import { isWindow } from '/@/utils/is';

let scrollBarWidth: number;

export default function (): number {
  if (!isWindow) return 0;
  if (scrollBarWidth !== undefined) return scrollBarWidth;

  const outer = document.createElement('div');
  outer.className = 'scrollbar__wrap';
  outer.style.visibility = 'hidden';
  outer.style.width = '100px';
  outer.style.position = 'absolute';
  outer.style.top = '-9999px';
  document.body.appendChild(outer);

  const widthNoScroll = outer.offsetWidth;
  outer.style.overflow = 'scroll';

  const inner = document.createElement('div');
  inner.style.width = '100%';
  outer.appendChild(inner);

  const widthWithScroll = inner.offsetWidth;
  const parentNode = outer.parentNode;
  parentNode && parentNode.removeChild(outer);
  scrollBarWidth = widthNoScroll - widthWithScroll;

  return scrollBarWidth;
}