<!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>
//注意掌握正则表达式
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, "");
}
}
function addClass(obj,cls){
if(!hasClass(obj,cls)){
obj.className +=" "+cls;
}
}
//定义getByClassName函数，让函数实现给对象增加class
//注意传入参数对象、函数内部for循环的使用以及if判断语句中的条件的书写
function getByClassName(obj,cls){
var elements=obj.getElementsByTagName("*");
var result=[];
for(var j=0;j<elements.length;j++){
if(elements[j].className==cls){
result.push(elements[j]);
}
}
return result;
}
//主要js
window.onload=function(){
window.onscroll=function(){
var top=document.documentElement?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;
}
}
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");
}else{
addClass(menu,"current");
}
}
}
}
}
//请补充此处代码，给正确的menu下的a元素class赋值current
</script>
</head>
</html>教程里的有问题，不如改成var top = document.body.scrollTop ? document.body.scrollTop : document.documentElement.scrollTop;
前后换一下位置就没问题了
改为var top=document.documentElement.scrollTop||document.body.scrollTop
给下html结构看一下