JavaScript制作楼层导航效果流程详解

<div id="box" class="box">    <ul class="list">        <li class="content-part" data-n="栏目一">栏目一</li>        <li class="content-part" data-n="栏目二">栏目二</li>        <li class="content-part" data-n="栏目三">栏目三</li>        <li class="content-part" data-n="栏目四">栏目四</li>        <li class="content-part" data-n="栏目五">栏目五</li>    </ul></div><div class="left">    <ul id="left-list">        <li data-n="栏目一">栏目一</li>        <li data-n="栏目二">栏目二</li>        <li data-n="栏目三">栏目三</li>        <li data-n="栏目四">栏目四</li>        <li data-n="栏目五">栏目五</li>    </ul></div>

<style>    * {        margin: 0;        padding: 0;    }    body .box {        width: 1200px;    }    body .box {        margin: 0 auto;    }    ul {        list-style: none;    }    body .box ul li {        height: 800px;        background-color: silver;        margin-bottom: 20px;        font-size: 30px;        font-weight: bold;    }    body .left {        position: fixed;        left: 20px;        bottom: 100px;        width: 100px;        height: 250px;        top: 50%;        margin-top: -125px;        background-color: silver;    }    body .left ul li {        height: 50px;        line-height: 50px;        text-align: center;        cursor: pointer;    }    body .current {        color: #fff;        background-color: tomato;    }</style>

var oList = document.getElementById('left-list');// 点击事件委托oList.onclick = function (e) {    if (e.target.tagName.toLowerCase() == 'li') {        // 取data-n值        var n = e.target.getAttribute('data-n');        // []属性选择器        var contentPart = document.querySelector('.content-part[data-n=' + n + ']');        // 设置卷动        document.documentElement.scrollTop = contentPart.offsetTop;    }}

// 页面卷动时，左侧盒子栏目背景随之变化var contents = document.querySelectorAll('.content-part');var lis = document.querySelectorAll('#left-list li');var offsetTopArr = [];for (var i = 0; i < contents.length; i++) {    offsetTopArr.push(contents[i].offsetTop);}// 为了方便比较，追加无穷大offsetTopArr.push(Infinity);// 监听卷动var nowFloor = -1;window.onscroll = function (e) {    var nowScrollTop = document.documentElement.scrollTop;    // break的i值即为盒子数组下标    for (var i = 0; i < offsetTopArr.length; i++) {        if (nowScrollTop >= offsetTopArr[i] && nowScrollTop < offsetTopArr[i + 1]) {            break;        }    }    // 楼层不等，进行样式更改    if (nowFloor != i) {        nowFloor = i;        for (var j = 0; j < lis.length; j++) {            if (j == i) {                // 当前楼层添加样式                lis[j].className = 'current';            } else {                // 去掉其他楼层的样式                lis[j].className = '';            }        }    }}