从数组列表创建数组树

function createArrayTree(arrayList) {
  const map = {}; // 哈希表用于存储每个元素的ID和对应的子节点数组
  const result = []; // 结果数组

  // 第一次遍历，记录每个元素的父子关系
  for (const item of arrayList) {
    const { id, parentId } = item;
    if (!map[id]) {
      map[id] = { children: [] };
    }
    map[id] = { ...item, children: map[id].children };
    const parent = parentId || '-';
    if (!map[parent]) {
      map[parent] = { children: [] };
    }
    map[parent].children.push(map[id]);
  }

  // 第二次遍历，找到根节点并添加到结果数组中
  for (const item of arrayList) {
    if (!item.parentId) {
      result.push(map[item.id]);
    }
  }

  return result;
}

// 示例数据
const arrayList = [
  { id: '1', name: 'Node 1', parentId: null },
  { id: '2', name: 'Node 2', parentId: '1' },
  { id: '3', name: 'Node 3', parentId: '1' },
  { id: '4', name: 'Node 4', parentId: '2' },
  { id: '5', name: 'Node 5', parentId: '2' },
  { id: '6', name: 'Node 6', parentId: '3' },
];

const arrayTree = createArrayTree(arrayList);
console.log(arrayTree);

[
  {
    id: '1',
    name: 'Node 1',
    parentId: null,
    children: [
      {
        id: '2',
        name: 'Node 2',
        parentId: '1',
        children: [
          { id: '4', name: 'Node 4', parentId: '2', children: [] },
          { id: '5', name: 'Node 5', parentId: '2', children: [] },
        ],
      },
      {
        id: '3',
        name: 'Node 3',
        parentId: '1',
        children: [
          { id: '6', name: 'Node 6', parentId: '3', children: [] },
        ],
      },
    ],
  },
]