<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
*{
margin:0;
padding:0;
}
.bar{
position: fixed;
top:0;
left:0;
width:0%;
height:10px;
background: #aa2;
}
.container{
width:100%;
height:2000px;
background: #fff;
}
</style>
</head>
<body>
<div class="bar"></div>
<div class="container"></div>
</body>
<script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
var windowHeight=$(window).height();
var documentHeight=$(document).height();
//console.log(windowHeight);
//console.log(documentHeight);
$(window).scroll(function(){
var scrollHeight=$(document).scrollTop();
//console.log(scrollHeight);
var n=documentHeight-windowHeight;
var bili=scrollHeight/n;
console.log(bili*100+"%")
$(".bar").width(bili*100+"%");
})
})
</script>
</html>
