Package Exports

nanoevents
nanoevents/unbind-all

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Readme

Nano Events

Simple and tiny event emitter library for JavaScript.

No Node.js EventEmitter compatibility.
Only 118 bytes (minified and gzipped). It uses Size Limit to control size.
on method returns unbind function. You don’t need to save callback to variable for removeListener.
No aliases, just emit and on methods.

import NanoEvents from 'nanoevents'
const emitter = new NanoEvents()

const unbind = emitter.on('tick', volume => {
  summary += volume
})

function disable () {
  unbind()
}

Usage

Mixing to Object

Because main Nano Events API has only 2 methods, you could just create proxy methods in your class:

class Ticker {
  constructor() {
    this.emitter = new NanoEvents()
  }
  on() {
    return this.emitter.on.apply(this.emitter, arguments)
  }
  tick() {
    this.emitter.emit('tick')
  }
}

Add Listener

Use on method to add listener for specific event:

emitter.on('tick', number => {
  console.log(number)
})

emitter.emit('tick', 1)
// Prints "1"
emitter.emit('tick', 2)
// Prints "2"

Remove Listener

Methods on returns unbind function. Call it and this listener will be removed from event.

const unbind = emitter.on('tick', number => {
  console.log('on ' + number)
})

emitter.emit('tick', 1)
// Prints "on 1"

unbind()
emitter.emit('tick', 2)
// Prints nothing

Execute Listeners

Method emit will execute all listeners. First argument is event name, others will be passed to listeners.

emitter.on('tick', (a, b) => {
  console.log(a, b)
})
emitter.emit('tick', 1, 'one')
// Prints 1, 'one'

Events List

You can get used events list by events property.

const unbind = emitter.on('tick', () => { })
Object.keys(emitter.events) //=> ["tick"]

unbind()
Object.keys(emitter.events) //=> []

Helpers

Once

If you need add event listener only for first event dispatch, you can use this snippet:

class Ticker {
  constructor() {
    this.emitter = new NanoEvents()
  }
  …
  once (event, callback) {
    const unbind = this.emitter.on(event, function () {
      unbind()
      callback.apply(this, arguments)
    })
    return unbind
  }
}

Remove all listeners

unbindAll method will remove all listeners to all events.

import unbindAll from 'nanoevents/unbind-all';

emitter.on('event1', () => { })
emitter.on('event2', () => { })

unbindAll(emitter);

Object.keys(emitter.events) //=> { }