Centre div in window no matter what – Version 2

In a previous post I showed you how to center a div on screen regardless of if it was inside an iframe or not. This is the second version, which should work regardless of if the div is in the top level window, an iframe, or a regular frame.

/******************************************************************
	Name: center
	Description: Center a div on page, no matter what!
	Author: AK (www.zeroedandnoughted.com)
	Date: 22nd April 2009
	Version: 0.2
	Dependencies: jQuery
	Notes:
	******************************************************************/
	(function($) {
	    $.fn.center = function() {
	        return this.each(function() {
				var $this = $(this);
				var frameXOffset = 0, frameYOffset = 0, windowHeight = 0, windowWidth = 0;
				//Are we in a frame?
				if (top.document != window.document) {
					var frm = $('iframe',top.document.body);
					if (frm.length == 0) {
						//regular frame
						frm =  $('frame',top.document.body);
					}
					var i=frm.length;
					while (i--) {
						if (frm[i].contentDocument) {
							doc = frm[i].contentDocument;
						} else {
							doc = frm[i].contentWindow.document;
						}
						if (doc === document) {
							//located our frame!
							frameXOffset = $(frm[i]).offset().left;
							frameYOffset = $(frm[i]).offset().top;
							break;
						}
					};
					if (jQuery.browser.msie) {
						windowWidth = top.window.document.documentElement.clientWidth;
						windowHeight = top.window.document.documentElement.clientHeight;
					} else {
						windowWidth = top.window.innerWidth;
						windowHeight = top.window.innerHeight;
					}
				} else {
					//we are not in a frame
					if (jQuery.browser.msie) {
						windowWidth = window.document.documentElement.clientWidth;
						windowHeight = window.document.documentElement.clientHeight;
					} else {
						windowWidth = window.innerWidth;
						windowHeight = window.innerHeight;
					}
				}
				var elHeight = $this.height();
				var newTop = ((windowHeight/2) - (elHeight/2)) - frameYOffset + $(parent.document.documentElement).scrollTop();
				if ((newTop + elHeight) > $(document).height()) {
					newTop = $(document).height() - elHeight;
				}
				$this.css ({
					left: ((windowWidth/2) - ($this.width()/2)) - frameXOffset + $(parent.document.documentElement).scrollLeft(),
					top: newTop
				});
			});
		};
	})(jQuery);