JavaScript 原生 groupBy 归约

Question

我正在使用 JavaScript 原生 reduce，但是我想稍微改变分组以获得我想要的结果。 我有一个数组如下:

const people = [
  {name: "John", age: 23, city: "Seattle", state: "WA"},
  {name: "Mark", age: 25, city: "Houston", state: "TX"},
  {name: "Luke", age: 26, city: "Seattle", state: "WA"},
  {name: "Paul", age: 28, city: "Portland", state: "OR"},
  {name: "Matt", age: 21, city: "Oakland", state: "CA"},
  {name: "Sam", age: 24, city: "Oakland", state: "CA"}
]

我想把它分组，改成这样:

const arranged = [
  {
    city: "Seattle",
    state: "WA",
    persons: [
      { name: "John", age: 23 },
      {name: "Luke", age: 26}
    ]
  },
    {
    city: "Houston",
    state: "TX",
    persons: [
      {name: "Mark", age: 25}
    ]
  },
  {
    city: "Portland",
    state: "OR",
    persons : [
      {name: "Paul", age: 28}
    ]
  },
  {
    city: "Oakland",
    state: "CA",
    persons: [
      {name: "Matt", age: 21},
      {name: "Sam", age: 24}
    ]
  }
]

Answer 1

你可以使用 Map和一个字符串化对象作为分组的键。

稍后用键和分组的人的对象渲染想要的数组。

var people = [{ name: "John", age: 23, city: "Seattle", state: "WA" }, { name: "Mark", age: 25, city: "Houston", state: "TX" }, { name: "Luke", age: 26, city: "Seattle", state: "WA" }, { name: "Paul", age: 28, city: "Portland", state: "OR" }, { name: "Matt", age: 21, city: "Oakland", state: "CA" }, { name: "Sam", age: 24, city: "Oakland", state: "CA" }],
    arranged = Array.from(
        people.reduce((m, o) => {
            var key = JSON.stringify(Object.assign(...['city', 'state'].map(k => ({ [k]: o[k] }))));
            return m.set(key, (m.get(key) || []).concat({ name: o.name, age: o.age }));
        }, new Map),
        ([key, persons]) => Object.assign(JSON.parse(key), { persons })
    );

console.log(arranged);

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