效果：在可视区域内随鼠标滚动，但始终在同一个位置
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
#div{
height:500px;
width:100px;
background:red;
position:absolute;
right:50px;
top:100px;
}
</style>
</head>
<body style="height:5000px;">
<div id="div"></div>
<script>
window.onload=window.onscroll=function(){
var oDiv=document.getElementById("div");
var scrolltop=document.documentElement.scrollTop||document.body.scrollTop;
//向下距离加上可视区高减去div实际高度的一半
var t=scrolltop+(document.documentElement.clientHeight-oDiv.offsetHeight)/2;
moveStart(parseInt(t));
}
var timer=null;
function moveStart(iTarget)
{
var oDiv=document.getElementById('div');
clearInterval(timer);
timer=setInterval(function(){
var iSpeed=(iTarget-oDiv.offsetTop)/4;
iSpeed=iSpeed>0?Math.ceil(iSpeed):Math.floor(iSpeed);
if(oDiv.offsetTop==iTarget)
{
clearInterval(timer);
}
else
{
oDiv.style.top=oDiv.offsetTop+iSpeed+'px';
}
},30);
}
</script>
</body>
</html>