Cross-browser method for detecting the scrollTop of the browser window

Question

What is the best cross-browser way to detect the scrollTop of the browser window? I prefer not to use any pre-built code libraries because this is a very simple script, and

Answer 1

YUI 2.8.1 code does this:

function getDocumentScrollTop(doc) 
{
   doc = doc || document;

   //doc.body.scrollTop is IE quirkmode only
   return Math.max(doc.documentElement.scrollTop, doc.body.scrollTop);
}

I think jQuery 1.4.2 code (a bit translated for humans) and supposing I understood it properly does this:

function getDocumentScrollTop(doc) 
{
   doc = doc || document;
   win = doc.defaultView || doc.parentWindow; //parentWindow is for IE < 9

   result = 0;
   if("pageYOffset" in win) //I'don't know why they use this, probably they tested it to be faster than doing: if(typeof win.pageYOffset !== 'undefined')
      result = win.pageYOffset;
   else
      result = (jQuery.support.boxModel && document.documentElement.scrollTop) || 
               document.body.scrollTop;

   return result;
}

Unfortunatley extracting the value of jQuery.support.boxModel is almost impossible because you would have to add a temporary child element into document and do the same tests jQuery does.