JS implementation method to expand web window from the middle to the top and bottom

<html>
<head>
<title>js displays the web window of the expanded middle</title>
<style>

</style>
</head>
<body>
<div class="intro"></div><div class="intro"></div>
<script language="JavaScript1.2">
var speed=20
var temp=new Array()
var temp2=new Array()
if (){
for (i=1;i<=2;i++){
temp[i]=eval(""+i+".clip")
temp2[i]=eval(""+i)
temp[i].width=
temp[i].height=/2
temp2[i].top=(i-1)*temp[i].height
}
}
else if (){
var clipbottom=/2,cliptop=0
for (i=1;i<=2;i++){
temp[i]=eval(""+i+".style")
temp[i].width=
temp[i].height=/2
temp[i].top=(i-1)*parseInt(temp[i].height)
}
}
function openit(){
(0,0)
if (){
temp[1].bottom-=speed
temp[2].top+=speed
if (temp[1].bottom<=0)
clearInterval(stopit)
}
else if (){
clipbottom-=speed
temp[1].clip="rect(0 auto+"+clipbottom+" 0)"
cliptop+=speed
temp[2].clip="rect("+cliptop+" auto auto)"
if (clipbottom<=0)
clearInterval(stopit)
}
}
function gogo(){
stopit=setInterval("openit()",100)
}
gogo()
</script>
</body>
</html>