// Can do recursive approach except check the previousElementSibling and lastElementChild
function previousLeftSibling(root, target) {
  // If target is null, there is no previous left sibling
  if (!target) {
    return null;
  }
  // Check target's immediate previousElementSibling to see if there is a previous sibling on the same level
  if (target.previousElementSibling) {
    return target.previousElementSibling;
  }

  let parent = target.parentElement;
  while (parent) {
    parent = previousLeftSibling(root, parent);
    if (parent && parent.lastElementChild) {
      return parent.lastElementChild;
    }
  }

  return null;
}