展平并组合对象数组

Question

我有一个像这样的对象数组

[
   {
      "id":1,
      "name":"Competition One",
      "entrants": [
          {
              "id":1,
              "competitionId":1,
              "duration":"3 minutes",
           },
           {
              "id":2,
              "competitionId":1,
              "duration":"2 hours",
           },
      ]
   },
   {
      "id":2,
      "name":"Competition Two",
      "entrants": [
            {
              "id":3,
              "competitionId":2,
              "duration":"5 hours",
           },
      ]
   },
]

我想做的是得到一个只包含参赛者的平面数组，因此我正在这样做

const entrants = competitions.flatMap((comp) => {
    return comp.entrants;
});

这似乎可以解决问题。我现在有以下

[
   {
      "id":1,
      "competitionId":1,
      "duration":"3 minutes",
   },
   {
      "id":2,
      "competitionId":1,
      "duration":"2 hours",
   },
   {
      "id":3,
      "competitionId":2,
      "duration":"5 hours",
   }
]

但是，我想不通的是如何在上述数据中添加一个包含比赛名称的新字段。所以我追求的是这个

[
   {
      "id":1,
      "competitionId":1,
      "name": "Competition One"
      "duration":"3 minutes",
   },
   {
      "id":2,
      "competitionId":1,
      "name": "Competition One"
      "duration":"2 hours",
   },
   {
      "id":3,
      "competitionId":2,
      "name": "Competition Two"
      "duration":"5 hours",
   }
]

如何实现？我知道如何使用传统循环来做到这一点，但我试图强迫自己学习 ES6 的做事方式。这是 reduce 可以派上用场的地方吗？

感谢任何建议。

谢谢

Answer 1

映射时将name属性合并到comp.entrants中。

const entrants = competitions.flatMap((comp) => {
    return {name: comp.name, ...comp.entrants};
});

Answer 2

您可以使用嵌套映射，然后将对象与额外的对象合并属性:

let competitions = [{  "id":1, "name":"Competition One", "entrants": [{"id":1,"competitionId":1,"duration":"3 minutes",},{ "id":2,"competitionId":1,"duration":"2 hours",},]},{"id":2,"name":"Competition Two","entrants": [{"id":3,"competitionId":2,"duration":"5 hours",},]},]

let result = competitions.flatMap(({name, entrants}) =>
    entrants.map(entrant => ({name, ...entrant}))
);

console.log(result);

Answer 3

使用 Array#map 获取具有相应 competition 名称的每个 entrants 列表：

const competitions = [
  {
    "id":1,
    "name":"Competition One",
    "entrants": [ { "id":1, "competitionId":1, "duration":"3 minutes" }, { "id":2, "competitionId":1, "duration":"2 hours" } ]
  },
  {
    "id":2,
    "name":"Competition Two",
    "entrants": [ { "id":3, "competitionId":2, "duration":"5 hours" } ]
  }
];

const entrants = competitions.flatMap(({ name, entrants = [] }) =>
  entrants.map(entrant => ({ ...entrant, name }))
);

console.log(entrants);

展平并组合对象数组

Flatten and combining an Array of Objects

javascript

ecmascript-6