获得两个DOM元素的公共父级

function findCommonAncestor(element1, element2) {
  let parents1 = getParents(element1);
  let parents2 = getParents(element2);
  let commonAncestor = null;

  for (let i = 0; i< parents1.length; i++) {
    for (let j = 0; j< parents2.length; j++) {
      if (parents1[i] === parents2[j]) {
        commonAncestor = parents1[i];
        break;
      }
    }
    if (commonAncestor) {
      break;
    }
  }
  return commonAncestor;
}

function getParents(element) {
  let parents = [];
  let parent = element.parentNode;
  while (parent) {
    parents.push(parent);
    parent = parent.parentNode;
  }
  return parents;
}