Telegraph

A minimal event emitter for browsers, forked from Benjamin Thomas' smokesignals.js.

This library has three goals:

1. Make it easy and intuitive to listen for and initiate events on an object.
2. Be as small as possible. Right now the minified version comes in at 528 bytes.
3. Capability for handlers to cancel the event process.

There are many other wonderful libraries that do similar things, but none of them worked exactly how I wanted them to work or met all the goals above.

Installing

Just download telegraph.js and put it in a place you can access from your webpage.

Loading

Just include the Telegraph script:

<script src="telegraph.js"></script>

Using

Make any object an event emitter:

var jill = {};
telegraph(jill);

// or...
var jill = telegraph();

Or if you prefer constructors:

function Person() {
    telegraph(this);
}
var jill = new Person();

Now you can listen for events:

function listener(name) {
    window.alert('Hello ' + name + '!');
}
jill.on('say hello', listener);

And emit events:

jill.emit('say hello', 'Jack');
// alerts: "Hello Jack!"
// returns: true

And remove a listener:

jill.off('say hello', listener);

Or if you only want to listen for an event once:

jill.once('another event', function() {
    window.alert("I'll only be called once!");
});
jill.emit('another event');

Or remove all listeners for an event:

jill.off('say hello');

Or if you want to remove ALL listeners:

// just call off() with no parameters
jill.off();

// or reconvert the object...
telegraph(jill);

Or if you want to cancel the event chain:

// just return false from a handler
jill.on('event', function() { return false; });
jill.on('event', function() { console.log('event!'); });

// emit now returns false, and 'event!' is not printed
jill.emit('event');

That's it! One global object (telegraph) and when used it adds 4 methods to your objects (on, once, off and emit).

By the way, all methods, except for emit, are chainable:

var jill = telegraph()
    .on('event one', function() { ... })
    .on('event two', function() { ... })
    .once('event three', function() { ... })
    .off ('event one');