js控制层

<!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=gb2312" />
<title>MessageBox演示</title>
<script language="javascript">
var Xdown=Ydown=0 ;
var Xup=Yup=0 ;
var DivW = DivH = 0;
//根据两个坐标生成
function MouseDown(){
Xdown = event.clientX;
Ydown = event.clientY;
}
function MouseUp(){
Xup = event.clientX;
Yup = event.clientY;
var DivX = (Xup<Xdown) ? Xup:Xdown ;
var DivY = (Yup<Ydown) ? Yup:Ydown ; 
if (Xup>Xdown)
{
DivW = Xup-Xdown;
}
else
{
DivW = Xdown - Xup;
}
if (Yup>Ydown)
{
DivH = Yup-Ydown;
}
else
{
DivH = Ydown - Yup;
}