将对象数组转换为树数据结构

const data = [
  { 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 1.1.1', parentId: 2 },
  { id: 5, name: 'Node 2', parentId: null },
  { id: 6, name: 'Node 2.1', parentId: 5 },
];

function arrayToTree(arr, parentId = null) {
  const tree = [];
  
  for (const item of arr) {
    if (item.parentId === parentId) {
      const children = arrayToTree(arr, item.id);
      if (children.length) {
        item.children = children;
      }
      tree.push(item);
    }
  }
  
  return tree;
}

const treeData = arrayToTree(data);
console.log(treeData);

[
  {
    id: 1,
    name: 'Node 1',
    parentId: null,
    children: [
      {
        id: 2,
        name: 'Node 1.1',
        parentId: 1,
        children: [
          {
            id: 4,
            name: 'Node 1.1.1',
            parentId: 2,
            children: []
          }
        ]
      },
      {
        id: 3,
        name: 'Node 1.2',
        parentId: 1,
        children: []
      }
    ]
  },
  {
    id: 5,
    name: 'Node 2',
    parentId: null,
    children: [
      {
        id: 6,
        name: 'Node 2.1',
        parentId: 5,
        children: []
      }
    ]
  }
]