dom-helpers/esm/scrollParent.js

tiny modular DOM lib for ie9+

/* eslint-disable no-cond-assign, no-continue */

import css from "./css.js";
import height from "./height.js";
import isDocument from "./isDocument.js";

/**
 * Find the first scrollable parent of an element.
 *
 * @param element Starting element
 * @param firstPossible Stop at the first scrollable parent, even if it's not currently scrollable
 */
export default function scrollParent(element, firstPossible) {
  const position = css(element, 'position');
  const excludeStatic = position === 'absolute';
  const ownerDoc = element.ownerDocument;
  if (position === 'fixed') return ownerDoc || document;

  // @ts-ignore
  while ((element = element.parentNode) && !isDocument(element)) {
    const isStatic = excludeStatic && css(element, 'position') === 'static';
    const style = (css(element, 'overflow') || '') + (css(element, 'overflow-y') || '') + css(element, 'overflow-x');
    if (isStatic) continue;
    if (/(auto|scroll)/.test(style) && (firstPossible || height(element) < element.scrollHeight)) {
      return element;
    }
  }
  return ownerDoc || document;
}