getFixedPositionOffsetParent.js

import getStyleComputedProperty from './getStyleComputedProperty';
import isIE from './isIE';
/**
 * Finds the first parent of an element that has a transformed property defined
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} first transformed parent or documentElement
 */

export default function getFixedPositionOffsetParent(element) {
  // This check is needed to avoid errors in case one of the elements isn't defined for any reason
   if (!element || !element.parentElement || isIE()) {
    return document.documentElement;
  }
  let el = element.parentElement;
  while (el && getStyleComputedProperty(el, 'transform') === 'none') {
    el = el.parentElement;
  }
  return el || document.documentElement;

}