jQuery $("body").height() returns undefined

Question

I have a call like this:

$("#ContextMenuModal").height($("body").height());

However $("body").height() returns undefined when I view it in Firebug.

What would cause jQuery to return undefined for the body height?

I am using jQuery 1.4.1.

Edit:

This is inside an iFrame

Answer 1

Simply use

$(document).height() // - $('body').offset().top

and / or

$(window).height()

instead $('body').height()

To expand a bit,

$(window).height();   // returns height of browser viewport
$(document).height(); // returns height of HTML document

As bažmegakapa points out, there is a slight difference, albeit a few pixels. The true height of the body can be calculated by subtracting the body offset from the document height (like I mentioned above):

$(document).height() - $('body').offset().top