二分之一

没空讲原理了，写了一个DEMO供大家学习，先上一段核心代码，然后附上DEMO。

请查看DEMO，更详细的理解Observer（观察者）模式

DEMO:test.html

/**************订阅者/观察者/subscribe************/
function ObserverList(){
    this.observerList = [];
};

//添加
ObserverList.prototype.Add = function(obj){
    if(this.IndexOf(obj,0)==-1){
        return this.observerList.push(obj);
    }else{
        this.observerList;
    }
};

//清空
ObserverList.prototype.Empty = function(){
    this.observerList = [];
};

//统计
ObserverList.prototype.Count = function(){
    return this.observerList.length;
};

//获取
ObserverList.prototype.Get = function(index){
    if(index>-1 && index<this.observerList.length){
        return this.observerList[index];
    }
};

//插入
ObserverList.prototype.Insert = function(obj,index){
    var pointer = -1;
    if(index===0){
        this.observerList.unshift(obj);
        pointer = index;
    }else if(index === this.observerList.length){
        this.observerList.push(obj);
        pointer = index;
    }
    return pointer;
};

//查询位置
ObserverList.prototype.IndexOf = function(obj,startIndex){
    var i = startIndex,pointer = -1;
    while(i<this.observerList.length){
        if(this.observerList[i]===obj){
            pointer = i;
        }
        i++;
    }
    return pointer;
};

ObserverList.prototype.RemoveIndexAt = function(index){
    if(index===0){
        this.observerList.shift();
    }else if(index===this.observerList.length-1){
        this.observerList.pop();
    }else{
        this.observerList.splice(index,1);
    }
}

//扩展对象
function extend(obj,extension){
    for(var key in obj){
        extension[key] = obj[key];
    }
}

/**************发布者/目标/publish****************/
function Subject(){
    this.observers = new ObserverList();
}

Subject.prototype.AddObserver = function(observer){
    this.observers.Add(observer);
};

Subject.prototype.RemoveObserver = function(observer){
    this.observers.RemoveIndexAt(this.observers.IndexOf(observer,0));
    console.log(this.observers);
};

Subject.prototype.Notify = function(context){
    var observerCount = this.observers.Count();
    for(var i=0;i<observerCount;i++){
        this.observers.Get(i).Update(context);
    }
};

最后修改时间：2014年9月10日星期三晚上8点35