<!DOCTYPE html> <html> <head> <meta charset="utf-8"/> <title>地狗购物网——网页定位导航效果</title> <style> * { margin: 0; padding: 0; } body { font-size: 12px; line-height: 1.7; } li { list-style: none; } #content { width: 800px; margin: 0 auto; padding: 20px; } #content h1 { color: #0088bb; } #content .item { padding: 20px; margin-bottom: 20px; border: 1px dotted #0088bb; } #content .item h2 { font-size: 16px; font-weight: bold; border-bottom: 2px solid #0088bb; margin-bottom: 10px; } #content .item li { display: inline; margin-right: 10px; } #content .item li a img { width: 230px; height: 230px; border: none; } #menu { position: fixed; top: 100px; left: 50%; margin-left: 400px; width: 80px; } #menu ul li a { display: block; margin: 5px 0; font-size: 14px; font-weight: bold; color: #333; width: 80px; height: 50px; line-height: 50px; text-decoration: none; text-align: center; } #menu ul li a:hover, #menu ul li a.current { color: #fff; background: #0088bb; } /*ie6 hack*/ * html, * html body { background-image: url(about:blank); background-attachment: fixed; } * html #menu { /*position: fixed;*/ position: absolute; top: expression(((e=document.documentElement.scrollTop)?e:document.body.scrollTop)+100+'px'); } </style> <script> //定义getByClassName函数，让函数实现根据class name获取对象并返回 function getByClassName(obj,cls){ var elements=obj.getElementsByTagName("*"); var result=[]; for(var i=0;i<elements.length;i++){ if(elements[i].className==cls){ result.push(elements[i]); } } return result; } // 用removeAttribute,setAttribute属性之后，这三个函数都不需要啦 function hasClass( obj, cls ){ return obj.className.match(new RegExp("(\\s|^)" + cls + "(\\s|$)")); } function removeClass( obj, cls ){ if( hasClass( obj, cls )){ //remove var reg = new RegExp("(\\s|^)" + cls + "(\\s|$)"); obj.className = obj.className.replace(reg, ""); } } //定义addClaass函数，让函数实现给对象增加class function addClass(obj,cls){ if(!hasClass( obj, cls )){ obj.className+=""+cls; } } window.onload = function(){ window.onscroll = function(){ var top = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop; var menus = document.getElementById("menu").getElementsByTagName("a"); var items = getByClassName(document.getElementById("content"), "item"); var currentId = ""; for ( var i=0; i< items.length; i++ ){ var _item = items[i]; var _itemTop = _item.offsetTop; if( top > _itemTop - 200 ){ currentId = _item.id; } else { break; } } //请补充此处代码，给正确的menu下的a元素class赋值current if(currentId){ for(var i=0;i<menus.length;i++){ var _menu=menus[i]; var _href=_menu.href.split("#"); if(_href[_href.length-1]!=currentId){ // removeClass(_menu,"current"); _menu.removeAttribute("class","current"); } else{ // addClass(_menu,"current"); _menu.setAttribute("class","current"); } } } } } </script> </head> <body> <div id="menu"> <ul> <!--运用锚点，实现导航定位。--> <li><a href="#item1" class="current">1F 男装</a></li> <li><a href="#item2">2F 女装</a></li> <li><a href="#item3">3F 美妆</a></li> <li><a href="#item4">4F 数码</a></li> <li><a href="#item5">5F 母婴</a></li> </ul> </div> <div id="content"> <h1>地狗购物网</h1> <div id="item1" class="item"> <h2>1F 男装</h2> <ul> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/53660fce0001111903990422.jpg" alt=""/></a></li> </ul> </div> <div id="item2" class="item"> <h2>2F 女装</h2> <ul> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/5366104c0001e5c403990422.jpg" alt=""/></a></li> </ul> </div> <div id="item3" class="item"> <h2>3F 美妆</h2> <ul> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610820001cf5b03990422.jpg" alt=""/></a></li> </ul> </div> <div id="item4" class="item"> <h2>4F 数码</h2> <ul> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610ac00012df703990422.jpg" alt=""/></a></li> </ul> </div> <div id="item5" class="item"> <h2>5F 母婴</h2> <ul> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> <li><a href="#"><img src="http://img.mukewang.com/536610cd0001f34603990422.jpg" alt=""/></a></li> </ul> </div> </div> </body> </html>
图为改进后的代码
1.js中ie8及以下浏览器不支持getElementsByClassName,
(1)JS原生代码里addClass添加类,要带空格
举例子 ：
<div class="item1 item2"> </div>
上面是一个div，这个div的样式已经有两个，所以你再添加class的时候就需要加空格后再加入新的样式。
最后得到： <div class="item1 item2 new"> </div>
(2)移除类：不能直接让 obj.className="";因为一个对象可能有很多类。要用如下空格替换要移除的正则表达式。
obj.className = obj.className.replace(reg, "");
2.var result = [ ];定义一个空数组。
3.window.onscroll = function(){}; 当窗口滚动时，那么执行以下函数。如果没有这一行，那么，窗口滚动没有触发任何的函数，相当于没用。window.scroll就是触发窗口滚动事件。
4._menu的href属性也可以直接用getAttribute('href') _menu.getAttribute('href')
js可以用 setAttribute('class','className')