JavaScript 디자인 패턴 중 관찰자 패턴에 대한 자세한 소개

document.body.addEventListener('click', function () {
    console.log('you clicked me, poor guy!')
});

var dom = $('.dom');
var listener1 = function(e){
    //do one thing
}
var listener2 = function(e){
    //do another thing
}
addEvent(dom,'click',listener1);
addEvent(dom,'click',listener2);

var dom = document.getElementById('dom');
var handler1 = function(e){
    //do one thing
}
var handler2 = function(e){
    //do another thing
}
dom.onclick = handler1;
dom.onclick = handler2;

//定义动画
var Animation = function(){
    this.onStart = new Publisher;  //关于Publisher的设计将在1.3节介绍
    this.onComplete = new Publisher;
    this.onTween = new Publisher;
}
//定义一个原型方法
Animation.prototype.look = function(){
    this.onStart.deliver('animation started!');
    this.onTween.deliver('animation is going on!');
    this.onComplete.deliver('animation completed!');  
};

//实例一个box对象
var box = new Animation();

//定义三个函数作为subscribers
var openBox = function(msg){
    console.log(msg)
}
var checkBox = function(msg){
    console.log(msg)
}
var closeBox = function(msg){
    console.log(msg)
}

//订阅事件
openBox.subscribe(box.onStart);
checkBox.subscribe(box.onTween);
closeBox.subscribe(box.onComplete);

//调用方法
box.look()

//animation started!
//animation is going on!
//animation completed!

function Publisher(){
    this.subscribes = [];
}

Publisher.prototype.deliver = function(data){
    this.subscribes.forEach(function(fn){
        fn(data);
    });
    return this;
}

Function.prototype.subscribe = function(publisher){
    var that = this;
    var alreadyExists = publisher.subscribes.some(function(el){
        return el === that;
    });
    if(!alreadyExists){
        publisher.subscribes.push(this);
    }
    return this;
}

    var scope = (function() {
    //消息列表
    var events = {};
    return {
        //订阅消息
        on:function(name,hander){
            var index = 0;  //记录消息时间的索引
            if(events[name]){  
                //消息名已存在，将处理函数放到该消息的事件队列中
                index = events[name].push(hander) - 1; 
            }else{
                events[name] = [hander];
            }
            //返回当前消息处理事件的移除函数
            return function(){
                events[name].splice(index,1);
            }
        },
        //关闭消息
        off:function(name){
            if(!events[name]) return;
            //消息存在，删除消息
            delete events[name];
        },
        //消息发布
        emit:function(name,msg){
            //消息不存在，不处理
            if(!events[name]) return;
            //消息存在，将该事件处理队列中每一个函数都执行一次
            events[name].forEach(function(v,i){
                v(msg);
            });
        }
    }
})();

var sayHello = scope.on('greeting',function(msg){
    console.log('订阅消息：' + msg);
});

var greeting = function(msg){
    console.log('发布消息：' + msg);
    scope.emit('greeting', msg);
}

greeting('hello Panfen!')

var EventEmitter = require('events').EventEmitter;
var life = new EventEmitter();
life.setMaxListeners(11);       //设置最大监听数，默认10

//发布和订阅sendName
life.on('sendName',function(name){
    console.log('say hello to '+name);
});
life.emit('sendName','jeff');

//发布和订阅sendName2
function sayBeautiful(name){
    console.log(name + ' is beautiful');
}
life.on('sendName2',sayBeautiful);
life.emit('sendName2','jeff');