设计模式-发布订阅模式

pattern-pubsub.js

// pattern-pubsub.js

var pubsub = {};

(function (ps) {
	var topics = {};  // store topics
	var subId  = -1;  // identify subcribers

	ps.publish = function (topic, args) {
		var subcribers = topics[topic];

		// no subscribes subcribing the topic	
		if (!subcribers) {
			return false;
		}

		for (var i = 0; i < subcribers.length; i++) {
			// notify every subscriber with arguments
			subcribers[i].func(args);
		}

		return this;
	};

	ps.subscribe = function (topic, func) {
		var subcribers = topics[topic];

		// first subscriber!
		if (!subcribers) {
			// init subscribers list
			topics[topic] = [];
		}

		// generate unique id
		var id = ++subId;

		// add this subscriber into the list
		topics[topic].push({
			id: id,
			func: func
		});

		return id;
	};

	ps.unsubscribe = function (id) {
		for(var t in topics) {
			var subcribers = topics[t];
			for (var i = 0; i < subcribers.length; i++) {
				// find the topic with id
				if (subcribers[i].id === id) {
					// delete id
					subcribers.splice(i, 1);

					// find the topic with id, return the id
					return id;
				}
			};
		}

		// do not find the topic with id, just return this
		return this;
	};
})(pubsub);

// subscribe a topic name 'topic1'
var id1 = pubsub.subscribe('topic1', function (args) {
	console.log('topic1', args);
});
// subscribe a topic name 'topic2'
var id2 = pubsub.subscribe('topic2', function (args) {
	console.log('topic2', args);
});


// pubsub the topic 'topic1'
pubsub.publish('topic1', 'hello xiaolai!');
// pubsub the topic 'topic1'
pubsub.publish('topic2', 'hello 赖小赖!');

// now we unsubscribe the 'topic1'
pubsub.unsubscribe(id1);

// pubsub the topic 'topic1'  and 'topic2' again
pubsub.publish('topic1', 'hello xiaolai again!');
pubsub.publish('topic1', 'hello xiaolai again!');

几个优秀的发布订阅库：
http://radio.uxder.com/
https://github.com/mroderick/PubSubJS
https://github.com/phiggins42/bloody-jquery-plugins/blob/55e41df9bf08f42378bb08b93efcb28555b61aeb/pubsub.js
http://amplifyjs.com
https://gist.github.com/826794

发布订阅模式的优点是，可以让多个模块之间解耦，通过事件的形式执行特定的操作，无需关心其他模块的信息