Measure scrollbar width and height 📐

January 15, 2019 • 1 min read

What's the point of this? 🧐

I noticed an irritating thing when I developed a modal component. The most common thing with modals is that you set overflow: hidden on the <body> to prevent the scroll. If the browser has a scrollbar that takes up space the overflow: hidden will make the content jump to the right, and then jump back to the left when the modal is closed. This is very annoying and gives a bad impression. So how can we solve this? First we have to measure the scollbar...

Can we measure the scrollbar? 😲

Yes we can, and it's quite simple. We need to create a <div> and inject it into the DOM, and then measure the scrollbar of that element. Sounds quite simple, right?

Some styling is necessary for this measuring to work. First we need to append some offscreen positioning so the user doesn't see it, then give it overflow: scroll so the scrollbar is visible for our measurement.

With the styled element in the page we can measure the scrollbar. To get the width we'll subtract offsetWidth with the clientWidth, and if you want the height you'll just use offsetHeight and clientHeight instead.

The last step is removing the <div> from the DOM. Here you can see the function:

export const getScrollbarSize = () => {
  const { body } = document;
  const scrollDiv = document.createElement('div');

  // Append element with defined styling
  scrollDiv.setAttribute(
    'style',
    'width: 1337px; height: 1337px; position: absolute; left: -9999px; overflow: scroll;'
  );
  body.appendChild(scrollDiv);

  // Collect width & height of scrollbar
  const calculateValue = (type) =>
    scrollDiv[`offset${type}`] - scrollDiv[`client${type}`];
  const scrollbarWidth = calculateValue('Width');
  const scrollbarHeight = calculateValue('Height');

  // Remove element
  body.removeChild(scrollDiv);

  return {
    width: scrollbarWidth,
    height: scrollbarHeight
  };
};

With getScrollbarSize() function we're getting both the width and height of the scrollbar. So how did this function solve my problem with the modal? I just appended margin-right with the width amount of the scrollbar on the content container.

An example of how to access it you simple do something like this:

import { getScrollbarSize } from './getScrollbarSize';

const { height, width } = getScrollbarSize();
console.log(width); // Width of scrollbar
console.log(height); // Height of scrollbar

Congratulations 🎉

You just learned how easy it is to measure the width and height of the scrollbar. I hope you find this useful. Peace ☮