gistfile1.txt

function observable(obj) {
	obj._events = [];


	obj.on = function (eventName, fn) {
		this._events[eventName] = (this._events[eventName]) ? this._events[eventName] : [];

		this._events[eventName].push({
			fn: fn,
			once: false
		});
	}

	obj.one = function (eventName, fn) {
		this._events[eventName] = (this._events[eventName]) ? this._events[eventName] : [];

		this._events[eventName].push({
			fn: fn,
			once: true
		});
	}

	obj.fire = function (eventName) {
		var args = Array.prototype.slice.call(arguments).slice(1);

		this._events[eventName] = (this._events[eventName]) ? this._events[eventName] : [];
 
		this._events[eventName].forEach(function (listener, index, array) {
			listener.fn.apply(null, args);
			
			if (listener.once) {
				array.splice(index,1);
			}
		});
	}

	obj.unbind = function (eventName, fn) {
		if (!fn) {
			this._events[eventName] = [];
		} else {
			this._events[eventName].forEach(function (listener, index, array) {
				if (fn === listener.fn) {
					array.splice(index,1);
				}
			});
		}
	}
} 

implementation observable pattern