Question

我有以下数据，我想返回years的（对象）数组，它们是不同的。

我尝试了以下功能，但在数组中获取了一个数组。

const data = [{
    id: 1,
    name: "test1",
    years: [{
      id: 1,
      name: "year1"
    }, {
      id: 2,
      name: "year2"
    }]
  },
  {
    id: 2,
    name: "test2",
    years: [{
      id: 1,
      name: "year1"
    }]
  },
]

let years = data.map((s) => {
  return s.years
})
let distinctYears = Array.from(new Set(years.map(c => c.id))).map(id => {
  return {
    id: id,
    name: years.find(c => c.id === id).name,
  }
})

console.log(distinctYears);

期望的结果：

[
  {id: 1, name: "year1"},
  {id: 2, name: "year2"}
]

Answer 1

由于s.years()是一个数组，并且data.map()返回一个结果数组，所以years必然是一个数组数组。

使用.map()来串联它们，而不是使用.reduce()。

const data = [{
    id: 1,
    name: "test1",
    years: [{
      id: 1,
      name: "year1"
    }, {
      id: 2,
      name: "year2"
    }]
  },
  {
    id: 2,
    name: "test2",
    years: [{
      id: 1,
      name: "year1"
    }]
  },
];

const years = data.reduce((a, {
  years
}) => a.concat(years), []);
let distinctYears = Array.from(new Set(years.map(c => c.id))).map(id => {
  return {
    id: id,
    name: years.find(c => c.id === id).name,
  }
});
console.log(distinctYears);

Answer 2

您可以通过多种方式执行此操作。这是一个，不是一线，而是分解为多个部分，以帮助我们了解发生了什么。

您的数据集：

let data =
[
  {
    id: 1,
    name: "test1",
    years: [{id: 1, name: "year1"}, {id: 2, name: "year2"} ]
  },
  {
    id: 2,
    name: "test2",
    years: [{id: 1, name: "year1"} ]
  },
]

使用.flatMap()创建一个包含所有项目的一级数组：

let allItems = data.flatMap((item) => {
    return item.years.map((year) => {
        return year
    })
})

获得不同的物品：

let distinct = []

allItems.forEach((item) => {
    let matchingItem = distinct.find((match) => match.id == item.id && match.name == item.name)

    if(!matchingItem){
        distinct.push(item)
    }
})

在实践中：

let data = [{
    id: 1,
    name: "test1",
    years: [{
      id: 1,
      name: "year1"
    }, {
      id: 2,
      name: "year2"
    }]
  },
  {
    id: 2,
    name: "test2",
    years: [{
      id: 1,
      name: "year1"
    }]
  },
]

let allItems = data.flatMap((item) => {
  return item.years.map((year) => {
    return year
  })
})

let distinct = []

allItems.forEach((item) => {
  let matchingItem = distinct.find((match) => match.id == item.id && match.name == item.name)

  if (!matchingItem) {
    distinct.push(item)
  }
})

console.log(distinct)

返回对象数组（来自对象数组）

2 个答案: