一维数组转成树形数组

const target = [
  {
    id: 1,
    name: '流程管理',
    children: [
      { id: 2, name: '请假流程' },
      { id: 3, name: '报销流程' },
      {
        id: 4,
        name: '借款流程',
        children: [{ id: 5, name: '备用金流程' }],
      },
    ],
  },
  {
    id: 6,
    name: '系统管理',
    children: [
      { id: 7, name: '用户管理' },
      { id: 8, name: '角色管理' },
    ],
  },
]
const data = [
  { id: 1, name: '流程管理', parent_id: 0 },
  { id: 2, name: '请假流程', parent_id: 1 },
  { id: 3, name: '报销流程', parent_id: 1 },
  { id: 4, name: '借款流程', parent_id: 1 },
  { id: 5, name: '备用金流程', parent_id: 4 },
  { id: 6, name: '系统管理', parent_id: 0 },
  { id: 7, name: '用户管理', parent_id: 6 },
  { id: 8, name: '角色管理', parent_id: 6 },
]

// 一维转树形  reduce()
const arrayToTree = (arr, pid) => {
  return arr.reduce((res, current) => {
    if (current['parent_id'] === pid) {
      current.children = arrayToTree(arr, current['id'])
      return res.concat(current)
    }
    return res
  }, [])
}

// console.log(arrayToTree(data, 0))

// 一维转树形  递归一
const treeToArray = arr => {
  const res = []
  arr.forEach(element => {
    const { children, ...rest } = element
    res.push({ ...rest })
    if (element?.children?.length > 0) {
      res.push(...treeToArray(children))
    }
  })
  return res
}

// console.log(treeToArray(target))

// 一维转树形 递归二
const formatData = (data, pid) => {
  const root = data.filter(item => {
    return item['parent_id'] === pid
  })

  return root.map(pItem => {
    return { ...pItem, children: [...formatData(data, pItem['id'])] }
  })
}

// console.log(formatData(data, 0))

// 一维转树形 递归三
const getTreeList = (data, pid, res) => {
  for (const list of data) {
    if (list['parent_id'] === pid) {
      res.push(list)
    }
    for (const root of res) {
      root.children = []
      getTreeList(data, root.id, root.children)
      if (root.children.length === 0) {
        delete root.children
      }
    }
  }
  return res
}

// 一维转树形 不使用递归
const filterTreeList = data => {
  const res = []
  data.forEach(item => {
  
    item.children = data.filter(i => {
      return i['parent_id'] === item.id
    })

    if (item.children.length === 0) {
      delete item.children
    }
     if (item['parent_id'] === 0) {
       res.push(item)
     }
    res.push(item)
  })
  return res
}

console.log(filterTreeList(data))