node/doc/api/globals.md

Global objects

Stability: 2 - Stable

These objects are available in all modules.

The following variables may appear to be global but are not. They exist only in the scope of CommonJS modules:

• __dirname
• __filename
• exports
• module
• require()

The objects listed here are specific to Node.js. There are built-in objects that are part of the JavaScript language itself, which are also globally accessible.

__dirname

This variable may appear to be global but is not. See __dirname.

__filename

This variable may appear to be global but is not. See __filename.

Class: AbortController

A utility class used to signal cancelation in selected Promise-based APIs. The API is based on the Web API {AbortController}.

const ac = new AbortController();

ac.signal.addEventListener('abort', () => console.log('Aborted!'),
                           { once: true });

ac.abort();

console.log(ac.signal.aborted);  // Prints true

abortController.abort([reason])

• reason {any} An optional reason, retrievable on the AbortSignal's reason property.

Triggers the abort signal, causing the abortController.signal to emit the 'abort' event.

abortController.signal

• Type: {AbortSignal}

Class: AbortSignal

• Extends: {EventTarget}

The AbortSignal is used to notify observers when the abortController.abort() method is called.

Static method: AbortSignal.abort([reason])

• reason {any}
• Returns: {AbortSignal}

Returns a new already aborted AbortSignal.

Static method: AbortSignal.timeout(delay)

• delay {number} The number of milliseconds to wait before triggering the AbortSignal.

Returns a new AbortSignal which will be aborted in delay milliseconds.

Static method: AbortSignal.any(signals)

• signals {AbortSignal[]} The AbortSignals of which to compose a new AbortSignal.

Returns a new AbortSignal which will be aborted if any of the provided signals are aborted. Its abortSignal.reason will be set to whichever one of the signals caused it to be aborted.

Event: 'abort'

The 'abort' event is emitted when the abortController.abort() method is called. The callback is invoked with a single object argument with a single type property set to 'abort':

const ac = new AbortController();

// Use either the onabort property...
ac.signal.onabort = () => console.log('aborted!');

// Or the EventTarget API...
ac.signal.addEventListener('abort', (event) => {
  console.log(event.type);  // Prints 'abort'
}, { once: true });

ac.abort();

The AbortController with which the AbortSignal is associated will only ever trigger the 'abort' event once. We recommended that code check that the abortSignal.aborted attribute is false before adding an 'abort' event listener.

Any event listeners attached to the AbortSignal should use the { once: true } option (or, if using the EventEmitter APIs to attach a listener, use the once() method) to ensure that the event listener is removed as soon as the 'abort' event is handled. Failure to do so may result in memory leaks.

abortSignal.aborted

• Type: {boolean}

True after the AbortController has been aborted.

abortSignal.onabort

• Type: {Function}

An optional callback function that may be set by user code to be notified when the abortController.abort() function has been called.

abortSignal.reason

• Type: {any}

An optional reason specified when the AbortSignal was triggered.

const ac = new AbortController();
ac.abort(new Error('boom!'));
console.log(ac.signal.reason);  // Error: boom!

abortSignal.throwIfAborted()

If abortSignal.aborted is true, throws abortSignal.reason.

atob(data)

Stability: 3 - Legacy. Use Buffer.from(data, 'base64') instead.

Global alias for buffer.atob().

An automated migration is available (source):

npx codemod@latest @nodejs/buffer-atob-btoa

Class: Blob

See {Blob}.

Class: BroadcastChannel

See {BroadcastChannel}.

btoa(data)

Stability: 3 - Legacy. Use buf.toString('base64') instead.

Global alias for buffer.btoa().

An automated migration is available (source):

npx codemod@latest @nodejs/buffer-atob-btoa

Class: Buffer

• Type: {Function}

Used to handle binary data. See the buffer section.

Class: ByteLengthQueuingStrategy

A browser-compatible implementation of ByteLengthQueuingStrategy.

clearImmediate(immediateObject)

clearImmediate is described in the timers section.

clearInterval(intervalObject)

clearInterval is described in the timers section.

clearTimeout(timeoutObject)

clearTimeout is described in the timers section.

Class: CloseEvent

A browser-compatible implementation of {CloseEvent}. Disable this API with the --no-experimental-websocket CLI flag.

Class: CompressionStream

A browser-compatible implementation of CompressionStream.

console

• Type: {Object}

Used to print to stdout and stderr. See the console section.

Class: CountQueuingStrategy

A browser-compatible implementation of CountQueuingStrategy.

Class: Crypto

A browser-compatible implementation of {Crypto}. This global is available only if the Node.js binary was compiled with including support for the node:crypto module.

crypto

A browser-compatible implementation of the Web Crypto API.

Class: CryptoKey

A browser-compatible implementation of {CryptoKey}. This global is available only if the Node.js binary was compiled with including support for the node:crypto module.

Class: CustomEvent

A browser-compatible implementation of {CustomEvent}.

Class: DecompressionStream

A browser-compatible implementation of DecompressionStream.

Class: DOMException

The WHATWG {DOMException} class.

ErrorEvent

A browser-compatible implementation of {ErrorEvent}.

Class: Event

A browser-compatible implementation of the Event class. See EventTarget and Event API for more details.

Class: EventSource

Stability: 1 - Experimental. Enable this API with the --experimental-eventsource CLI flag.

A browser-compatible implementation of {EventSource}.

Class: EventTarget

A browser-compatible implementation of the EventTarget class. See EventTarget and Event API for more details.

exports

This variable may appear to be global but is not. See exports.

fetch

A browser-compatible implementation of the fetch() function.

const res = await fetch('https://nodejs.org/api/documentation.json');
if (res.ok) {
  const data = await res.json();
  console.log(data);
}

The implementation is based upon undici, an HTTP/1.1 client written from scratch for Node.js. You can figure out which version of undici is bundled in your Node.js process reading the process.versions.undici property.

Custom dispatcher

You can use a custom dispatcher to dispatch requests passing it in fetch's options object. The dispatcher must be compatible with undici's Dispatcher class.

fetch(url, { dispatcher: new MyAgent() });

It is possible to change the global dispatcher in Node.js by installing undici and using the setGlobalDispatcher() method. Calling this method will affect both undici and Node.js.

import { setGlobalDispatcher } from 'undici';
setGlobalDispatcher(new MyAgent());

Related classes

The following globals are available to use with fetch:

• FormData
• Headers
• Request
• Response

Class: File

See {File}.

Class: FormData

A browser-compatible implementation of {FormData}.

global

Stability: 3 - Legacy. Use globalThis instead.

• Type: {Object} The global namespace object.

In browsers, the top-level scope has traditionally been the global scope. This means that var something will define a new global variable, except within ECMAScript modules. In Node.js, this is different. The top-level scope is not the global scope; var something inside a Node.js module will be local to that module, regardless of whether it is a CommonJS module or an ECMAScript module.

Class: Headers

A browser-compatible implementation of {Headers}.

localStorage

Stability: 1.2 - Release candidate. Disable this API with --no-experimental-webstorage.

A browser-compatible implementation of localStorage. Data is stored unencrypted in the file specified by the --localstorage-file CLI flag. The maximum amount of data that can be stored is 10 MB. Any modification of this data outside of the Web Storage API is not supported. localStorage data is not stored per user or per request when used in the context of a server, it is shared across all users and requests.

Class: MessageChannel

The MessageChannel class. See MessageChannel for more details.

Class: MessageEvent

A browser-compatible implementation of {MessageEvent}.

Class: MessagePort

The MessagePort class. See MessagePort for more details.

module

This variable may appear to be global but is not. See module.

Class: Navigator

Stability: 1.1 - Active development. Disable this API with the --no-experimental-global-navigator CLI flag.

A partial implementation of the Navigator API.

navigator

Stability: 1.1 - Active development. Disable this API with the --no-experimental-global-navigator CLI flag.

A partial implementation of window.navigator.

navigator.hardwareConcurrency

• Type: {number}

The navigator.hardwareConcurrency read-only property returns the number of logical processors available to the current Node.js instance.

console.log(`This process is running on ${navigator.hardwareConcurrency} logical processors`);

navigator.language

• Type: {string}

The navigator.language read-only property returns a string representing the preferred language of the Node.js instance. The language will be determined by the ICU library used by Node.js at runtime based on the default language of the operating system.

The value is representing the language version as defined in RFC 5646.

The fallback value on builds without ICU is 'en-US'.

console.log(`The preferred language of the Node.js instance has the tag '${navigator.language}'`);

navigator.languages

• Type: {string[]}

The navigator.languages read-only property returns an array of strings representing the preferred languages of the Node.js instance. By default navigator.languages contains only the value of navigator.language, which will be determined by the ICU library used by Node.js at runtime based on the default language of the operating system.

The fallback value on builds without ICU is ['en-US'].

console.log(`The preferred languages are '${navigator.languages}'`);

navigator.locks

Stability: 1 - Experimental

The navigator.locks read-only property returns a LockManager instance that can be used to coordinate access to resources that may be shared across multiple threads within the same process. This global implementation matches the semantics of the browser LockManager API.

// Request an exclusive lock
await navigator.locks.request('my_resource', async (lock) => {
  // The lock has been acquired.
  console.log(`Lock acquired: ${lock.name}`);
  // Lock is automatically released when the function returns
});

// Request a shared lock
await navigator.locks.request('shared_resource', { mode: 'shared' }, async (lock) => {
  // Multiple shared locks can be held simultaneously
  console.log(`Shared lock acquired: ${lock.name}`);
});

// Request an exclusive lock
navigator.locks.request('my_resource', async (lock) => {
  // The lock has been acquired.
  console.log(`Lock acquired: ${lock.name}`);
  // Lock is automatically released when the function returns
}).then(() => {
  console.log('Lock released');
});

// Request a shared lock
navigator.locks.request('shared_resource', { mode: 'shared' }, async (lock) => {
  // Multiple shared locks can be held simultaneously
  console.log(`Shared lock acquired: ${lock.name}`);
}).then(() => {
  console.log('Shared lock released');
});

See worker_threads.locks for detailed API documentation.

navigator.platform

• Type: {string}

The navigator.platform read-only property returns a string identifying the platform on which the Node.js instance is running.

console.log(`This process is running on ${navigator.platform}`);

navigator.userAgent

• Type: {string}

The navigator.userAgent read-only property returns user agent consisting of the runtime name and major version number.

console.log(`The user-agent is ${navigator.userAgent}`); // Prints "Node.js/21"

performance

The perf_hooks.performance object.

Class: PerformanceEntry

The PerformanceEntry class. See PerformanceEntry for more details.

Class: PerformanceMark

The PerformanceMark class. See PerformanceMark for more details.

Class: PerformanceMeasure

The PerformanceMeasure class. See PerformanceMeasure for more details.

Class: PerformanceObserver

The PerformanceObserver class. See PerformanceObserver for more details.

Class: PerformanceObserverEntryList

The PerformanceObserverEntryList class. See PerformanceObserverEntryList for more details.

Class: PerformanceResourceTiming

The PerformanceResourceTiming class. See PerformanceResourceTiming for more details.

process

• Type: {Object}

The process object. See the process object section.

queueMicrotask(callback)

• callback {Function} Function to be queued.

The queueMicrotask() method queues a microtask to invoke callback. If callback throws an exception, the process object 'uncaughtException' event will be emitted.

The microtask queue is managed by V8 and may be used in a similar manner to the process.nextTick() queue, which is managed by Node.js. The process.nextTick() queue is always processed before the microtask queue within each turn of the Node.js event loop.

// Here, `queueMicrotask()` is used to ensure the 'load' event is always
// emitted asynchronously, and therefore consistently. Using
// `process.nextTick()` here would result in the 'load' event always emitting
// before any other promise jobs.

DataHandler.prototype.load = async function load(key) {
  const hit = this._cache.get(key);
  if (hit !== undefined) {
    queueMicrotask(() => {
      this.emit('load', hit);
    });
    return;
  }

  const data = await fetchData(key);
  this._cache.set(key, data);
  this.emit('load', data);
};

Class: QuotaExceededError

The WHATWG {QuotaExceededError} class. Extends {DOMException}.

Class: ReadableByteStreamController

A browser-compatible implementation of ReadableByteStreamController.

Class: ReadableStream

A browser-compatible implementation of ReadableStream.

Class: ReadableStreamBYOBReader

A browser-compatible implementation of ReadableStreamBYOBReader.

Class: ReadableStreamBYOBRequest

A browser-compatible implementation of ReadableStreamBYOBRequest.

Class: ReadableStreamDefaultController

A browser-compatible implementation of ReadableStreamDefaultController.

Class: ReadableStreamDefaultReader

A browser-compatible implementation of ReadableStreamDefaultReader.

Class: Request

A browser-compatible implementation of {Request}.

require()

This variable may appear to be global but is not. See require().

Class: Response

A browser-compatible implementation of {Response}.

sessionStorage

Stability: 1.2 - Release candidate. Disable this API with --no-experimental-webstorage.

A browser-compatible implementation of sessionStorage. Data is stored in memory, with a storage quota of 10 MB. sessionStorage data persists only within the currently running process, and is not shared between workers.

setImmediate(callback[, ...args])

setImmediate is described in the timers section.

setInterval(callback, delay[, ...args])

setInterval is described in the timers section.

setTimeout(callback, delay[, ...args])

setTimeout is described in the timers section.

Class: Storage

Stability: 1.2 - Release candidate. Disable this API with --no-experimental-webstorage.

A browser-compatible implementation of {Storage}.

structuredClone(value[, options])

The WHATWG structuredClone method.

Class: SubtleCrypto

A browser-compatible implementation of {SubtleCrypto}. This global is available only if the Node.js binary was compiled with including support for the node:crypto module.

Class: TextDecoder

The WHATWG TextDecoder class. See the TextDecoder section.

Class: TextDecoderStream

A browser-compatible implementation of TextDecoderStream.

Class: TextEncoder

The WHATWG TextEncoder class. See the TextEncoder section.

Class: TextEncoderStream

A browser-compatible implementation of TextEncoderStream.

Class: TransformStream

A browser-compatible implementation of TransformStream.

Class: TransformStreamDefaultController

A browser-compatible implementation of TransformStreamDefaultController.

Class: URL

The WHATWG URL class. See the URL section.

Class: URLPattern

Stability: 1 - Experimental

The WHATWG URLPattern class. See the URLPattern section.

Class: URLSearchParams

The WHATWG URLSearchParams class. See the URLSearchParams section.

Class: WebAssembly

• Type: {Object}

The object that acts as the namespace for all W3C WebAssembly related functionality. See the Mozilla Developer Network for usage and compatibility.

Class: WebSocket

A browser-compatible implementation of {WebSocket}. Disable this API with the --no-experimental-websocket CLI flag.

Class: WritableStream

A browser-compatible implementation of WritableStream.

Class: WritableStreamDefaultController

A browser-compatible implementation of WritableStreamDefaultController.

Class: WritableStreamDefaultWriter

A browser-compatible implementation of WritableStreamDefaultWriter.