javascript - javascript中数组如何分组

Question

嗨，我是 Java 脚本的新手，我正在使用 knex ORM 与数据库进行交互，我得到的结果行是 flat json，我需要以我在预期中提到的实际格式获得结果结果。我尝试了一些代码，但没有一个代码给我预期的结果。我已经提到了我尝试过的原型(prototype)代码以及代码的结果，它不是我想要的格式我怎样才能得到我在预期结果部分提到的实际结果，我怎样才能使用 lodash 或 ES6 实现相同的结果高阶函数。

var data= [
    {order_id: 1,kot_id: 10,price: 20,quantity: 2},
    {order_id: 1,kot_id: 10,price: 100,quantity: 1},
    {order_id: 1,kot_id: 10,price: 150,quantity: 1},
    {order_id: 1,kot_id: 11,price: 55,quantity: 1},
    {order_id: 1,kot_id: 11,price: 250,quantity: 3},
]



let objects = {}
let arr = []
result = data.forEach((item,index) => {
    if(!objects.order_id) {
        objects = {order_id: item.order_id,list: []}
        arr.push(objects)
    }
    if(!objects.kot_id) {
         objects.list.push({kot_id: item.kot_id,kot_list: []})

    }
    objects.list[index].kot_list.push({price: item.price,quantity: item.quantity})

})
console.log(JSON.stringify(arr,null,2))

RESULT OF THE ABOVE CODE
[

  {
    "order_id": 1,
    "list": [
      {
        "kot_id": 10,
        "kot_list": [
          {
            "price": 20,
            "quantity": 2
          }
        ]
      },
      {
        "kot_id": 10,
        "kot_list": [
          {
            "price": 100,
            "quantity": 1
          }
        ]
      },
      {
        "kot_id": 10,
        "kot_list": [
          {
            "price": 150,
            "quantity": 1
          }
        ]
      },
      {
        "kot_id": 11,
        "kot_list": [
          {
            "price": 55,
            "quantity": 1
          }
        ]
      },
      {
        "kot_id": 11,
        "kot_list": [
          {
            "price": 250,
            "quantity": 3
          },

        ]
      }
    ]
  }
]

EXPECTED RESULT

result = [
    {
        order_id: 1,
        list: [
            {
                kot_id: 10,
                kot_list : [
                    { price: 200,quantity: 2 },
                    {price: 100,quantity: 1},
                    {price: 150,quantity: 1}
                ]
            },
            {
                kot_id: 11,
                kot_list: [
                    {price: 55,quantity: 1},
                    {price: 250,quantity: 3}
                ]
            }
        ]
    }
]

Answer 1

lodash实用程序，如 groupBy和 mapValues应该做的工作。

Lodash 示例:

const data = [
    {order_id: 1, kot_id: 10, price: 20, quantity: 2},
    {order_id: 1, kot_id: 10, price: 100, quantity: 1},
    {order_id: 1, kot_id: 10, price: 150, quantity: 1},
    {order_id: 1, kot_id: 11, price: 55, quantity: 1},
    {order_id: 1, kot_id: 11, price: 250, quantity: 3},

    {order_id: 2, kot_id: 10, price: 150, quantity: 1},
    {order_id: 2, kot_id: 11, price: 55, quantity: 1},
    {order_id: 2, kot_id: 11, price: 250, quantity: 3},
]


const result = _(data)
  .groupBy('order_id')
  .mapValues((values, key) => {
    return _(values)
      .groupBy('kot_id')
      .map((list, id) => ({
        kot_id: id,
        kot_list: _.map(list, i => _.pick(i, ['price', 'quantity']))
      }))
      .value();
  })
  .map((list, order_id) => ({order_id, list}))
  .value();


console.log(JSON.stringify(result, null, 4));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

或者您可以简单地使用 ES6 实用程序来获得相同的结果:

普通 ES6 示例:

const data = [
    {order_id: 1, kot_id: 10, price: 20, quantity: 2},
    {order_id: 1, kot_id: 10, price: 100, quantity: 1},
    {order_id: 1, kot_id: 10, price: 150, quantity: 1},
    {order_id: 1, kot_id: 11, price: 55, quantity: 1},
    {order_id: 1, kot_id: 11, price: 250, quantity: 3},

    {order_id: 2, kot_id: 10, price: 150, quantity: 1},
    {order_id: 2, kot_id: 11, price: 55, quantity: 1},
    {order_id: 2, kot_id: 11, price: 250, quantity: 3},
]


const orderIds = [...new Set(data.map(i => i.order_id))];
const kotIds = [... new Set(data.map(i => i.kot_id))];

const result = orderIds.map(order_id => {
  return {
    order_id,
    list: kotIds
      .map(kot_id => {
        return {
          kot_id,
          kot_list: data
            .filter(i => i.order_id === order_id && i.kot_id === kot_id)
            .map(i => ({price: i.price, quantity: i.quantity}))
        }
      })
  };
});

console.log(JSON.stringify(result, null, 4));