Smooth auto scrolling to bottom JavaScript when zoomed in

Question

I am using WebBrowser control to develop a browser app for Windows phone. I am trying to implement auto scroll to the bottom using the following code. It works fine but when the page is zoomed in document.body.scrollHeight in the the conditional check

if (document.body.scrollHeight > (document.documentElement.scrollTop + window.innerHeight))

is always larger causing the function to be called non stop and the terminating clearTimeout(timeOutDown) is never reached.

var timeOutDown;
function scrollToBottom() 
{ 
    clearTimeout(timeOut);
    if (document.body.scrollHeight > (document.documentElement.scrollTop + window.innerHeight))
    {
         window.scrollBy(0, 100); 
         window.external.notify(String(window.innerHeight));
         timeOutDown=setTimeout('scrollToBottom()',10);
    }
     else 
    {
        clearTimeout(timeOutDown);
    }
}

What is the correct way to do this considering user can zoom in/out the page?

Answer 1

Figured it out, just replace document.documentElement.scrollTop with window.pageYOffset. So the conditional statement becomes

if (document.body.scrollHeight > (window.pageYOffset + window.innerHeight))

This will take care of the zoom factor.