Calculate scroll bar width cross-browser

scrollbarWidth.js

function getScrollBarWidth() {
	var inner = document.createElement('p');
	inner.style.width = "100%";
	inner.style.height = "200px";

	var outer = document.createElement('div');
	outer.style.position = "absolute";
	outer.style.top = "0px";
	outer.style.left = "0px";
	outer.style.visibility = "hidden";
	outer.style.width = "200px";
	outer.style.height = "150px";
	outer.style.overflow = "hidden";
	outer.appendChild(inner);

	document.body.appendChild(outer);
	var w1 = inner.offsetWidth;
	outer.style.overflow = 'scroll';
	var w2 = inner.offsetWidth;

	if (w1 == w2) {
		w2 = outer.clientWidth;
	}

	document.body.removeChild(outer);

	return (w1 - w2);
}