calculate the size of the scrollbar

scrollbarsize.js

var scrollbarSize = (function() {
	var inner = document.createElement( "div" ),
		outer = document.createElement( "div" );
	inner.style.width = "100%";
	inner.style.height = "60px";
	outer.style.position = "absolute";
	outer.style.top = "0";
	outer.style.left = "0";
	outer.style.visibility = "hidden";
	outer.style.width = "50px";
	outer.style.height = "50px";
	outer.style.overflow = "hidden";
	outer.appendChild( inner );
	document.body.appendChild( outer );
	var sizeBefore = inner.offsetWidth;
	outer.style.overflow = "scroll";
	var sizeAfter = inner.offsetWidth;
	if ( sizeBefore === sizeAfter ) {
		sizeAfter = outer.clientWidth;
	}
	document.body.removeChild( outer );
	return ( sizeBefore - sizeAfter );
}());