JavaScript动态设置div样式的两种方法：style与className

<!DOCTYPE html>
<html>
<head>
<meta charset=" utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<head>
<title>动态设置div的样式</title>
<style type="text/css">
div{
 width:50px;
 height:50px;
 background:red;
 margin-top:10px;
}
.bg{
 background-color:blue;
}
</style>
<script type="text/javascript">
window.onload=function(){
 var firstDiv=document.getElementById("firstDiv");
 var secondDiv=document.getElementById("secondDiv");
 var first=document.getElementById("first");
 var second=document.getElementById("second");
 first.onclick=function(){
   firstDiv.style.backgroundColor="green";
 }
 second.onclick=function(){
   secondDiv.className="bg";
 }
}
</script>
</head>
<body>
<div id="firstDiv"></div>
<div id="secondDiv"></div>
<input type="button" value="使用style方式" id="first" />
<input type="button" value="使用className方式" id="second" />
</body>
</html> 

JS修改div样式：style对象与className用法详解

<script type="text/javascript">
 var oBox = document.getElementById('box');
 var oDiv = document.getElementById('div1');
 var aInput = document.getElementsByTagName('input');
 var aAttr = ['width', 'height', 'backgroundColor', 'display', 'display'];
 var aValue = ['200px', '200px', 'red', 'none', 'block'];
 for(var len=aInput.length,i=0;i<len;i++){
  aInput[i].index = i; //索引
  aInput[i].onclick = function(){
   //重置按钮,cssText清空DIV属性
   if(this.index == aInput.length - 1)oDiv.style.cssText = "";
   //设置DIV属性
   property(oDiv, aAttr[this.index], aValue[this.index]);
  };
 }
 //控制DIV属性
 function property(obj, attr, value){
  obj.style[attr] = value;
 }
</script>