tab栏切换制作这个是重点一定要会

这个是重点一定要会
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        .tab {
            width: 1200px;
            margin: 200px auto;
        }
        
        .tab_list {
            width: 1200px;
            height: 30px;
            background-color: #EFF0EF;
            border: 1px solid #D5D6D4;
        }
        
        .tab_list li {
            width: 240px;
            height: 30px;
            line-height: 30px;
            float: left;
            list-style: none;
            text-align: center;
            /* margin: 0 10px; */
            cursor: default;
        }
        
        .current {
            background-color: #D72720;
            color: #fff;
            /* display: block; */
        }
        
        .item {
            display: none;
        }
        
        .tab_con div:first-child {
            display: block;
        }
    </style>
</head>
<body>
    <div class="tab">
        <div class="tab_list">
            <ul>
                <li class="current">商品介绍</li>
                <li>规格与包装</li>
                <li>售后保障</li>
                <li>商品评价（500+）</li>
                <li>手机社区</li>
            </ul>
        </div>
        <div class="tab_con">
            <div class="item ">
                商品介绍模块内容1
            </div>
            <div class="item">
                商品介绍模块内容2
            </div>
            <div class="item">
                商品介绍模块内容3
            </div>
            <div class="item">
                商品介绍模块内容4
            </div>
            <div class="item">
                商品介绍模块内容5
            </div>
        </div>
    </div>
    <script>
        var lis = document.querySelector('.tab_list').getElementsByTagName('li');
        var items = document.querySelector('.tab_con').querySelectorAll('.item');
        for (var i = 0; i < lis.length; i++) {
            lis[i].setAttribute('index', i);
            lis[i].onclick = function() {
                // console.log('aaa');
                for (var i = 0; i < lis.length; i++) {
                    lis[i].className = '';
                }
                this.className = 'current';

                var index = this.getAttribute('index');
                // console.log(index);

                for (var j = 0; j < items.length; j++) {
                    items[j].style.display = 'none';
                }
                // console.log(index);
                items[index].style.display = 'block';
            }
        }
    </script>
</body>