simplebar/src/scrollbar-width.js

import canUseDOM from 'can-use-dom';

let cachedScrollbarWidth = null;
let cachedDevicePixelRatio = null;

if (canUseDOM) {
  window.addEventListener('resize', () => {
    if (cachedDevicePixelRatio !== window.devicePixelRatio) {
      cachedDevicePixelRatio = window.devicePixelRatio;
      cachedScrollbarWidth = null;
    }
  });
}

export default function scrollbarWidth() {
  if (cachedScrollbarWidth === null) {
    if (typeof document === 'undefined') {
      cachedScrollbarWidth = 0;
      return cachedScrollbarWidth;
    }

    const body = document.body;
    const box = document.createElement('div');

    box.classList.add('simplebar-hide-scrollbar');

    body.appendChild(box);

    const width = box.getBoundingClientRect().right;

    body.removeChild(box);

    cachedScrollbarWidth = width;
  }

  return cachedScrollbarWidth;
}