EventEmitter – Cross-environment event emitter solution for JavaScript

Usage

var ee = require('event-emitter');

var emitter = ee({}), listener;

emitter.on('test', listener = function (args) {
  // …emitter logic
});

emitter.once('test', function (args) {
  // …invoked only once(!)
});

emitter.emit('test', arg1, arg2/…args/); // Two above listeners invoked
emitter.emit('test', arg1, arg2/…args/); // Only first listener invoked

emitter.off('test', listener);              // Removed first listener
emitter.emit('test', arg1, arg2/…args/); // No listeners invoked

Installation

NPM

In your project path:

$ npm install event-emitter

Browser

Browser bundle can be easily created with help of modules-webmake. Assuming that you have latest Node.js and Git installed, following will work in command shell of any system (Linux/MacOS/Windows):

$ npm install -g webmake
$ git clone git://github.com/medikoo/event-emitter.git
$ cd event-emitter
$ npm install
$ cd ..
$ webmake --name=eventEmitter event-emitter/lib/index.js event-emitter.js

If you work with AMD modules, add amd option, so generated bundle is one:

$ webmake --name=eventEmitter --amd event-emitter/lib/index.js event-emitter.js

Mind that eventEmitter relies on some EcmaScript5 features, so for older browsers you need to load as well es5-shim

Functionalities provided as separate modules

allOff(obj)

Remove all listeners

var eeAllOff = require('event-emitter/lib/all-off');
eeAllOff(emitter); // Removed all registered listeners on emitter

unify(emitter1, emitter2)

Unify listeners database of two emitter. Events emitted on either emitter will call listeners attached to emitter object

var eeUnify = require('event-emitter/lib/unify');

var emitter1 = ee(), listener1, listener3;
var emitter2 = ee(), listener2, listener4;

emitter1.on('test', listener1 = function () { });
emitter2.on('test', listener2 = function () { });

emitter1.emit('test'); // Invoked listener1
emitter2.emit('test'); // Invoked listener2

var unify = eeUnify(emitter1, emitter2);

emitter1.emit('test'); // Invoked listener1 and listener2
emitter2.emit('test'); // Invoked listener1 and listener2

emitter1.on('test', listener3 = function () { });
emitter2.on('test', listener4 = function () { });

emitter1.emit('test'); // Invoked listener1, listener2, listener3 and listener4
emitter2.emit('test'); // Invoked listener1, listener2, listener3 and listener4

hasListeners(obj[, type])

Whether given object have registered listeners

var emitter = ee();
var hasListeners = require('event-emitter/lib/has-listeners');
var listener = function () {};

hasListeners(emitter); // false

emitter.on('foo', listener);
hasListeners(emitter); // true
hasListeners(emitter, 'foo'); // true
hasListeners(emitter, 'bar'); // false

emitter.off('foo', listener);
hasListeners(emitter, 'foo'); // false

Tests

$ npm test

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