How can I get the browser's scrollbar sizes?

Question

How can I determine the height of a horizontal scrollbar, or the width of a vertical one, in JavaScript?

Answer 1

function getWindowScrollBarHeight() {
    let bodyStyle = window.getComputedStyle(document.body);
    let fullHeight = document.body.scrollHeight;
    let contentsHeight = document.body.getBoundingClientRect().height;
    let marginTop = parseInt(bodyStyle.getPropertyValue('margin-top'), 10);
    let marginBottom = parseInt(bodyStyle.getPropertyValue('margin-bottom'), 10);
    return fullHeight - contentHeight - marginTop - marginBottom;
  }

Answer 2

window.scrollBarWidth = function() {
  document.body.style.overflow = 'hidden'; 
  var width = document.body.clientWidth;
  document.body.style.overflow = 'scroll'; 
  width -= document.body.clientWidth; 
  if(!width) width = document.body.offsetWidth - document.body.clientWidth;
  document.body.style.overflow = ''; 
  return width; 
} 

Answer 3

function getScrollBarWidth() {
    return window.innerWidth - document.documentElement.clientWidth;
}

Most of the browser use 15px for the scrollbar width

Answer 4

Using jQuery, you can shorten Matthew Vines answer to:

function getScrollBarWidth () {
    var $outer = $('<div>').css({visibility: 'hidden', width: 100, overflow: 'scroll'}).appendTo('body'),
        widthWithScroll = $('<div>').css({width: '100%'}).appendTo($outer).outerWidth();
    $outer.remove();
    return 100 - widthWithScroll;
};

Answer 5

The way Antiscroll.js does it in it's code is:

function scrollbarSize () {
  var div = $(
      '<div class="antiscroll-inner" style="width:50px;height:50px;overflow-y:scroll;'
    + 'position:absolute;top:-200px;left:-200px;"><div style="height:100px;width:100%"/>'
    + '</div>'
  );

  $('body').append(div);
  var w1 = $(div).innerWidth();
  var w2 = $('div', div).innerWidth();
  $(div).remove();

  return w1 - w2;
};

The code is from here: https://github.com/LearnBoost/antiscroll/blob/master/antiscroll.js#L447

Answer 6

I made an updated version of @Matthew Vines answer.

It's easier to read, easier to understand. It doesn't require an inner element. The element created to get the scroll bar width has a 100% height/width so it doesn't create any visible scroll bar on the body on lower end PCs/mobiles which could take a bit more time to create the element, get the widths, and finally remove the element.

const getScrollBarWidth = () => {
  const e = document.createElement('div');
  Object.assign(e.style, {
    width: '100%',
    height: '100%',
    overflow: 'scroll',
    position: 'absolute',
    visibility: 'hidden',
    top: '0',
    left: '0',
  });

  document.body.appendChild(e);

  const scrollbarWidth = e.offsetWidth - e.clientWidth;

  document.body.removeChild(e);

  return scrollbarWidth;
};

console.log(getScrollBarWidth());

I do recommend to check for the scroll bar width only once, at page load (except if it doesn't fit your needs) then store the result in a state/variable.