How jQuery calculates iframe window width and height

<iframe id="aaax" src="" scrolling="no" frameborder="0" style="
display
:none"></iframe> 
<script language="
javascript
" type="text/javascript"> 
$(function () { 
var $main = $("#main").height(); 
var $searchPanel = $("#searchPanel").height(); 
var $listArea = $("#listArea").height(); 
$("#aaax").height($(window).height() - $main - $searchPanel - $listArea + 180); 
var $aaax = $("#aaax").height(); 
if ($aaax < 282) { $("#aaax").height(300); } 
else { $("#aaax").height($(window).height() - $main - $searchPanel - $listArea + 180); } 
var $chartArea = $("#chartArea").width(); 
var $chartAreaLeft = $(".chartAreaLeft").width(); 
$("#aaax").width($chartArea - $chartAreaLeft - 10); 
var $aaaxWidth = $("#aaax").width(); 
if ($aaaxWidth < 597) { $("#aaax").width(500); } 
else { $("#aaax").width($chartArea - $chartAreaLeft - 10); } 
}); 
</script>