Get Scrollbar width

getScrollbarWidth

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;
  }

Credit: https://stackoverflow.com/questions/13382516/getting-scroll-bar-width-using-javascript