Node.js v21.6.2 documentation

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 copy

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(); copy

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! copy

abortSignal.throwIfAborted()#

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

Class: Blob#

See <Blob>.

Class: Buffer#

• <Function>

Used to handle binary data. See the buffer section.

Class: ByteLengthQueuingStrategy#

A browser-compatible implementation of ByteLengthQueuingStrategy.

__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.

atob(data)#

Global alias for buffer.atob().

BroadcastChannel#

See <BroadcastChannel>.

btoa(data)#

Global alias for buffer.btoa().

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: CompressionStream#

A browser-compatible implementation of CompressionStream.

console#

• <Object>

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

Class: CountQueuingStrategy#

A browser-compatible implementation of CountQueuingStrategy.

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.

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.

CustomEvent#

A browser-compatible implementation of the CustomEvent Web API.

Class: DecompressionStream#

A browser-compatible implementation of DecompressionStream.

Event#

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

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.

Class: File#

See <File>.

Class FormData#

A browser-compatible implementation of <FormData>.

global#

• <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>.

MessageChannel#

The MessageChannel class. See MessageChannel for more details.

MessageEvent#

The MessageEvent class. See MessageEvent for more details.

MessagePort#

The MessagePort class. See MessagePort for more details.

module#

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

Navigator#

A partial implementation of the Navigator API.

navigator#

A partial implementation of window.navigator.

navigator.hardwareConcurrency#

• <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`); copy

navigator.language#

• <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}'`); copy

navigator.languages#

• {Array}

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}'`); copy

navigator.platform#

• <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}`); copy

navigator.userAgent#

• <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" copy

PerformanceEntry#

The PerformanceEntry class. See PerformanceEntry for more details.

PerformanceMark#

The PerformanceMark class. See PerformanceMark for more details.

PerformanceMeasure#

The PerformanceMeasure class. See PerformanceMeasure for more details.

PerformanceObserver#

The PerformanceObserver class. See PerformanceObserver for more details.

PerformanceObserverEntryList#

The PerformanceObserverEntryList class. See PerformanceObserverEntryList for more details.

PerformanceResourceTiming#

The PerformanceResourceTiming class. See PerformanceResourceTiming for more details.

performance#

The perf_hooks.performance object.

process#

• <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);
}; copy

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.

require()#

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

Response#

A browser-compatible implementation of <Response>.

Request#

A browser-compatible implementation of <Request>.

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.

structuredClone(value[, options])#

The WHATWG structuredClone method.

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.

DOMException#

The WHATWG DOMException class. See DOMException for more details.

TextDecoder#

The WHATWG TextDecoder class. See the TextDecoder section.

Class: TextDecoderStream#

A browser-compatible implementation of TextDecoderStream.

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.

URL#

The WHATWG URL class. See the URL section.

URLSearchParams#

The WHATWG URLSearchParams class. See the URLSearchParams section.

WebAssembly#

• <Object>

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

WebSocket#

A browser-compatible implementation of WebSocket. Enable this API with the --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.