js习题（筋斗云导航栏）

<!DOCTYPE html>
<html>

<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        * {
     
     
            margin: 0;
            padding: 0
        }

        ul {
     
     
            list-style: none;
        }

        body {
     
     
            background-color: black;
        }

        .c-nav {
     
     
            width: 900px;
            height: 42px;
            background: #fff url(images/rss.png) no-repeat right center;
            margin: 100px auto;
            border-radius: 5px;
            position: relative;
        }

        .c-nav ul {
     
     
            position: absolute;
        }

        .c-nav li {
     
     
            float: left;
            width: 83px;
            text-align: center;
            line-height: 42px;
        }

        .c-nav li a {
     
     
            color: #333;
            text-decoration: none;
            display: inline-block;
            height: 42px;
        }

        .c-nav li a:hover {
     
     
            color: white;
        }

        .c-nav li.current a {
     
     
            color: #0dff1d;
        }

        .cloud {
     
     
            position: absolute;
            left: 0;
            top: 0;
            width: 83px;
            height: 42px;
            background: url(images/cloud.gif) no-repeat;
        }
    </style>
    <!-- <script src="animate.js"></script> -->
    <script>
        window.addEventListener('load', function () {
     
     
            // 1. 获取元素
            var cloud = document.querySelector('.cloud');
            var c_nav = document.querySelector('.c-nav');
            var lis = c_nav.querySelectorAll('li');
            // 2. 给所有的小li绑定事件 
            // 这个current 做为筋斗云的起始位置
            var current = 0
            for (var i = 0; i < lis.length; i++) {
     
     
                lis[i].addEventListener('mouseenter', function () {
     
     
                    console.log(this.offsetLeft)
                    animate(cloud, this.offsetLeft)
                })
                lis[i].addEventListener('mouseleave', function () {
     
     
                    animate(cloud, current)
                })
                lis[i].addEventListener('click', function () {
     
     
                    current = this.offsetLeft
                })
            }

            function animate(obj, target, callBack) {
     
     
                clearInterval(obj.timer)
                obj.timer = setInterval(function () {
     
     
                    var step = (target - obj.offsetLeft) / 10
                    step = (step > 0 ? Math.ceil(step) : Math.floor(step))
                    if (obj.offsetLeft == target) {
     
     
                        clearInterval(obj.timer)
                        callBack && callBack()
                        return
                    }
                    obj.style.left = obj.offsetLeft + step + 'px'
                }, 15)
            }
        })
    </script>
</head>

<body>
    <div id="c_nav" class="c-nav">
        <span class="cloud"></span>
        <ul>
            <li class="current"><a href="#">首页新闻</a></li>
            <li><a href="#">师资力量</a></li>
            <li><a href="#">活动策划</a></li>
            <li><a href="#">企业文化</a></li>
            <li><a href="#">招聘信息</a></li>
            <li><a href="#">公司简介</a></li>
            <li><a href="#">我是佩奇</a></li>
            <li><a href="#">啥是佩奇</a></li>
        </ul>
    </div>
</body>

</html>
js习题（筋斗云导航栏）

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