extended-emitter.js

Everything you expect from require('events').EventEmitter in both the browser and client, plus:

criteria : use a sift expression to work on a subset of the events
.allOff() : removes all events from this emitter
.emitter : the internal emitter used, in case you need direct access.

import

CommonJS

const { Emitter } = require('extended-emitter');
const emitter = new Emitter();

ES6 imports

import { Emitter } from 'extended-emitter';
const emitter = new Emitter();

optional criteria

you can now using mongo-style queries (supported by sift) to subscribe to specific events (in this context .once() means meeting the criteria, not just firing an event of that type).

emitter.on('my_object_event', {
    myObjectId : object.id
}, function(){
    //do stuff here
});

// or

emitter.once('my_object_event', {
    myObjectId : object.id,
    myObjectValue : {
    	$gt : 20,
    	$lt : 40
    }
}, function(){
    //do stuff here
});

.when()

and there's also the addition of a when function which can take ready-style functions, real promises or events, making it easy to delay or wait for a state, without resorting to chaining.

async

await emitter.when([$(document).ready, 'my-init-event', 'my-load-event']);

callbacks

emitter.when([$(document).ready, 'my-init-event', 'my-load-event'], function(){
	//do stuff
});

.onto()

Often you want an object to implement emitters, and while it's easy enough to wrap them, why not just have that done for you and avoid the boilerplate?

emitter.onto(MyClass.prototype);
emitter.onto(MyInstance);
emitter.onto(MyObject);

or in the constructor:

(new Emitter()).onto(this);

Testing

Run the tests at the project root with:

npm run import-test
npm run require-test

Enjoy,

-Abbey Hawk Sparrow

khrome/extended-emitter