Emmett

A custom event emitter for Node.js and the browser.

Its aim is to provide its user with a lot of event emitting sugar while remaining lightweight and fast.

Installation

You can install Emmett through npm:

npm install --save emmett

Usage

Creating an emitter

var Emitter = require('emmett');
 
var emitter = new Emitter();

Extending the emitter

Node.js

var util = require('util'),
    Emitter = require('emmett');
 
function MyObject() {
    Emitter.call(this);
}
 
util.inherits(MyObject, Emitter);

ES6 class

import Emitter from 'emmett';
 
class MyObject extends Emitter {
    /* ... */
}

Listening to events

// Basic
emitter.on('eventName', callback);
 
// Once
emitter.once('eventName', callback);
 
// Using ES6 symbol as event name
const sym = Symbol();
emitter.on(sym, callback);
 
// Matching event names with a regex
emitter.on(/^event/, callback);
 
// Options
emitter.on('eventName', callback, {scope: customScope, once: true});
 
// Polymorphisms
emitter.on(['event1', 'event2'], callback);
 
emitter.on({
    event1: callback1,
    event2: callback2
});
 
// Listening to every events
emitter.on(callback);

Event data

Events are objects having the following keys:

• data: the data attached to the event.
• type: the event type.
• target: the event emitter.

emitter.on('myEvent', function(e) {
    console.log(e.data);
});
 
emitter.emit('myEvent', 'Hello World!');
 
// Will print "Hello World!" in the console

Removing listeners

// Basic
emitter.off('eventName', callback);
 
// Removing every listeners attached to the given event
emitter.off('eventName');
 
// Removing the callback from any event
emitter.off(callback);
 
// Polymorphisms
emitter.off(['event1', 'event2'], callback);
 
emitter.off({
    event1: callback1,
    event2: callback2
});
 
// Removing every listeners
emitter.unbindAll();

Emitting

// Basic
emitter.emit('eventName');
 
// With data
emitter.emit('eventName', {hello: 'world'});
 
// Polymorphisms
emitter.emit(['event1', 'event2']);
emitter.emit(['event1', 'event2'], {hello: 'world'});
 
emitter.emit({
    event1: 'hey',
    event2: 'ho'
});

Retrieving listeners

// Return every matching handlers for a given event name
emitter.listeners('eventName');

Disabling an emitter

While disabled, emitting events won't produce nothing.

emitter.disable();
emitter.enable();

Killing an emitter

Killing an emitter will remove all its listeners and make it inoperant in the future.

emitter.kill();

Contribution

Do not hesitate to contribute to the library. Be sure to add and pass any relevant unit test before submitting any code.

# Installing the dev version 
git clone http://github.com/jacomyal/emmett
cd emmett
 
# Installing dependencies 
npm install
 
# Running unit tests 
npm test
 
# Lint the code 
npm run lint