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event-emitter

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 Build Status

$ npm test