js id pid 递归

const data = [
  { id: 1, pid: 0, name: 'Root' },
  { id: 2, pid: 1, name: 'Child 1' },
  { id: 3, pid: 1, name: 'Child 2' },
  { id: 4, pid: 2, name: 'Grandchild 1' },
  { id: 5, pid: 2, name: 'Grandchild 2' },
];

function buildTree(data, parentId = 0) {
  return data
    .filter(item => item.pid === parentId)
    .map(item => ({
      ...item,
      children: buildTree(data, item.id)
    }));
}

const tree = buildTree(data);
console.log(JSON.stringify(tree, null, 2));

function buildTreeIterative(data) {
  const map = new Map();
  const roots = [];

  data.forEach(item => {
    map.set(item.id, { ...item, children: [] });
  });

  data.forEach(item => {
    if (item.pid === 0) {
      roots.push(map.get(item.id));
    } else {
      const parent = map.get(item.pid);
      if (parent) {
        parent.children.push(map.get(item.id));
      }
    }
  });

  return roots;
}

const treeIterative = buildTreeIterative(data);
console.log(JSON.stringify(treeIterative, null, 2));