compose-emitter

Fast, lightweight and powerful composition of an EventEmitter with context binding in mind. Pass your emitter instance and context through options and compose on/off/once/emit methods using .compose method.

This package gives you interface with only single method exposed - .compose. You should implement the expected methods using flexible .compose method and passing whatever emitter you want. It's up to you to create your emitter of choice with methods of choice. This just gives you the flexibility and context binding.

Install

npm i compose-emitter --save

Usage

For more use-cases see the tests

const emitter = require('compose-emitter')
// or get constructor
const ComposeEmitter = require('compose-emitter').ComposeEmitter

ComposeEmitter

Initialize ComposeEmitter with options. Pass your EventEmitter instance and optionally pass options.context to bind to listeners.

Params

• options {Object}: Pass event emitter instance to options.emitter.

Example

var ComposeEmitter = require('compose-emitter').ComposeEmitter
var Emitter = require('component-emitter')

var ee = new ComposeEmitter({
  emitter: new Emitter()
})

ee
  .compose('on')('foo', console.log) // => 1, 2, 3
  .compose('emit')('foo', 1, 2, 3)

ComposeEmitter.extend

Extend your application with ComposeEmitter static and prototype methods. See static-extend or tunnckoCore/app-base for more info and what's static and prototype methods are added.

Params

• Parent {Function}: The constructor to extend, using static-extend.

Example

var ComposeEmitter = require('compose-emitter').ComposeEmitter
var Emitter = require('eventemitter3')

function App (options) {
   if (!(this instanceof App)) {
     return new App(options)
   }
  ComposeEmitter.call(this, options)
}

ComposeEmitter.extend(App)

App.prototype.on = function on (name, fn, context) {
  return this.compose('on')(name, fn, context)
}

App.prototype.once = function once (name, fn, context) {
  return this.compose('once')(name, fn, context)
}

App.prototype.off = function off (name, fn, context) {
  return this.compose('off')(name, fn, context)
}

App.prototype.emit = function emit () {
  return this.compose('emit').apply(null, arguments)
}

var app = new App({
  context: {foo: 'bar'},
  emitter: new Emitter()
})

app
  .on('foo', function (a) {
    console.log('foo:', a, this) // => 123, {foo: 'bar'}
  })
  .once('bar', function (b) {
    console.log('bar:', b) // => 456
  })
  .emit('foo', 123)
  .emit('bar', 456)
  .emit('bar', 789)

.compose

Compose different type of emitter methods. You can use this to create the usual .on, .emit and other methods. Pass as type name of the method that your emitter have and optional options to pass context for the listeners.

Params

• type {String}: Name of the emitter method that you want to mirror.
• options {Object}: Optionally pass context that will be bind to listeners.
• returns {Function}: Method that accept as many arguments as you want or emitter method need.

Example

var emitter = require('compose-emitter')
var Emitter = require('eventemitter3')

var on = emitter.compose('on', {
  context: {a: 'b'},
  emitter: new Emitter()
})
var emit = emitter.compose('emit')

on('foo', function (a, b) {
  console.log('foo:', a, b, this) // => 1, 2, {a: 'b', c: 'd'}
}, {c: 'd'})

emit('foo', 1, 2)

Related

• component-emitter: Event emitter | homepage
• define-property: Define a non-enumerable property on an object. | homepage
• eventemitter3: EventEmitter3 focuses on performance while maintaining a Node.js AND browser… more | homepage
• static-extend: Adds a static extend method to a class, to simplify… more | homepage

Contributing

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.
But before doing anything, please read the CONTRIBUTING.md guidelines.

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