<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
#div1{
width: 30px;
height: 500px;
background: black;
position: absolute;
left: 10px;
top: 10px;
}
#div2{
width: 30px;
height: 30px;
background: red;
position: absolute;
left: 0;
top: 0;
}
#div3{
width: 500px;
height: 0;
background: green;
position: absolute;
left: 50px;
top: 10px;
}
</style>
<script>
window.onload=function(){
var oDiv1=document.getElementById("div1");
var oDiv2=document.getElementById("div2");
var oDiv3=document.getElementById("div3");
var iMaxTop=oDiv1.offsetHeight-oDiv2.offsetHeight;
oDiv2.onmousedown=function(ev){
var ev=ev||event;
var disY=ev.clientY-this.offsetTop;
document.onmousemove=function(ev){
var ev=ev||event;
var T=ev.clientY-disY;
if(T<0){
T=0;
}else if(T>iMaxTop){
T=iMaxTop;
}
oDiv2.style.top=T+"px";
var iScale=T/iMaxTop;
// document.title=iScale;
oDiv3.style.height=500*iScale+"px";
}
document.onmouseup=function(){
document.onmousemove=document.onmouseup=null;
}
return false;
}
}
</script>
</head>
<body>
<div id="div1">
<div id="div2"></div>
</div>
<div id="div3"></div>
</body>
</html>
