ak-eventemitter

API

EventEmitter(options)

Constructor.

• options Object

{
  'delimiter': '.' // used to delimite name spaces
}

on(ns, callback[, context, once])

Adds an event listener.

• ns String

Target namespace, wildcard is *, e.g chat.*

• callback Function

function (ns, arg1, arg2, ...) {} see emit().

• context Object [optional]

Context used when calling callback.

• once Boolean [optional]

Privately used by once()

once(ns, callback, context)

Same as on(), triggered only once (removed after first emit()).

off([ns, callback, context])

Removes an event listener.

• ns String [optional]

Target namespace, wildcard is *, e.g chat.*

• callback Function [optional]

function (ns, arg1, arg2, ...) {} see emit().

• context Object [optional]

Context used when calling callback.

---

• If no ns provided, removes all listeners;
• if no callback provided, removes all listeners for given ns;
• if no context provided, remove a listener for given ns and callback;
• if context provided, removes a listener for given ns, callback and context.

emit(ns, ...)

Emits an event.

• ns String [optional]

Target namespace.

• ... Mixed [optional]

Any argument given after ns will be passed to listener's callback. See examples.

Inheritance

See this CoderWall tip.

Examples

Example 1: simple event

var ee = new EventEmitter();

ee.on('someevent', function (ns, val1, val2) {
  console.log(ns, val1, val2);
});

ee.emit('someevent', 123, 'abc'); // -> 'someevent', 123, 'abc'

Example 2: wildcard event

var ee = new EventEmitter();

ee.on('room.*', function (ns, data) {
  console.log(ns, data);
});

ee.emit('room.user.enter', 'john'); // -> 'room.user.enter', 'john'
ee.emit('room.user.leave', 'john'); // -> 'room.user.leave', 'john'
ee.emit('room.topic.update', 'JavaScript is awesome!'); // -> 'room.topic.update', 'JavaScript is awesome!'

Example 3: on, once, off

var ee = new EventEmitter();

ee.on('room.*', function (ns, data) {
  console.log(ns, data);
});

ee.once('room.user.enter', function (ns, user) {
  console.log('Hello ' + user + '! You\'re the first in!');
});

ee.emit('room.user.enter', 'john'); 
// -> 'room.user.enter', 'john'
// -> 'Hello john! You're the first in!'

ee.off('room.*');

ee.emit('room.user.leave', 'john'); // Nothing is logged (because we offed 'room.*')

Example 4: context

var ee = new EventEmitter();
var counter = {
  'enter': 0,
  'leave': 0
};

ee.on('room.user.enter', function (ns) {
  this.enter += 1;
}, counter);

ee.on('room.user.leave', function (ns) {
  this.leave += 1;
}, counter);

ee.emit('room.user.enter', 'john');
ee.emit('room.user.leave', 'mary');
ee.emit('room.user.enter', 'george');
ee.emit('room.user.enter', 'paul');

console.log(counter); // -> {'enter': 3, 'leave': 1}