Observer模式

var Observer = (function() {

	var instance = null;

	function Observe() {

		this.events = {}

	}

	Observe.prototype.subscribe = function(eventName, callback) {

		var actions = this.events[eventName];

		if( !actions) {

			actions = this.events[eventName] = [];

		}

		actions.push(callback);

	};

	Observe.prototype.publish = function(eventName) {

		var args = Array.prototype.slice.call(arguments).slice(1);

		var actions = this.events[eventName];

		if(actions) {

			for(var cb in actions) {

				actions[cb].apply(null, args)

			}

		}

		else {

			console.log(eventName || '' + ' is not registered');

		}

	};

	function returnFunction() {

		if(!instance) {

			instance = new Observe();

		}

		return instance;

	}

	returnFunction.toString = function() {

		console.log('Use Observer() to get instance');

	};

	return returnFunction;

})();