将原始list转化为树形结构

// 原始 list 如下
let list =[
    {id:1,name:'部门A',parentId:0},
    {id:2,name:'部门B',parentId:0},
    {id:3,name:'部门C',parentId:1},
    {id:4,name:'部门D',parentId:1},
    {id:5,name:'部门E',parentId:2},
    {id:6,name:'部门F',parentId:3},
    {id:7,name:'部门G',parentId:2},
    {id:8,name:'部门H',parentId:4}
];

// 转换后的结果如下
let result = [
    {
      id: 1,
      name: '部门A',
      parentId: 0,
      children: [
        {
          id: 3,
          name: '部门C',
          parentId: 1,
          children: [
            {
              id: 6,
              name: '部门F',
              parentId: 3
            }, {
              id: 16,
              name: '部门L',
              parentId: 3
            }
          ]
        },
        {
          id: 4,
          name: '部门D',
          parentId: 1,
          children: [
            {
              id: 8,
              name: '部门H',
              parentId: 4
            }
          ]
        }
      ]
    },
  ···
];

实现的函数如下：

function convert(list) {
  const res = []
  const map = list.reduce((res, v) => (res[v.id] = v, res), {})
  for (const item of list) {
    if (item.parentId === 0) {
      res.push(item)
      continue
    }
    if (item.parentId in map) {
      const parent = map[item.parentId]
      parent.children = parent.children || []
      parent.children.push(item)
    }
  }
  return res
}