Question

I want to return, say, the width or height of a certain element without having set them beforehand with CSS or HTML. Is that even possible? Do you always have to set those before you can use them?

Answer 1

Use the getComputedStyle() method on the element. There are some little differences across browsers on how this method works, but for the height and width properties it works the same.

So, an example would be:

var el     = document.getElementById('el'),
    height = el.getComputedStyle('height'),
    width  = el.getComputedStyle('width');

Here’s a fiddle: http://jsfiddle.net/joplomacedo/7Qr83/