Find what the hell to scroll

Window vs Body scrolling

var $docEl = $( document.documentElement ),
    $body = $( document.body ),
    // if docEl has a scrollTop, well, that kinda answers our question
    $scrollable = $docEl.scrollTop() ? $docEL : 
        $body.scrollTop( $body.scrollTop() + 1 ).scrollTop() ? $body : $docEl;		
			
		
    // its like we can already tell!
    if ( windowST ) {
        $scrollable = $docEl;
    }else {
        // if adding one to body doesn't help us out, we're in docEl land
        if ( !$scrollable.scrollTop( bodyST + 1 ).scrollTop() ) {
	    $scrollable = $docEl;
        }
    }