javascript之Publish/Subscribe模式

  发布/订阅，是一种由两个部分构成:发布者和订阅者的消息传递模式。发布者将消息发布到特定频道，而订阅者接听频道，当频道上有消息发布时将接收到通知。

1、用javascript实现Pub/Sub模式代码：

var PubSub = {
           //订阅
           subscribe : function(ev,callback){
                this._callback || (this._callback = {});
                (this._callback[ev] || (this._callback[ev] = [])).push(callback);
                return this;
            },
            //取消订阅
            unsubscribe : function(ev){
                if(!this._callback || !this._callback[ev]){
                    return this;
                }
                this._callback[ev] = null;
                delete this._callback[ev];
                return this;
            },
             //发布
            publish : function(){
                var callback, list, i, length, args = [].slice.call(arguments,0), ev = args.shift();
                if(!(callback = this._callback) || !(list = this._callback[ev])){
                    return this;
                }
                for(i = 0, length = list.length; i < length; i++){
                      list[i].apply(this, args);
                }
                return this;
            }
    };
    PubSub.subscribe('wen',function(){alert('Wen!!!');}).publish('wen').unsubscribe('wen').publish('wen');