getScrollParent.ts

export default function getScrollParent(node?: Node | null) {
  if (!(node instanceof HTMLElement)) return null;
  if (typeof window.getComputedStyle !== 'function') return null;

  const overflowY = window.getComputedStyle(node).overflowY || 'visible';
  const isScrollable = /^(visible|hidden)/.test(overflowY);

  if (isScrollable && node.scrollHeight >= node.clientHeight) {
    return node;
  }

  return getScrollParent(node.parentNode) || document.body;
}