楼梯跳跃代码web

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        *{margin: 0;padding: 0;}
        html,body{width: 100%;height: 100%;}
        ul,ol{list-style: none;}
        ul{width: 100%;height: 100%;}
        ul li{width: 100%;height: 100%;}
        ol{position: fixed;top: 100px;left: 100px;}
        ol li{
            width: 50px;
            height: 50px;
            border: 1px solid #000;
            margin-top: -1px;
            text-align: center;
            font: 400 22px/50px "simsun";
            cursor: pointer;
        }
    </style>
</head>
<body>
    <ul id="ul">
        <li>男装区</li>
        <li>女装区</li>
        <li>童装区</li>
        <li>孕装区</li>
        <li>老年装区</li>
    </ul>
    <ol id="ol">
        <li>男装</li>
        <li>女装</li>
        <li>童装</li>
        <li>孕装</li>
        <li>老年</li>
    </ol>
</body>
</html>
<script>
    //需求：给所有盒子添加颜色，点击ol的li，页面跳转到ul中相应的li
    //步骤：
    //1、利用数组给所有盒子添加颜色
    //2、缓动框架移动最顶端
    //3、移动到指定位置（给ol中的li绑定索引值，获取对应的ul中的li距离顶端的距离，赋值给target，好让页面跳转
    //4、屏幕滑动，记录屏幕的位置

    var ul = document.getElementById("ul");
    var ol = document.getElementById("ol");
    var ulLis = ul.children;
    var olLis = ol.children;
    var arr = ["pink","yellow","green","purple","orange"];

    var timer = null,target = 0,leader = 0;

    window.onscroll = function () {
        //屏幕滑动，给屏幕目前所在的位置赋值。
        leader = scroll().top;
    }

    for(var i=0;i<olLis.length;i++){
        //为每一个盒子上色，ul和ol中的li对应颜色
        ulLis[i].style.backgroundColor = arr[i];
        olLis[i].style.backgroundColor = arr[i];

        olLis[i].index = i;
        olLis[i].onclick = function(){
            //给目标位置赋值(小盒子对应的大盒子距离顶部的距离)
            target = ulLis[this.index].offsetTop;
            clearInterval(timer);
            timer = setInterval(function(){
                var step = (target-leader)/10;
                step = step>0?Math.ceil(step):Math.floor(step);
                leader = leader+step;
                window.scrollTo(0,leader);
                if(target == leader){
                    clearInterval(timer);
                }
            },30)
        }
    }
</script>