如何使用单行解决方案将包含对象数组数组的对象减少为内部对象？

Question

我有以下对象结构：

regions: [
  {
    name: reg1, 
    subregions: [
      {name: subreg11},
      {name: subreg12}
    ]
  },
  {
    name: reg2, 
    subregions: [
      {name: subreg21},
      {name: subreg22}
    ]
  }
]

我想要的是提取子区域数组，如下所示：

[{name: subreg11}, {name: subreg12}, {name: subreg21}, {name: subreg22}]

...我想用一行 array.prototype 函数来做到这一点，例如 .filter、.map、.forEach 等

我已经设法用这样的三行来完成（包括 return 语句，我想在一行中包含它）：

let subregions = []
regions.forEach(reg => reg.subregions.forEach(subregion => subregions.push(subregion)))
return locs

有人知道我该怎么做吗？

编辑 2020 年 7 月：我看到问题已被 @nina-sholz, but I don't believe this is true. The linked question asks "" 标记为重复，而我的问题是对解决问题的方法的描述. 我没有特别请求 flatMap 函数，将其标记为重复只是说“你应该凭直觉知道 Array.prototype.flatMap 是你要找的东西”。

Answer 1

flatMap 并提取 subregions 属性:

const regions = [
  {
    name: 'reg1',
    subregions: [
      {name: 'subreg11'},
      {name: 'subreg12'}
    ]
  },
  {
    name: 'reg2', 
    subregions: [
      {name: 'subreg21'},
      {name: 'subreg22'}
    ]
  }
];

const output = regions.flatMap(({ subregions }) => subregions);
console.log(output);

您也可以使用 reduce:

const regions = [
  {
    name: 'reg1',
    subregions: [
      {name: 'subreg11'},
      {name: 'subreg12'}
    ]
  },
  {
    name: 'reg2', 
    subregions: [
      {name: 'subreg21'},
      {name: 'subreg22'}
    ]
  }
];

const output = regions.reduce((a, { subregions }) => a.concat(subregions), []);
console.log(output);

几乎任何 Javascript 代码都可以简化为一行，但不一定可读。

Answer 2

您可以使用 map 和 flat

const regions = [{name: 'reg1',subregions: [{name: 'subreg11'},{name: 'subreg12'}]},{name: 'reg2', subregions: [{name: 'subreg21'},{name: 'subreg22'}]}];
const output = regions.map(({ subregions }) => subregions).flat();
console.log(output);

如何使用单行解决方案将包含对象数组数组的对象减少为内部对象？

How to, with a one-lined solution, can I reduce an object containing arrays of arrays of objects to the inner objects?

javascript

arrays

javascript-objects

sub-array