arbitrary-emitter

arbitrary-emitter

Event emitter with Map/Set sugar for modern browsers and node.js (~500 bytes)

arbitrary-emitter stores listeners and actions in Maps, this allows to use arbitrary values as keys for your listeners.

It's written in vanilla ES6, so you will have to transpile it before using it in old browsers or node.js < v5.9

Features

• works in browsers and node.js
• allows to use arbitrary values as keys for listeners
• really small footprint (~500 bytes when gzipped)
• blazing fast
• conventional api (on, off, once and emit)
• on method returns an unsubscription function (like in redux.js)

Usage

Install with npm, clone the repo or download and extract the zip. Then import or insert it as script tag.

const emitter = arbitraryEmitter()
const obj = {}
emitter.on(obj, () => doSomething())
// will `doSomething`
emitter.emit(obj)

Emitter API

on(key, action)

Adds the listener action to the Set for the event tagged with key. key can be any type of value.

on returns removeListener method

const obj = {}
let removeListener = emitter.on(obj, () => doSomething())
emitter.emit(obj) // will `doSomething`
emitter.emit(obj) // will `doSomething`
removeListener()
emitter.emit(obj) // won't do anything

once(key, action)

Adds the listener action to the Set for the event tagged with key. action will be triggered just one time, then it will be removed. key can be any type of value

const obj = {}
emitter.once(obj, () => doSomethingOnce())
emitter.emit(obj) // will `doSomethingOnce`
emitter.emit(obj) // won't do anything

emit(key[, ...args])

Synchronously calls each of the listeners registered for the event tagged with key, and pass the rest of the arguments to them

emitter.on('test', (a, b) => console.log(a + b))
emitter.emit('test', 1, 2) // => 3

off(key[, action])

Remove action from listeners tagged with key. If no action is specified will remove all listeners tagged with key

emitter.off(key, action) // will remove action from listeners
emitter.off(key) // will remove all the listeners tagged with `key`, and the tag itself

Testing

Node

npm test

Browser

Build browser tests (npm run build-tests) and open test/test.html

Building

• Build UMD file: npm run build-umd
• Build browser tests: npm run build-tests
• Run both builds: npm run build

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© 2016 Jacobo Tabernero - Released under MIT License