嵌套对象数组上的 Javascript reduce 和 map

Question

我有一组对象

[
  {
    "country": "USA",
    "payment": [
      {
        "paymentType": "Visa",
        "count": 1000
      },
      {
        "paymentType": "MasterCard",
        "count": 1000
      }
    ]
  },
  {
    "country": "CANADA",
    "payment": [
      {
        "paymentType": "Visa",
        "count": 1000
      },
      {
        "paymentType": "MasterCard",
        "count": 1000
      }
    ]
  },
  {...}
]

我想把它改造成

[
["USA" , "VISA" , 10000 ], 
["USA","Mastercard",1000],
[countryName2, paymentType,count] , ...
]

有人可以帮我吗>？

我试着做：

const data2 = data.map(function(elem) {
  return [
    elem.country,
    elem.payment.map(b=> b.paymentType),
    elem.payment.map(c=>c.count),
  ]
})

但是我得到的 output 不是我想要的，如果有人可以展示如何去做，

Answer 1

您可以使用嵌套的 map 执行此操作，其中每个数组条目都是通过从前缀为 outer country的payment中提取数据来创建的。

 const data = [{"country":"USA","payment":[{"paymentType":"Visa","count":1000},{"paymentType":"MasterCard","count":1000}]},{"country":"CANADA","payment":[{"paymentType":"Visa","count":1000},{"paymentType":"MasterCard","count":1000}]}]; const data2 = data.flatMap(({ country, payment }) => payment.map(({ paymentType, count }) => [ country, paymentType, count ]) ); console.log(data2);

 .as-console-wrapper { max-height: 100%;important; }

外部 map 上的flatMap()删除了在结果中创建的额外嵌套级别。

Answer 2

您可以使用平面阵列 function。这里：

const data2 = data
  .map(state => state.payment.map(statePayment => [state.country, statePayment.paymentType, statePayment.count]))
  .flat();