Emithor 📡

Simple pub-sub JavaScript implementation.

Features

• Attaching callbacks to custom events
• Triggering events and firing callbacks (with payload and context)
• Firing specific callbacks only once
• Removing events and specific callbacks

Install

$ npm install emithor

// or 
$ yarn add emithor

Basic usage

Using Emithor is very simple. You have two options for importing:

// Import class
import Emithor from 'emithor'
const emithor = new Emithor()

// ...Or import just what you want.
import { on, trigger } from 'emithor'

// Add event listeners
emithor.on('myEvent', () => { console.log('myEvent triggered') })
// ...And trigger event.
emithor.trigger('myEvent') // => 'myEvent triggered'

API

Instance of Emithor exposes following methods:

• on
• trigger
• remove
• getEvents

on()

(alias: subscribe, register)

Registers callback to specifeid event.

params

• eventName String - Can't be empty string
• callback Function - Callback to be executed when event triggers.
• ctx Object (default: null) - Context which is to be provided to callback
• once Boolean (default: false) - Controls if callback is going to be invoked only once

// Register handleMyEvent handler 
// on event named 'myEvent'
emithor.on('myEvent', handleMyEvent)

// When 'myEvent' gets triggered callback
// will be invoked, but just the first time
emithor.on('myEvent', handleMyEvent, null, true)

trigger()

(alias: publish, fire)

Triggers specified event's callbacks and passes the same payload to all of them. Optianally you can override predefined context for all callbacks by passing another value for this.

params

• eventName String
• context Any - Value for this of the callback. If you don't need it, just use null instead.
• payload Any - Params to pass to callback call.

// Let's first register our callback.
emithor.on('myEvent', () => { console.log('myEvent triggered') })

// Then trigger event without passing context and payload.
emithor.trigger('myEvent')
// => 'myEvent triggered'

// Add one more callback to event
emithor.on('myEvent', (a, b) => { console.log(a + b) })
// Triggering event fires all callbacks attached.
// Payload of `2, 2` is passed to all of them
emithor.trigger('myEvent', null, 2, 2)
// => 'myEvent triggered'
// => 4

// Add callback which requires both value for `this` and payload
emithor.on('myEvent', function(greeting) { 
  console.log(`${greeting} ${this.name}!`) 
})
// Create context 
const person = { name: 'Joe' }
// Passing context to `trigger` method overrides  
// context defined define with `on` menthod
emithor.trigger('myEvent', person, 'Hey')
// => 'Hey Joe!'

remove()

(alias: unsubscribe)

Removes an event or callback (or both). If callback is specified then it only removes callback. If there are no more callbacks after callback is deleted then it removes whole specified event.

params

• eventName String - Can't be empty string
• callback Function (default: null) - Callback to be executed when event triggers.

// Passing only event name removes 
// whole event with all of its callbacks.
emithor.remove('myEvent')

// Passing callback reference removes 
// that callback from given event.
emithor.remove('myEvent', callback)

getEvents()

(alias: getChannels)

Returns copy of all events.

console.log(emithor.getEvents()) 
// => [{name: 'event', cbs: [{fn: callback, ctx: null, once: false}]}]

Usage examples

Pass payload and trigger event multiple times:

const emithor = new Emithor()

emithor.on('myEvent', (a, b) => { console.log(a + b) })
emithor.trigger('myEvent', null, 1, 2) // => 3
emithor.trigger('myEvent', null, 2, 2) // => 4
emithor.trigger('myEvent', null, 3, 2) // => 5
emithor.trigger('myEvent', null, 3, 2) // => 5

Trigger events multiple times, while some callbacks will be invoked only once:

const { on, trigger } from 'emithor'

on('myEvent', (a, b) => { console.log(a + b) }, null, true)
on('myEvent', (a, b) => { console.log('myEvent triggered') })
trigger('myEvent', null, 1, 2) 
// => 3
// => 'myEvent triggered'
trigger('myEvent', null, 1, 2) // => 'myEvent triggered'
trigger('myEvent') // => 'myEvent triggered'

Provide this value to the callback:

const { on, trigger } from 'emithor'
const context = { name: 'context' }
const handleMyEvent = function () { console.log(this.name) }

on('myEvent', handleMyEvent, context)
trigger('myEvent') // => 'context'

License

MIT © Vedran Josipovic