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.

Answer 2

function getScrollTop(){
    if(typeof pageYOffset!= 'undefined'){
        //most browsers except IE before #9
        return pageYOffset;
    }
    else{
        var B= document.body; //IE 'quirks'
        var D= document.documentElement; //IE with doctype
        D= (D.clientHeight)? D: B;
        return D.scrollTop;
    }
}

alert(getScrollTop())

Answer 3

function getSize(method) {
  return document.documentElement[method] || document.body[method];
}
getSize("scrollTop");

Answer 4

I know its been quite a while since this thread was updated, but this is a function I created that allows developers to find the root element that actually hosts has a working "scrollTop" property. Tested on Chrome 42 and Firefox 37 for Mac OS X (10.9.5):

function getScrollRoot(){
    var html = document.documentElement, body = document.body,
        cacheTop = ((typeof window.pageYOffset !== "undefined") ? window.pageYOffset : null) || body.scrollTop || html.scrollTop, // cache the window's current scroll position
        root;

    html.scrollTop = body.scrollTop = cacheTop + (cacheTop > 0) ? -1 : 1;
    // find root by checking which scrollTop has a value larger than the cache.
    root = (html.scrollTop !== cacheTop) ? html : body;

    root.scrollTop = cacheTop; // restore the window's scroll position to cached value

    return root; // return the scrolling root element
}

// USAGE: when page is ready: create a global variable that calls this function.

var scrollRoot = getScrollRoot();

scrollRoot.scrollTop = 10; // set the scroll position to 10 pixels from the top
scrollRoot.scrollTop = 0; // set the scroll position to the top of the window

I hope you find this useful! Cheers.

Answer 5

No need extra library, use this snippet:

const scrollTop = 
    (window.pageYOffset !== undefined) ? 
     window.pageYOffset :
    (document.documentElement || document.body.parentNode || document.body).scrollTop;