Javascript - Get the width of an undefined element

Question

I have a div element, that has no defined width or height. It holds other elements, and molds on their size. I need to get the final size of the div, without being able to check the sizes of the elements inside of it (dynamic elements).

I tried parsing all the properties of the object, but found nothing, all were "undefined".

Any thoughts?

Many thanks

Later edit:

I have

<div id="xxx" style="position:relative;">  
    aaaa
</div>

I tried:

var a = mydiv.style.width;

But it did not work.

I also tried:

var getKeys = function (obj) {  
    var keys = [];

    for(var key in obj){  
        document.write(key+"="+obj.key+"<br>");  
    }  

    return keys;  
}  

getKeys(mydiv.style);  

To show all the properties, but none had any info.

The jQuery solution works perfectly, but getComputedStyle was what I was looking for, as I can't use jquery here.

Sorry for the short information.

Answer 1

Based on no information whatsoever about what you were doing, I'd suggest that you should (if possible) use the window.getComputedStyle() approach, which finds the properties of an object as rendered by the browser:

var elem = document.getElementById('elemId'),
    properties = window.getComputedStyle(elem, null),
    height = properties.height,
    width = properties.width;

If you have jQuery available, then you can simply use the width() and height() (or outerWidth()/outerHeight()) methods:

var height = $('#elem').height(),
    width = $('#elem').width();