dom - How can I get an object's absolute position on the page in Javascript?

I want to get an object's absolute x,y position on the page in
Javascript. How can I do this?

I tried
obj.offsetTop and obj.offsetLeft, but
those only give the position relative to the parent element. I guess I could loop
through and add the parent's offset, and its parent's offset, and so on until I get to
the object with no parent, but it seems like there should be a better way. Googling
didn't turn up much, and even SO site search isn't finding
anything.

Also, I can't use
jQuery.

Answer

var cumulativeOffset =
            function(element) {
 var top = 0, left = 0;
 do {
 top +=
            element.offsetTop || 0;
 left += element.offsetLeft || 0;
 element =
            element.offsetParent;
 } while(element);

 return
            {
 top: top,
 left: left

            };
};

(Method
shamelessly stolen from PrototypeJS; code style, variable names and return value changed
to protect the innocent)