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Kucukkanat's Emitter

Table of Contents

Install

This project uses node and npm. Go check them out if you don't have them locally installed.

$ npm install --save subscribe
// using ES6 modules
import { Emitter } from 'subscribe'

// using CommonJS modules
var { Emitter } = require('subscribe')

The UMD build is also available on unpkg:

<script src="https://esm.sh/subscribe"></script>

You can find the library on window.__Emitter__.

Usage

import {Emitter} from 'subscribe'
// OR
const {Emitter} = require('subscribe')

const eventbus = new Emitter()

// listen to an event
eventbus.on('foo', e => console.log('foo', e) )

// listen to all events
// This will fire first the 'type' event if it exists
eventbus.on('*', (type, e) => console.log(type, e) )

// fire an event
eventbus.emit('foo', { a: 'b' })

// working with handler references:
function onFoo() {}
eventbus.on('foo', onFoo)   // listen
eventbus.off('foo', onFoo)  // unlisten

// remove all listeners for specific event
eventbus.off('foo')

// Fire event listener only once
eventbus.once('knock knock', (data) => console.log("I will be fired only once"))
eventbus.emit('knock knock', null)
// This will not fire
eventbus.emit('knock knock', null)

Typescript

For better autocompletion Emitter class takes parameters for possible event names :

import {Emitter} from 'subscribe'
const emitter = new Emitter<'foo' | 'bar'>()
emitter.on('foo', e => console.log('foo', e) )
emitter.on('bar', e => console.log('foo', e) )
// Will throw an error: (on typescript typecheck NOT ON RUNTIME!)
emitter.on('bar2', e => console.log('foo', e) )

API

Table of Contents

constructor

Use the constructor to initiate the eventbus with handlers

Parameters

  • ``
  • listeners EventHandlerMap

on

Register an event handler for the given type.

Parameters

  • type String Type of event to listen for, or "*" for all events
  • handler Function Function to call in response to given event

off

Remove an event handler for the given type.

Parameters

  • type String Type of event to unregister handler from, or "*"
  • handler Function Handler function to remove

emit

Invoke this.listeners handlers for the given type. If present, "*" handlers are invoked after type-matched handlers.

Note: Manually firing "*" handlers is not supported.

Parameters

  • type String The event type to invoke
  • evt Any? Any value (object is recommended and powerful), passed to each handler

Reporting Issues

Found a problem? Want a new feature? First of all see if your issue or idea has already been reported. If don't, just open a new clear and descriptive issue.

License

MIT License © Kucukkanat