在对象数组中连接数组

Question

我构建了这个数组：

const array = [
  {
    title: 'something',
    list: ['a', 'b', 'c', 'd']
  },
  {
    title: 'dog',
    list: ['aa']
  },
  {
    title: 'cat',
    list: ['aaa', 'b', 'cccc']
  },
  {
    title: 'apple',
    list: [],
  }
]

我想要一个包含其他数组中所有值的数组，所以：

const res = ['a', 'b', 'c', 'd', 'aa', 'aaa', 'b', 'cccc']

我可以吗？我可以使用 concat 但如何使用？

Answer 1

同时使用 concat 和 reduce

var a=[
  {
    title: 'something',
    list: ['a', 'b', 'c', 'd']
  },
  {
    title: 'dog',
    list: ['aa']
  },
  {
    title: 'cat',
    list: ['aaa', 'b', 'cccc']
  },
  {
    title: 'apple',
    list: [],
  }
];
console.log(a.reduce((acc,e)=>acc.concat(e.list),[]))

Answer 2

您可以减少数组以展平属性。

const
    array = [{ title: 'something', list: ['a', 'b', 'c', 'd'] }, { title: 'dog', list: ['aa'] }, { title: 'cat', list: ['aaa', 'b', 'cccc'] }, { title: 'apple', list: [] }],
    list = array.reduce((r, { list }) => [...r, ...list], []);

console.log(list);

或即将到来的 flatMap。

const
    array = [{ title: 'something', list: ['a', 'b', 'c', 'd'] }, { title: 'dog', list: ['aa'] }, { title: 'cat', list: ['aaa', 'b', 'cccc'] }, { title: 'apple', list: [] }],
    list = array.flatMap(({ list }) => list);

console.log(list);

Answer 3

使用 reduce 和 ...（展开运算符）非常简单。

const array = [{
    title: 'something',
    list: ['a', 'b', 'c', 'd']
  },
  {
    title: 'dog',
    list: ['aa']
  },
  {
    title: 'cat',
    list: ['aaa', 'b', 'cccc']
  },
  {
    title: 'apple',
    list: [],
  }
]

const result = array.reduce((accum, item) => {
  return [...accum, ...item.list]
}, [])

console.log(result);

Answer 4

您可以在具有 map 的空数组上使用 concat 并扩展语法 ....

const array = [{"title":"something","list":["a","b","c","d"]},{"title":"dog","list":["aa"]},{"title":"cat","list":["aaa","b","cccc"]},{"title":"apple","list":[]}]

const res = [].concat(...array.map(({list}) => list))
console.log(res)

Answer 5

忘记 flatmap 和 reduce。让事情简单易懂。

var res = []
for (var i = 0; i < array.length; i++) {
    res = res.concat(array[i]["list"])
}

在对象数组中连接数组

Concat arrays in array of objects

javascript

arrays

concat

object