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Correction status：qualified
Teacher's comments：尽管是抄的教学案例, 但是如何是搞明白的基础上, 也是不容易的
Collection
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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>tab选项卡</title>
</head>
<style>
ul,li{margin: 0; padding:0; list-style: none;}
a{text-decoration: none; color: cornflowerblue;}
a:hover{text-decoration: #0000ff underline;}
.tab-container{width: 360px; height: 165px;}
.tab-nav{overflow: hidden;}
.tab-nav ul li{float: left; width: 120px; height: 35px; line-height: 35px; text-align: center; cursor: pointer;}
.active{background-color: lightblue;}
.tab-content .detail{line-height: 35px; min-height: 120px; padding: 10px 0 0 20px; display: none;}
.detail.active{display: block;}
</style>
<body>
<p></p>
<div>
<!-- 选项卡的标签导航 -->
<div>
<ul>
<li data-index="1">手机</li>
<li data-index="2">衣服</li>
<li data-index="3">鞋</li>
</ul>
</div>
<!-- 标签导航对应的内容区 -->
<div>
<div class="detail active" data-index="1">
<ul>
<li><a href="">华为mate20</a></li>
<li><a href="">荣耀v20</a></li>
<li><a href="">华为p30</a></li>
</ul>
</div>
<div data-index="2">
<ul>
<li><a href="">T恤</a></li>
<li><a href="">***裤</a></li>
<li><a href="">格子衫</a></li>
</ul>
</div>
<div data-index="3">
<ul>
<li><a href="">阿迪</a></li>
<li><a href="">耐克</a></li>
<li><a href="">NB</a></li>
</ul>
</div>
</div>
</div>
<script>
// 获取标签页导航tab，以及可点击的所有标签页<li>，并转为数据对象
var tabNav = document.getElementsByClassName('tab-nav').item(0);
var tabList = tabNav.firstElementChild.children;
var tabArr = Array.prototype.slice.call(tabList,0);
// 获取所有详情页，并转为数据对象
var detail = document.getElementsByClassName('detail');
var detailArr = Array.prototype.slice.call(detail,0);
// 利用冒泡，进行事件委托
tabNav.addEventListener('click',showDetail,false);
// 监听tab点击事件
function showDetail(ev) {
// 1.清空原导航标签的样式，并设置当前正在被点击的标签页为当前页
tabArr.forEach(function (tab) {
tab.classList.remove('active')
});
ev.target.classList.add('active');
// 清空所在详情页样式，并根据与导航data-index属性的对象关系，显示对应的详情页面
detailArr.forEach(function (detail) {
detail.classList.remove('active')
});
detailArr.forEach(function (detail) {
// 详情页的index与导航标签的index相同时，显示该页面
if(detail.dataset.index ===ev.target.dataset.index){
detail.classList.add('active');
}
})
}
tabNav.addEventListener('mouseover',showDetail,false);
</script>
</body>
</html>