events

What is events?

The 'events' npm package provides a way to implement the Observer pattern, which is a software design pattern that allows an object (known as a 'subject') to maintain a list of its dependents (known as 'observers') and automatically notify them of any state changes, usually by calling one of their methods. It is the same EventEmitters API as used by Node.js core.

What are events's main functionalities?

EventEmitter creation

This code sample shows how to import the 'events' package and create a new instance of an EventEmitter.

const EventEmitter = require('events');
const myEmitter = new EventEmitter();

Event listening

This code sample demonstrates how to listen for an 'event' and execute a callback function when the event is emitted.

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

Event emitting

This code sample shows how to emit an 'event', which will trigger any associated event listeners.

myEmitter.emit('event');

Once listener

This code sample demonstrates how to set up a listener that will only be called once for the next time the event is emitted.

myEmitter.once('event', () => {
  console.log('this event will be logged only once');
});

Removing listeners

This code sample shows how to remove a specific listener from an event.

const callback = () => console.log('event occurred');
myEmitter.on('event', callback);
// ...
myEmitter.removeListener('event', callback);

Other packages similar to events

mitt

Mitt is a tiny functional event emitter / pubsub. It provides the same basic functionality as 'events' but with a smaller footprint and a more functional approach.

eventemitter3

EventEmitter3 is a high performance EventEmitter. It has a similar API to 'events' but is optimized for performance and has no dependencies.

wolfy87-eventemitter

Wolfy87's EventEmitter is an implementation of the EventEmitter module found in Node.js but for the browser. It offers similar functionality to 'events' but is designed to work in a browser environment.

README

events

Node's event emitter for all engines.

Install

npm install events

Require

var EventEmitter = require('events').EventEmitter

Usage

See the node.js event emitter docs

Changelog

1.1.1 (2016-06-22)

• add more context to errors if they are not instanceof Error