标签：padding func hid star ide 分享 菜单显示 his pos
简单的分析一下，要实现N级菜单，首先从布局入手，即判断是否有下级菜单
图：1
注意： 下面凡是担忧 xxx===yyy ? xxx : xxx都是利用三元表达式，来表达思路。
ＨＴＭＬ结构如下：
图：2
ＨＴＭＬ结构如下：
效果图如下：
代码如下：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style type="text/css"> * { margin: 0; padding: 0; } #box { margin: 200px 0 0 50px; text-align: center; color: #ccc; } ul { list-style: none; float: left; } li { width: 150px; height: 40px; line-height: 40px; background-color: #124520; border: 1px solid #eee; position: relative; } li span { position: absolute; top: 0; right: 10px; } li:hover { background-color: #666; transition: background-color .5s; } ul { display: none; } ul.first { display: block; } .relative { position:relative; top: 0; left: 0; } .absolute { position: absolute; left: 0; top: 0; } .show { display: block; } .hide { display: none; } </style> </head> <body> <div id="box"> <ul class="first"> <li>一级菜单 <span>></span> </li> <li>一级菜单 <span>></span> <ul> <li>二级菜单 <span>></span> <ul> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> </ul> </li> <li>二级菜单 <span>></span> <ul> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> </ul> </li> <li>二级菜单 <span>></span> </li> <li>二级菜单 <span>></span> <ul> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> </ul> </li> </ul> </li> <li>一级菜单 <span>></span> <ul> <li>二级菜单 <span>></span> </li> <li>二级菜单 <span>></span> <ul> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> </ul> </li> <li>二级菜单 <span>></span> <ul> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> </ul> </li> <li>二级菜单 <span>></span> <ul> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> <li>三级菜单 <span>></span> </li> </ul> </li> </ul> </li> <li>一级菜单 <span>></span> </li> </ul> </div> </body> <script type="text/javascript"> let uls = document.querySelectorAll("ul"); //获取所有的ul let lis = document.querySelectorAll("li"); //获取所有的li let liWidth = document.querySelector("#box ul").offsetWidth-2 //li的宽度 -2是为了好看 /* 布局start */ /* * * 通过下面布局中代码实现每个 li.children.length 要么为0 要么为2 * 0 无下级菜单 * 2 有下级菜单 * */ for (let i = uls.length - 1; i >= 0; i--) { if(uls[i].parentNode.nodeName === "LI") { uls[i].parentNode.classList.add("relative"); //相对定位 uls[i].classList.add("absolute"); // 绝对定位 uls[i].style.left = liWidth + "px"; } } for (var i = 0; i < lis.length; i++) { if( lis[i].children.length === 1) { //没有下一级菜单直接删除 lis[i].children[0].outerHTML = ""; }; } /* 布局end */ for (let i = 0; i < lis.length; i++) { // 控制每一个li lis[i].onmouseover = function() { if( lis[i].children.length === 2) { this.children[1].classList.remove("hide"); this.children[1].classList.add("show"); } } lis[i].onmouseout = function() { if( lis[i].children.length === 2) { this.children[1].classList.remove("show"); this.children[1].classList.add("hide"); } } } </script> </html>
上面代码实现了，只要用ul,li结构嵌套在li标签里面即可
标签：padding func hid star ide 分享 菜单显示 his pos
原文地址：http://www.cnblogs.com/cq-lcq/p/6884123.html
