npm_assets/node_modules/popper.js/src/utils/getScrollParent.js


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import getStyleComputedProperty from './getStyleComputedProperty';
import getParentNode from './getParentNode';

/**
 * Returns the scrolling parent of the given element
 * @method
 * @memberof Popper.Utils
 * @argument {Element} element
 * @returns {Element} scroll parent
 */
export default function getScrollParent(element) {
  // Return body, `getScroll` will take care to get the correct `scrollTop` from it
  if (!element) {
    return document.body
  }

  switch (element.nodeName) {
    case 'HTML':
    case 'BODY':
      return element.ownerDocument.body
    case '#document':
      return element.body
  }

  // Firefox want us to check `-x` and `-y` variations as well
  const { overflow, overflowX, overflowY } = getStyleComputedProperty(element);
  if (/(auto|scroll|overlay)/.test(overflow + overflowY + overflowX)) {
    return element;
  }

  return getScrollParent(getParentNode(element));
}