【经验总结】简陋无比的观察者模式实现

 说明：观察者模式超级简陋版，代码很简单

主要实现代码如下：

//简单的工具对象，实现了观察者模式所需的基本要素
var publisher = {

    whateverType: 'any',
    subscribers:{
        //'any': []    //当不指定订阅类型时，统统扔到这个默认的队列里去
    },
    
    //订阅事件，type：事件类型，handler：事件处理方法
    subscribe: function(type, handler){
        type = type || whateverType;
        if(typeof this.subscribers[type]==='undefined'){
            this.subscribers[type] = [];
        }
        this.subscribers[type].push(handler);
    },
    
    //停止订阅事件，type：事件类型，[handler]：事件处理方法（如不传，则将类型为type的事件订阅队列清空）
    unsubscribe: function(type, handler){
        type = type || whateverType;
        var subscribers = this.subscribers[type] || [];
        for(var i=0; i<subscribers.length; i++){
            if(!handler || subscribers[i]===handler){
                subscribers.splice(i, 1);
                i--;
            }
        }
    },
    
    //发布事件，type：事件类型，[param]：事件参数，格式可自行定义
    publish: function(type, param){
        type = type || whateverType;
        var subscribers = this.subscribers[type] || [];
        for(var i=0,len=subscribers.length; i<len; i++){
            subscribers[i](param);
        }        
    }
};

接下来随便写两个对象，一个做发布者，一个做订阅者吧（一下子想到了老师给学生布置作业神马的。。。）

//工具函数，将source对象的属性拷贝到target里
function extend(target, source){
    for( var key in source) target[key] = source[key];
}

//仁慈的老师
var Teacher = {};
extend(Teacher, publisher);

//听话的学生
var Student = {
    doHomework: function(){
        console.log('homework, i wanna die');
    },
    takeExam: function(param){
        console.log('just '+ param.week_left +' weeks before final exams ! wtf');
    }
};

简单的测试用例，非详细：

Teacher.subscribe('homework', Student.doHomework);
Teacher.subscribe('exam', Student.takeExam);

Teacher.publish('homework');    //homework, i wanna die 
Teacher.publish('exam', {week_left: 2});    //just 2 weeks before final exams ! wtf 

Teacher.unsubscribe('homework', Student.doHomework);

Teacher.publish('homework');
Teacher.publish('exam', {week_left: 2});    //just 2 weeks before final exams ! wtf 

观察者模式的简陋实现，代码很简单，思路也不复杂，根据需要稍加修改应该就可以用到实际项目中去，对于项目模块的通信、解耦都有很大作用...省略n字...