JS与CSS实现DIV层展开与收缩效果详解

<html>
<head>
<title>CSS+JS实现一个DIV层的展开/折叠效果</title>
<style>
* { margin:0; padding:0;}
body { text-align:center; font:75% Verdana, Arial, Helvetica, sans-serif;}
h1 { font:125% Arial, Helvetica, sans-serif; text-align:left; font-weight:bolder; background:#555; padding:3px; display:block; color:#99CC00}
.class1 { width:40%; background:#CCCCCC; position:relative; margin:0 auto; padding:5px;}
span { position:absolute; right:10px; top:8px; cursor:pointer; color:yellow;}
p { text-align:left; line-height:20px; background:#555; padding:3px; margin-top:5px; color:#99CC00}
#class1content { height:256px;overflow:hidden}
</style>
<script>
function $(element){
return element = document.getElementById(element);
}
function $D(){
var d=$('class1content');
var h=d.offsetHeight;
var maxh=300;
function dmove(){
h+=50; //层展开速度
if(h>=maxh){
d.style.height='300px';
clearInterval(iIntervalId);
}else{
d.style.display='block';
d.style.height=h+'px';
}
}
iIntervalId=setInterval(dmove,2);
}
function $D2(){
var d=$('class1content');
var h=d.offsetHeight;
var maxh=300;
function dmove(){
h-=50;//层收缩速度
if(h<=0){
d.style.display='none';
clearInterval(iIntervalId);
}else{
d.style.height=h+'px';
}
}
iIntervalId=setInterval(dmove,2);
}
function $use(){
var d=$('class1content');
var sb=$('stateBut');
if(d.style.display=='none'){
$D();
sb.innerHTML='收缩';
}else{
$D2();
sb.innerHTML='展开';
}
}
</script>
</head>
<body>
<div class="class1">
<span id="stateBut" onclick="$use()">收缩</span>
<p id="class1content">本站。
</p>
</div>
</body>

<html>
<head>
  <meta http-equiv="Content-Type" content="text/html;charset=gb2312">
  <title>Title</title>
</head>
<body>
<!-- js 控制 展开 隐藏div -->
<img src="image/down.png" onclick="test(this)">  <!--this 指 img 对象 -->

<div id="div2" style="border:1px solid #ccc; width:300px; height:200px; display: block;">
  （1）每个HTML标记都有事件句柄属性。onClick是HTML标记属性，不分大小写。
  （2）HTML标记对应的元素对象也具有事件句柄属性，这个属性必须全小写，因JS区分大小写
</div>
</body>
</html>
<script type="text/javascript">
function test(obj){

  var div1=document.getElementById("div2");
  if(div1.style.display=="block"){
    div1.style.display="none";
    obj.src="image/up.png";
  }else{
    div1.style.display="block";
    obj.src="image/down.png";
  }
}
</script>