<pre> 
function getScrollbarWidth() { 
 
	// Creating invisible container 
	const outer = document.createElement('div'); 
	outer.style.visibility = 'hidden'; 
	outer.style.overflow = 'scroll'; // forcing scrollbar to appear 
	outer.style.msOverflowStyle = 'scrollbar'; // needed for WinJS apps 
	document.body.appendChild(outer); 
 
	// Creating inner element and placing it in the container 
	const inner = document.createElement('div'); 
	outer.appendChild(inner); 
 
	// Calculating difference between container's full width and the child width 
	const scrollbarWidth = (outer.offsetWidth - inner.offsetWidth); 
 
	// Removing temporary elements from the DOM 
	outer.parentNode.removeChild(outer); 
 
	return scrollbarWidth; 
} 
</pre>
<hr>
<p>åç §å <a href="https://stackoverflow.com/questions/13382516/getting-scroll-bar-width-using-javascript" rel="noopener noreferrer" target="_blank">Getting scroll bar width using JavaScript</a></p>