The node:vfs module provides an in-memory virtual file system with a\nnode:fs-like API. It is useful for tests, fixtures, embedded assets, and other\nscenarios where you need a self-contained file system without touching the\nactual file-system.
To access it:
\nimport vfs from 'node:vfs';\nconst vfs = require('node:vfs');\nThis module is only available under the node: scheme, and only when Node.js\nis started with the --experimental-vfs flag.
const vfs = require('node:vfs');\n\nconst myVfs = vfs.create();\nmyVfs.mkdirSync('/dir', { recursive: true });\nmyVfs.writeFileSync('/dir/hello.txt', 'Hello, VFS!');\n\nconsole.log(myVfs.readFileSync('/dir/hello.txt', 'utf8')); // 'Hello, VFS!'\nvfs.create() returns a VirtualFileSystem instance backed by a\nMemoryProvider by default. The instance exposes synchronous,\ncallback-based, and promise-based file system methods that mirror the\nshape of the node:fs API. All paths are POSIX-style and absolute\n(starting with /).
VFS Stats objects are real instances of fs.Stats (or\nfs.BigIntStats when { bigint: true } is requested). Their\nfields use synthetic but stable values:
dev is 4085 (the VFS device id).ino is monotonically increasing per process.blksize is 4096.blocks is Math.ceil(size / 512).provider {VirtualProvider} The provider to use. Default:\nnew MemoryProvider().options <Object>\nemitExperimentalWarning <boolean> Whether to emit the experimental\nwarning when the instance is created. Default: true.Convenience factory equivalent to new VirtualFileSystem(provider, options).
const vfs = require('node:vfs');\n\n// Default in-memory provider\nconst memoryVfs = vfs.create();\n\n// Explicit provider\nconst realVfs = vfs.create(new vfs.RealFSProvider('/tmp/sandbox'));\nA VirtualFileSystem wraps a VirtualProvider and exposes a\nnode:fs-like API. Each instance maintains its own file tree.
provider {VirtualProvider} The provider to use. Default:\nnew MemoryProvider().options <Object>\nemitExperimentalWarning <boolean> Whether to emit the experimental\nwarning. Default: true.The provider backing this VFS instance.
" }, { "textRaw": "{boolean}", "name": "readonly", "type": "boolean", "meta": { "added": [ "REPLACEME" ], "changes": [] }, "desc": "true when the underlying provider is read-only.
VirtualFileSystem implements the following methods, with the same\nsignatures as their node:fs counterparts:
existsSync(path)statSync(path[, options])lstatSync(path[, options])readFileSync(path[, options])writeFileSync(path, data[, options])appendFileSync(path, data[, options])readdirSync(path[, options])mkdirSync(path[, options])rmdirSync(path)unlinkSync(path)renameSync(oldPath, newPath)copyFileSync(src, dest[, mode])realpathSync(path[, options])readlinkSync(path[, options])symlinkSync(target, path[, type])accessSync(path[, mode])rmSync(path[, options])truncateSync(path[, len])ftruncateSync(fd[, len])linkSync(existingPath, newPath)chmodSync(path, mode)chownSync(path, uid, gid)utimesSync(path, atime, mtime)lutimesSync(path, atime, mtime)mkdtempSync(prefix)opendirSync(path[, options])openAsBlob(path[, options])openSync, closeSync, readSync, writeSync,\nfstatSynccreateReadStream, createWriteStreamwatch, watchFile, unwatchFilereadFile, writeFile, stat, lstat, readdir, realpath, readlink,\naccess, open, close, read, write, rm, fstat, truncate,\nftruncate, link, mkdtemp, opendir. Each takes a Node.js-style\ncallback (err, ...result) => {}.
vfs.promises exposes the promise-based variants:
const vfs = require('node:vfs');\n\nasync function example() {\n const myVfs = vfs.create();\n await myVfs.promises.writeFile('/file.txt', 'hello');\n const data = await myVfs.promises.readFile('/file.txt', 'utf8');\n return data;\n}\nexample();\nThe promise namespace mirrors fs.promises and includes readFile,\nwriteFile, appendFile, stat, lstat, readdir, mkdir, rmdir,\nunlink, rename, copyFile, realpath, readlink, symlink,\naccess, rm, truncate, link, mkdtemp, chmod, chown, lchown,\nutimes, lutimes, open, lchmod, and watch.
The base class for all VFS providers. Subclasses implement the essential\nprimitives (open, stat, readdir, mkdir, rmdir, unlink,\nrename, ...) and inherit default implementations of the derived\nThe base class for all VFS providers. Subclasses implement the essential\nprimitives (such as open, stat, readdir, mkdir, rmdir, unlink,\nrename, etc.) and inherit default implementations of the derived\nmethods (such as readFile, writeFile, exists, copyFile, access, etc.).
provider.readonly <boolean> Default: false.provider.supportsSymlinks <boolean> Default: false.provider.supportsWatch <boolean> Default: false.const { VirtualProvider } = require('node:vfs');\n\nclass StaticProvider extends VirtualProvider {\n get readonly() { return true; }\n\n statSync(path) { /* ... */ }\n openSync(path, flags) { /* ... */ }\n readdirSync(path, options) { /* ... */ }\n // ...\n}\nThe base class throws ERR_METHOD_NOT_IMPLEMENTED for any primitive\nthat has not been overridden, and rejects writes from a readonly\nprovider with EROFS.
The default in-memory provider. Stores files, directories, and symbolic\nlinks in a Map-backed tree, supports symlinks (supportsSymlinks === true), and supports watching (supportsWatch === true).
Locks the provider into read-only mode. Subsequent writes through any\nVirtualFileSystem using this provider throw EROFS. There is no\nway to revert the provider to writable.
const vfs = require('node:vfs');\n\nconst provider = new vfs.MemoryProvider();\nconst myVfs = vfs.create(provider);\nmyVfs.writeFileSync('/seed.txt', 'initial');\n\nprovider.setReadOnly();\n\nmyVfs.writeFileSync('/x.txt', 'fail'); // throws EROFS\nA provider that wraps a directory (i.e. one on the actual file system) and exposes its\ncontents through the VFS API. All VFS paths are resolved relative to\nthe root and verified to stay inside it; symbolic links resolving\noutside the root are rejected.
", "signatures": [ { "textRaw": "`new RealFSProvider(rootPath)`", "name": "RealFSProvider", "type": "ctor", "meta": { "added": [ "REPLACEME" ], "changes": [] }, "params": [ { "textRaw": "`rootPath` {string} The absolute file-system path to use as the root. Must be a non-empty string.", "name": "rootPath", "type": "string", "desc": "The absolute file-system path to use as the root. Must be a non-empty string." } ], "desc": "const vfs = require('node:vfs');\n\nconst realVfs = vfs.create(new vfs.RealFSProvider('/tmp/sandbox'));\nrealVfs.writeFileSync('/file.txt', 'hello'); // writes /tmp/sandbox/file.txt\nThe resolved absolute path used as the root.
" } ] } ], "displayName": "Virtual File System" } ] }