js设计模式之实现观察者模式实例代码

时间：2020-01-12 10:14:07 收藏：0 阅读：87

前端界面

技术分享图片

html代码

<body>
    <select name="" id="select">
        <option value="">请选择风格</option>
        <option value="male">男式风格</option>
        <option value="female">女士风格</option>
    </select>
    <button onclick="t1();">观察学习区</button>
    <button onclick="t2();">不观察学习区</button>
    <div id="content">内容区</div>
    <div id="ad">广告区</div>
    <div id="study">学习区</div>
</body>

css样式

<style>
#content,#ad,#study{
    width: 498px;
    height: 150px;
    border:1px solid #333;
    margin-top: 10px;
}

</style>

js代码

<script>
    var sel = document.getElementById("select");
    // console.log(sel)
    sel.objs = {}
    sel.attach = function(key,obj){
        this.objs[key] = obj;
    }
    sel.delAttach = function(key){
        delete this.objs[key];
    }

    sel.onchange = function(){
        for(var key in this.objs){
            this.objs[key].update(this)
        }
    }

    // 客户端
    var content = document.getElementById(‘content‘)
    var ad = document.getElementById(‘ad‘)
    var study = document.getElementById(‘study‘)
    content.update = function(objs){
        if (objs.value == ‘male‘) {
            content.style.backgroundColor = "blue";
        }else if (objs.value == ‘female‘) {
            content.style.backgroundColor = "pink";
        }else{
            content.style.backgroundColor = "";
        }
    }
    ad.update = function(objs){
        if (objs.value == ‘male‘) {
            ad.innerHTML = "汽车";
        }else if (objs.value == ‘female‘) {
            ad.innerHTML = "减肥";
        }else{
            ad.innerHTML = "广告区";
        }
    }
    study.update = function(objs){
        if (objs.value == ‘male‘) {
            study.innerHTML = "学习编程";
        }else if (objs.value == ‘female‘) {
            study.innerHTML = "学习美工";
        }else{
            study.innerHTML = "学习区";
        }
    }
    sel.attach(‘content‘,content);
    sel.attach(‘ad‘,ad);
    sel.attach(‘study‘,study);
    function t1(){
        sel.attach(‘study‘,study)
    }
    function t2(){
        sel.delAttach(‘study‘)
    }
</script>

原文：https://www.cnblogs.com/Mishell/p/12182010.html