js 一维数组，转成嵌套数组

// 情况一：

// 数据源
var egs = [
            {name_1: 'name_1...'},
            {name_2: 'name_4...'},
            {name_3: 'name_3...'},
            {name_0: 'name_0...'},
        ].reverse()
// 最终想要的数据形式
        // {name_1: 'name_1...',
        //     children: [
        //         {name_2: 'name_2...',
        //             children: [
        //                 {name_3: 'name_3...'},
        //             ]
        //         }
        //     ]
        // }

        var result = {}
        var key ='children'
        s(egs)

        function s(arrs) {
            arrs.forEach((o, i) => {
                console.log('---'+ i + ': ', result)
                if (!result[key]) {
                    result[key] = [o]
                } else {
                    o[key] = [result]
                    result = o
                }
             })
        }

        console.log(result)

// 情况二：
// pId 对应父级 id

let arr = [

    { pId: '-1', id: '0', name: '父级1' },

    { pId: '0', id: '1', name: '父级1-1' },

    { pId: '0', id: '2', name: '父级1-2' },

    { pId: '2', id: '21', name: '子级21' },

  ]

  function buildTree (arr) {

    let temp = {}

    let tree = {}

    // 数组转 键值对

    arr.forEach(item => {

      temp[item.id] = item

    })

    let tempKeys = Object.keys(temp)

    tempKeys.forEach(key => {

      // 获取当前项

      let item = temp[key]

      // 当前项 pId

      let _itemPId = item.pId

      // 获取父级项

      let parentItemByPid = temp[_itemPId]

      if (parentItemByPid) {

        if (!parentItemByPid.children) {

          parentItemByPid.children = []

        }

        parentItemByPid.children.push(item)

      } else {

        tree[item.id] = item

      }

    })

    // 对象转数组并返回

    return Object.keys(tree).map(key => tree[key])

  }