event-emitter
Environment agnostic event emitter
Installation
$ npm install event-emitter
To port it to Browser or any other (non CJS) environment, use your favorite CJS bundler. No favorite yet? Try: Browserify, Webmake or Webpack
Usage
var ee = require('event-emitter'); var MyClass = function () { /* .. */ }; ee(MyClass.prototype); // All instances of MyClass will expose event-emitter interface var emitter = new MyClass(), listener; emitter.on('test', listener = function (args) { // … react to 'test' event }); emitter.once('test', function (args) { // … react to first 'test' event (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
Additional utilities
allOff(obj) (event-emitter/all-off)
Removes all listeners from given event emitter object
hasListeners(obj[, name]) (event-emitter/has-listeners)
Whether object has some listeners attached to the object.
When name is provided, it checks listeners for specific event name
var emitter = ee(); var hasListeners = require('event-emitter/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
pipe(source, target[, emitMethodName]) (event-emitter/pipe)
Pipes all events from source emitter onto target emitter (all events from source emitter will be emitted also on target emitter, but not other way).
Returns pipe object which exposes pipe.close function. Invoke it to close configured pipe.
It works internally by redefinition of emit method, if in your interface this method is referenced differently, provide its name (or symbol) with third argument.
unify(emitter1, emitter2) (event-emitter/unify)
Unifies event handling for two objects. Events emitted on emitter1 would be also emitted on emitter2, and other way back.
Non reversible.
var eeUnify = require('event-emitter/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
Tests 
$ npm test