树形数据扁平化&数组数据树形化

数据扁平化：        

let objArr = [
  {
    id: 1,
    name: '部门1',
    children: [
      {
        id: 2,
        name: '部门2',

        children: []
      },
      {
        id: 3,
        name: '部门3',
        children: [
          {
            id: 4,
            name: '部门4',
            children: [
              {
                id: 5,
                name: '部门5',
                children: []
              }
            ]
          }
        ]
      }
    ]
  }
]
let result = []
const flattenArr = (arr, curArr, pid) => {
  let tempArr = arr.reduce((pre, cur) => {
    pre.push({
      id: cur?.id,
      name: cur?.name,
      pid: pid
    })
    cur.children?.length &&
      arr.forEach((i) => {
        flattenArr(i.children, curArr, i.id)
      })
    return pre
  }, [])
  curArr.push(...tempArr)
}
flattenArr(objArr, result, 0)
console.log(result)
//结果
[
  { id: 5, name: '部门5', pid: 4 },
  { id: 4, name: '部门4', pid: 3 },
  { id: 2, name: '部门2', pid: 1 },
  { id: 3, name: '部门3', pid: 1 },
  { id: 1, name: '部门1', pid: 0 }
]

数组数据树形化：

let arr = [
  { id: 5, name: '部门5', pid: 4 },
  { id: 4, name: '部门4', pid: 3 },
  { id: 2, name: '部门2', pid: 1 },
  { id: 3, name: '部门3', pid: 1 },
  { id: 1, name: '部门1', pid: 0 }
]
const arrToTree = (arr, pid) => {
  let result = []
  handleArr(arr, result, pid)
  return result
}
const handleArr = (arr, result, pid) => {
  for (const item of arr) {
    if (item.pid == pid) {
      let newObj = { ...item, children: [] }
      result.push(newObj)
      handleArr(arr, newObj.children, item.id)
    }
  }
}

console.log(JSON.stringify(arrToTree(arr, 0)))
//结果
   [
    {
        "id": 1,
        "name": "部门1",
        "pid": 0,
        "children": [
            {
                "id": 2,
                "name": "部门2",
                "pid": 1,
                "children": []
            },
            {
                "id": 3,
                "name": "部门3",
                "pid": 1,
                "children": [
                    {
                        "id": 4,
                        "name": "部门4",
                        "pid": 3,
                        "children": [
                            {
                                "id": 5,
                                "name": "部门5",
                                "pid": 4,
                                "children": []
                            }
                        ]
                    }
                ]
            }
        ]
    }
]