将对象的平面数组转换为对象的嵌套数组

const users = [
  { id: 1, name: 'Alice', parentId: null },
  { id: 2, name: 'Bob', parentId: 1 },
  { id: 3, name: 'Charlie', parentId: 1 },
  { id: 4, name: 'David', parentId: 2 },
  { id: 5, name: 'Eve', parentId: 3 }
];

function groupUsers(users) {
  const map = new Map();
  const roots = [];

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

  users.forEach(user => {
    if (user.parentId === null) {
      roots.push(map.get(user.id));
    } else {
      const parent = map.get(user.parentId);
      if (parent) {
        parent.children.push(map.get(user.id));
      }
    }
  });

  return roots;
}

const nestedUsers = groupUsers(users);
console.log(nestedUsers);

function groupUsers(users) {
  const map = new Map();
  const roots = [];

  users.forEach(user => {
    console.log('Mapping user:', user);
    map.set(user.id, { ...user, children: [] });
  });

  users.forEach(user => {
    console.log('Grouping user:', user);
    if (user.parentId === null) {
      console.log('Root user:', user);
      roots.push(map.get(user.id));
    } else {
      const parent = map.get(user.parentId);
      if (parent) {
        console.log('Adding child:', user, 'to parent:', parent);
        parent.children.push(map.get(user.id));
      } else {
        console.error('Parent not found for user:', user);
      }
    }
  });

  return roots;
}