按类型和总价格获取的对象数组[重复]答案

【问题标题】：Array of objects get by type and sum price [duplicate]按类型和总价格获取的对象数组[重复]
【发布时间】：2021-04-15 11:46:24
【问题描述】：

我有一个对象数组，由包含类型、数量、名称和其他元数据的对象组成。

看起来像：

[
    {
       "id":"31362",
       "quantity":"7",
       "type":"wood",
       "metadata":{
          "name":"Wood Pack"
       }
    },
    {
       "id":"31361",
       "quantity":"13",
       "type":"sand",
       "metadata":{
          "name":"Sand Pack"
       }
    },
    {
       "id":"29161",
       "quantity":"7",
       "type":"sand",
       "metadata":{
          "name":"Sand Pack"
       }
    },
    {
       "id":"31398",
       "quantity":"50000",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    },
    {
       "id":"31363",
       "quantity":"50000",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    },
    {
       "id":"31368",
       "quantity":"50000",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    },
    {
       "id":"30755",
       "quantity":"1",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    }
 ]

我想要实现的是最终得到另一个数组，该数组对于下面的每个 type 属性和数量的总和都有一个对象

例如

    [
   {
      type: 'wood',
      quantity: 7
   },
   {
      type: 'sand',
      quantity: 20
   }
   ....
]

【问题讨论】：

标签： javascript node.js arrays

【解决方案1】：

试试这个 for 循环过程。

let a = [
    {
       "id":"31362",
       "quantity":"7",
       "type":"wood",
       "metadata":{
          "name":"Wood Pack"
       }
    },
    {
       "id":"31361",
       "quantity":"13",
       "type":"sand",
       "metadata":{
          "name":"Sand Pack"
       }
    },
    {
       "id":"29161",
       "quantity":"7",
       "type":"sand",
       "metadata":{
          "name":"Sand Pack"
       }
    },
    {
       "id":"31398",
       "quantity":"50000",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    },
    {
       "id":"31363",
       "quantity":"50000",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    },
    {
       "id":"31368",
       "quantity":"50000",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    },
    {
       "id":"30755",
       "quantity":"1",
       "type":"energy",
       "metadata":{
          "name":"Energy Pack"
       }
    }
 ]
let b = {};
a.forEach((v)=>{b[v.type] = b[v.type]?b[v.type]+parseInt(v.quantity):parseInt(v.quantity)});

let new_arr = [];
for (const [key, value] of Object.entries(b)) {
  let temp = {type:key, quantity: value}
  new_arr.push(temp);
}

console.log(new_arr);

【讨论】：