{ "miscs": [ { "textRaw": "About this Documentation", "name": "About this Documentation", "introduced_in": "v0.10.0", "type": "misc", "desc": "
The goal of this documentation is to comprehensively explain the Node.js\nAPI, both from a reference as well as a conceptual point of view. Each\nsection describes a built-in module or high-level concept.
\nWhere appropriate, property types, method arguments, and the arguments\nprovided to event handlers are detailed in a list underneath the topic\nheading.
", "miscs": [ { "textRaw": "Contributing", "name": "contributing", "desc": "If errors are found in this documentation, please submit an issue\nor see the contributing guide for directions on how to submit a patch.
\nEvery file is generated based on the corresponding .md
file in the\ndoc/api/
folder in Node.js's source tree. The documentation is generated\nusing the tools/doc/generate.js
program. An HTML template is located at\ndoc/template.html
.
Throughout the documentation are indications of a section's\nstability. The Node.js API is still somewhat changing, and as it\nmatures, certain parts are more reliable than others. Some are so\nproven, and so relied upon, that they are unlikely to ever change at\nall. Others are brand new and experimental, or known to be hazardous\nand in the process of being redesigned.
\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. This feature is still under active development\nand subject to non-backward compatible changes or removal in any future\nversion. Use of the feature is not recommended in production environments.\nExperimental features are not subject to the Node.js Semantic Versioning\nmodel.
\n
\n\nStability: 2 - Stable. Compatibility with the npm ecosystem is a high\npriority.
\n
Caution must be used when making use of Experimental
features, particularly\nwithin modules that may be used as dependencies (or dependencies of\ndependencies) within a Node.js application. End users may not be aware that\nexperimental features are being used, and therefore may experience unexpected\nfailures or behavior changes when API modifications occur. To help avoid such\nsurprises, Experimental
features may require a command-line flag to\nexplicitly enable them, or may cause a process warning to be emitted.\nBy default, such warnings are printed to stderr
and may be handled by\nattaching a listener to the 'warning'
event.
Every .html
document has a corresponding .json
document presenting\nthe same information in a structured manner. This feature is\nexperimental, and added for the benefit of IDEs and other utilities that\nwish to do programmatic things with the documentation.
System calls like open(2)
and read(2)
define the interface between user programs\nand the underlying operating system. Node.js functions\nwhich simply wrap a syscall,\nlike fs.open()
, will document that. The docs link to the corresponding man\npages (short for manual pages) which describe how the syscalls work.
Most Unix syscalls have Windows equivalents, but behavior may differ on Windows\nrelative to Linux and macOS. For an example of the subtle ways in which it's\nsometimes impossible to replace Unix syscall semantics on Windows, see Node.js\nissue 4760.
", "type": "misc", "displayName": "Syscalls and man pages" } ] }, { "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 information about\ndifferent options and ways to run scripts with Node.js.
\nAn example of a web server written with Node.js which responds with\n'Hello, World!'
:
Commands displayed in this document are shown starting with $
or >
\nto replicate how they would appear in a user's terminal.\nDo not include the $
and >
characters. They are there to\nindicate the start of each command.
There are many tutorials and examples that follow this\nconvention: $
or >
for commands run as a regular user, and #
\nfor commands that should be executed as an administrator.
Lines that don’t start with $
or >
character are typically showing\nthe output of the previous command.
Firstly, make sure to have downloaded and installed Node.js.\nSee this guide for further install information.
\nNow, create an empty project folder called projects
, then navigate into it.\nThe project folder can be named based on the user's current project title, but\nthis example will use projects
as the project folder.
Linux and Mac:
\n$ mkdir ~/projects\n$ cd ~/projects\n
\nWindows CMD:
\n> mkdir %USERPROFILE%\\projects\n> cd %USERPROFILE%\\projects\n
\nWindows PowerShell:
\n> mkdir $env:USERPROFILE\\projects\n> cd $env:USERPROFILE\\projects\n
\nNext, create a new source file in the projects
\nfolder and call it hello-world.js
.
In Node.js it is considered good style to use\nhyphens (-
) or underscores (_
) to separate\nmultiple words in filenames.
Open hello-world.js
in any preferred text editor and\npaste in the following content:
const http = require('http');\n\nconst hostname = '127.0.0.1';\nconst port = 3000;\n\nconst server = http.createServer((req, res) => {\n res.statusCode = 200;\n res.setHeader('Content-Type', 'text/plain');\n res.end('Hello, World!\\n');\n});\n\nserver.listen(port, hostname, () => {\n console.log(`Server running at http://${hostname}:${port}/`);\n});\n
\nSave the file, go back to the terminal window enter the following command:
\n$ node hello-world.js\n
\nAn output like this should appear in the terminal to indicate Node.js\nserver is running:
\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.
Many of the examples in the documentation can be run similarly.
" }, { "textRaw": "C++ Addons", "name": "C++ Addons", "introduced_in": "v0.10.0", "type": "misc", "desc": "Node.js Addons are dynamically-linked shared objects, written in C++, that\ncan be loaded into Node.js using the require()
function, and used\njust as if they were an ordinary Node.js module. They are used primarily to\nprovide an interface between JavaScript running in Node.js and C/C++ libraries.
At the moment, the method for implementing Addons is rather complicated,\ninvolving knowledge of several components and APIs:
\nV8: the C++ library Node.js currently 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 filesystem, sockets, timers, and system events. libuv\nalso provides a pthreads-like threading abstraction that may be used to\npower more sophisticated asynchronous Addons that need to move beyond the\nstandard event loop. Addon authors are encouraged to think about how to\navoid blocking the event loop with I/O or other time-intensive tasks by\noff-loading work via libuv to non-blocking system operations, worker threads\nor a custom use of libuv's threads.
\nInternal Node.js libraries. Node.js itself exports a number of C++ APIs\nthat Addons can use — the most important of which is the\nnode::ObjectWrap
class.
Node.js includes a number of other statically linked libraries including\nOpenSSL. These other libraries are located in the deps/
directory in the\nNode.js source tree. Only the libuv, OpenSSL, V8 and zlib symbols are\npurposefully re-exported by Node.js and may be used to various extents by\nAddons.\nSee Linking to Node.js' own dependencies 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::NewStringType;\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\", NewStringType::kNormal).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
\nNote that all 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()
.
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()
. From the addon's perspective, this means\nthat it must 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:
\nv8::Persistent<v8::Object>
which will hold a weak\nreference to the addon's exports
object. The callback associated with the weak\nreference will then destroy the instance of the class.v8::Persistent<v8::Object>
is set to the exports
object.v8::External
, andv8::External
to all methods exposed to JavaScript by passing it\nto the v8::FunctionTemplate
constructor which creates the native-backed\nJavaScript functions. The v8::FunctionTemplate
constructor's third parameter\naccepts the v8::External
.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 AddonData(Isolate* isolate, Local<Object> exports):\n call_count(0) {\n // Link the existence of this object instance to the existence of exports.\n exports_.Reset(isolate, exports);\n exports_.SetWeak(this, DeleteMe, WeakCallbackType::kParameter);\n }\n\n ~AddonData() {\n if (!exports_.IsEmpty()) {\n // Reset the reference to avoid leaking data.\n exports_.ClearWeak();\n exports_.Reset();\n }\n }\n\n // Per-addon data.\n int call_count;\n\n private:\n // Method to call when \"exports\" is about to be garbage-collected.\n static void DeleteMe(const WeakCallbackInfo<AddonData>& info) {\n delete info.GetParameter();\n }\n\n // Weak handle to the \"exports\" object. An instance of this class will be\n // destroyed along with the exports object to which it is weakly bound.\n v8::Persistent<v8::Object> exports_;\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.\n AddonData* data = new AddonData(isolate, exports);\n // Wrap the data in a v8::External so we can pass it to the method we 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\", NewStringType::kNormal)\n .ToLocalChecked(),\n FunctionTemplate::New(isolate, Method, external)\n ->GetFunction(context).ToLocalChecked()).FromJust();\n}\n
",
"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
\nPlease see the examples below for further information or\nhttps://github.com/arturadib/node-qt for an example in production.
\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.
Note that while the bindings
package implementation is more sophisticated\nin how it locates Addon modules, it is essentially using a try-catch pattern\nsimilar 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 Node.js' own dependencies",
"name": "linking_to_node.js'_own_dependencies",
"desc": "Node.js uses a number of statically linked libraries such as V8, libuv and\nOpenSSL. All Addons are required to link to V8 and may link to any of the\nother dependencies as well. Typically, this is as simple as including\nthe appropriate #include <...>
statements (e.g. #include <v8.h>
) and\nnode-gyp
will locate the appropriate headers automatically. However, there\nare a few caveats to be aware 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, then\nonly 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 make direct use of the\nNode.js and V8 APIs for implementing Addons. It is important to understand\nthat the V8 API can, and has, changed dramatically from one V8 release to the\nnext (and one major Node.js release to the next). With each change, Addons may\nneed to be updated and recompiled in order to continue functioning. The Node.js\nrelease schedule is designed to minimize the frequency and impact of such\nchanges but there is little that Node.js can do currently to ensure stability\nof 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.
N-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 N-API are used.
\nCreating and maintaining an addon that benefits from the ABI stability\nprovided by N-API carries with it certain\nimplementation considerations.
\nTo use N-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 N-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, \"hello\", 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 the\nsection titled C/C++ Addons - N-API.
", "type": "misc", "displayName": "N-API" }, { "textRaw": "Addon examples", "name": "addon_examples", "desc": "Following are some example Addons intended to help developers get started. The\nexamples make use of 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::NewStringType;\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\",\n NewStringType::kNormal).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\",\n NewStringType::kNormal).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::NewStringType;\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\",\n NewStringType::kNormal).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
\nNote that this example uses a two-argument form of Init()
that receives\nthe full module
object as the second argument. This allows the Addon\nto completely overwrite exports
with a single function instead of\nadding the function as a property 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
\nNote that, in 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::NewStringType;\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\",\n NewStringType::kNormal).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::NewStringType;\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\", NewStringType::kNormal).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\", NewStringType::kNormal).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 static v8::Persistent<v8::Function> constructor;\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::NewStringType;\nusing v8::Number;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\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\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(\n isolate, \"MyObject\", NewStringType::kNormal).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 exports->Set(context, String::NewFromUtf8(\n isolate, \"MyObject\", NewStringType::kNormal).ToLocalChecked(),\n tpl->GetFunction(context).ToLocalChecked()).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 = Local<Function>::New(isolate, constructor);\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.
", "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::Persistent<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 v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Number;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<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(\n isolate, \"MyObject\", NewStringType::kNormal).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\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::Persistent<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 v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<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(\n isolate, \"MyObject\", NewStringType::kNormal).ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n Local<Context> context = isolate->GetCurrentContext();\n constructor.Reset(isolate, tpl->GetFunction(context).ToLocalChecked());\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"
},
{
"textRaw": "AtExit hooks",
"name": "atexit_hooks",
"desc": "An AtExit
hook is a function that is invoked after the Node.js event loop\nhas ended but before the JavaScript VM is terminated and Node.js shuts down.\nAtExit
hooks are registered using the node::AtExit
API.
callback
<void (*)(void*)>\nA pointer to the function to call at exit.args
<void*>\nA pointer to pass to the callback at exit.Registers exit hooks that run after the event loop has ended but before the VM\nis killed.
\nAtExit
takes two parameters: a pointer to a callback function to run at exit,\nand a pointer to untyped context data to be passed to that callback.
Callbacks are run in last-in first-out order.
\nThe following addon.cc
implements AtExit
:
// addon.cc\n#include <assert.h>\n#include <stdlib.h>\n#include <node.h>\n\nnamespace demo {\n\nusing node::AtExit;\nusing v8::HandleScope;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\n\nstatic char cookie[] = \"yum yum\";\nstatic int at_exit_cb1_called = 0;\nstatic int at_exit_cb2_called = 0;\n\nstatic void at_exit_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 at_exit_cb1_called++;\n}\n\nstatic void at_exit_cb2(void* arg) {\n assert(arg == static_cast<void*>(cookie));\n at_exit_cb2_called++;\n}\n\nstatic void sanity_check(void*) {\n assert(at_exit_cb1_called == 1);\n assert(at_exit_cb2_called == 2);\n}\n\nvoid init(Local<Object> exports) {\n AtExit(at_exit_cb2, cookie);\n AtExit(at_exit_cb2, cookie);\n AtExit(at_exit_cb1, exports->GetIsolate());\n AtExit(sanity_check);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, init)\n\n} // namespace demo\n
\nTest in JavaScript by running:
\n// test.js\nrequire('./build/Release/addon');\n
",
"type": "module",
"displayName": "void AtExit(callback, args)"
}
],
"type": "module",
"displayName": "AtExit hooks"
}
],
"type": "misc",
"displayName": "Addon examples"
}
]
},
{
"textRaw": "N-API",
"name": "N-API",
"introduced_in": "v7.10.0",
"type": "misc",
"stability": 2,
"stabilityText": "Stable",
"desc": "N-API (pronounced N as in the letter, followed by API)\nis an API for building native Addons. It is independent from\nthe underlying JavaScript runtime (ex 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 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\noutlined in the section titled C++ Addons.\nThe only difference is the set of APIs that are used by the native code.\nInstead of using the V8 or Native Abstractions for Node.js APIs,\nthe functions available in the N-API are used.
\nAPIs exposed by N-API are generally used to create and manipulate\nJavaScript values. Concepts and operations generally map to ideas specified\nin the ECMA262 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.The N-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\nnode-addon-api.\nThis wrapper provides an inlineable C++ API. Binaries built\nwith node-addon-api
will depend on the symbols for the N-API C-based\nfunctions exported by Node.js. node-addon-api
is a more\nefficient way to write code that calls N-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_crate_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\ndocs\nfor node-addon-api
.
Although N-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 make use exclusively of N-API 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 N-API.
", "type": "misc", "displayName": "Implications of ABI Stability" }, { "textRaw": "Usage", "name": "usage", "desc": "In order to use the N-API functions, include the file\nnode_api.h
\nwhich is 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 N-API, the version\ncan be specified explicitly when including the header:
#define NAPI_VERSION 3\n#include <node_api.h>\n
\nThis restricts the N-API surface to just the functionality that was available in\nthe specified (and earlier) versions.
\nSome of the N-API surface is considered experimental and requires explicit\nopt-in to access those APIs:
\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.
", "type": "misc", "displayName": "Usage" }, { "textRaw": "N-API Version Matrix", "name": "n-api_version_matrix", "desc": "\n | 1 | \n2 | \n3 | \n
---|---|---|---|
v4.x | \n\n | \n | \n |
v6.x | \n\n | \n | v6.14.2* | \n
v8.x | \nv8.0.0* | \nv8.10.0* | \n\n |
v9.x | \nv9.0.0* | \nv9.3.0* | \nv9.11.0* | \n
v10.x | \n\n | \n | v10.0.0 | \n
* Indicates that the N-API version was released as experimental
\nThe N-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 N-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 N-API. In the example below,\naddon.c
and addon.h
refer only to js_native_api.h
. This ensures that\naddon.c
can be reused to compile against either the Node.js implementation of\nN-API or any implementation of N-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\"\nnapi_value create_addon(napi_env env) {\n napi_value result;\n assert(napi_create_object(env, &result) == napi_ok);\n napi_value exported_function;\n assert(napi_create_function(env,\n \"doSomethingUseful\",\n NAPI_AUTO_LENGTH,\n DoSomethingUseful,\n NULL,\n &exported_function) == napi_ok);\n assert(napi_set_named_property(env,\n result,\n \"doSomethingUseful\",\n exported_function) == napi_ok);\n return result;\n}\n
\n// addon_node.c\n#include <node_api.h>\n\nstatic napi_value Init(napi_env env, napi_value exports) {\n return create_addon(env);\n}\n\nNAPI_MODULE(NODE_GYP_MODULE_NAME, Init)\n
",
"type": "misc",
"displayName": "N-API Version Matrix"
},
{
"textRaw": "Basic N-API Data Types",
"name": "basic_n-api_data_types",
"desc": "N-API exposes the following fundamental datatypes as abstractions that are\nconsumed by the various APIs. These APIs should be treated as opaque,\nintrospectable only with other N-API calls.
", "modules": [ { "textRaw": "napi_status", "name": "napi_status", "desc": "Integral status code indicating the success or failure of a N-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_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 N-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 N-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 N-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 N-API calls. Caching the napi_env
for the purpose of general reuse is\nnot allowed.
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", "stability": 1, "stabilityText": "Experimental", "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",
"stability": 1,
"stabilityText": "Experimental",
"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": "N-API Memory Management types",
"name": "n-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, N-API values are created within\nthe 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, N-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", "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", "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" } ], "type": "module", "displayName": "N-API Memory Management types" }, { "textRaw": "N-API Callback types", "name": "n-api_callback_types", "modules": [ { "textRaw": "napi_callback_info", "name": "napi_callback_info", "desc": "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", "desc": "Function pointer type for user-provided native functions which are to be\nexposed to JavaScript via N-API. Callback functions should satisfy the\nfollowing signature:
\ntypedef napi_value (*napi_callback)(napi_env, napi_callback_info);\n
",
"type": "module",
"displayName": "napi_callback"
},
{
"textRaw": "napi_finalize",
"name": "napi_finalize",
"desc": "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 with which it was associated with, has been garbage-collected. The user\nmust provide a function satisfying the following signature which would get\ncalled upon the object's collection. Currently, napi_finalize
can be used for\nfinding out when objects that have external data are collected.
typedef void (*napi_finalize)(napi_env env,\n void* finalize_data,\n void* finalize_hint);\n
",
"type": "module",
"displayName": "napi_finalize"
},
{
"textRaw": "napi_async_execute_callback",
"name": "napi_async_execute_callback",
"desc": "Function pointer used with functions that support asynchronous\noperations. Callback functions must statisfy the following signature:
\ntypedef void (*napi_async_execute_callback)(napi_env env, void* data);\n
\nImplementations of this type of function should avoid making any N-API calls\nthat could result in the execution of JavaScript or interaction with\nJavaScript objects. Most often, any code that needs to make N-API\ncalls should be made in napi_async_complete_callback
instead.
Function pointer used with functions that support asynchronous\noperations. Callback functions must statisfy the following signature:
\ntypedef void (*napi_async_complete_callback)(napi_env env,\n napi_status status,\n void* data);\n
",
"type": "module",
"displayName": "napi_async_complete_callback"
},
{
"textRaw": "napi_threadsafe_function_call_js",
"name": "napi_threadsafe_function_call_js",
"stability": 1,
"stabilityText": "Experimental",
"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.
N-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.[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 N-API\nfunctions) that can be passed as parameters when js_callback
is invoked. This\npointer is managed entirely by the threads and this callback. Thus this callback\nshould free the data.N-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", "desc": "All of the N-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
: n-api status code for the last error.napi_get_last_error_info
returns the information for the last\nN-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(napi_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\nan n-api function is called on the same env
.
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 N-API function call may result in a pending JavaScript exception. This is\nobviously the case for any function that may cause the execution of\nJavaScript, but N-API specifies that an exception may be pending\non return from any of the API functions.
\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.
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 N-API calls\nis unspecified while an exception is pending, and many will simply return\nnapi_pending_exception
, so it is important to do as little as possible\nand then return to JavaScript 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 Error
object 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
and\nnapi_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
, and napi_create_range_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 N-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\nthe 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\nthe 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\nthe error.Returns napi_ok
if the API succeeded.
This API throws a JavaScript RangeError
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\nbe associated with the error.[in] msg
: napi_value
that references a JavaScript String
to be\nused as the 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\nbe associated with the error.[in] msg
: napi_value
that references a JavaScript String
to be\nused as the 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\nbe associated with the error.[in] msg
: napi_value
that references a JavaScript String
to be\nused as the 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_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 returns true if an exception is pending.
\nThis 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 returns true if an exception is pending.
\nThis 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 module, 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\nNAPI_AUTO_LENGTH
if it is\nnull-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 N-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 N-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, N-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
.
N-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. N-API supports an\n'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 open 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 open 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\nObject
in 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 objects with a lifespan longer than that of the native method", "name": "references_to_objects_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 objects\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 creates 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.
N-API provides methods to create persistent references to an object.\nEach persistent reference has an associated count with a value of 0\nor higher. The count determines if the reference will keep\nthe corresponding object live. References with a count of 0 do not\nprevent the object from being collected and are often called 'weak'\nreferences. Any count greater than 0 will prevent the object\nfrom being collected.
\nReferences 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\nwill result 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 will result 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.
", "modules": [ { "textRaw": "napi_create_reference", "name": "napi_create_reference", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_create_reference(napi_env env,\n napi_value value,\n int initial_refcount,\n napi_ref* result);\n
\n[in] env
: The environment that the API is invoked under.[in] value
: napi_value
representing the Object
to which we want\na reference.[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 create a new reference with the specified reference count\nto the Object
passed in.
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 int* 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 int* 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
\nthe napi_value passed
in or out of these methods is a handle to the\nobject to which the reference is related.
[in] env
: The environment that the API is invoked under.[in] ref
: napi_ref
for which we requesting the corresponding Object
.[out] result
: The napi_value
for the Object
referenced by the\nnapi_ref
.Returns napi_ok
if the API succeeded.
If still valid, this API returns the napi_value
representing the\nJavaScript Object
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 instance exits.
\nN-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(napi_env env,\n void (*fun)(void* arg),\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.
NAPI_EXTERN napi_status napi_remove_env_cleanup_hook(napi_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.
N-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 N-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. N-API modules cannot modify the module
object but can\nspecify 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\", NULL, Method, NULL, NULL, NULL, napi_default, NULL};\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_default, 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
\nIf the module will be loaded multiple times during the lifetime of the Node.js\nprocess, use the NAPI_MODULE_INIT
macro to initialize the module:
NAPI_MODULE_INIT() {\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
\nThis macro includes NAPI_MODULE
, and declares an Init
function with a\nspecial name and with visibility beyond the addon. This will allow Node.js to\ninitialize the module even if it is loaded multiple times.
There are a few design considerations when declaring a module that may be loaded\nmultiple times. The documentation of context-aware addons provides more\ndetails.
\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": "N-API exposes a set of APIs to create all types of JavaScript values.\nSome of these types are documented under\nSection 6\nof the ECMAScript Language Specification.
\nFundamentally, these APIs are used to do one of the following:\n1. Create a new JavaScript object\n2. Convert from a primitive C type to an N-API value\n3. Convert from N-API value to a primitive C type\n4. Get global instances including undefined
and null
N-API values are represented by the type napi_value
.\nAny N-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 // 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\nSection 6.1 of\nthe 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 N-API call is invoked under.[out] result
: A napi_value
representing a JavaScript Array
.Returns napi_ok
if the API succeeded.
This API returns an N-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 an N-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.\nIf 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
.[out] result
: A napi_value
representing a JavaScript ArrayBuffer
.Returns napi_ok
if the API succeeded.
This API returns an N-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.[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\nsize of 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.[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_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\nis being collected.[in] finalize_hint
: Optional hint to pass to the finalize callback\nduring collection.[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. The API allows the caller to pass in a finalize callback,\nin case the underlying native resource needs to be cleaned up when the external\nJavaScript value gets collected.
\nThe 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\nbeing collected.[in] finalize_hint
: Optional hint to pass to the finalize callback\nduring collection.[out] result
: A napi_value
representing a JavaScript ArrayBuffer
.Returns napi_ok
if the API succeeded.
This API returns an N-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.
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\nthe size of the new buffer).[in] data
: Raw pointer to the underlying buffer to copy from.[in] finalize_cb
: Optional callback to call when the ArrayBuffer
is\nbeing collected.[in] finalize_hint
: Optional hint to pass to the finalize callback\nduring collection.[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\nbacked by the passed in buffer. While this is still a fully-supported data\nstructure, in most cases using a TypedArray
will suffice.
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\nSection 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
object from a UTF8-encoded C string.
The JavaScript Symbol
type is described in\nSection 19.4\nof the ECMAScript Language 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\nNumber.MIN_SAFE_INTEGER
\n-(2^53 - 1) -\nNumber.MAX_SAFE_INTEGER
\n(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\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
object 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 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
object 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 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
\nif 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
object 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_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\nSection 22.1.4.1\nof the ECMAScript Language Specification.
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
.[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
being queried.[out] data
: The underlying data buffer of the node::Buffer
.[out] 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 a node::Buffer
\nand it's 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
.[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.
\nWarning: 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
.[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.
This API returns various properties of a DataView
.
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 size_t* word_count,\n int* sign_bit,\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 > 2^31 -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\nNumber.MIN_SAFE_INTEGER
\n-(2^53 - 1) -\nNumber.MAX_SAFE_INTEGER
\n(2^53 - 1) will lose precision.
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) is returned.[in] bufsize
: Size of the destination buffer. When this value is\ninsufficient, the returned string will be truncated.[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) is returned.[in] bufsize
: Size of the destination buffer. When this value is\ninsufficient, the returned string will be truncated.[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) is returned.[in] bufsize
: Size of the destination buffer. When this value is\ninsufficient, the returned string will be truncated.[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 - Abstract Operations", "name": "working_with_javascript_values_-_abstract_operations", "desc": "N-API exposes a set of APIs to perform some abstract operations on JavaScript\nvalues. Some of these operations are documented under\nSection 7\nof the ECMAScript Language Specification.
\nThese APIs support doing one of the following:\n1. Coerce JavaScript values to specific JavaScript types (such as Number
or\nString
).\n2. Check the type of a JavaScript value.\n3. Check for equality between two JavaScript values.
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\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object
.
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\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object
.
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\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object
.
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\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object
.
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, it has support for detecting an External value.\nIf 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\nfunction to 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\nSection 12.10.4\nof 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\nof 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
\nobject.Returns napi_ok
if the API succeeded.
This API checks if the Object
passed in is a buffer.
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\nSection 7.2.14\nof the ECMAScript Language Specification.
", "type": "module", "displayName": "napi_strict_equals" } ], "type": "misc", "displayName": "Working with JavaScript Values - Abstract Operations" }, { "textRaw": "Working with JavaScript Properties", "name": "working_with_javascript_properties", "desc": "N-API exposes a set of APIs to get and set properties on JavaScript\nobjects. Some of these types are documented under\nSection 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 N-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
.N-API values are represented by the type napi_value
.\nAny N-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 N-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 N-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 N-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 N-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_default, NULL },\n { \"bar\", NULL, NULL, NULL, NULL, barValue, napi_default, 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",
"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} 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
- Used to indicate that no explicit attributes are set on the\ngiven property. By default, a property is read only, not enumerable and not\nconfigurable.napi_writable
- Used to indicate that a given property is writable.napi_enumerable
- Used to indicate that a given property is enumerable.napi_configurable
- Used to indicate that a given property is configurable,\nas defined in Section 6.1.7.1 of the ECMAScript Language Specification.napi_static
- Used to indicate that the property will be defined as\na static property on a class as opposed to an instance property, which is the\ndefault. This is used only by napi_define_class
. It is ignored by\nnapi_define_properties
.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 the\nproperty is accessed from JavaScript code (or if a get on the property is\nperformed using a N-API call).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 the\nproperty is set from JavaScript code (or if a set on the property is\nperformed using a N-API call).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).attributes
: The attributes associated with the particular property.\nSee napi_property_attributes
.data
: The callback data passed into method
, getter
and setter
if\nthis function 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 N-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_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 N-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 N-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 N-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 N-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 N-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. N-API will not perform\nany 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 N-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 N-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 N-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 N-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 and 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 N-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 N-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 N-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 N-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 ECMA262\nspecification).
N-API provides a set of APIs that allow JavaScript code to\ncall back into native code. N-API 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, N-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_status napi_call_function(napi_env env,\n napi_value recv,\n napi_value func,\n int 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
object passed to the called function.[in] func
: napi_value
representing the JavaScript function\nto be invoked.[in] argc
: The count of elements in the argv
array.[in] argv
: Array of napi_values
representing JavaScript values passed\nin as 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}\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
: The name of the function encoded as UTF8. This is visible\nwithin JavaScript as the new function object's name
property.[in] length
: The length of the utf8name
in bytes, or\nNAPI_AUTO_LENGTH
if it is null-terminated.[in] cb
: The native function which should be called when this function\nobject is invoked.[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\nSection 19.2\nof the ECMAScript Language 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 size of the provided argv
array\nand receives the actual count of arguments.[out] argv
: Buffer to which the napi_value
representing the\narguments are copied. If there are more arguments than the provided\ncount, only the requested number of arguments are copied. If there are fewer\narguments provided than claimed, the rest of argv
is filled with napi_value
\nvalues that represent undefined
.[out] this
: Receives the JavaScript this
argument for the call.[out] data
: Receives the data pointer for the callback.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\nto be invoked as a constructor.[in] argc
: The count of elements in the argv
array.[in] argv
: Array of JavaScript values as napi_value
\nrepresenting the arguments to the constructor.[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 N-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.
N-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.
", "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; this is\nnot required to be the same as the C++ class name, though it is recommended\nfor clarity.[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. (This should be a static method on the class, not an actual\nC++ constructor function.)[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 that corresponds to a C++ class, including:
\nnapi_static
attribute).prototype
object corresponding to\nnon-static data properties, accessors, and methods of the C++ class\n(defined by property descriptors without the napi_static
attribute).The C++ constructor callback should be a static method on the class that calls\nthe actual class constructor, then wraps the new C++ instance in a JavaScript\nobject, and returns the wrapper object. 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 check whether provided values are instances of the class. In that\ncase, to prevent the function value from being garbage-collected, create a\npersistent reference to it using napi_create_reference
and ensure the\nreference 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 is ready for garbage-collection.[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.
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_add_finalizer(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 to which the native data will be\nattached.[in] native_object
: The native data that will be attached to the JavaScript\nobject.[in] finalize_cb
: Native callback that will be used to free the\nnative data when the JavaScript object is ready for garbage-collection.[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
is ready for garbage collection. This API is similar to\nnapi_wrap()
except that
napi_unwrap()
,napi_remove_wrap()
, andCaution: 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.
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\nis important in order to allow them to avoid blocking overall execution\nof the Node.js application.
\nN-API provides an ABI-stable interface for these\nsupporting functions which covers the most common asynchronous use cases.
\nN-API defines the napi_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 N-API calls\nthat could result in the execution of JavaScript or interaction with\nJavaScript objects. Most often, any code that needs to make N-API\ncalls should be made in complete
callback instead.
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(napi_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\nbeing provided for diagnostic information exposed by the async_hooks
API.[in] execute
: The native function which should be called to execute\nthe logic asynchronously. The given function is called from a worker pool\nthread and 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.[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(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 requests that the previously allocated work be scheduled\nfor execution.
", "type": "module", "displayName": "napi_queue_async_work" }, { "textRaw": "napi_cancel_async_work", "name": "napi_cancel_async_work", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_cancel_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 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
: 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\nthat is being provided for diagnostic information exposed by the\nasync_hooks
API.[out] result
: The initialized async context.Returns napi_ok
if the API succeeded.
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", "description": "Added `async_context` parameter." } ] }, "desc": "napi_status napi_make_callback(napi_env env,\n napi_async_context async_context,\n napi_value recv,\n napi_value func,\n int 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
. However NULL
is also allowed,\nwhich indicates the current async context (if any) is to be used\nfor the callback.[in] recv
: The this
object passed to the called function.[in] func
: napi_value
representing the JavaScript function\nto be invoked.[in] argc
: The count of elements in the argv
array.[in] argv
: Array of JavaScript values as napi_value
\nrepresenting the 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 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
.
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 optional object associated with the async work\nthat will be passed to possible async_hooks
init
hooks.[in] context
: Context for the async operation that is\ninvoking the callback. This should be a value previously obtained\nfrom 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 N-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(napi_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(napi_env env,\n uint32_t* result);\n
\n[in] env
: The environment that the API is invoked under.[out] result
: The highest version of N-API supported.Returns napi_ok
if the API succeeded.
This API returns the highest N-API version supported by the\nNode.js runtime. N-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(napi_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\nkept alive 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 module). Registering\nexternally allocated memory will trigger global garbage collections more\noften than it would otherwise.
\n\n", "type": "module", "displayName": "napi_adjust_external_memory" } ], "type": "misc", "displayName": "Memory Management" }, { "textRaw": "Promises", "name": "promises", "desc": "N-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 promise,\n bool* is_promise);\n
\n[in] env
: The environment that the API is invoked under.[in] promise
: The promise to examine[out] is_promise
: Flag indicating whether promise
is a native promise\nobject - that is, a promise object created by the underlying engine.N-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.N-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(napi_env env,\n uv_loop_t** 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 N-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()
. It is important that, aside from\nthe main loop thread, there be no threads left using the thread-safe function\nafter the finalize callback completes.
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 then 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.
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\nN-API runs call_js_cb
in a context appropriate for callbacks.
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. It is important that\nnapi_release_threadsafe_function()
be the last API call made in conjunction\nwith a given napi_threadsafe_function
, because after the call completes, there\nis no guarantee that the napi_threadsafe_function
is still allocated. For the\nsame reason it is also important that no more use be made of a thread-safe\nfunction after receiving a return value of napi_closing
in response to a call\nto napi_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()
.
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 make no\nfurther use of the thread-safe function 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.
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
: The JavaScript function to call from another thread.[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 threads, including the main\nthread, which will be making use of 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.[out] result
: The asynchronous thread-safe JavaScript function.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 with\na status of napi_queue_full
whenever the queue is full.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 function,\nor napi_tsfn_abort
to indicate that in addition to the current thread, no\nother thread should make any further calls to the thread-safe function. If set\nto napi_tsfn_abort
, further calls to napi_call_threadsafe_function()
will\nreturn napi_closing
, and no further values 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(napi_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.
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", "stability": 1, "stabilityText": "Experimental", "meta": { "added": [ "v10.6.0" ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\nnapi_unref_threadsafe_function(napi_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": "Command Line Options", "name": "Command Line Options", "introduced_in": "v5.9.1", "type": "misc", "desc": "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] [script.js | -e \"script\" | -] [--] [arguments]
node inspect [script.js | -e \"script\" | <host>:<port>] …
node --v8-options
Execute without arguments to start the REPL.
\nFor more info about node inspect
, please see the debugger documentation.
All options, including V8 options, allow words to be separated by both\ndashes (-
) or underscores (_
).
For example, --pending-deprecation
is equivalent to --pending_deprecation
.
Alias for stdin, analogous to the use of - in other command line utilities,\nmeaning that the script will be read from stdin, and the rest of the options\nare passed to that script.
", "type": "module", "displayName": "`-`" }, { "textRaw": "`--`", "name": "`--`", "meta": { "added": [ "v6.11.0" ], "changes": [] }, "desc": "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 will be used as a script filename.
", "type": "module", "displayName": "`--`" }, { "textRaw": "`--abort-on-uncaught-exception`", "name": "`--abort-on-uncaught-exception`", "meta": { "added": [ "v0.10" ], "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\ndomain
module that uses it).
Print source-able bash completion script for Node.js.
\n$ node --completion-bash > node_bash_completion\n$ source node_bash_completion\n
",
"type": "module",
"displayName": "`--completion-bash`"
},
{
"textRaw": "`--enable-fips`",
"name": "`--enable-fips`",
"meta": {
"added": [
"v6.0.0"
],
"changes": []
},
"desc": "Enable FIPS-compliant crypto at startup. (Requires Node.js to be built with\n./configure --openssl-fips
.)
Enable experimental ES module support and caching modules.
", "type": "module", "displayName": "`--experimental-modules`" }, { "textRaw": "`--experimental-repl-await`", "name": "`--experimental-repl-await`", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "desc": "Enable experimental top-level await
keyword support in REPL.
Enable experimental ES Module support in the vm
module.
Enable experimental worker threads using the worker_threads
module.
Force FIPS-compliant crypto on startup. (Cannot be disabled from script code.)\n(Same requirements as --enable-fips
.)
Chooses an HTTP parser library. Available values are:
\nllhttp
for https://llhttp.org/legacy
for https://github.com/nodejs/http-parserThe default is legacy
, unless otherwise specified when building Node.js.
This flag exists to aid in experimentation with the internal implementation of\nthe Node.js http parser.\nThis flag is likely to become a no-op and removed at some point in the future.
", "type": "module", "displayName": "`--http-parser=library`" }, { "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
.)
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.
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", "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 you specify a host, make sure that at least one of the following is true:\neither the host is not public, or the port is properly firewalled to disallow\nunwanted connections.
\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": "`--loader=file`", "name": "`--loader=file`", "meta": { "added": [ "v9.0.0" ], "changes": [] }, "desc": "Specify the file
of the custom experimental ECMAScript Module loader.
This option is a no-op. It is kept for compatibility.
", "type": "module", "displayName": "`--napi-modules`" }, { "textRaw": "`--no-deprecation`", "name": "`--no-deprecation`", "meta": { "added": [ "v0.8.0" ], "changes": [] }, "desc": "Silence deprecation warnings.
", "type": "module", "displayName": "`--no-deprecation`" }, { "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.
Silence all process warnings (including deprecations).
", "type": "module", "displayName": "`--no-warnings`" }, { "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 with\n./configure --openssl-fips
.
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 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.
Note that --preserve-symlinks-main
does not imply --preserve-symlinks
; it\nis expected that --preserve-symlinks-main
will be used in addition to\n--preserve-symlinks
when it is not desirable to follow symlinks before\nresolving relative paths.
See --preserve-symlinks
for more information.
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.
", "type": "module", "displayName": "`--redirect-warnings=file`" }, { "textRaw": "`--throw-deprecation`", "name": "`--throw-deprecation`", "meta": { "added": [ "v0.11.14" ], "changes": [] }, "desc": "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": "`--trace-deprecation`", "name": "`--trace-deprecation`", "meta": { "added": [ "v0.8.0" ], "changes": [] }, "desc": "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-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-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": "`--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
.
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 V8 will choose an appropriate size of the thread pool based\non the number of online processors.
If the value provided is larger than V8's maximum, then the largest value\nwill be chosen.
", "type": "module", "displayName": "`--v8-pool-size=num`" }, { "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.
Syntax check the script without executing.
", "type": "module", "displayName": "`-c`, `--check`" }, { "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.
Print node command line options.\nThe output of this option is less detailed than this document.
", "type": "module", "displayName": "`-h`, `--help`" }, { "textRaw": "`-i`, `--interactive`", "name": "`-i`,_`--interactive`", "meta": { "added": [ "v0.7.7" ], "changes": [] }, "desc": "Opens the REPL even if stdin does not appear to be a terminal.
", "type": "module", "displayName": "`-i`, `--interactive`" }, { "textRaw": "`-p`, `--print \"script\"`", "name": "`-p`,_`--print_\"script\"`", "meta": { "added": [ "v0.6.4" ], "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": "Identical to -e
but prints the result.
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.
Print node's version.
", "type": "module", "displayName": "`-v`, `--version`" } ], "type": "misc", "displayName": "Options" }, { "textRaw": "Environment Variables", "name": "environment_variables", "modules": [ { "textRaw": "`NODE_DEBUG=module[,…]`", "name": "`node_debug=module[,…]`", "meta": { "added": [ "v0.1.32" ], "changes": [] }, "desc": "','
-separated list of core modules that should print debug information.
','
-separated list of core C++ modules that should print debug information.
When set to 1
colors will not be used in the REPL.
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.
Note that 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.
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 as\nif they had been specified on the command line before the actual command line\n(so they can be overridden). Node.js will exit with an error if an option\nthat is not allowed in the environment is used, such as -p
or a script file.
Node.js options that are allowed are:
\n--enable-fips
--experimental-modules
--experimental-repl-await
--experimental-vm-modules
--experimental-worker
--force-fips
--icu-data-dir
--inspect
--inspect-brk
--inspect-port
--loader
--napi-modules
--no-deprecation
--no-force-async-hooks-checks
--no-warnings
--openssl-config
--pending-deprecation
--redirect-warnings
--require
, -r
--throw-deprecation
--title
--tls-cipher-list
--trace-deprecation
--trace-event-categories
--trace-event-file-pattern
--trace-events-enabled
--trace-sync-io
--trace-warnings
--track-heap-objects
--use-bundled-ca
--use-openssl-ca
--v8-pool-size
--zero-fill-buffers
V8 options that are allowed are:
\n--abort-on-uncaught-exception
--max-old-space-size
--perf-basic-prof
--perf-prof
--stack-trace-limit
':'
-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.
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 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 '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 to the\ndirectory provided as an argument. Coverage is output as an array of\nScriptCoverage objects:
\n{\n \"result\": [\n {\n \"scriptId\": \"67\",\n \"url\": \"internal/tty.js\",\n \"functions\": []\n }\n ]\n}\n
\nNODE_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.
At this time coverage is only collected in the main thread and will not be\noutput for code executed by worker threads.
", "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 ./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": "`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.randomBytes()
, unless it is used without a callbackcrypto.randomFill()
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.
Node.js includes an out-of-process debugging utility accessible via a\nV8 Inspector and built-in debugging client. To use it, start Node.js\nwith the inspect
argument followed by the path to the script to debug; a\nprompt will be displayed indicating successful launch of the debugger:
$ node inspect myscript.js\n< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba\n< For help, see: https://nodejs.org/en/docs/inspector\n< Debugger attached.\nBreak on start in myscript.js:1\n> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;\n 2 setTimeout(() => {\n 3 console.log('world');\ndebug>\n
\nNode.js's debugger client is not a full-featured debugger, but simple step and\ninspection are possible.
\nInserting the statement debugger;
into the source code of a script will\nenable a breakpoint at that position in the code:
// myscript.js\nglobal.x = 5;\nsetTimeout(() => {\n debugger;\n console.log('world');\n}, 1000);\nconsole.log('hello');\n
\nOnce the debugger is run, a breakpoint will occur at line 3:
\n$ node inspect myscript.js\n< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba\n< For help, see: https://nodejs.org/en/docs/inspector\n< Debugger attached.\nBreak on start in myscript.js:1\n> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;\n 2 setTimeout(() => {\n 3 debugger;\ndebug> cont\n< hello\nbreak in myscript.js:3\n 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;\n 2 setTimeout(() => {\n> 3 debugger;\n 4 console.log('world');\n 5 }, 1000);\ndebug> next\nbreak in myscript.js:4\n 2 setTimeout(() => {\n 3 debugger;\n> 4 console.log('world');\n 5 }, 1000);\n 6 console.log('hello');\ndebug> repl\nPress Ctrl + C to leave debug repl\n> x\n5\n> 2 + 2\n4\ndebug> next\n< world\nbreak in myscript.js:5\n 3 debugger;\n 4 console.log('world');\n> 5 }, 1000);\n 6 console.log('hello');\n 7\ndebug> .exit\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\nfunctions bodysetBreakpoint('script.js', 1)
, sb(...)
- Set breakpoint on first line of\nscript.js
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://127.0.0.1:9229/4e3db158-9791-4274-8909-914f7facf3bd\n< For help, see: https://nodejs.org/en/docs/inspector\n< Debugger attached.\nBreak on start in main.js:1\n> 1 (function (exports, require, module, __filename, __dirname) { 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
",
"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 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
- Execute an expression in debugging script's contextrun
- 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 127.0.0.1:9229.\nTo start debugging, open the following URL in Chrome:\n chrome-devtools://devtools/bundled/js_app.html?experiments=true&v8only=true&ws=127.0.0.1:9229/dc9010dd-f8b8-4ac5-a510-c1a114ec7d29\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.
Node.js may deprecate APIs when either: (a) use of the API is considered to be\nunsafe, (b) an improved alternative API is available, or (c) breaking changes to\nthe API are expected in a future major release.
\nNode.js utilizes three kinds of Deprecations:
\nA 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.
A Runtime deprecation will, by default, generate a process warning that will\nbe printed to stderr
the first time the deprecated API is used. When the\n--throw-deprecation
command-line flag is used, a Runtime deprecation will\ncause an error to be thrown.
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 may 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", "desc": "", "modules": [ { "textRaw": "DEP0001: http.OutgoingMessage.prototype.flush", "name": "dep0001:_http.outgoingmessage.prototype.flush", "meta": { "changes": [ { "version": [ "v4.8.6", "v6.12.0" ], "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: Runtime
\nThe OutgoingMessage.prototype.flush()
method is deprecated. Use\nOutgoingMessage.prototype.flushHeaders()
instead.
Type: End-of-Life
\nThe _linklist
module is deprecated. Please use a userland alternative.
Type: Runtime
\nThe _writableState.buffer
property is deprecated. Use the\n_writableState.getBuffer()
method instead.
Type: End-of-Life
\nThe CryptoStream.prototype.readyState
property was removed.
Type: Runtime (supports --pending-deprecation
)
The Buffer()
function and new Buffer()
constructor are deprecated due to\nAPI usability issues that can potentially lead to accidental security issues.
As an alternative, use of the following methods of constructing Buffer
objects\nis strongly recommended:
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
.As of v10.0.0, a deprecation warning is printed at runtime when\n--pending-deprecation
is used or when the calling code is\noutside node_modules
in order to better target developers, rather than users.
Type: Runtime
\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 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('fs').constants
and require('os').constants
.
Type: Runtime
\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
will print a deprecation warning to align with the behavior when digest
\nis undefined
.
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: Runtime
\nThe GLOBAL
and root
aliases for the global
property are deprecated\nand should no longer be used.
Type: End-of-Life
\nIntl.v8BreakIterator
was a non-standard extension and has been removed.\nSee Intl.Segmenter
.
Type: Runtime
\nUnhandled promise rejections are deprecated. In the future, promise rejections\nthat are not handled will terminate the Node.js process with a non-zero exit\ncode.
\n", "type": "module", "displayName": "DEP0018: Unhandled promise rejections" }, { "textRaw": "DEP0019: require('.') resolved outside directory", "name": "dep0019:_require('.')_resolved_outside_directory", "meta": { "changes": [ { "version": [ "v4.8.6", "v6.12.0" ], "pr-url": "https://github.com/nodejs/node/pull/10116", "description": "A deprecation code has been assigned." }, { "version": "v1.8.1", "pr-url": "https://github.com/nodejs/node/pull/1363", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nIn certain cases, require('.')
may resolve outside the package directory.\nThis behavior is deprecated and will be removed in a future major Node.js\nrelease.
Type: Runtime
\nThe Server.connections
property is deprecated. Please use the\nServer.getConnections()
method instead.
Type: Runtime
\nThe Server.listenFD()
method is deprecated. Please use\nServer.listen({fd: <number>})
instead.
Type: Runtime
\nThe os.tmpDir()
API is deprecated. Please use os.tmpdir()
instead.
Type: Runtime
\nThe os.getNetworkInterfaces()
method is deprecated. Please use the\nos.networkInterfaces
property instead.
Type: End-of-Life
\nThe REPLServer.prototype.convertToContext()
API has been removed.
Type: Runtime
\nThe sys
module is deprecated. Please use the util
module instead.
Type: Runtime
\nThe util.print()
API is deprecated. Please use console.log()
\ninstead.
Type: Runtime
\nThe util.puts()
API is deprecated. Please use console.log()
instead.
Type: Runtime
\nThe util.debug()
API is deprecated. Please use console.error()
\ninstead.
Type: Runtime
\nThe util.error()
API is deprecated. Please use console.error()
\ninstead.
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 EventEmitter.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 is deprecated.
Type: Deprecation revoked
\nThe fs.lchownSync(path, uid, gid)
API is deprecated.
Type: Documentation-only
\nThe require.extensions
property is deprecated.
Type: Documentation-only
\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: Runtime
\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 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 repl
module's REPL_MODE_MAGIC
constant, used for replMode
option, has\nbeen 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: Documentation-only
\nThe http
module outgoingMessage._headers
and outgoingMessage._headerNames
\nproperties are deprecated. Use one of the public methods\n(e.g. outgoingMessage.getHeader()
, outgoingMessage.getHeaders()
,\noutgoingMessage.getHeaderNames()
, outgoingMessage.hasHeader()
,\noutgoingMessage.removeHeader()
, outgoingMessage.setHeader()
) for working\nwith outgoing headers.
The outgoingMessage._headers
and outgoingMessage._headerNames
properties\nwere never documented as officially supported properties.
Type: Documentation-only
\nThe http
module OutgoingMessage.prototype._renderHeaders()
API is\ndeprecated.
The OutgoingMessage.prototype._renderHeaders
property was never documented as\nan officially supported API.
Type: Runtime
\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.
\n", "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.
\n", "type": "module", "displayName": "DEP0073: Several internal properties of net.Server" }, { "textRaw": "DEP0074: REPLServer.bufferedCommand", "name": "dep0074:_replserver.bufferedcommand", "meta": { "changes": [ { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/13687", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nThe REPLServer.bufferedCommand
property was deprecated in favor of\nREPLServer.clearBufferedCommand()
.
Type: Runtime
\nREPLServer.parseREPLKeyword()
was removed from userland visibility.
Type: Runtime
\ntls.parseCertString()
is a trivial parsing helper that was made public by\nmistake. This function can usually be replaced with:
const querystring = require('querystring');\nquerystring.parse(str, '\\n', '=');\n
\nThis function is not completely equivalent to querystring.parse()
. One\ndifference is that querystring.parse()
does url decoding:
> querystring.parse('%E5%A5%BD=1', '\\n', '=');\n{ '好': '1' }\n> tls.parseCertString('%E5%A5%BD=1');\n{ '%E5%A5%BD': '1' }\n
\n",
"type": "module",
"displayName": "DEP0076: tls.parseCertString()"
},
{
"textRaw": "DEP0077: Module._debug()",
"name": "dep0077:_module._debug()",
"meta": {
"changes": [
{
"version": "v9.0.0",
"pr-url": "https://github.com/nodejs/node/pull/13948",
"description": "Runtime deprecation."
}
]
},
"desc": "Type: Runtime
\nModule._debug()
is deprecated.
The Module._debug()
function was never documented as an officially\nsupported API.
Type: Runtime
\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\nmay 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: Runtime
\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: Runtime
\nSince Node.js versions 4.4.0 and 5.2.0, several modules only intended for\ninternal usage are mistakenly exposed to user code through require()
. These\nmodules are:
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
may 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.\n(See https://github.com/nodejs/node/issues/15572.) Use the AsyncResource
\nAPI instead.
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 for\nmore details.
Type: Documentation-only
\nImporting assert directly is not recommended as the exposed functions will use\nloose equality checks. Use require('assert').strict
instead. The API is the\nsame as the legacy assert but it will always use strict equality checks.
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 v11.0.0,\nonly authentication tag lengths of 128, 120, 112, 104, 96, 64, and 32 bits are\nallowed. Authentication tags whose length is not included in this list are\nconsidered invalid in compliance with NIST SP 800-38D.
Type: Runtime
\nThe crypto.DEFAULT_ENCODING
property is deprecated.
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 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: Runtime
\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 for more details.
Type: Compile-time
\nCertain versions of node::MakeCallback
APIs available to native modules 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.
\n", "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 going\nto be verified, no matter if it is set to true or not. 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 may\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()
should 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()
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.
\n", "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: Runtime
\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
\nThe process.binding()
API is intended for use by Node.js internal code\nonly. Use of process.binding()
by userland code is unsupported.
Type: Runtime
\nThe dgram
module previously contained several APIs that were never meant to\naccessed 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: Runtime
\nWith the current crypto API, having Cipher.setAuthTag()
and\nDecipher.getAuthTag()
is not helpful and both functions will throw an error\nwhen called. They have never been documented and will be removed in a future\nrelease.
Type: Runtime
\nThe crypto._toBuf()
function was not designed to be used by modules outside\nof Node.js core and will be removed in the future.
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 may be removed in a\nfuture release.
Type: Documentation-only
\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: Runtime
\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.\nUsing the _handle
property to access the native object is deprecated because\nimproper use of the native object can lead to crashing the application.
Type: Runtime
\nPrevious versions of Node.js supported dns.lookup()
with a falsy hostname\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
)
Directly calling process.binding('uv').errname(<val>)
is deprecated.\nPlease make sure to use util.getSystemErrorName()
instead.
Type: Runtime
\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.
Node.js contains support for ES Modules based upon the\nNode.js EP for ES Modules.
\nNot all features of the EP are complete and will be landing as both VM support\nand implementation is ready. Error messages are still being polished.
", "miscs": [ { "textRaw": "Enabling", "name": "Enabling", "type": "misc", "desc": "The --experimental-modules
flag can be used to enable features for loading\nESM modules.
Once this has been set, files ending with .mjs
will be able to be loaded\nas ES Modules.
node --experimental-modules my-app.mjs\n
"
},
{
"textRaw": "Features",
"name": "Features",
"type": "misc",
"miscs": [
{
"textRaw": "Supported",
"name": "supported",
"desc": "Only the CLI argument for the main entry point to the program can be an entry\npoint into an ESM graph. Dynamic import can also be used to create entry points\ninto ESM graphs at runtime.
", "properties": [ { "textRaw": "`meta` {Object}", "type": "Object", "name": "meta", "desc": "The import.meta
metaproperty is an Object
that contains the following\nproperty:
url
<string> The absolute file:
URL of the module.Feature | \nReason | \n
---|---|
require('./foo.mjs') | \nES Modules have differing resolution and timing, use dynamic import | \n
NODE_PATH
is not part of resolving import
specifiers. Please use symlinks\nif this behavior is desired.
require.extensions
is not used by import
. The expectation is that loader\nhooks can provide this workflow in the future.
require.cache
is not used by import
. It has a separate cache.
ESM are resolved and cached based upon URL\nsemantics. This means that files containing special characters such as #
and\n?
need to be escaped.
Modules will be loaded multiple times if the import
specifier used to resolve\nthem have a different query or fragment.
import './foo?query=1'; // loads ./foo with query of \"?query=1\"\nimport './foo?query=2'; // loads ./foo with query of \"?query=2\"\n
\nFor now, only modules using the file:
protocol can be loaded.
All CommonJS, JSON, and C++ modules can be used with import
.
Modules loaded this way will only be loaded once, even if their query\nor fragment string differs between import
statements.
When loaded via import
these modules will provide a single default
export\nrepresenting the value of module.exports
at the time they finished evaluating.
// foo.js\nmodule.exports = { one: 1 };\n\n// bar.js\nimport foo from './foo.js';\nfoo.one === 1; // true\n
\nBuiltin modules will provide named exports of their public API, as well as a\ndefault export which can be used for, among other things, modifying the named\nexports. Named exports of builtin modules are updated when the corresponding\nexports property is accessed, redefined, or deleted.
\nimport EventEmitter from 'events';\nconst e = new EventEmitter();\n
\nimport { readFile } from '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 'fs';\n\nfs.readFileSync = () => Buffer.from('Hello, ESM');\n\nfs.readFileSync === readFileSync;\n
",
"type": "misc",
"displayName": "Interop with existing modules"
},
{
"textRaw": "Loader hooks",
"name": "Loader hooks",
"type": "misc",
"desc": "To customize the default module resolution, loader hooks can optionally be\nprovided via a --loader ./loader-name.mjs
argument to Node.js.
When hooks are used they only apply to ES module loading and not to any\nCommonJS modules loaded.
", "miscs": [ { "textRaw": "Resolve hook", "name": "resolve_hook", "desc": "The resolve hook returns the resolved file URL and module format for a\ngiven module specifier and parent file URL:
\nconst baseURL = new URL('file://');\nbaseURL.pathname = `${process.cwd()}/`;\n\nexport async function resolve(specifier,\n parentModuleURL = baseURL,\n defaultResolver) {\n return {\n url: new URL(specifier, parentModuleURL).href,\n format: 'esm'\n };\n}\n
\nThe parentModuleURL
is provided as undefined
when performing main Node.js\nload itself.
The default Node.js ES module resolution function is provided as a third\nargument to the resolver for easy compatibility workflows.
\nIn addition to returning the resolved file URL value, the resolve hook also\nreturns a format
property specifying the module format of the resolved\nmodule. This can be one of the following:
format | \nDescription | \n
---|---|
'esm' | \nLoad a standard JavaScript module | \n
'cjs' | \nLoad a node-style CommonJS module | \n
'builtin' | \nLoad a node builtin CommonJS module | \n
'json' | \nLoad a JSON file | \n
'addon' | \nLoad a C++ Addon | \n
'dynamic' | \nUse a dynamic instantiate hook | \n
For example, a dummy loader to load JavaScript restricted to browser resolution\nrules with only JS file extension and Node.js builtin modules support could\nbe written:
\nimport path from 'path';\nimport process from 'process';\nimport Module from 'module';\n\nconst builtins = Module.builtinModules;\nconst JS_EXTENSIONS = new Set(['.js', '.mjs']);\n\nconst baseURL = new URL('file://');\nbaseURL.pathname = `${process.cwd()}/`;\n\nexport function resolve(specifier, parentModuleURL = baseURL, defaultResolve) {\n if (builtins.includes(specifier)) {\n return {\n url: specifier,\n format: 'builtin'\n };\n }\n if (/^\\.{0,2}[/]/.test(specifier) !== true && !specifier.startsWith('file:')) {\n // For node_modules support:\n // return defaultResolve(specifier, parentModuleURL);\n throw new Error(\n `imports must begin with '/', './', or '../'; '${specifier}' does not`);\n }\n const resolved = new URL(specifier, parentModuleURL);\n const ext = path.extname(resolved.pathname);\n if (!JS_EXTENSIONS.has(ext)) {\n throw new Error(\n `Cannot load file with non-JavaScript file extension ${ext}.`);\n }\n return {\n url: resolved.href,\n format: 'esm'\n };\n}\n
\nWith this loader, running:
\nNODE_OPTIONS='--experimental-modules --loader ./custom-loader.mjs' node x.js\n
\nwould load the module x.js
as an ES module with relative resolution support\n(with node_modules
loading skipped in this example).
To create a custom dynamic module that doesn't correspond to one of the\nexisting format
interpretations, the dynamicInstantiate
hook can be used.\nThis hook is called only for modules that return format: 'dynamic'
from\nthe resolve
hook.
export async function dynamicInstantiate(url) {\n return {\n exports: ['customExportName'],\n execute: (exports) => {\n // get and set functions provided for pre-allocated export names\n exports.customExportName.set('value');\n }\n };\n}\n
\nWith the list of module exports provided upfront, the execute
function will\nthen be called at the exact point of module evaluation order for that module\nin the import tree.
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 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 undefined\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 using try…catch
or the Node.js process will exit\nimmediately.
With few exceptions, Synchronous APIs (any blocking method that does not\naccept a callback
function, such as fs.readFileSync
), will use throw
\nto report errors.
Errors that occur within Asynchronous APIs may be reported in multiple ways:
\ncallback
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('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('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: The domain
module is\nused appropriately or a handler has been registered for the\n'uncaughtException'
event.
const EventEmitter = require('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.
", "miscs": [ { "textRaw": "Error-first callbacks", "name": "Error-first callbacks", "type": "misc", "desc": "Most asynchronous methods exposed by the Node.js core API follow an idiomatic\npattern referred to as an error-first callback. With this pattern, a callback\nfunction is passed to the method as an argument. When the operation either\ncompletes or an error is raised, the callback function is called with the\nError
object (if any) passed as the first argument. If no error was raised,\nthe first argument will be passed as null
.
const fs = require('fs');\n\nfunction errorFirstCallback(err, data) {\n if (err) {\n console.error('There was an error', err);\n return;\n }\n console.log(data);\n}\n\nfs.readFile('/some/file/that/does-not-exist', errorFirstCallback);\nfs.readFile('/some/file/that/does-exist', errorFirstCallback);\n
\nThe JavaScript try…catch
mechanism cannot be used to intercept errors\ngenerated by asynchronous APIs. A common mistake for beginners is to try to\nuse throw
inside an error-first callback:
// THIS WILL NOT WORK:\nconst fs = require('fs');\n\ntry {\n fs.readFile('/some/file/that/does-not-exist', (err, data) => {\n // mistaken assumption: throwing here...\n if (err) {\n throw err;\n }\n });\n} catch (err) {\n // This will not catch the throw!\n console.error(err);\n}\n
\nThis will not work because the callback function passed to fs.readFile()
is\ncalled asynchronously. By the time the callback has been called, the\nsurrounding code (including the try { } catch (err) { }
block will have\nalready exited. Throwing an error inside the callback can crash the Node.js\nprocess in most cases. If domains are enabled, or a handler has been\nregistered with process.on('uncaughtException')
, such errors can be\nintercepted.
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.
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.
\nSystem errors are usually generated at the syscall level. For a comprehensive\nlist, see the errno
(3) man page.
In Node.js, system errors are Error
objects with extra properties.
address
<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> | <string> 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 number or a string. If it is a number, it is a\nnegative value which corresponds to the error code defined in\nlibuv Error handling
. See the libuv errno.h
header file\n(deps/uv/include/uv/errno.h
in the Node.js source tree) for details. In case\nof a string, it is the same as error.code
.
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
.
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.
A function argument is being used in a way that suggests that the function\nsignature may be misunderstood. This is thrown by the assert
module when the\nmessage
parameter in assert.throws(block, message)
matches the error message\nthrown by block
because that usage suggests that the user believes message
\nis the expected message rather than the message the AssertionError
will\ndisplay 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 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. Note that users are also able\nto define their own types if using the public embedder API.
\n", "type": "module", "displayName": "ERR_ASYNC_TYPE" }, { "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.
The value passed to postMessage()
contained an object that is not supported\nfor transferring.
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 constructor for a class was called without new
.
The native call from process.cpuUsage
could not be processed.
A client certificate engine was requested that is not supported by the version\nof OpenSSL being used.
\n", "type": "module", "displayName": "ERR_CRYPTO_CUSTOM_ENGINE_NOT_SUPPORTED" }, { "textRaw": "ERR_CRYPTO_ECDH_INVALID_FORMAT", "name": "err_crypto_ecdh_invalid_format", "desc": "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('crypto').setEngine()
.
The --force-fips
command-line argument was used but there was an attempt\nto enable or disable FIPS mode in the 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_DIGEST_NO_UTF16", "name": "err_crypto_hash_digest_no_utf16", "desc": "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.
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 selected public or private key encoding is incompatible with other options.
\n", "type": "module", "displayName": "ERR_CRYPTO_INCOMPATIBLE_KEY_OPTIONS" }, { "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_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()
.
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.
c-ares
failed to set the DNS server.
The domain
module was not usable since it could not establish the required\nerror handling hooks, because\nprocess.setUncaughtExceptionCaptureCallback()
had been called at an\nearlier point in time.
process.setUncaughtExceptionCaptureCallback()
could not be called\nbecause the 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\ndomain
module had been loaded.
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.
A Promise
that was callbackified via util.callbackify()
was rejected with a\nfalsy value.
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_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.
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_HEADER_SINGLE_VALUE", "name": "err_http2_header_single_value", "desc": "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_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_SOCKET_MANIPULATION", "name": "err_http2_no_socket_manipulation", "desc": "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_TRAILERS_ALREADY_SENT", "name": "err_http2_trailers_already_sent", "desc": "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:
.
While using the inspector
module, an attempt was made to connect when the\ninspector was already connected.
While using the inspector
module, an attempt was made to use the inspector\nafter the session had already closed.
The inspector
module is not available for use.
While using the inspector
module, an attempt was made to use the inspector\nbefore it was connected.
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.
A callback function was required but was not been provided to a Node.js API.
\n", "type": "module", "displayName": "ERR_INVALID_CALLBACK" }, { "textRaw": "ERR_INVALID_CHAR", "name": "err_invalid_char", "desc": "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()
for\nmore 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_OPT_VALUE", "name": "err_invalid_opt_value", "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", "desc": "An invalid or unknown file encoding was passed.
\n", "type": "module", "displayName": "ERR_INVALID_OPT_VALUE_ENCODING" }, { "textRaw": "ERR_INVALID_PERFORMANCE_MARK", "name": "err_invalid_performance_mark", "desc": "While using the Performance Timing API (perf_hooks
), a performance mark is\ninvalid.
An invalid options.protocol
was passed.
Both breakEvalOnSigint
and eval
options were set in the REPL config, which\nis not supported.
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_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_TRANSFER_OBJECT",
"name": "err_invalid_transfer_object",
"desc": "An invalid transfer object was passed to postMessage()
.
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\nURL
constructor to be parsed. The thrown error object\ntypically has an additional property 'input'
that contains the URL that failed\nto 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 attempt was made to allocate memory (usually in the C++ layer) but it\nfailed.
\n", "type": "module", "displayName": "ERR_MEMORY_ALLOCATION_FAILED" }, { "textRaw": "ERR_METHOD_NOT_IMPLEMENTED", "name": "err_method_not_implemented", "desc": "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.
An ES6 module loader hook specified format: 'dynamic'
but did not provide\na dynamicInstantiate
hook.
A MessagePort
was found in the object passed to a postMessage()
call,\nbut not provided in the transferList
for that call.
An ES6 module could not be resolved.
\n", "type": "module", "displayName": "ERR_MISSING_MODULE" }, { "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_RESOLUTION_LEGACY", "name": "err_module_resolution_legacy", "stability": 1, "stabilityText": "Experimental", "desc": "A failure occurred resolving imports in an ES6 module.
\n", "type": "module", "displayName": "ERR_MODULE_RESOLUTION_LEGACY" }, { "textRaw": "ERR_MULTIPLE_CALLBACK", "name": "err_multiple_callback", "desc": "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 N-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_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_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])
.
A given value is out of the accepted range.
\n", "type": "module", "displayName": "ERR_OUT_OF_RANGE" }, { "textRaw": "ERR_REQUIRE_ESM", "name": "err_require_esm", "stability": 1, "stabilityText": "Experimental", "desc": "An attempt was made to require()
an ES6 module.
Script execution was interrupted by SIGINT
(For example, when Ctrl+C was\npressed).
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.
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.
Data could be sent on a socket.
\n", "type": "module", "displayName": "ERR_SOCKET_CANNOT_SEND" }, { "textRaw": "ERR_SOCKET_CLOSED", "name": "err_socket_closed", "desc": "An attempt was made to operate on an already closed socket.
\n", "type": "module", "displayName": "ERR_SOCKET_CLOSED" }, { "textRaw": "ERR_SOCKET_DGRAM_NOT_RUNNING", "name": "err_socket_dgram_not_running", "desc": "A call was made and the UDP subsystem was not running.
\n", "type": "module", "displayName": "ERR_SOCKET_DGRAM_NOT_RUNNING" }, { "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('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_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.
While using TLS, the hostname/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_PROTOCOL_VERSION", "name": "err_tls_invalid_protocol_version", "desc": "Valid TLS protocol versions are 'TLSv1'
, 'TLSv1.1'
, or 'TLSv1.2'
.
Attempting to set a TLS protocol minVersion
or maxVersion
conflicts with an\nattempt to set the secureProtocol
explicitly. Use one mechanism or the other.
An attempt to renegotiate the TLS session failed.
\n", "type": "module", "displayName": "ERR_TLS_RENEGOTIATE" }, { "textRaw": "ERR_TLS_RENEGOTIATION_DISABLED", "name": "err_tls_renegotiation_disabled", "desc": "An attempt was made to renegotiate TLS on a socket instance with TLS disabled.
\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 hostname 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 trace_events
module could not be loaded because Node.js was compiled with\nthe --without-v8-platform
flag.
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.
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_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET", "name": "err_uncaught_exception_capture_already_set", "desc": "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()
).
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.
While using the Performance Timing API (perf_hooks
), no valid performance\nentry types were found.
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 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_LINKING_ERRORED", "name": "err_vm_module_linking_errored", "desc": "The linker function returned a module for which linking has failed.
\n", "type": "module", "displayName": "ERR_VM_MODULE_LINKING_ERRORED" }, { "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_NOT_MODULE", "name": "err_vm_module_not_module", "desc": "The fulfilled value of a linking promise is not a vm.SourceTextModule
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_WORKER_PATH", "name": "err_worker_path", "desc": "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_EXTENSION", "name": "err_worker_unsupported_extension", "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_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 8KB 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.
A module file could not be resolved while attempting a require()
or\nimport
operation.
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_NAPI_CONS_PROTOTYPE_OBJECT", "name": "err_napi_cons_prototype_object", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used by the N-API
when Constructor.prototype
is not an object.
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 repl
module was unable to parse data from the REPL history file.
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_UNKNOWN_BUILTIN_MODULE", "name": "err_unknown_builtin_module", "meta": { "added": [ "v8.0.0" ], "removed": [ "v9.0.0" ], "changes": [] }, "desc": "The 'ERR_UNKNOWN_BUILTIN_MODULE'
error code is used to identify a specific\nkind of internal Node.js error that should not typically be triggered by user\ncode. Instances of this error point to an internal bug within the Node.js\nbinary itself.
Used when a given value is out of the accepted range.
\n", "type": "module", "displayName": "ERR_VALUE_OUT_OF_RANGE" }, { "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.
These errors have never been released, but had been present on master between\nreleases.
\n", "modules": [ { "textRaw": "ERR_FS_WATCHER_ALREADY_STARTED", "name": "err_fs_watcher_already_started", "desc": "An attempt was made to start a watcher returned by fs.watch()
that has\nalready been started.
An attempt was made to initiate operations on a watcher returned by\nfs.watch()
that has not yet been started.
Occurs with multiple attempts to shutdown an HTTP/2 session.
\n", "type": "module", "displayName": "ERR_HTTP2_ALREADY_SHUTDOWN" }, { "textRaw": "ERR_HTTP2_ERROR", "name": "err_http2_error", "desc": "A non-specific HTTP/2 error has occurred.
\n", "type": "module", "displayName": "ERR_HTTP2_ERROR" }, { "textRaw": "ERR_INVALID_REPL_HISTORY", "name": "err_invalid_repl_history", "desc": "Used in the repl
in case the old history file is used and an error occurred\nwhile trying to read and parse it.
Used when an ES6 module loader hook specifies format: 'dynamic'
but does\nnot provide a dynamicInstantiate
hook.
Used to prevent an abort if a string decoder was set on the Socket.
\nconst Socket = require('net').Socket;\nconst instance = new Socket();\n\ninstance.setEncoding('utf8');\n
\n",
"type": "module",
"displayName": "ERR_STREAM_HAS_STRINGDECODER"
},
{
"textRaw": "ERR_STRING_TOO_LARGE",
"name": "err_string_too_large",
"desc": "An attempt has been made to create a string larger than the maximum allowed\nsize.
\n", "type": "module", "displayName": "ERR_STRING_TOO_LARGE" }, { "textRaw": "ERR_TTY_WRITABLE_NOT_READABLE", "name": "err_tty_writable_not_readable", "desc": "This Error
is thrown when a read is attempted on a TTY WriteStream
,\nsuch as process.stdout.on('data')
.
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.
For crypto only, Error
objects will include the OpenSSL error stack in a\nseparate property called opensslErrorStack
if it is available when the error\nis thrown.
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 an end user. For instance:
function MyError() {\n Error.captureStackTrace(this, MyError);\n}\n\n// Without passing MyError to captureStackTrace, the MyError\n// frame would show up in the .stack property. By passing\n// the constructor, we omit that frame, and retain all frames below it.\nnew MyError().stack;\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": "`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, or its 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.
System-level errors are generated as augmented Error
instances, which are\ndetailed here.
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 message.toString()
. 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.
A subclass of Error
that indicates the failure of an assertion. For details,\nsee Class: assert.AssertionError
.
A subclass of Error
that indicates that a provided argument was not within the\nset or range of acceptable values for a function; whether that is a numeric\nrange, or outside the set of options for a given function parameter.
require('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.
A subclass of Error
that indicates that an attempt is being made to access a\nvariable that is not defined. Such errors commonly indicate typos in code, or\nan otherwise broken program.
While 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 should always be considered a bug in the code\nor its dependencies.
A subclass of Error
that indicates that a program is not valid JavaScript.\nThese errors may only be generated and propagated as a result of code\nevaluation. Code evaluation may happen as a result of eval
, Function
,\nrequire
, or vm. These errors are almost always indicative of a broken\nprogram.
try {\n require('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.
A subclass of Error
that indicates that a provided argument is not an\nallowable type. For example, passing a function to a parameter which expects a\nstring would be considered a TypeError
.
require('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. The following variables may appear\nto be global but are not. They exist only in the scope of modules, see the\nmodule system documentation:
\n__dirname
__filename
exports
module
require()
The objects listed here are specific to Node.js. There are a number of\nbuilt-in objects that are part of the JavaScript language itself, which are\nalso globally accessible.
", "globals": [ { "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.
In browsers, the top-level scope is the global scope. This means that\nwithin the browser var something
will define a new global variable. In\nNode.js this is different. The top-level scope is not the global scope;\nvar something
inside a Node.js module will be local to that module.
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(url);\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(url, 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 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.
" } ], "miscs": [ { "textRaw": "__dirname", "name": "__dirname", "desc": "This variable may appear to be global but is not. See __dirname
.
This variable may appear to be global but is not. See __filename
.
This variable may appear to be global but is not. See exports
.
This variable may appear to be global but is not. See module
.
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:
\nLocale-sensitive or Unicode-aware functions in the ECMAScript Language\nSpecification:
\n\nAll functionality described in the ECMAScript Internationalization API\nSpecification (aka ECMA-402):
\nIntl
objectString.prototype.localeCompare()
and\nDate.prototype.toLocaleString()
require('buffer').transcode()
require('util').TextDecoder
RegExp
Unicode Property EscapesNode.js (and its underlying V8 engine) uses ICU to implement these features\nin native C/C++ code. However, some of them require a very large ICU data file\nin order to support all locales of the world. Because it is expected that most\nNode.js users will make use of only a small portion of ICU functionality, only\na subset of the full ICU data set is provided by Node.js by default. Several\noptions are provided for customizing and expanding 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
(default)--with-intl=full-icu
An overview of available Node.js and JavaScript features for each configure
\noption:
\n | none | \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
WHATWG URL Parser | \npartial (no IDN support) | \nfull | \nfull | \nfull | \n
require('buffer').transcode() | \nnone (function does not exist) | \nfull | \nfull | \nfull | \n
REPL | \npartial (inaccurate line editing) | \nfull | \nfull | \nfull | \n
require('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, most internationalization features mentioned above\nwill 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 \"M01\" on small-icu\n// Should print \"enero\"\n
\nThis mode provides a good balance between features and binary size, and it is\nthe default behavior if no --with-intl
flag is passed. The official binaries\nare also built in this mode.
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 /some/directory
, it can be made available to ICU\nthrough either:
The NODE_ICU_DATA
environment variable:
env NODE_ICU_DATA=/some/directory node\n
\nThe --icu-data-dir
CLI parameter:
node --icu-data-dir=/some/directory\n
\n(If both are specified, the --icu-data-dir
CLI parameter takes precedence.)
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 icudt6X[bl].dat
, where 6X
denotes\nthe intended ICU version, and b
or l
indicates the system's endianness.\nCheck \"ICU Data\" article in the ICU User Guide for other supported formats\nand more details on ICU data in general.
The 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. See\nBUILDING.md on how to compile a binary using this mode.
", "type": "module", "displayName": "Embed the entire ICU (`full-icu`)" } ], "type": "misc", "displayName": "Options for building Node.js" }, { "textRaw": "Detecting internationalization support", "name": "detecting_internationalization_support", "desc": "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.The assert
module provides a simple set of assertion tests that can be used to\ntest invariants.
A strict
and a legacy
mode exist, while it is recommended to only use\nstrict mode
.
For more information about the used equality comparisons see\nMDN's guide on equality comparisons and sameness.
", "classes": [ { "textRaw": "Class: assert.AssertionError", "type": "class", "name": "assert.AssertionError", "desc": "A subclass of Error
that indicates the failure of an assertion. All errors\nthrown by the assert
module 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 value in case e.g.,\nassert.strictEqual()
is used.expected
<any> Set to the expected value in case e.g.,\nassert.strictEqual()
is used.generatedMessage
<boolean> Indicates if the message was auto-generated\n(true
) or not.code
<string> This is always set to the string ERR_ASSERTION
to indicate\nthat the error is actually an assertion error.operator
<string> Set to the passed in operator value.const assert = require('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 [ERR_ASSERTION]');\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
"
}
]
}
],
"modules": [
{
"textRaw": "Strict mode",
"name": "strict_mode",
"meta": {
"added": [
"v9.9.0"
],
"changes": [
{
"version": "v9.9.0",
"pr-url": "https://github.com/nodejs/node/pull/17615",
"description": "Added error diffs to the strict mode"
},
{
"version": "v9.9.0",
"pr-url": "https://github.com/nodejs/node/pull/17002",
"description": "Added strict mode to the assert module."
}
]
},
"desc": "When using the strict mode
, any assert
function will use the equality used\nin the strict function mode. So assert.deepEqual()
will, for example,\nwork the same as assert.deepStrictEqual()
.
On top of that, error messages which involve objects produce an error diff\ninstead of displaying both objects. That is not the case for the legacy mode.
\nIt can be accessed using:
\nconst assert = require('assert').strict;\n
\nExample error diff:
\nconst assert = require('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 NODE_DISABLE_COLORS
environment variable.\nPlease note that this will also deactivate the colors in the REPL.
When accessing assert
directly instead of using the strict
property, the\nAbstract Equality Comparison will be used for any function without \"strict\"\nin its name, such as assert.deepEqual()
.
It can be accessed using:
\nconst assert = require('assert');\n
\nIt is recommended to use the strict mode
instead as the\nAbstract Equality Comparison can often have surprising results. This is\nespecially true for assert.deepEqual()
, where the comparison rules are\nlax:
// WARNING: This does not throw an AssertionError!\nassert.deepEqual(/a/gi, new Date());\n
",
"type": "module",
"displayName": "Legacy mode"
}
],
"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",
"optional": true
}
]
}
],
"desc": "An alias of assert.ok()
.
Strict mode
\nAn alias of assert.deepStrictEqual()
.
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.deepStrictEqual()
instead.
Tests for deep equality between the actual
and expected
parameters.\nPrimitive values are compared with the Abstract Equality Comparison\n( ==
).
Only enumerable \"own\" properties are considered. The\nassert.deepEqual()
implementation does not test the\n[[Prototype]]
of objects or enumerable own Symbol
\nproperties. For such checks, consider using assert.deepStrictEqual()
\ninstead. assert.deepEqual()
can have potentially surprising results. The\nfollowing example does not throw an AssertionError
because the properties on\nthe RegExp
object are not enumerable:
// WARNING: This does not throw an AssertionError!\nassert.deepEqual(/a/gi, new Date());\n
\nAn exception is made for Map
and Set
. Map
s and Set
s have their\ncontained items compared too, as expected.
\"Deep\" equality means that the enumerable \"own\" properties of child objects\nare evaluated also:
\nconst assert = require('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 = Object.create(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 Strict Equality Comparison.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.const assert = require('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 of the SameValue comparison\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 using the SameValue Comparison:\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
.
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()
.
(async () => {\n await assert.doesNotReject(\n async () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError\n );\n})();\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",
"optional": true
},
{
"textRaw": "`message` {string}",
"name": "message",
"type": "string",
"optional": true
}
]
}
],
"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 different\ntype, or if the error
parameter is undefined, the error is propagated back\nto 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:
assert.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...':
assert.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:
assert.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": []
},
"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",
"optional": true
}
]
}
],
"desc": "Strict mode
\nAn alias of assert.strictEqual()
.
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.strictEqual()
instead.
Tests shallow, coercive equality between the actual
and expected
parameters\nusing the Abstract Equality Comparison ( ==
).
const assert = require('assert');\n\nassert.equal(1, 1);\n// OK, 1 == 1\nassert.equal(1, '1');\n// OK, 1 == '1'\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 error\nmessage. If the message
parameter is an instance of an Error
then it\nwill be thrown instead of the AssertionError
.
const assert = require('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.
const assert = require('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:
function 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.
const assert = require('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.notDeepEqual(actual, expected[, message])",
"type": "method",
"name": "notDeepEqual",
"meta": {
"added": [
"v0.1.21"
],
"changes": [
{
"version": "v9.0.0",
"pr-url": "https://github.com/nodejs/node/pull/15001",
"description": "The `Error` names and messages are now properly compared"
},
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/12142",
"description": "The `Set` and `Map` content is also compared"
},
{
"version": "v6.4.0, v4.7.1",
"pr-url": "https://github.com/nodejs/node/pull/8002",
"description": "Typed array slices are handled correctly now."
},
{
"version": "v6.1.0, v4.5.0",
"pr-url": "https://github.com/nodejs/node/pull/6432",
"description": "Objects with circular references can be used as inputs now."
},
{
"version": "v5.10.1, v4.4.3",
"pr-url": "https://github.com/nodejs/node/pull/5910",
"description": "Handle non-`Uint8Array` typed arrays correctly."
}
]
},
"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",
"optional": true
}
]
}
],
"desc": "Strict mode
\nAn alias of assert.notDeepStrictEqual()
.
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.notDeepStrictEqual()
instead.
Tests for any deep inequality. Opposite of assert.deepEqual()
.
const assert = require('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 = Object.create(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 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 strict inequality. Opposite of assert.deepStrictEqual()
.
const assert = require('assert').strict;\n\nassert.notDeepStrictEqual({ a: 1 }, { a: '1' });\n// OK\n
\nIf the values are deeply and strictly equal, an AssertionError
is thrown with\na message
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
.
Strict mode
\nAn alias of assert.notStrictEqual()
.
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.notStrictEqual()
instead.
Tests shallow, coercive inequality with the Abstract Equality Comparison\n( !=
).
const assert = require('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
property\nset equal to 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
.
Tests strict inequality between the actual
and expected
parameters as\ndetermined by the SameValue Comparison.
const assert = require('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 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 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.
const assert = require('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\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",
"optional": true
},
{
"textRaw": "`message` {string}",
"name": "message",
"type": "string",
"optional": true
}
]
}
],
"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
if\nthe asyncFn
fails to reject.
(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
\nassert.rejects(\n Promise.reject(new Error('Wrong value')),\n Error\n).then(() => {\n // ...\n});\n
\nNote that error
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 the SameValue Comparison.
const assert = require('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
\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:
\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 // Note that 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 otherErr.code = 404;\n throw otherErr;\n },\n err // This tests for `message`, `name` and `code`.\n);\n
\nValidate instanceof using constructor:
\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.
assert.throws(\n () => {\n throw new Error('Wrong value');\n },\n /^Error: Wrong value$/\n);\n
\nCustom error validation:
\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n function(err) {\n if ((err instanceof Error) && /value/.test(err)) {\n return true;\n }\n },\n 'unexpected error'\n);\n
\nNote that error
cannot be a string. If a string is provided as the second\nargument, then error
is assumed to be omitted and the string will be used for\nmessage
instead. This can lead to easy-to-miss mistakes. Using the same\nmessage as the thrown error message is going to result in an\nERR_AMBIGUOUS_ARGUMENT
error. Please read the example below carefully if using\na string as the second argument gets considered:
function throwingFirst() {\n throw new Error('First');\n}\nfunction throwingSecond() {\n throw new Error('Second');\n}\nfunction notThrowing() {}\n\n// The second argument is a string and the input function threw an Error.\n// The first case will not throw as it does not match for the error message\n// thrown by the input function!\nassert.throws(throwingFirst, 'Second');\n// In the next example the message has no benefit over the message from the\n// error and since it is not clear if the user intended to actually match\n// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.\nassert.throws(throwingSecond, 'Second');\n// TypeError [ERR_AMBIGUOUS_ARGUMENT]\n\n// The string is only used (as message) in case the function does not throw:\nassert.throws(notThrowing, 'Second');\n// AssertionError [ERR_ASSERTION]: Missing expected exception: Second\n\n// If it was intended to match for the error message do this instead:\n// It does not throw because the error messages match.\nassert.throws(throwingSecond, /Second$/);\n\n// If the error message does not match, the error from within the function is\n// not caught.\nassert.throws(throwingFirst, /Second$/);\n// Error: First\n// at throwingFirst (repl:2:9)\n
\nDue to the confusing notation, it is recommended not to use a string as the\nsecond argument. This might lead to difficult-to-spot errors.
" } ], "type": "module", "displayName": "Assert" }, { "textRaw": "Async Hooks", "name": "async_hooks", "introduced_in": "v8.1.0", "stability": 1, "stabilityText": "Experimental", "desc": "The async_hooks
module provides an API to register callbacks tracking the\nlifetime of asynchronous resources created inside a Node.js application.\nIt can be accessed using:
const async_hooks = require('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, for example, 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.
\nconst async_hooks = require('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 (e.g. TCPWrap), and will be called exactly 1\n// time for requests (e.g. 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 an AsyncWrap instance 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
",
"methods": [
{
"textRaw": "async_hooks.createHook(callbacks)",
"type": "method",
"name": "createHook",
"meta": {
"added": [
"v8.1.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {AsyncHook} Instance used for disabling and enabling hooks",
"name": "return",
"type": "AsyncHook",
"desc": "Instance used for disabling and enabling 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": "`destroy` {Function} The [`destroy` callback][].",
"name": "destroy",
"type": "Function",
"desc": "The [`destroy` callback][]."
}
]
}
]
}
],
"desc": "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.
const async_hooks = require('async_hooks');\n\nconst asyncHook = async_hooks.createHook({\n init(asyncId, type, triggerAsyncId, resource) { },\n destroy(asyncId) { }\n});\n
\nNote that the 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
",
"modules": [
{
"textRaw": "Error Handling",
"name": "error_handling",
"desc": "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 AsyncHooks callbacks", "name": "printing_in_asynchooks_callbacks", "desc": "Because printing to the console is an asynchronous operation, console.log()
\nwill cause the AsyncHooks callbacks to be called. Using console.log()
or\nsimilar asynchronous operations inside an AsyncHooks callback function will thus\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 AsyncHooks recursively because\nit is synchronous.
const fs = require('fs');\nconst util = require('util');\n\nfunction debug(...args) {\n // Use a function like this one when debugging inside an AsyncHooks 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 AsyncHooks itself. The logging should then be skipped when\nit was the logging itself that caused AsyncHooks callback to call. By\ndoing this the otherwise infinite recursion is broken.
", "type": "module", "displayName": "Printing in AsyncHooks callbacks" } ] }, { "textRaw": "asyncHook.enable()", "type": "method", "name": "enable", "signatures": [ { "return": { "textRaw": "Returns: {AsyncHook} A reference to `asyncHook`.", "name": "return", "type": "AsyncHook", "desc": "A reference to `asyncHook`." }, "params": [] } ], "desc": "Enable the callbacks for a given AsyncHook
instance. If no callbacks are\nprovided enabling is a noop.
The AsyncHook
instance is disabled by default. If the AsyncHook
instance\nshould be enabled immediately after creation, the following pattern can be used.
const async_hooks = require('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.
const async_hooks = require('async_hooks');\n\nconsole.log(async_hooks.executionAsyncId()); // 1 - bootstrap\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 (i.e. process.nextTick()) because all\n // callbacks passed to .listen() are wrapped in a nextTick().\n async_hooks.executionAsyncId();\n});\n
\nNote that promise 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
\nNote that promise 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.
\nrequire('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.
FSEVENTWRAP, FSREQCALLBACK, GETADDRINFOREQWRAP, GETNAMEINFOREQWRAP, HTTPPARSER,\nJSSTREAM, PIPECONNECTWRAP, PIPEWRAP, PROCESSWRAP, QUERYWRAP, SHUTDOWNWRAP,\nSIGNALWRAP, STATWATCHER, TCPCONNECTWRAP, TCPSERVERWRAP, TCPWRAP, TTYWRAP,\nUDPSENDWRAP, UDPWRAP, WRITEWRAP, ZLIB, SSLCONNECTION, PBKDF2REQUEST,\nRANDOMBYTESREQUEST, TLSWRAP, Microtask, Timeout, Immediate, TickObject\n
\nThere 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
:
async_hooks.createHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = async_hooks.executionAsyncId();\n fs.writeSync(\n 1, `${type}(${asyncId}): trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n }\n}).enable();\n\nrequire('net').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. This can contain useful information that can vary based on\nthe value of type
. For instance, for the GETADDRINFOREQWRAP
resource type,\nresource
provides the hostname used when looking up the IP address for the\nhost in net.Server.listen()
. The API for accessing this information is\ncurrently not considered public, but using the Embedder API, users can provide\nand document their own resource objects. For example, such a resource object\ncould contain the SQL query being executed.
In the case of Promises, the resource
object will have promise
property\nthat refers to the Promise
that is being initialized, and an\nisChainedPromise
property, set to true
if the promise has a parent promise,\nand false
otherwise. For example, in the case of b = a.then(handler)
, a
is\nconsidered a parent Promise
of b
. Here, b
is considered a chained promise.
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 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.
let 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 1,\n `${indentStr}${type}(${asyncId}):` +\n ` trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n },\n before(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeFileSync('log.out',\n `${indentStr}before: ${asyncId}\\n`, { flag: 'a' });\n indent += 2;\n },\n after(asyncId) {\n indent -= 2;\n const indentStr = ' '.repeat(indent);\n fs.writeFileSync('log.out',\n `${indentStr}after: ${asyncId}\\n`, { flag: 'a' });\n },\n destroy(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeFileSync('log.out',\n `${indentStr}destroy: ${asyncId}\\n`, { flag: 'a' });\n },\n}).enable();\n\nrequire('net').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:
Timeout(7) -> TickObject(6) -> root(1)\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\nhostname is a synchronous operation, but to maintain a completely asynchronous\nAPI the user's callback is placed in a process.nextTick()
.
The graph only shows when a resource was created, not why, so to track\nthe why use triggerAsyncId
.
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.
Called when the resolve
function passed to the Promise
constructor is\ninvoked (either directly or through other means of resolving a promise).
Note that 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"
}
],
"type": "module",
"displayName": "Overview"
}
],
"type": "module",
"displayName": "Public API"
},
{
"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.
const ah = require('async_hooks');\nPromise.resolve(1729).then(() => {\n console.log(`eid ${ah.executionAsyncId()} tid ${ah.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 note that\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:
const ah = require('async_hooks');\nah.createHook({ init() {} }).enable(); // forces PromiseHooks to be enabled.\nPromise.resolve(1729).then(() => {\n console.log(`eid ${ah.executionAsyncId()} tid ${ah.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\nAsyncWrap
JavaScript API so that all the appropriate callbacks are called.
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.
const { AsyncResource, executionAsyncId } = require('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
",
"methods": [
{
"textRaw": "asyncResource.runInAsyncScope(fn[, thisArg, ...args])",
"type": "method",
"name": "runInAsyncScope",
"meta": {
"added": [
"v9.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`fn` {Function} The function to call in the execution context of this async resource.",
"name": "fn",
"type": "Function",
"desc": "The function to call in the execution context of this async resource."
},
{
"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.",
"optional": true
},
{
"textRaw": "`...args` {any} Optional arguments to pass to the function.",
"name": "...args",
"type": "any",
"desc": "Optional arguments to pass to the function.",
"optional": true
}
]
}
],
"desc": "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.emitBefore()", "type": "method", "name": "emitBefore", "meta": { "deprecated": [ "v9.6.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`asyncResource.runInAsyncScope()`][] instead.", "signatures": [ { "params": [] } ], "desc": "Call all before
callbacks to notify that a new asynchronous execution context\nis being entered. If nested calls to emitBefore()
are made, the stack of\nasyncId
s will be tracked and properly unwound.
before
and after
calls must be unwound in the same order that they\nare called. Otherwise, an unrecoverable exception will occur and the process\nwill abort. For this reason, the emitBefore
and emitAfter
APIs are\nconsidered deprecated. Please use runInAsyncScope
, as it provides a much safer\nalternative.
Call all after
callbacks. If nested calls to emitBefore()
were made, then\nmake sure the stack is unwound properly. Otherwise an error will be thrown.
If the user's callback throws an exception, emitAfter()
will automatically be\ncalled for all asyncId
s on the stack if the error is handled by a domain or\n'uncaughtException'
handler.
before
and after
calls must be unwound in the same order that they\nare called. Otherwise, an unrecoverable exception will occur and the process\nwill abort. For this reason, the emitBefore
and emitAfter
APIs are\nconsidered deprecated. Please use runInAsyncScope
, as it provides a much safer\nalternative.
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.
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": "JavaScript Embedder API"
}
],
"type": "module",
"displayName": "Async Hooks"
},
{
"textRaw": "Buffer",
"name": "buffer",
"introduced_in": "v0.1.90",
"stability": 2,
"stabilityText": "Stable",
"desc": "Prior to the introduction of TypedArray
, the JavaScript language had no\nmechanism for reading or manipulating streams of binary data. The Buffer
class\nwas introduced as part of the Node.js API to enable interaction with octet\nstreams in TCP streams, file system operations, and other contexts.
With TypedArray
now available, the Buffer
class implements the\nUint8Array
API in a manner that is more optimized and suitable for Node.js.
Instances of the Buffer
class are similar to arrays of integers but\ncorrespond to fixed-sized, raw memory allocations outside the V8 heap.\nThe size of the Buffer
is established when it is created and cannot be\nchanged.
The Buffer
class is within the global scope, making it unlikely that one\nwould need to ever use require('buffer').Buffer
.
// Creates a zero-filled Buffer of length 10.\nconst buf1 = Buffer.alloc(10);\n\n// Creates a Buffer of length 10, filled with 0x1.\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 either fill() or write().\nconst buf3 = Buffer.allocUnsafe(10);\n\n// Creates a Buffer containing [0x1, 0x2, 0x3].\nconst buf4 = Buffer.from([1, 2, 3]);\n\n// Creates a Buffer containing UTF-8 bytes [0x74, 0xc3, 0xa9, 0x73, 0x74].\nconst buf5 = Buffer.from('tést');\n\n// Creates a Buffer containing Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].\nconst buf6 = Buffer.from('tést', 'latin1');\n
",
"modules": [
{
"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
. While 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
. Starting in Node.js 8.0.0, Buffer(num)
and\nnew Buffer(num)
will 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
that\nshares 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.
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.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()
may be allocated off\na shared internal memory pool if size
is less than or equal to half\nBuffer.poolSize
. Instances returned by Buffer.allocUnsafeSlow()
never\nuse the shared internal memory 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, including buffers returned by new Buffer(size)
,\nBuffer.allocUnsafe()
, Buffer.allocUnsafeSlow()
, and new SlowBuffer(size)
. Use of this flag can have a significant negative impact on\nperformance. Use of the --zero-fill-buffers
option is recommended only when\nnecessary to enforce that newly allocated Buffer
instances cannot contain old\ndata 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 memory\ncan allow this old data to be leaked when the Buffer
memory is read.
While there are clear performance advantages to using Buffer.allocUnsafe()
,\nextra care must be taken in order to avoid introducing security\nvulnerabilities into an application.
When string data is stored in or extracted out of a Buffer
instance, a\ncharacter encoding may be specified.
const buf = Buffer.from('hello world', 'ascii');\n\nconsole.log(buf.toString('hex'));\n// Prints: 68656c6c6f20776f726c64\nconsole.log(buf.toString('base64'));\n// Prints: aGVsbG8gd29ybGQ=\n\nconsole.log(Buffer.from('fhqwhgads', 'ascii'));\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
\nThe character encodings currently supported by Node.js include:
\n'ascii'
- For 7-bit ASCII data only. This encoding is fast and will strip\nthe high bit if set.
'utf8'
- Multibyte encoded Unicode characters. Many web pages and other\ndocument formats use UTF-8.
'utf16le'
- 2 or 4 bytes, little-endian encoded Unicode characters.\nSurrogate pairs (U+10000 to U+10FFFF) are supported.
'ucs2'
- Alias of 'utf16le'
.
'base64'
- Base64 encoding. When creating a Buffer
from a string,\nthis encoding will also correctly accept \"URL and Filename Safe Alphabet\" as\nspecified in RFC4648, Section 5.
'latin1'
- A way of encoding the Buffer
into a one-byte encoded string\n(as defined by the IANA in RFC1345,\npage 63, to be the Latin-1 supplement block and C0/C1 control codes).
'binary'
- Alias for 'latin1'
.
'hex'
- Encode each byte as two hexadecimal characters.
Modern 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 Uint8Array
instances. However, there are subtle\nincompatibilities with TypedArray
. For example, while\nArrayBuffer#slice()
creates a copy of the slice, the implementation of\nBuffer#slice()
creates a view over the existing Buffer
\nwithout copying, making Buffer#slice()
far more efficient.
It is also possible to create new TypedArray
instances from a Buffer
with\nthe following caveats:
The Buffer
object's memory is copied to the TypedArray
, not shared.
The Buffer
object's memory is interpreted as an array of distinct\nelements, and not as a byte array of the target type. That is,\nnew Uint32Array(Buffer.from([1, 2, 3, 4]))
creates a 4-element Uint32Array
\nwith elements [1, 2, 3, 4]
, not a Uint32Array
with a single element\n[0x1020304]
or [0x4030201]
.
It is possible to create a new Buffer
that shares the same allocated memory as\na TypedArray
instance by using the TypeArray
object's .buffer
property.
const arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Copies the contents of `arr`\nconst buf1 = Buffer.from(arr);\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
\nNote that when 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.
const 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:
const buf = Buffer.from([1, 2, 3]);\n\n// Prints:\n// 1\n// 2\n// 3\nfor (const b of buf) {\n console.log(b);\n}\n
\nAdditionally, the buf.values()
, buf.keys()
, and\nbuf.entries()
methods can be used to create iterators.
Note that buffer.constants
is a property on the buffer
module returned by\nrequire('buffer')
, not on the Buffer
global or a Buffer
instance.
On 32-bit architectures, this value is (2^30)-1
(~1GB).\nOn 64-bit architectures, this value is (2^31)-1
(~2GB).
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" } ], "classes": [ { "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.
const buf = Buffer.alloc(5);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00>\n
\nAllocates a new Buffer
of size
bytes. If size
is larger than\nbuffer.constants.MAX_LENGTH
or smaller than 0, ERR_INVALID_OPT_VALUE
is\nthrown. A zero-length Buffer
is created if size
is 0.
If fill
is specified, the allocated Buffer
will be initialized by calling\nbuf.fill(fill)
.
const 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)
.
const 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 significantly slower than the alternative\nBuffer.allocUnsafe()
but ensures that the newly created Buffer
instance\ncontents will never contain sensitive data.
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_INVALID_OPT_VALUE
is\nthrown. 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 Buffer.alloc()
instead to initialize\nBuffer
instances with zeroes.
const 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.
Note that 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()
and the deprecated\nnew Buffer(size)
constructor only when size
is less than or equal to\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_INVALID_OPT_VALUE
is\nthrown. 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 4KB 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 persistent 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.
// Need to keep around a few small chunks of memory\nconst store = [];\n\nsocket.on('readable', () => {\n const data = socket.read();\n\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
\nBuffer.allocUnsafeSlow()
should be used only as a last resort after a\ndeveloper has observed undue memory retention in their applications.
A TypeError
will be thrown if size
is not a number.
Returns the actual byte length of a string. This is not the same as\nString.prototype.length
since that returns the number of characters in\na string.
For 'base64'
and 'hex'
, this function assumes valid input. For strings that\ncontain non-Base64/Hex-encoded data (e.g. whitespace), the return value might be\ngreater than the length of a Buffer
created from the string.
const 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 actual byte length is returned.
Compares buf1
to buf2
typically for the purpose of sorting arrays of\nBuffer
instances. This is equivalent to calling\nbuf1.compare(buf2)
.
const 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": "Class 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 concat.",
"name": "list",
"type": "Buffer[] | Uint8Array[]",
"desc": "List of `Buffer` or [`Uint8Array`] instances to concat."
},
{
"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.",
"optional": true
}
]
}
],
"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
. This however causes an additional loop to be executed in order to\ncalculate the totalLength
, so it is faster to provide the length explicitly if\nit is already known.
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
.
// 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
"
},
{
"textRaw": "Class 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 octets.
// Creates a new Buffer containing UTF-8 bytes of the string 'buffer'\nconst buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);\n
\nA TypeError
will be thrown if array
is not an Array
.
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
.
const 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
.
const 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
.
Copies the passed buffer
data onto a new Buffer
instance.
const 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
.
Creates a new Buffer
containing string
. The encoding
parameter identifies\nthe character encoding of string
.
const 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('ascii'));\n// Prints: this is a tC)st\n
\nA TypeError
will be thrown if string
is not a string.
For objects whose valueOf()
function returns a value not strictly equal to\nobject
, returns Buffer.from(object.valueOf(), offsetOrEncoding, length)
.
const 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](), offsetOrEncoding, length)
.
class 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
"
},
{
"textRaw": "Class Method: Buffer.isBuffer(obj)",
"type": "classMethod",
"name": "isBuffer",
"meta": {
"added": [
"v0.1.101"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {boolean}",
"name": "return",
"type": "boolean"
},
"params": [
{
"textRaw": "`obj` {Object}",
"name": "obj",
"type": "Object"
}
]
}
],
"desc": "Returns true
if obj
is a Buffer
, false
otherwise.
Returns true
if encoding
contains a supported character encoding, or false
\notherwise.
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
- that is, getting returns undefined
and\nsetting does nothing.
// Copy an ASCII string into a `Buffer` one byte at a time.\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('ascii'));\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": "const 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` on the underlying `ArrayBuffer` object based on which this `Buffer` object is created.",
"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 doesn't start from a zero offset on the underlying ArrayBuffer
.
This can cause problems when accessing the underlying ArrayBuffer
directly\nusing buf.buffer
, as the first bytes in this ArrayBuffer
may be unrelated\nto the buf
object itself.
A common issue is when casting a Buffer
object to a TypedArray
object,\nin this case one needs to specify the byteOffset
correctly:
// Create a buffer smaller than `Buffer.poolSize`.\nconst nodeBuffer = new Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);\n\n// When casting the Node.js Buffer to an Int8 TypedArray remember to use the\n// byteOffset.\nnew Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);\n
",
"shortDesc": "The `byteOffset` on the underlying `ArrayBuffer` object based on which this `Buffer` object is created."
},
{
"textRaw": "`length` {integer}",
"type": "integer",
"name": "length",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"desc": "Returns the amount of memory allocated for buf
in bytes. Note that this\ndoes not necessarily reflect the amount of \"usable\" data within buf
.
// Create a `Buffer` and write a shorter ASCII string to it.\n\nconst buf = Buffer.alloc(1234);\n\nconsole.log(buf.length);\n// Prints: 1234\n\nbuf.write('some string', 0, 'ascii');\n\nconsole.log(buf.length);\n// Prints: 1234\n
\nWhile the length
property is not immutable, changing the value of length
\ncan result in undefined and inconsistent behavior. Applications that wish to\nmodify the length of a Buffer
should therefore treat length
as read-only and\nuse buf.slice()
to create a new Buffer
.
let buf = Buffer.allocUnsafe(10);\n\nbuf.write('abcdefghj', 0, 'ascii');\n\nconsole.log(buf.length);\n// Prints: 10\n\nbuf = buf.slice(0, 5);\n\nconsole.log(buf.length);\n// Prints: 5\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.const 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.
const 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
.
// 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\nconsole.log(buf2.toString('ascii', 0, 25));\n// Prints: !!!!!!!!qrst!!!!!!!!!!!!!\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 of\nbuf
.
// 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} A `Buffer` or [`Uint8Array`] with which to compare `buf`.",
"name": "otherBuffer",
"type": "Buffer",
"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.
const 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|integer} The value with which to fill `buf`.",
"name": "value",
"type": "string|Buffer|integer",
"desc": "The value with which to fill `buf`."
},
{
"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`.",
"optional": true
},
{
"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).",
"optional": true
},
{
"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.",
"optional": true
}
]
}
],
"desc": "Fills buf
with the specified value
. If the offset
and end
are not given,\nthe entire buf
will be filled:
// 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
\nvalue
is coerced to a uint32
value if it is not a string or integer.
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:
// Fill a `Buffer` with a two-byte character.\n\nconsole.log(Buffer.allocUnsafe(3).fill('\\u0222'));\n// Prints: <Buffer c8 a2 c8>\n
\nIf value
contains invalid characters, it is truncated; if no valid\nfill data remains, an exception is thrown:
const 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|integer} What to search for.",
"name": "value",
"type": "string|Buffer|integer",
"desc": "What to search for."
},
{
"textRaw": "`byteOffset` {integer} Where to begin searching in `buf`. **Default:** `0`.",
"name": "byteOffset",
"type": "integer",
"default": "`0`",
"desc": "Where to begin searching in `buf`.",
"optional": true
},
{
"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.",
"optional": true
}
]
}
],
"desc": "Equivalent to buf.indexOf() !== -1
.
const 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`. **Default:** `0`.",
"name": "byteOffset",
"type": "integer",
"default": "`0`",
"desc": "Where to begin searching in `buf`.",
"optional": true
},
{
"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`.",
"optional": true
}
]
}
],
"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.slice()
.value
will be interpreted as an unsigned 8-bit integer\nvalue between 0
and 255
.const 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#indexOf()
.
const 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).
const 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`."
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]
},
"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`. **Default:** [`buf.length`]` - 1`.",
"name": "byteOffset",
"type": "integer",
"default": "[`buf.length`]` - 1`",
"desc": "Where to begin searching in `buf`.",
"optional": true
},
{
"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`.",
"optional": true
}
]
}
],
"desc": "Identical to buf.indexOf()
, except the last occurrence of value
is found\nrather than the first occurrence.
const 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#lastIndexOf()
.
const 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 64-bit double from buf
at the specified offset
with specified\nendian format (readDoubleBE()
returns big endian, readDoubleLE()
returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleBE(0));\n// Prints: 8.20788039913184e-304\nconsole.log(buf.readDoubleLE(0));\n// Prints: 5.447603722011605e-270\nconsole.log(buf.readDoubleLE(1));\n// Throws ERR_OUT_OF_RANGE\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",
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]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 8`."
}
]
}
],
"desc": "Reads a 64-bit double from buf
at the specified offset
with specified\nendian format (readDoubleBE()
returns big endian, readDoubleLE()
returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleBE(0));\n// Prints: 8.20788039913184e-304\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"
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"changes": [
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"version": "v10.0.0",
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]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a 32-bit float from buf
at the specified offset
with specified\nendian format (readFloatBE()
returns big endian, readFloatLE()
returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatBE(0));\n// Prints: 2.387939260590663e-38\nconsole.log(buf.readFloatLE(0));\n// Prints: 1.539989614439558e-36\nconsole.log(buf.readFloatLE(1));\n// Throws ERR_OUT_OF_RANGE\n
"
},
{
"textRaw": "buf.readFloatLE(offset)",
"type": "method",
"name": "readFloatLE",
"meta": {
"added": [
"v0.11.15"
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"changes": [
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"version": "v10.0.0",
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]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a 32-bit float from buf
at the specified offset
with specified\nendian format (readFloatBE()
returns big endian, readFloatLE()
returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatBE(0));\n// Prints: 2.387939260590663e-38\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",
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}
]
},
"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`.",
"name": "offset",
"type": "integer",
"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.
const 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": [
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"changes": [
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}
]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads a signed 16-bit integer from buf
at the specified offset
with\nthe specified endian format (readInt16BE()
returns big endian,\nreadInt16LE()
returns little endian).
Integers read from a Buffer
are interpreted as two's complement signed values.
const buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16BE(0));\n// Prints: 5\nconsole.log(buf.readInt16LE(0));\n// Prints: 1280\nconsole.log(buf.readInt16LE(1));\n// Throws ERR_OUT_OF_RANGE\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",
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}
]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads a signed 16-bit integer from buf
at the specified offset
with\nthe specified endian format (readInt16BE()
returns big endian,\nreadInt16LE()
returns little endian).
Integers read from a Buffer
are interpreted as two's complement signed values.
const buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16BE(0));\n// Prints: 5\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",
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}
]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a signed 32-bit integer from buf
at the specified offset
with\nthe specified endian format (readInt32BE()
returns big endian,\nreadInt32LE()
returns little endian).
Integers read from a Buffer
are interpreted as two's complement signed values.
const buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32BE(0));\n// Prints: 5\nconsole.log(buf.readInt32LE(0));\n// Prints: 83886080\nconsole.log(buf.readInt32LE(1));\n// Throws ERR_OUT_OF_RANGE\n
"
},
{
"textRaw": "buf.readInt32LE(offset)",
"type": "method",
"name": "readInt32LE",
"meta": {
"added": [
"v0.5.5"
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"changes": [
{
"version": "v10.0.0",
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}
]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads a signed 32-bit integer from buf
at the specified offset
with\nthe specified endian format (readInt32BE()
returns big endian,\nreadInt32LE()
returns little endian).
Integers read from a Buffer
are interpreted as two's complement signed values.
const buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32BE(0));\n// Prints: 5\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": [
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"changes": [
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]
},
"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 two's complement signed value. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntLE(0, 6).toString(16));\n// Prints: -546f87a9cbee\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"
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"changes": [
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"version": "v10.0.0",
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]
},
"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 two's complement signed value. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntLE(0, 6).toString(16));\n// Prints: -546f87a9cbee\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.readUInt8(offset)",
"type": "method",
"name": "readUInt8",
"meta": {
"added": [
"v0.5.0"
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"changes": [
{
"version": "v10.0.0",
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}
]
},
"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`.",
"name": "offset",
"type": "integer",
"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
.
const 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": [
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"changes": [
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]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads an unsigned 16-bit integer from buf
at the specified offset
with\nspecified endian format (readUInt16BE()
returns big endian, readUInt16LE()
\nreturns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16BE(0).toString(16));\n// Prints: 1234\nconsole.log(buf.readUInt16LE(0).toString(16));\n// Prints: 3412\nconsole.log(buf.readUInt16BE(1).toString(16));\n// Prints: 3456\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.readUInt16LE(offset)",
"type": "method",
"name": "readUInt16LE",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"version": "v10.0.0",
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]
},
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 2`."
}
]
}
],
"desc": "Reads an unsigned 16-bit integer from buf
at the specified offset
with\nspecified endian format (readUInt16BE()
returns big endian, readUInt16LE()
\nreturns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16BE(0).toString(16));\n// Prints: 1234\nconsole.log(buf.readUInt16LE(0).toString(16));\n// Prints: 3412\nconsole.log(buf.readUInt16BE(1).toString(16));\n// Prints: 3456\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": "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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads an unsigned 32-bit integer from buf
at the specified offset
with\nspecified endian format (readUInt32BE()
returns big endian,\nreadUInt32LE()
returns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32BE(0).toString(16));\n// Prints: 12345678\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.readUInt32LE(offset)",
"type": "method",
"name": "readUInt32LE",
"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`.",
"name": "offset",
"type": "integer",
"desc": "Number of bytes to skip before starting to read. Must satisfy `0 <= offset <= buf.length - 4`."
}
]
}
],
"desc": "Reads an unsigned 32-bit integer from buf
at the specified offset
with\nspecified endian format (readUInt32BE()
returns big endian,\nreadUInt32LE()
returns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32BE(0).toString(16));\n// Prints: 12345678\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": "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 integer. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readUIntLE(0, 6).toString(16));\n// Prints: ab9078563412\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": "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 integer. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readUIntLE(0, 6).toString(16));\n// Prints: ab9078563412\nconsole.log(buf.readUIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE\n
"
},
{
"textRaw": "buf.slice([start[, end]])",
"type": "method",
"name": "slice",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"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."
}
]
},
"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.",
"optional": true
},
{
"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).",
"optional": true
}
]
}
],
"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
.
Modifying the new Buffer
slice will modify the memory in the original Buffer
\nbecause the allocated memory of the two objects overlap.
// 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.slice(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.
const buf = Buffer.from('buffer');\n\nconsole.log(buf.slice(-6, -1).toString());\n// Prints: buffe\n// (Equivalent to buf.slice(0, 5))\n\nconsole.log(buf.slice(-6, -2).toString());\n// Prints: buff\n// (Equivalent to buf.slice(0, 4))\n\nconsole.log(buf.slice(-5, -2).toString());\n// Prints: uff\n// (Equivalent to buf.slice(1, 4))\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
is\nnot a multiple of 2.
const 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:
const 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
is\nnot a multiple of 4.
const 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.
const 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
\nNote that JavaScript cannot encode 64-bit integers. This method is intended\nfor working with 64-bit floats.
" }, { "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.
const 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.data) :\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.",
"optional": true
},
{
"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.",
"optional": true
},
{
"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).",
"optional": true
}
]
}
],
"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
.
The maximum length of a string instance (in UTF-16 code units) is available\nas buffer.constants.MAX_STRING_LENGTH
.
const 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('ascii'));\n// Prints: abcdefghijklmnopqrstuvwxyz\nconsole.log(buf1.toString('ascii', 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.
const 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`.",
"optional": true
},
{
"textRaw": "`length` {integer} Number of bytes to write. **Default:** `buf.length - offset`.",
"name": "length",
"type": "integer",
"default": "`buf.length - offset`",
"desc": "Number of bytes to write.",
"optional": true
},
{
"textRaw": "`encoding` {string} The character encoding of `string`. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "The character encoding of `string`.",
"optional": true
}
]
}
],
"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.
const 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
"
},
{
"textRaw": "buf.writeDoubleBE(value, offset)",
"type": "method",
"name": "writeDoubleBE",
"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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeDoubleBE()
writes big endian, writeDoubleLE()
writes little\nendian). value
should be a valid 64-bit double. Behavior is undefined when\nvalue
is anything other than a 64-bit double.
const 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\nbuf.writeDoubleLE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>\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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeDoubleBE()
writes big endian, writeDoubleLE()
writes little\nendian). value
should be a valid 64-bit double. Behavior is undefined when\nvalue
is anything other than a 64-bit double.
const 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\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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeFloatBE()
writes big endian, writeFloatLE()
writes little\nendian). value
should be a valid 32-bit float. Behavior is undefined when\nvalue
is anything other than a 32-bit float.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 4f 4a fe bb>\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer bb fe 4a 4f>\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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeFloatBE()
writes big endian, writeFloatLE()
writes little\nendian). value
should be a valid 32-bit float. Behavior is undefined when\nvalue
is anything other than a 32-bit float.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 4f 4a fe bb>\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`.",
"name": "offset",
"type": "integer",
"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
should 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.
const 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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeInt16BE()
writes big endian, writeInt16LE()
writes little\nendian). value
should be a valid signed 16-bit integer. Behavior is\nundefined when value
is anything other than a signed 16-bit integer.
value
is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt16BE(0x0102, 0);\nbuf.writeInt16LE(0x0304, 2);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 04 03>\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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeInt16BE()
writes big endian, writeInt16LE()
writes little\nendian). value
should be a valid signed 16-bit integer. Behavior is\nundefined when value
is anything other than a signed 16-bit integer.
value
is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt16BE(0x0102, 0);\nbuf.writeInt16LE(0x0304, 2);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeInt32BE()
writes big endian, writeInt32LE()
writes little\nendian). value
should be a valid signed 32-bit integer. Behavior is\nundefined when value
is anything other than a signed 32-bit integer.
value
is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(8);\n\nbuf.writeInt32BE(0x01020304, 0);\nbuf.writeInt32LE(0x05060708, 4);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04 08 07 06 05>\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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeInt32BE()
writes big endian, writeInt32LE()
writes little\nendian). value
should be a valid signed 32-bit integer. Behavior is\nundefined when value
is anything other than a signed 32-bit integer.
value
is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(8);\n\nbuf.writeInt32BE(0x01020304, 0);\nbuf.writeInt32LE(0x05060708, 4);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04 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
.\nSupports up to 48 bits of accuracy. Behavior is undefined when value
is\nanything other than a signed integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n\nbuf.writeIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\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
.\nSupports up to 48 bits of accuracy. Behavior is undefined when value
is\nanything other than a signed integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\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": "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`.",
"name": "offset",
"type": "integer",
"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
should be a\nvalid unsigned 8-bit integer. Behavior is undefined when value
is anything\nother than an unsigned 8-bit integer.
const 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": "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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeUInt16BE()
writes big endian, writeUInt16LE()
writes little\nendian). value
should be a valid unsigned 16-bit integer. Behavior is\nundefined when value
is anything other than an unsigned 16-bit integer.
const 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\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer ad de ef be>\n
"
},
{
"textRaw": "buf.writeUInt16LE(value, offset)",
"type": "method",
"name": "writeUInt16LE",
"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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeUInt16BE()
writes big endian, writeUInt16LE()
writes little\nendian). value
should be a valid unsigned 16-bit integer. Behavior is\nundefined when value
is anything other than an unsigned 16-bit integer.
const 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\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": "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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeUInt32BE()
writes big endian, writeUInt32LE()
writes little\nendian). value
should be a valid unsigned 32-bit integer. Behavior is\nundefined when value
is anything other than an unsigned 32-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer fe ed fa ce>\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer ce fa ed fe>\n
"
},
{
"textRaw": "buf.writeUInt32LE(value, offset)",
"type": "method",
"name": "writeUInt32LE",
"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`.",
"name": "offset",
"type": "integer",
"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
with specified endian\nformat (writeUInt32BE()
writes big endian, writeUInt32LE()
writes little\nendian). value
should be a valid unsigned 32-bit integer. Behavior is\nundefined when value
is anything other than an unsigned 32-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer fe ed fa ce>\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": "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
.\nSupports up to 48 bits of accuracy. Behavior is undefined when value
is\nanything other than an unsigned integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n\nbuf.writeUIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\n
"
},
{
"textRaw": "buf.writeUIntLE(value, offset, byteLength)",
"type": "method",
"name": "writeUIntLE",
"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 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
.\nSupports up to 48 bits of accuracy. Behavior is undefined when value
is\nanything other than an unsigned integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\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": "Allocates a new Buffer
using an array
of octets.
// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'\nconst buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);\n
"
},
{
"params": [
{
"textRaw": "`arrayBuffer` {ArrayBuffer|SharedArrayBuffer} An [`ArrayBuffer`], [`SharedArrayBuffer`] or the `.buffer` property of a [`TypedArray`].",
"name": "arrayBuffer",
"type": "ArrayBuffer|SharedArrayBuffer",
"desc": "An [`ArrayBuffer`], [`SharedArrayBuffer`] or the `.buffer` property of a [`TypedArray`]."
},
{
"textRaw": "`byteOffset` {integer} Index of first byte to expose. **Default:** `0`.",
"name": "byteOffset",
"type": "integer",
"default": "`0`",
"desc": "Index of first byte to expose.",
"optional": true
},
{
"textRaw": "`length` {integer} Number of bytes to expose. **Default:** `arrayBuffer.length - byteOffset`.",
"name": "length",
"type": "integer",
"default": "`arrayBuffer.length - byteOffset`",
"desc": "Number of bytes to expose.",
"optional": true
}
],
"desc": "This creates a view of the ArrayBuffer
or SharedArrayBuffer
without\ncopying the underlying memory. For example, when passed a reference to the\n.buffer
property of a TypedArray
instance, the newly created Buffer
will\nshare the same allocated memory as the TypedArray
.
The optional byteOffset
and length
arguments specify a memory range within\nthe arrayBuffer
that will be shared by the Buffer
.
const arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Shares memory with `arr`\nconst buf = new Buffer(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
"
},
{
"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.
const buf1 = new Buffer('buffer');\nconst buf2 = new Buffer(buf1);\n\nbuf1[0] = 0x61;\n\nconsole.log(buf1.toString());\n// Prints: auffer\nconsole.log(buf2.toString());\n// Prints: buffer\n
"
},
{
"params": [
{
"textRaw": "`size` {integer} The desired length of the new `Buffer`.",
"name": "size",
"type": "integer",
"desc": "The desired length of the new `Buffer`."
}
],
"desc": "Allocates a new Buffer
of size
bytes. If size
is larger than\nbuffer.constants.MAX_LENGTH
or smaller than 0, ERR_INVALID_OPT_VALUE
is\nthrown. A zero-length Buffer
is created if size
is 0.
Prior to Node.js 8.0.0, the underlying memory for Buffer
instances\ncreated in this way is not initialized. The contents of a newly created\nBuffer
are unknown and may contain sensitive data. Use\nBuffer.alloc(size)
instead to initialize a Buffer
\nwith zeroes.
const buf = new Buffer(10);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>\n
"
},
{
"params": [
{
"textRaw": "`string` {string} String to encode.",
"name": "string",
"type": "string",
"desc": "String to encode."
},
{
"textRaw": "`encoding` {string} The encoding of `string`. **Default:** `'utf8'`.",
"name": "encoding",
"type": "string",
"default": "`'utf8'`",
"desc": "The encoding of `string`.",
"optional": true
}
],
"desc": "Creates a new Buffer
containing string
. The encoding
parameter identifies\nthe character encoding of string
.
const buf1 = new Buffer('this is a tést');\nconst buf2 = new Buffer('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('ascii'));\n// Prints: this is a tC)st\n
"
}
]
},
{
"textRaw": "Class: SlowBuffer",
"type": "class",
"name": "SlowBuffer",
"meta": {
"deprecated": [
"v6.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`Buffer.allocUnsafeSlow()`] instead.",
"desc": "Returns an un-pooled Buffer
.
In order to avoid the garbage collection overhead of creating many individually\nallocated Buffer
instances, by default allocations under 4KB are sliced from a\nsingle larger allocated object.
In the case where a developer may need to retain a small chunk of memory from a\npool for an indeterminate amount of time, it may be appropriate to create an\nun-pooled Buffer
instance using SlowBuffer
then copy out the relevant bits.
// Need to keep around a few small chunks of memory\nconst store = [];\n\nsocket.on('readable', () => {\n const data = socket.read();\n\n // Allocate for retained data\n const sb = SlowBuffer(10);\n\n // Copy the data into the new allocation\n data.copy(sb, 0, 0, 10);\n\n store.push(sb);\n});\n
\nUse of SlowBuffer
should be used only as a last resort after a developer\nhas observed undue memory retention in their applications.
Allocates a new Buffer
of size
bytes. If size
is larger than\nbuffer.constants.MAX_LENGTH
or smaller than 0, ERR_INVALID_OPT_VALUE
is\nthrown. A zero-length Buffer
is created if size
is 0.
The underlying memory for SlowBuffer
instances is not initialized. The\ncontents of a newly created SlowBuffer
are unknown and may contain sensitive\ndata. Use buf.fill(0)
to initialize a SlowBuffer
with\nzeroes.
const { SlowBuffer } = require('buffer');\n\nconst buf = new SlowBuffer(5);\n\nconsole.log(buf);\n// Prints: (contents may vary): <Buffer 78 e0 82 02 01>\n\nbuf.fill(0);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00>\n
"
}
]
}
],
"properties": [
{
"textRaw": "`INSPECT_MAX_BYTES` {integer} **Default:** `50`",
"type": "integer",
"name": "INSPECT_MAX_BYTES",
"meta": {
"added": [
"v0.5.4"
],
"changes": []
},
"default": "`50`",
"desc": "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.
Note that this is a property on the buffer
module returned by\nrequire('buffer')
, not on the Buffer
global or a Buffer
instance.
An alias for buffer.constants.MAX_LENGTH
.
Note that this is a property on the buffer
module returned by\nrequire('buffer')
, not on the Buffer
global or a Buffer
instance.
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:
\nconst buffer = require('buffer');\n\nconst newBuf = buffer.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
.
Note that this is a property on the buffer
module returned by\nrequire('buffer')
, not on the Buffer
global or a Buffer
instance.
\n\nStability: 2 - Stable
\n
The child_process
module provides the ability to spawn child processes 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('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.log(`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 child. These pipes have\nlimited (and platform-specific) capacity. If the child process writes to\nstdout in excess of that limit without the output being captured, the child\nprocess will block 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 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 child_process
module provides a handful of synchronous\nand asynchronous alternatives to child_process.spawn()
and\nchild_process.spawnSync()
. Note that each of these alternatives are\nimplemented on top of child_process.spawn()
or child_process.spawnSync()
.
child_process.exec()
: spawns a shell and runs a command within that shell,\npassing the stdout
and stderr
to a callback function when complete.child_process.execFile()
: similar to child_process.exec()
except that\nit spawns the command directly without first spawning a shell by default.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 additionally\nallow for an optional callback
function to be specified that is invoked\nwhen 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 operating\nsystems (Unix, Linux, macOS) child_process.execFile()
can be more efficient\nbecause it does not spawn a shell by default. On Windows, however, .bat
and .cmd
\nfiles are not executable on their own without a terminal, and therefore cannot\nbe launched using child_process.execFile()
. When running on Windows, .bat
\nand .cmd
files can be invoked using child_process.spawn()
with the shell
\noption set, with child_process.exec()
, or by spawning cmd.exe
and passing\nthe .bat
or .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('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.log(data.toString());\n});\n\nbat.on('exit', (code) => {\n console.log(`Child exited with code ${code}`);\n});\n
\n// OR...\nconst { exec } = require('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": "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} Current working directory of the child process. **Default:** `null`.",
"name": "cwd",
"type": "string",
"default": "`null`",
"desc": "Current working directory of the child process."
},
{
"textRaw": "`env` {Object} Environment key-value pairs. **Default:** `null`.",
"name": "env",
"type": "Object",
"default": "`null`",
"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": "`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. See caveat at [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.",
"name": "maxBuffer",
"type": "number",
"default": "`200 * 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": "`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."
}
],
"optional": true
},
{
"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"
}
],
"optional": true
}
]
}
],
"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:
exec('\"/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// 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 child process while error.signal
will be set to the\nsignal that terminated the process. Any exit code other than 0
is considered\nto be an error.
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('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.log(`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. In case of an\nerror (including any error resulting in an exit code other than 0), a rejected\npromise is returned, with the same error
object given in the callback, but\nwith an additional two properties stdout
and stderr
.
const util = require('util');\nconst exec = util.promisify(require('child_process').exec);\n\nasync function lsExample() {\n const { stdout, stderr } = await exec('ls');\n console.log('stdout:', stdout);\n console.log('stderr:', stderr);\n}\nlsExample();\n
"
},
{
"textRaw": "child_process.execFile(file[, args][, options][, callback])",
"type": "method",
"name": "execFile",
"meta": {
"added": [
"v0.1.91"
],
"changes": [
{
"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": "`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.",
"optional": true
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`cwd` {string} Current working directory of the child process.",
"name": "cwd",
"type": "string",
"desc": "Current working directory of the child process."
},
{
"textRaw": "`env` {Object} Environment key-value pairs.",
"name": "env",
"type": "Object",
"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. See caveat at [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.",
"name": "maxBuffer",
"type": "number",
"default": "`200 * 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": "`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][]."
}
],
"optional": true
},
{
"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"
}
],
"optional": true
}
]
}
],
"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 executable file
\nis spawned directly as a new process making it slightly more efficient than\nchild_process.exec()
.
The same options as child_process.exec()
are supported. Since a shell is not\nspawned, behaviors such as I/O redirection and file globbing are not supported.
const { execFile } = require('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. In case of an\nerror (including any error resulting in an exit code other than 0), a rejected\npromise is returned, with the same error
object given in the\ncallback, but with an additional two properties stdout
and stderr
.
const util = require('util');\nconst execFile = util.promisify(require('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.
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 returned\nChildProcess
will have an additional communication channel built-in that\nallows messages to be passed back and forth between the parent and child. See\nsubprocess.send()
for details.
It is important to 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.
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.
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('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.log(`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('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.log(`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.log(`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('child_process');\nconst subprocess = spawn('bad_command');\n\nsubprocess.on('error', (err) => {\n console.log('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 currently 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.
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. Note that\nchild processes may continue running after the parent exits regardless of\nwhether they 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('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('fs');\nconst { spawn } = require('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": "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)'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 created\nfor fds 0 - 2 are also available as subprocess.stdin
,\nsubprocess.stdout
and subprocess.stderr
, respectively.
'ipc'
- Create an IPC channel for passing messages/file descriptors\nbetween parent and child. A ChildProcess
may have at most one IPC stdio\nfile descriptor. Setting this option enables the subprocess.send()
\nmethod. If the child is a Node.js process, the presence of an IPC channel\nwill enable process.send()
and process.disconnect()
methods,\nas well as 'disconnect'
and '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 - 2 for the processes it spawns, setting the fd to\n'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. Note that the stream must\nhave an underlying descriptor (file streams do not until the 'open'
\nevent has occurred).
Positive integer - The integer value is interpreted as a file descriptor\nthat is currently open in the parent process. It is shared with the child\nprocess, similar to how <Stream> objects can be shared.
\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('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.
On UNIX-like operating systems, the child_process.spawn()
method\nperforms memory operations synchronously before decoupling the event loop\nfrom the child. Applications with a large memory footprint may find frequent\nchild_process.spawn()
calls to be a bottleneck. For more information,\nsee V8 issue 7381.
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\nthe Node.js event loop, pausing execution of any additional code until the\nspawned process 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": "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.", "optional": true }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cwd` {string} Current working directory of the child process.", "name": "cwd", "type": "string", "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. 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. 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.", "name": "env", "type": "Object", "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:** `200 * 1024`.", "name": "maxBuffer", "type": "number", "default": "`200 * 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][]." } ], "optional": true } ] } ], "desc": "The child_process.execFileSync()
method is generally identical to\nchild_process.execFile()
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
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\nthrow an Error
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 until\nthe child process has fully closed. When a timeout has been encountered and\nkillSignal
is sent, the method won't return until the process has completely\nexited. Note that if the child process intercepts and handles the SIGTERM
\nsignal and doesn't exit, the parent process will wait until the child\nprocess has exited.
If the process times out or has a non-zero exit code, this method will\nthrow. The 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": "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} The exit code of the child process.", "name": "status", "type": "number", "desc": "The exit code of the child process." }, { "textRaw": "`signal` {string} The signal used to kill the child process.", "name": "signal", "type": "string", "desc": "The signal used to kill the child process." }, { "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.", "optional": true }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cwd` {string} Current working directory of the child process.", "name": "cwd", "type": "string", "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. 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. 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.", "name": "stdio", "type": "string|Array", "desc": "Child's stdio configuration." }, { "textRaw": "`env` {Object} Environment key-value pairs.", "name": "env", "type": "Object", "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:** `200 * 1024`.", "name": "maxBuffer", "type": "number", "default": "`200 * 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": "`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." } ], "optional": true } ] } ], "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. Note that if the process intercepts and handles the\nSIGTERM
signal and doesn't exit, the parent process will wait until the child\nprocess has exited.
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.
Instances of the ChildProcess
class are EventEmitters
that represent\nspawned 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 when the stdio streams of a child process have\nbeen closed. This is distinct from the 'exit'
event, since multiple\nprocesses might share the same stdio streams.
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:
The 'exit'
event may or may not fire after an error has occurred. When\nlistening to both the 'exit'
and 'error'
events, it is important to 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.
Note that when the 'exit'
event is triggered, child process stdio streams\nmight still be open.
Also, note that Node.js establishes signal handlers for SIGINT
and\nSIGTERM
and Node.js processes will not terminate immediately due to receipt\nof those signals. Rather, Node.js will perform a sequence of cleanup actions\nand then will re-raise the handled signal.
See waitpid(2)
.
The 'message'
event is triggered when a child process uses process.send()
\nto send messages.
The message goes through serialization and parsing. The resulting\nmessage might not be the same as what is originally sent.
" } ], "properties": [ { "textRaw": "`channel` {Object} A pipe representing the IPC channel to the child process.", "type": "Object", "name": "channel", "meta": { "added": [ "v7.1.0" ], "changes": [] }, "desc": "The subprocess.channel
property is a reference to the child's IPC channel. If\nno IPC channel currently exists, this property is undefined
.
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.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.
\nconst { spawn } = require('child_process');\nconst grep = spawn('grep', ['ssh']);\n\nconsole.log(`Spawned child pid: ${grep.pid}`);\ngrep.stdin.end();\n
"
},
{
"textRaw": "`stderr` {stream.Readable}",
"type": "stream.Readable",
"name": "stderr",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"desc": "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.
A Writable Stream
that represents the child process's stdin
.
Note that if a child process waits to read all of its input, the child will not\ncontinue until 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.
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'
. Note that subprocess.stdio[0]
, subprocess.stdio[1]
,\nand subprocess.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('assert');\nconst fs = require('fs');\nconst child_process = require('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
"
},
{
"textRaw": "`stdout` {stream.Readable}",
"type": "stream.Readable",
"name": "stdout",
"meta": {
"added": [
"v0.1.90"
],
"changes": []
},
"desc": "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.
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()
.
Note that 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.
const { spawn } = require('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 cannot be\ndelivered. Sending a signal to a child process that has already exited is not\nan error but may have unforeseen consequences. Specifically, if the process\nidentifier (PID) has been reassigned to another process, the signal will be\ndelivered to that process instead which can have unexpected results.
Note that while the function is called kill
, the signal delivered to the\nchild process may not actually terminate the process.
See kill(2)
for reference.
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('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 process in the shell\n}, 2000);\n
"
},
{
"textRaw": "subprocess.ref()",
"type": "method",
"name": "ref",
"meta": {
"added": [
"v0.7.10"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "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('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",
"optional": true
},
{
"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."
}
],
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"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('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 that\nallows 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 happen,\nfor 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('child_process').fork('subprocess.js');\n\n// Open up the server object and send the handle.\nconst server = require('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 net
module, dgram
\nmodule servers use exactly the same workflow with the exceptions of listening on\na 'message'
event instead of 'connection'
and using server.bind()
instead of\nserver.listen()
. This is, however, currently only supported 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('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('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
\nOnce a socket has been passed to a child, the parent is no longer capable of\ntracking when the socket is destroyed. To indicate this, the .connections
\nproperty becomes null
. It is recommended not to use .maxConnections
when\nthis occurs.
It is also recommended that any 'message'
handlers in the child process\nverify that socket
exists, as the connection may have been closed during the\ntime it takes to send the connection 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('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"
},
{
"textRaw": "Cluster",
"name": "cluster",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "A single instance of Node.js runs in a single thread. To take advantage of\nmulti-core systems, the user will sometimes want to launch a cluster of Node.js\nprocesses to handle the load.
\nThe cluster module allows easy creation of child processes that all share\nserver ports.
\nconst cluster = require('cluster');\nconst http = require('http');\nconst numCPUs = require('os').cpus().length;\n\nif (cluster.isMaster) {\n console.log(`Master ${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\nMaster 3596 is running\nWorker 4324 started\nWorker 4520 started\nWorker 6056 started\nWorker 5644 started\n
\nPlease note that on Windows, it is not yet possible to set up a named pipe\nserver 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 master 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 master 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 master\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 master,\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 master\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 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 master 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.
const worker = cluster.fork();\nworker.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
"
},
{
"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
\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 master\nprocess of the number of HTTP requests received by the workers:
\nconst cluster = require('cluster');\nconst http = require('http');\n\nif (cluster.isMaster) {\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('os').cpus().length;\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 master 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 master, an internal message is sent to the worker causing it to call\n.disconnect()
on itself.
Causes .exitedAfterDisconnect
to be set.
Note that 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.
\nNote that in 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.isMaster) {\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('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 master via its\nIPC channel, false
otherwise. A worker is connected to its master 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
.
This function will kill the worker. In the master, it does this by disconnecting\nthe worker.process
, and once disconnected, killing with signal
. In the\nworker, it does it by disconnecting the channel, and then exiting with code 0
.
Because kill()
attempts to gracefully disconnect the worker process, it is\nsusceptible to waiting indefinitely for the disconnect to complete. For example,\nif the worker enters an infinite loop, a graceful disconnect will never occur.\nIf the graceful disconnect behavior is not needed, use worker.process.kill()
.
Causes .exitedAfterDisconnect
to be set.
This method is aliased as worker.destroy()
for backwards compatibility.
Note that in a worker, process.kill()
exists, but it is not this function,\nit is kill
.
Send a message to a worker or master, optionally with a handle.
\nIn the master this sends a message to a specific worker. It is identical to\nChildProcess.send()
.
In a worker this sends a message to the master. It is identical to\nprocess.send()
.
This example will echo back all messages from the master:
\nif (cluster.isMaster) {\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": "Set by calling .kill()
or .disconnect()
. Until then, it is undefined
.
The boolean worker.exitedAfterDisconnect
allows distinguishing between\nvoluntary and accidental exit, the master 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` {number}",
"type": "number",
"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.
\nNote that workers 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\nmaster.
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'
(UDP v4 or v6)Emitted when the cluster master receives a message from any worker.
\nSee child_process
event: 'message'
.
Before Node.js v6.0, this event emitted only the message and the handle,\nbut not the worker object, contrary to what the documentation stated.
\nIf support for older versions is required but a worker object is not\nrequired, it is possible to work around the discrepancy by checking the\nnumber of arguments:
\ncluster.on('message', (worker, message, handle) => {\n if (arguments.length === 2) {\n handle = message;\n message = worker;\n worker = undefined;\n }\n // ...\n});\n
"
},
{
"textRaw": "Event: 'online'",
"type": "event",
"name": "online",
"meta": {
"added": [
"v0.7.0"
],
"changes": []
},
"params": [
{
"textRaw": "`worker` {cluster.Worker}",
"name": "worker",
"type": "cluster.Worker"
}
],
"desc": "After forking a new worker, the worker should respond with an online message.\nWhen the master receives an online message it will emit this event.\nThe difference between 'fork'
and 'online'
is that fork is emitted when the\nmaster 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 .setupMaster()
is called.
The settings
object is the cluster.settings
object at the time\n.setupMaster()
was called and is advisory only, since multiple calls to\n.setupMaster()
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\nmaster 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 master 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.", "optional": true } ] } ], "desc": "Spawn a new worker process.
\nThis can only be called from the master process.
" }, { "textRaw": "cluster.setupMaster([settings])", "type": "method", "name": "setupMaster", "meta": { "added": [ "v0.7.1" ], "changes": [ { "version": "v6.4.0", "pr-url": "https://github.com/nodejs/node/pull/7838", "description": "The `stdio` option is supported now." } ] }, "signatures": [ { "params": [ { "textRaw": "`settings` {Object} See [`cluster.settings`][].", "name": "settings", "type": "Object", "desc": "See [`cluster.settings`][].", "optional": true } ] } ], "desc": "setupMaster
is used to change the default 'fork' behavior. Once called,\nthe settings will be present in cluster.settings
.
Note that:
\n.fork()
and have no\neffect on workers that are already running..setupMaster()
is\nthe env
passed to .fork()
.cluster.setupMaster()
is called.const cluster = require('cluster');\ncluster.setupMaster({\n exec: 'worker.js',\n args: ['--use', 'https'],\n silent: true\n});\ncluster.fork(); // https worker\ncluster.setupMaster({\n exec: 'worker.js',\n args: ['--use', 'http']\n});\ncluster.fork(); // http worker\n
\nThis can only be called from the master process.
" } ], "properties": [ { "textRaw": "`isMaster` {boolean}", "type": "boolean", "name": "isMaster", "meta": { "added": [ "v0.8.1" ], "changes": [] }, "desc": "True if the process is a master. This is determined\nby the process.env.NODE_UNIQUE_ID
. If process.env.NODE_UNIQUE_ID
is\nundefined, then isMaster
is true
.
True if the process is not a master (it is the negation of cluster.isMaster
).
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 cluster.setupMaster()
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 .setupMaster()
(or .fork()
) this settings object will contain\nthe 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 master process.
\nconst cluster = require('cluster');\n\nif (cluster.isMaster) {\n console.log('I am master');\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. Makes it\neasy to loop through all the workers. It is only available in the master\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 last 'disconnect'
or 'exit'
event is emitted.
// Go through all workers\nfunction eachWorker(callback) {\n for (const id in cluster.workers) {\n callback(cluster.workers[id]);\n }\n}\neachWorker((worker) => {\n worker.send('big announcement to all workers');\n});\n
\nUsing the worker's unique id is the easiest way to locate the worker.
\nsocket.on('data', (id) => {\n const worker = cluster.workers[id];\n});\n
"
}
],
"type": "module",
"displayName": "Cluster"
},
{
"textRaw": "Console",
"name": "console",
"introduced_in": "v0.10.13",
"stability": 2,
"stabilityText": "Stable",
"desc": "The console
module provides a simple debugging console that is similar to the\nJavaScript 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('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: Whoops, something bad happened], to stderr\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('console').Console
\nor console.Console
(or their destructured counterparts):
const { Console } = require('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.",
"optional": true
}
]
}
],
"desc": "A simple assertion test that verifies whether value
is truthy. If it is not,\nAssertion failed
is logged. If provided, the error message
is formatted\nusing util.format()
by passing along all message arguments. The output is\nused as the error message.
console.assert(true, 'does nothing');\n// OK\nconsole.assert(false, 'Whoops %s work', 'didn\\'t');\n// Assertion failed: Whoops didn't work\n
\nCalling console.assert()
with a falsy assertion will only cause the message
\nto be printed to the console without interrupting execution of subsequent code.
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.",
"optional": true
}
]
}
],
"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": "v9.3.0",
"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",
"optional": true
}
]
}
],
"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.\nPlease note that this 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 two spaces.
\nIf 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 two spaces.
" }, { "textRaw": "console.info([data][, ...args])", "type": "method", "name": "info", "meta": { "added": [ "v0.1.100" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any", "optional": true }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any", "optional": true } ] } ], "desc": "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'`",
"optional": true
}
]
}
],
"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\nmilliseconds to stdout
. Timer durations are accurate to the sub-millisecond.
Stops a timer that was previously started by calling console.time()
and\nprints the result to stdout
:
console.time('100-elements');\nfor (let i = 0; i < 100; i++) {}\nconsole.timeEnd('100-elements');\n// prints 100-elements: 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'`",
"optional": true
},
{
"textRaw": "`...data` {any}",
"name": "...data",
"type": "any",
"optional": true
}
]
}
],
"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",
"optional": true
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any",
"optional": true
}
]
}
],
"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",
"optional": true
},
{
"textRaw": "`...args` {any}",
"name": "...args",
"type": "any",
"optional": true
}
]
}
],
"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 `'auto'` will make color support depend on the value of the `isTTY` property and the value returned by `getColorDepth()` on the respective stream. **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 `'auto'` will make color support depend on the value of the `isTTY` property and the value returned by `getColorDepth()` on the respective stream."
}
]
}
],
"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.markTimeline()
method is the deprecated form of\nconsole.timeStamp()
.
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",
"optional": true
}
]
}
],
"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", "optional": true } ] } ], "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.
This method does not display anything unless used in the inspector. The\nconsole.timeline()
method is the deprecated form of console.time()
.
This method does not display anything unless used in the inspector. The\nconsole.timelineEnd()
method is the deprecated form of\nconsole.timeEnd()
.
The crypto
module provides cryptographic functionality that includes a set of\nwrappers for OpenSSL's hash, HMAC, cipher, decipher, sign, and verify functions.
Use require('crypto')
to access this module.
const crypto = require('crypto');\n\nconst secret = 'abcdefg';\nconst hash = crypto.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\ncrypto
module. In such cases, calling require('crypto')
will result in an\nerror being thrown.
let crypto;\ntry {\n crypto = require('crypto');\n} catch (err) {\n console.log('crypto support is disabled!');\n}\n
",
"type": "module",
"displayName": "Determining if crypto support is unavailable"
},
{
"textRaw": "`crypto` module methods and properties",
"name": "`crypto`_module_methods_and_properties",
"properties": [
{
"textRaw": "`constants` Returns: {Object} An object containing commonly used constants for crypto and security related operations. The specific constants currently defined are described in [Crypto Constants][].",
"type": "Object",
"name": "return",
"meta": {
"added": [
"v6.3.0"
],
"changes": []
},
"desc": "An object containing commonly used constants for crypto and security related operations. The specific constants currently defined are described in [Crypto Constants][]."
},
{
"textRaw": "crypto.DEFAULT_ENCODING",
"name": "DEFAULT_ENCODING",
"meta": {
"added": [
"v0.9.3"
],
"deprecated": [
"v10.0.0"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated",
"desc": "The default encoding to use for functions that can take either strings\nor buffers. The default value is 'buffer'
, which makes methods\ndefault to Buffer
objects.
The crypto.DEFAULT_ENCODING
mechanism is provided for backwards compatibility\nwith legacy programs that expect 'latin1'
to be the default encoding.
New applications should expect the default to be 'buffer'
.
This property is deprecated.
" }, { "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.
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 is used (e.g. 'aes-128-ccm'
). 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.
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms
\n(openssl list-cipher-algorithms
for older versions of OpenSSL) 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
.
The 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 is used (e.g. 'aes-128-ccm'
). 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.
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms
\n(openssl list-cipher-algorithms
for older versions of OpenSSL) 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. If the cipher does not need\nan initialization vector, iv
may be null
.
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;\nit is important to remember that an attacker must not be able to predict ahead\nof time what a given IV will be.
" }, { "textRaw": "crypto.createDecipher(algorithm, password[, options])", "type": "method", "name": "createDecipher", "meta": { "added": [ "v0.1.94" ], "deprecated": [ "v10.0.0" ], "changes": [ { "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 | Buffer | TypedArray | DataView}", "name": "password", "type": "string | Buffer | TypedArray | DataView" }, { "textRaw": "`options` {Object} [`stream.transform` options][]", "name": "options", "type": "Object", "desc": "[`stream.transform` options][]", "optional": true } ] } ], "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 is used (e.g. 'aes-128-ccm'
). In that case, the\nauthTagLength
option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode.
The 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 is used (e.g. 'aes-128-ccm'
). 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.
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms
\n(openssl list-cipher-algorithms
for older versions of OpenSSL) 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. If the cipher does not need\nan initialization vector, iv
may be null
.
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;\nit is important to remember that an attacker must not be able to predict ahead\nof time what a given IV 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 | Buffer | TypedArray | DataView}", "name": "prime", "type": "string | Buffer | TypedArray | DataView" }, { "textRaw": "`primeEncoding` {string} The [encoding][] of the `prime` string.", "name": "primeEncoding", "type": "string", "desc": "The [encoding][] of the `prime` string.", "optional": true }, { "textRaw": "`generator` {number | string | Buffer | TypedArray | DataView} **Default:** `2`", "name": "generator", "type": "number | string | Buffer | TypedArray | DataView", "default": "`2`", "optional": true }, { "textRaw": "`generatorEncoding` {string} The [encoding][] of the `generator` string.", "name": "generatorEncoding", "type": "string", "desc": "The [encoding][] of the `generator` string.", "optional": true } ] } ], "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.
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.
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
\n(openssl list-message-digest-algorithms
for older versions of OpenSSL) will\ndisplay the available digest algorithms.
Example: generating the sha256 sum of a file
\nconst filename = process.argv[2];\nconst crypto = require('crypto');\nconst fs = require('fs');\n\nconst hash = crypto.createHash('sha256');\n\nconst input = fs.createReadStream(filename);\ninput.on('readable', () => {\n const data = input.read();\n if (data)\n hash.update(data);\n else {\n console.log(`${hash.digest('hex')} ${filename}`);\n }\n});\n
"
},
{
"textRaw": "crypto.createHmac(algorithm, key[, options])",
"type": "method",
"name": "createHmac",
"meta": {
"added": [
"v0.1.94"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Hmac}",
"name": "return",
"type": "Hmac"
},
"params": [
{
"textRaw": "`algorithm` {string}",
"name": "algorithm",
"type": "string"
},
{
"textRaw": "`key` {string | Buffer | TypedArray | DataView}",
"name": "key",
"type": "string | Buffer | TypedArray | DataView"
},
{
"textRaw": "`options` {Object} [`stream.transform` options][]",
"name": "options",
"type": "Object",
"desc": "[`stream.transform` options][]",
"optional": true
}
]
}
],
"desc": "Creates and returns an Hmac
object that uses the given algorithm
and key
.\nOptional options
argument controls stream behavior.
The algorithm
is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256'
, 'sha512'
, etc.\nOn recent releases of OpenSSL, openssl list -digest-algorithms
\n(openssl list-message-digest-algorithms
for older versions of OpenSSL) will\ndisplay the available digest algorithms.
The key
is the HMAC key used to generate the cryptographic HMAC hash.
Example: generating the sha256 HMAC of a file
\nconst filename = process.argv[2];\nconst crypto = require('crypto');\nconst fs = require('fs');\n\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nconst input = fs.createReadStream(filename);\ninput.on('readable', () => {\n const data = input.read();\n if (data)\n hmac.update(data);\n else {\n console.log(`${hmac.digest('hex')} ${filename}`);\n }\n});\n
"
},
{
"textRaw": "crypto.createSign(algorithm[, options])",
"type": "method",
"name": "createSign",
"meta": {
"added": [
"v0.1.92"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Sign}",
"name": "return",
"type": "Sign"
},
"params": [
{
"textRaw": "`algorithm` {string}",
"name": "algorithm",
"type": "string"
},
{
"textRaw": "`options` {Object} [`stream.Writable` options][]",
"name": "options",
"type": "Object",
"desc": "[`stream.Writable` options][]",
"optional": true
}
]
}
],
"desc": "Creates and returns a Sign
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.
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.
Generates a new asymmetric key pair of the given type
. Only RSA, DSA and EC\nare currently supported.
It is recommended to encode public keys as 'spki'
and private keys as\n'pkcs8'
with encryption:
const { generateKeyPair } = require('crypto');\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. When PEM\nencoding was selected, the result will be a string, otherwise it will be a\nbuffer containing the data encoded as DER. Note that Node.js itself does not\naccept DER, it is supported for interoperability with other libraries such as\nWebCrypto only.
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
. Only RSA, DSA and EC\nare currently supported.
It is recommended to encode public keys as 'spki'
and private keys as\n'pkcs8'
with encryption:
const { generateKeyPairSync } = require('crypto');\nconst { publicKey, privateKey } = 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.
const ciphers = crypto.getCiphers();\nconsole.log(ciphers); // ['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 curves = crypto.getCurves();\nconsole.log(curves); // ['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: {DiffieHellman}",
"name": "return",
"type": "DiffieHellman"
},
"params": [
{
"textRaw": "`groupName` {string}",
"name": "groupName",
"type": "string"
}
]
}
],
"desc": "Creates a predefined DiffieHellman
key exchange object. The\nsupported groups are: 'modp1'
, 'modp2'
, 'modp5'
(defined in\nRFC 2412, but see Caveats) and 'modp14'
, 'modp15'
,\n'modp16'
, 'modp17'
, 'modp18'
(defined in RFC 3526). The\nreturned 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 crypto = require('crypto');\nconst alice = crypto.getDiffieHellman('modp14');\nconst bob = crypto.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: {boolean} `true` if and only if a FIPS compliant crypto provider is currently in use.",
"name": "return",
"type": "boolean",
"desc": "`true` if and only if a FIPS compliant crypto provider is currently in use."
},
"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'`.",
"name": "return",
"type": "string[]",
"desc": "An array of the names of the supported hash algorithms, such as `'RSA-SHA256'`."
},
"params": []
}
],
"desc": "const hashes = crypto.getHashes();\nconsole.log(hashes); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]\n
"
},
{
"textRaw": "crypto.pbkdf2(password, salt, iterations, keylen, digest, callback)",
"type": "method",
"name": "pbkdf2",
"meta": {
"added": [
"v0.5.5"
],
"changes": [
{
"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|Buffer|TypedArray|DataView}",
"name": "password",
"type": "string|Buffer|TypedArray|DataView"
},
{
"textRaw": "`salt` {string|Buffer|TypedArray|DataView}",
"name": "salt",
"type": "string|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.
If digest
is null
, 'sha1'
will be used. This behavior is deprecated,\nplease specify a digest
explicitely.
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.
const crypto = require('crypto');\ncrypto.pbkdf2('secret', 'salt', 100000, 64, 'sha512', (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\n
\nThe crypto.DEFAULT_ENCODING
property can be used to change the way the\nderivedKey
is passed to the callback. This property, however, has been\ndeprecated and use should be avoided.
const crypto = require('crypto');\ncrypto.DEFAULT_ENCODING = 'hex';\ncrypto.pbkdf2('secret', 'salt', 100000, 512, 'sha512', (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey); // '3745e48...aa39b34'\n});\n
\nAn array of supported digest functions can be retrieved using\ncrypto.getHashes()
.
Note that 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
.
If digest
is null
, 'sha1'
will be used. This behavior is deprecated,\nplease specify a digest
explicitely.
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.
const crypto = require('crypto');\nconst key = crypto.pbkdf2Sync('secret', 'salt', 100000, 64, 'sha512');\nconsole.log(key.toString('hex')); // '3745e48...08d59ae'\n
\nThe crypto.DEFAULT_ENCODING
property may be used to change the way the\nderivedKey
is returned. This property, however, is deprecated and use\nshould be avoided.
const crypto = require('crypto');\ncrypto.DEFAULT_ENCODING = 'hex';\nconst key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');\nconsole.log(key); // '3745e48...aa39b34'\n
\nAn array of supported digest functions can be retrieved using\ncrypto.getHashes()
.
Decrypts buffer
with privateKey
. buffer
was previously encrypted using\nthe corresponding public key, for example using crypto.publicEncrypt()
.
privateKey
can be an object or a string. If privateKey
is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_OAEP_PADDING
.
Encrypts buffer
with privateKey
. The returned data can be decrypted using\nthe corresponding public key, for example using crypto.publicDecrypt()
.
privateKey
can be an object or a string. If privateKey
is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_PADDING
.
Decrypts buffer
with key
.buffer
was previously encrypted using\nthe corresponding private key, for example using crypto.privateEncrypt()
.
key
can be an object or a string. If key
is a string, it is treated as\nthe key with no passphrase and will use RSA_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": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer} A new `Buffer` with the encrypted content.", "name": "return", "type": "Buffer", "desc": "A new `Buffer` with the encrypted content." }, "params": [ { "textRaw": "`key` {Object | string}", "name": "key", "type": "Object | string", "options": [ { "textRaw": "`key` {string} A PEM encoded public or private key.", "name": "key", "type": "string", "desc": "A PEM encoded public or private key." }, { "textRaw": "`passphrase` {string} An optional passphrase for the private key.", "name": "passphrase", "type": "string", "desc": "An optional passphrase for the private key." }, { "textRaw": "`padding` {crypto.constants} An optional padding value defined in `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING`, `crypto.constants.RSA_PKCS1_PADDING`, or `crypto.constants.RSA_PKCS1_OAEP_PADDING`.", "name": "padding", "type": "crypto.constants", "desc": "An optional padding value defined in `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING`, `crypto.constants.RSA_PKCS1_PADDING`, or `crypto.constants.RSA_PKCS1_OAEP_PADDING`." } ] }, { "textRaw": "`buffer` {Buffer | TypedArray | DataView}", "name": "buffer", "type": "Buffer | TypedArray | DataView" } ] } ], "desc": "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()
.
key
can be an object or a string. If key
is a string, it is treated as\nthe key with no passphrase and will use RSA_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": "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}", "name": "size", "type": "number" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`buf` {Buffer}", "name": "buf", "type": "Buffer" } ], "optional": true } ] } ], "desc": "Generates cryptographically strong pseudo-random 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 crypto = require('crypto');\ncrypto.randomBytes(256, (err, buf) => {\n if (err) throw err;\n console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);\n});\n
\nIf the callback
function is not provided, the random bytes are generated\nsynchronously and returned as a Buffer
. An error will be thrown if\nthere is a problem generating the bytes.
// Synchronous\nconst buf = crypto.randomBytes(256);\nconsole.log(\n `${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.
Note that 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()
.
const buf = Buffer.alloc(10);\nconsole.log(crypto.randomFillSync(buf).toString('hex'));\n\ncrypto.randomFillSync(buf, 5);\nconsole.log(buf.toString('hex'));\n\n// The above is equivalent to the following:\ncrypto.randomFillSync(buf, 5, 5);\nconsole.log(buf.toString('hex'));\n
\nAny TypedArray
or DataView
instance may be passed as buffer
.
const a = new Uint32Array(10);\nconsole.log(Buffer.from(crypto.randomFillSync(a).buffer,\n a.byteOffset, a.byteLength).toString('hex'));\n\nconst b = new Float64Array(10);\nconsole.log(Buffer.from(crypto.randomFillSync(b).buffer,\n b.byteOffset, b.byteLength).toString('hex'));\n\nconst c = new DataView(new ArrayBuffer(10));\nconsole.log(Buffer.from(crypto.randomFillSync(c).buffer,\n c.byteOffset, c.byteLength).toString('hex'));\n
"
},
{
"textRaw": "crypto.randomFill(buffer[, offset][, size], callback)",
"type": "method",
"name": "randomFill",
"meta": {
"added": [
"v7.10.0",
"v6.13.0"
],
"changes": [
{
"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` {Buffer|TypedArray|DataView} Must be supplied.",
"name": "buffer",
"type": "Buffer|TypedArray|DataView",
"desc": "Must be supplied."
},
{
"textRaw": "`offset` {number} **Default:** `0`",
"name": "offset",
"type": "number",
"default": "`0`",
"optional": true
},
{
"textRaw": "`size` {number} **Default:** `buffer.length - offset`",
"name": "size",
"type": "number",
"default": "`buffer.length - offset`",
"optional": true
},
{
"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.
const buf = Buffer.alloc(10);\ncrypto.randomFill(buf, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\ncrypto.randomFill(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:\ncrypto.randomFill(buf, 5, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n
\nAny TypedArray
or DataView
instance may be passed as buffer
.
const a = new Uint32Array(10);\ncrypto.randomFill(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 Float64Array(10);\ncrypto.randomFill(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 DataView(new ArrayBuffer(10));\ncrypto.randomFill(c, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n
\nNote that 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.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.
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.
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 crypto = require('crypto');\n// Using the factory defaults.\ncrypto.scrypt('secret', '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.\ncrypto.scrypt('secret', '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": "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`."
}
],
"optional": true
}
]
}
],
"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.
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 crypto = require('crypto');\n// Using the factory defaults.\nconst key1 = crypto.scryptSync('secret', 'salt', 64);\nconsole.log(key1.toString('hex')); // '3745e48...08d59ae'\n// Using a custom N parameter. Must be a power of two.\nconst key2 = crypto.scryptSync('secret', 'salt', 64, { N: 1024 });\nconsole.log(key2.toString('hex')); // '3745e48...aa39b34'\n
"
},
{
"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`",
"optional": true
}
]
}
],
"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
The flags below are deprecated in OpenSSL-1.1.0.
\ncrypto.constants.ENGINE_METHOD_ECDH
crypto.constants.ENGINE_METHOD_ECDSA
crypto.constants.ENGINE_METHOD_STORE
Enables the FIPS compliant crypto provider in a FIPS-enabled Node.js build.\nThrows an error if FIPS mode is not available.
" }, { "textRaw": "crypto.timingSafeEqual(a, b)", "type": "method", "name": "timingSafeEqual", "meta": { "added": [ "v6.6.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`a` {Buffer | TypedArray | DataView}", "name": "a", "type": "Buffer | TypedArray | DataView" }, { "textRaw": "`b` {Buffer | TypedArray | DataView}", "name": "b", "type": "Buffer | TypedArray | DataView" } ] } ], "desc": "This function is based on a constant-time algorithm.\nReturns true if a
is equal to b
, without leaking 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.
a
and b
must both be Buffer
s, TypedArray
s, or DataView
s, and they\nmust have the same length.
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.
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, the many of the crypto
defined 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.
Usage of ECDH
with non-dynamically generated key pairs has been simplified.\nNow, ecdh.setPrivateKey()
can be called with a preselected private key\nand the associated public point (key) will be computed and stored in the object.\nThis allows code to only store and provide the private part of the EC key pair.\necdh.setPrivateKey()
now also validates that the private key is valid for\nthe selected curve.
The ecdh.setPublicKey()
method is now deprecated as its inclusion in the\nAPI is not useful. Either a previously stored private key should be set, which\nautomatically generates the associated public key, or ecdh.generateKeys()
\nshould be called. The main drawback of using ecdh.setPublicKey()
is that\nit can be used to put the ECDH key pair into an inconsistent state.
The crypto
module still supports some algorithms which are already\ncompromised and are not currently recommended for use. The API also allows\nthe use of ciphers and hashes with a small key size that are considered to be\ntoo weak for safe use.
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.
", "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\nspecifying additional authenticated data or calling 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. This is not necessary if no AAD is used.update()
can only be called\nonce.update()
is sufficient to encrypt/decrypt the message,\napplications must call final()
to compute or verify the\nauthentication tag.const crypto = require('crypto');\n\nconst key = 'keykeykeykeykeykeykeykey';\nconst nonce = crypto.randomBytes(12);\n\nconst aad = Buffer.from('0123456789', 'hex');\n\nconst cipher = crypto.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 = crypto.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 console.error('Authentication failed!');\n}\n\nconsole.log(receivedPlaintext);\n
",
"type": "module",
"displayName": "CCM 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 crypto
, tls
, and https
modules and are generally specific to OpenSSL.
Constant | \nDescription | \n
---|---|
SSL_OP_ALL | \n Applies multiple bug workarounds within OpenSSL. See\n https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html\n for detail. | \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/man1.0.2/ssl/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/man1.0.2/ssl/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_EPHEMERAL_RSA | \n Instructs OpenSSL to always use the tmp_rsa key when performing RSA\n operations. | \n
SSL_OP_LEGACY_SERVER_CONNECT | \n Allows initial connection to servers that do not support RI. | \n
SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER | \n \n |
SSL_OP_MICROSOFT_SESS_ID_BUG | \n \n |
SSL_OP_MSIE_SSLV2_RSA_PADDING | \n Instructs OpenSSL to disable the workaround for a man-in-the-middle\n protocol-version vulnerability in the SSL 2.0 server implementation. | \n
SSL_OP_NETSCAPE_CA_DN_BUG | \n \n |
SSL_OP_NETSCAPE_CHALLENGE_BUG | \n \n |
SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG | \n \n |
SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG | \n \n |
SSL_OP_NO_COMPRESSION | \n Instructs OpenSSL to disable support for SSL/TLS compression. | \n
SSL_OP_NO_QUERY_MTU | \n \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 | \nSSL_OP_PKCS1_CHECK_1 | \n \n \n |
SSL_OP_PKCS1_CHECK_2 | \n \n |
SSL_OP_SINGLE_DH_USE | \n Instructs OpenSSL to always create a new key when using\n temporary/ephemeral DH parameters. | \n
SSL_OP_SINGLE_ECDH_USE | \n Instructs OpenSSL to always create a new key when using\n temporary/ephemeral ECDH parameters. | \nSSL_OP_SSLEAY_080_CLIENT_DH_BUG | \n \n \n |
SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG | \n \n |
SSL_OP_TLS_BLOCK_PADDING_BUG | \n \n |
SSL_OP_TLS_D5_BUG | \n \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 |
ALPN_ENABLED | \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.
Note that <keygen>
is deprecated since HTML 5.2 and new projects\nshould not use this element anymore.
The 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 } = require('crypto');\nconst spkac = getSpkacSomehow();\nconst challenge = Certificate.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": [
"v9.0.0"
],
"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 | Buffer | TypedArray | DataView}",
"name": "spkac",
"type": "string | Buffer | TypedArray | DataView"
},
{
"textRaw": "`encoding` {string} The [encoding][] of the `spkac` string.",
"name": "encoding",
"type": "string",
"desc": "The [encoding][] of the `spkac` string.",
"optional": true
}
]
}
],
"desc": "const { Certificate } = require('crypto');\nconst spkac = getSpkacSomehow();\nconst publicKey = Certificate.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\n
"
},
{
"textRaw": "Certificate.verifySpkac(spkac)",
"type": "method",
"name": "verifySpkac",
"meta": {
"added": [
"v9.0.0"
],
"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` {Buffer | TypedArray | DataView}",
"name": "spkac",
"type": "Buffer | TypedArray | DataView"
}
]
}
],
"desc": "const { Certificate } = require('crypto');\nconst spkac = getSpkacSomehow();\nconsole.log(Certificate.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\n
"
}
],
"modules": [
{
"textRaw": "Legacy API",
"name": "legacy_api",
"desc": "As a still supported legacy interface, it is possible (but not recommended) to\ncreate new instances of the crypto.Certificate
class as illustrated in the\nexamples below.
Instances of the Certificate
class can be created using the new
keyword\nor by calling crypto.Certificate()
as a function:
const crypto = require('crypto');\n\nconst cert1 = new crypto.Certificate();\nconst cert2 = crypto.Certificate();\n
"
}
],
"methods": [
{
"textRaw": "certificate.exportChallenge(spkac)",
"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 | Buffer | TypedArray | DataView}",
"name": "spkac",
"type": "string | Buffer | TypedArray | DataView"
}
]
}
],
"desc": "const cert = require('crypto').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)",
"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 | Buffer | TypedArray | DataView}",
"name": "spkac",
"type": "string | Buffer | TypedArray | DataView"
}
]
}
],
"desc": "const cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconst publicKey = cert.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\n
"
},
{
"textRaw": "certificate.verifySpkac(spkac)",
"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` {Buffer | TypedArray | DataView}",
"name": "spkac",
"type": "Buffer | TypedArray | DataView"
}
]
}
],
"desc": "const cert = require('crypto').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 crypto = require('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 async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// Use `crypto.randomBytes()` to generate a random iv instead of the static iv\n// shown here.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst cipher = crypto.createCipheriv(algorithm, key, iv);\n\nlet encrypted = '';\ncipher.on('readable', () => {\n const data = cipher.read();\n if (data)\n encrypted += data.toString('hex');\n});\ncipher.on('end', () => {\n console.log(encrypted);\n // Prints: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa\n});\n\ncipher.write('some clear text data');\ncipher.end();\n
\nExample: Using Cipher
and piped streams:
const crypto = require('crypto');\nconst fs = require('fs');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// Use `crypto.randomBytes()` to generate a random iv instead of the static iv\n// shown here.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst cipher = crypto.createCipheriv(algorithm, key, iv);\n\nconst input = fs.createReadStream('test.js');\nconst output = fs.createWriteStream('test.enc');\n\ninput.pipe(cipher).pipe(output);\n
\nExample: Using the cipher.update()
and cipher.final()
methods:
const crypto = require('crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// Use `crypto.randomBytes` to generate a random iv instead of the static iv\n// shown here.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst cipher = crypto.createCipheriv(algorithm, key, iv);\n\nlet encrypted = cipher.update('some clear text data', 'utf8', 'hex');\nencrypted += cipher.final('hex');\nconsole.log(encrypted);\n// Prints: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa\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.",
"optional": true
}
]
}
],
"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.
When using an authenticated encryption mode (GCM
, CCM
and OCB
are\ncurrently supported), the cipher.setAAD()
method sets the value used for the\nadditional authenticated data (AAD) input parameter.
The options
argument is optional for GCM
and OCB
. When using CCM
, the\nplaintextLength
option must be specified and its value must match the length\nof the plaintext in bytes. See CCM mode.
The cipher.setAAD()
method must be called before cipher.update()
.
The cipher.getAuthTag()
method should only be called after encryption has\nbeen completed using the cipher.final()
method.
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:
const crypto = require('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 = crypto.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 = crypto.createDecipheriv(algorithm, key, iv);\n\nlet decrypted = '';\ndecipher.on('readable', () => {\n const data = decipher.read();\n if (data)\n decrypted += data.toString('utf8');\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:
const crypto = require('crypto');\nconst fs = require('fs');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.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 = crypto.createDecipheriv(algorithm, key, iv);\n\nconst input = fs.createReadStream('test.enc');\nconst output = fs.createWriteStream('test.js');\n\ninput.pipe(decipher).pipe(output);\n
\nExample: Using the decipher.update()
and decipher.final()
methods:
const crypto = require('crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.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 = crypto.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.",
"optional": true
}
]
}
],
"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
and OCB
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 plaintext in bytes. See CCM mode.
The decipher.setAAD()
method must be called before decipher.update()
.
When using an authenticated encryption mode (GCM
, CCM
and OCB
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\ndecipher.final()
and can only be called once.
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.
const crypto = require('crypto');\nconst assert = require('assert');\n\n// Generate Alice's keys...\nconst alice = crypto.createDiffieHellman(2048);\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = crypto.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 | Buffer | TypedArray | DataView}",
"name": "otherPublicKey",
"type": "string | Buffer | TypedArray | DataView"
},
{
"textRaw": "`inputEncoding` {string} The [encoding][] of an `otherPublicKey` string.",
"name": "inputEncoding",
"type": "string",
"desc": "The [encoding][] of an `otherPublicKey` string.",
"optional": true
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value.",
"optional": true
}
]
}
],
"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, 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.
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
.
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 constants
\nmodule):
DH_CHECK_P_NOT_SAFE_PRIME
DH_CHECK_P_NOT_PRIME
DH_UNABLE_TO_CHECK_GENERATOR
DH_NOT_SUITABLE_GENERATOR
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.
const crypto = require('crypto');\nconst assert = require('assert');\n\n// Generate Alice's keys...\nconst alice = crypto.createECDH('secp521r1');\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = crypto.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": "Class 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 | Buffer | TypedArray | DataView}",
"name": "key",
"type": "string | 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.",
"optional": true
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value.",
"optional": true
},
{
"textRaw": "`format` {string} **Default:** `'uncompressed'`",
"name": "format",
"type": "string",
"default": "`'uncompressed'`",
"optional": true
}
]
}
],
"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 { createECDH, ECDH } = require('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": "v6.0.0",
"pr-url": "https://github.com/nodejs/node/pull/5522",
"description": "The default `inputEncoding` changed from `binary` to `utf8`"
},
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/16849",
"description": "Changed error format to better support invalid public key error"
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`otherPublicKey` {string | Buffer | TypedArray | DataView}",
"name": "otherPublicKey",
"type": "string | Buffer | TypedArray | DataView"
},
{
"textRaw": "`inputEncoding` {string} The [encoding][] of the `otherPublicKey` string.",
"name": "inputEncoding",
"type": "string",
"desc": "The [encoding][] of the `otherPublicKey` string.",
"optional": true
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value.",
"optional": true
}
]
}
],
"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,\nits recommended for developers 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.
Note that 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 crypto = require('crypto');\nconst alice = crypto.createECDH('secp256k1');\nconst bob = crypto.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 crypto.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 crypto = require('crypto');\nconst hash = crypto.createHash('sha256');\n\nhash.on('readable', () => {\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:
const crypto = require('crypto');\nconst fs = require('fs');\nconst hash = crypto.createHash('sha256');\n\nconst input = fs.createReadStream('test.js');\ninput.pipe(hash).pipe(process.stdout);\n
\nExample: Using the hash.update()
and hash.digest()
methods:
const crypto = require('crypto');\nconst hash = crypto.createHash('sha256');\n\nhash.update('some data to hash');\nconsole.log(hash.digest('hex'));\n// Prints:\n// 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n
",
"methods": [
{
"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.",
"optional": true
}
]
}
],
"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 crypto = require('crypto');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nhmac.on('readable', () => {\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:
const crypto = require('crypto');\nconst fs = require('fs');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nconst input = fs.createReadStream('test.js');\ninput.pipe(hmac).pipe(process.stdout);\n
\nExample: Using the hmac.update()
and hmac.digest()
methods:
const crypto = require('crypto');\nconst hmac = crypto.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.",
"optional": true
}
]
}
],
"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: Sign", "type": "class", "name": "Sign", "meta": { "added": [ "v0.1.92" ], "changes": [] }, "desc": "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
objects as streams:
const crypto = require('crypto');\nconst sign = crypto.createSign('SHA256');\n\nsign.write('some data to sign');\nsign.end();\n\nconst privateKey = getPrivateKeySomehow();\nconsole.log(sign.sign(privateKey, 'hex'));\n// Prints: the calculated signature using the specified private key and\n// SHA-256. For RSA keys, the algorithm is RSASSA-PKCS1-v1_5 (see padding\n// parameter below for RSASSA-PSS). For EC keys, the algorithm is ECDSA.\n
\nExample: Using the sign.update()
and sign.sign()
methods:
const crypto = require('crypto');\nconst sign = crypto.createSign('SHA256');\n\nsign.update('some data to sign');\n\nconst privateKey = getPrivateKeySomehow();\nconsole.log(sign.sign(privateKey, 'hex'));\n// Prints: the calculated signature\n
\nIn some cases, a Sign
instance can also be created by passing in a signature\nalgorithm name, such as 'RSA-SHA256'. This will use the corresponding digest\nalgorithm. This does not work for all signature algorithms, such as\n'ecdsa-with-SHA256'. Use digest names instead.
Example: signing using legacy signature algorithm name
\nconst crypto = require('crypto');\nconst sign = crypto.createSign('RSA-SHA256');\n\nsign.update('some data to sign');\n\nconst privateKey = getPrivateKeySomehow();\nconsole.log(sign.sign(privateKey, 'hex'));\n// Prints: the calculated signature\n
",
"methods": [
{
"textRaw": "sign.sign(privateKey[, outputEncoding])",
"type": "method",
"name": "sign",
"meta": {
"added": [
"v0.1.92"
],
"changes": [
{
"version": "v8.0.0",
"pr-url": "https://github.com/nodejs/node/pull/11705",
"description": "Support for RSASSA-PSS and additional options was added."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Buffer | string}",
"name": "return",
"type": "Buffer | string"
},
"params": [
{
"textRaw": "`privateKey` {string | Object}",
"name": "privateKey",
"type": "string | Object",
"options": [
{
"textRaw": "`key` {string}",
"name": "key",
"type": "string"
},
{
"textRaw": "`passphrase` {string}",
"name": "passphrase",
"type": "string"
},
{
"textRaw": "`padding` {integer}",
"name": "padding",
"type": "integer"
},
{
"textRaw": "`saltLength` {integer}",
"name": "saltLength",
"type": "integer"
}
]
},
{
"textRaw": "`outputEncoding` {string} The [encoding][] of the return value.",
"name": "outputEncoding",
"type": "string",
"desc": "The [encoding][] of the return value.",
"optional": true
}
]
}
],
"desc": "Calculates the signature on all the data passed through using either\nsign.update()
or sign.write()
.
The privateKey
argument can be an object or a string. If privateKey
is a\nstring, it is treated as a raw key with no passphrase. If privateKey
is an\nobject, it must contain one or more of the following properties:
key
: <string> - PEM encoded private key (required)
passphrase
: <string> - passphrase for the private key
padding
: <integer> - Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING
(default)crypto.constants.RSA_PKCS1_PSS_PADDING
Note that 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 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.
Example: Using Verify
objects as streams:
const crypto = require('crypto');\nconst verify = crypto.createVerify('SHA256');\n\nverify.write('some data to sign');\nverify.end();\n\nconst publicKey = getPublicKeySomehow();\nconst signature = getSignatureToVerify();\nconsole.log(verify.verify(publicKey, signature));\n// Prints: true or false\n
\nExample: Using the verify.update()
and verify.verify()
methods:
const crypto = require('crypto');\nconst verify = crypto.createVerify('SHA256');\n\nverify.update('some data to sign');\n\nconst publicKey = getPublicKeySomehow();\nconst signature = getSignatureToVerify();\nconsole.log(verify.verify(publicKey, signature));\n// Prints: true or false\n
",
"methods": [
{
"textRaw": "verify.update(data[, inputEncoding])",
"type": "method",
"name": "update",
"meta": {
"added": [
"v0.1.92"
],
"changes": [
{
"version": "v6.0.0",
"pr-url": "https://github.com/nodejs/node/pull/5522",
"description": "The default `inputEncoding` changed from `binary` to `utf8`."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`data` {string | Buffer | TypedArray | DataView}",
"name": "data",
"type": "string | Buffer | TypedArray | DataView"
},
{
"textRaw": "`inputEncoding` {string} The [encoding][] of the `data` string.",
"name": "inputEncoding",
"type": "string",
"desc": "The [encoding][] of the `data` string.",
"optional": true
}
]
}
],
"desc": "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": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11705", "description": "Support for RSASSA-PSS and additional options was added." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean} `true` or `false` depending on the validity of the signature for the data and public key.", "name": "return", "type": "boolean", "desc": "`true` or `false` depending on the validity of the signature for the data and public key." }, "params": [ { "textRaw": "`object` {string | Object}", "name": "object", "type": "string | Object" }, { "textRaw": "`signature` {string | Buffer | TypedArray | DataView}", "name": "signature", "type": "string | Buffer | TypedArray | DataView" }, { "textRaw": "`signatureEncoding` {string} The [encoding][] of the `signature` string.", "name": "signatureEncoding", "type": "string", "desc": "The [encoding][] of the `signature` string.", "optional": true } ] } ], "desc": "Verifies the provided data using the given object
and signature
.\nThe object
argument can be either a string containing a PEM encoded object,\nwhich can be an RSA public key, a DSA public key, or an X.509 certificate,\nor an object with one or more of the following properties:
key
: <string> - PEM encoded public key (required)
padding
: <integer> - Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING
(default)crypto.constants.RSA_PKCS1_PSS_PADDING
Note that 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.
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.
The dns
module contains functions belonging to two different categories:
1) Functions that use the underlying operating system facilities to perform\nname resolution, and that do not necessarily perform any network communication.\nThis category contains only one function: dns.lookup()
. Developers\nlooking to perform name resolution in the same way that other applications on\nthe same operating system behave should use dns.lookup()
.
For example, looking up iana.org
.
const dns = require('dns');\n\ndns.lookup('iana.org', (err, address, family) => {\n console.log('address: %j family: IPv%s', address, family);\n});\n// address: \"192.0.43.8\" family: IPv4\n
\n2) Functions that connect to an actual DNS server to perform name resolution,\nand that always use the network to perform DNS queries. This category\ncontains all functions in the dns
module except dns.lookup()
. These\nfunctions do not use the same set of configuration files used by\ndns.lookup()
(e.g. /etc/hosts
). These functions should be used by\ndevelopers who do not want to use the underlying operating system's facilities\nfor name resolution, and instead want to always perform DNS queries.
Below is an example that resolves 'archive.org'
then reverse resolves the IP\naddresses that are returned.
const dns = require('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
\nThere are subtle consequences in choosing one over the other, please consult\nthe 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.
\nNote that creating 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('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 dns
module are available:
resolver.getServers()
resolver.resolve()
resolver.resolve4()
resolver.resolve6()
resolver.resolveAny()
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\ncallbacks will be called with an error with code ECANCELLED
.
Returns an array of IP address strings, formatted according to rfc5952,\nthat are currently configured for DNS resolution. A string will include a port\nsection if a custom port is used.
\n\n[\n '4.4.4.4',\n '2001:4860:4860::8888',\n '4.4.4.4:1053',\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": "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} The record family. Must be `4` or `6`. IPv4 and IPv6 addresses are both returned by default.",
"name": "family",
"type": "integer",
"desc": "The record family. Must be `4` or `6`. IPv4 and IPv6 addresses are both returned by default."
},
{
"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:** currently `false` (addresses are reordered) but this is expected to change in the not too distant future. 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. New code should use `{ verbatim: true }`",
"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."
}
],
"optional": true
},
{
"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`.",
"name": "family",
"type": "integer",
"desc": "`4` or `6`, denoting the family of `address`."
}
]
}
]
}
],
"desc": "Resolves a hostname (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 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 'ENOENT'
not only when\nthe hostname 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('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
: Returned address types are determined by the types\nof addresses supported by the current system. For example, IPv4 addresses\nare only returned if the current system has at least one IPv4 address\nconfigured. Loopback addresses are not considered.dns.V4MAPPED
: If the IPv6 family was specified, but no IPv6 addresses were\nfound, then return IPv4 mapped IPv6 addresses. Note that it is not supported\non some operating systems (e.g FreeBSD 10.1).Resolves the given address
and port
into a hostname 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('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 hostname (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
'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 a 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
"
},
{
"textRaw": "dns.resolveCname(hostname, callback)",
"type": "method",
"name": "resolveCname",
"meta": {
"added": [
"v0.3.2"
],
"changes": []
},
"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 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 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": []
},
"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": []
},
"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": []
},
"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": "`records` {string[][]}",
"name": "records",
"type": "string[][]"
}
]
}
]
}
],
"desc": "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 hostnames.
\nOn error, err
is an Error
object, where err.code
is\none of the DNS error codes.
Sets the IP address and port of servers to be used when performing DNS\nresolution. The servers
argument is an array of rfc5952 formatted\naddresses. If the port is the IANA default DNS port (53) it can be omitted.
dns.setServers([\n '4.4.4.4',\n '[2001:4860:4860::8888]',\n '4.4.4.4:1053',\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.
Note that 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('dns').promises
.
An independent resolver for DNS requests.
\nNote that creating 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('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.resolveCname()
resolver.resolveMx()
resolver.resolveNaptr()
resolver.resolveNs()
resolver.resolvePtr()
resolver.resolveSoa()
resolver.resolveSrv()
resolver.resolveTxt()
resolver.reverse()
resolver.setServers()
Returns an array of IP address strings, formatted according to rfc5952,\nthat are currently configured for DNS resolution. A string will include a port\nsection if a custom port is used.
\n\n[\n '4.4.4.4',\n '2001:4860:4860::8888',\n '4.4.4.4:1053',\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` or `6`. IPv4 and IPv6 addresses are both returned by default.",
"name": "family",
"type": "integer",
"desc": "The record family. Must be `4` or `6`. IPv4 and IPv6 addresses are both returned by default."
},
{
"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. 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. 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."
}
],
"optional": true
}
]
}
],
"desc": "Resolves a hostname (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 'ENOENT'
not only when\nthe hostname 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('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 hostname 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('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} Hostname to resolve.",
"name": "hostname",
"type": "string",
"desc": "Hostname to resolve."
},
{
"textRaw": "`rrtype` {string} Resource record type. **Default:** `'A'`.",
"name": "rrtype",
"type": "string",
"default": "`'A'`",
"desc": "Resource record type.",
"optional": true
}
]
}
],
"desc": "Uses the DNS protocol to resolve a hostname (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
'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.resolveCname(hostname)",
"type": "method",
"name": "resolveCname",
"meta": {
"added": [
"v10.6.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`hostname` {string}",
"name": "hostname",
"type": "string"
}
]
}
],
"desc": "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 hostnames.
\nOn error, the Promise
is rejected with an Error
object, where err.code
\nis one of the DNS error codes.
Sets the IP address and port of servers to be used when performing DNS\nresolution. The servers
argument is an array of rfc5952 formatted\naddresses. If the port is the IANA default DNS port (53) it can be omitted.
dnsPromises.setServers([\n '4.4.4.4',\n '[2001:4860:4860::8888]',\n '4.4.4.4:1053',\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.
Note that 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 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 requested operation.dns.REFUSED
: DNS server refused query.dns.BADQUERY
: Misformatted DNS query.dns.BADNAME
: Misformatted hostname.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 hostname 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.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 note that 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.
Note that various networking APIs will call dns.lookup()
internally to resolve\nhost names. If that is an issue, consider resolving the hostname 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 than what dns.lookup()
\nuses. For instance, they do not use the configuration from /etc/hosts
.
This module is pending deprecation. Once a replacement API has been\nfinalized, this module will be fully deprecated. Most end users 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 master 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('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 // resources like crazy 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('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('cluster');\nconst PORT = +process.env.PORT || 1337;\n\nif (cluster.isMaster) {\n // A more realistic scenario would have more than 2 workers,\n // and perhaps not put the master 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 master 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('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('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 master know we're dead. This will trigger a\n // 'disconnect' in the cluster master, 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 lowlevel 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('domain');\nconst http = require('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.
Domain
is a child class of EventEmitter
. To handle the errors that it\ncatches, 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.\n // 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.\n // 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 lowlevel 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('domain');\nconst fs = require('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
\nNote that domains will not interfere with the error handling mechanisms for\nPromises, i.e. no 'error'
event will be emitted for unhandled Promise
\nrejections.
Much 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 will be 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.
const EventEmitter = require('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. It is important to 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.
const myEmitter = new MyEmitter();\nmyEmitter.on('event', function(a, b) {\n console.log(a, b, this, this === myEmitter);\n // Prints:\n // a b MyEmitter {\n // domain: null,\n // _events: { event: [Function] },\n // _eventsCount: 1,\n // _maxListeners: undefined } 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:
const 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 is important to ensure the proper sequencing of\nevents and to avoid race conditions or logic errors. When appropriate,\nlistener functions can switch to an asynchronous mode of operation using\nthe setImmediate()
or process.nextTick()
methods:
const 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 will be invoked every time the named event is emitted.
const 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.
const 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.
const 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 domain
module is deprecated.)
As a best practice, listeners should always be added for the 'error'
events.
const 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
",
"type": "module",
"displayName": "Error events"
}
],
"classes": [
{
"textRaw": "Class: EventEmitter",
"type": "class",
"name": "EventEmitter",
"meta": {
"added": [
"v0.1.26"
],
"changes": []
},
"desc": "The EventEmitter
class is defined and exposed by the events
module:
const EventEmitter = require('events');\n
\nAll EventEmitter
s emit the event 'newListener'
when new listeners are\nadded and 'removeListener'
when existing listeners are removed.
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 will be 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 will be inserted before the\nlistener that is in the process of being added.
const 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.
A class method that returns the number of listeners for the given eventName
\nregistered on the given emitter
.
const myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {});\nmyEmitter.on('event', () => {});\nconsole.log(EventEmitter.listenerCount(myEmitter, 'event'));\n// Prints: 2\n
"
},
{
"textRaw": "emitter.addListener(eventName, listener)",
"type": "method",
"name": "addListener",
"meta": {
"added": [
"v0.1.26"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`eventName` {string|symbol}",
"name": "eventName",
"type": "string|symbol"
},
{
"textRaw": "`listener` {Function}",
"name": "listener",
"type": "Function"
}
]
}
],
"desc": "Alias for emitter.on(eventName, listener)
.
...args
<any>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.
Returns an array listing the events for which the emitter has registered\nlisteners. The values in the array will be strings or Symbol
s.
const EventEmitter = require('events');\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\nEventEmitter.defaultMaxListeners
.
Returns the number of listeners listening to the event named eventName
.
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.
const 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.
const 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
.
Note that 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.
Note that once an event has been emitted, all listeners attached to it at the\ntime of emitting will be 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 will behave as expected.
const 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:
const 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. Obviously, not all events should be limited to just 10 listeners.\nThe emitter.setMaxListeners()
method allows the limit to be modified for this\nspecific EventEmitter
instance. The value can be set to Infinity
(or 0
)\nto 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()
).
const 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
"
}
],
"properties": [
{
"textRaw": "EventEmitter.defaultMaxListeners",
"name": "defaultMaxListeners",
"meta": {
"added": [
"v0.11.2"
],
"changes": []
},
"desc": "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 EventEmitter.defaultMaxListeners
\nproperty can be used. If this value is not a positive number, a TypeError
\nwill be thrown.
Take caution when setting the EventEmitter.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 EventEmitter.defaultMaxListeners
.
Note that 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:
emitter.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'
.
The fs
module provides an API for interacting with the file system in a\nmanner closely modeled around standard POSIX functions.
To use this module:
\nconst fs = require('fs');\n
\nAll file system operations have synchronous and asynchronous forms.
\nThe asynchronous form always takes a completion callback as its last argument.\nThe arguments passed to the completion callback depend on the method, but the\nfirst argument is always reserved for an exception. If the operation was\ncompleted successfully, then the first argument will be null
or undefined
.
const fs = require('fs');\n\nfs.unlink('/tmp/hello', (err) => {\n if (err) throw err;\n console.log('successfully deleted /tmp/hello');\n});\n
\nExceptions that occur using synchronous operations are thrown immediately and\nmay be handled using try
/catch
, or may be allowed to bubble up.
const fs = require('fs');\n\ntry {\n fs.unlinkSync('/tmp/hello');\n console.log('successfully deleted /tmp/hello');\n} catch (err) {\n // handle the error\n}\n
\nThere is no guaranteed ordering when using asynchronous methods. So the\nfollowing is prone to error because the fs.stat()
operation may complete\nbefore the fs.rename()
operation:
fs.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
\nTo correctly order the operations, move the fs.stat()
call into the callback\nof the fs.rename()
operation:
fs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n fs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n });\n});\n
\nIn busy processes, the programmer is strongly encouraged to use the\nasynchronous versions of these calls. The synchronous versions will block\nthe entire process until they complete — halting all connections.
\nWhile it is not recommended, most fs functions allow the callback argument to\nbe omitted, in which case a default callback is used that rethrows errors. To\nget a trace to the original call site, set the NODE_DEBUG
environment\nvariable:
Omitting the callback function on asynchronous fs functions is deprecated and\nmay result in an error being thrown in the future.
\n$ cat script.js\nfunction bad() {\n require('fs').readFile('/');\n}\nbad();\n\n$ env NODE_DEBUG=fs node script.js\nfs.js:88\n throw backtrace;\n ^\nError: EISDIR: illegal operation on a directory, read\n <stack trace.>\n
",
"modules": [
{
"textRaw": "File paths",
"name": "file_paths",
"desc": "Most fs
operations accept filepaths that may be specified in the form of\na string, a Buffer
, or a URL
object using the file:
protocol.
String form 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 specified by process.cwd()
.
Example using an absolute path on POSIX:
\nconst fs = require('fs');\n\nfs.open('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\n
\nExample using a relative path on POSIX (relative to process.cwd()
):
fs.open('file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\n
\nPaths 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:
Example using an absolute path on POSIX:
\nfs.open(Buffer.from('/open/some/file.txt'), 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\n
\nOn 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.
For most fs
module functions, the path
or filename
argument may be passed\nas a WHATWG URL
object. Only URL
objects using the file:
protocol\nare supported.
const fs = require('fs');\nconst fileUrl = new URL('file:///tmp/hello');\n\nfs.readFileSync(fileUrl);\n
\nfile:
URLs are always absolute paths.
Using WHATWG URL
objects might introduce platform-specific behaviors.
On Windows, file:
URLs with a hostname convert to UNC paths, while file:
\nURLs with drive letters convert to local absolute paths. file:
URLs without a\nhostname nor a drive letter will result in a throw:
// 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\nfs.readFileSync(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\nfs.readFileSync(new URL('file:///C:/tmp/hello'));\n\n// - WHATWG file URLs without hostname must have a drive letters\nfs.readFileSync(new URL('file:///notdriveletter/p/a/t/h/file'));\nfs.readFileSync(new URL('file:///c/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must be absolute\n
\nfile:
URLs with drive letters must use :
as a separator just after\nthe drive letter. Using another separator will result in a throw.
On all other platforms, file:
URLs with a hostname are unsupported and will\nresult in a throw:
// On other platforms:\n\n// - WHATWG file URLs with hostname are unsupported\n// file://hostname/p/a/t/h/file => throw!\nfs.readFileSync(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\nfs.readFileSync(new URL('file:///tmp/hello'));\n
\nA file:
URL having encoded slash characters will result in a throw on all\nplatforms:
// On Windows\nfs.readFileSync(new URL('file:///C:/p/a/t/h/%2F'));\nfs.readFileSync(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\nfs.readFileSync(new URL('file:///p/a/t/h/%2F'));\nfs.readFileSync(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:
URLs having encoded backslash will result in a throw:
// On Windows\nfs.readFileSync(new URL('file:///C:/path/%5C'));\nfs.readFileSync(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": "URL object support"
}
],
"type": "module",
"displayName": "File paths"
},
{
"textRaw": "File Descriptors",
"name": "file_descriptors",
"desc": "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\nspecific differences between operating systems and assigns all open files a\nnumeric file descriptor.
\nThe fs.open()
method is used to allocate a new file descriptor. Once\nallocated, the file descriptor may be used to read data from, write data to,\nor request information about the file.
fs.open('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.fstat(fd, (err, stat) => {\n if (err) throw err;\n // use stat\n\n // always close the file descriptor!\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n });\n});\n
\nMost 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.
", "type": "module", "displayName": "File Descriptors" }, { "textRaw": "Threadpool Usage", "name": "threadpool_usage", "desc": "All file system APIs except fs.FSWatcher()
and those that are explicitly\nsynchronous use libuv's threadpool, which can have surprising and negative\nperformance implications for some applications. See the\nUV_THREADPOOL_SIZE
documentation for more information.
The fs.promises
API provides an alternative set of asynchronous file system\nmethods that return Promise
objects rather than using callbacks. The\nAPI is accessible via require('fs').promises
.
A FileHandle
object is a wrapper for a numeric file descriptor.\nInstances of FileHandle
are distinct from numeric file descriptors\nin that, if the FileHandle
is not explicitly closed using the\nfilehandle.close()
method, they will automatically close the file descriptor\nand will emit a process warning, thereby helping to prevent memory leaks.
Instances of the FileHandle
object are created internally by the\nfsPromises.open()
method.
Unlike the callback-based API (fs.fstat()
, fs.fchown()
, fs.fchmod()
, and\nso on), a numeric file descriptor is not used by the promise-based API. Instead,\nthe promise-based API uses the FileHandle
class in order to help avoid\naccidental leaking of unclosed file descriptors after a Promise
is resolved or\nrejected.
Asynchronously append data to this file, creating the file if it does not yet\nexist. data
can be a string or a Buffer
. The Promise
will be\nresolved with no arguments upon success.
If options
is a string, then it specifies the encoding.
The FileHandle
must have been opened for appending.
Modifies the permissions on the file. The Promise
is resolved with no\narguments upon success.
Changes the ownership of the file then resolves the Promise
with no arguments\nupon success.
Closes the file descriptor.
\nconst fsPromises = require('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
"
},
{
"textRaw": "filehandle.datasync()",
"type": "method",
"name": "datasync",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise}",
"name": "return",
"type": "Promise"
},
"params": []
}
],
"desc": "Asynchronous fdatasync(2)
. The Promise
is resolved with no arguments upon\nsuccess.
Read data from the file.
\nbuffer
is the buffer that the data will be written to.
offset
is the offset in the buffer to start writing at.
length
is an integer specifying the number of bytes to read.
position
is an argument specifying where to begin reading from in the file.\nIf position
is null
, data will be read from the current file position,\nand the file position will be updated.\nIf position
is an integer, the file position will remain unchanged.
Following successful read, the Promise
is resolved with an object with a\nbytesRead
property specifying the number of bytes read, and a buffer
\nproperty that is a reference to the passed in buffer
argument.
Asynchronously reads the entire contents of a file.
\nThe Promise
is resolved with the contents of the file. If no encoding is\nspecified (using options.encoding
), the data is returned as a Buffer
\nobject. 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.
The FileHandle
has to support reading.
If 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.
Retrieves the fs.Stats
for the file.
Asynchronous fsync(2)
. The Promise
is resolved with no arguments upon\nsuccess.
Truncates the file then resolves the Promise
with no arguments upon success.
If the file was larger than len
bytes, only the first len
bytes will be\nretained in the file.
For example, the following program retains only the first four bytes of the\nfile:
\nconst fs = require('fs');\nconst fsPromises = fs.promises;\n\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\nasync function doTruncate() {\n let filehandle = null;\n try {\n filehandle = await fsPromises.open('temp.txt', 'r+');\n await filehandle.truncate(4);\n } finally {\n if (filehandle) {\n // close the file if it is opened.\n await filehandle.close();\n }\n }\n console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints: Node\n}\n\ndoTruncate().catch(console.error);\n
\nIf the file previously was shorter than len
bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'
):
const fs = require('fs');\nconst fsPromises = fs.promises;\n\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\nasync function doTruncate() {\n let filehandle = null;\n try {\n filehandle = await fsPromises.open('temp.txt', 'r+');\n await filehandle.truncate(10);\n } finally {\n if (filehandle) {\n // close the file if it is opened.\n await filehandle.close();\n }\n }\n console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints Node.js\\0\\0\\0\n}\n\ndoTruncate().catch(console.error);\n
\nThe last three bytes are null bytes ('\\0'
), to compensate the over-truncation.
Change the file system timestamps of the object referenced by the FileHandle
\nthen resolves the Promise
with no arguments upon success.
This function does not work on AIX versions before 7.1, it will resolve the\nPromise
with an error using code UV_ENOSYS
.
Write buffer
to the file.
The Promise
is resolved with an object containing a bytesWritten
property\nidentifying the number of bytes written, and a buffer
property containing\na reference to the buffer
written.
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)
.
It is unsafe to use filehandle.write()
multiple times on the same file\nwithout waiting for the Promise
to be resolved (or rejected). For this\nscenario, fs.createWriteStream()
is strongly recommended.
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(string[, position[, encoding]])", "type": "method", "name": "write", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`string` {string}", "name": "string", "type": "string" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer", "optional": true }, { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`", "optional": true } ] } ], "desc": "Write string
to the file. If string
is not a string, then\nthe value will be coerced to one.
The Promise
is resolved with an object containing a bytesWritten
property\nidentifying the number of bytes written, and a buffer
property containing\na reference to the string
written.
position
refers to the offset from the beginning of the file where this data\nshould be written. If the type of position
is not a number
the data\nwill be written at the current position. See pwrite(2)
.
encoding
is the expected string encoding.
It is unsafe to use filehandle.write()
multiple times on the same file\nwithout waiting for the Promise
to be resolved (or rejected). For this\nscenario, fs.createWriteStream()
is strongly recommended.
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": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`data` {string|Buffer|Uint8Array}", "name": "data", "type": "string|Buffer|Uint8Array" }, { "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:** `'w'`.", "name": "flag", "type": "string", "default": "`'w'`", "desc": "See [support of file system `flags`][]." } ] } ] } ], "desc": "Asynchronously writes data to a file, replacing the file if it already exists.\ndata
can be a string or a buffer. The Promise
will be resolved with no\narguments upon success.
The encoding
option is ignored if data
is a buffer.
If options
is a string, then it specifies the encoding.
The FileHandle
has to support writing.
It is unsafe to use filehandle.writeFile()
multiple times on the same file\nwithout waiting for the Promise
to be resolved (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.
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. Check File Access Constants for possible values\nof mode
. It is possible to create a mask consisting of the bitwise OR of\ntwo or more values (e.g. fs.constants.W_OK | fs.constants.R_OK
).
If the accessibility check is successful, the Promise
is resolved 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.
const fs = require('fs');\nconst fsPromises = fs.promises;\n\nfsPromises.access('/etc/passwd', fs.constants.R_OK | fs.constants.W_OK)\n .then(() => console.log('can access'))\n .catch(() => console.error('cannot access'));\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
. The Promise
will be\nresolved with no arguments upon success.
If options
is a string, then it specifies the encoding.
The path
may be specified as a FileHandle
that has been opened\nfor appending (using fsPromises.open()
).
Changes the permissions of a file then resolves the Promise
with no\narguments upon succces.
Changes the ownership of a file then resolves the Promise
with no arguments\nupon success.
Asynchronously copies src
to dest
. By default, dest
is overwritten if it\nalready exists. The Promise
will be resolved with no arguments upon success.
Node.js makes no guarantees about the atomicity of the copy operation. If an\nerror occurs after the destination file has been opened for writing, Node.js\nwill attempt to remove the destination.
\nflags
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 copy-on-write,\nthen the operation will fail.const fsPromises = require('fs').promises;\n\n// destination.txt will be created or overwritten by default.\nfsPromises.copyFile('source.txt', 'destination.txt')\n .then(() => console.log('source.txt was copied to destination.txt'))\n .catch(() => console.log('The file could not be copied'));\n
\nIf the third argument is a number, then it specifies flags
:
const fs = require('fs');\nconst fsPromises = fs.promises;\nconst { COPYFILE_EXCL } = fs.constants;\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfsPromises.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL)\n .then(() => console.log('source.txt was copied to destination.txt'))\n .catch(() => console.log('The file could not be copied'));\n
"
},
{
"textRaw": "fsPromises.lchmod(path, mode)",
"type": "method",
"name": "lchmod",
"meta": {
"deprecated": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Promise}",
"name": "return",
"type": "Promise"
},
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`mode` {integer}",
"name": "mode",
"type": "integer"
}
]
}
],
"desc": "Changes the permissions on a symbolic link then resolves the Promise
with\nno arguments upon success. This method is only implemented on macOS.
Changes the ownership on a symbolic link then resolves the Promise
with\nno arguments upon success.
Asynchronous link(2)
. The Promise
is resolved with no arguments upon success.
Asynchronous lstat(2)
. The Promise
is resolved with the fs.Stats
object\nfor the given symbolic link path
.
Asynchronously creates a directory then resolves the Promise
with no\narguments upon success.
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 folders should be created.
Creates a unique temporary directory and resolves the Promise
with the created\nfolder path. A unique directory name is generated by appending six random\ncharacters to the end of the provided prefix
.
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use.
fsPromises.mkdtemp(path.join(os.tmpdir(), 'foo-'))\n .catch(console.error);\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('path').sep
).
Asynchronous file open that returns a Promise
that, when resolved, yields a\nFileHandle
object. See open(2)
.
mode
sets the file mode (permission and sticky bits), but only if the file was\ncreated.
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.
Reads the contents of a directory then resolves the Promise
with an array\nof the names of the files in the directory excluding '.'
and '..'
.
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. If the encoding
is set to 'buffer'
, the filenames returned\nwill be passed as Buffer
objects.
If options.withFileTypes
is set to true
, the resolved array will contain\nfs.Dirent
objects.
Asynchronously reads the entire contents of a file.
\nThe Promise
is resolved with the contents of the file. If no encoding is\nspecified (using options.encoding
), the data is returned as a Buffer
\nobject. 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.
Any specified FileHandle
has to support reading.
Asynchronous readlink(2)
. The Promise
is resolved with the linkString
upon\nsuccess.
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 then resolves the Promise
with the resolved\npath.
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
and resolves the Promise
with no arguments\nupon success.
Removes the directory identified by path
then resolves the Promise
with\nno arguments upon success.
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.
The Promise
is resolved with the fs.Stats
object for the given path
.
Creates a symbolic link then resolves the Promise
with no arguments upon\nsuccess.
The type
argument is only used on Windows platforms and can be one of 'dir'
,\n'file'
, or 'junction'
. Windows junction points require the destination path\nto be absolute. When using 'junction'
, the target
argument will\nautomatically be normalized to absolute path.
Truncates the path
then resolves the Promise
with no arguments upon\nsuccess. The path
must be a string or Buffer
.
Asynchronous unlink(2)
. The Promise
is resolved with no arguments upon\nsuccess.
Change the file system timestamps of the object referenced by path
then\nresolves the Promise
with no arguments upon success.
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.Asynchronously writes data to a file, replacing the file if it already exists.\ndata
can be a string or a buffer. The Promise
will be resolved with no\narguments upon success.
The encoding
option is ignored if data
is a buffer.
If options
is a string, then it specifies the encoding.
Any specified FileHandle
has to support writing.
It is unsafe to use fsPromises.writeFile()
multiple times on the same file\nwithout waiting for the Promise
to be resolved (or rejected).
The following constants are exported by fs.constants
.
Not every constant will be available on every operating system.
", "modules": [ { "textRaw": "File Access Constants", "name": "file_access_constants", "desc": "The following constants are meant for use with fs.access()
.
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 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 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
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
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
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.
'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)
) ensures that path is newly\ncreated. On POSIX systems, path is considered to exist even if it is a symlink\nto a non-existent file. The exclusive flag may or may not work with network\nfile 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 a flags mode of 'r+'
\nrather than the default mode 'w'
.
The behavior of some flags are platform-specific. As such, opening a directory\non macOS and Linux with the 'a+'
flag - see 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()
or 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.
When fs.readdir()
or fs.readdirSync()
is called with the\nwithFileTypes
option set to true
, the resulting array is filled with\nfs.Dirent
objects, rather than strings or Buffers
.
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()
.
A successful call to fs.watch()
method will return a new fs.FSWatcher
\nobject.
All fs.FSWatcher
objects are EventEmitter
's that will emit a 'change'
\nevent whenever a specific watched file 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.
// Example when handled through fs.watch() listener\nfs.watch('./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\nfs.FSWatcher
object is no longer usable in the event handler.
Emitted when an error occurs while watching the file. The errored\nfs.FSWatcher
object is no longer usable in the event handler.
Stop watching for changes on the given fs.FSWatcher
. Once stopped, the\nfs.FSWatcher
object is no longer usable.
A successful call to fs.createReadStream()
will return a new fs.ReadStream
\nobject.
All fs.ReadStream
objects are Readable Streams.
Emitted when the fs.ReadStream
's underlying file descriptor has been closed.
Emitted when the fs.ReadStream
's file descriptor has been opened.
Emitted when the fs.ReadStream
is ready to be used.
Fires 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
.
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.
Objects returned from fs.stat()
, fs.lstat()
and 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
.
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:
Stats {\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 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.
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 is considered \"special\".
" }, { "textRaw": "`size` {number|bigint}", "type": "number|bigint", "name": "size", "desc": "The size of the file in bytes.
" }, { "textRaw": "`blksize` {number|bigint}", "type": "number|bigint", "name": "blksize", "desc": "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": "`atime` {Date}", "type": "Date", "name": "atime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "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\nnumbers that hold the corresponding times in milliseconds. Their\nprecision 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 filesystems 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.
WriteStream
is a Writable Stream.
Emitted when the WriteStream
's underlying file descriptor has been closed.
Emitted when the WriteStream
's file is opened.
Emitted when the fs.WriteStream
is ready to be used.
Fires 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.
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. Check File Access Constants for possible values\nof mode
. It is possible to create a mask consisting of the bitwise OR of\ntwo or more values (e.g. fs.constants.W_OK | fs.constants.R_OK
).
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.
const file = 'package.json';\n\n// Check if the file exists in the current directory.\nfs.access(file, fs.constants.F_OK, (err) => {\n console.log(`${file} ${err ? 'does not exist' : 'exists'}`);\n});\n\n// Check if the file is readable.\nfs.access(file, fs.constants.R_OK, (err) => {\n console.log(`${file} ${err ? 'is not readable' : 'is readable'}`);\n});\n\n// Check if the file is writable.\nfs.access(file, fs.constants.W_OK, (err) => {\n console.log(`${file} ${err ? 'is not writable' : 'is writable'}`);\n});\n\n// Check if the file exists in the current directory, and if it is writable.\nfs.access(file, fs.constants.F_OK | fs.constants.W_OK, (err) => {\n if (err) {\n console.error(\n `${file} ${err.code === 'ENOENT' ? 'does not exist' : 'is read-only'}`);\n } else {\n console.log(`${file} exists, and it is writable`);\n }\n});\n
\nUsing fs.access()
to check for the accessibility 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 is not accessible.
write (NOT RECOMMENDED)
\nfs.access('myfile', (err) => {\n if (!err) {\n console.error('myfile already exists');\n return;\n }\n\n fs.open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n writeMyData(fd);\n });\n});\n
\nwrite (RECOMMENDED)
\nfs.open('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 writeMyData(fd);\n});\n
\nread (NOT RECOMMENDED)
\nfs.access('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 fs.open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n readMyData(fd);\n });\n});\n
\nread (RECOMMENDED)
\nfs.open('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 readMyData(fd);\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.
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. Check File Access Constants for\npossible values of mode
. It is possible to create a mask consisting of\nthe bitwise OR of two or more values\n(e.g. fs.constants.W_OK | fs.constants.R_OK
).
If any of the accessibility checks fail, an Error
will be thrown. Otherwise,\nthe method will return undefined
.
try {\n fs.accessSync('etc/passwd', fs.constants.R_OK | fs.constants.W_OK);\n console.log('can read/write');\n} catch (err) {\n console.error('no access!');\n}\n
"
},
{
"textRaw": "fs.appendFile(path, data[, options], callback)",
"type": "method",
"name": "appendFile",
"meta": {
"added": [
"v0.6.7"
],
"changes": [
{
"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."
},
{
"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`][]."
}
],
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
}
]
}
]
}
],
"desc": "Asynchronously append data to a file, creating the file if it does not yet\nexist. data
can be a string or a Buffer
.
fs.appendFile('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:
fs.appendFile('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.
fs.open('message.txt', 'a', (err, fd) => {\n if (err) throw err;\n fs.appendFile(fd, 'data to append', 'utf8', (err) => {\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n if (err) throw err;\n });\n});\n
"
},
{
"textRaw": "fs.appendFileSync(path, data[, options])",
"type": "method",
"name": "appendFileSync",
"meta": {
"added": [
"v0.6.7"
],
"changes": [
{
"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`][]."
}
],
"optional": true
}
]
}
],
"desc": "Synchronously append data to a file, creating the file if it does not yet\nexist. data
can be a string or a Buffer
.
try {\n fs.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:
fs.appendFileSync('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.
let fd;\n\ntry {\n fd = fs.openSync('message.txt', 'a');\n fs.appendFileSync(fd, 'data to append', 'utf8');\n} catch (err) {\n /* Handle the error */\n} finally {\n if (fd !== undefined)\n fs.closeSync(fd);\n}\n
"
},
{
"textRaw": "fs.chmod(path, mode, callback)",
"type": "method",
"name": "chmod",
"meta": {
"added": [
"v0.1.30"
],
"changes": [
{
"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. 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": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`mode` {integer}",
"name": "mode",
"type": "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 also: chmod(2)
.
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 not\nexposed 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.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. Support is currently still *experimental*." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer}", "name": "mode", "type": "integer" } ] } ], "desc": "For detailed information, see the documentation of the asynchronous version of\nthis API: fs.chmod()
.
See also: chmod(2)
.
Asynchronously changes owner and group of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee also: chown(2)
.
Synchronously changes owner and group of a file. Returns undefined
.\nThis is the synchronous version of fs.chown()
.
See also: chown(2)
.
Asynchronous close(2)
. No arguments other than a possible exception are given\nto the completion callback.
Synchronous close(2)
. Returns undefined
.
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.
flags
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 copy-on-write,\nthen the operation will fail.const fs = require('fs');\n\n// destination.txt will be created or overwritten by default.\nfs.copyFile('source.txt', 'destination.txt', (err) => {\n if (err) throw err;\n console.log('source.txt was copied to destination.txt');\n});\n
\nIf the third argument is a number, then it specifies flags
:
const fs = require('fs');\nconst { COPYFILE_EXCL } = fs.constants;\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfs.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL, callback);\n
"
},
{
"textRaw": "fs.copyFileSync(src, dest[, flags])",
"type": "method",
"name": "copyFileSync",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"signatures": [
{
"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": "`flags` {number} modifiers for copy operation. **Default:** `0`.",
"name": "flags",
"type": "number",
"default": "`0`",
"desc": "modifiers for copy operation.",
"optional": true
}
]
}
],
"desc": "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.
flags
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 copy-on-write,\nthen the operation will fail.const fs = require('fs');\n\n// destination.txt will be created or overwritten by default.\nfs.copyFileSync('source.txt', 'destination.txt');\nconsole.log('source.txt was copied to destination.txt');\n
\nIf the third argument is a number, then it specifies flags
:
const fs = require('fs');\nconst { COPYFILE_EXCL } = fs.constants;\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfs.copyFileSync('source.txt', 'destination.txt', COPYFILE_EXCL);\n
"
},
{
"textRaw": "fs.createReadStream(path[, options])",
"type": "method",
"name": "createReadStream",
"meta": {
"added": [
"v0.1.31"
],
"changes": [
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/19898",
"description": "Impose new restrictions on `start` and `end`, throwing more appropriate errors in cases when we cannot reasonably handle the input values."
},
{
"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. Support is currently still *experimental*."
},
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/7831",
"description": "The passed `options` object will never be modified."
},
{
"version": "v2.3.0",
"pr-url": "https://github.com/nodejs/node/pull/1845",
"description": "The passed `options` object can be a string now."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {fs.ReadStream} See [Readable Streams][].",
"name": "return",
"type": "fs.ReadStream",
"desc": "See [Readable Streams][]."
},
"params": [
{
"textRaw": "`path` {string|Buffer|URL}",
"name": "path",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {string|Object}",
"name": "options",
"type": "string|Object",
"options": [
{
"textRaw": "`flags` {string} See [support of file system `flags`][]. **Default:** `'r'`.",
"name": "flags",
"type": "string",
"default": "`'r'`",
"desc": "See [support of file system `flags`][]."
},
{
"textRaw": "`encoding` {string} **Default:** `null`",
"name": "encoding",
"type": "string",
"default": "`null`"
},
{
"textRaw": "`fd` {integer} **Default:** `null`",
"name": "fd",
"type": "integer",
"default": "`null`"
},
{
"textRaw": "`mode` {integer} **Default:** `0o666`",
"name": "mode",
"type": "integer",
"default": "`0o666`"
},
{
"textRaw": "`autoClose` {boolean} **Default:** `true`",
"name": "autoClose",
"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`"
}
],
"optional": true
}
]
}
],
"desc": "Unlike the 16 kb default highWaterMark
for a readable stream, the stream\nreturned by this method has a default highWaterMark
of 64 kb.
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. If fd
is specified and start
is omitted or undefined
,\nfs.createReadStream()
reads sequentially from the current file position.\nThe encoding
can be any one of those accepted by 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\nnet.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.
const fs = require('fs');\n// Create a stream from some character device.\nconst stream = fs.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:
\nfs.createReadStream('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\nsome position past the beginning of the file. Modifying a file rather\nthan replacing it may require a flags
mode of r+
rather than the\ndefault mode w
. The encoding
can be any one of those accepted by\nBuffer
.
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.
Like ReadStream
, if fd
is specified, 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:
fs.exists('/etc/passwd', (exists) => {\n console.log(exists ? 'it\\'s there' : '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)
\nfs.exists('myfile', (exists) => {\n if (exists) {\n console.error('myfile already exists');\n } else {\n fs.open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n writeMyData(fd);\n });\n }\n});\n
\nwrite (RECOMMENDED)
\nfs.open('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 writeMyData(fd);\n});\n
\nread (NOT RECOMMENDED)
\nfs.exists('myfile', (exists) => {\n if (exists) {\n fs.open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n readMyData(fd);\n });\n } else {\n console.error('myfile does not exist');\n }\n});\n
\nread (RECOMMENDED)
\nfs.open('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 readMyData(fd);\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.existsSync(path)", "type": "method", "name": "existsSync", "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. Support is currently still *experimental*." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" } ] } ], "desc": "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.
Asynchronous fchmod(2)
. No arguments other than a possible exception\nare given to the completion callback.
Synchronous fchmod(2)
. Returns undefined
.
Asynchronous fchown(2)
. No arguments other than a possible exception are given\nto the completion callback.
Synchronous fchown(2)
. Returns undefined
.
Asynchronous fdatasync(2)
. No arguments other than a possible exception are\ngiven to the completion callback.
Synchronous fdatasync(2)
. Returns undefined
.
Asynchronous fstat(2)
. The callback gets two arguments (err, stats)
where\nstats
is an fs.Stats
object. fstat()
is identical to stat()
,\nexcept that the file to be stat-ed is specified by the file descriptor fd
.
Synchronous fstat(2)
.
Asynchronous fsync(2)
. No arguments other than a possible exception are given\nto the completion callback.
Synchronous fsync(2)
. Returns undefined
.
Asynchronous ftruncate(2)
. No arguments other than a possible exception are\ngiven to the completion callback.
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:
\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\n// get the file descriptor of the file to be truncated\nconst fd = fs.openSync('temp.txt', 'r+');\n\n// truncate the file to first four bytes\nfs.ftruncate(fd, 4, (err) => {\n assert.ifError(err);\n console.log(fs.readFileSync('temp.txt', 'utf8'));\n});\n// Prints: Node\n
\nIf the file previously was shorter than len
bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'
):
console.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\n// get the file descriptor of the file to be truncated\nconst fd = fs.openSync('temp.txt', 'r+');\n\n// Truncate the file to 10 bytes, whereas the actual size is 7 bytes\nfs.ftruncate(fd, 10, (err) => {\n assert.ifError(err);\n console.log(fs.readFileSync('temp.txt'));\n});\n// Prints: <Buffer 4e 6f 64 65 2e 6a 73 00 00 00>\n// ('Node.js\\0\\0\\0' in UTF8)\n
\nThe last three bytes are null bytes ('\\0'
), to compensate the over-truncation.
Returns undefined
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.ftruncate()
.
Change the file system timestamps of the object referenced by the supplied file\ndescriptor. See fs.utimes()
.
This function does not work on AIX versions before 7.1, it will return the\nerror UV_ENOSYS
.
Synchronous version of fs.futimes()
. Returns undefined
.
Asynchronous lchmod(2)
. No arguments other than a possible exception\nare given to the completion callback.
Only available on macOS.
" }, { "textRaw": "fs.lchmodSync(path, mode)", "type": "method", "name": "lchmodSync", "meta": { "deprecated": [ "v0.4.7" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer}", "name": "mode", "type": "integer" } ] } ], "desc": "Synchronous lchmod(2)
. Returns undefined
.
Asynchronous lchown(2)
. No arguments other than a possible exception are given\nto the completion callback.
Synchronous lchown(2)
. Returns undefined
.
Asynchronous link(2)
. No arguments other than a possible exception are given to\nthe completion callback.
Synchronous link(2)
. Returns undefined
.
Asynchronous lstat(2)
. The callback gets two arguments (err, stats)
where\nstats
is a fs.Stats
object. lstat()
is identical to stat()
,\nexcept that if path
is a symbolic link, then the link itself is stat-ed,\nnot the file that it refers to.
Synchronous lstat(2)
.
Asynchronously creates a directory. No arguments other than a possible exception\nare given to the completion callback.
\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 folders should be created.
// Creates /tmp/a/apple, regardless of whether `/tmp` and /tmp/a exist.\nfs.mkdir('/tmp/a/apple', { recursive: true }, (err) => {\n if (err) throw err;\n});\n
\nSee also: mkdir(2)
.
Synchronously creates a directory. Returns undefined
.\nThis is the synchronous version of fs.mkdir()
.
See also: mkdir(2)
.
Creates a unique temporary directory.
\nGenerates six random characters to be appended behind a required\nprefix
to create a unique temporary directory.
The created folder 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.
fs.mkdtemp(path.join(os.tmpdir(), 'foo-'), (err, folder) => {\n if (err) throw err;\n console.log(folder);\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('path').sep
).
// The parent directory for the new temporary directory\nconst tmpDir = os.tmpdir();\n\n// This method is *INCORRECT*:\nfs.mkdtemp(tmpDir, (err, folder) => {\n if (err) throw err;\n console.log(folder);\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*:\nconst { sep } = require('path');\nfs.mkdtemp(`${tmpDir}${sep}`, (err, folder) => {\n if (err) throw err;\n console.log(folder);\n // Will print something similar to `/tmp/abc123`.\n // A new temporary directory is created within\n // the /tmp directory.\n});\n
"
},
{
"textRaw": "fs.mkdtempSync(prefix[, options])",
"type": "method",
"name": "mkdtempSync",
"meta": {
"added": [
"v5.10.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {string}",
"name": "return",
"type": "string"
},
"params": [
{
"textRaw": "`prefix` {string}",
"name": "prefix",
"type": "string"
},
{
"textRaw": "`options` {string|Object}",
"name": "options",
"type": "string|Object",
"options": [
{
"textRaw": "`encoding` {string} **Default:** `'utf8'`",
"name": "encoding",
"type": "string",
"default": "`'utf8'`"
}
],
"optional": true
}
]
}
],
"desc": "Returns the created folder 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.
Asynchronous file open. See open(2)
.
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 an integer representing the file descriptor.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.open()
.
Read data from the file specified by fd
.
buffer
is the buffer that the data will be written to.
offset
is the offset in the buffer to start writing at.
length
is an integer specifying the number of bytes to read.
position
is an argument specifying where to begin reading from in the file.\nIf position
is null
, data will be read from the current file position,\nand the file position will be updated.\nIf position
is an integer, the file position will remain unchanged.
The callback is given the three arguments, (err, bytesRead, buffer)
.
If this method is invoked as its util.promisify()
ed version, it returns\na Promise
for an Object
with bytesRead
and buffer
properties.
Asynchronous readdir(3)
. Reads the contents of a directory.\nThe callback gets two arguments (err, files)
where files
is an array of\nthe names of the files in the directory excluding '.'
and '..'
.
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\nfs.Dirent
objects.
Synchronous readdir(3)
.
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\nfs.Dirent
objects.
Asynchronously reads the entire contents of a file.
\nfs.readFile('/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:
fs.readFile('/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.
// macOS, Linux, and Windows\nfs.readFile('<directory>', (err, data) => {\n // => [Error: EISDIR: illegal operation on a directory, read <directory>]\n});\n\n// FreeBSD\nfs.readFile('<directory>', (err, data) => {\n // => null, <data>\n});\n
\nThe fs.readFile()
function buffers the entire file. To minimize memory costs,\nwhen possible prefer streaming via fs.createReadStream()
.
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'
.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.
// macOS, Linux, and Windows\nfs.readFileSync('<directory>');\n// => [Error: EISDIR: illegal operation on a directory, read <directory>]\n\n// FreeBSD\nfs.readFileSync('<directory>'); // => <data>\n
"
},
{
"textRaw": "fs.readlink(path[, options], callback)",
"type": "method",
"name": "readlink",
"meta": {
"added": [
"v0.1.31"
],
"changes": [
{
"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. 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": "`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'`"
}
],
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"options": [
{
"textRaw": "`err` {Error}",
"name": "err",
"type": "Error"
},
{
"textRaw": "`linkString` {string|Buffer}",
"name": "linkString",
"type": "string|Buffer"
}
]
}
]
}
],
"desc": "Asynchronous readlink(2)
. The callback gets two arguments (err, linkString)
.
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.
Synchronous readlink(2)
. Returns the symbolic link's string value.
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()
.
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.
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.
Asynchronously rename file at oldPath
to the pathname provided\nas newPath
. In the case that newPath
already exists, it will\nbe overwritten. No arguments other than a possible exception are\ngiven to the completion callback.
See also: rename(2)
.
fs.rename('oldFile.txt', 'newFile.txt', (err) => {\n if (err) throw err;\n console.log('Rename complete!');\n});\n
"
},
{
"textRaw": "fs.renameSync(oldPath, newPath)",
"type": "method",
"name": "renameSync",
"meta": {
"added": [
"v0.1.21"
],
"changes": [
{
"version": "v7.6.0",
"pr-url": "https://github.com/nodejs/node/pull/10739",
"description": "The `oldPath` and `newPath` parameters can be WHATWG `URL` objects using `file:` protocol. Support is currently still *experimental*."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`oldPath` {string|Buffer|URL}",
"name": "oldPath",
"type": "string|Buffer|URL"
},
{
"textRaw": "`newPath` {string|Buffer|URL}",
"name": "newPath",
"type": "string|Buffer|URL"
}
]
}
],
"desc": "Synchronous rename(2)
. Returns undefined
.
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.
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.
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.
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.
Synchronous stat(2)
.
Asynchronous symlink(2)
. No arguments other than a possible exception are given\nto the completion callback. The type
argument can be set to 'dir'
,\n'file'
, or 'junction'
and is only available on\nWindows (ignored on other platforms). Windows junction points require the\ndestination path to be absolute. When using 'junction'
, the target
argument\nwill automatically be normalized to absolute path.
Here is an example below:
\nfs.symlink('./foo', './new-port', callback);\n
\nIt creates a symbolic link named \"new-port\" that points to \"foo\".
" }, { "textRaw": "fs.symlinkSync(target, path[, type])", "type": "method", "name": "symlinkSync", "meta": { "added": [ "v0.1.31" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `target` and `path` parameters can be WHATWG `URL` objects using `file:` protocol. Support is currently still *experimental*." } ] }, "signatures": [ { "params": [ { "textRaw": "`target` {string|Buffer|URL}", "name": "target", "type": "string|Buffer|URL" }, { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`type` {string} **Default:** `'file'`", "name": "type", "type": "string", "default": "`'file'`", "optional": true } ] } ], "desc": "Returns undefined
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.symlink()
.
Asynchronous truncate(2)
. 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.
Passing a file descriptor is deprecated and may result in an error being thrown\nin the future.
" }, { "textRaw": "fs.truncateSync(path[, len])", "type": "method", "name": "truncateSync", "meta": { "added": [ "v0.8.6" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`len` {integer} **Default:** `0`", "name": "len", "type": "integer", "default": "`0`", "optional": true } ] } ], "desc": "Synchronous truncate(2)
. 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.unlink(path, callback)", "type": "method", "name": "unlink", "meta": { "added": [ "v0.0.2" ], "changes": [ { "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. 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": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Asynchronously removes a file or symbolic link. No arguments other than a\npossible exception are given to the completion callback.
\n// Assuming that 'path/file.txt' is a regular file.\nfs.unlink('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 also: unlink(2)
.
Synchronous unlink(2)
. Returns undefined
.
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\nnumeric string like '123456789.0'
.NaN
, Infinity
or\n-Infinity
, an Error
will be thrown.Returns undefined
.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.utimes()
.
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\nfs.FSWatcher
, but it is not the same thing as the 'change'
value of\neventType
.
The fs.watch
API is not 100% consistent across platforms, and is\nunavailable in some situations.
The recursive option is only supported on macOS and Windows.
", "miscs": [ { "textRaw": "Availability", "name": "Availability", "type": "misc", "desc": "This feature depends on the underlying operating system providing a way\nto be notified of filesystem changes.
\ninotify(7)
.kqueue(2)
.kqueue(2)
for files and FSEvents
for directories.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. For example, watching files or\ndirectories can be unreliable, and in some cases impossible, on network file\nsystems (NFS, SMB, etc), or host file systems when using virtualization software\nsuch as Vagrant, Docker, etc.
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
.
fs.watch('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": "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. Support is currently still *experimental*."
}
]
},
"signatures": [
{
"params": [
{
"textRaw": "`filename` {string|Buffer|URL}",
"name": "filename",
"type": "string|Buffer|URL"
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`persistent` {boolean} **Default:** `true`",
"name": "persistent",
"type": "boolean",
"default": "`true`"
},
{
"textRaw": "`interval` {integer} **Default:** `5007`",
"name": "interval",
"type": "integer",
"default": "`5007`"
}
],
"optional": true
},
{
"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:
fs.watchFile('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
.
To be notified when the file was modified, not just accessed, it is necessary\nto compare curr.mtime
and prev.mtime
.
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). In Windows, blksize
and blocks
fields will be undefined
,\ninstead of zero. 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 previousStat
reported in the second callback event (the file's\nreappearance) will be the same as the previousStat
of the first callback\nevent (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, string[, position[, encoding]], callback)", "type": "method", "name": "write", "meta": { "added": [ "v0.11.5" ], "changes": [ { "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": "v7.2.0", "pr-url": "https://github.com/nodejs/node/pull/7856", "description": "The `position` parameter is optional now." }, { "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": "`string` {string}", "name": "string", "type": "string" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer", "optional": true }, { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`", "optional": true }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`written` {integer}", "name": "written", "type": "integer" }, { "textRaw": "`string` {string}", "name": "string", "type": "string" } ] } ] } ], "desc": "Write string
to the file specified by fd
. If string
is not a string, then\nthe value will be coerced to one.
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.
Asynchronously writes data to a file, replacing the file if it already exists.\ndata
can be a string or a buffer.
The encoding
option is ignored if data
is a buffer.
const data = new Uint8Array(Buffer.from('Hello Node.js'));\nfs.writeFile('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:
fs.writeFile('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.
file
, it will not be closed\nautomatically.'Hello World'
and the newly written content is 'Aloha'
,\nthen the contents of the file would be 'Aloha World'
, rather than just\n'Aloha'
.Returns undefined
.
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, string...)
.
Returns an object containing commonly used constants for file system\noperations. The specific constants currently defined are described in\nFS Constants.
" } ], "type": "module", "displayName": "fs" }, { "textRaw": "HTTP", "name": "http", "introduced_in": "v0.10.0", "stability": 2, "stabilityText": "Stable", "desc": "To use the HTTP server and client one must require('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 — the\nuser is able to stream data.
\nHTTP message headers are represented by an object like this:
\n\n{ 'content-length': '123',\n 'content-type': 'text/plain',\n 'connection': 'keep-alive',\n 'host': 'mysite.com',\n 'accept': '*/*' }\n
\nKeys are lowercased. Values are not modified.
\nIn order to support the full spectrum of possible HTTP applications, Node.js's\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', 'mysite.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: {net.Socket}",
"name": "return",
"type": "net.Socket"
},
"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",
"optional": true
}
]
}
],
"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
.
callback
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.
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.
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 will no longer be used. Otherwise,\nsockets may hang 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.
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()
.
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": [] }, "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. **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." }, { "textRaw": "`keepAliveMsecs` {number} When using the `keepAlive` option, specifies the [initial delay](net.html#net_socket_setkeepalive_enable_initialdelay) 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](net.html#net_socket_setkeepalive_enable_initialdelay) 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. **Default:** `Infinity`.", "name": "maxSockets", "type": "number", "default": "`Infinity`", "desc": "Maximum number of sockets to allow per host." }, { "textRaw": "`maxFreeSockets` {number} Maximum number of sockets 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 to leave open in a free state. Only relevant if `keepAlive` is set to `true`." }, { "textRaw": "`timeout` {number} Socket timeout in milliseconds. This will set the timeout after the socket is connected.", "name": "timeout", "type": "number", "desc": "Socket timeout in milliseconds. This will set the timeout after the socket is connected." } ], "optional": true } ], "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.
const http = require('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.
Node.js does not check whether Content-Length and the length of the\nbody which has been transmitted are equal or not.
\nThe request inherits from Stream, and additionally implements the\nfollowing:
", "events": [ { "textRaw": "Event: 'abort'", "type": "event", "name": "abort", "meta": { "added": [ "v1.4.1" ], "changes": [] }, "params": [], "desc": "Emitted when the request has been aborted by the client. This event is only\nemitted on the first call to abort()
.
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.
A client and server pair demonstrating how to listen for the 'connect'
event:
const http = require('http');\nconst net = require('net');\nconst url = require('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, cltSocket, head) => {\n // connect to an origin server\n const srvUrl = url.parse(`http://${req.url}`);\n const srvSocket = net.connect(srvUrl.port, srvUrl.hostname, () => {\n cltSocket.write('HTTP/1.1 200 Connection Established\\r\\n' +\n 'Proxy-agent: Node.js-Proxy\\r\\n' +\n '\\r\\n');\n srvSocket.write(head);\n srvSocket.pipe(cltSocket);\n cltSocket.pipe(srvSocket);\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: 'information'", "type": "event", "name": "information", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "params": [], "desc": "Emitted when the server sends a 1xx response (excluding 101 Upgrade). This\nevent is emitted with a callback containing an object with a status code.
\nconst http = require('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', (res) => {\n console.log(`Got information prior to main response: ${res.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` {net.Socket}", "name": "socket", "type": "net.Socket" } ], "desc": "Emitted after a socket is assigned to this request.
" }, { "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 aborted 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.
\nA client server pair demonstrating how to listen for the 'upgrade'
event.
const http = require('http');\n\n// Create an HTTP server\nconst srv = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nsrv.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\nsrv.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"
],
"changes": []
},
"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.end([data[, encoding]][, callback])", "type": "method", "name": "end", "meta": { "added": [ "v0.1.90" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/18780", "description": "This method now returns a reference to `ClientRequest`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {this}", "name": "return", "type": "this" }, "params": [ { "textRaw": "`data` {string|Buffer}", "name": "data", "type": "string|Buffer", "optional": true }, { "textRaw": "`encoding` {string}", "name": "encoding", "type": "string", "optional": true }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "optional": true } ] } ], "desc": "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.
Flush 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. Note that 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.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
"
},
{
"textRaw": "request.setNoDelay([noDelay])",
"type": "method",
"name": "setNoDelay",
"meta": {
"added": [
"v0.5.9"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`noDelay` {boolean}",
"name": "noDelay",
"type": "boolean",
"optional": true
}
]
}
],
"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.
Sends a chunk of the body. By calling this method\nmany times, a request body can be sent to a\nserver — in that case it is suggested to use the\n['Transfer-Encoding', 'chunked']
header line when\ncreating 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": "`socket` {net.Socket}", "type": "net.Socket", "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. The socket
\nmay also be accessed via request.connection
.
const http = require('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
"
}
]
},
{
"textRaw": "Class: http.Server",
"type": "class",
"name": "http.Server",
"meta": {
"added": [
"v0.1.17"
],
"changes": []
},
"desc": "This class inherits from net.Server
and has the following additional\nevents:
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.
Note that 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.
Note that 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.
Default behavior is to close the socket with an HTTP '400 Bad Request' response\nif possible, otherwise the socket is immediately destroyed.
\nsocket
is the net.Socket
object that the error originated from.
const http = require('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.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` {net.Socket} Network socket between the server and client", "name": "socket", "type": "net.Socket", "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.
After 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.connection
.
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. Note that 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": "v10.0.0", "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` {net.Socket} Network socket between the server and client", "name": "socket", "type": "net.Socket", "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.
Stops the server from accepting new connections. See net.Server.close()
.
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's timeout value is 2 minutes, and sockets are\ndestroyed automatically if they time out. However, if a callback is assigned\nto the Server's 'timeout'
event, timeouts must be handled explicitly.
Limit the amount of time the parser will wait to receive the complete HTTP\nheaders.
\nIn case of inactivity, the rules defined in server.timeout
apply. However,\nthat inactivity based timeout would still allow the connection to be kept open\nif the headers are being sent very slowly (by default, up to a byte per 2\nminutes). In order to prevent this, whenever header data arrives an additional\ncheck is made that more than server.headersTimeout
milliseconds has not\npassed since the connection was established. If the check fails, a 'timeout'
\nevent is emitted on the server object, and (by default) the socket is destroyed.\nSee server.timeout
for more information on how timeout behavior can be\ncustomized.
Limits maximum incoming headers count. If set to 0, no limit will be applied.
" }, { "textRaw": "`timeout` {number} Timeout in milliseconds. **Default:** `120000` (2 minutes).", "type": "number", "name": "timeout", "meta": { "added": [ "v0.9.12" ], "changes": [] }, "default": "`120000` (2 minutes)", "desc": "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.
The response inherits from Stream, and additionally implements the\nfollowing:
", "events": [ { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v0.6.7" ], "changes": [] }, "params": [], "desc": "Indicates that the underlying connection was terminated.
" }, { "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.
\nNote that HTTP 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.
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's already been queued but not sent to the client.\nNote that the 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. Note that 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": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string"
},
{
"textRaw": "`value` {any}",
"name": "value",
"type": "any"
}
]
}
],
"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. 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.
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.
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.
\nNote that in the 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.\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 a HTTP/1.1 100 Continue message to the client, indicating that\nthe request body should be sent. See the 'checkContinue'
event on\nServer
.
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.
const body = 'hello world';\nresponse.writeHead(200, {\n 'Content-Length': Buffer.byteLength(body),\n 'Content-Type': 'text/plain' });\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
\nNote that Content-Length is given in bytes not characters. The above example\nworks because the string 'hello world'
contains only single byte characters.\nIf the body contains higher coded characters then Buffer.byteLength()
\nshould be used to determine the number of bytes in a given encoding.\nAnd Node.js does not check whether Content-Length and the length of the body\nwhich has been transmitted are equal or not.
Attempting to set a header field name or value that contains invalid characters\nwill result in a TypeError
being thrown.
Sends a HTTP/1.1 102 Processing message to the client, indicating that\nthe request body should be sent.
" } ], "properties": [ { "textRaw": "`connection` {net.Socket}", "type": "net.Socket", "name": "connection", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "desc": "See response.socket
.
Boolean value that indicates whether the response has completed. Starts\nas false
. After response.end()
executes, the value will be true
.
Boolean (read-only). True if headers were sent, false otherwise.
" }, { "textRaw": "`sendDate` {boolean}", "type": "boolean", "name": "sendDate", "meta": { "added": [ "v0.7.5" ], "changes": [] }, "desc": "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}", "type": "net.Socket", "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. The socket
may also be accessed\nvia response.connection
.
const http = require('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
"
},
{
"textRaw": "`statusCode` {number}",
"type": "number",
"name": "statusCode",
"meta": {
"added": [
"v0.4.0"
],
"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": [ "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": "Class: http.IncomingMessage", "type": "class", "name": "http.IncomingMessage", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "desc": "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.
It implements the Readable Stream interface, as well as the\nfollowing additional events, methods, and properties.
", "events": [ { "textRaw": "Event: 'aborted'", "type": "event", "name": "aborted", "meta": { "added": [ "v0.3.8" ], "changes": [] }, "params": [], "desc": "Emitted when the request has been aborted.
" }, { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v0.4.2" ], "changes": [] }, "params": [], "desc": "Indicates that the underlying connection was closed.
" } ], "properties": [ { "textRaw": "`aborted` {boolean}", "type": "boolean", "name": "aborted", "meta": { "added": [ "v10.1.0" ], "changes": [] }, "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": "`headers` {Object}",
"type": "Object",
"name": "headers",
"meta": {
"added": [
"v0.1.5"
],
"changes": []
},
"desc": "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
, or user-agent
are discarded.set-cookie
is always an array. Duplicates are added to the array.cookie
headers, the values are joined together with '; '.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.
\nNote that the 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.
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.
Only valid for request obtained from http.Server
.
Request URL string. This contains only the URL that is\npresent in the actual HTTP request. If the request is:
\nGET /status?name=ryan HTTP/1.1\\r\\n\nAccept: text/plain\\r\\n\n\\r\\n\n
\nThen request.url
will be:
'/status?name=ryan'\n
\nTo parse the url into its parts require('url').parse(request.url)
\ncan be used:
$ node\n> require('url').parse('/status?name=ryan')\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: 'name=ryan',\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\n
\nTo extract the parameters from the query string, the\nrequire('querystring').parse
function can be used, or\ntrue
can be passed as the second argument to require('url').parse
:
$ node\n> require('url').parse('/status?name=ryan', true)\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: { name: 'ryan' },\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\n
"
}
],
"methods": [
{
"textRaw": "message.destroy([error])",
"type": "method",
"name": "destroy",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`error` {Error}",
"name": "error",
"type": "Error",
"optional": true
}
]
}
],
"desc": "Calls destroy()
on the socket that received the IncomingMessage
. If error
\nis provided, an 'error'
event is emitted and error
is passed as an argument\nto any listeners on the event.
Calls message.connection.setTimeout(msecs, callback)
.
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.
Returns a new instance of http.Server
.
The requestListener
is a function which is automatically\nadded to the 'request'
event.
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 and calls req.end()
\nautomatically. Note that 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://nodejs.org/dist/index.json', (res) => {\n const { statusCode } = res;\n const contentType = res.headers['content-type'];\n\n let error;\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
"
},
{
"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` always set to `GET`. Properties that are inherited from the prototype are ignored.",
"name": "options",
"type": "Object",
"desc": "Accepts the same `options` as [`http.request()`][], with the `method` always set to `GET`. Properties that are inherited from the prototype are ignored.",
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"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 and calls req.end()
\nautomatically. Note that 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://nodejs.org/dist/index.json', (res) => {\n const { statusCode } = res;\n const contentType = res.headers['content-type'];\n\n let error;\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
"
},
{
"textRaw": "http.request(options[, callback])",
"type": "method",
"name": "request",
"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": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`protocol` {string} Protocol to use. **Default:** `'http:'`.",
"name": "protocol",
"type": "string",
"default": "`'http:'`",
"desc": "Protocol to use."
},
{
"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": "`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": "`port` {number} Port of remote server. **Default:** `80`.",
"name": "port",
"type": "number",
"default": "`80`",
"desc": "Port of remote server."
},
{
"textRaw": "`localAddress` {string} Local interface to bind for network connections.",
"name": "localAddress",
"type": "string",
"desc": "Local interface to bind for network connections."
},
{
"textRaw": "`socketPath` {string} Unix Domain Socket (cannot be used if one of `host` or `port` is specified, those specify a TCP Socket).",
"name": "socketPath",
"type": "string",
"desc": "Unix Domain Socket (cannot be used if one of `host` or `port` is specified, those specify a TCP Socket)."
},
{
"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": "`headers` {Object} An object containing request headers.",
"name": "headers",
"type": "Object",
"desc": "An object containing request headers."
},
{
"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."
},
{
"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": "`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": "`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": "`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": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"desc": "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.
const postData = querystring.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/x-www-form-urlencoded',\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
\nNote that in 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 RFC2616 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'
'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'
If req.abort()
is called before the connection succeeds, the following events\nwill 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 events\nwill be emitted in the following order:
'socket'
'response'
'data'
any number of times, on the res
objectreq.abort()
called here)'abort'
'aborted'
on the res
object'close'
'end'
on the res
object'close'
on the res
objectNote that setting the timeout
option or using the setTimeout()
function will\nnot abort the request or do anything besides add a 'timeout'
event.
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.
const postData = querystring.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/x-www-form-urlencoded',\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
\nNote that in 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 RFC2616 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'
'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'
If req.abort()
is called before the connection succeeds, the following events\nwill 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 events\nwill be emitted in the following order:
'socket'
'response'
'data'
any number of times, on the res
objectreq.abort()
called here)'abort'
'aborted'
on the res
object'close'
'end'
on the res
object'close'
on the res
objectNote that setting the timeout
option or using the setTimeout()
function will\nnot abort the request or do anything besides add a 'timeout'
event.
The http2
module provides an implementation of the HTTP/2 protocol. It\ncan be accessed using:
const http2 = require('http2');\n
",
"modules": [
{
"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('http2');\nconst fs = require('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',\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('http2');\nconst fs = require('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
,\nif-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('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream, headers) => {\n console.log(headers[':path']);\n console.log(headers.ABC);\n});\n
",
"type": "module",
"displayName": "Headers Object"
},
{
"textRaw": "Settings Object",
"name": "settings_object",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"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: 4,096 octets
.enablePush
<boolean> Specifies true
if HTTP/2 Push Streams are to be\npermitted on the Http2Session
instances.initialWindowSize
<number> Specifies the senders initial window size\nfor stream-level flow control. The minimum allowed value is 0. The maximum\nallowed value is 232-1. Default: 65,535 bytes
.maxFrameSize
<number> Specifies the size of the largest frame payload.\nThe minimum allowed value is 16,384. The maximum allowed value\nis 224-1. Default: 16,384 bytes
.maxConcurrentStreams
<number> Specifies the maximum number of concurrent\nstreams permitted on an Http2Session
. There is no default value which\nimplies, at least theoretically, 231-1 streams may be open\nconcurrently at any given time in an Http2Session
. The minimum value\nis 0. The maximum allowed value is 231-1.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
.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.All additional properties on the settings object are ignored.
", "type": "module", "displayName": "Settings Object" }, { "textRaw": "Using `options.selectPadding()`", "name": "using_`options.selectpadding()`", "desc": "When options.paddingStrategy
is equal to\nhttp2.constants.PADDING_STRATEGY_CALLBACK
, the HTTP/2 implementation will\nconsult the options.selectPadding()
callback function, if provided, to\ndetermine the specific amount of padding to use per HEADERS
and DATA
frame.
The options.selectPadding()
function receives two numeric arguments,\nframeLen
and maxFrameLen
and must return a number N
such that\nframeLen <= N <= maxFrameLen
.
const http2 = require('http2');\nconst server = http2.createServer({\n paddingStrategy: http2.constants.PADDING_STRATEGY_CALLBACK,\n selectPadding(frameLen, maxFrameLen) {\n return maxFrameLen;\n }\n});\n
\nThe options.selectPadding()
function is invoked once for every HEADERS
and\nDATA
frame. This has a definite noticeable impact on performance.
There are several types of error conditions that may arise when using the\nhttp2
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('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('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 ${name}`));\n});\n\nserver.listen(8000);\n
\nAn HTTP/2 CONNECT proxy:
\nconst http2 = require('http2');\nconst { NGHTTP2_REFUSED_STREAM } = http2.constants;\nconst net = require('net');\n\nconst proxy = http2.createServer();\nproxy.on('stream', (stream, headers) => {\n if (headers[':method'] !== 'CONNECT') {\n // Only accept CONNECT requests\n stream.close(NGHTTP2_REFUSED_STREAM);\n return;\n }\n const auth = new URL(`tcp://${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('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:${port}`\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('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('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 '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('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'\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('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',\n ':status': 200\n });\n stream.on('error', (error) => console.error(error));\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(80);\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.
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 or not the Http2Session
is currently waiting for an\nacknowledgment for a 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
.
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('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('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('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": [] }, "events": [ { "textRaw": "Event: 'altsvc'", "type": "event", "name": "altsvc", "meta": { "added": [ "v9.4.0" ], "changes": [] }, "params": [ { "textRaw": "`alt` {string}", "name": "alt", "type": "string" }, { "textRaw": "`origin` {string}", "name": "origin", "type": "string" }, { "textRaw": "`streamId` {number}", "name": "streamId", "type": "number" } ], "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('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('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.
This method is only available if http2session.type
is equal to\nhttp2.constants.NGHTTP2_SESSION_CLIENT
.
const http2 = require('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
.
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.
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.http2stream.close()
method is called.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 will be sent 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.
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 'timeout'
event is emitted after no activity is received for this\nHttp2Stream
within the number of milliseconds set using\nhttp2stream.setTimeout()
.
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.
Note that 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 the 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.
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> true
if this Http2Stream
has been closed locally.remoteClose
<number> true
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('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('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": [],
"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": [],
"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('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('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('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 });\n stream.end('some data');\n});\n
\nWhen 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('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": "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} A readable file descriptor.",
"name": "fd",
"type": "number",
"desc": "A readable file descriptor."
},
{
"textRaw": "`headers` {HTTP/2 Headers Object}",
"name": "headers",
"type": "HTTP/2 Headers Object",
"optional": true
},
{
"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."
}
],
"optional": true
}
]
}
],
"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('http2');\nconst fs = require('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'\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 is not closed when the stream is closed, so it will need\nto be closed manually once it is no longer needed.\nNote that using 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.
\nWhen 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('http2');\nconst fs = require('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'\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": "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",
"optional": true
},
{
"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."
}
],
"optional": true
}
]
}
],
"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('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 if (err.code === 'ENOENT') {\n stream.respond({ ':status': 404 });\n } else {\n stream.respond({ ':status': 500 });\n }\n stream.end();\n }\n\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain' },\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('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' },\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.sendTrilers()
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('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain' },\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 http2
\nmodule.
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.
Note that when this event is emitted and handled, the 'request'
event will\nnot be emitted.
Emitted each time there is a request. Note that 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": [], "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.
const http2 = require('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'\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 http2server.setTimeout()
.\nDefault: 2 minutes.
Stops the server from accepting new connections. See net.Server.close()
.
Note that this is not analogous to restricting new requests since HTTP/2\nconnections are persistent. To achieve a similar graceful shutdown behavior,\nconsider also using http2session.close()
on active sessions.
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 of no callback function were assigned, a new ERR_INVALID_CALLBACK
\nerror will be thrown.
Instances of Http2SecureServer
are created using the\nhttp2.createSecureServer()
function. The Http2SecureServer
class is not\nexported directly by the 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.
Note that when this event is emitted and handled, the 'request'
event will\nnot be emitted.
Emitted each time there is a request. Note that 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": [], "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.
const http2 = require('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'\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. See the Compatibility API.
Stops the server from accepting new connections. See tls.Server.close()
.
Note that this is not analogous to restricting new requests since HTTP/2\nconnections are persistent. To achieve a similar graceful shutdown behavior,\nconsider also using http2session.close()
on active sessions.
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 of no callback function were assigned, a new ERR_INVALID_CALLBACK
\nerror will be thrown.
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('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',\n ':status': 200\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(80);\n
"
},
{
"textRaw": "http2.createSecureServer(options[, onRequestHandler])",
"type": "method",
"name": "createSecureServer",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"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."
},
{
"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: {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": "`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. The minimum value is `4`. **Default:** `128`.",
"name": "maxHeaderListPairs",
"type": "number",
"default": "`128`",
"desc": "Sets the maximum number of header entries. 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} Identifies 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": "Identifies the strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames.",
"options": [
{
"textRaw": "`http2.constants.PADDING_STRATEGY_NONE` - Specifies that no padding is to be applied.",
"name": "http2.constants.PADDING_STRATEGY_NONE",
"desc": "Specifies that no padding is to be applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_MAX` - Specifies that the maximum amount of padding, as determined by the internal implementation, is to be applied.",
"name": "http2.constants.PADDING_STRATEGY_MAX",
"desc": "Specifies that the maximum amount of padding, as determined by the internal implementation, is to be applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_CALLBACK` - Specifies that the user provided `options.selectPadding()` callback is to be used to determine the amount of padding.",
"name": "http2.constants.PADDING_STRATEGY_CALLBACK",
"desc": "Specifies that the user provided `options.selectPadding()` callback is to be used to determine the amount of padding."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_ALIGNED` - Will *attempt* to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, however, 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 will be used and the total frame length will *not* necessarily be aligned at 8 bytes.",
"name": "http2.constants.PADDING_STRATEGY_ALIGNED",
"desc": "Will *attempt* to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, however, 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 will be used and the total frame length will *not* necessarily be 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": "`selectPadding` {Function} When `options.paddingStrategy` is equal to `http2.constants.PADDING_STRATEGY_CALLBACK`, provides the callback function used to determine the padding. See [Using `options.selectPadding()`][].",
"name": "selectPadding",
"type": "Function",
"desc": "When `options.paddingStrategy` is equal to `http2.constants.PADDING_STRATEGY_CALLBACK`, provides the callback function used to determine the padding. See [Using `options.selectPadding()`][]."
},
{
"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": "...: 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": "`onRequestHandler` {Function} See [Compatibility API][]",
"name": "onRequestHandler",
"type": "Function",
"desc": "See [Compatibility API][]",
"optional": true
}
]
}
],
"desc": "Returns a tls.Server
instance that creates and manages Http2Session
\ninstances.
const http2 = require('http2');\nconst fs = require('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',\n ':status': 200\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(80);\n
"
},
{
"textRaw": "http2.connect(authority[, options][, listener])",
"type": "method",
"name": "connect",
"meta": {
"added": [
"v8.4.0"
],
"changes": [
{
"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}",
"name": "authority",
"type": "string|URL"
},
{
"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": "`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. The minimum value is `1`. **Default:** `128`.",
"name": "maxHeaderListPairs",
"type": "number",
"default": "`128`",
"desc": "Sets the maximum number of header entries. 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.",
"name": "maxReservedRemoteStreams",
"type": "number",
"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."
},
{
"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} Identifies 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": "Identifies the strategy used for determining the amount of padding to use for `HEADERS` and `DATA` frames.",
"options": [
{
"textRaw": "`http2.constants.PADDING_STRATEGY_NONE` - Specifies that no padding is to be applied.",
"name": "http2.constants.PADDING_STRATEGY_NONE",
"desc": "Specifies that no padding is to be applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_MAX` - Specifies that the maximum amount of padding, as determined by the internal implementation, is to be applied.",
"name": "http2.constants.PADDING_STRATEGY_MAX",
"desc": "Specifies that the maximum amount of padding, as determined by the internal implementation, is to be applied."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_CALLBACK` - Specifies that the user provided `options.selectPadding()` callback is to be used to determine the amount of padding.",
"name": "http2.constants.PADDING_STRATEGY_CALLBACK",
"desc": "Specifies that the user provided `options.selectPadding()` callback is to be used to determine the amount of padding."
},
{
"textRaw": "`http2.constants.PADDING_STRATEGY_ALIGNED` - Will *attempt* to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, however, 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 will be used and the total frame length will *not* necessarily be aligned at 8 bytes.",
"name": "http2.constants.PADDING_STRATEGY_ALIGNED",
"desc": "Will *attempt* to apply enough padding to ensure that the total frame length, including the 9-byte header, is a multiple of 8. For each frame, however, 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 will be used and the total frame length will *not* necessarily be 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": "`selectPadding` {Function} When `options.paddingStrategy` is equal to `http2.constants.PADDING_STRATEGY_CALLBACK`, provides the callback function used to determine the padding. See [Using `options.selectPadding()`][].",
"name": "selectPadding",
"type": "Function",
"desc": "When `options.paddingStrategy` is equal to `http2.constants.PADDING_STRATEGY_CALLBACK`, provides the callback function used to determine the padding. See [Using `options.selectPadding()`][]."
},
{
"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": "`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."
}
],
"optional": true
},
{
"textRaw": "`listener` {Function}",
"name": "listener",
"type": "Function",
"optional": true
}
]
}
],
"desc": "Returns a ClientHttp2Session
instance.
const http2 = require('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('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|Uint8Array} The packed settings.",
"name": "buf",
"type": "Buffer|Uint8Array",
"desc": "The packed settings."
}
]
}
],
"desc": "Returns a HTTP/2 Settings Object containing the deserialized settings from\nthe given Buffer
as generated by http2.getPackedSettings()
.
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()
.
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('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' });\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('http2');\nconst { readFileSync } = require('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.
It implements the Readable Stream interface, as well as the\nfollowing additional events, methods, and properties.
", "events": [ { "textRaw": "Event: 'aborted'", "type": "event", "name": "aborted", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "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. It can also be accessed via\nreq.headers[':authority']
.
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, hostname, 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.
\nNote that the 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\npresent in the actual HTTP request. If the request is:
\nGET /status?name=ryan HTTP/1.1\\r\\n\nAccept: text/plain\\r\\n\n\\r\\n\n
\nThen request.url
will be:
'/status?name=ryan'\n
\nTo parse the url into its parts require('url').parse(request.url)
\ncan be used:
$ node\n> require('url').parse('/status?name=ryan')\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: 'name=ryan',\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\n
\nTo extract the parameters from the query string, the\nrequire('querystring').parse
function can be used, or\ntrue
can be passed as the second argument to require('url').parse
.
$ node\n> require('url').parse('/status?name=ryan', true)\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: { name: 'ryan' },\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\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",
"optional": true
}
]
}
],
"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.
The response inherits from Stream, and additionally implements the\nfollowing:
", "events": [ { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "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.
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.\nNote that the 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. Note that 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');\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');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\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",
"optional": true
}
]
}
],
"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.
\nNote that in the 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 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.
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' });\n
\nNote that Content-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');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\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.
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
.
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": "`sendDate` {boolean}", "type": "boolean", "name": "sendDate", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "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('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 (RFC7540 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.
The Performance Observer API can be used to collect basic performance\nmetrics for each Http2Session
and Http2Stream
instance.
const { PerformanceObserver } = require('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
.HTTPS is the HTTP protocol over TLS/SSL. In Node.js this is implemented as a\nseparate module.
", "classes": [ { "textRaw": "Class: https.Agent", "type": "class", "name": "https.Agent", "meta": { "added": [ "v0.4.5" ], "changes": [] }, "desc": "An Agent
object for HTTPS similar to http.Agent
. See\nhttps.request()
for more information.
This class is a subclass of tls.Server
and emits events same as\nhttp.Server
. See http.Server
for more information.
See server.close()
from the HTTP module for details.
Starts the HTTPS server listening for encrypted connections.\nThis method is identical to server.listen()
from net.Server
.
See http.Server#headersTimeout
.
See http.Server#maxHeadersCount
.
See http.Server#timeout
.
See http.Server#keepAliveTimeout
.
// curl -k https://localhost:8000/\nconst https = require('https');\nconst fs = require('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('https');\nconst fs = require('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": "`options` {Object | string | URL} Accepts the same `options` as [`https.request()`][], with the `method` always set to `GET`.",
"name": "options",
"type": "Object | string | URL",
"desc": "Accepts the same `options` as [`https.request()`][], with the `method` always set to `GET`."
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"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('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` always set to `GET`.",
"name": "options",
"type": "Object | string | URL",
"desc": "Accepts the same `options` as [`https.request()`][], with the `method` always set to `GET`.",
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"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('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": "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": [
{
"params": [
{
"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",
"optional": true
}
]
}
],
"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
.
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('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('tls');\nconst https = require('https');\nconst crypto = require('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-sha25 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 then 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": "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": [
{
"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`"
}
],
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"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
.
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('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('tls');\nconst https = require('https');\nconst crypto = require('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-sha25 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 then 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": []
},
"desc": "Global instance of https.Agent
for all HTTPS client requests.
The inspector
module provides an API for interacting with the V8 inspector.
It can be accessed using:
\nconst inspector = require('inspector');\n
",
"methods": [
{
"textRaw": "inspector.close()",
"type": "method",
"name": "close",
"signatures": [
{
"params": []
}
],
"desc": "Deactivate the inspector. Blocks until there are no active connections.
" }, { "textRaw": "inspector.open([port[, host[, wait]]])", "type": "method", "name": "open", "signatures": [ { "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.", "optional": true }, { "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.", "optional": true }, { "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.", "optional": true } ] } ], "desc": "Activate inspector on host and port. Equivalent to node --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.
require('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." } ], "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
\nIt 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
"
}
],
"methods": [
{
"textRaw": "session.connect()",
"type": "method",
"name": "connect",
"meta": {
"added": [
"v8.0.0"
],
"changes": []
},
"signatures": [
{
"params": []
}
],
"desc": "Connects a session to the inspector back-end. An exception will be thrown\nif there is already a connected session established either through the API or by\na front-end connected to the Inspector WebSocket port.
" }, { "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.
\nApart from the debugger, various V8 Profilers are available through the DevTools\nprotocol. Here's a simple example showing how to use the CPU profiler:
\nconst inspector = require('inspector');\nconst fs = require('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"
}
],
"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.
inspector.Session
is an EventEmitter
with the following events:
In the Node.js module system, 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 module system is implemented in the require('module')
module.
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')
.
Because module
provides a filename
property (normally equivalent to\n__filename
), the entry point of the current application can be obtained\nby checking require.main.filename
.
The semantics of Node.js's require()
function were designed to be general\nenough to support a number of reasonable directory structures. Package manager\nprograms such as dpkg
, rpm
, and npm
will hopefully find it possible to\nbuild native 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.
Since Node.js looks up the realpath
of any modules it loads (that is,\nresolves symlinks), and then looks for their dependencies in the node_modules
\nfolders as described here, this\nsituation is very simple to resolve 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
\ndepends on./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\nthat bar
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.resolve()
does:
require(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 filesystem root\n3. If X begins with './' or '/' or '../'\n a. LOAD_AS_FILE(Y + X)\n b. LOAD_AS_DIRECTORY(Y + X)\n4. LOAD_NODE_MODULES(X, dirname(Y))\n5. THROW \"not found\"\n\nLOAD_AS_FILE(X)\n1. If X is a file, load X as JavaScript text. 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. let M = X + (json main field)\n c. LOAD_AS_FILE(M)\n d. LOAD_INDEX(M)\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_AS_FILE(DIR/X)\n b. 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 = [GLOBAL_FOLDERS]\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 = DIRS + DIR\n d. let I = I - 1\n5. return DIRS\n
"
},
{
"textRaw": "Caching",
"name": "Caching",
"type": "misc",
"desc": "Modules are cached after the first time they are loaded. This means\n(among other things) that every call to require('foo')
will get\nexactly the same object returned, if it would resolve to the same file.
Provided require.cache
is not modified, multiple calls to\nrequire('foo')
will not cause the module code to be executed multiple times.\nThis is an important feature. With it, \"partially done\" objects can be returned,\nthus allowing transitive dependencies to be loaded even when they would cause\ncycles.
To have a module execute code multiple times, export a function, and call\nthat function.
", "miscs": [ { "textRaw": "Module Caching Caveats", "name": "Module Caching Caveats", "type": "misc", "desc": "Modules are cached based on their resolved filename. Since modules may\nresolve to a different filename based on the location of the calling\nmodule (loading from node_modules
folders), it is not a guarantee\nthat require('foo')
will always return the exact same object, if it\nwould 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 Node.js's source and are located in the\nlib/
folder.
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.
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
.
.js
files are interpreted as JavaScript text files, and .json
files are\nparsed as JSON text files. .node
files are interpreted as compiled addon\nmodules loaded with dlopen
.
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 an Error
with its\ncode
property set to 'MODULE_NOT_FOUND'
.
It is convenient to organize programs and libraries into self-contained\ndirectories, and then provide a single entry point to that library.\nThere 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
.
This is the extent of Node.js's awareness of package.json
files.
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 above\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
"
},
{
"textRaw": "Loading from `node_modules` Folders",
"name": "Loading from `node_modules` Folders",
"type": "misc",
"desc": "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 parent 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 frozen.
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 Node.js's\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.It helps to provide some global-looking variables that are actually specific\nto the module, such as:
\nmodule
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.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.
// Importing a local module:\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('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. Note that\nthis does not apply to native addons, for which reloading will result in an\nerror.
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\nnon-JavaScript modules into Node.js by compiling them on-demand.\nHowever, in practice, there are much better ways to do this, such as\nloading modules via some other Node.js program, or compiling them to\nJavaScript ahead of time.
\nSince the module system is locked, this feature will probably never go\naway. However, it may have subtle bugs and complexities that are best\nleft untouched.
\nNote that the number of file system operations that the module system\nhas to perform in order to resolve a require(...)
statement to a\nfilename scales linearly with the number of registered extensions.
In other words, adding extensions slows down the module loader and\nshould be discouraged.
" }, { "textRaw": "`main` {Object}", "type": "Object", "name": "main", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "desc": "The Module
object representing the entry script loaded when the Node.js\nprocess launched.\nSee \"Accessing the main module\".
In entry.js
script:
console.log(require.main);\n
\nnode entry.js\n
\n\nModule {\n id: '.',\n exports: {},\n parent: null,\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][] like `$HOME/.node_modules`, which are always included. Note that 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][] like `$HOME/.node_modules`, which are always included. Note that 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."
}
],
"optional": true
}
]
}
],
"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.
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
.
Provides general utility methods when interacting with instances of\nModule
— the module
variable often seen in file modules. Accessed\nvia require('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.
\nNote that module
in this context isn't the same object that's provided\nby the module wrapper. To access it, require the Module
module:
const builtin = require('module').builtinModules;\n
"
}
],
"methods": [
{
"textRaw": "module.createRequireFromPath(filename)",
"type": "method",
"name": "createRequireFromPath",
"meta": {
"added": [
"v10.12.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {[`require`][]} Require function",
"name": "return",
"type": "[`require`][]",
"desc": "Require function"
},
"params": [
{
"textRaw": "`filename` {string} Filename to be used to construct the relative require function.",
"name": "filename",
"type": "string",
"desc": "Filename to be used to construct the relative require function."
}
]
}
],
"desc": "const { createRequireFromPath } = require('module');\nconst requireUtil = createRequireFromPath('../src/utils');\n\n// require `../src/utils/some-tool`\nrequireUtil('./some-tool');\n
"
}
],
"type": "module",
"displayName": "The `Module` Object"
}
],
"vars": [
{
"textRaw": "The `module` Object",
"name": "module",
"meta": {
"added": [
"v0.1.16"
],
"changes": []
},
"type": "var",
"desc": "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
. Note that 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('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
\nNote that assignment 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 to 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": "`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}", "type": "module", "name": "parent", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "The module that first required this one.
" }, { "textRaw": "`paths` {string[]}", "type": "string[]", "name": "paths", "meta": { "added": [ "v0.4.0" ], "changes": [] }, "desc": "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: {Object} `module.exports` from the resolved module", "name": "return", "type": "Object", "desc": "`module.exports` from the resolved module" }, "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.
\n\nStability: 2 - Stable
\n
The 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('net');\n
",
"modules": [
{
"textRaw": "IPC Support",
"name": "ipc_support",
"desc": "The 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\nfilesystem pathname. It gets truncated to sizeof(sockaddr_un.sun_path) - 1
,\nwhich varies on different operating system between 91 and 107 bytes.\nThe typical values are 107 on Linux and 103 on macOS. The path is\nsubject to the same naming conventions and permissions checks as would be done\non file creation. If the UNIX domain socket (that is visible as a file system\npath) is created and used in conjunction with one of Node.js' API abstractions\nsuch as net.createServer()
, it will be unlinked as part of\nserver.close()
. On the other hand, if it is created and used outside of\nthese abstractions, the user will need to manually remove it. The same applies\nwhen the path was created by a Node.js API but the program crashes abruptly.\nIn short, a UNIX domain socket once successfully created will be visible in the\nfilesystem, and will persist until unlinked.
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.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. Note that 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()
.
Returns 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
\nDon't call server.address()
until the 'listening'
event has been emitted.
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.
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 servers\nThis 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.log('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",
"optional": true
},
{
"textRaw": "`callback` {Function} Common parameter of [`server.listen()`][] functions",
"name": "callback",
"type": "Function",
"desc": "Common parameter of [`server.listen()`][] functions",
"optional": true
}
]
}
],
"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": "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": "`callback` {Function} Common parameter of [`server.listen()`][] functions.", "name": "callback", "type": "Function", "desc": "Common parameter of [`server.listen()`][] functions.", "optional": true } ] } ], "desc": "If port
is specified, it behaves the same as\n\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
\nStarting 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.
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.
The number of concurrent connections on the server.
\nThis becomes null
when sending a socket to a child with\nchild_process.fork()
. To poll forks and get current number of active\nconnections, use asynchronous server.getConnections()
instead.
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). A\nnet.Socket
is also a duplex stream, so it can be both readable and\nwritable, and it is also an 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 data is received. The argument data
will be a Buffer
or\nString
. Encoding of data is set by socket.setEncoding()
.
Note that 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 sends a FIN packet, thus ending the\nreadable side of the socket.
\nBy default (allowHalfOpen
is false
) the socket will send a FIN packet\nback and destroy its file descriptor once it has written out its pending\nwrite queue. However, if allowHalfOpen
is set to true
, the socket will\nnot automatically end()
its writable side, allowing the\nuser 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 hostname but before connecting.\nNot applicable to UNIX sockets.
\nerr
<Error> | <null> The error object. See dns.lookup()
.address
<string> The IP address.family
<string> | <null> The address type. See dns.lookup()
.host
<string> The hostname.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.
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, can be either 4
or 6
.\nDefault: 4
.hints
<number> Optional dns.lookup()
hints.lookup
<Function> Custom lookup function. Default: dns.lookup()
.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.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. Only necessary in\ncase of errors (parse error or so).
\nIf exception
is specified, an 'error'
event will be emitted and any\nlisteners for that event will receive exception
as an argument.
Half-closes the socket. i.e., it sends a FIN packet. It is possible the\nserver will still send some data.
\nIf data
is specified, it is equivalent to calling\nsocket.write(data, encoding)
followed by socket.end()
.
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.
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.
Disables the Nagle algorithm. By default TCP connections use the Nagle\nalgorithm, they buffer data before sending it off. Setting true
for\nnoDelay
will immediately fire off data each time socket.write()
is called.
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 - this may not be immediately.
See Writable
stream write()
method for more\ninformation.
net.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. (Internally it is\npolling on the socket's file descriptor for being writable).
The consequence of this internal buffering is that memory may grow. This\nproperty shows the number of characters currently buffered to be written.\n(Number of characters is approximately equal to the number of bytes to be\nwritten, but the buffer may contain strings, and the strings are lazily\nencoded, so the exact number of bytes is not known.)
\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": "socket.bytesWritten", "name": "bytesWritten", "meta": { "added": [ "v0.5.3" ], "changes": [] }, "desc": "The amount of bytes sent.
" }, { "textRaw": "socket.connecting", "name": "connecting", "meta": { "added": [ "v6.1.0" ], "changes": [] }, "desc": "If true
,\nsocket.connect(options[, connectListener])
\nwas called and has not yet finished. Will be set to true
before emitting\n'connect'
event and/or calling\nsocket.connect(options[, connectListener])
's\ncallback.
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
.
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'
.
The numeric representation of the remote port. For example, 80
or 21
.
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('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
the second line would just be\nchanged to:
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)`].",
"optional": true
}
]
}
],
"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\nsends a FIN packet, the server will only send a FIN packet back when\nsocket.end()
is explicitly called, until then the connection is\nhalf-closed (non-readable but still writable). See 'end'
event\nand 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 an TCP echo server which listens for connections\non port 8124:
\nconst net = require('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
the third line from the last would\njust be changed to:
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.isIP(input)",
"type": "method",
"name": "isIP",
"meta": {
"added": [
"v0.3.0"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {integer}",
"name": "return",
"type": "integer"
},
"params": [
{
"textRaw": "`input` {string}",
"name": "input",
"type": "string"
}
]
}
],
"desc": "Tests if input is an IP address. Returns 0
for invalid strings,\nreturns 4
for IP version 4 addresses, and returns 6
for IP version 6\naddresses.
Returns true
if input is a version 4 IP address, otherwise returns false
.
Returns true
if input is a version 6 IP address, otherwise returns false
.
The os
module provides a number of operating system-related utility methods.\nIt can be accessed using:
const os = require('os');\n
",
"properties": [
{
"textRaw": "`EOL` {string}",
"type": "string",
"name": "EOL",
"meta": {
"added": [
"v0.7.8"
],
"changes": []
},
"desc": "A string constant defining the operating system-specific end-of-line marker:
\n\\n
on POSIX\\r\\n
on WindowsReturns an object containing commonly used operating system specific constants\nfor error codes, process signals, and so on. The specific constants currently\ndefined are described in OS Constants.
" } ], "methods": [ { "textRaw": "os.arch()", "type": "method", "name": "arch", "meta": { "added": [ "v0.5.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {string}", "name": "return", "type": "string" }, "params": [] } ], "desc": "The os.arch()
method returns a string identifying the operating system CPU\narchitecture for which the Node.js binary was compiled.
The current possible values are: 'arm'
, 'arm64'
, 'ia32'
, 'mips'
,\n'mipsel'
, 'ppc'
, 'ppc64'
, 's390'
, 's390x'
, 'x32'
, and 'x64'
.
Equivalent to process.arch
.
The os.cpus()
method returns an array of objects containing information about\neach logical CPU core.
The properties included on each object include:
\nmodel
<string>speed
<number> (in MHz)times
<Object>
user
<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 model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 511580,\n nice: 20,\n sys: 40900,\n idle: 1070842510,\n irq: 0\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 291660,\n nice: 0,\n sys: 34360,\n idle: 1070888000,\n irq: 10\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 308260,\n nice: 0,\n sys: 55410,\n idle: 1071129970,\n irq: 880\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 266450,\n nice: 1480,\n sys: 34920,\n idle: 1072572010,\n irq: 30\n }\n }\n]\n
\nBecause nice
values are UNIX-specific, on Windows the nice
values of all\nprocessors are always 0.
The os.endianness()
method returns a string identifying the endianness of the\nCPU for which the Node.js binary was compiled.
Possible values are:
\n'BE'
for big endian'LE'
for little endian.The os.freemem()
method returns the amount of free system memory in bytes as\nan integer.
The os.getPriority()
method returns the scheduling priority for the process\nspecified by pid
. If pid
is not provided, or is 0
, the priority of the\ncurrent process is returned.
The os.homedir()
method returns the home directory of the current user as a\nstring.
The os.hostname()
method returns the hostname of the operating system as a\nstring.
The os.loadavg()
method returns an array containing the 1, 5, and 15 minute\nload averages.
The load average is a measure of system activity, calculated by the operating\nsystem and expressed as a fractional number. As a rule of thumb, the load\naverage should ideally be less than the number of logical CPUs in the system.
\nThe load average is a UNIX-specific concept with no real equivalent on\nWindows platforms. On Windows, the return value is always [0, 0, 0]
.
The os.networkInterfaces()
method returns an object containing only network\ninterfaces that have been assigned a network address.
Each 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 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 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": "The os.platform()
method returns a string identifying the operating system\nplatform as set during compile time of Node.js.
Currently possible values are:
\n'aix'
'darwin'
'freebsd'
'linux'
'openbsd'
'sunos'
'win32'
Equivalent to process.platform
.
The value 'android'
may also be returned if the Node.js is built on the\nAndroid operating system. However, Android support in Node.js is considered\nto be experimental at this time.
The os.release()
method returns a string identifying the operating system\nrelease.
On POSIX systems, the operating system release is determined by calling\nuname(3)
. On Windows, GetVersionExW()
is used. Please see\nhttps://en.wikipedia.org/wiki/Uname#Examples for more information.
The os.setPriority()
method attempts to set the scheduling priority for the\nprocess specified by pid
. If pid
is not provided, or is 0
, the priority\nof 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, it is recommended to set priority
to one of the priority constants.
On Windows setting priority to PRIORITY_HIGHEST
requires elevated user,\notherwise the set priority will be silently reduced to PRIORITY_HIGH
.
The os.tmpdir()
method returns a string specifying the operating system's\ndefault directory for temporary files.
The os.totalmem()
method returns the total amount of system memory in bytes\nas an integer.
The os.type()
method returns a string identifying the operating system name\nas returned by uname(3)
. For example, 'Linux'
on Linux, 'Darwin'
on\nmacOS, and 'Windows_NT'
on Windows.
Please see https://en.wikipedia.org/wiki/Uname#Examples for additional\ninformation about the output of running uname(3)
on various operating\nsystems.
The os.uptime()
method returns the system uptime in number of seconds.
The os.userInfo()
method returns information about the currently effective\nuser — on POSIX platforms, this is typically a subset of the password file. The\nreturned object includes the username
, uid
, gid
, shell
, and homedir
.\nOn Windows, the uid
and gid
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 several\nenvironment variables for the home directory before falling back to the\noperating system response.
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 currently 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. Note that\n while 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 |
The path
module provides utilities for working with file and directory paths.\nIt can be accessed using:
const path = require('path');\n
",
"modules": [
{
"textRaw": "Windows vs. POSIX",
"name": "windows_vs._posix",
"desc": "The default operation of the path
module varies based on the operating system\non which a Node.js application is running. Specifically, when running on a\nWindows operating system, the path
module will assume that Windows-style\npaths 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()
methods returns the last portion of a path
, similar to\nthe Unix basename
command. Trailing directory separators are ignored, see\npath.sep
.
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
\nA TypeError
is thrown if path
is not a string or if ext
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 the\nfirst character of the basename of path
(see path.basename()
) is .
, then\nan 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
\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
\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.
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
.
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 system. 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": []
},
"desc": "The path.posix
property provides access to POSIX specific implementations\nof the path
methods.
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 Performance Timing API provides an implementation of the\nW3C Performance Timeline specification. The purpose of the API\nis to support collection of high resolution performance metrics.\nThis is the same Performance API as implemented in modern Web browsers.
\nconst { PerformanceObserver, performance } = require('perf_hooks');\n\nconst obs = new PerformanceObserver((items) => {\n console.log(items.getEntries()[0].duration);\n performance.clearMarks();\n});\nobs.observe({ entryTypes: ['measure'] });\n\nperformance.mark('A');\ndoSomeLongRunningProcess(() => {\n performance.mark('B');\n performance.measure('A to B', 'A', 'B');\n});\n
",
"classes": [
{
"textRaw": "Class: Performance",
"type": "class",
"name": "Performance",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"methods": [
{
"textRaw": "performance.clearMarks([name])",
"type": "method",
"name": "clearMarks",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`name` {string}",
"name": "name",
"type": "string",
"optional": true
}
]
}
],
"desc": "If name
is not provided, removes all PerformanceMark
objects from the\nPerformance Timeline. If name
is provided, removes only the named mark.
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.
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, then startMark
is set to timeOrigin
by default.
The endMark
argument must identify any existing PerformanceMark
in the\nPerformance Timeline or any of the timestamp properties provided by the\nPerformanceNodeTiming
class. If the named endMark
does not exist, an\nerror will be thrown.
Returns the current high resolution millisecond timestamp, where 0 represents\nthe start of the current node
process.
Wraps 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('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 obs.disconnect();\n});\nobs.observe({ entryTypes: ['function'] });\n\n// A performance timeline entry will be created\nwrapped();\n
"
}
],
"properties": [
{
"textRaw": "`nodeTiming` {PerformanceNodeTiming}",
"type": "PerformanceNodeTiming",
"name": "nodeTiming",
"meta": {
"added": [
"v8.5.0"
],
"changes": []
},
"desc": "An 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 total number of milliseconds elapsed for this entry. This value will not\nbe meaningful for all Performance Entry types.
" }, { "textRaw": "`name` {string}", "type": "string", "name": "name", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The name of the performance entry.
" }, { "textRaw": "`startTime` {number}", "type": "number", "name": "startTime", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp marking the starting time of the\nPerformance Entry.
" }, { "textRaw": "`entryType` {string}", "type": "string", "name": "entryType", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The type of the performance entry. Currently it may be one of: 'node'
,\n'mark'
, 'measure'
, 'gc'
, 'function'
, or 'http2'
.
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
Provides timing details for Node.js itself.
", "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": "`loopExit` {number}", "type": "number", "name": "loopExit", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "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: PerformanceObserver", "type": "class", "name": "PerformanceObserver", "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\nPerformanceEntry
instances identified by options.entryTypes
.
When options.buffered
is false
, the callback
will be invoked once for\nevery PerformanceEntry
instance:
const {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n // called three times synchronously. list contains one item\n});\nobs.observe({ entryTypes: ['mark'] });\n\nfor (let n = 0; n < 3; n++)\n performance.mark(`test${n}`);\n
\nconst {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n // called once. list contains three items\n});\nobs.observe({ entryTypes: ['mark'], buffered: true });\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('perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n console.log(list.getEntries());\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
.
Returns a list of PerformanceEntry
objects in chronological order\nwith respect to performanceEntry.startTime
.
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
.
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\nto execute the callback).
\n'use strict';\nconst async_hooks = require('async_hooks');\nconst {\n performance,\n PerformanceObserver\n} = require('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 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('perf_hooks');\nconst mod = require('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 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"
}
]
}
],
"type": "module",
"displayName": "Performance Timing API"
},
{
"textRaw": "Punycode",
"name": "punycode",
"meta": {
"changes": [
{
"version": "v7.0.0",
"pr-url": "https://github.com/nodejs/node/pull/7941",
"description": "Accessing this module will now emit a deprecation warning."
}
]
},
"introduced_in": "v0.10.0",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "The 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.
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" }, { "textRaw": "Query String", "name": "querystring", "introduced_in": "v0.10.0", "stability": 2, "stabilityText": "Stable", "desc": "The querystring
module provides utilities for parsing and formatting URL\nquery strings. It can be accessed using:
const querystring = require('querystring');\n
",
"methods": [
{
"textRaw": "querystring.escape(str)",
"type": "method",
"name": "escape",
"meta": {
"added": [
"v0.1.25"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`str` {string}",
"name": "str",
"type": "string"
}
]
}
],
"desc": "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.",
"optional": true
},
{
"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.",
"optional": true
},
{
"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."
}
],
"optional": true
}
]
}
],
"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> | <boolean> | <string[]> | <number[]> | <boolean[]>\nAny other input values will be coerced to empty 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.
The readline
module provides an interface for reading data from a Readable\nstream (such as process.stdin
) one line at a time. It can be accessed using:
const readline = require('readline');\n
\nThe following simple example illustrates the basic use of the readline
module.
const readline = require('readline');\n\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout\n});\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 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 'close'
event is emitted when one of the following occur:
rl.close()
method is called and the readline.Interface
instance has\nrelinquished control over the input
and output
streams;input
stream receives its 'end'
event;input
stream receives <ctrl>-D
to signal end-of-transmission (EOT);input
stream receives <ctrl>-C
to signal SIGINT
and there is no\n'SIGINT'
event listener registered on the readline.Interface
instance.The listener function is called without passing any arguments.
\nThe readline.Interface
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 the <Enter>
, or <Return>
keys.
The listener function is called with a string containing the single line of\nreceived input.
\nrl.on('line', (input) => {\n console.log(`Received: ${input}`);\n});\n
"
},
{
"textRaw": "Event: 'pause'",
"type": "event",
"name": "pause",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'pause'
event is emitted when one of the following occur:
input
stream is paused.input
stream is not paused and receives the 'SIGCONT'
event. (See\nevents 'SIGTSTP'
and 'SIGCONT'
.)The listener function is called without passing any arguments.
\nrl.on('pause', () => {\n console.log('Readline paused.');\n});\n
"
},
{
"textRaw": "Event: 'resume'",
"type": "event",
"name": "resume",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'resume'
event is emitted whenever the input
stream is resumed.
The listener function is called without passing any arguments.
\nrl.on('resume', () => {\n console.log('Readline resumed.');\n});\n
"
},
{
"textRaw": "Event: 'SIGCONT'",
"type": "event",
"name": "SIGCONT",
"meta": {
"added": [
"v0.7.5"
],
"changes": []
},
"params": [],
"desc": "The 'SIGCONT'
event is emitted when a Node.js process previously moved into\nthe background using <ctrl>-Z
(i.e. SIGTSTP
) is then brought back to the\nforeground using fg(1p)
.
If the input
stream was paused before the SIGTSTP
request, this event will\nnot be emitted.
The listener function is invoked without passing any arguments.
\nrl.on('SIGCONT', () => {\n // `prompt` will automatically resume the stream\n rl.prompt();\n});\n
\nThe 'SIGCONT'
event is not supported on Windows.
The 'SIGINT'
event is emitted whenever the input
stream receives a\n<ctrl>-C
input, known typically as SIGINT
. If there are no 'SIGINT'
event\nlisteners registered when the input
stream receives a SIGINT
, the 'pause'
\nevent will be emitted.
The listener function is invoked without passing any arguments.
\nrl.on('SIGINT', () => {\n rl.question('Are you sure you want to exit? ', (answer) => {\n if (answer.match(/^y(es)?$/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 a <ctrl>-Z
\ninput, typically known as SIGTSTP
. If there are no 'SIGTSTP'
event listeners\nregistered when the input
stream receives a SIGTSTP
, the Node.js process\nwill 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 readline.Interface
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 readline.Interface
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 readline.Interface
instance.
The rl.prompt()
method writes the readline.Interface
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 readline.Interface
was created with output
set to null
or\nundefined
the prompt is not written.
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.
Example usage:
\nrl.question('What is your favorite food? ', (answer) => {\n console.log(`Oh, so your favorite food is ${answer}`);\n});\n
\nThe 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.
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.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.
If key
is specified, data
is ignored.
When called, rl.write()
will resume the input
stream if it has been\npaused.
If the readline.Interface
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\nreadline.Interface
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\nreadline.Interface
will always consume the input stream fully.
A caveat with using this experimental API is that the performance is\ncurrently not on par with the traditional 'line'
event API, and thus it is\nnot recommended for performance-sensitive applications. We expect this\nsituation to improve in the future.
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
"
}
]
}
],
"methods": [
{
"textRaw": "readline.clearLine(stream, dir)",
"type": "method",
"name": "clearLine",
"meta": {
"added": [
"v0.7.7"
],
"changes": []
},
"signatures": [
{
"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"
}
]
}
]
}
],
"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('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).
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)",
"type": "method",
"name": "cursorTo",
"meta": {
"added": [
"v0.7.7"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`stream` {stream.Writable}",
"name": "stream",
"type": "stream.Writable"
},
{
"textRaw": "`x` {number}",
"name": "x",
"type": "number"
},
{
"textRaw": "`y` {number}",
"name": "y",
"type": "number"
}
]
}
],
"desc": "The readline.cursorTo()
method moves cursor to the specified position in a\ngiven TTY stream
.
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
"
},
{
"textRaw": "readline.moveCursor(stream, dx, dy)",
"type": "method",
"name": "moveCursor",
"meta": {
"added": [
"v0.7.7"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`stream` {stream.Writable}",
"name": "stream",
"type": "stream.Writable"
},
{
"textRaw": "`dx` {number}",
"name": "dx",
"type": "number"
},
{
"textRaw": "`dy` {number}",
"name": "dy",
"type": "number"
}
]
}
],
"desc": "The readline.moveCursor()
method moves the cursor relative to its current\nposition in a given TTY stream
.
The following example illustrates the use of readline.Interface
class to\nimplement a small command-line interface:
const readline = require('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('fs');\nconst readline = require('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('fs');\nconst readline = require('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
"
}
],
"type": "module",
"displayName": "Readline"
},
{
"textRaw": "REPL",
"name": "repl",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "The repl
module provides a Read-Eval-Print-Loop (REPL) implementation that\nis available both as a standalone program or includible in other applications.\nIt can be accessed using:
const repl = require('repl');\n
",
"modules": [
{
"textRaw": "Design and Features",
"name": "design_and_features",
"desc": "The 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,\nsimplistic Emacs-style line editing, multi-line inputs, ANSI-styled output,\nsaving and restoring current REPL session state, error recovery, and\ncustomizable evaluation functions.
The following special commands are supported by all REPL instances:
\n.break
- When in the process of inputting a multi-line expression, entering\nthe .break
command (or pressing the <ctrl>-C
key combination) will abort\nfurther input or processing of that expression..clear
- Resets the REPL context
to an empty object and clears any\nmulti-line expression currently 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 finish, <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<ctrl>-C
- When pressed once, has the same effect as the .break
command.\nWhen pressed twice on a blank line, has the same effect as the .exit
\ncommand.<ctrl>-D
- Has the same effect as the .exit
command.<tab>
- When pressed on a blank line, displays global and local (scope)\nvariables. When pressed while entering other input, displays relevant\nautocompletion options.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\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('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('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('fs')
.
> fs.createReadStream('./some/file');\n
",
"type": "module",
"displayName": "Accessing Core Node.js Modules"
},
{
"textRaw": "Global Uncaught Exceptions",
"name": "global_uncaught_exceptions",
"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:
'uncaughtException'
event.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');\nError: foo\n> _error.message\n'foo'\n
",
"type": "module",
"displayName": "Assignment of the `_` (underscore) variable"
},
{
"textRaw": "`await` keyword",
"name": "`await`_keyword",
"desc": "With the --experimental-repl-await
command line option specified,\nexperimental support for the await
keyword is enabled.
> await Promise.resolve(123)\n123\n> await Promise.reject(new Error('REPL await'))\nError: REPL await\n at repl:1:45\n> const timeout = util.promisify(setTimeout);\nundefined\n> const old = Date.now(); await timeout(1000); console.log(Date.now() - old);\n1002\nundefined\n
",
"type": "module",
"displayName": "`await` keyword"
}
],
"type": "module",
"displayName": "Default Evaluation"
},
{
"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('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": "As a user is typing input into the REPL prompt, pressing the <enter>
key will\nsend the current line of input to the eval
function. In order to support\nmulti-line input, the eval function can return an instance of repl.Recoverable
\nto 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 useColors
boolean option can be\nspecified at construction to instruct the default writer to use ANSI style\ncodes to colorize the output from the util.inspect()
method.
It is possible to fully customize the output of a repl.REPLServer
instance\nby passing a new function in using the writer
option on construction. The\nfollowing example, for instance, simply converts any input text to upper case:
const repl = require('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 repl
module to provide its own interactive interface\nfor executing JavaScript. This can be used by executing the Node.js binary\nwithout 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 ''
will disable persistent\nREPL history. Whitespace will be trimmed from the value.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('net');\nconst repl = require('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.
The repl.REPLServer
class inherits from the readline.Interface
class.\nInstances of repl.REPLServer
are created using the repl.start()
method and\nshould not be created directly using the JavaScript new
keyword.
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 to signal SIGINT
,\nor by pressing <ctrl>-D
to signal 'end'
on the input stream. 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('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('repl');\n\nconst replServer = repl.start({ prompt: '> ' });\nreplServer.defineCommand('sayhello', {\n help: 'Say hello',\n action(name) {\n this.clearBufferedCommand();\n console.log(`Hello, ${name}!`);\n this.displayPrompt();\n }\n});\nreplServer.defineCommand('saybye', function saybye() {\n console.log('Goodbye!');\n this.close();\n});\n
\nThe new commands can then be used from within the REPL instance:
\n> .sayhello Node.js User\nHello, Node.js User!\n> .saybye\nGoodbye!\n
"
},
{
"textRaw": "replServer.displayPrompt([preserveCursor])",
"type": "method",
"name": "displayPrompt",
"meta": {
"added": [
"v0.1.91"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`preserveCursor` {boolean}",
"name": "preserveCursor",
"type": "boolean",
"optional": true
}
]
}
],
"desc": "The replServer.displayPrompt()
method readies the REPL instance for input\nfrom the user, printing the configured prompt
to a new line in the output
\nand resuming the input
to accept new input.
When multi-line input is being entered, an ellipsis is printed rather than the\n'prompt'.
\nWhen preserveCursor
is true
, the cursor placement will not be reset to 0
.
The replServer.displayPrompt
method is primarily intended to be called from\nwithin the action function for commands registered using the\nreplServer.defineCommand()
method.
The replServer.clearBufferedCommand()
method clears any command that has been\nbuffered but not yet executed. This method is primarily intended to be\ncalled from within the action function for commands registered using the\nreplServer.defineCommand()
method.
An internal method used to parse and execute REPLServer
keywords.\nReturns true
if keyword
is a valid keyword, otherwise false
.
The repl.start()
method creates and starts a repl.REPLServer
instance.
If options
is a string, then it specifies the input prompt:
const repl = require('repl');\n\n// a Unix style prompt\nrepl.start('$ ');\n
"
}
],
"type": "module",
"displayName": "REPL"
},
{
"textRaw": "Stream",
"name": "stream",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "A stream is an abstract interface for working with streaming data in Node.js.\nThe stream
module provides a base API that makes it easy to build objects\nthat implement 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
.
The stream
module can be accessed using:
const stream = require('stream');\n
\nWhile it is important to understand how streams work, the stream
module itself\nis most useful for developers that are creating new types of stream instances.\nDevelopers who are primarily consuming stream objects will rarely need to use\nthe stream
module directly.
This document is divided into two primary sections with a third section for\nadditional notes. The first section explains the elements of the stream API that\nare required to use streams within an application. The second section explains\nthe elements of the API that are required to implement 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 pipeline and\nfinished.
", "modules": [ { "textRaw": "Object Mode", "name": "object_mode", "desc": "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.
Both Writable
and Readable
streams will store data in an internal\nbuffer that can be retrieved using writable.writableBuffer
or\nreadable.readableBuffer
, respectively.
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.
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, it is important for each side to\noperate (and buffer) independently of the other.
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('stream');\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 is promisify-able as well;
const finished = util.promisify(stream.finished);\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
"
},
{
"textRaw": "stream.pipeline(...streams, callback)",
"type": "method",
"name": "pipeline",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`...streams` {Stream} Two or more streams to pipe between.",
"name": "...streams",
"type": "Stream",
"desc": "Two or more streams to pipe between."
},
{
"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"
}
]
}
]
}
],
"desc": "A module method to pipe between streams forwarding errors and properly cleaning\nup and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('stream');\nconst fs = require('fs');\nconst zlib = require('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 is promisify-able as well:
const pipeline = util.promisify(stream.pipeline);\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
"
}
],
"miscs": [
{
"textRaw": "API for Stream Consumers",
"name": "API for Stream Consumers",
"type": "misc",
"desc": "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('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 in JSON at position 1\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('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": []
},
"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.
Not all Writable
streams will emit the 'close'
event.
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 not closed when the 'error'
event is emitted.
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.end('This is the end\\n');\nwriter.on('finish', () => {\n console.log('All writes are now complete.');\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 avoid a situation where writing\nmany small chunks of data to a stream do not cause a backup in the internal\nbuffer that would have an adverse impact on performance. In such situations,\nimplementations that implement the writable._writev()
method can perform\nbuffered writes in a more optimized manner.
See also: writable.uncork()
.
Destroy the stream, and emit the passed 'error'
and a 'close'
event.\nAfter this call, the writable stream has ended and subsequent calls\nto write()
or end()
will result in an ERR_STREAM_DESTROYED
error.\nImplementors 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. If provided, the optional callback
function is attached as a listener\nfor the 'finish'
event.
Calling the stream.write()
method after calling\nstream.end()
will raise an error.
// write 'hello, ' and then end with 'world!'\nconst fs = require('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, it is recommended that calls to writable.uncork()
be\ndeferred using process.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
may or may not be called with the error as its\nfirst argument. To reliably detect write errors, add a listener for the\n'error'
event.
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.\nIt is recommended that once write()
returns false, no more chunks be written\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
if it is safe to call writable.write()
.
Return the value of highWaterMark
passed when constructing this\nWritable
.
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
.
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 make the stream to\nstop flowing, and the data 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('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()); });\npass.write('ok'); // will not emit 'data'\npass.resume(); // must be called to make stream emit 'data'\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.
Use of the readable.pipe()
method is recommended for most users as it has been\nimplemented to provide the easiest way of consuming stream data. Developers that\nrequire more fine-grained control over the transfer and generation of data can\nuse the EventEmitter
and readable.on('readable')
/readable.read()
\nor the readable.pause()
/readable.resume()
APIs.
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.
Not all Readable
streams will emit the 'close'
event.
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 'readable'
event is emitted when there is data available to be read from\nthe stream. In some cases, attaching a listener for the 'readable'
event will\ncause some amount of data to be read into an internal buffer.
const readable = getReadableStreamSomehow();\nreadable.on('readable', function() {\n // there is some data to read now\n let data;\n\n while (data = this.read()) {\n console.log(data);\n }\n});\n
\nThe 'readable'
event will also be emitted once the end of the stream data\nhas been reached but before the 'end'
event is emitted.
Effectively, the 'readable'
event indicates that the stream has new\ninformation: either new data is available or the end of the stream has been\nreached. In the former case, stream.read()
will return the\navailable data. In the latter case, stream.read()
will return\nnull
. For instance, in the following example, foo.txt
is an empty file:
const fs = require('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 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()
.
Destroy the stream, and emit 'error'
and 'close'
. After this call, the\nreadable stream will release any internal resources and subsequent calls\nto push()
will be ignored.\nImplementors 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('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('fs');\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 pulls some data out of the internal buffer and\nreturns it. If no data available to be read, null
is returned. By default,\nthe data will be 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 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();\nreadable.on('readable', () => {\n let chunk;\n while (null !== (chunk = readable.read())) {\n console.log(`Received ${chunk.length} bytes of data.`);\n }\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",
"optional": true
}
]
}
],
"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('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)",
"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|any} Chunk of data to unshift onto the read queue. For streams not operating in object mode, `chunk` must be a string, `Buffer` or `Uint8Array`. For object mode streams, `chunk` may be any JavaScript value other than `null`.",
"name": "chunk",
"type": "Buffer|Uint8Array|string|any",
"desc": "Chunk of data to unshift onto the read queue. For streams not operating in object mode, `chunk` must be a string, `Buffer` or `Uint8Array`. For object mode streams, `chunk` may be any JavaScript value other than `null`."
}
]
}
],
"desc": "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('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.match(/\\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 } else {\n // still reading the header.\n header += str;\n }\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 stream
module API\nas it is currently defined. (See Compatibility for more information.)
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('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": []
},
"stability": 1,
"stabilityText": "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('fs');\n\nasync function print(readable) {\n readable.setEncoding('utf8');\n let data = '';\n for await (const k of readable) {\n data += k;\n }\n console.log(data);\n}\n\nprint(fs.createReadStream('file')).catch(console.log);\n
\nIf the loop terminates with a break
or a throw
, the stream will be\ndestroyed. 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 64kb of data because no highWaterMark
option is provided to\nfs.createReadStream()
.
Is true
if it is safe to call readable.read()
.
Returns the value of highWaterMark
passed when constructing this\nReadable
.
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
.
Duplex streams are streams that implement both the Readable
and\nWritable
interfaces.
Examples of Duplex
streams include:
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 emit 'error'
. 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'
.
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('stream');\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 is promisify-able as well;
const finished = util.promisify(stream.finished);\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
"
},
{
"textRaw": "stream.pipeline(...streams, callback)",
"type": "method",
"name": "pipeline",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`...streams` {Stream} Two or more streams to pipe between.",
"name": "...streams",
"type": "Stream",
"desc": "Two or more streams to pipe between."
},
{
"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"
}
]
}
]
}
],
"desc": "A module method to pipe between streams forwarding errors and properly cleaning\nup and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('stream');\nconst fs = require('fs');\nconst zlib = require('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 is promisify-able as well:
const pipeline = util.promisify(stream.pipeline);\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
"
}
]
},
{
"textRaw": "API for Stream Implementers",
"name": "API for Stream Implementers",
"type": "misc",
"desc": "The 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('stream');\n\nclass MyWritable extends Writable {\n constructor(options) {\n super(options);\n // ...\n }\n}\n
\nThe 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.
", "miscs": [ { "textRaw": "Simplified Construction", "name": "simplified_construction", "meta": { "added": [ "v1.2.0" ], "changes": [] }, "desc": "For many simple cases, it is possible to construct 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('stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n // ...\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()
method. The\nwritable._writev()
method may also be implemented.
const { Writable } = require('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('stream');\nconst util = require('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('stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n // ...\n },\n writev(chunks, callback) {\n // ...\n }\n});\n
"
}
],
"methods": [
{
"textRaw": "writable._write(chunk, encoding, callback)",
"type": "method",
"name": "_write",
"signatures": [
{
"params": [
{
"textRaw": "`chunk` {Buffer|string|any} The chunk to be written. Will **always** be a buffer unless the `decodeStrings` option was set to `false` or the stream is operating in object mode.",
"name": "chunk",
"type": "Buffer|string|any",
"desc": "The chunk to be written. Will **always** be a buffer unless the `decodeStrings` option was set to `false` or the stream is operating in object mode."
},
{
"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()
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
method must be called to signal either that the write completed\nsuccessfully or failed with an error. The first argument passed to the\ncallback
must be the Error
object if the call failed or null
if the\nwrite 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 to\nwritable._write()
in stream implementations that are capable of processing\nmultiple chunks of data at once. If implemented, the method will be called with\nall chunks of data currently buffered in the write queue.
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.
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.
It is recommended that errors occurring during the processing of the\nwritable._write()
and writable._writev()
methods are reported by invoking\nthe callback and passing the error as the first argument. This will cause an\n'error'
event to be emitted by the Writable
. Throwing an Error
from within\nwritable._write()
can result in unexpected and inconsistent behavior depending\non how the stream is being used. Using the callback ensures consistent and\npredictable handling of errors.
If a Readable
stream pipes into a Writable
stream when Writable
emits an\nerror, the Readable
stream will be unpiped.
const { Writable } = require('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('stream');\n\nclass MyWritable extends Writable {\n constructor(options) {\n super(options);\n // ...\n }\n\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('stream');\nconst { StringDecoder } = require('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('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('stream');\nconst util = require('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('stream');\n\nconst myReadable = new Readable({\n read(size) {\n // ...\n }\n});\n
"
}
],
"methods": [
{
"textRaw": "readable._read(size)",
"type": "method",
"name": "_read",
"meta": {
"added": [
"v0.9.4"
],
"changes": [
{
"version": "v10.0.0",
"pr-url": "https://github.com/nodejs/node/pull/17979",
"description": "call `_read()` only once per microtick"
}
]
},
"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, the\nimplementation should begin pushing that data into the read queue using the\nthis.push(dataChunk)
method. _read()
should continue reading\nfrom the resource and pushing data until readable.push()
returns false
. Only\nwhen _read()
is called again after it has stopped should it resume pushing\nadditional data onto the queue.
Once the readable._read()
method has been called, it will not be called again\nuntil the readable.push()
method is called. readable._read()
\nis guaranteed to be called only once within a synchronous execution, i.e. a\nmicrotick.
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 intended be called only by Readable
\nimplementers, and only from within 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.
It is recommended that errors occurring during the processing of the\nreadable._read()
method are emitted using the 'error'
event rather than\nbeing thrown. Throwing an Error
from within readable._read()
can result in\nunexpected and inconsistent behavior depending on whether the stream is\noperating in flowing or paused mode. Using the 'error'
event ensures\nconsistent and predictable handling of errors.
const { Readable } = require('stream');\n\nconst myReadable = new Readable({\n read(size) {\n if (checkSomeErrorCondition()) {\n process.nextTick(() => this.emit('error', err));\n return;\n }\n // do some work\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('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('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('stream');\nconst util = require('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('stream');\n\nconst myDuplex = new Duplex({\n read(size) {\n // ...\n },\n write(chunk, encoding, callback) {\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('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('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 readable._read()
\nmethods. Custom Transform
implementations must implement the\ntransform._transform()
method and may also implement\nthe 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('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('stream');\nconst util = require('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('stream');\n\nconst myTransform = new Transform({\n transform(chunk, encoding, callback) {\n // ...\n }\n});\n
"
}
],
"modules": [
{
"textRaw": "Events: 'finish' and 'end'",
"name": "events:_'finish'_and_'end'",
"desc": "The 'finish'
and 'end'
events are from the stream.Writable
\nand stream.Readable
classes, respectively. The 'finish'
event is emitted\nafter stream.end()
is called and all chunks have been processed\nby stream._transform()
. The 'end'
event is emitted\nafter all data has been output, which occurs after the callback in\ntransform._flush()
has been called.
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 readable.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 readable.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\nreadable.push()
method. In other words, 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.
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.
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.
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.
The string_decoder
module provides an API for decoding Buffer
objects into\nstrings in a manner that preserves encoded multi-byte UTF-8 and UTF-16\ncharacters. It can be accessed using:
const { StringDecoder } = require('string_decoder');\n
\nThe following example shows the basic use of the StringDecoder
class.
const { StringDecoder } = require('string_decoder');\nconst decoder = new StringDecoder('utf8');\n\nconst cent = Buffer.from([0xC2, 0xA2]);\nconsole.log(decoder.write(cent));\n\nconst euro = Buffer.from([0xE2, 0x82, 0xAC]);\nconsole.log(decoder.write(euro));\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('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])));\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` {Buffer|TypedArray|DataView} A `Buffer`, or `TypedArray`, or `DataView` containing the bytes to decode.",
"name": "buffer",
"type": "Buffer|TypedArray|DataView",
"desc": "A `Buffer`, or `TypedArray`, or `DataView` containing the bytes to decode.",
"optional": true
}
]
}
],
"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.
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.
The 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('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.
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.
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.
Calling timeout.unref()
creates an internal timer that will wake the Node.js\nevent loop. Creating too many of these can adversely impact performance\nof the Node.js application.
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": [] }, "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.", "optional": true } ] } ], "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\nutil.promisify()
:
const util = require('util');\nconst setImmediatePromise = util.promisify(setImmediate);\n\nsetImmediatePromise('foobar').then((value) => {\n // value === 'foobar' (passing values is optional)\n // This is executed after all I/O callbacks.\n});\n\n// or with async function\nasync function timerExample() {\n console.log('Before I/O callbacks');\n await setImmediatePromise();\n console.log('After I/O callbacks');\n}\ntimerExample();\n
"
},
{
"textRaw": "setInterval(callback, delay[, ...args])",
"type": "method",
"name": "setInterval",
"meta": {
"added": [
"v0.0.1"
],
"changes": []
},
"signatures": [
{
"return": {
"textRaw": "Returns: {Timeout} for use with [`clearInterval()`][]",
"name": "return",
"type": "Timeout",
"desc": "for use with [`clearInterval()`][]"
},
"params": [
{
"textRaw": "`callback` {Function} The function to call when the timer elapses.",
"name": "callback",
"type": "Function",
"desc": "The function to call when the timer elapses."
},
{
"textRaw": "`delay` {number} The number of milliseconds to wait before calling the `callback`.",
"name": "delay",
"type": "number",
"desc": "The number of milliseconds to wait before calling the `callback`."
},
{
"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.",
"optional": true
}
]
}
],
"desc": "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
.
If callback
is not a function, a TypeError
will be thrown.
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
.
If callback
is not a function, a TypeError
will be thrown.
This method has a custom variant for promises that is available using\nutil.promisify()
:
const util = require('util');\nconst setTimeoutPromise = util.promisify(setTimeout);\n\nsetTimeoutPromise(40, 'foobar').then((value) => {\n // value === 'foobar' (passing values is optional)\n // This is executed after about 40 milliseconds.\n});\n
"
}
],
"type": "module",
"displayName": "Scheduling Timers"
},
{
"textRaw": "Cancelling Timers",
"name": "cancelling_timers",
"desc": "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.
It is not possible to cancel timers that were created using the promisified\nvariants of setImmediate()
, setTimeout()
.
Cancels an Immediate
object created by setImmediate()
.
Cancels a Timeout
object created by setInterval()
.
Cancels a Timeout
object created by setTimeout()
.
The 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('tls');\n
",
"modules": [
{
"textRaw": "TLS/SSL Concepts",
"name": "tls/ssl_concepts",
"desc": "The TLS/SSL is a public/private key infrastructure (PKI). For most common\ncases, each client and 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 of\nkey-agreement (i.e., key-exchange) methods. That is, the server and client keys\nare used to negotiate new temporary keys that are used specifically and only for\nthe current communication session. Practically, this means that even if the\nserver's private key is compromised, communication can only be decrypted by\neavesdroppers 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):
\nEphemeral methods may have some performance drawbacks, because key generation\nis expensive.
\nTo use Perfect Forward Secrecy using DHE
with the tls
module, it is required\nto generate Diffie-Hellman parameters and specify them with the dhparam
\noption to tls.createSecureContext()
. The following illustrates the use of\nthe OpenSSL command-line interface to generate such parameters:
openssl dhparam -outform PEM -out dhparam.pem 2048\n
\nIf using Perfect Forward Secrecy using ECDHE
, Diffie-Hellman parameters are\nnot required and a default ECDHE curve will be used. The ecdhCurve
property\ncan be used when creating a TLS Server to specify the list of names of supported\ncurves to use, see tls.createServer()
for more info.
ALPN (Application-Layer Protocol Negotiation Extension) and\nSNI (Server Name Indication) are TLS handshake extensions:
\nThe 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.
\nTo test the renegotiation limits on a server, connect to it using the OpenSSL\ncommand-line client (openssl s_client -connect address:port
) then input\nR<CR>
(i.e., the letter R
followed by a carriage return) multiple times.
Node.js is built with a default suite of enabled and disabled TLS ciphers.\nCurrently, the default cipher suite is:
\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
command\nline switch. For instance, the following makes\nECDHE-RSA-AES128-GCM-SHA256:!RC4
the default TLS cipher suite:
node --tls-cipher-list=\"ECDHE-RSA-AES128-GCM-SHA256:!RC4\"\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.
Consult OpenSSL cipher list format documentation for details on the format.
\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.
\n128 bit AES is preferred over 192 and 256 bit AES in light of specific\nattacks affecting larger AES key sizes.
\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.
", "type": "module", "displayName": "Modifying the Default TLS Cipher suite" }, { "textRaw": "Deprecated APIs", "name": "deprecated_apis", "classes": [ { "textRaw": "Class: CryptoStream", "type": "class", "name": "CryptoStream", "meta": { "added": [ "v0.3.4" ], "deprecated": [ "v0.11.3" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`tls.TLSSocket`][] instead.", "desc": "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.
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
.
The tls.Server
class is a subclass of net.Server
that accepts encrypted\nconnections using TLS or SSL.
The 'newSession'
event is emitted upon creation of a new TLS session. This may\nbe used to store sessions in external storage. The listener callback is passed\nthree arguments when called:
sessionId
- The TLS session identifiersessionData
- 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
- The TLS/SSL session identifiercallback
<Function> A callback function to be called when the prior session\nhas been recovered.When called, the event listener may perform a lookup in external storage using\nthe given sessionId
and invoke callback(null, sessionData)
once finished. If\nthe session cannot be resumed (i.e., doesn't exist in storage) the callback may\nbe invoked as callback(null, null)
. Calling callback(err)
will terminate the\nincoming connection 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. Note that 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, tlsSocket.alpnProtocol
\nequals 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).
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 a Buffer
instance holding the keys currently used for\nencryption/decryption of the TLS Session Tickets.
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.
Updates the keys for encryption/decryption of the TLS Session Tickets.
\nThe key's Buffer
should be 48 bytes long. See ticketKeys
option in\ntls.createServer()
for more information on how it is used.
Changes to the ticket keys are effective only for future server connections.\nExisting or currently pending server connections will use the previous keys.
" } ], "properties": [ { "textRaw": "`connections` {number}", "type": "number", "name": "connections", "meta": { "added": [ "v0.3.2" ], "deprecated": [ "v0.9.7" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`server.getConnections()`][] instead.", "desc": "Returns the current number of concurrent connections on the server.
" } ] }, { "textRaw": "Class: tls.TLSSocket", "type": "class", "name": "tls.TLSSocket", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "The tls.TLSSocket
is a subclass of net.Socket
that performs transparent\nencryption of written data and all required TLS negotiation.
Instances 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 '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.
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
.
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 representing the cipher name. The version
key is a legacy\nfield which always contains the value 'TLSv1/SSLv3'
.
For example: { name: 'AES256-SHA', version: 'TLSv1/SSLv3' }
.
See SSL_CIPHER_get_name()
in\nhttps://www.openssl.org/docs/man1.1.0/ssl/SSL_CIPHER_get_name.html for more\ninformation.
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.
\nraw
<Buffer> The DER encoded X.509 certificate data.subject
<Object> The certificate subject, described in terms of\n Country (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\n subject
.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.\n Example: '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.\n It 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
<Array> (Optional) An array of names for the subject, an\n alternative to the subject
names.infoAccess
<Array> (Optional) An array describing the AuthorityInfoAccess,\n used with OCSP.issuerCert
<Object> (Optional) The issuer certificate object. For\n self-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{ 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 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 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'TLSv1'
'TLSv1.1'
'TLSv1.2'
'SSLv3'
See https://www.openssl.org/docs/man1.1.0/ssl/SSL_get_version.html for more\ninformation.
" }, { "textRaw": "tlsSocket.getSession()", "type": "method", "name": "getSession", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Returns the ASN.1 encoded TLS session or undefined
if no session was\nnegotiated. Can be used to speed up handshake establishment when reconnecting\nto the server.
Returns the TLS session ticket or undefined
if no session was negotiated.
This only works with client TLS sockets. Useful only for debugging, for session\nreuse provide session
option to tls.connect()
.
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.
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
.
Returns true
if the peer certificate was signed by one of the CAs specified\nwhen 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` {number}", "type": "number", "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 can be overwritten by providing alternative function as part of\nthe options.checkServerIdentity
option 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
).
The callback
function, if specified, will be added as a listener for the\n'secureConnect'
event.
tls.connect()
returns a tls.TLSSocket
object.
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('tls');\nconst fs = require('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()`][].",
"optional": true
},
{
"textRaw": "`callback` {Function} See [`tls.connect()`][].",
"name": "callback",
"type": "Function",
"desc": "See [`tls.connect()`][].",
"optional": true
}
]
}
],
"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`.", "optional": true }, { "textRaw": "`options` {Object} See [`tls.connect()`][].", "name": "options", "type": "Object", "desc": "See [`tls.connect()`][].", "optional": true }, { "textRaw": "`callback` {Function} See [`tls.connect()`][].", "name": "callback", "type": "Function", "desc": "See [`tls.connect()`][].", "optional": true } ] } ], "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": "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", "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": "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\".", "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\"." }, { "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": "`ciphers` {string} Cipher suite specification, replacing the default. For more information, see [modifying the default 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 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} Diffie Hellman parameters, required for [Perfect Forward Secrecy][]. Use `openssl dhparam` to create the parameters. The key length must be greater than or equal to 1024 bits, otherwise an error will be thrown. It is strongly recommended to use 2048 bits or larger for stronger security. If omitted or invalid, the parameters are silently discarded and DHE ciphers will not be available.", "name": "dhparam", "type": "string|Buffer", "desc": "Diffie Hellman parameters, required for [Perfect Forward Secrecy][]. Use `openssl dhparam` to create the parameters. The key length must be greater than or equal to 1024 bits, otherwise an error will be thrown. It is strongly recommended to use 2048 bits or larger for stronger security. If omitted or invalid, the parameters are silently discarded and DHE ciphers will not 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 credentials object.
A key is required for ciphers that make use of certificates. Either key
or\npfx
can be used to provide it.
If the 'ca' option is not given, then Node.js will use the default\npublicly trusted list of CAs as given in\nhttps://hg.mozilla.org/mozilla-central/raw-file/tip/security/nss/lib/ckfw/builtins/certdata.txt.
" }, { "textRaw": "tls.createServer([options][, secureConnectionListener])", "type": "method", "name": "createServer", "meta": { "added": [ "v0.3.2" ], "changes": [ { "version": "v9.3.0", "pr-url": "https://github.com/nodejs/node/pull/14903", "description": "The `options` parameter can now include `clientCertEngine`." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11984", "description": "The `ALPNProtocols` option can be a `TypedArray` or `DataView` now." }, { "version": "v5.0.0", "pr-url": "https://github.com/nodejs/node/pull/2564", "description": "ALPN options are supported now." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {tls.Server}", "name": "return", "type": "tls.Server" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`ALPNProtocols`: {string[]|Buffer[]|TypedArray[]|DataView[]|Buffer| TypedArray|DataView} An array of strings, `Buffer`s or `TypedArray`s or `DataView`s, or a single `Buffer` or `TypedArray` or `DataView` containing the supported ALPN protocols. `Buffer`s should have the format `[len][name][len][name]...` e.g. `0x05hello0x05world`, where the first byte is the length of the next protocol name. Passing an array is usually much simpler, e.g. `['hello', 'world']`. (Protocols should be ordered by their priority.)", "name": "ALPNProtocols", "type": "string[]|Buffer[]|TypedArray[]|DataView[]|Buffer| TypedArray|DataView", "desc": "An array of strings, `Buffer`s or `TypedArray`s or `DataView`s, or a single `Buffer` or `TypedArray` or `DataView` containing the supported ALPN protocols. `Buffer`s should have the format `[len][name][len][name]...` e.g. `0x05hello0x05world`, where the first byte is the length of the next protocol name. Passing an array is usually much simpler, e.g. `['hello', 'world']`. (Protocols should be ordered by their priority.)" }, { "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": "`handshakeTimeout` {number} Abort the connection if the SSL/TLS handshake does not finish in the specified number of milliseconds. A `'tlsClientError'` is emitted on the `tls.Server` object whenever a handshake times out. **Default:** `120000` (120 seconds).", "name": "handshakeTimeout", "type": "number", "default": "`120000` (120 seconds)", "desc": "Abort the connection if the SSL/TLS handshake does not finish in the specified number of milliseconds. A `'tlsClientError'` is emitted on the `tls.Server` object whenever a handshake times out." }, { "textRaw": "`rejectUnauthorized` {boolean} If not `false` the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect if `requestCert` is `true`. **Default:** `true`.", "name": "rejectUnauthorized", "type": "boolean", "default": "`true`", "desc": "If not `false` the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect if `requestCert` is `true`." }, { "textRaw": "`requestCert` {boolean} If `true` the server will request a certificate from clients that connect and attempt to verify that certificate. **Default:** `false`.", "name": "requestCert", "type": "boolean", "default": "`false`", "desc": "If `true` the server will request a certificate from clients that connect and attempt to verify that certificate." }, { "textRaw": "`sessionTimeout` {number} An integer specifying the number of seconds after which the TLS session identifiers and TLS session tickets created by the server will time out. See [`SSL_CTX_set_timeout`] for more details.", "name": "sessionTimeout", "type": "number", "desc": "An integer specifying the number of seconds after which the TLS session identifiers and TLS session tickets created by the server will time out. See [`SSL_CTX_set_timeout`] for more details." }, { "textRaw": "`SNICallback(servername, cb)` {Function} A function that will be called if the client supports SNI TLS extension. Two arguments will be passed when called: `servername` and `cb`. `SNICallback` should invoke `cb(null, ctx)`, where `ctx` is a `SecureContext` instance. (`tls.createSecureContext(...)` can be used to get a proper `SecureContext`.) If `SNICallback` wasn't provided the default callback with high-level API will be used (see below).", "name": "SNICallback(servername,", "desc": "cb)` {Function} A function that will be called if the client supports SNI TLS extension. Two arguments will be passed when called: `servername` and `cb`. `SNICallback` should invoke `cb(null, ctx)`, where `ctx` is a `SecureContext` instance. (`tls.createSecureContext(...)` can be used to get a proper `SecureContext`.) If `SNICallback` wasn't provided the default callback with high-level API will be used (see below)." }, { "textRaw": "`ticketKeys`: A 48-byte `Buffer` instance consisting of a 16-byte prefix, a 16-byte HMAC key, and a 16-byte AES key. This can be used to accept TLS session tickets on multiple instances of the TLS server.", "name": "ticketKeys", "desc": "A 48-byte `Buffer` instance consisting of a 16-byte prefix, a 16-byte HMAC key, and a 16-byte AES key. This can be used to accept TLS session tickets on multiple instances of the TLS server." }, { "textRaw": "...: Any [`tls.createSecureContext()`][] option can be provided. For servers, the identity options (`pfx` or `key`/`cert`) are usually required.", "name": "...", "desc": "Any [`tls.createSecureContext()`][] option can be provided. For servers, the identity options (`pfx` or `key`/`cert`) are usually required." } ], "optional": true }, { "textRaw": "`secureConnectionListener` {Function}", "name": "secureConnectionListener", "type": "Function", "optional": true } ] } ], "desc": "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 cluster
module\nworkers.
The following illustrates a simple echo server:
\nconst tls = require('tls');\nconst fs = require('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 SSL ciphers.
\nconsole.log(tls.getCiphers()); // ['AES128-SHA', 'AES256-SHA', ...]\n
"
}
],
"properties": [
{
"textRaw": "tls.DEFAULT_ECDH_CURVE",
"name": "DEFAULT_ECDH_CURVE",
"meta": {
"added": [
"v0.11.13"
],
"changes": []
},
"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.
Trace Event provides a mechanism to centralize tracing information generated by\nV8, Node.js core, and userspace code.
\nTracing can be enabled with the --trace-event-categories
command-line flag\nor by using the 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.environment
- Enables capture of Node.js Environment milestones.node.fs.sync
- Enables capture of trace data for file system sync methods.node.perf
- Enables capture of Performance API measurements.
node.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 vm
module's\nrunInNewContext()
, runInContext()
, and runInThisContext()
methods.v8
- The V8 events are GC, compiling, and execution related.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 trace_events
module:
const trace_events = require('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
\nStarting with Node.js 10.0.0, the 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('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
",
"type": "module",
"displayName": "`tracing.disable()`"
},
{
"textRaw": "`tracing.enable()`",
"name": "`tracing.enable()`",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"desc": "Enables this Tracing
object for the set of categories covered by the\nTracing
object.
true
only if the Tracing
object has been enabled.options
<Object>
categories
<string[]> An array of trace category names. Values included\nin the array are coerced to a string when possible. An error will be\nthrown if the value cannot be coerced.Creates and returns a Tracing
object for the given set of categories
.
const trace_events = require('trace_events');\nconst categories = ['node.perf', 'node.async_hooks'];\nconst tracing = trace_events.createTracing({ categories });\ntracing.enable();\n// do stuff\ntracing.disable();\n
",
"type": "module",
"displayName": "`trace_events.createTracing(options)`"
},
{
"textRaw": "`trace_events.getEnabledCategories()`",
"name": "`trace_events.getenabledcategories()`",
"meta": {
"added": [
"v10.0.0"
],
"changes": []
},
"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('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
",
"type": "module",
"displayName": "`trace_events.getEnabledCategories()`"
}
],
"type": "module",
"displayName": "The `trace_events` module"
}
],
"type": "module",
"displayName": "Trace Events"
},
{
"textRaw": "TTY",
"name": "tty",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "The tty
module provides the tty.ReadStream
and tty.WriteStream
classes.\nIn most cases, it will not be necessary or possible to use this module directly.\nHowever, it can be accessed using:
const tty = require('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.
The tty.ReadStream
class is a subclass of net.Socket
that represents the\nreadable side of a TTY. In normal circumstances process.stdin
will be the\nonly tty.ReadStream
instance in a Node.js process and there should be no\nreason to create additional instances.
A boolean
that is true
if the TTY is currently configured to operate as a\nraw device. Defaults to false
.
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 characters.\nNote that CTRL
+C
will no longer cause a SIGINT
when in this mode.
The tty.WriteStream
class is a subclass of net.Socket
that represents\nthe writable side of a TTY. In normal circumstances, process.stdout
and\nprocess.stderr
will be the only tty.WriteStream
instances created for a\nNode.js process and there should 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)",
"type": "method",
"name": "clearLine",
"meta": {
"added": [
"v0.7.7"
],
"changes": []
},
"signatures": [
{
"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"
}
]
}
]
}
],
"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\ncolors 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.\nTo enforce a specific behavior without relying on process.env
it is possible\nto pass in an object with different settings.
Use the NODE_DISABLE_COLORS
environment variable to enforce this function to\nalways return 1.
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.
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.
The dgram
module provides an implementation of UDP Datagram sockets.
const dgram = require('dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.log(`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// 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": "The dgram.Socket
object is an EventEmitter
that encapsulates the\ndatagram functionality.
New 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 'error'
event is emitted whenever any error occurs. The event handler\nfunction is passed a single Error
object.
The 'listening'
event is emitted whenever a socket begins listening for\ndatagram messages. This occurs as soon as UDP sockets are created.
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
.
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 sharing a UDP socket across multiple cluster
workers, the\nsocket.addMembership()
function must be called only once or an\nEADDRINUSE
error will occur:
const cluster = require('cluster');\nconst dgram = require('dgram');\nif (cluster.isMaster) {\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.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.
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.
Note that 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:
\nconst dgram = require('dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.log(`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// 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",
"optional": true
}
]
}
],
"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.
Note that 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\nuse 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.",
"optional": true
}
]
}
],
"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.
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.
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.
Broadcasts a datagram on the socket. The destination port
and address
must\nbe specified.
The msg
argument contains the message to be sent.\nDepending on its type, different behavior can apply. If msg
is a Buffer
\nor Uint8Array
,\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 falsy, '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.\nNote that DNS 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
or Uint8Array
.
Example of sending a UDP packet to a port on localhost
;
const dgram = require('dgram');\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
;
const dgram = require('dgram');\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. It is important to run benchmarks to\ndetermine the optimal strategy on a case-by-case basis. Generally speaking,\nhowever, sending multiple buffers is faster.
\nA Note about UDP datagram size
\nThe 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 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.
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.
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.
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 argument passed to socket.setMulticastTTL()
is a number of hops\nbetween 0 and 255. The default on most systems is 1
but can vary.
Sets the SO_RCVBUF
socket option. Sets the maximum socket receive buffer\nin bytes.
Sets the SO_SNDBUF
socket option. Sets the maximum socket send buffer\nin bytes.
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 argument to socket.setTTL()
is a number of hops between 1 and 255.\nThe default on most systems is 64 but can vary.
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 addition effect.
The socket.unref()
method returns a reference to the socket so calls can be\nchained.
As of Node.js v0.10, dgram.Socket#bind()
changed to an asynchronous\nexecution model. Legacy code would use synchronous behavior:
const s = dgram.createSocket('udp4');\ns.bind(1234);\ns.addMembership('224.0.0.114');\n
\nSuch legacy code would need to be changed to pass a callback function to the\ndgram.Socket#bind()
function:
const s = dgram.createSocket('udp4');\ns.bind(1234, () => {\n s.addMembership('224.0.0.114');\n});\n
",
"type": "module",
"displayName": "Change to asynchronous `socket.bind()` behavior"
}
]
}
],
"modules": [
{
"textRaw": "`dgram` module functions",
"name": "`dgram`_module_functions",
"methods": [
{
"textRaw": "dgram.createSocket(options[, callback])",
"type": "method",
"name": "createSocket",
"meta": {
"added": [
"v0.11.13"
],
"changes": [
{
"version": "v8.6.0",
"pr-url": "https://github.com/nodejs/node/pull/14560",
"description": "The `lookup` option is supported."
},
{
"version": "v8.7.0",
"pr-url": "https://github.com/nodejs/node/pull/13623",
"description": "The `recvBufferSize` and `sendBufferSize` options are supported now."
},
{
"version": "v11.4.0",
"pr-url": "https://github.com/nodejs/node/pull/23798",
"description": "The `ipv6Only` option is supported."
}
]
},
"signatures": [
{
"return": {
"textRaw": "Returns: {dgram.Socket}",
"name": "return",
"type": "dgram.Socket"
},
"params": [
{
"textRaw": "`options` {Object} Available options are:",
"name": "options",
"type": "Object",
"desc": "Available options are:",
"options": [
{
"textRaw": "`type` {string} The family of socket. Must be either `'udp4'` or `'udp6'`. Required.",
"name": "type",
"type": "string",
"desc": "The family of socket. Must be either `'udp4'` or `'udp6'`. Required."
},
{
"textRaw": "`reuseAddr` {boolean} When `true` [`socket.bind()`][] will reuse the address, even if another process has already bound a socket on it. **Default:** `false`.",
"name": "reuseAddr",
"type": "boolean",
"default": "`false`",
"desc": "When `true` [`socket.bind()`][] will reuse the address, even if another process has already bound a socket on it."
},
{
"textRaw": "`ipv6Only` {boolean} Setting `ipv6Only` to `true` will disable dual-stack support, i.e., binding to address `::` won't make `0.0.0.0` be bound. **Default:** `false`.",
"name": "ipv6Only",
"type": "boolean",
"default": "`false`",
"desc": "Setting `ipv6Only` to `true` will disable dual-stack support, i.e., binding to address `::` won't make `0.0.0.0` be bound."
},
{
"textRaw": "`recvBufferSize` {number} - Sets the `SO_RCVBUF` socket value.",
"name": "recvBufferSize",
"type": "number",
"desc": "Sets the `SO_RCVBUF` socket value."
},
{
"textRaw": "`sendBufferSize` {number} - Sets the `SO_SNDBUF` socket value.",
"name": "sendBufferSize",
"type": "number",
"desc": "Sets the `SO_SNDBUF` socket value."
},
{
"textRaw": "`lookup` {Function} Custom lookup function. **Default:** [`dns.lookup()`][].",
"name": "lookup",
"type": "Function",
"default": "[`dns.lookup()`][]",
"desc": "Custom lookup function."
}
]
},
{
"textRaw": "`callback` {Function} Attached as a listener for `'message'` events. Optional.",
"name": "callback",
"type": "Function",
"desc": "Attached as a listener for `'message'` events. Optional.",
"optional": true
}
]
}
],
"desc": "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
.
Creates a dgram.Socket
object of the specified type
. The type
argument\ncan be either 'udp4'
or 'udp6'
. An optional callback
function can be\npassed which is added as a listener for 'message'
events.
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
.
The url
module provides utilities for URL resolution and parsing. It can be\naccessed using:
const url = require('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 url
module provides two APIs for working with URLs: a legacy API that is\nNode.js specific, and a newer API that implements the same\nWHATWG URL Standard used by web browsers.
While the Legacy API has not been deprecated, it is maintained solely for\nbackwards compatibility with existing applications. New application code\nshould use the WHATWG API.
\nA comparison between the WHATWG and Legacy APIs is provided below. Above the URL\n'http://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:
\nconst url = require('url');\nconst myURL =\n url.parse('https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash');\n
",
"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. Note that 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 hostname 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\nmyURL.hostname = 'example.com:82';\nconsole.log(myURL.href);\n// Prints https://example.com:81/foo\n
\nInvalid hostname 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. Note that 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. Note that 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 |
\"gopher\" | \n70 | \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
\nNote that numbers 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
\nThe protocol schemes considered to be special by the WHATWG URL Standard\ninclude: ftp
, file
, gopher
, 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. Note that 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; to replace the entirety of query parameters of\nthe URL, use the url.search
setter. See URLSearchParams
\ndocumentation for details.
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. Note that 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()
.
Because of the need for standard compliance, this method does not allow users\nto customize the serialization process of the URL. For more flexibility,\nrequire('url').format()
method might be of interest.
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
"
}
],
"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.",
"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."
},
{
"textRaw": "`base` {string|URL} The base URL to resolve against if the `input` is not absolute.",
"name": "base",
"type": "string|URL",
"desc": "The base URL to resolve against if the `input` is not absolute.",
"optional": true
}
],
"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
\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 hostname of input
will be\nautomatically converted to ASCII using the Punycode algorithm.
const myURL = new URL('https://測試');\n// https://xn--g6w251d/\n
\nThis feature is only available if the node
executable was compiled with\nICU enabled. If not, the domain names are passed through unchanged.
In 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)", "type": "method", "name": "delete", "signatures": [ { "params": [ { "textRaw": "`name` {string}", "name": "name", "type": "string" } ] } ], "desc": "Remove 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} or `null` if there is no name-value pair with the given `name`.",
"name": "return",
"type": "string",
"desc": "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.
Returns true
if there is at least one name-value pair 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
"
}
],
"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": []
},
"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()
.
const url = require('url');\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": []
},
"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()
.
const url = require('url');\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.
\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."
}
],
"optional": true
}
]
}
],
"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.
const 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.
new 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%.js', 'file:'); // Incorrect: file:///some/path%\npathToFileURL('/some/path%.js'); // Correct: file:///some/path%25 (POSIX)\n
"
}
],
"type": "module",
"displayName": "The WHATWG URL API"
},
{
"textRaw": "Legacy URL API",
"name": "legacy_url_api",
"stability": 0,
"stabilityText": "Deprecated: Use the WHATWG URL API instead.",
"modules": [
{
"textRaw": "Legacy `urlObject`",
"name": "legacy_`urlobject`",
"meta": {
"changes": [
{
"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."
}
]
},
"desc": "The legacy urlObject
(require('url').Url
) is created and returned by the\nurl.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
.
url.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
.If either of the following conditions is true, then the literal string //
\nwill be appended to result
:
urlObject.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 @
.If the urlObject.host
property is undefined
then:
urlObject.hostname
is a string, it is appended to result
.urlObject.hostname
is not undefined
and is not a string,\nan Error
is thrown.If the urlObject.port
property value is truthy, and urlObject.hostname
\nis not undefined
:
:
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
.If the urlObject.pathname
property is a string that is not an empty string:
urlObject.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
.Otherwise, if urlObject.search
is a string:
urlObject.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.If the urlObject.hash
property is a string:
urlObject.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.
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 HREF.
const url = require('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
\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, U+0022, U+003C, U+003E, and U+0060.
\nThe path percent-encode set includes the C0 control percent-encode set\nand code points U+0020, U+0022, U+0023, U+003C, U+003E, U+003F, U+0060,\nU+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, U+005B, U+005C, U+005D,\nU+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 hostname, the hostname is encoded\nusing the Punycode algorithm. Note, however, that a hostname 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"
},
{
"textRaw": "Util",
"name": "util",
"introduced_in": "v0.10.0",
"stability": 2,
"stabilityText": "Stable",
"desc": "The util
module is primarily designed to support the needs of Node.js' own\ninternal APIs. However, many of the utilities are useful for application and\nmodule developers as well. It can be accessed using:
const util = require('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('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 && err.hasOwnProperty('reason') && err.reason === null; // true\n});\n
"
},
{
"textRaw": "util.debuglog(section)",
"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."
}
]
}
],
"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('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('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 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('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('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.
The first argument is a string containing zero or more placeholder tokens.\nEach placeholder token is replaced with the converted value from the\ncorresponding argument. Supported placeholders are:
\n%s
- String
.%d
- Number
(integer or floating point value) or BigInt
.%i
- Integer or BigInt
.%f
- Floating point value.%j
- JSON. Replaced with the string '[Circular]'
if the argument\ncontains circular references.%o
- Object
. A string representation of an object\nwith generic JavaScript object formatting.\nSimilar 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.%%
- single percent sign ('%'
). This does not consume an argument.If the placeholder does not have a corresponding argument, the placeholder is\nnot replaced.
\nutil.format('%s:%s', 'foo');\n// Returns: 'foo:%s'\n
\nIf there are more arguments passed to the util.format()
method than the number\nof placeholders, the extra arguments are coerced into strings then concatenated\nto the returned string, each delimited by a space. Excessive arguments whose\ntypeof
is 'object'
or 'symbol'
(except null
) will be transformed by\nutil.inspect()
.
util.format('%s:%s', 'foo', 'bar', 'baz'); // 'foo:bar baz'\n
\nIf the first argument is not a string then util.format()
returns\na string that is the concatenation of all arguments separated by spaces.\nEach argument is converted to a string using util.inspect()
.
util.format(1, 2, 3); // '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'); // '%% %s'\n
\nPlease note that util.format()
is a synchronous method that is mainly\nintended as a debugging tool. Some input values can have a significant\nperformance overhead that can block the event loop. Use this function\nwith 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.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."
}
]
},
"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
.
As an additional convenience, superConstructor
will be accessible\nthrough the constructor.super_
property.
const util = require('util');\nconst EventEmitter = require('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: \"${data}\"`);\n});\nstream.write('It works!'); // Received data: \"It works!\"\n
\nES6 example using class
and extends
:
const EventEmitter = require('events');\n\nclass MyStream extends EventEmitter {\n write(data) {\n this.emit('data', data);\n }\n}\n\nconst stream = new MyStream();\n\nstream.on('data', (data) => {\n console.log(`Received data: \"${data}\"`);\n});\nstream.write('With ES6');\n
"
},
{
"textRaw": "util.inspect(object[, options])",
"type": "method",
"name": "inspect",
"meta": {
"added": [
"v0.3.0"
],
"changes": [
{
"version": "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": "v10.12.0",
"pr-url": "https://github.com/nodejs/node/pull/22788",
"description": "The `sorted` option is supported now."
},
{
"version": "v11.0.0",
"pr-url": "https://github.com/nodejs/node/pull/22756",
"description": "The inspection output is now limited to about 128 MB. Data above that size will not be fully inspected."
},
{
"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 passed object",
"name": "return",
"type": "string",
"desc": "The representation of passed 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`, the `object`'s non-enumerable symbols and properties will be included in the formatted result as well as [`WeakMap`][] and [`WeakSet`][] entries. **Default:** `false`.",
"name": "showHidden",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, the `object`'s non-enumerable symbols and properties will be included in the formatted result as well as [`WeakMap`][] and [`WeakSet`][] entries."
},
{
"textRaw": "`depth` {number} Specifies the number of times to recurse while formatting the `object`. This is useful for inspecting large complicated objects. To make it 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 the `object`. This is useful for inspecting large complicated objects. To make it recurse up to the maximum call stack size pass `Infinity` or `null`."
},
{
"textRaw": "`colors` {boolean} If `true`, the output will be 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 will be styled with ANSI color codes. Colors are customizable, see [Customizing `util.inspect` colors][]."
},
{
"textRaw": "`customInspect` {boolean} If `false`, then `[util.inspect.custom](depth, opts)` functions will not be called. **Default:** `true`.",
"name": "customInspect",
"type": "boolean",
"default": "`true`",
"desc": "If `false`, then `[util.inspect.custom](depth, opts)` functions will not be called."
},
{
"textRaw": "`showProxy` {boolean} If `true`, then objects and functions that are `Proxy` objects will be introspected to show their `target` and `handler` objects. **Default:** `false`.",
"name": "showProxy",
"type": "boolean",
"default": "`false`",
"desc": "If `true`, then objects and functions that are `Proxy` objects will be introspected to show their `target` and `handler` objects."
},
{
"textRaw": "`maxArrayLength` {integer} Specifies the maximum number of `Array`, [`TypedArray`][], [`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`][], [`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": "`breakLength` {integer} The length at which an object's keys are split across multiple lines. Set to `Infinity` to format an object as a single line. **Default:** `60` for legacy compatibility.",
"name": "breakLength",
"type": "integer",
"default": "`60` for legacy compatibility",
"desc": "The length at which an object's keys are split across multiple lines. Set to `Infinity` to format an object as a single line."
},
{
"textRaw": "`compact` {boolean} Setting this to `false` changes the default indentation to use a line break for each object key instead of lining up multiple properties in one line. It will also break text that is above the `breakLength` size into smaller and better readable chunks and indents objects the same as arrays. Note that no text will be reduced below 16 characters, no matter the `breakLength` size. For more information, see the example below. **Default:** `true`.",
"name": "compact",
"type": "boolean",
"default": "`true`",
"desc": "Setting this to `false` changes the default indentation to use a line break for each object key instead of lining up multiple properties in one line. It will also break text that is above the `breakLength` size into smaller and better readable chunks and indents objects the same as arrays. Note that no text will be reduced below 16 characters, no matter the `breakLength` size. 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 will be sorted in the returned string. If set to `true` the [default sort][] is going to be 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 will be sorted in the returned string. If set to `true` the [default sort][] is going to be used. If set to a function, it is used as a [compare function][]."
},
{
"textRaw": "`getters` {boolean|string} If set to `true`, getters are going to be inspected as well. If set to `'get'` only getters without setter are going to be inspected. If set to `'set'` only getters having a corresponding setter are going to be 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 going to be inspected as well. If set to `'get'` only getters without setter are going to be inspected. If set to `'set'` only getters having a corresponding setter are going to be inspected. This might cause side effects depending on the getter function."
}
],
"optional": true
}
]
}
],
"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 certain aspects of the formatted string.\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
\nThe following example inspects all properties of the util
object:
const util = require('util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));\n
\nThe following example highlights the difference with the compact
option:
const util = require('util');\n\nconst o = {\n a: [1, 2, [[\n 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do ' +\n 'eiusmod tempor 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// This will print\n\n// { a:\n// [ 1,\n// 2,\n// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line\n// 'test',\n// 'foo' ] ],\n// 4 ],\n// b: Map { 'za' => 1, 'zb' => 'test' } }\n\n// Setting `compact` to false changes the output to be more reader friendly.\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, consectetur ' +\n// 'adipiscing elit, sed do eiusmod tempor ' +\n// 'incididunt ut labore et dolore magna ' +\n// 'aliqua.,\n// 'test',\n// 'foo'\n// ]\n// ],\n// 4\n// ],\n// b: Map {\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// Reducing the `breakLength` will split the \"Lorem ipsum\" text in smaller\n// chunks.\n
\nUsing the showHidden
option allows to inspect WeakMap
and WeakSet
\nentries. If there are more entries than maxArrayLength
, there is no guarantee\nwhich entries are displayed. That means retrieving the same WeakSet
\nentries twice might actually result in a different output. Besides this any item\nmight be collected at any point of time by the garbage collector if there is no\nstrong reference left to that object. Therefore there is no guarantee to get a\nreliable output.
const { inspect } = require('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 makes sure the output is identical, no matter of the\nproperties insertion order:
const { inspect } = require('util');\nconst assert = require('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 { 1, 2, 3 } }\nconsole.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));\n// { c: Set { 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
\nPlease note that util.inspect()
is a synchronous method that is mainly\nintended as a debugging tool. Its maximum output length is limited to\napproximately 128 MB and input values that result in output bigger than that\nwill not be inspected fully. Such values can have a significant performance\noverhead that can block the event loop for a significant amount of time.
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 certain aspects of the formatted string.\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
\nThe following example inspects all properties of the util
object:
const util = require('util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));\n
\nThe following example highlights the difference with the compact
option:
const util = require('util');\n\nconst o = {\n a: [1, 2, [[\n 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do ' +\n 'eiusmod tempor 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// This will print\n\n// { a:\n// [ 1,\n// 2,\n// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line\n// 'test',\n// 'foo' ] ],\n// 4 ],\n// b: Map { 'za' => 1, 'zb' => 'test' } }\n\n// Setting `compact` to false changes the output to be more reader friendly.\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, consectetur ' +\n// 'adipiscing elit, sed do eiusmod tempor ' +\n// 'incididunt ut labore et dolore magna ' +\n// 'aliqua.,\n// 'test',\n// 'foo'\n// ]\n// ],\n// 4\n// ],\n// b: Map {\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// Reducing the `breakLength` will split the \"Lorem ipsum\" text in smaller\n// chunks.\n
\nUsing the showHidden
option allows to inspect WeakMap
and WeakSet
\nentries. If there are more entries than maxArrayLength
, there is no guarantee\nwhich entries are displayed. That means retrieving the same WeakSet
\nentries twice might actually result in a different output. Besides this any item\nmight be collected at any point of time by the garbage collector if there is no\nstrong reference left to that object. Therefore there is no guarantee to get a\nreliable output.
const { inspect } = require('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 makes sure the output is identical, no matter of the\nproperties insertion order:
const { inspect } = require('util');\nconst assert = require('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 { 1, 2, 3 } }\nconsole.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));\n// { c: Set { 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
\nPlease note that util.inspect()
is a synchronous method that is mainly\nintended as a debugging tool. Its maximum output length is limited to\napproximately 128 MB and input values that result in output bigger than that\nwill not be inspected fully. Such values can have a significant performance\noverhead that can block the event loop for a significant amount of time.
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:
\nnumber
- yellow
boolean
- yellow
string
- green
date
- magenta
regexp
- red
null
- bold
undefined
- grey
special
- cyan
(only applied to functions at this time)name
- (no styling)The predefined color codes are: white
, grey
, black
, blue
, cyan
,\ngreen
, magenta
, red
and yellow
. There are also bold
, italic
,\nunderline
and inverse
codes.
Color styling uses ANSI control codes that may not be supported on all\nterminals.
" }, { "textRaw": "Custom inspection functions on Objects", "name": "Custom inspection functions on Objects", "type": "misc", "desc": "Objects may also define their own\n[util.inspect.custom](depth, opts)
function,\nwhich util.inspect()
will invoke and use the result of when inspecting\nthe object:
const util = require('util');\n\nclass Box {\n constructor(value) {\n this.value = value;\n }\n\n [util.inspect.custom](depth, options) {\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 = util.inspect(this.value, newOptions)\n .replace(/\\n/g, `\\n${padding}`);\n return `${options.stylize('Box', 'special')}< ${inner} >`;\n }\n}\n\nconst box = new Box(true);\n\nutil.inspect(box);\n// Returns: \"Box< true >\"\n
\nCustom [util.inspect.custom](depth, opts)
functions typically return a string\nbut may return a value of any type that will be formatted accordingly by\nutil.inspect()
.
const util = require('util');\n\nconst obj = { foo: 'this will not show up in the inspect() output' };\nobj[util.inspect.custom] = (depth) => {\n return { bar: 'baz' };\n};\n\nutil.inspect(obj);\n// Returns: \"{ bar: 'baz' }\"\n
"
}
],
"properties": [
{
"textRaw": "`custom` {symbol} that can be used to declare custom inspect functions.",
"type": "symbol",
"name": "custom",
"meta": {
"added": [
"v6.6.0"
],
"changes": [
{
"version": "v10.12.0",
"pr-url": "https://github.com/nodejs/node/pull/20857",
"description": "This is now defined as a shared symbol."
}
]
},
"desc": "In addition to being accessible through util.inspect.custom
, this\nsymbol is registered globally and can be\naccessed in any environment as Symbol.for('nodejs.util.inspect.custom')
.
const inspect = Symbol.for('nodejs.util.inspect.custom');\n\nclass Password {\n constructor(value) {\n this.value = value;\n }\n\n toString() {\n return 'xxxxxxxx';\n }\n\n [inspect]() {\n return `Password <${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('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.
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('util');\nconst fs = require('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('util');\nconst fs = require('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
\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 the util.promisify.custom
symbol one can override the return value of\nutil.promisify()
:
const util = require('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.
An implementation of the WHATWG Encoding Standard TextDecoder
API.
const decoder = new TextDecoder('shift_jis');\nlet string = '';\nlet buffer;\nwhile (buffer = getNextChunkSomehow()) {\n string += decoder.decode(buffer, { stream: true });\n}\nstring += decoder.decode(); // end-of-stream\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.\nWhile a very basic set of encodings is supported even on Node.js builds without\nICU enabled, support for some encodings is provided only when Node.js is built\nwith ICU and using the full ICU data (see Internationalization).
", "modules": [ { "textRaw": "Encodings Supported Without ICU", "name": "encodings_supported_without_icu", "desc": "Encoding | \nAliases | \n
---|---|
'utf-8' | \n'unicode-1-1-utf-8' , 'utf8' | \n
'utf-16le' | \n'utf-16' | \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
---|---|
'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
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 an 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.
The encoding supported by the TextEncoder
instance. Always set to 'utf-8'
.
util.types
provides a number of type checks for different kinds of built-in\nobjects. Unlike instanceof
or Object.prototype.toString.call(value)
,\nthese checks do not inspect properties of the object that are accessible from\nJavaScript (like their prototype), and usually have the overhead of\ncalling 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.
", "methods": [ { "textRaw": "util.types.isAnyArrayBuffer(value)", "type": "method", "name": "isAnyArrayBuffer", "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
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.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.\nNote that this 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.isDataView(value)",
"type": "method",
"name": "isDataView",
"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 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.
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.\nNote that this 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.\nNote that this 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.isMap(value)",
"type": "method",
"name": "isMap",
"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 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 is an instance of a built-in Error
type.
util.types.isNativeError(new Error()); // Returns true\nutil.types.isNativeError(new TypeError()); // Returns true\nutil.types.isNativeError(new RangeError()); // Returns 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
"
},
{
"textRaw": "util.types.isWebAssemblyCompiledModule(value)",
"type": "method",
"name": "isWebAssemblyCompiledModule",
"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 WebAssembly.Module
instance.
const module = new WebAssembly.Module(wasmBuffer);\nutil.types.isWebAssemblyCompiledModule(module); // 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()
.
Deprecated predecessor of console.error
.
Deprecated predecessor of console.error
.
Alias for Array.isArray()
.
Returns true
if the given object
is an Array
. Otherwise, returns false
.
const util = require('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('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('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('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('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
\nNote that this 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('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('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('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\n`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('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('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:\nUse `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('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\n`(typeof value !== 'object' && typeof value !== 'function') || value === null`\ninstead.",
"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('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('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('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('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('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('util');\n\nutil.log('Timestamped message.');\n
"
},
{
"textRaw": "util.print([...strings])",
"type": "method",
"name": "print",
"meta": {
"added": [
"v0.3.0"
],
"deprecated": [
"v0.11.3"
],
"changes": []
},
"stability": 0,
"stabilityText": "Deprecated: Use [`console.log()`][] instead.",
"signatures": [
{
"params": [
{
"name": "...strings",
"optional": true
}
]
}
],
"desc": "Deprecated predecessor of console.log
.
Deprecated predecessor of console.log
.
The 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('v8');\n
\nThe APIs and implementation are subject to change at any time.
", "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.
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": "v7.2.0",
"pr-url": "https://github.com/nodejs/node/pull/8610",
"description": "Added `malloced_memory`, `peak_malloced_memory`, and `does_zap_garbage`."
},
{
"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 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>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 memory set) gets bigger\nbecause it continuously touches all heap pages and that makes them less likely\nto get swapped out by the operating system.
{\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}\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
. An unofficial, community-maintained list of options\nand their effects is available here.
Usage:
\n// Print GC events to stdout for one minute.\nconst v8 = require('v8');\nv8.setFlagsFromString('--trace_gc');\nsetTimeout(() => { v8.setFlagsFromString('--notrace_gc'); }, 60e3);\n
"
}
],
"modules": [
{
"textRaw": "Serialization API",
"name": "serialization_api",
"stability": 1,
"stabilityText": "Experimental",
"desc": "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).
\nThis API is under development, and changes (including incompatible\nchanges to the API or wire format) may occur until this warning is removed.
", "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.
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 havings 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 havings 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 vm
module provides APIs for compiling and running code within V8 Virtual\nMachine contexts. The vm
module is not a security mechanism. Do\nnot use it to run untrusted code. The term \"sandbox\" is used throughout these\ndocs simply to refer to a separate context, and does not confer any security\nguarantees.
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 sandboxed environment.\nThe sandboxed code uses a different V8 Context, meaning that\nit has a different global object than the rest of the code.
\nOne can provide the context by \"contextifying\" a sandbox\nobject. The sandboxed code treats any property in the sandbox like a\nglobal variable. Any changes to global variables caused by the sandboxed\ncode are reflected in the sandbox object.
\nconst vm = require('vm');\n\nconst x = 1;\n\nconst sandbox = { x: 2 };\nvm.createContext(sandbox); // Contextify the sandbox.\n\nconst code = 'x += 40; var y = 17;';\n// x and y are global variables in the sandboxed environment.\n// Initially, x has the value 2 because that is the value of sandbox.x.\nvm.runInContext(code, sandbox);\n\nconsole.log(sandbox.x); // 42\nconsole.log(sandbox.y); // 17\n\nconsole.log(x); // 1; y is not defined.\n
",
"classes": [
{
"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 a low-level interface for using\nECMAScript modules in VM contexts. It is the counterpart of the vm.Script
\nclass that closely mirrors Source Text Module Records as defined in the\nECMAScript specification.
Unlike vm.Script
however, every vm.SourceTextModule
object is bound to a\ncontext from its creation. Operations on vm.SourceTextModule
objects are\nintrinsically asynchronous, in contrast with the synchronous nature of\nvm.Script
objects. With the help of async functions, however, manipulating\nvm.SourceTextModule
objects is fairly straightforward.
Using a vm.SourceTextModule
object requires four distinct steps:\ncreation/parsing, linking, instantiation, and evaluation. These four steps are\nillustrated in the following example.
This implementation lies at a lower level than the ECMAScript Module\nloader. There is also currently no way to interact with the Loader, though\nsupport is planned.
\nconst vm = require('vm');\n\nconst contextifiedSandbox = vm.createContext({ secret: 42 });\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 `contextifiedSandbox` 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 `, { context: contextifiedSandbox });\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 // \"contextifiedSandbox\" when creating the context.\n export default secret;\n `, { context: referencingModule.context });\n\n // Using `contextifiedSandbox` 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 // Instantiate the top-level Module.\n //\n // Only the top-level Module needs to be explicitly instantiated; its\n // dependencies will be recursively instantiated by instantiate().\n\n bar.instantiate();\n\n // Step 4\n //\n // Evaluate the Module. The evaluate() method returns a Promise with a single\n // property \"result\" that contains the result of the very last statement\n // executed in the Module. In the case of `bar`, it is `s;`, which refers to\n // the default export of the `foo` module, the `secret` we set in the\n // beginning to 42.\n\n const { result } = await bar.evaluate();\n\n console.log(result);\n // Prints 42.\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\nSource Text Module Records in the 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 Source Text Module Records\nin the ECMAScript specification.
The current linking status of module
. It will be one of the following values:
'unlinked'
: module.link()
has not yet been called.'linking'
: module.link()
has been called, but not all Promises returned by\nthe linker function have been resolved yet.'linked'
: module.link()
has been called, and all its dependencies have\nbeen successfully linked.'errored'
: module.link()
has been called, but at least one of its\ndependencies failed to link, either because the callback returned a Promise
\nthat is rejected, or because the Module
the callback returned is invalid.The namespace object of the module. This is only available after instantiation\n(module.instantiate()
) 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'uninstantiated'
: The module is not instantiated. It may because of any of\nthe following reasons:
module.instantiate()
has been called on this module, but it failed for\nsome reason.This status does not convey any information regarding if module.link()
has\nbeen called. See module.linkingStatus
for that.
'instantiating'
: The module is currently being instantiated through a\nmodule.instantiate()
call on itself or a parent module.
'instantiated'
: The module has been instantiated successfully, but\nmodule.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\nSource Text Module Record's [[Status]]
field. 'errored'
corresponds to\n'evaluated'
in the specification, but with [[EvaluationError]]
set to a\nvalue that is not undefined
.
The URL of the current module, as set in the constructor.
" } ], "methods": [ { "textRaw": "module.evaluate([options])", "type": "method", "name": "evaluate", "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`timeout` {integer} Specifies the number of milliseconds to evaluate before terminating execution. If execution is interrupted, an [`Error`][] will be thrown. This value must be a strictly positive integer.", "name": "timeout", "type": "integer", "desc": "Specifies the number of milliseconds to evaluate before terminating execution. If execution is interrupted, an [`Error`][] will be thrown. This value must be a strictly positive integer." }, { "textRaw": "`breakOnSigint` {boolean} If `true`, the execution will be terminated when `SIGINT` (Ctrl+C) is received. Existing handlers for the event that have been attached via `process.on('SIGINT')` will be disabled during script execution, but will continue to work after that. If execution is interrupted, an [`Error`][] will be thrown.", "name": "breakOnSigint", "type": "boolean", "desc": "If `true`, the execution will be terminated when `SIGINT` (Ctrl+C) is received. Existing handlers for the event that have been attached via `process.on('SIGINT')` will be disabled during script execution, but will continue to work after that. If execution is interrupted, an [`Error`][] will be thrown." } ], "optional": true } ] } ], "desc": "Evaluate the module.
\nThis must be called after the module has been instantiated; otherwise it will\nthrow an error. It could be called also when the module has already been\nevaluated, in which case it will do one of the following two things:
\nundefined
if the initial evaluation ended in success (module.status
\nis 'evaluated'
)module.status
is 'errored'
)This method cannot be called while the module is being evaluated\n(module.status
is 'evaluating'
) to prevent infinite recursion.
Corresponds to the Evaluate() concrete method field of Source Text Module\nRecords in the ECMAScript specification.
" }, { "textRaw": "module.instantiate()", "type": "method", "name": "instantiate", "signatures": [ { "params": [] } ], "desc": "Instantiate the module. This must be called after linking has completed\n(linkingStatus
is 'linked'
); otherwise it will throw an error. It may also\nthrow an exception if one of the dependencies does not provide an export the\nparent module requires.
However, if this function succeeded, further calls to this function after the\ninitial instantiation will be no-ops, to be consistent with the ECMAScript\nspecification.
\nUnlike other methods operating on Module
, this function completes\nsynchronously and returns nothing.
Corresponds to the Instantiate() concrete method field of Source Text\nModule Records in the ECMAScript specification.
" }, { "textRaw": "module.link(linker)", "type": "method", "name": "link", "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`linker` {Function}", "name": "linker", "type": "Function" } ] } ], "desc": "Link module dependencies. This method must be called before instantiation, and\ncan only be called once per module.
\nTwo parameters will be passed to the linker
function:
specifier
The specifier of the requested module:
import foo from 'foo';\n// ^^^^^ the module specifier\n
\nreferencingModule
The Module
object link()
is called on.The 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
.linkingStatus
must not be 'errored'
.If the returned Module
's linkingStatus
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\ninstantiation 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.
" } ], "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": "`url` {string} URL used in module resolution and stack traces. **Default:** `'vm:module(i)'` where `i` is a context-specific ascending index.", "name": "url", "type": "string", "default": "`'vm:module(i)'` where `i` is a context-specific ascending index", "desc": "URL used in module resolution and 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." }, { "textRaw": "`lineOffset` {integer} Specifies the line number offset that is displayed in stack traces produced by this `Module`.", "name": "lineOffset", "type": "integer", "desc": "Specifies the line number offset that is displayed in stack traces produced by this `Module`." }, { "textRaw": "`columnOffset` {integer} Specifies the column number offset that is displayed in stack traces produced by this `Module`.", "name": "columnOffset", "type": "integer", "desc": "Specifies the 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`. This function has the signature `(meta, module)`, where `meta` is the `import.meta` object in the `Module`, and `module` is this `vm.SourceTextModule` object.", "name": "initializeImportMeta", "type": "Function", "desc": "Called during evaluation of this `Module` to initialize the `import.meta`. This function has the signature `(meta, module)`, where `meta` is the `import.meta` object in the `Module`, and `module` is this `vm.SourceTextModule` object." }, { "textRaw": "`importModuleDynamically` {Function} Called during evaluation of this module when `import()` is called. This function has the signature `(specifier, module)` where `specifier` is the specifier passed to `import()` and `module` is this `vm.SourceTextModule`. If this option is not specified, calls to `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][]. This method can return a [Module Namespace Object][], but returning a `vm.SourceTextModule` is recommended in order to take advantage of error tracking, and to avoid issues with namespaces that contain `then` function exports.", "name": "importModuleDynamically", "type": "Function", "desc": "Called during evaluation of this module when `import()` is called. This function has the signature `(specifier, module)` where `specifier` is the specifier passed to `import()` and `module` is this `vm.SourceTextModule`. If this option is not specified, calls to `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][]. This method can return a [Module Namespace Object][], but returning a `vm.SourceTextModule` is recommended in order to take advantage of error tracking, and to avoid issues with namespaces that contain `then` function exports." } ], "optional": true } ], "desc": "Creates a new ES Module
object.
Properties assigned to the import.meta
object that are objects may\nallow the Module
to access information outside the specified context
, if the\nobject is created in the top level context. Use vm.runInContext()
to create\nobjects in a specific context.
const vm = require('vm');\n\nconst contextifiedSandbox = vm.createContext({ secret: 42 });\n\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 sandbox.\n meta.prop = {};\n }\n });\n // Since module has no dependencies, the linker function will never be called.\n await module.link(() => {});\n module.instantiate();\n await 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('{}', contextifiedSandbox);\n})();\n
"
}
]
},
{
"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 sandboxes (or \"contexts\").
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.
const script = new vm.Script(`\nfunction add(a, b) {\n return a + b;\n}\n\nconst x = add(1, 2);\n`);\n\nconst cacheWithoutX = script.createCachedData();\n\nscript.runInThisContext();\n\nconst cacheWithX = script.createCachedData();\n
"
},
{
"textRaw": "script.runInContext(contextifiedSandbox[, 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": [
{
"params": [
{
"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."
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script.",
"name": "filename",
"type": "string",
"desc": "Specifies the filename used in stack traces produced by this script."
},
{
"textRaw": "`lineOffset` {number} Specifies the line number offset that is displayed in stack traces produced by this script.",
"name": "lineOffset",
"type": "number",
"desc": "Specifies the line number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`columnOffset` {number} Specifies the column number offset that is displayed in stack traces produced by this script.",
"name": "columnOffset",
"type": "number",
"desc": "Specifies the column number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`displayErrors` {boolean} When `true`, if an [`Error`][] error occurs while compiling the `code`, the line of code causing the error is attached to the stack trace.",
"name": "displayErrors",
"type": "boolean",
"desc": "When `true`, if an [`Error`][] 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`: if `true`, the execution will be terminated when `SIGINT` (Ctrl+C) is received. Existing handlers for the event that have been attached via `process.on('SIGINT')` will be disabled during script execution, but will continue to work after that. If execution is terminated, an [`Error`][] will be thrown.",
"name": "breakOnSigint",
"desc": "if `true`, the execution will be terminated when `SIGINT` (Ctrl+C) is received. Existing handlers for the event that have been attached via `process.on('SIGINT')` will be disabled during script execution, but will continue to work after that. If execution is terminated, an [`Error`][] will be thrown."
}
],
"optional": true
}
]
}
],
"desc": "Runs the compiled code contained by the vm.Script
object within the given\ncontextifiedSandbox
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 sandbox
object.
const util = require('util');\nconst vm = require('vm');\n\nconst sandbox = {\n animal: 'cat',\n count: 2\n};\n\nconst script = new vm.Script('count += 1; name = \"kitty\";');\n\nconst context = vm.createContext(sandbox);\nfor (let i = 0; i < 10; ++i) {\n script.runInContext(context);\n}\n\nconsole.log(util.inspect(sandbox));\n\n// { 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 sandbox
, runs the compiled code contained by\nthe vm.Script
object within the created sandbox, 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 sandbox
.
const util = require('util');\nconst vm = require('vm');\n\nconst script = new vm.Script('globalVar = \"set\"');\n\nconst sandboxes = [{}, {}, {}];\nsandboxes.forEach((sandbox) => {\n script.runInNewContext(sandbox);\n});\n\nconsole.log(util.inspect(sandboxes));\n\n// [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]\n
"
},
{
"textRaw": "script.runInThisContext([options])",
"type": "method",
"name": "runInThisContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": []
},
"signatures": [
{
"params": [
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script.",
"name": "filename",
"type": "string",
"desc": "Specifies the filename used in stack traces produced by this script."
},
{
"textRaw": "`lineOffset` {number} Specifies the line number offset that is displayed in stack traces produced by this script.",
"name": "lineOffset",
"type": "number",
"desc": "Specifies the line number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`columnOffset` {number} Specifies the column number offset that is displayed in stack traces produced by this script.",
"name": "columnOffset",
"type": "number",
"desc": "Specifies the column number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`displayErrors` {boolean} When `true`, if an [`Error`][] error occurs while compiling the `code`, the line of code causing the error is attached to the stack trace.",
"name": "displayErrors",
"type": "boolean",
"desc": "When `true`, if an [`Error`][] 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."
}
],
"optional": true
}
]
}
],
"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('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`",
"name": "options",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script.",
"name": "filename",
"type": "string",
"desc": "Specifies the filename used in stack traces produced by this script."
},
{
"textRaw": "`lineOffset` {number} Specifies the line number offset that is displayed in stack traces produced by this script.",
"name": "lineOffset",
"type": "number",
"desc": "Specifies the line number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`columnOffset` {number} Specifies the column number offset that is displayed in stack traces produced by this script.",
"name": "columnOffset",
"type": "number",
"desc": "Specifies the column number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`cachedData` {Buffer|TypedArray|DataView} Provides an optional `Buffer` or `TypedArray`, or `DataView` with V8's code cache data for the supplied source. When supplied, the `cachedDataRejected` value will be set to either `true` or `false` depending on acceptance of the data by V8.",
"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. When supplied, the `cachedDataRejected` value will be set to either `true` or `false` depending on acceptance of the data by V8."
},
{
"textRaw": "`produceCachedData` {boolean} When `true` and no `cachedData` is present, V8 will attempt to produce code cache data for `code`. Upon success, a `Buffer` with V8's code cache data will be produced and stored in the `cachedData` property of the returned `vm.Script` instance. The `cachedDataProduced` value will be set to either `true` or `false` depending on whether code cache data is produced successfully. This option is deprecated in favor of `script.createCachedData()`.",
"name": "produceCachedData",
"type": "boolean",
"desc": "When `true` and no `cachedData` is present, V8 will attempt to produce code cache data for `code`. Upon success, a `Buffer` with V8's code cache data will be produced and stored in the `cachedData` property of the returned `vm.Script` instance. The `cachedDataProduced` value will be set to either `true` or `false` depending on whether code cache data is produced successfully. This option is deprecated in favor of `script.createCachedData()`."
},
{
"textRaw": "`importModuleDynamically` {Function} Called during evaluation of this module when `import()` is called. This function has the signature `(specifier, module)` where `specifier` is the specifier passed to `import()` and `module` is this `vm.SourceTextModule`. If this option is not specified, calls to `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][]. This method can return a [Module Namespace Object][], but returning a `vm.SourceTextModule` is recommended in order to take advantage of error tracking, and to avoid issues with namespaces that contain `then` function exports.",
"name": "importModuleDynamically",
"type": "Function",
"desc": "Called during evaluation of this module when `import()` is called. This function has the signature `(specifier, module)` where `specifier` is the specifier passed to `import()` and `module` is this `vm.SourceTextModule`. If this option is not specified, calls to `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][]. This method can return a [Module Namespace Object][], but returning a `vm.SourceTextModule` is recommended in order to take advantage of error tracking, and to avoid issues with namespaces that contain `then` function exports."
}
]
}
],
"desc": "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.
Compiles the given code into the provided context/sandbox (if no context is\nsupplied, the current context is used), and returns it wrapped inside a\nfunction with the given params
.
If given a sandbox
object, the vm.createContext()
method will prepare\nthat sandbox so that it can be used in calls to\nvm.runInContext()
or script.runInContext()
. Inside such scripts,\nthe sandbox
object 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 util = require('util');\nconst vm = require('vm');\n\nglobal.globalVar = 3;\n\nconst sandbox = { globalVar: 1 };\nvm.createContext(sandbox);\n\nvm.runInContext('globalVar *= 2;', sandbox);\n\nconsole.log(util.inspect(sandbox)); // { globalVar: 2 }\n\nconsole.log(util.inspect(globalVar)); // 3\n
\nIf sandbox
is omitted (or passed explicitly as undefined
), a new, empty\ncontextified sandbox object will be returned.
The vm.createContext()
method is primarily useful for creating a single\nsandbox that can be used to run multiple scripts. For instance, if emulating a\nweb browser, the method can be used to create a single sandbox representing a\nwindow's global object, then run all <script>
tags together within the context\nof that sandbox.
The provided name
and origin
of the context are made visible through the\nInspector API.
Returns true
if the given sandbox
object has been contextified using\nvm.createContext()
.
The vm.runInContext()
method compiles code
, runs it within the context of\nthe contextifiedSandbox
, then returns the result. Running code does not have\naccess to the local scope. The contextifiedSandbox
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 util = require('util');\nconst vm = require('vm');\n\nconst sandbox = { globalVar: 1 };\nvm.createContext(sandbox);\n\nfor (let i = 0; i < 10; ++i) {\n vm.runInContext('globalVar *= 2;', sandbox);\n}\nconsole.log(util.inspect(sandbox));\n\n// { globalVar: 1024 }\n
"
},
{
"textRaw": "vm.runInNewContext(code[, sandbox[, options]])",
"type": "method",
"name": "runInNewContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": []
},
"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": "`sandbox` {Object} An object that will be [contextified][]. If `undefined`, a new object will be created.",
"name": "sandbox",
"type": "Object",
"desc": "An object that will be [contextified][]. If `undefined`, a new object will be created.",
"optional": true
},
{
"textRaw": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script.",
"name": "filename",
"type": "string",
"desc": "Specifies the filename used in stack traces produced by this script."
},
{
"textRaw": "`lineOffset` {number} Specifies the line number offset that is displayed in stack traces produced by this script.",
"name": "lineOffset",
"type": "number",
"desc": "Specifies the line number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`columnOffset` {number} Specifies the column number offset that is displayed in stack traces produced by this script.",
"name": "columnOffset",
"type": "number",
"desc": "Specifies the column number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`displayErrors` {boolean} When `true`, if an [`Error`][] error occurs while compiling the `code`, the line of code causing the error is attached to the stack trace.",
"name": "displayErrors",
"type": "boolean",
"desc": "When `true`, if an [`Error`][] 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": "`contextName` {string} Human-readable name of the newly created context. **Default:** `'VM Context i'`, where `i` is an ascending numerical index of the created context.",
"name": "contextName",
"type": "string",
"default": "`'VM Context i'`, where `i` is an ascending numerical index of the created context",
"desc": "Human-readable name of the newly created context."
},
{
"textRaw": "`contextOrigin` {string} [Origin][origin] corresponding to the newly created context for display purposes. The origin should be formatted like a URL, but with only the scheme, host, and port (if necessary), like the value of the [`url.origin`][] property of a [`URL`][] object. Most notably, this string should omit the trailing slash, as that denotes a path. **Default:** `''`.",
"name": "contextOrigin",
"type": "string",
"default": "`''`",
"desc": "[Origin][origin] corresponding to the newly created context for display purposes. The origin should be formatted like a URL, but with only the scheme, host, and port (if necessary), like the value of the [`url.origin`][] property of a [`URL`][] object. Most notably, this string should omit the trailing slash, as that denotes a path."
}
],
"optional": true
}
]
}
],
"desc": "The vm.runInNewContext()
first contextifies the given sandbox
object (or\ncreates a new sandbox
if passed as undefined
), compiles the code
, runs it\nwithin the context of 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 sandbox
.
const util = require('util');\nconst vm = require('vm');\n\nconst sandbox = {\n animal: 'cat',\n count: 2\n};\n\nvm.runInNewContext('count += 1; name = \"kitty\"', sandbox);\nconsole.log(util.inspect(sandbox));\n\n// { animal: 'cat', count: 3, name: 'kitty' }\n
"
},
{
"textRaw": "vm.runInThisContext(code[, options])",
"type": "method",
"name": "runInThisContext",
"meta": {
"added": [
"v0.3.1"
],
"changes": []
},
"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": "`options` {Object|string}",
"name": "options",
"type": "Object|string",
"options": [
{
"textRaw": "`filename` {string} Specifies the filename used in stack traces produced by this script.",
"name": "filename",
"type": "string",
"desc": "Specifies the filename used in stack traces produced by this script."
},
{
"textRaw": "`lineOffset` {number} Specifies the line number offset that is displayed in stack traces produced by this script.",
"name": "lineOffset",
"type": "number",
"desc": "Specifies the line number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`columnOffset` {number} Specifies the column number offset that is displayed in stack traces produced by this script.",
"name": "columnOffset",
"type": "number",
"desc": "Specifies the column number offset that is displayed in stack traces produced by this script."
},
{
"textRaw": "`displayErrors` {boolean} When `true`, if an [`Error`][] error occurs while compiling the `code`, the line of code causing the error is attached to the stack trace.",
"name": "displayErrors",
"type": "boolean",
"desc": "When `true`, if an [`Error`][] 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."
}
],
"optional": true
}
]
}
],
"desc": "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('vm');\nlet localVar = 'initial value';\n\nconst vmResult = vm.runInThisContext('localVar = \"vm\";');\nconsole.log('vmResult:', vmResult);\nconsole.log('localVar:', localVar);\n\nconst evalResult = eval('localVar = \"eval\";');\nconsole.log('evalResult:', evalResult);\nconsole.log('localVar:', localVar);\n\n// vmResult: 'vm', localVar: 'initial value'\n// 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 http
module the code passed to\nthe context must either call require('http')
on its own, or have a reference\nto the http
module passed to it. For instance:
'use strict';\nconst vm = require('vm');\n\nconst code = `\n((require) => {\n const http = require('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.
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 sandbox
object that is\npassed in (or a newly created object if sandbox
is undefined
) is associated\ninternally with a new instance of a V8 Context. This V8 Context provides the\ncode
run using the vm
module's methods with an isolated global environment\nwithin which it can operate. The process of creating the V8 Context and\nassociating it with the sandbox
object is what this document refers to as\n\"contextifying\" the sandbox
.
Because of the internal mechanics of how the process.nextTick()
queue and\nthe microtask queue that underlies Promises are implemented within V8 and\nNode.js, it is possible for code running within a context to \"escape\" the\ntimeout
set using vm.runInContext()
, vm.runInNewContext()
, and\nvm.runInThisContext()
.
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('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 }\n);\n
\nThis issue also occurs when the loop()
call is scheduled using\nthe process.nextTick()
and queueMicrotask()
functions.
This issue occurs because all contexts share the same microtask and nextTick\nqueues.
", "type": "module", "displayName": "Timeout limitations when using process.nextTick(), Promises, and queueMicrotask()" } ], "type": "module", "displayName": "vm" }, { "textRaw": "Worker Threads", "name": "worker_threads", "introduced_in": "v10.5.0", "stability": 1, "stabilityText": "Experimental", "desc": "The worker
module provides a way to create multiple environments running\non independent threads, and to create message channels between them. It\ncan be accessed using the --experimental-worker
flag and:
const worker = require('worker_threads');\n
\nWorkers are useful for performing CPU-intensive JavaScript operations; do not\nuse them for I/O, since Node.js’s built-in mechanisms for performing operations\nasynchronously already treat it more efficiently than Worker threads can.
\nWorkers, unlike child processes or when using the cluster
module, can also\nshare memory efficiently by transferring ArrayBuffer
instances or sharing\nSharedArrayBuffer
instances between them.
const {\n Worker, isMainThread, parentPort, workerData\n} = require('worker_threads');\n\nif (isMainThread) {\n module.exports = async 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
\nNote that this example spawns a Worker thread for each parse
call.\nIn practice, it is strongly recommended to use a pool of Workers for these\nkinds of tasks, since the overhead of creating Workers would likely exceed the\nbenefit of handing the work off to it.
Is true
if this code is not running inside of a Worker
thread.
If this thread was spawned as a Worker
, this will be a MessagePort
\nallowing communication with the parent thread. Messages sent using\nparentPort.postMessage()
will be available in the parent thread\nusing worker.on('message')
, and messages sent from the parent thread\nusing worker.postMessage()
will be available in this thread using\nparentPort.on('message')
.
An integer identifier for the current thread. On the corresponding worker object\n(if there is any), it is available as worker.threadId
.
An arbitrary JavaScript value that contains a clone of the data passed\nto this thread’s Worker
constructor.
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('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": []
},
"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.
With the exception of MessagePort
s being EventEmitter
s rather\nthan EventTarget
s, this implementation matches browser MessagePort
s.
The 'close'
event is emitted once either side of the channel has been\ndisconnected.
The 'message'
event is emitted for any incoming message, containing the cloned\ninput of port.postMessage()
.
Listeners on this event will receive a clone of the value
parameter as passed\nto postMessage()
and no further arguments.
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
.
Sends a JavaScript value to the receiving side of this channel.\nvalue
will be transferred in a way which is compatible with\nthe HTML structured clone algorithm. In particular, it may contain circular\nreferences and objects like typed arrays that the JSON
API is not able\nto stringify.
transferList
may be a list of ArrayBuffer
and MessagePort
objects.\nAfter transferring, they will not be 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 will be 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.
Because the object cloning uses the 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.
The message object will be 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 v8
module.
Opposite of unref()
. Calling ref()
on a previously unref()
ed port will\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 will have no effect.
If listeners are attached or removed using .on('message')
, the port will\nbe 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 will be called automatically once 'message'
\nlisteners are attached.
Calling unref()
on a port will allow 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 will have no effect.
If listeners are attached or removed using .on('message')
, the port will\nbe ref()
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
\nmay be redirected by the parent thread.require('worker_threads').isMainThread
property is set to false
.require('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 read-only reference to the environment variables.process.title
cannot be modified.process.on('...')
.worker.terminate()
\nbeing invoked.trace_events
module is not supported.Currently, the following differences also exist until they are addressed:
\ninspector
module is not available yet.Creating Worker
instances inside of other Worker
s is possible.
Like Web Workers and the cluster
module, two-way communication can be\nachieved through inter-thread message passing. Internally, a Worker
has a\nbuilt-in pair of MessagePort
s that are already associated with each other\nwhen the Worker
is created. While the MessagePort
object on the parent side\nis 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('assert');\nconst {\n Worker, MessageChannel, MessagePort, isMainThread, parentPort\n} = require('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 will be terminated.
The 'exit'
event is emitted once the worker has stopped. If the worker\nexited by calling process.exit()
, the exitCode
parameter will be the\npassed exit code. If the worker was terminated, the exitCode
parameter will\nbe 1
.
The 'message'
event is emitted when the worker thread has invoked\nrequire('worker_threads').postMessage()
. See the port.on('message')
\nevent for more details.
The 'online'
event is emitted when the worker thread has started executing\nJavaScript code.
Send a message to the worker that will be received via\nrequire('worker_threads').parentPort.on('message')
.\nSee port.postMessage()
for more details.
Opposite of unref()
, calling ref()
on a previously unref()
ed worker will\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 will have\nno effect.
Stop all JavaScript execution in the worker thread as soon as possible.\ncallback
is an optional function that is invoked once this operation is known\nto have completed.
Warning: Currently, not all code in the internals of Node.js is prepared to\nexpect termination at arbitrary points in time and may crash if it encounters\nthat condition. Consequently, only call .terminate()
if it is known that the\nWorker thread is not accessing Node.js core modules other than what is exposed\nin the worker
module.
Calling unref()
on a worker will allow 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 will have no effect.
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 will be 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 will be 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('worker_threads').threadId
.
The zlib
module provides compression functionality implemented using Gzip and\nDeflate/Inflate. It can be accessed using:
const zlib = require('zlib');\n
\nCompressing or decompressing a stream (such as a file) can be accomplished by\npiping the source stream data through a zlib
stream into a destination stream:
const gzip = zlib.createGzip();\nconst fs = require('fs');\nconst inp = fs.createReadStream('input.txt');\nconst out = fs.createWriteStream('input.txt.gz');\n\ninp.pipe(gzip).pipe(out);\n
\nIt is also possible to compress or decompress data in a single step:
\nconst input = '.................................';\nzlib.deflate(input, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString('base64'));\n } else {\n // handle error\n }\n});\n\nconst buffer = Buffer.from('eJzT0yMAAGTvBe8=', 'base64');\nzlib.unzip(buffer, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString());\n } else {\n // handle error\n }\n});\n
",
"modules": [
{
"textRaw": "Threadpool Usage",
"name": "threadpool_usage",
"desc": "Note that all zlib APIs except those that are explicitly synchronous use libuv's\nthreadpool. This can lead to surprising effects in some applications, such as\nsubpar performance (which can be mitigated by adjusting the pool size)\nand/or unrecoverable and catastrophic memory fragmentation.
", "type": "module", "displayName": "Threadpool Usage" }, { "textRaw": "Compressing HTTP requests and responses", "name": "compressing_http_requests_and_responses", "desc": "The zlib
module can be used to implement support for the gzip
and deflate
\ncontent-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('zlib');\nconst http = require('http');\nconst fs = require('fs');\nconst request = http.get({ host: 'example.com',\n path: '/',\n port: 80,\n headers: { 'Accept-Encoding': 'gzip,deflate' } });\nrequest.on('response', (response) => {\n const output = fs.createWriteStream('example.com_index.html');\n\n switch (response.headers['content-encoding']) {\n // or, just use zlib.createUnzip() to handle both cases\n case 'gzip':\n response.pipe(zlib.createGunzip()).pipe(output);\n break;\n case 'deflate':\n response.pipe(zlib.createInflate()).pipe(output);\n break;\n default:\n response.pipe(output);\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('zlib');\nconst http = require('http');\nconst fs = require('fs');\nhttp.createServer((request, response) => {\n const raw = fs.createReadStream('index.html');\n let acceptEncoding = request.headers['accept-encoding'];\n if (!acceptEncoding) {\n acceptEncoding = '';\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 raw.pipe(zlib.createDeflate()).pipe(response);\n } else if (/\\bgzip\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'gzip' });\n raw.pipe(zlib.createGzip()).pipe(response);\n } else {\n response.writeHead(200, {});\n raw.pipe(response);\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 { finishFlush: zlib.constants.Z_SYNC_FLUSH },\n (err, buffer) => {\n if (!err) {\n console.log(buffer.toString());\n } else {\n // handle error\n }\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('zlib');\nconst http = require('http');\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 output.pipe(response);\n\n 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",
"desc": "From zlib/zconf.h
, modified to Node.js's 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.
All of the constants defined in zlib.h
are also defined on\nrequire('zlib').constants
. In the normal course of operations, it will not be\nnecessary to use these constants. They are documented so that their presence is\nnot surprising. This section is taken almost directly from the\nzlib documentation. See https://zlib.net/manual.html#Constants for more\ndetails.
Previously, the constants were available directly from require('zlib')
, for\ninstance zlib.Z_NO_FLUSH
. Accessing the constants directly from the module is\ncurrently 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
Each class takes an options
object. All options are optional.
Note that 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
.)See the description of deflateInit2
and inflateInit2
at\nhttps://zlib.net/manual.html#Advanced for more information on these.
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 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 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.Zlib", "type": "class", "name": "zlib.Zlib", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Not exported by the zlib
module. It is documented here because it is the base\nclass of the compressor/decompressor classes.
This class inherits from stream.Transform
, allowing zlib
objects to be\nused 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`", "name": "kind", "default": "`zlib.constants.Z_FULL_FLUSH`", "optional": true }, { "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.
Dynamically 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.createDeflate([options])", "type": "method", "name": "createDeflate", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`options` {zlib options}", "name": "options", "type": "zlib options", "optional": true } ] } ], "desc": "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.
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 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.
For crypto only, Error
objects will include the OpenSSL error stack in a\nseparate property called opensslErrorStack
if it is available when the error\nis thrown.
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 an end user. For instance:
function MyError() {\n Error.captureStackTrace(this, MyError);\n}\n\n// Without passing MyError to captureStackTrace, the MyError\n// frame would show up in the .stack property. By passing\n// the constructor, we omit that frame, and retain all frames below it.\nnew MyError().stack;\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": "`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, or its 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.
System-level errors are generated as augmented Error
instances, which are\ndetailed here.
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 message.toString()
. 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.
A subclass of Error
that indicates the failure of an assertion. For details,\nsee Class: assert.AssertionError
.
A subclass of Error
that indicates that a provided argument was not within the\nset or range of acceptable values for a function; whether that is a numeric\nrange, or outside the set of options for a given function parameter.
require('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.
A subclass of Error
that indicates that an attempt is being made to access a\nvariable that is not defined. Such errors commonly indicate typos in code, or\nan otherwise broken program.
While 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 should always be considered a bug in the code\nor its dependencies.
A subclass of Error
that indicates that a program is not valid JavaScript.\nThese errors may only be generated and propagated as a result of code\nevaluation. Code evaluation may happen as a result of eval
, Function
,\nrequire
, or vm. These errors are almost always indicative of a broken\nprogram.
try {\n require('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.
A subclass of Error
that indicates that a provided argument is not an\nallowable type. For example, passing a function to a parameter which expects a\nstring would be considered a TypeError
.
require('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.
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.
In browsers, the top-level scope is the global scope. This means that\nwithin the browser var something
will define a new global variable. In\nNode.js this is different. The top-level scope is not the global scope;\nvar something
inside a Node.js module will be local to that module.
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(url);\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(url, 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 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.
" }, { "textRaw": "Process", "name": "Process", "introduced_in": "v0.10.0", "type": "global", "desc": "The process
object is a global
that provides information about, and control\nover, the current Node.js process. As a global, it is always available to\nNode.js applications without using require()
.
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.
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.
process.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:
process.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.
" }, { "textRaw": "Event: 'multipleResolves'", "type": "event", "name": "multipleResolves", "meta": { "added": [ "v10.12.0" ], "changes": [] }, "params": [ { "textRaw": "`type` {string} The error type. One of `'resolve'` or `'reject'`.", "name": "type", "type": "string", "desc": "The error type. One of `'resolve'` or `'reject'`." }, { "textRaw": "`promise` {Promise} The promise that resolved or rejected more than once.", "name": "promise", "type": "Promise", "desc": "The promise that resolved or rejected more than once." }, { "textRaw": "`value` {any} The value with which the promise was either resolved or rejected after the original resolve.", "name": "value", "type": "any", "desc": "The value with which the promise was either resolved or rejected after the original resolve." } ], "desc": "The 'multipleResolves'
event is emitted whenever a Promise
has been either:
This is useful for tracking errors in an application while using the promise\nconstructor. Otherwise such mistakes are silently swallowed due to being in a\ndead zone.
\nIt is recommended to end the process on such errors, since the process could be\nin an undefined state. While using the promise constructor make sure that it is\nguaranteed to trigger the resolve()
or reject()
functions exactly once per\ncall and never call both functions in the same call.
process.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.
const 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.
The listener function is called with the Error
object passed as the only\nargument.
process.on('uncaughtException', (err) => {\n fs.writeSync(1, `Caught exception: ${err}\\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
",
"modules": [
{
"textRaw": "Warning: Using `'uncaughtException'` correctly",
"name": "warning:_using_`'uncaughtexception'`_correctly",
"desc": "Note that '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 of the power cord when upgrading a computer — nine out of ten\ntimes nothing happens - but the 10th 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 '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.
The listener function is called with the following arguments:
\nreason
<Error> | <any> The object with which the promise was rejected\n(typically an Error
object).p
the Promise
that was rejected.process.on('unhandledRejection', (reason, p) => {\n console.log('Unhandled Rejection at:', p, '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:
function 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. Alternatively, the 'rejectionHandled'
event may be used.
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.
\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.
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.
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.
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).
// 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). It is not\ngenerated when terminal raw mode is enabled.'SIGBREAK'
is delivered on Windows when <Ctrl>+<Break>
is pressed, on\nnon-Windows platforms it can be listened on, but there is no way to send or\ngenerate 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\n artificially using kill(2)
, inherently leave the process in a state from\n which it is not safe to attempt to call JS listeners. Doing so might lead to\n the process hanging in an endless loop, since listeners attached using\n process.on()
are called asynchronously and therefore unable to correct the\nunderlying problem.Windows does not support sending signals, but Node.js offers some emulation\nwith process.kill()
, and subprocess.kill()
. Sending signal 0
can\nbe used to test for the existence of a process. Sending SIGINT
, SIGTERM
,\nand SIGKILL
cause the unconditional termination of the target 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 Node.js's 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 Node.js's 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 Node.js's 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.>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).
console.log(`Starting directory: ${process.cwd()}`);\ntry {\n process.chdir('/tmp');\n console.log(`New directory: ${process.cwd()}`);\n} catch (err) {\n console.error(`chdir: ${err}`);\n}\n
\nThis feature is not available in Worker
threads.
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.
const startUsage = process.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(process.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.
console.log(`Current directory: ${process.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 that same as calling the parent\nprocess's ChildProcess.disconnect()
.
If the Node.js process was not spawned with an IPC channel,\nprocess.disconnect()
will be undefined
.
The process.dlopen()
method allows to dynamically load shared\nobjects. It is primarily used by require()
to load\nC++ Addons, and should not be used directly, except in special\ncases. In other words, require()
should be preferred over\nprocess.dlopen()
, unless there are specific reasons.
The flags
argument is an integer that allows to specify dlopen\nbehavior. See the os.constants.dlopen
documentation for details.
If there are specific reasons to use process.dlopen()
(for instance,\nto specify dlopen flags), it's often useful to use require.resolve()
\nto look up the module's path.
An important drawback when calling process.dlopen()
is that the module
\ninstance must be passed. Functions exported by the C++ Addon will be accessible\nvia module.exports
.
The example below shows how to load a C++ Addon, named as binding
,\nthat exports a foo
function. All the symbols will be loaded before\nthe call returns, by passing the RTLD_NOW
constant. In this example\nthe constant is assumed to be available.
const os = require('os');\nprocess.dlopen(module, require.resolve('binding'),\n os.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."
}
],
"optional": true
}
]
}
],
"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.
// Emit a warning with a code and additional detail.\nprocess.emitWarning('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.
process.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.
// Emit a warning using a string.\nprocess.emitWarning('Something happened!');\n// Emits: (node: 56338) Warning: Something happened!\n
\n// Emit a warning using a string and a type.\nprocess.emitWarning('Something Happened!', 'CustomWarning');\n// Emits: (node:56338) CustomWarning: Something Happened!\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.
process.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):
// 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\nprocess.emitWarning(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.
Note that 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, it is recommended to place the emitWarning()
behind a simple boolean\nflag as illustrated in the example below:
function emitMyWarning() {\n if (!emitMyWarning.warned) {\n emitMyWarning.warned = true;\n process.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": []
},
"signatures": [
{
"params": [
{
"textRaw": "`code` {integer} The exit code. **Default:** `0`.",
"name": "code",
"type": "integer",
"default": "`0`",
"desc": "The exit code.",
"optional": true
}
]
}
],
"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:
\nprocess.exit(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:
// This is an example of what *not* to do:\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.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:
// 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.getegid()
method returns the numerical effective group identity\nof the Node.js process. (See getegid(2)
.)
if (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)
.)
if (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)
.)
if (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.
This 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)
.)
if (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:
\nconst NS_PER_SEC = 1e9;\nconst time = process.hrtime();\n// [ 1800216, 25 ]\n\nsetTimeout(() => {\n const diff = process.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 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.
const start = process.hrtime.bigint();\n// 191051479007711n\n\nsetTimeout(() => {\n const end = process.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.
Note that care must be taken when dropping privileges:
\nconsole.log(process.getgroups()); // [ 0 ]\nprocess.initgroups('bnoordhuis', 1000); // switch user\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000, 0 ]\nprocess.setgid(1000); // drop root gid\nconsole.log(process.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.
process.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.
The process.memoryUsage()
method returns an object describing the memory usage\nof the Node.js process measured in bytes.
For example, the code:
\nconsole.log(process.memoryUsage());\n
\nWill generate:
\n\n{\n rss: 4935680,\n heapTotal: 1826816,\n heapUsed: 650472,\n external: 49879\n}\n
\nheapTotal
and heapUsed
refer to V8's memory usage.\nexternal
refers to the memory usage of C++ objects bound to JavaScript\nobjects managed by V8. rss
, Resident Set Size, is the amount of space\noccupied in the main memory device (that is a subset of the total allocated\nmemory) for the process, which includes the heap, code segment and stack.
The heap is where objects, strings, and closures are stored. Variables are\nstored in the stack and the actual JavaScript code resides in the\ncode segment.
\nWhen 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.
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. As a result, it's\npossible to create an infinite loop if one were to recursively call\nprocess.nextTick()
.
console.log('start');\nprocess.nextTick(() => {\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:
\nfunction MyThing(options) {\n this.setupOptions(options);\n\n process.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:
\nfunction definitelyAsync(arg, cb) {\n if (arg) {\n process.nextTick(cb);\n return;\n }\n\n fs.stat('file', cb);\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",
"optional": true
},
{
"textRaw": "`options` {Object}",
"name": "options",
"type": "Object",
"optional": true
},
{
"textRaw": "`callback` {Function}",
"name": "callback",
"type": "Function",
"optional": true
}
]
}
],
"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.
if (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.log(`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.
if (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.log(`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.
if (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.log(`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.
This 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.
if (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.log(`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.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.
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.
The process.umask()
method sets or returns the Node.js process's file mode\ncreation mask. Child processes inherit the mask from the parent process. Invoked\nwithout an argument, the current mask is returned, otherwise the umask is set to\nthe argument value and the previous mask is returned.
const newmask = 0o022;\nconst oldmask = process.umask(newmask);\nconsole.log(\n `Changed umask from ${oldmask.toString(8)} to ${newmask.toString(8)}`\n);\n
\nThis feature is not available in Worker
threads.
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:
process.allowedNodeEnvironmentFlags.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 process.arch
property returns a string identifying the operating system\nCPU architecture for which the Node.js binary was compiled.
The current possible values are: 'arm'
, 'arm64'
, 'ia32'
, 'mips'
,\n'mipsel'
, 'ppc'
, 'ppc64'
, 's390'
, 's390x'
, 'x32'
, and 'x64'
.
console.log(`This processor architecture is ${process.arch}`);\n
"
},
{
"textRaw": "`argv` {string[]}",
"type": "string[]",
"name": "argv",
"meta": {
"added": [
"v0.1.27"
],
"changes": []
},
"desc": "The process.argv
property returns an array containing the command line\narguments passed when the Node.js process was launched. The first element will\nbe process.execPath
. See process.argv0
if access to the original value of\nargv[0]
is needed. The second element will be the path to the JavaScript\nfile being executed. The remaining elements will be any additional command line\narguments.
For example, assuming the following script for process-args.js
:
// print process.argv\nprocess.argv.forEach((val, index) => {\n console.log(`${index}: ${val}`);\n});\n
\nLaunching the Node.js process as:
\n$ node 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": []
},
"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
.
The process.config
property returns an Object
containing the JavaScript\nrepresentation of the configure options used to compile the current Node.js\nexecutable. This is the same as the config.gypi
file that was produced when\nrunning 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 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_dtrace: 'false',\n node_use_openssl: 'true',\n node_shared_openssl: 'false',\n strict_aliasing: 'true',\n target_arch: 'x64',\n v8_use_snapshot: 'true'\n }\n}\n
\nThe process.config
property is not read-only and there are existing\nmodules in the ecosystem that are known to extend, modify, or entirely replace\nthe value of process.config
.
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 Node.js's debugger when enabled.
\nprocess.debugPort = 5858;\n
"
},
{
"textRaw": "`env` {Object}",
"type": "Object",
"name": "env",
"meta": {
"added": [
"v0.1.27"
],
"changes": [
{
"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. In other words, the following example\nwould not work:
\n$ node -e 'process.env.foo = \"bar\"' && echo $foo\n
\nWhile the following will:
\nprocess.env.foo = 'bar';\nconsole.log(process.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.
process.env.test = null;\nconsole.log(process.env.test);\n// => 'null'\nprocess.env.test = undefined;\nconsole.log(process.env.test);\n// => 'undefined'\n
\nUse delete
to delete a property from process.env
.
process.env.TEST = 1;\ndelete process.env.TEST;\nconsole.log(process.env.TEST);\n// => undefined\n
\nOn Windows operating systems, environment variables are case-insensitive.
\nprocess.env.TEST = 1;\nconsole.log(process.env.test);\n// => 1\n
\nprocess.env
is read-only in Worker
threads.
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
"
},
{
"textRaw": "`execPath` {string}",
"type": "string",
"name": "execPath",
"meta": {
"added": [
"v0.1.100"
],
"changes": []
},
"desc": "The process.execPath
property returns the absolute pathname of the executable\nthat started the Node.js process.
'/usr/local/bin/node'\n
"
},
{
"textRaw": "`exitCode` {integer}",
"type": "integer",
"name": "exitCode",
"meta": {
"added": [
"v0.11.8"
],
"changes": []
},
"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.
The process.pid
property returns the PID of the process.
console.log(`This process is pid ${process.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 on which the Node.js process is running.
Currently possible values are:
\n'aix'
'darwin'
'freebsd'
'linux'
'openbsd'
'sunos'
'win32'
console.log(`This platform is ${process.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 current parent process.
console.log(`The parent process is pid ${process.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'
for Node.js. For\nlegacy io.js releases, this will be 'io.js'
.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> an absolute URL pointing to a node.lib
file matching the\narchitecture and version of the current release. This file is used for\ncompiling Node.js native add-ons. This property is only present on Windows\nbuilds of Node.js and will be missing on all other platforms.lts
<string> a string label identifying the LTS label for this release.\nThis property only exists for LTS releases and is undefined
for all other\nrelease types, including Current releases. Currently the valid values are:
'Argon'
for the 4.x LTS line beginning with 4.2.0.'Boron'
for the 6.x LTS line beginning with 6.9.0.'Carbon'
for the 8.x LTS line beginning with 8.9.1.{\n name: 'node',\n lts: 'Argon',\n sourceUrl: 'https://nodejs.org/download/release/v4.4.5/node-v4.4.5.tar.gz',\n headersUrl: 'https://nodejs.org/download/release/v4.4.5/node-v4.4.5-headers.tar.gz',\n libUrl: 'https://nodejs.org/download/release/v4.4.5/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.
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.
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.
process.stdin.setEncoding('utf8');\n\nprocess.stdin.on('readable', () => {\n const chunk = process.stdin.read();\n if (chunk !== null) {\n process.stdout.write(`data: ${chunk}`);\n }\n});\n\nprocess.stdin.on('end', () => {\n process.stdout.write('end');\n});\n
\nAs 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.
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
:
process.stdin.pipe(process.stdout);\n
\nprocess.stdout
differs from other Node.js streams in important ways. See\nnote on process I/O for more information.
process.stdout
and process.stderr
differ from other Node.js streams in\nimportant ways:
console.log()
and console.error()
,\nrespectively.Writes may be synchronous depending on what the stream is connected to\nand whether the system is Windows or POSIX:
\nThese behaviors are partly for historical reasons, as changing them would\ncreate backwards 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, its 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 process.throwDeprecation
property indicates whether the\n--throw-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.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.
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 returns the Node.js version string.
console.log(`Version: ${process.version}`);\n
"
},
{
"textRaw": "`versions` {Object}",
"type": "Object",
"name": "versions",
"meta": {
"added": [
"v0.2.0"
],
"changes": [
{
"version": "v4.2.0",
"pr-url": "https://github.com/nodejs/node/pull/3102",
"description": "The `icu` property is now supported."
},
{
"version": "v9.0.0",
"pr-url": "https://github.com/nodejs/node/pull/15785",
"description": "The `v8` property now includes a Node.js specific suffix."
}
]
},
"desc": "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.
console.log(process.versions);\n
\nWill generate an object similar to:
\n\n{ http_parser: '2.7.0',\n node: '8.9.0',\n v8: '6.3.292.48-node.6',\n uv: '1.18.0',\n zlib: '1.2.11',\n ares: '1.13.0',\n modules: '60',\n nghttp2: '1.29.0',\n napi: '2',\n openssl: '1.0.2n',\n icu: '60.1',\n unicode: '10.0',\n cldr: '32.0',\n tz: '2016b' }\n
"
}
]
}
],
"methods": [
{
"textRaw": "require()",
"type": "method",
"name": "require",
"signatures": [
{
"params": []
}
],
"desc": "This variable may appear to be global but is not. See require()
.