JS 实现导航栏悬停效果

JS-实现导航栏悬停

先布个局：

 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<head> 
<script type="text/javascript" src="test.js"></script> 
<link rel="stylesheet" type="text/css" href="test.css"></link> 
<title>Test</title> 
</head> 
<body> 
<div class="main"> 
<div class="content">1</div> 
<div id="nav" class="navigation"> 
<div class="tab">tab1</div> 
<div class="tab">tab2</div> 
<div class="tab">tab3</div> 
<div class="tab">tab4</div> 
</div> 
<div class="content">2</div> 
<div class="content">3</div> 
<div class="content">4</div> 
<div class="content">5</div> 
<div class="content">6</div> 
<div class="content">7</div> 
</div> 
</body> 
</html> 

添加简单的样式：

复制代码代码如下:

 
div.main{ 
width: 800px; 
background: #CCC; 
margin: 10px auto 0; 
position: relative; 
} 

div.content{ 
width: 800px; 
height: 400px; 
background: yellow; 
margin: 10px auto 0; 
} 

div.navigation{ 
width: 800px; 
height: 40px; 
background: red; 
margin: 4px auto 0; 
top: 400px; 
left: 0px; 
position: absolute; 
} 

div.tab{ 
width: 195px; 
height: 40px; 
background: blue; 
float: left; 
margin-left: 5px; 
} 

JS:

复制代码代码如下:

 
//记录导航条原来在页面上的位置 
var naviga_offsetTop = 0; 

//IE7不识别getElementsByClassName，为了兼容自定义一个 
function my_getElementsByClassName(class_name) { 
var el = []; 
//获取所有元素 
_el = document.getElementsByTagName('*'); 
//通过className刷选 
for (var i=0; i<_el.length; i++ ) { 
if (_el[i].className == class_name ) { 
el[el.length] = _el[i]; 
} 
} 
return el; 
} 

//导航条，悬停在顶部 
function naviga_stay_top(){ 
var a_navigation_bar = []; 
if(document.getElementsByClassName){//Chrome, FF 
a_navigation_bar = document.getElementsByClassName("navigation"); 
} else {//IE 
a_navigation_bar = my_getElementsByClassName("navigation"); 
} 
var scrollTop = document.body.scrollTop || document.documentElement.scrollTop; 

if( scrollTop > naviga_offsetTop){ 
a_navigation_bar[0].style.top = scrollTop + "px"; 
} else { 
a_navigation_bar[0].style.top = naviga_offsetTop + "px"; 
} 
} 


//给导航条上四个tab，加上点击事件。 
window.onload=function(){ 
var a_tabs = []; 
if( document.getElementsByClassName ){//Chrome, FF 
a_tabs = document.getElementsByClassName("tab"); 
}else{ //IE 
a_tabs = my_getElementsByClassName("tab"); 
} 

var a_contents = []; 
if( document.getElementsByClassName ){//Chrome, FF 
a_contents = document.getElementsByClassName("content"); 
}else{//IE 
a_contents = my_getElementsByClassName("content"); 
} 

a_tabs[0].onclick=function(){ 
window.scrollTo(0, a_contents[2].offsetTop); 
} 
a_tabs[1].onclick=function(){ 
window.scrollTo(0, a_contents[3].offsetTop); 
} 
a_tabs[2].onclick=function(){ 
window.scrollTo(0, a_contents[4].offsetTop); 
} 
a_tabs[3].onclick=function(){ 
window.scrollTo(0, a_contents[5].offsetTop); 
} 

//获取页面上，导航条到顶部的位置 
var a_navigation_bar = []; 
if(document.getElementsByClassName){//Chrome, FF 
a_navigation_bar = document.getElementsByClassName("navigation"); 
} else {//IE 
a_navigation_bar = my_getElementsByClassName("navigation"); 
} 
naviga_offsetTop = a_navigation_bar[0].offsetTop; 

//给滚动条以及鼠标加上滚动事件 
// window.onscroll= naviga_stay_top; 
// document.onmousewheel= naviga_stay_top; 
if( window.attachEvent) //IE 
{ 
window.attachEvent("onmousewheel", naviga_stay_top); 
window.attachEvent("onscroll", naviga_stay_top); 

document.attachEvent("onmousewheel", naviga_stay_top); 
document.attachEvent("onscroll", naviga_stay_top); 
} else {//Chrome ,FF 
window.addEventListener("mousewheel", naviga_stay_top,false); 
window.addEventListener("scroll", naviga_stay_top,false); 

document.addEventListener("mousewheel", naviga_stay_top,false); 
document.addEventListener("scroll", naviga_stay_top,false); 
} 

} 

不知道什么原因，在IE上，滚动滚动条或者鼠标滚轮的时候，导航栏会抖动;而在Chrome和FF上有没有任何问题。还望高人指点。

JS 实现导航栏悬停效果

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