Simple and tiny Observer design pattern implementation written in ES6.

This package is part of quark framework but it can be used independently.

Installation

npm install quark-signal --save

Usage

Basic

Basic example using add() and dispatch() methods.

import Signal from 'quark-signal'

const mySignal = new Signal()

mySignal.add(data => { console.log(data) })
mySignal.dispatch('foo')

Add once

Add a signal listener that will be called only once.

import Signal from 'quark-signal'

const mySignal = new Signal()

mySignal.once(data => { console.log(data) })
mySignal.dispatch('foo')

// It will not be dispatched again
mySignal.dispatch('foo')

Priority

Priorise a listener so that it will be called first when a signal is dispatched. Higher priority listener will be called earlier.

import Signal from 'quark-signal'

const mySignal = new Signal()

mySignal.add(data => { console.log(data) })
mySignal.add(data => { console.log(data) }, { priority: 1 }) // It will be called first

mySignal.dispatch('foo')

Context

Bind a signal listener with a specific context.

import Signal from 'quark-signal'

const obj = {
  foo: 'bar'
}

function callback () {
  console.log(this.foo) // = 'bar'
}

const mySignal = new Signal()

mySignal.add(callback, { context: obj })
mySignal.dispatch()

Propagation

Stop the propagation of a dispatched signal by returning false in a listener.

import Signal from 'quark-signal'

const mySignal = new Signal()

mySignal.add(() => false)
mySignal.add(data => { console.log(data) }) // It will not be called

mySignal.dispatch('foo')

Has

Check if a signal listener exists.

import Signal from 'quark-signal'

const mySignal = new Signal()

const listener = data => { console.log(data) }

mySignal.add(listener)
const listenerExists = mySignal.has(listener) // = true

Remove

Remove a signal listener.

import Signal from 'quark-signal'

const mySignal = new Signal()

const listener = data => { console.log(data) }

mySignal.add(listener)
mySignal.dispatch('foo')
mySignal.remove(listener)

Remove all signal listeners.

import Signal from 'quark-signal'

const mySignal = new Signal()

const listener = data => { console.log(data) }

mySignal.add(listener)
mySignal.add(listener)
mySignal.removeAll()

API

See https://fm-ph.github.io/quark-signal/

Testing

To run the quark-signal tests, first clone the repository and install its dependencies :

git clone https://github.com/fm_ph/quark-signal.git
cd quark-signal
npm install

Then, run the tests with :

npm test

For coverage, use :

npm test:coverage

References

• https://github.com/edankwan/min-signal
• https://github.com/millermedeiros/js-signals
• https://github.com/robertpenner/as3-signals

License

MIT License © Patrick Heng Fabien Motte