Event.js - Small event pub/sub library

Event.js tries to plug the gaps in other event pub/sub bind/trigger or whatever-method-you-use libraries. It's extremely simple, but shouldn't do anything you don't expect.

Usage

Let's start by require()ing Event.js and creating an instance:

Vent    = require('EventJS');
MyEvent = new Vent();

Subscribing to an event

To subscribe a callback to an event, simply use subscribe(name, callback):

MyEvent.subscribe('test', myCallback);

If you are using the method of a particular object, then use the bind argument:

MyEvent.subscribe('test', myFoo.myCallback, myFoo);

This will ensure that myFoo.myCallback is bound to myFoo when it is called. Do not use Vent.subscribe('test', myFoo.myCallback.bind(myFoo)), as this causes problems when we try to unsubscribe events.

Unsubscribing from an event

To unsubscribe, you must use exactly the same call signature you use for subscribe, but this time for unsubscribe:

MyEvent.unsubscribe('test', myCallback);

Or, if you subscribed an instance method:

MyEvent.unsubscribe('test', myFoo.myCallback, myFoo);

Publishing events

To notify all the subscribers, use the publish method:

MyEvent.publish('test', 'Hello');

This will call each subscribed callback with a single argument, "Hello". To add more arguments, just put them in the call signature:

MyEvent.publish('test', 'Hello', 'World');

This will call each subscribed callback with two arguments, "Hello" and "World".

Implementing functionality on your own class

Event.js can implement the pub/sub functionality on any other class using the implementOn class method:

Vent.implementOn(MyClass.prototype);

Then you can use it as before:

var myInstance = new MyClass();

myInstance.subscribe(/* ... */);
// ... and so on

Some things this fixes

My primary motivation for writing Event.js was that it fixed some problems I was having in some other libraries. When unsubscribing one instance's callback I often found that this would unsubscribe all the instances' callbacks, or fail to recognise the instance/callback combination, because I had to use callback.bind(obj). The way Event.js does things, by having a separate bind argument, avoids problems with this, which are related to the way .bind() works (it creates a new function, so equality tests always fail).