JSFiddle - React, Tailwind, and code Playground

HTML

<div

JavaScript

function scrollbarWidth() {
    var block = $('<div>').css({'height':'50px','width':'50px'}),
        indicator = $('<div>').css({'height':'200px'});
    
    $('body').append(block.append(indicator));
    var w1 = $('div', block).innerWidth();    
    block.css('overflow-y', 'scroll');
    var w2 = $('div', block).innerWidth();
    $(block).remove();
    return (w1 - w2);
}

alert(scrollbarWidth());