Шаблон "Наблюдатель (Подписчик-Издатель)"

Observer.js

var Observer = (function () {
	'use strict';

	var exports = {};

	var events = {},
		splitter =  /\s+/;

	var on = function(types, fn, context) {
		var type;

		types = types.split(splitter);
		type = types.pop();
		context = context || this;

		while (type) {
			events[type] = events[type] || [];
			events[type].push({
				context: context,
				callback: fn
			});
			type = types.pop();
		}

		return this;
	};

	var off = function(types, fn) {
		var type,
			index;

		types = types.split(splitter);
		type = types.pop();

		while (type && type in events) {
			index = events[type].indexOf(fn);
			events[type].splice(index, 1);
			if(events[type].length === 0) {
				delete events[type];
			}
			type = types.pop();
		}

		return this;
	};

	var once = function(types, fn, context) {
		var self = this;

		function handler() {
			self.off(types, handler);
			fn.apply(context, arguments);
		}

		this.on(types, handler, context);

		return this;
	};

	var emit = function(types) {
		var type, args, e,
			subscription,
			len;

		types = types.split(splitter);
		type = types.pop();
		args = Array.prototype.slice.call(arguments, 1);

		while(type && (type in events)) {
			e = events[type];
			for (len = e.length; len > 0; len -= 1) {
				subscription = e[len - 1];
				subscription.callback.apply(subscription.context, args);
			}
			type = types.pop();
		}
	};

	exports.on = on;
	exports.off = off;
	exports.once = once;
	exports.emit = emit;

	return exports;
})();