Skip to main content
events - Node documentation

Usage in Deno

import * as mod from "node:events";

Much of the Node.js core API is built around an idiomatic asynchronous event-driven architecture in which certain kinds of objects (called "emitters") emit named events that cause Function objects ("listeners") to be called.

For instance: a net.Server object emits an event each time a peer connects to it; a fs.ReadStream emits an event when the file is opened; a stream emits an event whenever data is available to be read.

All objects that emit events are instances of the EventEmitter class. These objects expose an eventEmitter.on() function that allows one or more functions to be attached to named events emitted by the object. Typically, event names are camel-cased strings but any valid JavaScript property key can be used.

When the EventEmitter object emits an event, all of the functions attached to that specific event are called synchronously. Any values returned by the called listeners are ignored and discarded.

The following example shows a simple EventEmitter instance with a single listener. The eventEmitter.on() method is used to register listeners, while the eventEmitter.emit() method is used to trigger the event.

import { EventEmitter } from 'node:events';

class MyEmitter extends EventEmitter {}

const myEmitter = new MyEmitter();
myEmitter.on('event', () => {
  console.log('an event occurred!');
});
myEmitter.emit('event');

Classes

c
EventEmitter.EventEmitterAsyncResource

Integrates EventEmitter with AsyncResource for EventEmitters thatrequire manual async tracking. Specifically, all events emitted by instancesof events.EventEmitterAsyncResource will run within its async context.

Interfaces

Type Aliases

T
AnyRest
No documentation available
T
Args
No documentation available
T
DefaultEventMap
No documentation available
T
EventMap
No documentation available
T
Key
No documentation available
T
Key2
No documentation available
T
Listener
No documentation available
T
Listener1
No documentation available
T
Listener2
No documentation available