使用 JavaScript 组合和分组数组

Question

我有两组数据需要以某种方式组合和分组。

第一组数据：

let overallCert =
[
  {
      "id": "1",
      "entity_id": "3",
      "status": "Certified",
  },
  {
      "id": "379",
      "entity_id": "417",
      "status": "Certified",
  }
];

第二组数据：

let userCerts =
[
  {
      "id": "640",
      "entity_id": "417",
      "method": "Field Study",
      "strand": "",
      "date_completed": "2016-07-15T08:00:00.000Z"
  },
  {
      "id": "814",
      "entity_id": "417",
      "method": "Field Study",
      "date_completed": "2019-07-15T08:00:00.000Z"
  },
  {
      "id": "844",
      "entity_id": "3",
      "method": "Online",
      "date_completed": "2022-03-28T08:00:00.000Z"
  },
  {
      "id": "845",
      "entity_id": "3",
      "method": "Field Study",
      "date_completed": "2022-03-28T08:00:00.000Z"
  }
];

我想通过 entity_id 合并和分组这些对象数组以在下面创建此输出...

期望的输出：

let desiredOutput = 
[
  [
    [
      {
        "id": "640",
        "entity_id": "417",
        "method": "Field Study",
        "date_completed": "2016-07-15T08:00:00.000Z"
      },
      {
        "id": "814",
        "entity_id": "417",
        "method": "Field Study",
        "date_completed": "2019-07-15T08:00:00.000Z"
      },
    ],
    [
      {
        "id": "379",
        "entity_id": "417",
        "status": "Certified",
      }
    ]
  ],
  [
    [
      {
        "id": "844",
        "entity_id": "3",
        "method": "Online",
        "date_completed": "2022-03-28T08:00:00.000Z"
      },
      {
        "id": "845",
        "entity_id": "3",
        "method": "Field Study",
        "date_completed": "2022-03-28T08:00:00.000Z"
      }
    ],
    [
      {
        "id": "379",
        "entity_id": "417",
        "status": "Certified",
      }
    ]
  ]
];

到目前为止，我已经做到了：

let certsDataCombined = overallCert.map(item => ({ ...item,
  0 : userCerts.filter(c => c.entity_id == item.entity_id)
}));

let userCertsGroupBy = groupBy(certsDataCombined, "entity_id");

function groupBy(arr, prop) {
  const map = new Map(Array.from(arr, obj => [obj[prop], []]));
  arr.forEach(obj => map.get(obj[prop]).push(obj));
  return Array.from(map.values());
}

这段代码几乎可以解决问题，但我需要将 overallCert 数据封装在它自己的数组中，而且嵌套有点偏离。是当前输出：

Answer 1

似乎您可以通过将每个 overallCert 映射到一个新数组然后使用 filter

拉出匹配的 userCerts 来构建输出

const overallCert = [{"id":"1","entity_id":"3","status":"Certified"},{"id":"379","entity_id":"417","status":"Certified"}];
const userCerts = [{"id":"640","entity_id":"417","method":"Field Study","strand":"","date_completed":"2016-07-15T08:00:00.000Z"},{"id":"814","entity_id":"417","method":"Field Study","date_completed":"2019-07-15T08:00:00.000Z"},{"id":"844","entity_id":"3","method":"Online","date_completed":"2022-03-28T08:00:00.000Z"},{"id":"845","entity_id":"3","method":"Field Study","date_completed":"2022-03-28T08:00:00.000Z"}];

const result = overallCert.map(cert => [
  userCerts.filter(({ entity_id }) => cert.entity_id === entity_id),
  [ cert ]
]);

console.log(result);

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

请注意，顺序是基于 overallCert 而不是您问题中的 userCerts。

以上是 O(n^2) 的时间复杂度，这并不好。您可以通过首先按 entity_id 对 O(n) 对两个数组进行分组来改进这一点。这也可以让您像示例中那样按 userCerts 排序。

const overallCert = [{"id":"1","entity_id":"3","status":"Certified"},{"id":"379","entity_id":"417","status":"Certified"}];
const userCerts = [{"id":"640","entity_id":"417","method":"Field Study","strand":"","date_completed":"2016-07-15T08:00:00.000Z"},{"id":"814","entity_id":"417","method":"Field Study","date_completed":"2019-07-15T08:00:00.000Z"},{"id":"844","entity_id":"3","method":"Online","date_completed":"2022-03-28T08:00:00.000Z"},{"id":"845","entity_id":"3","method":"Field Study","date_completed":"2022-03-28T08:00:00.000Z"}];

// Helper function since Map is missing this
Map.prototype.getOrDefault = function(key, defaultValue) {
  return (this.has(key) ? this : this.set(key, defaultValue)).get(key);
};

// Groups certs by entity_id
const reducer = (map, cert) => (
  map.getOrDefault(cert.entity_id, []).push(cert),
  map
);

const overallCertsByEntityId = overallCert.reduce(reducer, new Map());
const userCertByEntityId = userCerts.reduce(reducer, new Map());

const result = Array.from(userCertByEntityId, ([key, certs]) => [
  certs,
  overallCertsByEntityId.get(key)
]);

console.log(result);

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

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