JS實現觀察者模式

時間 2019-11-17

原文原文鏈接

感謝自學IT網的燕十八老師 javascript

<!DOCTYPE HTML>
<html>
<head>
    <meta http-equiv="content-type" content="text/html; charset=utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>觀察者模式</title>
    <style type="text/css" media="all">
        #sec{
            margin:20px;
        }
        #cont,#ad,#study{
            width:400px;
            height:200px;
            margin:10px;
            border:1px solid #ccc;
        }
    </style>
    
</head>
<body>
    <div class='container'>
        <select name="" id="sec">
            <option value='male'>男性</option>
            <option value='famale'>女性</option>
        </select>
        &nbsp;
        <input type='button' value='觀察尾部' onclick='t1()' />
        <input type='button' value='不觀察尾部' onclick='t2()' />
        <div id='cont'>這裏是內容</div>
        <div id='ad'>這裏是廣告</div>
        <div id='study'>這裏是學習</div>
    </div>
</body>
    <script type="text/javascript" charset="utf-8">
        var sec = document.getElementById('sec');
        var ad = document.getElementById('ad');
        var cont = document.getElementById('cont');
        var study = document.getElementById('study');

        sec.observers = {};
        sec.attach = function(key,obj){
            this.observers[key] = obj;
        }

        sec.detach = function(key){
            delete sec.observers[key];
        }

        sec.onchange = sec.notify = function(){
            for(var key in this.observers){
                this.observers[key].update(this);
            }
        }

        cont.update = function(observer){
            if (observer.value=='male') 
            {
                this.style.backgroundColor = 'gray';
            }else if (observer.value=='famale'){
                this.style.backgroundColor = 'pink';
            }
        }

        ad.update = function(observer){
            if (observer.value=='male') 
            {
                this.innerHTML = '汽車';
            }else if (observer.value=='famale'){
                this.innerHTML = '減肥';
            }
        }

        study.update = function(observer){
            if (observer.value=='male') 
            {
                this.innerHTML = '電腦';
            }else if (observer.value=='famale'){
                this.innerHTML = '化妝';
            }
        }

        // 監聽
        sec.attach('cont',cont);
        sec.attach('ad',ad);
        sec.attach('study',study);

        function t1(){
            // 觀察尾部
            sec.attach('study',study);
        }

        function t2(){
            // 不觀察尾部
            sec.detach('study');
        }
    </script>
</html>