Binary Tree Level Order Traversal

function levelOrder(root) {
  if (!root) return [];
  const result = [];
  let queue = [root];
  while (queue.length) {
    const next = [];
    result.push(queue.map((node) => node.val));
    for (const node of queue) {
      if (node.left) next.push(node.left);
      if (node.right) next.push(node.right);
    }
    queue = next;
  }
  return result;
}