SYNOPSIS

EventEmitter2 is an implementation of the EventEmitter module found in Node.js. In addition to having a better benchmark performance than EventEmitter and being browser-compatible, it also extends the interface of EventEmitter with additianal non-breaking features.

DESCRIPTION

FEATURES

• Namespaces/Wildcards.
• Times To Listen (TTL), extends the once concept with many.
• Browser environment compatibility.
• Demonstrates good performance in benchmarks

EventEmitterHeatUp x 3,728,965 ops/sec \302\2610.68% (60 runs sampled)
EventEmitter x 2,822,904 ops/sec \302\2610.74% (63 runs sampled)
EventEmitter2 x 7,251,227 ops/sec \302\2610.55% (58 runs sampled)
EventEmitter2 (wild) x 3,220,268 ops/sec \302\2610.44% (65 runs sampled)
Fastest is EventEmitter2

Differences (Non-breaking, compatible with existing EventEmitter)

• The EventEmitter2 constructor takes an optional configuration object.

    var EventEmitter2 = require('eventemitter2').EventEmitter2;
    var server = new EventEmitter2({

      //
      // set this to `true` to use wildcards. It defaults to `false`.
      //
      wildcard: true,

      //
      // the delimiter used to segment namespaces, defaults to `.`.
      //
      delimiter: '::', 
      
      //
      // set this to `true` if you want to emit the newListener event. The default value is `true`.
      //
      newListener: false, 

      //
      // the maximum amount of listeners that can be assigned to an event, default 10.
      //
      maxListeners: 20
    });

• Getting the actual event that fired.

    server.on('foo.*', function(value1, value2) {
      console.log(this.event, value1, value2);
    });

• Fire an event N times and then remove it, an extension of the once concept.

    server.many('foo', 4, function() {
      console.log('hello');
    });

• Pass in a namespaced event as an array rather than a delimited string.

    server.many(['foo', 'bar', 'bazz'], function() {
      console.log('hello');
    });

API

When an EventEmitter instance experiences an error, the typical action is to emit an error event. Error events are treated as a special case. If there is no listener for it, then the default action is to print a stack trace and exit the program.

All EventEmitters emit the event newListener when new listeners are added.

Namespaces with Wildcards To use namespaces/wildcards, pass the wildcard option into the EventEmitter constructor. When namespaces/wildcards are enabled, events can either be strings (foo.bar) separated by a delimiter or arrays (['foo', 'bar']). The delimiter is also configurable as a constructor option.

An event name passed to any event emitter method can contain a wild card (the * character). If the event name is a string, a wildcard may appear as foo.*. If the event name is an array, the wildcard may appear as ['foo', '*'].

If either of the above described events were passed to the on method, subsequent emits such as the following would be observed...

   emitter.emit('foo.bazz');
   emitter.emit(['foo', 'bar']);

Multi-level Wildcards

A double wildcard (the string **) matches any number of levels (zero or more) of events. So if for example 'foo.**' is passed to the on method, the following events would be observed:

    emitter.emit('foo');
    emitter.emit('foo.bar');
    emitter.emit('foo.bar.baz');

On the other hand, if the single-wildcard event name was passed to the on method, the callback would only observe the second of these events.

emitter.addListener(event, listener)

emitter.on(event, listener)

Adds a listener to the end of the listeners array for the specified event.

    server.on('data', function(value1, value2, value3, ...) {
      console.log('The event was raised!');
    });

    server.on('data', function(value) {
      console.log('The event was raised!');
    });

emitter.onAny(listener)

Adds a listener that will be fired when any event is emitted.

    server.onAny(function(value) {
      console.log('All events trigger this.');
    });

emitter.offAny(listener)

Removes the listener that will be fired when any event is emitted.

    server.offAny(function(value) {
      console.log('The event was raised!');
    });

emitter.once(event, listener)

Adds a one time listener for the event. The listener is invoked only the first time the event is fired, after which it is removed.

    server.once('get', function (value) {
      console.log('Ah, we have our first value!');
    });

emitter.many(event, timesToListen, listener)

Adds a listener that will execute n times for the event before being removed. The listener is invoked only the first n times the event is fired, after which it is removed.

    server.many('get', 4, function (value) {
      console.log('This event will be listened to exactly four times.');
    });

emitter.removeListener(event, listener)

emitter.off(event, listener)

Remove a listener from the listener array for the specified event. Caution: Calling this method changes the array indices in the listener array behind the listener.

    var callback = function(value) {
      console.log('someone connected!');
    };
    server.on('get', callback);
    // ...
    server.removeListener('get', callback);

emitter.removeAllListeners([event])

Removes all listeners, or those of the specified event.

emitter.setMaxListeners(n)

By default EventEmitters will print a warning if more than 10 listeners are added to it. This is a useful default which helps finding memory leaks. Obviously not all Emitters should be limited to 10. This function allows that to be increased. Set to zero for unlimited.

emitter.listeners(event)

Returns an array of listeners for the specified event. This array can be manipulated, e.g. to remove listeners.

    server.on('get', function(value) {
      console.log('someone connected!');
    });
    console.log(server.listeners('get')); // [ [Function] ]

emitter.listenersAny()

Returns an array of listeners that are listening for any event that is specified. This array can be manipulated, e.g. to remove listeners.

    server.onAny(function(value) {
      console.log('someone connected!');
    });
    console.log(server.listenersAny()[0]); // [ [Function] ]

emitter.emit(event, [arg1], [arg2], [...])

Execute each of the listeners that may be listening for the specified event name in order with the list of arguments.

LICENSE

(The MIT License)

Copyright (c) 2011 hij1nx http://www.twitter.com/hij1nx

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.