js实现带按钮的上下滚动效果

本文实例讲述了js实现带按钮的上下滚动效果。分享给大家供大家参考。具体实现方法如下：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>js带按钮上下滚动效果</title>
<style type="text/css">
ul{
 margin:0;
 padding:0;
 list-style:none;
 height:100000px;
}
li{
 margin:0;
 padding:0;
 width:100px;
 height:100px;
 display:block;
 float:top;
 margin-bottom:5px;
 background:#009900;
}
#img_bag{
 width:110px;
 height:600px;
 background:#F2F2F2;
 margin:0 auto;
 text-align:center;
}
#img_bag #img{
 width:100px;
 height:525px;
 background:#969696;
 overflow:hidden;
 margin:auto;
}
</style>
</head>
<body>
<div id="img_bag">
 <a href="javascript:void(0)" onmousedown="moveTop()">
 <img src="upp.jpg" border="0" /></a>
 <div id="img">
 <ul>
  <li>1</li>
  <li>2</li>
  <li>3</li>
  <li>4</li>
  <li>5</li>
  <li>6</li>
  <li>7</li>
  <li>8</li>
  <li>9</li>
  <li>10</li>
  <li>11</li>
  <li>12</li>
 </ul>
 </div>
 <a href="javascript:void(0)" onmousedown="moveBottom()">
 <img src="down.jpg" border="0" /></a>
</div>
<script type="text/javascript">
function $(obj){
 //获取指定对象
 return document.getElementById(obj);
}
var maxHeight=$("img").getElementsByTagName("ul")[0].getElementsByTagName("li").length*105;
//滚动图片的最大高度
var targety = 211;
//一次滚动距离
var dx;
var a=null;
function moveTop(){
 var le=parseInt($("img").scrollTop);
 if(le>211){
 targety=parseInt($("img").scrollTop)-211;
 }else{
 targety=parseInt($("img").scrollTop)-le-1;
 }
 scTop();
}
function scTop(){
 dx=parseInt($("img").scrollTop)-targety;
 $("img").scrollTop-=dx*.3;
 clearScroll=setTimeout(scTop,50);
 if(dx*.3<1){
 clearTimeout(clearScroll);
 }
}
function moveBottom(){
 var le=parseInt($("img").scrollTop)+211;
 var maxL=maxHeight-600;
 if(le<maxL){
 targety=parseInt($("img").scrollTop)+211;
 }else{
 targety=maxL
 }
 scBottom();
}
function scBottom(){
 dx=targety-parseInt($("img").scrollTop);
 $("img").scrollTop+=dx*.3;
 a=setTimeout(scBottom,50);
 if(dx*.3<1){
 clearTimeout(a)
 }
}
</script>
</body>
</html>

运行效果如下所示：

希望本文所述对大家的javascript程序设计有所帮助。