js拖拽进度条

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm4.aspx.cs" Inherits="WebApplication1.WebForm4" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<style type="text/css">
#box {
position: relative;
width: 200px;
height: 50px;
border: 1px solid #eee;
margin: 50px auto 0;
}

#bg {
height: 10px;
margin-top: 19px;
border: 1px solid #ddd;
border-radius: 5px;
overflow: hidden;
}

#bgcolor {
background: #5889B2;
width: 0;
height: 10px;
border-radius: 5px;
}

#bt {
width: 34px;
height: 34px;
background: url(http://bbs.blueidea.com/data/attachment/album/201505/22/192934pwywwrt8cbrfwzfh.png) no-repeat center center;
border-radius: 17px;
overflow: hidden;
position: absolute;
left: 0px;
margin-left: -17px;
top: 8px;
cursor: pointer;
}

#text {
width: 200px;
margin: 0 auto;
font-size: 16px;
line-height: 2em;
}
</style>
<script type="text/javascript" src="http://www.w3school.com.cn/jquery/jquery-1.11.1.min.js"></script>
</head>
<body>
<div>
<div id="box">
<div id="bg">
<div id="bgcolor"></div>
</div>
<div id="bt"></div>
</div>
<div id="text"></div>
<script type="text/javascript">
(function ($) {
var $box = $('#box');
var $bg = $('#bg');
var $bgcolor = $('#bgcolor');
var $btn = $('#bt');
var $text = $('#text');
var statu = false;
var ox = 0;
var lx = 0;
var left = 0;
var bgleft = 0;
$btn.mousedown(function (e) {
lx = $btn.offset().left;
ox = e.pageX - left;
statu = true;
});
$(document).mouseup(function () {
statu = false;
});
$box.mousemove(function (e) {
if (statu) {
left = e.pageX - ox;
if (left < 0) {
left = 0;
}
if (left > 200) {
left = 200;
}
$btn.css('left', left);
$bgcolor.width(left);
$text.html('位置:' + parseInt(left / 2) + '%');
}
});
$bg.click(function (e) {
if (!statu) {
bgleft = $bg.offset().left;
left = e.pageX - bgleft;
if (left < 0) {
left = 0;
}
if (left > 200) {
left = 200;
}
$btn.css('left', left);
$bgcolor.stop().animate({ width: left }, 200);
$text.html('位置:' + parseInt(left / 2) + '%');
}
});
})(jQuery);
</script>
</div>
</body>
</html>