Observer Design Pattern Using JavaScript

Observer.js

/*
Notes:
	Observer	Event	  	Pub/Sub
	add    	   → 	bind       → 	subscribe
	remove 	   → 	unbind     → 	unsubscribe
	notify 	   → 	trigger    → 	publish
	topic  	   → 	type       → 	topic
*/
/**
 * Observer Class
 */
function Observer() {
    this._observers = {};
}

/**
 * @param {Object} observer
 * @param {String} topic
 */
Observer.prototype.addObserver = function(observer, topic) {
    if (!this._observers.hasOwnProperty(topic)) this._observers[topic] = [];
    this._observers[topic].push(observer);
}

/**
 * @param {Object} observer
 * @param {String} topic
 */
Observer.prototype.removeObserver = function(observer, topic) {
    var topics = this._observers[topic] || []
        , l = topics.length
        , i = 0;

    for (; i < l; i++) {
        if (topics[i] === observer) {
            break;
        }
    }

    this._observers[topic].splice(i, 1);
}

/**
 * @param {Object} subject
 * @param {String} topic
 * @param {Object} data
 */
Observer.prototype.notifyObserver = function(subject, topic, data) {
    var topics = this._observers[topic] || []
        , l = topics.length
        , i = 0
	    , subject = subject || window;

    for (; i < l; i++) {
        topics[i].call(subject, data);
    }
}

/**
 * @param {String} topic
 * @return {Array}
 */
Observer.prototype.enumerateObservers = function(topic) {
    return this._observers[topic] || [];
}

// Testing!!!
var o = new Observer();

function f(e) {
    console.log('O1: ' + e);
}

function g(e) {
    console.log('03: ' + e);
}

o.addObserver(f, 'click');

o.addObserver(function(e){
    console.log('O2: ' + e);
}, 'click');

o.addObserver(g, 'click');

var s = {};

o.notifyObserver(s, 'click', 'hello world!');

o.removeObserver(f, 'click');

o.notifyObserver(s, 'click', 'WTF!');