events

Fast event emitter for javascript. Check the benchmarks.

This is the benchmark result that emit event to the single listener

event-emitter x 6,300,170 ops/sec ±1.59% (94 runs sampled)
EventEmitter2 x 10,258,851 ops/sec ±0.54% (92 runs sampled)
EventEmitter3 x 12,151,111 ops/sec ±0.30% (91 runs sampled)
component-emitter x 2,663,473 ops/sec ±0.77% (94 runs sampled)
wolfy87-eventemitter x 2,081,167 ops/sec ±0.48% (95 runs sampled)
@foxify/events x 19,033,563 ops/sec ±0.72% (92 runs sampled)
@yoshibu/events x 20,305,984 ops/sec ±0.43% (93 runs sampled)
Fastest is @yoshibu/events

Features

• Fast
• Compiled by the buble, and the compile target is 'ie8'
• Support ES2015 module, CommonJS, and the browser
• Support Wildcard event

Install

npm

npm i @yoshibu/events

CDN

<script src="https://unpkg.com/@yoshibu/events/dist/events.browser.js"></script>

You can find the library on window.EventEmitter

Usage

import EventEmitter from '@yoshibu/events'
// const EventEmitter = require('@yoshibu/events') // CommonJS

const emitter = new EventEmitter();

// listen to an event
emitter.on('foo', message => console.log(message));

// listen to all events
emitter.on('*', (event, message) => console.log(event, message));

emitter.emit('foo', 'hello');
// --- console ---
// foo hello
// hello

API

addListener(event, listener)

Alias for the on

on(event, listener)

• event: string
• listener: function
• Returns: EventEmitter

Register an event listener for the given event.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee.on('foo', message => console.log(message));

If you specified '*' for the event, the listener will be invoked with an event name and the arguments when any events emitted.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee.on('*', console.log);

ee.emit('foo', 1, 2, 3);
// --- console ---
// foo 1 2 3

once(event, listener)

• event: string
• listener: function
• Returns: EventEmitter

Register an one-time event listener for the given event.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee.once('foo', message => console.log(message));

emit(event[, ...args])

• event: string
• args: any
• Returns: boolean

Synchronously invoke each of the listeners registered for the given event, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee.emit('foo', 1, 2, 3);

Event listener execution order

1. Listeners registered for the '*' event by the once method
2. Listeners registered for the'*' event by the addListener or on method
3. Listeners registered for the given event by the once method
4. Listeners registered for the given event by the addListener or on method

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee
  .on('foo', () => console.log('on: foo'))
  .once('foo', () => console.log('once: foo'))
  .on('*', () => console.log('on: *'))
  .once('*', () => console.log('once: *'));

ee.emit('foo');
// --- console ---
// once: *
// on: *
// once: foo
// on: foo

removeListener(event, listener)

• event: string
• listener: function
• Retusns: EventEmitter

Remove all specified listeners from the given event.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

const listener = () => {};

ee.on('foo', listener);

ee.removeListener('foo', listener);

removeAllListeners([event])

• event: string
• Returns: EventEmitter

Remove all listeners from the given event. If event is not passed, remove all listeners.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee.removeAllListeners('foo');

listenerCount(event)

• event: string
• Returns: number

Returns the listener count for the given event.

import EventEmitter from '@yoshibu/events'

const ee = new EventEmitter();

ee.listenerCount('foo'); // 0

Liccence

MIT License © YooShibu