Publish/subscribe module

events.js

/**
 * A simple Publish/subscribe javascript module based on code by David Walsh:
 * http://davidwalsh.name/pubsub-javascript
 */
var events = (function(){
	// Holds the subscribed topics.
	var topics = {};

	return {
		subscribe: function( topic, callback ) {
			// Create the topic's object if not yet created.
			if( ! topics[topic] ) {
				topics[topic] = { subscribers: [] };
			}

			// Add the callback to subscribers list.
			var index = topics[topic].subscribers.push( callback ) - 1;

			// Remove subscriber from a topic.
			return {
				remove: function() {
					delete topics[topic].subscribers[index];
				}
			};
		},

		publish: function(topic, info) {
			// Return early if the topic doesn't exist, or there are no subscribers.
			if( ! topics[topic] || ! topics[topic].subscribers.length ) {
				return;
			}

			// Cycle through topics subscribers, fire! 
			var items = topics[topic].subscribers;

			for ( var i = 0, len = items.length; i < len; i++ ) {
				items[i]( info || {} );
			}
		}
	};
})();