?? About the "window=this" in the source code of the jquery

?? About the "window=this" in the source code of the jquery


I write a code like below to use "window=this", but it is wrong!!
<html>
<head><title>this example</title>
<script language="Javascript" type="text/javascript">
window=this;
function dosomething(){
this.style.color="red";
}
window.onload=function(){ document.getElementById
("h").onclick=dosomething; }
</script>
</head>
<body>
<hl id="h">this example</h1>
</body>
</html>
the right code is cancel the "window=this", why? why use the
"window=this" in jquery source code???