Global objects | Node.js v14.21.3 Documentation (original) (raw)

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 modules, see themodule system documentation:

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

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

Class: AbortController#

Added in: v14.17.0

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

To use, launch Node.js using the --experimental-abortcontroller flag.

const ac = new AbortController();

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

ac.abort();

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

abortController.abort()#

Added in: v14.17.0

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

abortController.signal#

Added in: v14.17.0

• Type:

Class: AbortSignal#

Added in: v14.17.0

• Extends:

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

Static method: AbortSignal.abort()#

Added in: v14.17.0

• Returns:

Returns a new already aborted AbortSignal.

Event: 'abort'#

Added in: v14.17.0

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#

Added in: v14.17.0

• Type: True after the AbortController has been aborted.

abortSignal.onabort#

Added in: v14.17.0

• Type:

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

Class: Buffer#

Added in: v0.1.103

Used to handle binary data. See the buffer section.

__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.

clearImmediate(immediateObject)#

Added in: v0.9.1

clearImmediate is described in the timers section.

clearInterval(intervalObject)#

Added in: v0.0.1

clearInterval is described in the timers section.

clearTimeout(timeoutObject)#

Added in: v0.0.1

clearTimeout is described in the timers section.

console#

Added in: v0.1.100

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

exports#

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

global#

Added in: v0.1.27

• The global namespace object.

In browsers, the top-level scope is the global scope. This means that within the browser var something will define a new global variable. 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.

module#

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

process#

Added in: v0.1.7

The process object. See the process object section.

queueMicrotask(callback)#

Added in: v11.0.0

• callback Function to be queued.

The queueMicrotask() method queues a microtask to invoke callback. Ifcallback 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. Theprocess.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);
};

require()#

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

setImmediate(callback[, ...args])#

Added in: v0.9.1

setImmediate is described in the timers section.

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

Added in: v0.0.1

setInterval is described in the timers section.

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

Added in: v0.0.1

setTimeout is described in the timers section.

TextDecoder#

Added in: v11.0.0

The WHATWG TextDecoder class. See the TextDecoder section.

TextEncoder#

Added in: v11.0.0

The WHATWG TextEncoder class. See the TextEncoder section.

URL#

Added in: v10.0.0

The WHATWG URL class. See the URL section.

URLSearchParams#

Added in: v10.0.0

The WHATWG URLSearchParams class. See the URLSearchParams section.

WebAssembly#

Added in: v8.0.0

The object that acts as the namespace for all W3CWebAssembly related functionality. See theMozilla Developer Network for usage and compatibility.