JavaScript模拟实现新浪下拉菜单效果

思考：首先在CSS布局上就出错了，导致后面设置JS时就有很大的问题

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .nav {
            background-color: rgb(235, 225, 225);
            line-height: 30px;
            height: 30px;
            position: relative;
        }

        ul {
            margin: 0px 0px;
            padding: 0 0 0 0;
        }

        .nav1 li,
        .nav2 li,
        .nav3 li {
            display: block;
            padding-left: 10px;
            height: 20px;
            padding-top: 5px;
            padding-bottom: 5px;
            border: 1px solid orange;
            margin-top: -1px;
        }

        .nav1,
        .nav2,
        .nav3 {
            display: none
        }

        .nav1 {
            background-color: white;
            width: 80px;
            position: absolute;
            top: 0px;
            left: 0px
        }

        .nav2 {
            background-color: white;
            width: 100px;
            position: absolute;
            top: 0px;
            left: 80px
        }

        .nav3 {
            background-color: white;
            width: 120px;
            position: absolute;
            top: 0px;
            left: 160px
        }

        .nav div {
            width: 80px;
            text-align: center;
            line-height: 30px;
            float: left
        }

        .tort {
            position: relative;
            left: 0px
        }

        .se {
            background-color: rgb(201, 192, 192);
            color: orange
        }

        ul li:hover {
            background-color: orange;
        }
    </style>
</head>

<body>
    <div class="nav">
        <div>微博</div>
        <div>博客</div>
        <div>邮箱</div>
    </div>
    <div class="tort">
        <div class="nav1">
            <ul>
                <li>私信</li>
                <li>评论</li>
                <li>@我</li>
            </ul>
        </div>
        <div class="nav2">
            <ul>
                <li>博客评论</li>
                <li>未读提醒</li>
            </ul>
        </div>
        <div class="nav3">
            <ul>
                <li>免费邮箱</li>
                <li>VIP邮箱</li>
                <li>企业邮箱</li>
                <li>新浪客户邮箱</li>
            </ul>
        </div>
    </div>
    <script>
        //获得导航栏元素
        var nav = document.querySelector('.nav')
            //注册下拉事件点击的时候，对应的下拉菜单就是显示的（一一对应）因此需要索引号
            //给na.children即下面的所有li设置自定义属性
            //用不着，因为下面下拉菜单都进行了分别命名，但这样就不能用循环了
        nav.children[0].setAttribute('data-index', '0')
        nav.children[1].setAttribute('data-index', '1')
        nav.children[2].setAttribute('data-index', '2')
        var nav1 = document.querySelector('.nav1')
        var nav2 = document.querySelector('.nav2')
        var nav3 = document.querySelector('.nav3')
            //获取下拉菜单子元素
            //应该用data-index来获取
            // var tort = document.querySelector('.tort')
            // nav1.setAttribute('data-idn', '0')
            // nav2.setAttribute('data-idn', '1')
            // nav3.setAttribute('data-idn', '2')

        // var nn =
        // console.log(nn)
        //添加事件
        for (var i = 0; i < nav.children.length; i++) {
            nav.children[i].onmouseover = function() {
                this.className = 'se'
            }
            nav.children[i].onmouseout = function() {
                    this.className = ''
                }
                //添加下拉菜单显示属性

        }
        // nav.children[0].onmouseover = function() {
        //     nav1.style.display = 'block'
        //     nav2.style.display = ''
        //     nav3.style.display = ''
        // }
        // nav.children[1].onmouseover = function() {
        //     nav2.style.display = 'block'
        //     nav1.style.display = ''
        //     nav3.style.display = ''
        // }
        // nav.children[2].onmouseover = function() {
        //     nav3.style.display = 'block'
        //     nav2.style.display = ''
        //     nav1.style.display = ''
        // }
    </script>

</body>

</html>

导航栏里面的li都要有鼠标经过的效果，所以需要循环注册事件

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .nav li {
            list-style: none;
        }

        .nav>li>a:hover {
            background-color: #eee;
        }

        .nav ul {
            display: block;
            position: absolute;
            top: 41px;
            left: 0px;
            width: 100%;
            border-left: 1px solid #fecc5b;
            border-right: 1px solid #fecc5b
        }

        .nav ul li {
            border-bottom: 1px solid #fecc5b;
        }

        .nav ul li a:hover {
            background-color: #fff5da;
        }

        .m1 {
            position: absolute;
            top: 0px;
            left: 0px;
        }

        .m1 {
            position: absolute;
            top: 0px;
            left: 20px;
        }
    </style>
</head>

<body>
    <ul class="nav">
        <li>
            <a href="#" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >微博</a>
            <ul class="m1">
                <li><a href="">私信</a>
                </li>
                <li><a href="">评论</a></li>
                <li><a href="">@我</a></li>

            </ul>
        </li>
        <li>
            <a href="#" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >微博</a>
            <ul>
                <li><a href="">私信</a>
                </li>
                <li><a href="">评论</a></li>
                <li><a href="">@我</a></li>
            </ul>
        </li>
        <li>
            <a href="#" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >微博</a>
            <ul class="m1">
                <li><a href="">私信</a>
                </li>
                <li><a href="">评论</a></li>
                <li><a href="">@我</a></li>
            </ul>
        </li>
        <li>
            <a href="#" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >微博</a>
            <ul>
                <li><a href="">私信</a>
                </li>
                <li><a href="">评论</a></li>
                <li><a href="">@我</a></li>
            </ul>
        </li>
    </ul>
    <script>
        //获取元素
        var nav = document.querySelector('.nav')
        var lis = nav.children
            //循环注册事件
        for (var i = 0; i < lis.length; i++) {
            lis[i].onmouseover = function() {
                this.children[1].style.display = 'block'

            }
            lis[i].onmouseout = function() {
                this.children[1].style.display = ''

            }
        }
    </script>
</body>

</html>

未完成

注意用节点的方式获取元素

总归是完成了，对于js设置的时候，不太合理。

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        li {
            list-style: none;
            height: 20px;
            line-height: 20px;
        }

        a {
            text-decoration: none;
            color: black
        }

        .nav0,
        .nav1,
        .nav2 {
            position: relative;
            width: 80px;
            height: 82px;
            padding-left: 0px;
            float: left
        }

        .nav0>li,
        .nav1>li,
        .nav2>li {
            background-color: rgb(221, 216, 216);
            text-align: center;
        }

        .navv0,
        .navv1,
        .navv2 {
            position: absolute;
            top: 20px;
            left: 0px;
            border-top: 0px;
            padding-left: 0px;
            width: 80px;
            margin-top: -1px;
            display: none
        }

        .navv1 {
            width: 100px
        }

        .navv2 {
            width: 120px
        }

        .navv0 li,
        .navv1 li,
        .navv2 li {
            border-bottom: 1px solid orange;
            border-left: 1px solid orange;
            border-right: 1px solid rgb(240, 169, 28);
            padding-left: 5px
        }

        li:hover a {
            /* 注意改变的是链接里面的文字颜色 */
            color: orange
        }

        .nav0>li:hover,
        .nav1>li:hover,
        .nav2>li:hover {
            /* 冒号hover前面不要加空格 */
            background-color: rgb(138, 129, 129);
        }

        .navv0>li:hover,
        .navv1>li:hover,
        .navv2>li:hover {
            /* 冒号hover前面不要加空格 */
            background-color: rgb(236, 232, 203);
        }
    </style>
</head>

<body>

    <ul class="nav0">
        <li><a href="">微博</a></li>
        <ul class="navv0">
            <li><a href="">私信</a></li>
            <li><a href="">评论</a></li>
            <li><a href="">@我</a></li>
        </ul>
    </ul>
    <ul class="nav1">
        <li><a href="">博客</a></li>
        <ul class="navv1">
            <li><a href="">博客评论</a></li>
            <li><a href="">未读提醒</a></li>

        </ul>
    </ul>
    <ul class="nav2">
        <li><a href="">邮箱</a></li>
        <ul class="navv2">
            <li><a href="">免费邮箱</a></li>
            <li><a href="">VIP邮箱</a></li>
            <li><a href="">企业邮箱</a></li>
            <li><a href="">新浪客户邮箱</a></li>

        </ul>
    </ul>
    <script>
        //鼠标放在第一个大的nav中时，下拉栏就显示,离开第一个大nav时后，下拉菜单就不显示，这需要对第一个nav的盒子大小有要求，需要刚好把内容
        //获取元素
        var nav0 = document.querySelector('.nav0')
        var navv0 = document.querySelector('.navv0')
            //这三部分一起使用才行，首先鼠标放在nav里面的第一个导航栏里面，下来菜单需要出现，鼠标点在第一个下拉菜单时候，要保持出现，当鼠标离开整个nav的时候，下拉菜单隐藏
        nav0.children[0].onmouseover = function() {
            navv0.style.display = 'block'
                // this.style.backgroundColor = 'rgb(211,211,211)' //没必要这样写，直接写hover属性即可
                // this.style.color = 'red'

        }
        navv0.onmouseover = function() {
            navv0.style.display = 'block'
                // nav0.children[0].style.backgroundColor = 'rgb(211,211,211)'
        }
        nav0.onmouseout = function() {
                navv0.style.display = ''
                    // nav0.children[0].style.backgroundColor = 'rgb(221, 216, 216)'
            }
            // for (var i = 0; i < navv0.children; i++) {
            //     navv0.children[i].onmouseover = function() {
            //         console.log(11)
            //             // this.style.backgroundColor = 'orange'
            //     }
            // }

        var nav1 = document.querySelector('.nav1')
        var navv1 = document.querySelector('.navv1')
        nav1.children[0].onmouseover = function() {
            navv1.style.display = 'block'
                // this.style.backgroundColor = 'rgb(211,211,211)'

        }
        navv1.onmouseover = function() {
            navv1.style.display = 'block'
                // nav1.children[0].style.backgroundColor = 'rgb(211,211,211)'
        }
        nav1.onmouseout = function() {
            navv1.style.display = ''
                // nav1.children[0].style.backgroundColor = 'rgb(221, 216, 216)'
        }

        var nav2 = document.querySelector('.nav2')
        var navv2 = document.querySelector('.navv2')
        nav2.children[0].onmouseover = function() {
            navv2.style.display = 'block'
                // this.style.backgroundColor = 'rgb(211,211,211)'

        }
        navv2.onmouseover = function() {
            navv2.style.display = 'block'
                // nav1.children[0].style.backgroundColor = 'rgb(211,211,211)'
        }
        nav2.onmouseout = function() {
            navv2.style.display = ''
                // nav1.children[0].style.backgroundColor = 'rgb(221, 216, 216)'
        }
    </script>
</body>

</html>

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