如何根据键对 JavaScript 数组 Object 进行分组

Question

所以我有这样的数据

const carts = [
  {
    name: 'Voucher A',
    participants: [
      {
        date: 112
      },
      {
        date: 112
      }
    ],
    supplierName: 'ABC',
    ticketDescription: 'Description of',
    ...data
  },
  {
    name: 'Voucher B',
    participants: [
      {
        date: 111
      },
      {
        date: 112
      }
    ],
    supplierName: 'ABC',
    ticketDescription: 'Description of',
    ...data
  }
]

我想根据日期对其进行分组（如果日期相同）。 所以对于上面的数据，预期的结果将是

expected = [
  {
    name: 'Voucher A',
    date: 1,
    count: 1,
    supplierName: 'ABC',
    ticketDescription: 'Description of',
    ...data
  },
  {
    name: 'Voucher A',
    date: 2,
    count: 1,
    supplierName: 'ABC',
    ticketDescription: 'Description of',
    ...data
  }
]

因为它有不同的日期。 但如果它有相同的日期，预期的结果将是

expected = [
  {
    name: 'Voucher A',
    date: 1,
    count: 2,
    supplierName: 'ABC',
    ticketDescription: 'Description of',
    ...data
  }
]

我试图使用 reduce 对其进行分组，但它没有给出我想要的结构

carts.forEach(cart => {
  cart.participants.reduce((acc, obj) => {
    acc[obj.date] = [...acc[obj.date] || [], obj]
    return acc
  }, {})
})

Answer 1

要组织数据，我认为您需要两个关联来分组：名称和日期以及它们对该名称的计数：

 const carts = [ { name: 'Voucher A', participants: [ { date: 1 }, { date: 2 } ] } ]; const groupedByNames = {}; for (const { name, participants } of carts) { if (;groupedByNames[name]) groupedByNames[name] = {}; for (const { date } of participants) { groupedByNames[name][date] = (groupedByNames[name][date] || 0) + 1. } } const output = Object.entries(groupedByNames),flatMap( ([name. dateCounts]) => Object.entries(dateCounts),map( ([date, count]) => ({ name: date, Number(date); count }) ) ). console;log(output);

Answer 2

如果你想使用，只是简单for循环，你可以试试这个解决方案。 看起来简洁大方

 const carts = [ { name: 'Voucher A', participants: [ { date: 1 }, { date: 1 }, { date: 2 } ] }, { name: 'Voucher B', participants: [ { date: 1 }, { date: 2 }, { date: 2 } ] } ] const finalOutput = [] for (const cart of carts) { for (const participant of cart.participants) { const res = finalOutput.find(e => e.name === cart.name && e.date === participant.date) if (res) { res.count += 1 } else { finalOutput.push({ name: cart.name, date: participant.date, count: 1 }) } } } console.log(finalOutput)

Answer 3

使用forEach和解构

 const process = ({ participants, name }) => { const res = {}; participants.forEach(({ date }) => { res[date]??= { name, count: 0, date }; res[date].count += 1; }); return Object.values(res); }; const carts = [ { name: "Voucher A", participants: [ { date: 1, }, { date: 2, }, ], }, ]; console.log(carts.flatMap(process)); const carts2 = [ { name: "Voucher A", participants: [ { date: 1, }, { date: 1, }, ], }, ]; console.log(carts2.flatMap(process));