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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
body {
height: 2000px;
}
#up {
position: fixed;
bottom: 0;
right: 0;
width: 100px;
height: 100px;
background: #c1c1c1;
}
</style>
</head>
<body>
<div id="up"></div>
<script>
window.onload = function (){
var oDiv = document.getElementById("up");
var timer = null;
var bySys = true;
//如何检测用户拖动了滚动条
window.onscroll = function (){
if (!bySys) {
clearInterval(timer);
}
bySys = false;
}
oDiv.onclick = function (){
timer = setInterval(function() {
var scrollTop = document.documentElement.scrollTop ||
document.body.scrollTop;
var iSpeed = Math.floor(-scrollTop/8);
if (scrollTop === 0) {
clearInterval(timer);
}
bySys = true;
document.body.scrollTop = scrollTop + iSpeed;
document.documentElement.scrollTop = scrollTop + iSpeed;
}, 30);
}
}
</script>
</body>
</html>
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原文地址：http://www.cnblogs.com/zhongshanblog/p/4649524.html
