如何在javascript中数组列表到树？

function buildTree(arr) {
  let map = {};
  let roots = [];

  // 将数组元素转换为节点对象，并以节点id为键存储在map中
  arr.forEach(item => {
    map[item.id] = { ...item, children: [] };
  });

  // 遍历节点对象，将每个节点添加到其父节点的children数组中
  for (let id in map) {
    let node = map[id];
    if (node.parentId) {
      map[node.parentId].children.push(node);
    } else {
      roots.push(node);
    }
  }

  return roots;
}

// 示例数据
let arr = [
  { id: 1, name: 'Node 1', parentId: null },
  { id: 2, name: 'Node 1.1', parentId: 1 },
  { id: 3, name: 'Node 1.2', parentId: 1 },
  { id: 4, name: 'Node 1.2.1', parentId: 3 },
  { id: 5, name: 'Node 2', parentId: null },
  { id: 6, name: 'Node 2.1', parentId: 5 },
];

let tree = buildTree(arr);
console.log(tree);