocess.setUncaughtExceptionCaptureCallback()
is called.
Installing an 'uncaughtExceptionMonitor'
listener does not change the behavior\nonce an 'uncaughtException'
event is emitted. The process will\nstill crash if no 'uncaughtException'
listener is installed.
import process from 'node:process';\n\nprocess.on('uncaughtExceptionMonitor', (err, origin) => {\n MyMonitoringTool.logSync(err, origin);\n});\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\n// Still crashes Node.js\n
\nconst process = require('node:process');\n\nprocess.on('uncaughtExceptionMonitor', (err, origin) => {\n MyMonitoringTool.logSync(err, origin);\n});\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\n// Still crashes Node.js\n
"
},
{
"textRaw": "Event: `'unhandledRejection'`",
"type": "event",
"name": "unhandledRejection",
"meta": {
"added": [
"v1.4.1"
],
"changes": [
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/8217",
"description": "Not handling `Promise` rejections is deprecated."
},
{
"version": "v6.6.0",
"pr-url": "https://github.com/nodejs/node/pull/8223",
"description": "Unhandled `Promise` rejections will now emit a process warning."
}
]
},
"params": [
{
"textRaw": "`reason` {Error|any} The object with which the promise was rejected (typically an [`Error`][] object).",
"name": "reason",
"type": "Error|any",
"desc": "The object with which the promise was rejected (typically an [`Error`][] object)."
},
{
"textRaw": "`promise` {Promise} The rejected promise.",
"name": "promise",
"type": "Promise",
"desc": "The rejected promise."
}
],
"desc": "The 'unhandledRejection'
event is emitted whenever a Promise
is rejected and\nno error handler is attached to the promise within a turn of the event loop.\nWhen programming with Promises, exceptions are encapsulated as \"rejected\npromises\". Rejections can be caught and handled using promise.catch()
and\nare propagated through a Promise
chain. The 'unhandledRejection'
event is\nuseful for detecting and keeping track of promises that were rejected whose\nrejections have not yet been handled.
import process from 'node:process';\n\nprocess.on('unhandledRejection', (reason, promise) => {\n console.log('Unhandled Rejection at:', promise, 'reason:', reason);\n // Application specific logging, throwing an error, or other logic here\n});\n\nsomePromise.then((res) => {\n return reportToUser(JSON.pasre(res)); // Note the typo (`pasre`)\n}); // No `.catch()` or `.then()`\n
\nconst process = require('node:process');\n\nprocess.on('unhandledRejection', (reason, promise) => {\n console.log('Unhandled Rejection at:', promise, 'reason:', reason);\n // Application specific logging, throwing an error, or other logic here\n});\n\nsomePromise.then((res) => {\n return reportToUser(JSON.pasre(res)); // Note the typo (`pasre`)\n}); // No `.catch()` or `.then()`\n
\nThe following will also trigger the 'unhandledRejection'
event to be\nemitted:
import process from 'node:process';\n\nfunction SomeResource() {\n // Initially set the loaded status to a rejected promise\n this.loaded = Promise.reject(new Error('Resource not yet loaded!'));\n}\n\nconst resource = new SomeResource();\n// no .catch or .then on resource.loaded for at least a turn\n
\nconst process = require('node:process');\n\nfunction SomeResource() {\n // Initially set the loaded status to a rejected promise\n this.loaded = Promise.reject(new Error('Resource not yet loaded!'));\n}\n\nconst resource = new SomeResource();\n// no .catch or .then on resource.loaded for at least a turn\n
\nIn this example case, it is possible to track the rejection as a developer error\nas would typically be the case for other 'unhandledRejection'
events. To\naddress such failures, a non-operational\n.catch(() => { })
handler may be attached to\nresource.loaded
, which would prevent the 'unhandledRejection'
event from\nbeing emitted.
The 'warning'
event is emitted whenever Node.js emits a process warning.
A process warning is similar to an error in that it describes exceptional\nconditions that are being brought to the user's attention. However, warnings\nare not part of the normal Node.js and JavaScript error handling flow.\nNode.js can emit warnings whenever it detects bad coding practices that could\nlead to sub-optimal application performance, bugs, or security vulnerabilities.
\nimport process from 'node:process';\n\nprocess.on('warning', (warning) => {\n console.warn(warning.name); // Print the warning name\n console.warn(warning.message); // Print the warning message\n console.warn(warning.stack); // Print the stack trace\n});\n
\nconst process = require('node:process');\n\nprocess.on('warning', (warning) => {\n console.warn(warning.name); // Print the warning name\n console.warn(warning.message); // Print the warning message\n console.warn(warning.stack); // Print the stack trace\n});\n
\nBy default, Node.js will print process warnings to stderr
. The --no-warnings
\ncommand-line option can be used to suppress the default console output but the\n'warning'
event will still be emitted by the process
object. Currently, it\nis not possible to suppress specific warning types other than deprecation\nwarnings. To suppress deprecation warnings, check out the --no-deprecation
\nflag.
The following example illustrates the warning that is printed to stderr
when\ntoo many listeners have been added to an event:
$ node\n> events.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> (node:38638) MaxListenersExceededWarning: Possible EventEmitter memory leak\ndetected. 2 foo listeners added. Use emitter.setMaxListeners() to increase limit\n
\nIn contrast, the following example turns off the default warning output and\nadds a custom handler to the 'warning'
event:
$ node --no-warnings\n> const p = process.on('warning', (warning) => console.warn('Do not do that!'));\n> events.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> Do not do that!\n
\nThe --trace-warnings
command-line option can be used to have the default\nconsole output for warnings include the full stack trace of the warning.
Launching Node.js using the --throw-deprecation
command-line flag will\ncause custom deprecation warnings to be thrown as exceptions.
Using the --trace-deprecation
command-line flag will cause the custom\ndeprecation to be printed to stderr
along with the stack trace.
Using the --no-deprecation
command-line flag will suppress all reporting\nof the custom deprecation.
The *-deprecation
command-line flags only affect warnings that use the name\n'DeprecationWarning'
.
See the process.emitWarning()
method for issuing\ncustom or application-specific warnings.
There are no strict guidelines for warning types (as identified by the name
\nproperty) emitted by Node.js. New types of warnings can be added at any time.\nA few of the warning types that are most common include:
'DeprecationWarning'
- Indicates use of a deprecated Node.js API or feature.\nSuch warnings must include a 'code'
property identifying the\ndeprecation code.'ExperimentalWarning'
- Indicates use of an experimental Node.js API or\nfeature. Such features must be used with caution as they may change at any\ntime and are not subject to the same strict semantic-versioning and long-term\nsupport policies as supported features.'MaxListenersExceededWarning'
- Indicates that too many listeners for a\ngiven event have been registered on either an EventEmitter
or EventTarget
.\nThis is often an indication of a memory leak.'TimeoutOverflowWarning'
- Indicates that a numeric value that cannot fit\nwithin a 32-bit signed integer has been provided to either the setTimeout()
\nor setInterval()
functions.'UnsupportedWarning'
- Indicates use of an unsupported option or feature\nthat will be ignored rather than treated as an error. One example is use of\nthe HTTP response status message when using the HTTP/2 compatibility API.The 'worker'
event is emitted after a new <Worker> thread has been created.
Signal events will be emitted when the Node.js process receives a signal. Please\nrefer to signal(7)
for a listing of standard POSIX signal names such as\n'SIGINT'
, 'SIGHUP'
, etc.
Signals are not available on Worker
threads.
The signal handler will receive the signal's name ('SIGINT'
,\n'SIGTERM'
, etc.) as the first argument.
The name of each event will be the uppercase common name for the signal (e.g.\n'SIGINT'
for SIGINT
signals).
import process from 'node:process';\n\n// Begin reading from stdin so the process does not exit.\nprocess.stdin.resume();\n\nprocess.on('SIGINT', () => {\n console.log('Received SIGINT. Press Control-D to exit.');\n});\n\n// Using a single function to handle multiple signals\nfunction handle(signal) {\n console.log(`Received ${signal}`);\n}\n\nprocess.on('SIGINT', handle);\nprocess.on('SIGTERM', handle);\n
\nconst process = require('node:process');\n\n// Begin reading from stdin so the process does not exit.\nprocess.stdin.resume();\n\nprocess.on('SIGINT', () => {\n console.log('Received SIGINT. Press Control-D to exit.');\n});\n\n// Using a single function to handle multiple signals\nfunction handle(signal) {\n console.log(`Received ${signal}`);\n}\n\nprocess.on('SIGINT', handle);\nprocess.on('SIGTERM', handle);\n
\n'SIGUSR1'
is reserved by Node.js to start the debugger. It's possible to\ninstall a listener but doing so might interfere with the debugger.'SIGTERM'
and 'SIGINT'
have default handlers on non-Windows platforms that\nreset the terminal mode before exiting with code 128 + signal number
. If one\nof these signals has a listener installed, its default behavior will be\nremoved (Node.js will no longer exit).'SIGPIPE'
is ignored by default. It can have a listener installed.'SIGHUP'
is generated on Windows when the console window is closed, and on\nother platforms under various similar conditions. See signal(7)
. It can have a\nlistener installed, however Node.js will be unconditionally terminated by\nWindows about 10 seconds later. On non-Windows platforms, the default\nbehavior of SIGHUP
is to terminate Node.js, but once a listener has been\ninstalled its default behavior will be removed.'SIGTERM'
is not supported on Windows, it can be listened on.'SIGINT'
from the terminal is supported on all platforms, and can usually be\ngenerated with Ctrl+C (though this may be configurable).\nIt is not generated when terminal raw mode is enabled\nand Ctrl+C is used.'SIGBREAK'
is delivered on Windows when Ctrl+Break is\npressed. On non-Windows platforms, it can be listened on, but there is no way\nto send or generate it.'SIGWINCH'
is delivered when the console has been resized. On Windows, this\nwill only happen on write to the console when the cursor is being moved, or\nwhen a readable tty is used in raw mode.'SIGKILL'
cannot have a listener installed, it will unconditionally\nterminate Node.js on all platforms.'SIGSTOP'
cannot have a listener installed.'SIGBUS'
, 'SIGFPE'
, 'SIGSEGV'
, and 'SIGILL'
, when not raised\nartificially using kill(2)
, inherently leave the process in a state from\nwhich it is not safe to call JS listeners. Doing so might cause the process\nto stop responding.0
can be sent to test for the existence of a process, it has no effect if\nthe process exists, but will throw an error if the process does not exist.Windows does not support signals so has no equivalent to termination by signal,\nbut Node.js offers some emulation with process.kill()
, and\nsubprocess.kill()
:
SIGINT
, SIGTERM
, and SIGKILL
will cause the unconditional\ntermination of the target process, and afterwards, subprocess will report that\nthe process was terminated by signal.0
can be used as a platform independent way to test for the\nexistence of a process.Node.js will normally exit with a 0
status code when no more async\noperations are pending. The following status codes are used in other\ncases:
1
Uncaught Fatal Exception: There was an uncaught exception,\nand it was not handled by a domain or an 'uncaughtException'
event\nhandler.2
: Unused (reserved by Bash for builtin misuse)3
Internal JavaScript Parse Error: The JavaScript source code\ninternal in the Node.js bootstrapping process caused a parse error. This\nis extremely rare, and generally can only happen during development\nof Node.js itself.4
Internal JavaScript Evaluation Failure: The JavaScript\nsource code internal in the Node.js bootstrapping process failed to\nreturn a function value when evaluated. This is extremely rare, and\ngenerally can only happen during development of Node.js itself.5
Fatal Error: There was a fatal unrecoverable error in V8.\nTypically a message will be printed to stderr with the prefix FATAL ERROR
.6
Non-function Internal Exception Handler: There was an\nuncaught exception, but the internal fatal exception handler\nfunction was somehow set to a non-function, and could not be called.7
Internal Exception Handler Run-Time Failure: There was an\nuncaught exception, and the internal fatal exception handler\nfunction itself threw an error while attempting to handle it. This\ncan happen, for example, if an 'uncaughtException'
or\ndomain.on('error')
handler throws an error.8
: Unused. In previous versions of Node.js, exit code 8 sometimes\nindicated an uncaught exception.9
Invalid Argument: Either an unknown option was specified,\nor an option requiring a value was provided without a value.10
Internal JavaScript Run-Time Failure: The JavaScript\nsource code internal in the Node.js bootstrapping process threw an error\nwhen the bootstrapping function was called. This is extremely rare,\nand generally can only happen during development of Node.js itself.12
Invalid Debug Argument: The --inspect
and/or --inspect-brk
\noptions were set, but the port number chosen was invalid or unavailable.13
Unfinished Top-Level Await: await
was used outside of a function\nin the top-level code, but the passed Promise
never resolved.14
Snapshot Failure: Node.js was started to build a V8 startup\nsnapshot and it failed because certain requirements of the state of\nthe application were not met.>128
Signal Exits: If Node.js receives a fatal signal such as\nSIGKILL
or SIGHUP
, then its exit code will be 128
plus the\nvalue of the signal code. This is a standard POSIX practice, since\nexit codes are defined to be 7-bit integers, and signal exits set\nthe high-order bit, and then contain the value of the signal code.\nFor example, signal SIGABRT
has value 6
, so the expected exit\ncode will be 128
+ 6
, or 134
.The process.abort()
method causes the Node.js process to exit immediately and\ngenerate a core file.
This feature is not available in Worker
threads.
The process.chdir()
method changes the current working directory of the\nNode.js process or throws an exception if doing so fails (for instance, if\nthe specified directory
does not exist).
import { chdir, cwd } from 'node:process';\n\nconsole.log(`Starting directory: ${cwd()}`);\ntry {\n chdir('/tmp');\n console.log(`New directory: ${cwd()}`);\n} catch (err) {\n console.error(`chdir: ${err}`);\n}\n
\nconst { chdir, cwd } = require('node:process');\n\nconsole.log(`Starting directory: ${cwd()}`);\ntry {\n chdir('/tmp');\n console.log(`New directory: ${cwd()}`);\n} catch (err) {\n console.error(`chdir: ${err}`);\n}\n
\nThis feature is not available in Worker
threads.
Gets the amount of memory available to the process (in bytes) based on\nlimits imposed by the OS. If there is no such constraint, or the constraint\nis unknown, undefined
is returned.
See uv_get_constrained_memory
for more\ninformation.
The process.cpuUsage()
method returns the user and system CPU time usage of\nthe current process, in an object with properties user
and system
, whose\nvalues are microsecond values (millionth of a second). These values measure time\nspent in user and system code respectively, and may end up being greater than\nactual elapsed time if multiple CPU cores are performing work for this process.
The result of a previous call to process.cpuUsage()
can be passed as the\nargument to the function, to get a diff reading.
import { cpuUsage } from 'node:process';\n\nconst startUsage = cpuUsage();\n// { user: 38579, system: 6986 }\n\n// spin the CPU for 500 milliseconds\nconst now = Date.now();\nwhile (Date.now() - now < 500);\n\nconsole.log(cpuUsage(startUsage));\n// { user: 514883, system: 11226 }\n
\nconst { cpuUsage } = require('node:process');\n\nconst startUsage = cpuUsage();\n// { user: 38579, system: 6986 }\n\n// spin the CPU for 500 milliseconds\nconst now = Date.now();\nwhile (Date.now() - now < 500);\n\nconsole.log(cpuUsage(startUsage));\n// { user: 514883, system: 11226 }\n
"
},
{
"textRaw": "`process.cwd()`",
"type": "method",
"name": "cwd",
"meta": {
"added": [
"v0.1.8"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": []
}
],
"desc": "The process.cwd()
method returns the current working directory of the Node.js\nprocess.
import { cwd } from 'node:process';\n\nconsole.log(`Current directory: ${cwd()}`);\n
\nconst { cwd } = require('node:process');\n\nconsole.log(`Current directory: ${cwd()}`);\n
"
},
{
"textRaw": "`process.disconnect()`",
"type": "method",
"name": "disconnect",
"meta": {
"added": [
"v0.7.2"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "If the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the process.disconnect()
method will close the\nIPC channel to the parent process, allowing the child process to exit gracefully\nonce there are no other connections keeping it alive.
The effect of calling process.disconnect()
is the same as calling\nChildProcess.disconnect()
from the parent process.
If the Node.js process was not spawned with an IPC channel,\nprocess.disconnect()
will be undefined
.
The process.dlopen()
method allows dynamically loading shared objects. It is\nprimarily used by require()
to load C++ Addons, and should not be used\ndirectly, except in special cases. In other words, require()
should be\npreferred over process.dlopen()
unless there are specific reasons such as\ncustom dlopen flags or loading from ES modules.
The flags
argument is an integer that allows to specify dlopen\nbehavior. See the os.constants.dlopen
documentation for details.
An important requirement when calling process.dlopen()
is that the module
\ninstance must be passed. Functions exported by the C++ Addon are then\naccessible via module.exports
.
The example below shows how to load a C++ Addon, named local.node
,\nthat exports a foo
function. All the symbols are loaded before\nthe call returns, by passing the RTLD_NOW
constant. In this example\nthe constant is assumed to be available.
import { dlopen } from 'node:process';\nimport { constants } from 'node:os';\nimport { fileURLToPath } from 'node:url';\n\nconst module = { exports: {} };\ndlopen(module, fileURLToPath(new URL('local.node', import.meta.url)),\n constants.dlopen.RTLD_NOW);\nmodule.exports.foo();\n
\nconst { dlopen } = require('node:process');\nconst { constants } = require('node:os');\nconst { join } = require('node:path');\n\nconst module = { exports: {} };\ndlopen(module, join(__dirname, 'local.node'), constants.dlopen.RTLD_NOW);\nmodule.exports.foo();\n
"
},
{
"textRaw": "`process.emitWarning(warning[, options])`",
"type": "method",
"name": "emitWarning",
"meta": {
"added": [
"v8.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`warning` {string|Error} The warning to emit.",
"name": "warning",
"type": "string|Error",
"desc": "The warning to emit."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`type` {string} When `warning` is a `String`, `type` is the name to use for the _type_ of warning being emitted. **Default:** `'Warning'`.",
"name": "type",
"type": "string",
"default": "`'Warning'`",
"desc": "When `warning` is a `String`, `type` is the name to use for the _type_ of warning being emitted."
},
{
"textRaw": "`code` {string} A unique identifier for the warning instance being emitted.",
"name": "code",
"type": "string",
"desc": "A unique identifier for the warning instance being emitted."
},
{
"textRaw": "`ctor` {Function} When `warning` is a `String`, `ctor` is an optional function used to limit the generated stack trace. **Default:** `process.emitWarning`.",
"name": "ctor",
"type": "Function",
"default": "`process.emitWarning`",
"desc": "When `warning` is a `String`, `ctor` is an optional function used to limit the generated stack trace."
},
{
"textRaw": "`detail` {string} Additional text to include with the error.",
"name": "detail",
"type": "string",
"desc": "Additional text to include with the error."
}
]
}
]
}
],
"desc": "The process.emitWarning()
method can be used to emit custom or application\nspecific process warnings. These can be listened for by adding a handler to the\n'warning'
event.
import { emitWarning } from 'node:process';\n\n// Emit a warning with a code and additional detail.\nemitWarning('Something happened!', {\n code: 'MY_WARNING',\n detail: 'This is some additional information',\n});\n// Emits:\n// (node:56338) [MY_WARNING] Warning: Something happened!\n// This is some additional information\n
\nconst { emitWarning } = require('node:process');\n\n// Emit a warning with a code and additional detail.\nemitWarning('Something happened!', {\n code: 'MY_WARNING',\n detail: 'This is some additional information',\n});\n// Emits:\n// (node:56338) [MY_WARNING] Warning: Something happened!\n// This is some additional information\n
\nIn this example, an Error
object is generated internally by\nprocess.emitWarning()
and passed through to the\n'warning'
handler.
import process from 'node:process';\n\nprocess.on('warning', (warning) => {\n console.warn(warning.name); // 'Warning'\n console.warn(warning.message); // 'Something happened!'\n console.warn(warning.code); // 'MY_WARNING'\n console.warn(warning.stack); // Stack trace\n console.warn(warning.detail); // 'This is some additional information'\n});\n
\nconst process = require('node:process');\n\nprocess.on('warning', (warning) => {\n console.warn(warning.name); // 'Warning'\n console.warn(warning.message); // 'Something happened!'\n console.warn(warning.code); // 'MY_WARNING'\n console.warn(warning.stack); // Stack trace\n console.warn(warning.detail); // 'This is some additional information'\n});\n
\nIf warning
is passed as an Error
object, the options
argument is ignored.
The process.emitWarning()
method can be used to emit custom or application\nspecific process warnings. These can be listened for by adding a handler to the\n'warning'
event.
import { emitWarning } from 'node:process';\n\n// Emit a warning using a string.\nemitWarning('Something happened!');\n// Emits: (node: 56338) Warning: Something happened!\n
\nconst { emitWarning } = require('node:process');\n\n// Emit a warning using a string.\nemitWarning('Something happened!');\n// Emits: (node: 56338) Warning: Something happened!\n
\nimport { emitWarning } from 'node:process';\n\n// Emit a warning using a string and a type.\nemitWarning('Something Happened!', 'CustomWarning');\n// Emits: (node:56338) CustomWarning: Something Happened!\n
\nconst { emitWarning } = require('node:process');\n\n// Emit a warning using a string and a type.\nemitWarning('Something Happened!', 'CustomWarning');\n// Emits: (node:56338) CustomWarning: Something Happened!\n
\nimport { emitWarning } from 'node:process';\n\nemitWarning('Something happened!', 'CustomWarning', 'WARN001');\n// Emits: (node:56338) [WARN001] CustomWarning: Something happened!\n
\nconst { emitWarning } = require('node:process');\n\nprocess.emitWarning('Something happened!', 'CustomWarning', 'WARN001');\n// Emits: (node:56338) [WARN001] CustomWarning: Something happened!\n
\nIn each of the previous examples, an Error
object is generated internally by\nprocess.emitWarning()
and passed through to the 'warning'
\nhandler.
import process from 'node:process';\n\nprocess.on('warning', (warning) => {\n console.warn(warning.name);\n console.warn(warning.message);\n console.warn(warning.code);\n console.warn(warning.stack);\n});\n
\nconst process = require('node:process');\n\nprocess.on('warning', (warning) => {\n console.warn(warning.name);\n console.warn(warning.message);\n console.warn(warning.code);\n console.warn(warning.stack);\n});\n
\nIf warning
is passed as an Error
object, it will be passed through to the\n'warning'
event handler unmodified (and the optional type
,\ncode
and ctor
arguments will be ignored):
import { emitWarning } from 'node:process';\n\n// Emit a warning using an Error object.\nconst myWarning = new Error('Something happened!');\n// Use the Error name property to specify the type name\nmyWarning.name = 'CustomWarning';\nmyWarning.code = 'WARN001';\n\nemitWarning(myWarning);\n// Emits: (node:56338) [WARN001] CustomWarning: Something happened!\n
\nconst { emitWarning } = require('node:process');\n\n// Emit a warning using an Error object.\nconst myWarning = new Error('Something happened!');\n// Use the Error name property to specify the type name\nmyWarning.name = 'CustomWarning';\nmyWarning.code = 'WARN001';\n\nemitWarning(myWarning);\n// Emits: (node:56338) [WARN001] CustomWarning: Something happened!\n
\nA TypeError
is thrown if warning
is anything other than a string or Error
\nobject.
While process warnings use Error
objects, the process warning\nmechanism is not a replacement for normal error handling mechanisms.
The following additional handling is implemented if the warning type
is\n'DeprecationWarning'
:
--throw-deprecation
command-line flag is used, the deprecation\nwarning is thrown as an exception rather than being emitted as an event.--no-deprecation
command-line flag is used, the deprecation\nwarning is suppressed.--trace-deprecation
command-line flag is used, the deprecation\nwarning is printed to stderr
along with the full stack trace.As a best practice, warnings should be emitted only once per process. To do\nso, place the emitWarning()
behind a boolean.
import { emitWarning } from 'node:process';\n\nfunction emitMyWarning() {\n if (!emitMyWarning.warned) {\n emitMyWarning.warned = true;\n emitWarning('Only warn once!');\n }\n}\nemitMyWarning();\n// Emits: (node: 56339) Warning: Only warn once!\nemitMyWarning();\n// Emits nothing\n
\nconst { emitWarning } = require('node:process');\n\nfunction emitMyWarning() {\n if (!emitMyWarning.warned) {\n emitMyWarning.warned = true;\n emitWarning('Only warn once!');\n }\n}\nemitMyWarning();\n// Emits: (node: 56339) Warning: Only warn once!\nemitMyWarning();\n// Emits nothing\n
",
"type": "module",
"displayName": "Avoiding duplicate warnings"
}
]
},
{
"textRaw": "`process.exit([code])`",
"type": "method",
"name": "exit",
"meta": {
"added": [
"v0.1.13"
],
"changes": [
{
"version": "v20.0.0",
"pr-url": "https://github.com/nodejs/node/pull/43716",
"description": "Only accepts a code of type number, or of type string if it represents an integer."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`code` {integer|string|null|undefined} The exit code. For string type, only integer strings (e.g.,'1') are allowed. **Default:** `0`.",
"name": "code",
"type": "integer|string|null|undefined",
"default": "`0`",
"desc": "The exit code. For string type, only integer strings (e.g.,'1') are allowed."
}
]
}
],
"desc": "The process.exit()
method instructs Node.js to terminate the process\nsynchronously with an exit status of code
. If code
is omitted, exit uses\neither the 'success' code 0
or the value of process.exitCode
if it has been\nset. Node.js will not terminate until all the 'exit'
event listeners are\ncalled.
To exit with a 'failure' code:
\nimport { exit } from 'node:process';\n\nexit(1);\n
\nconst { exit } = require('node:process');\n\nexit(1);\n
\nThe shell that executed Node.js should see the exit code as 1
.
Calling process.exit()
will force the process to exit as quickly as possible\neven if there are still asynchronous operations pending that have not yet\ncompleted fully, including I/O operations to process.stdout
and\nprocess.stderr
.
In most situations, it is not actually necessary to call process.exit()
\nexplicitly. The Node.js process will exit on its own if there is no additional\nwork pending in the event loop. The process.exitCode
property can be set to\ntell the process which exit code to use when the process exits gracefully.
For instance, the following example illustrates a misuse of the\nprocess.exit()
method that could lead to data printed to stdout being\ntruncated and lost:
import { exit } from 'node:process';\n\n// This is an example of what *not* to do:\nif (someConditionNotMet()) {\n printUsageToStdout();\n exit(1);\n}\n
\nconst { exit } = require('node:process');\n\n// This is an example of what *not* to do:\nif (someConditionNotMet()) {\n printUsageToStdout();\n exit(1);\n}\n
\nThe reason this is problematic is because writes to process.stdout
in Node.js\nare sometimes asynchronous and may occur over multiple ticks of the Node.js\nevent loop. Calling process.exit()
, however, forces the process to exit\nbefore those additional writes to stdout
can be performed.
Rather than calling process.exit()
directly, the code should set the\nprocess.exitCode
and allow the process to exit naturally by avoiding\nscheduling any additional work for the event loop:
import process from 'node:process';\n\n// How to properly set the exit code while letting\n// the process exit gracefully.\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exitCode = 1;\n}\n
\nconst process = require('node:process');\n\n// How to properly set the exit code while letting\n// the process exit gracefully.\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exitCode = 1;\n}\n
\nIf it is necessary to terminate the Node.js process due to an error condition,\nthrowing an uncaught error and allowing the process to terminate accordingly\nis safer than calling process.exit()
.
In Worker
threads, this function stops the current thread rather\nthan the current process.
The process.getActiveResourcesInfo()
method returns an array of strings\ncontaining the types of the active resources that are currently keeping the\nevent loop alive.
import { getActiveResourcesInfo } from 'node:process';\nimport { setTimeout } from 'node:timers';\n\nconsole.log('Before:', getActiveResourcesInfo());\nsetTimeout(() => {}, 1000);\nconsole.log('After:', getActiveResourcesInfo());\n// Prints:\n// Before: [ 'CloseReq', 'TTYWrap', 'TTYWrap', 'TTYWrap' ]\n// After: [ 'CloseReq', 'TTYWrap', 'TTYWrap', 'TTYWrap', 'Timeout' ]\n
\nconst { getActiveResourcesInfo } = require('node:process');\nconst { setTimeout } = require('node:timers');\n\nconsole.log('Before:', getActiveResourcesInfo());\nsetTimeout(() => {}, 1000);\nconsole.log('After:', getActiveResourcesInfo());\n// Prints:\n// Before: [ 'TTYWrap', 'TTYWrap', 'TTYWrap' ]\n// After: [ 'TTYWrap', 'TTYWrap', 'TTYWrap', 'Timeout' ]\n
"
},
{
"textRaw": "`process.getegid()`",
"type": "method",
"name": "getegid",
"meta": {
"added": [
"v2.0.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "The process.getegid()
method returns the numerical effective group identity\nof the Node.js process. (See getegid(2)
.)
import process from 'node:process';\n\nif (process.getegid) {\n console.log(`Current gid: ${process.getegid()}`);\n}\n
\nconst process = require('node:process');\n\nif (process.getegid) {\n console.log(`Current gid: ${process.getegid()}`);\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "`process.geteuid()`", "type": "method", "name": "geteuid", "meta": { "added": [ "v2.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "The process.geteuid()
method returns the numerical effective user identity of\nthe process. (See geteuid(2)
.)
import process from 'node:process';\n\nif (process.geteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n}\n
\nconst process = require('node:process');\n\nif (process.geteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "`process.getgid()`", "type": "method", "name": "getgid", "meta": { "added": [ "v0.1.31" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "The process.getgid()
method returns the numerical group identity of the\nprocess. (See getgid(2)
.)
import process from 'node:process';\n\nif (process.getgid) {\n console.log(`Current gid: ${process.getgid()}`);\n}\n
\nconst process = require('node:process');\n\nif (process.getgid) {\n console.log(`Current gid: ${process.getgid()}`);\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "`process.getgroups()`", "type": "method", "name": "getgroups", "meta": { "added": [ "v0.9.4" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer\\[]}", "name": "return", "type": "integer\\[]" }, "params": [] } ], "desc": "The process.getgroups()
method returns an array with the supplementary group\nIDs. POSIX leaves it unspecified if the effective group ID is included but\nNode.js ensures it always is.
import process from 'node:process';\n\nif (process.getgroups) {\n console.log(process.getgroups()); // [ 16, 21, 297 ]\n}\n
\nconst process = require('node:process');\n\nif (process.getgroups) {\n console.log(process.getgroups()); // [ 16, 21, 297 ]\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "`process.getuid()`", "type": "method", "name": "getuid", "meta": { "added": [ "v0.1.28" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer}", "name": "return", "type": "integer" }, "params": [] } ], "desc": "The process.getuid()
method returns the numeric user identity of the process.\n(See getuid(2)
.)
import process from 'node:process';\n\nif (process.getuid) {\n console.log(`Current uid: ${process.getuid()}`);\n}\n
\nconst process = require('node:process');\n\nif (process.getuid) {\n console.log(`Current uid: ${process.getuid()}`);\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "`process.hasUncaughtExceptionCaptureCallback()`", "type": "method", "name": "hasUncaughtExceptionCaptureCallback", "meta": { "added": [ "v9.3.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [] } ], "desc": "Indicates whether a callback has been set using\nprocess.setUncaughtExceptionCaptureCallback()
.
This is the legacy version of process.hrtime.bigint()
\nbefore bigint
was introduced in JavaScript.
The process.hrtime()
method returns the current high-resolution real time\nin a [seconds, nanoseconds]
tuple Array
, where nanoseconds
is the\nremaining part of the real time that can't be represented in second precision.
time
is an optional parameter that must be the result of a previous\nprocess.hrtime()
call to diff with the current time. If the parameter\npassed in is not a tuple Array
, a TypeError
will be thrown. Passing in a\nuser-defined array instead of the result of a previous call to\nprocess.hrtime()
will lead to undefined behavior.
These times are relative to an arbitrary time in the\npast, and not related to the time of day and therefore not subject to clock\ndrift. The primary use is for measuring performance between intervals:
\nimport { hrtime } from 'node:process';\n\nconst NS_PER_SEC = 1e9;\nconst time = hrtime();\n// [ 1800216, 25 ]\n\nsetTimeout(() => {\n const diff = hrtime(time);\n // [ 1, 552 ]\n\n console.log(`Benchmark took ${diff[0] * NS_PER_SEC + diff[1]} nanoseconds`);\n // Benchmark took 1000000552 nanoseconds\n}, 1000);\n
\nconst { hrtime } = require('node:process');\n\nconst NS_PER_SEC = 1e9;\nconst time = hrtime();\n// [ 1800216, 25 ]\n\nsetTimeout(() => {\n const diff = hrtime(time);\n // [ 1, 552 ]\n\n console.log(`Benchmark took ${diff[0] * NS_PER_SEC + diff[1]} nanoseconds`);\n // Benchmark took 1000000552 nanoseconds\n}, 1000);\n
"
},
{
"textRaw": "`process.hrtime.bigint()`",
"type": "method",
"name": "bigint",
"meta": {
"added": [
"v10.7.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {bigint}",
"name": "return",
"type": "bigint"
},
"params": []
}
],
"desc": "The bigint
version of the process.hrtime()
method returning the\ncurrent high-resolution real time in nanoseconds as a bigint
.
Unlike process.hrtime()
, it does not support an additional time
\nargument since the difference can just be computed directly\nby subtraction of the two bigint
s.
import { hrtime } from 'node:process';\n\nconst start = hrtime.bigint();\n// 191051479007711n\n\nsetTimeout(() => {\n const end = hrtime.bigint();\n // 191052633396993n\n\n console.log(`Benchmark took ${end - start} nanoseconds`);\n // Benchmark took 1154389282 nanoseconds\n}, 1000);\n
\nconst { hrtime } = require('node:process');\n\nconst start = hrtime.bigint();\n// 191051479007711n\n\nsetTimeout(() => {\n const end = hrtime.bigint();\n // 191052633396993n\n\n console.log(`Benchmark took ${end - start} nanoseconds`);\n // Benchmark took 1154389282 nanoseconds\n}, 1000);\n
"
},
{
"textRaw": "`process.initgroups(user, extraGroup)`",
"type": "method",
"name": "initgroups",
"meta": {
"added": [
"v0.9.4"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`user` {string|number} The user name or numeric identifier.",
"name": "user",
"type": "string|number",
"desc": "The user name or numeric identifier."
},
{
"textRaw": "`extraGroup` {string|number} A group name or numeric identifier.",
"name": "extraGroup",
"type": "string|number",
"desc": "A group name or numeric identifier."
}
]
}
],
"desc": "The process.initgroups()
method reads the /etc/group
file and initializes\nthe group access list, using all groups of which the user is a member. This is\na privileged operation that requires that the Node.js process either have root
\naccess or the CAP_SETGID
capability.
Use care when dropping privileges:
\nimport { getgroups, initgroups, setgid } from 'node:process';\n\nconsole.log(getgroups()); // [ 0 ]\ninitgroups('nodeuser', 1000); // switch user\nconsole.log(getgroups()); // [ 27, 30, 46, 1000, 0 ]\nsetgid(1000); // drop root gid\nconsole.log(getgroups()); // [ 27, 30, 46, 1000 ]\n
\nconst { getgroups, initgroups, setgid } = require('node:process');\n\nconsole.log(getgroups()); // [ 0 ]\ninitgroups('nodeuser', 1000); // switch user\nconsole.log(getgroups()); // [ 27, 30, 46, 1000, 0 ]\nsetgid(1000); // drop root gid\nconsole.log(getgroups()); // [ 27, 30, 46, 1000 ]\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker
threads.
The process.kill()
method sends the signal
to the process identified by\npid
.
Signal names are strings such as 'SIGINT'
or 'SIGHUP'
. See Signal Events\nand kill(2)
for more information.
This method will throw an error if the target pid
does not exist. As a special\ncase, a signal of 0
can be used to test for the existence of a process.\nWindows platforms will throw an error if the pid
is used to kill a process\ngroup.
Even though the name of this function is process.kill()
, it is really just a\nsignal sender, like the kill
system call. The signal sent may do something\nother than kill the target process.
import process, { kill } from 'node:process';\n\nprocess.on('SIGHUP', () => {\n console.log('Got SIGHUP signal.');\n});\n\nsetTimeout(() => {\n console.log('Exiting.');\n process.exit(0);\n}, 100);\n\nkill(process.pid, 'SIGHUP');\n
\nconst process = require('node:process');\n\nprocess.on('SIGHUP', () => {\n console.log('Got SIGHUP signal.');\n});\n\nsetTimeout(() => {\n console.log('Exiting.');\n process.exit(0);\n}, 100);\n\nprocess.kill(process.pid, 'SIGHUP');\n
\nWhen SIGUSR1
is received by a Node.js process, Node.js will start the\ndebugger. See Signal Events.
Loads the .env
file into process.env
. Usage of NODE_OPTIONS
\nin the .env
file will not have any effect on Node.js.
const { loadEnvFile } = require('node:process');\nloadEnvFile();\n
\nimport { loadEnvFile } from 'node:process';\nloadEnvFile();\n
"
},
{
"textRaw": "`process.memoryUsage()`",
"type": "method",
"name": "memoryUsage",
"meta": {
"added": [
"v0.1.16"
],
"changes": [
{
"version": [
"v13.9.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/31550",
"description": "Added `arrayBuffers` to the returned object."
},
{
"version": "v7.2.0",
"pr-url": "https://github.com/nodejs/node/pull/9587",
"description": "Added `external` to the returned object."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object",
"options": [
{
"textRaw": "`rss` {integer}",
"name": "rss",
"type": "integer"
},
{
"textRaw": "`heapTotal` {integer}",
"name": "heapTotal",
"type": "integer"
},
{
"textRaw": "`heapUsed` {integer}",
"name": "heapUsed",
"type": "integer"
},
{
"textRaw": "`external` {integer}",
"name": "external",
"type": "integer"
},
{
"textRaw": "`arrayBuffers` {integer}",
"name": "arrayBuffers",
"type": "integer"
}
]
},
"params": []
}
],
"desc": "Returns an object describing the memory usage of the Node.js process measured in\nbytes.
\nimport { memoryUsage } from 'node:process';\n\nconsole.log(memoryUsage());\n// Prints:\n// {\n// rss: 4935680,\n// heapTotal: 1826816,\n// heapUsed: 650472,\n// external: 49879,\n// arrayBuffers: 9386\n// }\n
\nconst { memoryUsage } = require('node:process');\n\nconsole.log(memoryUsage());\n// Prints:\n// {\n// rss: 4935680,\n// heapTotal: 1826816,\n// heapUsed: 650472,\n// external: 49879,\n// arrayBuffers: 9386\n// }\n
\nheapTotal
and heapUsed
refer to V8's memory usage.external
refers to the memory usage of C++ objects bound to JavaScript\nobjects managed by V8.rss
, Resident Set Size, is the amount of space occupied in the main\nmemory device (that is a subset of the total allocated memory) for the\nprocess, including all C++ and JavaScript objects and code.arrayBuffers
refers to memory allocated for ArrayBuffer
s and\nSharedArrayBuffer
s, including all Node.js Buffer
s.\nThis is also included in the external
value. When Node.js is used as an\nembedded library, this value may be 0
because allocations for ArrayBuffer
s\nmay not be tracked in that case.When using Worker
threads, rss
will be a value that is valid for the\nentire process, while the other fields will only refer to the current thread.
The process.memoryUsage()
method iterates over each page to gather\ninformation about memory usage which might be slow depending on the\nprogram memory allocations.
The process.memoryUsage.rss()
method returns an integer representing the\nResident Set Size (RSS) in bytes.
The Resident Set Size, is the amount of space occupied in the main\nmemory device (that is a subset of the total allocated memory) for the\nprocess, including all C++ and JavaScript objects and code.
\nThis is the same value as the rss
property provided by process.memoryUsage()
\nbut process.memoryUsage.rss()
is faster.
import { memoryUsage } from 'node:process';\n\nconsole.log(memoryUsage.rss());\n// 35655680\n
\nconst { memoryUsage } = require('node:process');\n\nconsole.log(memoryUsage.rss());\n// 35655680\n
"
},
{
"textRaw": "`process.nextTick(callback[, ...args])`",
"type": "method",
"name": "nextTick",
"meta": {
"added": [
"v0.1.26"
],
"changes": [
{
"version": "v18.0.0",
"pr-url": "https://github.com/nodejs/node/pull/41678",
"description": "Passing an invalid callback to the `callback` argument now throws `ERR_INVALID_ARG_TYPE` instead of `ERR_INVALID_CALLBACK`."
},
{
"version": "v1.8.1",
"pr-url": "https://github.com/nodejs/node/pull/1077",
"description": "Additional arguments after `callback` are now supported."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
},
{
"textRaw": "`...args` {any} Additional arguments to pass when invoking the `callback`",
"name": "...args",
"type": "any",
"desc": "Additional arguments to pass when invoking the `callback`"
}
]
}
],
"desc": "process.nextTick()
adds callback
to the \"next tick queue\". This queue is\nfully drained after the current operation on the JavaScript stack runs to\ncompletion and before the event loop is allowed to continue. It's possible to\ncreate an infinite loop if one were to recursively call process.nextTick()
.\nSee the Event Loop guide for more background.
import { nextTick } from 'node:process';\n\nconsole.log('start');\nnextTick(() => {\n console.log('nextTick callback');\n});\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// nextTick callback\n
\nconst { nextTick } = require('node:process');\n\nconsole.log('start');\nnextTick(() => {\n console.log('nextTick callback');\n});\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// nextTick callback\n
\nThis is important when developing APIs in order to give users the opportunity\nto assign event handlers after an object has been constructed but before any\nI/O has occurred:
\nimport { nextTick } from 'node:process';\n\nfunction MyThing(options) {\n this.setupOptions(options);\n\n nextTick(() => {\n this.startDoingStuff();\n });\n}\n\nconst thing = new MyThing();\nthing.getReadyForStuff();\n\n// thing.startDoingStuff() gets called now, not before.\n
\nconst { nextTick } = require('node:process');\n\nfunction MyThing(options) {\n this.setupOptions(options);\n\n nextTick(() => {\n this.startDoingStuff();\n });\n}\n\nconst thing = new MyThing();\nthing.getReadyForStuff();\n\n// thing.startDoingStuff() gets called now, not before.\n
\nIt is very important for APIs to be either 100% synchronous or 100%\nasynchronous. Consider this example:
\n// WARNING! DO NOT USE! BAD UNSAFE HAZARD!\nfunction maybeSync(arg, cb) {\n if (arg) {\n cb();\n return;\n }\n\n fs.stat('file', cb);\n}\n
\nThis API is hazardous because in the following case:
\nconst maybeTrue = Math.random() > 0.5;\n\nmaybeSync(maybeTrue, () => {\n foo();\n});\n\nbar();\n
\nIt is not clear whether foo()
or bar()
will be called first.
The following approach is much better:
\nimport { nextTick } from 'node:process';\n\nfunction definitelyAsync(arg, cb) {\n if (arg) {\n nextTick(cb);\n return;\n }\n\n fs.stat('file', cb);\n}\n
\nconst { nextTick } = require('node:process');\n\nfunction definitelyAsync(arg, cb) {\n if (arg) {\n nextTick(cb);\n return;\n }\n\n fs.stat('file', cb);\n}\n
",
"modules": [
{
"textRaw": "When to use `queueMicrotask()` vs. `process.nextTick()`",
"name": "when_to_use_`queuemicrotask()`_vs._`process.nexttick()`",
"desc": "The queueMicrotask()
API is an alternative to process.nextTick()
that\nalso defers execution of a function using the same microtask queue used to\nexecute the then, catch, and finally handlers of resolved promises. Within\nNode.js, every time the \"next tick queue\" is drained, the microtask queue\nis drained immediately after.
import { nextTick } from 'node:process';\n\nPromise.resolve().then(() => console.log(2));\nqueueMicrotask(() => console.log(3));\nnextTick(() => console.log(1));\n// Output:\n// 1\n// 2\n// 3\n
\nconst { nextTick } = require('node:process');\n\nPromise.resolve().then(() => console.log(2));\nqueueMicrotask(() => console.log(3));\nnextTick(() => console.log(1));\n// Output:\n// 1\n// 2\n// 3\n
\nFor most userland use cases, the queueMicrotask()
API provides a portable\nand reliable mechanism for deferring execution that works across multiple\nJavaScript platform environments and should be favored over process.nextTick()
.\nIn simple scenarios, queueMicrotask()
can be a drop-in replacement for\nprocess.nextTick()
.
console.log('start');\nqueueMicrotask(() => {\n console.log('microtask callback');\n});\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// microtask callback\n
\nOne note-worthy difference between the two APIs is that process.nextTick()
\nallows specifying additional values that will be passed as arguments to the\ndeferred function when it is called. Achieving the same result with\nqueueMicrotask()
requires using either a closure or a bound function:
function deferred(a, b) {\n console.log('microtask', a + b);\n}\n\nconsole.log('start');\nqueueMicrotask(deferred.bind(undefined, 1, 2));\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// microtask 3\n
\nThere are minor differences in the way errors raised from within the next tick\nqueue and microtask queue are handled. Errors thrown within a queued microtask\ncallback should be handled within the queued callback when possible. If they are\nnot, the process.on('uncaughtException')
event handler can be used to capture\nand handle the errors.
When in doubt, unless the specific capabilities of process.nextTick()
are\nneeded, use queueMicrotask()
.
import { resourceUsage } from 'node:process';\n\nconsole.log(resourceUsage());\n/*\n Will output:\n {\n userCPUTime: 82872,\n systemCPUTime: 4143,\n maxRSS: 33164,\n sharedMemorySize: 0,\n unsharedDataSize: 0,\n unsharedStackSize: 0,\n minorPageFault: 2469,\n majorPageFault: 0,\n swappedOut: 0,\n fsRead: 0,\n fsWrite: 8,\n ipcSent: 0,\n ipcReceived: 0,\n signalsCount: 0,\n voluntaryContextSwitches: 79,\n involuntaryContextSwitches: 1\n }\n*/\n
\nconst { resourceUsage } = require('node:process');\n\nconsole.log(resourceUsage());\n/*\n Will output:\n {\n userCPUTime: 82872,\n systemCPUTime: 4143,\n maxRSS: 33164,\n sharedMemorySize: 0,\n unsharedDataSize: 0,\n unsharedStackSize: 0,\n minorPageFault: 2469,\n majorPageFault: 0,\n swappedOut: 0,\n fsRead: 0,\n fsWrite: 8,\n ipcSent: 0,\n ipcReceived: 0,\n signalsCount: 0,\n voluntaryContextSwitches: 79,\n involuntaryContextSwitches: 1\n }\n*/\n
"
},
{
"textRaw": "`process.send(message[, sendHandle[, options]][, callback])`",
"type": "method",
"name": "send",
"meta": {
"added": [
"v0.5.9"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`message` {Object}",
"name": "message",
"type": "Object"
},
{
"textRaw": "`sendHandle` {net.Server|net.Socket}",
"name": "sendHandle",
"type": "net.Server|net.Socket"
},
{
"textRaw": "`options` {Object} used to parameterize the sending of certain types of handles.`options` supports the following properties:",
"name": "options",
"type": "Object",
"desc": "used to parameterize the sending of certain types of handles.`options` supports the following properties:",
"options": [
{
"textRaw": "`keepOpen` {boolean} A value that can be used when passing instances of `net.Socket`. When `true`, the socket is kept open in the sending process. **Default:** `false`.",
"name": "keepOpen",
"type": "boolean",
"default": "`false`",
"desc": "A value that can be used when passing instances of `net.Socket`. When `true`, the socket is kept open in the sending process."
}
]
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function"
}
]
}
],
"desc": "If Node.js is spawned with an IPC channel, the process.send()
method can be\nused to send messages to the parent process. Messages will be received as a\n'message'
event on the parent's ChildProcess
object.
If Node.js was not spawned with an IPC channel, process.send
will be\nundefined
.
The message goes through serialization and parsing. The resulting message might\nnot be the same as what is originally sent.
" }, { "textRaw": "`process.setegid(id)`", "type": "method", "name": "setegid", "meta": { "added": [ "v2.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`id` {string|number} A group name or ID", "name": "id", "type": "string|number", "desc": "A group name or ID" } ] } ], "desc": "The process.setegid()
method sets the effective group identity of the process.\n(See setegid(2)
.) The id
can be passed as either a numeric ID or a group\nname string. If a group name is specified, this method blocks while resolving\nthe associated a numeric ID.
import process from 'node:process';\n\nif (process.getegid && process.setegid) {\n console.log(`Current gid: ${process.getegid()}`);\n try {\n process.setegid(501);\n console.log(`New gid: ${process.getegid()}`);\n } catch (err) {\n console.error(`Failed to set gid: ${err}`);\n }\n}\n
\nconst process = require('node:process');\n\nif (process.getegid && process.setegid) {\n console.log(`Current gid: ${process.getegid()}`);\n try {\n process.setegid(501);\n console.log(`New gid: ${process.getegid()}`);\n } catch (err) {\n console.error(`Failed to set gid: ${err}`);\n }\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker
threads.
The process.seteuid()
method sets the effective user identity of the process.\n(See seteuid(2)
.) The id
can be passed as either a numeric ID or a username\nstring. If a username is specified, the method blocks while resolving the\nassociated numeric ID.
import process from 'node:process';\n\nif (process.geteuid && process.seteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n try {\n process.seteuid(501);\n console.log(`New uid: ${process.geteuid()}`);\n } catch (err) {\n console.error(`Failed to set uid: ${err}`);\n }\n}\n
\nconst process = require('node:process');\n\nif (process.geteuid && process.seteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n try {\n process.seteuid(501);\n console.log(`New uid: ${process.geteuid()}`);\n } catch (err) {\n console.error(`Failed to set uid: ${err}`);\n }\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker
threads.
The process.setgid()
method sets the group identity of the process. (See\nsetgid(2)
.) The id
can be passed as either a numeric ID or a group name\nstring. If a group name is specified, this method blocks while resolving the\nassociated numeric ID.
import process from 'node:process';\n\nif (process.getgid && process.setgid) {\n console.log(`Current gid: ${process.getgid()}`);\n try {\n process.setgid(501);\n console.log(`New gid: ${process.getgid()}`);\n } catch (err) {\n console.error(`Failed to set gid: ${err}`);\n }\n}\n
\nconst process = require('node:process');\n\nif (process.getgid && process.setgid) {\n console.log(`Current gid: ${process.getgid()}`);\n try {\n process.setgid(501);\n console.log(`New gid: ${process.getgid()}`);\n } catch (err) {\n console.error(`Failed to set gid: ${err}`);\n }\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker
threads.
The process.setgroups()
method sets the supplementary group IDs for the\nNode.js process. This is a privileged operation that requires the Node.js\nprocess to have root
or the CAP_SETGID
capability.
The groups
array can contain numeric group IDs, group names, or both.
import process from 'node:process';\n\nif (process.getgroups && process.setgroups) {\n try {\n process.setgroups([501]);\n console.log(process.getgroups()); // new groups\n } catch (err) {\n console.error(`Failed to set groups: ${err}`);\n }\n}\n
\nconst process = require('node:process');\n\nif (process.getgroups && process.setgroups) {\n try {\n process.setgroups([501]);\n console.log(process.getgroups()); // new groups\n } catch (err) {\n console.error(`Failed to set groups: ${err}`);\n }\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker
threads.
The process.setuid(id)
method sets the user identity of the process. (See\nsetuid(2)
.) The id
can be passed as either a numeric ID or a username string.\nIf a username is specified, the method blocks while resolving the associated\nnumeric ID.
import process from 'node:process';\n\nif (process.getuid && process.setuid) {\n console.log(`Current uid: ${process.getuid()}`);\n try {\n process.setuid(501);\n console.log(`New uid: ${process.getuid()}`);\n } catch (err) {\n console.error(`Failed to set uid: ${err}`);\n }\n}\n
\nconst process = require('node:process');\n\nif (process.getuid && process.setuid) {\n console.log(`Current uid: ${process.getuid()}`);\n try {\n process.setuid(501);\n console.log(`New uid: ${process.getuid()}`);\n } catch (err) {\n console.error(`Failed to set uid: ${err}`);\n }\n}\n
\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker
threads.
This function enables or disables the Source Map v3 support for\nstack traces.
\nIt provides same features as launching Node.js process with commandline options\n--enable-source-maps
.
Only source maps in JavaScript files that are loaded after source maps has been\nenabled will be parsed and loaded.
" }, { "textRaw": "`process.setUncaughtExceptionCaptureCallback(fn)`", "type": "method", "name": "setUncaughtExceptionCaptureCallback", "meta": { "added": [ "v9.3.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`fn` {Function|null}", "name": "fn", "type": "Function|null" } ] } ], "desc": "The process.setUncaughtExceptionCaptureCallback()
function sets a function\nthat will be invoked when an uncaught exception occurs, which will receive the\nexception value itself as its first argument.
If such a function is set, the 'uncaughtException'
event will\nnot be emitted. If --abort-on-uncaught-exception
was passed from the\ncommand line or set through v8.setFlagsFromString()
, the process will\nnot abort. Actions configured to take place on exceptions such as report\ngenerations will be affected too
To unset the capture function,\nprocess.setUncaughtExceptionCaptureCallback(null)
may be used. Calling this\nmethod with a non-null
argument while another capture function is set will\nthrow an error.
Using this function is mutually exclusive with using the deprecated\ndomain
built-in module.
process.umask()
returns the Node.js process's file mode creation mask. Child\nprocesses inherit the mask from the parent process.
process.umask(mask)
sets the Node.js process's file mode creation mask. Child\nprocesses inherit the mask from the parent process. Returns the previous mask.
import { umask } from 'node:process';\n\nconst newmask = 0o022;\nconst oldmask = umask(newmask);\nconsole.log(\n `Changed umask from ${oldmask.toString(8)} to ${newmask.toString(8)}`,\n);\n
\nconst { umask } = require('node:process');\n\nconst newmask = 0o022;\nconst oldmask = umask(newmask);\nconsole.log(\n `Changed umask from ${oldmask.toString(8)} to ${newmask.toString(8)}`,\n);\n
\nIn Worker
threads, process.umask(mask)
will throw an exception.
The process.uptime()
method returns the number of seconds the current Node.js\nprocess has been running.
The return value includes fractions of a second. Use Math.floor()
to get whole\nseconds.
The process.allowedNodeEnvironmentFlags
property is a special,\nread-only Set
of flags allowable within the NODE_OPTIONS
\nenvironment variable.
process.allowedNodeEnvironmentFlags
extends Set
, but overrides\nSet.prototype.has
to recognize several different possible flag\nrepresentations. process.allowedNodeEnvironmentFlags.has()
will\nreturn true
in the following cases:
-
) or double (--
) dashes; e.g.,\ninspect-brk
for --inspect-brk
, or r
for -r
.--v8-options
) may replace\none or more non-leading dashes for an underscore, or vice-versa;\ne.g., --perf_basic_prof
, --perf-basic-prof
, --perf_basic-prof
,\netc.=
) characters; all\ncharacters after and including the first equals will be ignored;\ne.g., --stack-trace-limit=100
.NODE_OPTIONS
.When iterating over process.allowedNodeEnvironmentFlags
, flags will\nappear only once; each will begin with one or more dashes. Flags\npassed through to V8 will contain underscores instead of non-leading\ndashes:
import { allowedNodeEnvironmentFlags } from 'node:process';\n\nallowedNodeEnvironmentFlags.forEach((flag) => {\n // -r\n // --inspect-brk\n // --abort_on_uncaught_exception\n // ...\n});\n
\nconst { allowedNodeEnvironmentFlags } = require('node:process');\n\nallowedNodeEnvironmentFlags.forEach((flag) => {\n // -r\n // --inspect-brk\n // --abort_on_uncaught_exception\n // ...\n});\n
\nThe methods add()
, clear()
, and delete()
of\nprocess.allowedNodeEnvironmentFlags
do nothing, and will fail\nsilently.
If Node.js was compiled without NODE_OPTIONS
support (shown in\nprocess.config
), process.allowedNodeEnvironmentFlags
will\ncontain what would have been allowable.
The operating system CPU architecture for which the Node.js binary was compiled.\nPossible values are: 'arm'
, 'arm64'
, 'ia32'
, 'loong64'
, 'mips'
,\n'mipsel'
, 'ppc'
, 'ppc64'
, 'riscv64'
, 's390'
, 's390x'
, and 'x64'
.
import { arch } from 'node:process';\n\nconsole.log(`This processor architecture is ${arch}`);\n
\nconst { arch } = require('node:process');\n\nconsole.log(`This processor architecture is ${arch}`);\n
"
},
{
"textRaw": "`argv` {string\\[]}",
"type": "string\\[]",
"name": "argv",
"meta": {
"added": [
"v0.1.27"
],
"changes": []
},
"desc": "The process.argv
property returns an array containing the command-line\narguments passed when the Node.js process was launched. The first element will\nbe process.execPath
. See process.argv0
if access to the original value\nof argv[0]
is needed. The second element will be the path to the JavaScript\nfile being executed. The remaining elements will be any additional command-line\narguments.
For example, assuming the following script for process-args.js
:
import { argv } from 'node:process';\n\n// print process.argv\nargv.forEach((val, index) => {\n console.log(`${index}: ${val}`);\n});\n
\nconst { argv } = require('node:process');\n\n// print process.argv\nargv.forEach((val, index) => {\n console.log(`${index}: ${val}`);\n});\n
\nLaunching the Node.js process as:
\nnode process-args.js one two=three four\n
\nWould generate the output:
\n0: /usr/local/bin/node\n1: /Users/mjr/work/node/process-args.js\n2: one\n3: two=three\n4: four\n
"
},
{
"textRaw": "`argv0` {string}",
"type": "string",
"name": "argv0",
"meta": {
"added": [
"v6.4.0"
],
"changes": []
},
"desc": "The process.argv0
property stores a read-only copy of the original value of\nargv[0]
passed when Node.js starts.
$ bash -c 'exec -a customArgv0 ./node'\n> process.argv[0]\n'/Volumes/code/external/node/out/Release/node'\n> process.argv0\n'customArgv0'\n
"
},
{
"textRaw": "`channel` {Object}",
"type": "Object",
"name": "channel",
"meta": {
"added": [
"v7.1.0"
],
"changes": [
{
"version": "v14.0.0",
"pr-url": "https://github.com/nodejs/node/pull/30165",
"description": "The object no longer accidentally exposes native C++ bindings."
}
]
},
"desc": "If the Node.js process was spawned with an IPC channel (see the\nChild Process documentation), the process.channel
\nproperty is a reference to the IPC channel. If no IPC channel exists, this\nproperty is undefined
.
This method makes the IPC channel keep the event loop of the process\nrunning if .unref()
has been called before.
Typically, this is managed through the number of 'disconnect'
and 'message'
\nlisteners on the process
object. However, this method can be used to\nexplicitly request a specific behavior.
This method makes the IPC channel not keep the event loop of the process\nrunning, and lets it finish even while the channel is open.
\nTypically, this is managed through the number of 'disconnect'
and 'message'
\nlisteners on the process
object. However, this method can be used to\nexplicitly request a specific behavior.
The process.config
property returns a frozen Object
containing the\nJavaScript representation of the configure options used to compile the current\nNode.js executable. This is the same as the config.gypi
file that was produced\nwhen running the ./configure
script.
An example of the possible output looks like:
\n\n{\n target_defaults:\n { cflags: [],\n default_configuration: 'Release',\n defines: [],\n include_dirs: [],\n libraries: [] },\n variables:\n {\n host_arch: 'x64',\n napi_build_version: 5,\n node_install_npm: 'true',\n node_prefix: '',\n node_shared_cares: 'false',\n node_shared_http_parser: 'false',\n node_shared_libuv: 'false',\n node_shared_zlib: 'false',\n node_use_openssl: 'true',\n node_shared_openssl: 'false',\n strict_aliasing: 'true',\n target_arch: 'x64',\n v8_use_snapshot: 1\n }\n}\n
"
},
{
"textRaw": "`connected` {boolean}",
"type": "boolean",
"name": "connected",
"meta": {
"added": [
"v0.7.2"
],
"changes": []
},
"desc": "If the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the process.connected
property will return\ntrue
so long as the IPC channel is connected and will return false
after\nprocess.disconnect()
is called.
Once process.connected
is false
, it is no longer possible to send messages\nover the IPC channel using process.send()
.
The port used by the Node.js debugger when enabled.
\nimport process from 'node:process';\n\nprocess.debugPort = 5858;\n
\nconst process = require('node:process');\n\nprocess.debugPort = 5858;\n
"
},
{
"textRaw": "`env` {Object}",
"type": "Object",
"name": "env",
"meta": {
"added": [
"v0.1.27"
],
"changes": [
{
"version": "v11.14.0",
"pr-url": "https://github.com/nodejs/node/pull/26544",
"description": "Worker threads will now use a copy of the parent thread's `process.env` by default, configurable through the `env` option of the `Worker` constructor."
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/18990",
"description": "Implicit conversion of variable value to string is deprecated."
}
]
},
"desc": "The process.env
property returns an object containing the user environment.\nSee environ(7)
.
An example of this object looks like:
\n\n{\n TERM: 'xterm-256color',\n SHELL: '/usr/local/bin/bash',\n USER: 'maciej',\n PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',\n PWD: '/Users/maciej',\n EDITOR: 'vim',\n SHLVL: '1',\n HOME: '/Users/maciej',\n LOGNAME: 'maciej',\n _: '/usr/local/bin/node'\n}\n
\nIt is possible to modify this object, but such modifications will not be\nreflected outside the Node.js process, or (unless explicitly requested)\nto other Worker
threads.\nIn other words, the following example would not work:
node -e 'process.env.foo = \"bar\"' && echo $foo\n
\nWhile the following will:
\nimport { env } from 'node:process';\n\nenv.foo = 'bar';\nconsole.log(env.foo);\n
\nconst { env } = require('node:process');\n\nenv.foo = 'bar';\nconsole.log(env.foo);\n
\nAssigning a property on process.env
will implicitly convert the value\nto a string. This behavior is deprecated. Future versions of Node.js may\nthrow an error when the value is not a string, number, or boolean.
import { env } from 'node:process';\n\nenv.test = null;\nconsole.log(env.test);\n// => 'null'\nenv.test = undefined;\nconsole.log(env.test);\n// => 'undefined'\n
\nconst { env } = require('node:process');\n\nenv.test = null;\nconsole.log(env.test);\n// => 'null'\nenv.test = undefined;\nconsole.log(env.test);\n// => 'undefined'\n
\nUse delete
to delete a property from process.env
.
import { env } from 'node:process';\n\nenv.TEST = 1;\ndelete env.TEST;\nconsole.log(env.TEST);\n// => undefined\n
\nconst { env } = require('node:process');\n\nenv.TEST = 1;\ndelete env.TEST;\nconsole.log(env.TEST);\n// => undefined\n
\nOn Windows operating systems, environment variables are case-insensitive.
\nimport { env } from 'node:process';\n\nenv.TEST = 1;\nconsole.log(env.test);\n// => 1\n
\nconst { env } = require('node:process');\n\nenv.TEST = 1;\nconsole.log(env.test);\n// => 1\n
\nUnless explicitly specified when creating a Worker
instance,\neach Worker
thread has its own copy of process.env
, based on its\nparent thread's process.env
, or whatever was specified as the env
option\nto the Worker
constructor. Changes to process.env
will not be visible\nacross Worker
threads, and only the main thread can make changes that\nare visible to the operating system or to native add-ons. On Windows, a copy of\nprocess.env
on a Worker
instance operates in a case-sensitive manner\nunlike the main thread.
The process.execArgv
property returns the set of Node.js-specific command-line\noptions passed when the Node.js process was launched. These options do not\nappear in the array returned by the process.argv
property, and do not\ninclude the Node.js executable, the name of the script, or any options following\nthe script name. These options are useful in order to spawn child processes with\nthe same execution environment as the parent.
node --harmony script.js --version\n
\nResults in process.execArgv
:
['--harmony']\n
\nAnd process.argv
:
['/usr/local/bin/node', 'script.js', '--version']\n
\nRefer to Worker
constructor for the detailed behavior of worker\nthreads with this property.
The process.execPath
property returns the absolute pathname of the executable\nthat started the Node.js process. Symbolic links, if any, are resolved.
'/usr/local/bin/node'\n
"
},
{
"textRaw": "`exitCode` {integer|string|null|undefined} The exit code. For string type, only integer strings (e.g.,'1') are allowed. **Default:** `undefined`.",
"type": "integer|string|null|undefined",
"name": "exitCode",
"meta": {
"added": [
"v0.11.8"
],
"changes": [
{
"version": "v20.0.0",
"pr-url": "https://github.com/nodejs/node/pull/43716",
"description": "Only accepts a code of type number, or of type string if it represents an integer."
}
]
},
"default": "`undefined`",
"desc": "A number which will be the process exit code, when the process either\nexits gracefully, or is exited via process.exit()
without specifying\na code.
Specifying a code to process.exit(code)
will override any\nprevious setting of process.exitCode
.
The process.mainModule
property provides an alternative way of retrieving\nrequire.main
. The difference is that if the main module changes at\nruntime, require.main
may still refer to the original main module in\nmodules that were required before the change occurred. Generally, it's\nsafe to assume that the two refer to the same module.
As with require.main
, process.mainModule
will be undefined
if there\nis no entry script.
The process.noDeprecation
property indicates whether the --no-deprecation
\nflag is set on the current Node.js process. See the documentation for\nthe 'warning'
event and the\nemitWarning()
method for more information about this\nflag's behavior.
This API is available through the --experimental-permission
flag.
process.permission
is an object whose methods are used to manage permissions\nfor the current process. Additional documentation is available in the\nPermission Model.
Verifies that the process is able to access the given scope and reference.\nIf no reference is provided, a global scope is assumed, for instance,\nprocess.permission.has('fs.read')
will check if the process has ALL\nfile system read permissions.
The reference has a meaning based on the provided scope. For example,\nthe reference when the scope is File System means files and folders.
\nThe available scopes are:
\nfs
- All File Systemfs.read
- File System read operationsfs.write
- File System write operationschild
- Child process spawning operationsworker
- Worker thread spawning operation// Check if the process has permission to read the README file\nprocess.permission.has('fs.read', './README.md');\n// Check if the process has read permission operations\nprocess.permission.has('fs.read');\n
"
}
]
},
{
"textRaw": "`pid` {integer}",
"type": "integer",
"name": "pid",
"meta": {
"added": [
"v0.1.15"
],
"changes": []
},
"desc": "The process.pid
property returns the PID of the process.
import { pid } from 'node:process';\n\nconsole.log(`This process is pid ${pid}`);\n
\nconst { pid } = require('node:process');\n\nconsole.log(`This process is pid ${pid}`);\n
"
},
{
"textRaw": "`platform` {string}",
"type": "string",
"name": "platform",
"meta": {
"added": [
"v0.1.16"
],
"changes": []
},
"desc": "The process.platform
property returns a string identifying the operating\nsystem platform for which the Node.js binary was compiled.
Currently possible values are:
\n'aix'
'darwin'
'freebsd'
'linux'
'openbsd'
'sunos'
'win32'
import { platform } from 'node:process';\n\nconsole.log(`This platform is ${platform}`);\n
\nconst { platform } = require('node:process');\n\nconsole.log(`This platform is ${platform}`);\n
\nThe value 'android'
may also be returned if the Node.js is built on the\nAndroid operating system. However, Android support in Node.js\nis experimental.
The process.ppid
property returns the PID of the parent of the\ncurrent process.
import { ppid } from 'node:process';\n\nconsole.log(`The parent process is pid ${ppid}`);\n
\nconst { ppid } = require('node:process');\n\nconsole.log(`The parent process is pid ${ppid}`);\n
"
},
{
"textRaw": "`release` {Object}",
"type": "Object",
"name": "release",
"meta": {
"added": [
"v3.0.0"
],
"changes": [
{
"version": "v4.2.0",
"pr-url": "https://github.com/nodejs/node/pull/3212",
"description": "The `lts` property is now supported."
}
]
},
"desc": "The process.release
property returns an Object
containing metadata related\nto the current release, including URLs for the source tarball and headers-only\ntarball.
process.release
contains the following properties:
name
<string> A value that will always be 'node'
.sourceUrl
<string> an absolute URL pointing to a .tar.gz
file containing\nthe source code of the current release.headersUrl
<string> an absolute URL pointing to a .tar.gz
file containing\nonly the source header files for the current release. This file is\nsignificantly smaller than the full source file and can be used for compiling\nNode.js native add-ons.libUrl
<string> | <undefined> an absolute URL pointing to a node.lib
file\nmatching the architecture and version of the current release. This file is\nused for compiling Node.js native add-ons. This property is only present on\nWindows builds of Node.js and will be missing on all other platforms.lts
<string> | <undefined> a string label identifying the LTS label for this\nrelease. This property only exists for LTS releases and is undefined
for all\nother release types, including Current releases. Valid values include the\nLTS Release code names (including those that are no longer supported).\n'Fermium'
for the 14.x LTS line beginning with 14.15.0.'Gallium'
for the 16.x LTS line beginning with 16.13.0.'Hydrogen'
for the 18.x LTS line beginning with 18.12.0.\nFor other LTS Release code names, see Node.js Changelog Archive{\n name: 'node',\n lts: 'Hydrogen',\n sourceUrl: 'https://nodejs.org/download/release/v18.12.0/node-v18.12.0.tar.gz',\n headersUrl: 'https://nodejs.org/download/release/v18.12.0/node-v18.12.0-headers.tar.gz',\n libUrl: 'https://nodejs.org/download/release/v18.12.0/win-x64/node.lib'\n}\n
\nIn custom builds from non-release versions of the source tree, only the\nname
property may be present. The additional properties should not be\nrelied upon to exist.
process.report
is an object whose methods are used to generate diagnostic\nreports for the current process. Additional documentation is available in the\nreport documentation.
Write reports in a compact format, single-line JSON, more easily consumable\nby log processing systems than the default multi-line format designed for\nhuman consumption.
\nimport { report } from 'node:process';\n\nconsole.log(`Reports are compact? ${report.compact}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Reports are compact? ${report.compact}`);\n
"
},
{
"textRaw": "`directory` {string}",
"type": "string",
"name": "directory",
"meta": {
"added": [
"v11.12.0"
],
"changes": [
{
"version": [
"v13.12.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32242",
"description": "This API is no longer experimental."
}
]
},
"desc": "Directory where the report is written. The default value is the empty string,\nindicating that reports are written to the current working directory of the\nNode.js process.
\nimport { report } from 'node:process';\n\nconsole.log(`Report directory is ${report.directory}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Report directory is ${report.directory}`);\n
"
},
{
"textRaw": "`filename` {string}",
"type": "string",
"name": "filename",
"meta": {
"added": [
"v11.12.0"
],
"changes": [
{
"version": [
"v13.12.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32242",
"description": "This API is no longer experimental."
}
]
},
"desc": "Filename where the report is written. If set to the empty string, the output\nfilename will be comprised of a timestamp, PID, and sequence number. The default\nvalue is the empty string.
\nIf the value of process.report.filename
is set to 'stdout'
or 'stderr'
,\nthe report is written to the stdout or stderr of the process respectively.
import { report } from 'node:process';\n\nconsole.log(`Report filename is ${report.filename}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Report filename is ${report.filename}`);\n
"
},
{
"textRaw": "`reportOnFatalError` {boolean}",
"type": "boolean",
"name": "reportOnFatalError",
"meta": {
"added": [
"v11.12.0"
],
"changes": [
{
"version": [
"v15.0.0",
"v14.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/35654",
"description": "This API is no longer experimental."
}
]
},
"desc": "If true
, a diagnostic report is generated on fatal errors, such as out of\nmemory errors or failed C++ assertions.
import { report } from 'node:process';\n\nconsole.log(`Report on fatal error: ${report.reportOnFatalError}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Report on fatal error: ${report.reportOnFatalError}`);\n
"
},
{
"textRaw": "`reportOnSignal` {boolean}",
"type": "boolean",
"name": "reportOnSignal",
"meta": {
"added": [
"v11.12.0"
],
"changes": [
{
"version": [
"v13.12.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32242",
"description": "This API is no longer experimental."
}
]
},
"desc": "If true
, a diagnostic report is generated when the process receives the\nsignal specified by process.report.signal
.
import { report } from 'node:process';\n\nconsole.log(`Report on signal: ${report.reportOnSignal}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Report on signal: ${report.reportOnSignal}`);\n
"
},
{
"textRaw": "`reportOnUncaughtException` {boolean}",
"type": "boolean",
"name": "reportOnUncaughtException",
"meta": {
"added": [
"v11.12.0"
],
"changes": [
{
"version": [
"v13.12.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32242",
"description": "This API is no longer experimental."
}
]
},
"desc": "If true
, a diagnostic report is generated on uncaught exception.
import { report } from 'node:process';\n\nconsole.log(`Report on exception: ${report.reportOnUncaughtException}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Report on exception: ${report.reportOnUncaughtException}`);\n
"
},
{
"textRaw": "`signal` {string}",
"type": "string",
"name": "signal",
"meta": {
"added": [
"v11.12.0"
],
"changes": [
{
"version": [
"v13.12.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32242",
"description": "This API is no longer experimental."
}
]
},
"desc": "The signal used to trigger the creation of a diagnostic report. Defaults to\n'SIGUSR2'
.
import { report } from 'node:process';\n\nconsole.log(`Report signal: ${report.signal}`);\n
\nconst { report } = require('node:process');\n\nconsole.log(`Report signal: ${report.signal}`);\n
"
}
],
"methods": [
{
"textRaw": "`process.report.getReport([err])`",
"type": "method",
"name": "getReport",
"meta": {
"added": [
"v11.8.0"
],
"changes": [
{
"version": [
"v13.12.0",
"v12.17.0"
],
"pr-url": "https://github.com/nodejs/node/pull/32242",
"description": "This API is no longer experimental."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Object}",
"name": "return",
"type": "Object"
},
"params": [
{
"textRaw": "`err` {Error} A custom error used for reporting the JavaScript stack.",
"name": "err",
"type": "Error",
"desc": "A custom error used for reporting the JavaScript stack."
}
]
}
],
"desc": "Returns a JavaScript Object representation of a diagnostic report for the\nrunning process. The report's JavaScript stack trace is taken from err
, if\npresent.
import { report } from 'node:process';\nimport util from 'node:util';\n\nconst data = report.getReport();\nconsole.log(data.header.nodejsVersion);\n\n// Similar to process.report.writeReport()\nimport fs from 'node:fs';\nfs.writeFileSync('my-report.log', util.inspect(data), 'utf8');\n
\nconst { report } = require('node:process');\nconst util = require('node:util');\n\nconst data = report.getReport();\nconsole.log(data.header.nodejsVersion);\n\n// Similar to process.report.writeReport()\nconst fs = require('node:fs');\nfs.writeFileSync('my-report.log', util.inspect(data), 'utf8');\n
\nAdditional documentation is available in the report documentation.
" }, { "textRaw": "`process.report.writeReport([filename][, err])`", "type": "method", "name": "writeReport", "meta": { "added": [ "v11.8.0" ], "changes": [ { "version": [ "v13.12.0", "v12.17.0" ], "pr-url": "https://github.com/nodejs/node/pull/32242", "description": "This API is no longer experimental." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {string} Returns the filename of the generated report.", "name": "return", "type": "string", "desc": "Returns the filename of the generated report." }, "params": [ { "textRaw": "`filename` {string} Name of the file where the report is written. This should be a relative path, that will be appended to the directory specified in `process.report.directory`, or the current working directory of the Node.js process, if unspecified.", "name": "filename", "type": "string", "desc": "Name of the file where the report is written. This should be a relative path, that will be appended to the directory specified in `process.report.directory`, or the current working directory of the Node.js process, if unspecified." }, { "textRaw": "`err` {Error} A custom error used for reporting the JavaScript stack.", "name": "err", "type": "Error", "desc": "A custom error used for reporting the JavaScript stack." } ] } ], "desc": "Writes a diagnostic report to a file. If filename
is not provided, the default\nfilename includes the date, time, PID, and a sequence number. The report's\nJavaScript stack trace is taken from err
, if present.
If the value of filename
is set to 'stdout'
or 'stderr'
, the report is\nwritten to the stdout or stderr of the process respectively.
import { report } from 'node:process';\n\nreport.writeReport();\n
\nconst { report } = require('node:process');\n\nreport.writeReport();\n
\nAdditional documentation is available in the report documentation.
" } ] }, { "textRaw": "`sourceMapsEnabled` {boolean}", "type": "boolean", "name": "sourceMapsEnabled", "meta": { "added": [ "v20.7.0" ], "changes": [] }, "stability": 1, "stabilityText": "Experimental", "desc": "The process.sourceMapsEnabled
property returns whether the\nSource Map v3 support for stack traces is enabled.
The process.stderr
property returns a stream connected to\nstderr
(fd 2
). It is a net.Socket
(which is a Duplex\nstream) unless fd 2
refers to a file, in which case it is\na Writable stream.
process.stderr
differs from other Node.js streams in important ways. See\nnote on process I/O for more information.
This property refers to the value of underlying file descriptor of\nprocess.stderr
. The value is fixed at 2
. In Worker
threads,\nthis field does not exist.
The process.stdin
property returns a stream connected to\nstdin
(fd 0
). It is a net.Socket
(which is a Duplex\nstream) unless fd 0
refers to a file, in which case it is\na Readable stream.
For details of how to read from stdin
see readable.read()
.
As a Duplex stream, process.stdin
can also be used in \"old\" mode that\nis compatible with scripts written for Node.js prior to v0.10.\nFor more information see Stream compatibility.
In \"old\" streams mode the stdin
stream is paused by default, so one\nmust call process.stdin.resume()
to read from it. Note also that calling\nprocess.stdin.resume()
itself would switch stream to \"old\" mode.
This property refers to the value of underlying file descriptor of\nprocess.stdin
. The value is fixed at 0
. In Worker
threads,\nthis field does not exist.
The process.stdout
property returns a stream connected to\nstdout
(fd 1
). It is a net.Socket
(which is a Duplex\nstream) unless fd 1
refers to a file, in which case it is\na Writable stream.
For example, to copy process.stdin
to process.stdout
:
import { stdin, stdout } from 'node:process';\n\nstdin.pipe(stdout);\n
\nconst { stdin, stdout } = require('node:process');\n\nstdin.pipe(stdout);\n
\nprocess.stdout
differs from other Node.js streams in important ways. See\nnote on process I/O for more information.
This property refers to the value of underlying file descriptor of\nprocess.stdout
. The value is fixed at 1
. In Worker
threads,\nthis field does not exist.
process.stdout
and process.stderr
differ from other Node.js streams in\nimportant ways:
console.log()
and console.error()
,\nrespectively.These behaviors are partly for historical reasons, as changing them would\ncreate backward incompatibility, but they are also expected by some users.
\nSynchronous writes avoid problems such as output written with console.log()
or\nconsole.error()
being unexpectedly interleaved, or not written at all if\nprocess.exit()
is called before an asynchronous write completes. See\nprocess.exit()
for more information.
Warning: Synchronous writes block the event loop until the write has\ncompleted. This can be near instantaneous in the case of output to a file, but\nunder high system load, pipes that are not being read at the receiving end, or\nwith slow terminals or file systems, it's possible for the event loop to be\nblocked often enough and long enough to have severe negative performance\nimpacts. This may not be a problem when writing to an interactive terminal\nsession, but consider this particularly careful when doing production logging to\nthe process output streams.
\nTo check if a stream is connected to a TTY context, check the isTTY
\nproperty.
For instance:
\n$ node -p \"Boolean(process.stdin.isTTY)\"\ntrue\n$ echo \"foo\" | node -p \"Boolean(process.stdin.isTTY)\"\nfalse\n$ node -p \"Boolean(process.stdout.isTTY)\"\ntrue\n$ node -p \"Boolean(process.stdout.isTTY)\" | cat\nfalse\n
\nSee the TTY documentation for more information.
", "type": "module", "displayName": "A note on process I/O" } ] }, { "textRaw": "`throwDeprecation` {boolean}", "type": "boolean", "name": "throwDeprecation", "meta": { "added": [ "v0.9.12" ], "changes": [] }, "desc": "The initial value of process.throwDeprecation
indicates whether the\n--throw-deprecation
flag is set on the current Node.js process.\nprocess.throwDeprecation
is mutable, so whether or not deprecation\nwarnings result in errors may be altered at runtime. See the\ndocumentation for the 'warning'
event and the\nemitWarning()
method for more information.
$ node --throw-deprecation -p \"process.throwDeprecation\"\ntrue\n$ node -p \"process.throwDeprecation\"\nundefined\n$ node\n> process.emitWarning('test', 'DeprecationWarning');\nundefined\n> (node:26598) DeprecationWarning: test\n> process.throwDeprecation = true;\ntrue\n> process.emitWarning('test', 'DeprecationWarning');\nThrown:\n[DeprecationWarning: test] { name: 'DeprecationWarning' }\n
"
},
{
"textRaw": "`title` {string}",
"type": "string",
"name": "title",
"meta": {
"added": [
"v0.1.104"
],
"changes": []
},
"desc": "The process.title
property returns the current process title (i.e. returns\nthe current value of ps
). Assigning a new value to process.title
modifies\nthe current value of ps
.
When a new value is assigned, different platforms will impose different maximum\nlength restrictions on the title. Usually such restrictions are quite limited.\nFor instance, on Linux and macOS, process.title
is limited to the size of the\nbinary name plus the length of the command-line arguments because setting the\nprocess.title
overwrites the argv
memory of the process. Node.js v0.8\nallowed for longer process title strings by also overwriting the environ
\nmemory but that was potentially insecure and confusing in some (rather obscure)\ncases.
Assigning a value to process.title
might not result in an accurate label\nwithin process manager applications such as macOS Activity Monitor or Windows\nServices Manager.
The process.traceDeprecation
property indicates whether the\n--trace-deprecation
flag is set on the current Node.js process. See the\ndocumentation for the 'warning'
event and the\nemitWarning()
method for more information about this\nflag's behavior.
The process.version
property contains the Node.js version string.
import { version } from 'node:process';\n\nconsole.log(`Version: ${version}`);\n// Version: v14.8.0\n
\nconst { version } = require('node:process');\n\nconsole.log(`Version: ${version}`);\n// Version: v14.8.0\n
\nTo get the version string without the prepended v, use\nprocess.versions.node
.
The process.versions
property returns an object listing the version strings of\nNode.js and its dependencies. process.versions.modules
indicates the current\nABI version, which is increased whenever a C++ API changes. Node.js will refuse\nto load modules that were compiled against a different module ABI version.
import { versions } from 'node:process';\n\nconsole.log(versions);\n
\nconst { versions } = require('node:process');\n\nconsole.log(versions);\n
\nWill generate an object similar to:
\n{ node: '20.2.0',\n acorn: '8.8.2',\n ada: '2.4.0',\n ares: '1.19.0',\n base64: '0.5.0',\n brotli: '1.0.9',\n cjs_module_lexer: '1.2.2',\n cldr: '43.0',\n icu: '73.1',\n llhttp: '8.1.0',\n modules: '115',\n napi: '8',\n nghttp2: '1.52.0',\n nghttp3: '0.7.0',\n ngtcp2: '0.8.1',\n openssl: '3.0.8+quic',\n simdutf: '3.2.9',\n tz: '2023c',\n undici: '5.22.0',\n unicode: '15.0',\n uv: '1.44.2',\n uvwasi: '0.0.16',\n v8: '11.3.244.8-node.9',\n zlib: '1.2.13' }\n
"
}
],
"source": "doc/api/process.md"
}
],
"methods": [
{
"textRaw": "`atob(data)`",
"type": "method",
"name": "atob",
"meta": {
"added": [
"v16.0.0"
],
"changes": []
},
"stability": 3,
"stabilityText": "Legacy. Use `Buffer.from(data, 'base64')` instead.",
"signatures": [
{
"params": []
}
],
"desc": "Global alias for buffer.atob()
.
Global alias for buffer.btoa()
.
This variable may appear to be global but is not. See require()
.