選項卡（物件導向）

html:

<div id="div1">
    <input type="button" value="1" class="active">
    <input type="button" value="2">
    <input type="button" value="3">
    <div style="display:block">111</div>
    <div>222</div>
    <div>333</div>
 </div>

css:

#div1 div{width: 200px; height: 200px;border:1px #000 solid; display: none;}
.active{background:#f00;}

js:

// 普通寫法

    window.onload = function () {
        var oParent = document.getElementById(`div1`);
        var aInput = oParent.getElementsByTagName(`input`);
        var aDiv = oParent.getElementsByTagName(`div`);
        for (var i = 0; i < aInput.length; i++) {
            aInput[i].index = i;
            aInput[i].onclick = function () {
                for (var i = 0; i < aInput.length; i++) {
                    aInput[i].className = ``;
                    aDiv[i].style.display = `none`
                }
                this.className = `active`;
                aDiv[this.index].style.display = `block`
            }
        }
    }
    

轉換過程
-先變型 儘量不要出現函式巢狀函式,可以有全域性變數,把onload中不是賦值的語句放到單獨函式中

    var oParent = null;
    var aInput = null;
    var aDiv = null;
    window.onload = function () {
        oParent = document.getElementById(`div1`);
        aInput = oParent.getElementsByTagName(`input`);
        aDiv = oParent.getElementsByTagName(`div`);
        init();
    }

    function init() {
        for (var i = 0; i < aInput.length; i++) {
            aInput[i].index = i;
            aInput[i].onclick = change;
        } 
    }

    function change() {
        for (var i = 0; i < aInput.length; i++) {
            aInput[i].className = ``;
            aDiv[i].style.display = `none`
        }
        this.className = `active`;
        aDiv[this.index].style.display = `block`
    }
    

//改成物件導向
全域性變數就是屬性 函式就是方法 onload中建立物件 改this指向(事件或定時器問題)

    window.onload = function () {
       var t1 = new Tab()
       t1.init();
    }
    function Tab() {
        this.oParent = document.getElementById(`div1`);
        this.aInput = this.oParent.getElementsByTagName(`input`);
        this.aDiv = this.oParent.getElementsByTagName(`div`);
    }
    Tab.prototype.init = function () {
        var This = this;
        for (var i = 0; i < this.aInput.length; i++) {
            this.aInput[i].index = i;
            this.aInput[i].onclick = function (){
                This.change(this);
            }
        } 
    }
    Tab.prototype.change = function (obj) {
        for (var i = 0; i < this.aInput.length; i++) {
            this.aInput[i].className = ``;
            this.aDiv[i].style.display = `none`
        }
        obj.className = `active`;
        this.aDiv[obj.index].style.display = `block`
    }
    

現要求再建立一個選項卡，自動輪播，只需新增div2 修改init和新增一個autoPlay方法

    window.onload = function () {
       var t1 = new Tab(`div1`)
       t1.init();
       var t2 = new Tab(`div2`)
       t2.init();
       t2.autoPlay();
    }
    function Tab(id) {
        this.oParent = document.getElementById(id);
        this.aInput = this.oParent.getElementsByTagName(`input`);
        this.aDiv = this.oParent.getElementsByTagName(`div`);
        this.iNow = 0;
    }

    Tab.prototype.autoPlay = function () {
        var This = this;
        setInterval(function () {
            if(This.iNow == This.aInput.length-1) {
                This.iNow = 0;
            }else {
                This.iNow++;
            }
            for (var i = 0; i < This.aInput.length; i++) {
                This.aInput[i].className = ``;
                This.aDiv[i].style.display = `none`
            }
            This.aInput[This.iNow].className = `active`;
            This.aDiv[This.iNow].style.display = `block`
        }, 2000)
    }