转化嵌套对象数组 [英] Transforming nested objects to an array

问题描述

我有一个包含其它的目的，如一个对象

I have an object that contains other objects, such as:

let foo = {
  a: {
    b: {},
    c: {}
  },
  d: {
    e: {}
  }
};

现在我想转换成对象，其中前两个层次的按键形成一个键/值对，如数组这样的：

Now I want to transform this into an array of objects, where the keys of the first two levels form a key / value pair, such as:

let transformedFoo = [
  { outer: 'a', inner: 'b' },
  { outer: 'a', inner: 'c' },
  { outer: 'd', inner: 'e' }
];

我目前的做法是这样的：

My current approach looks like this:

let fooTransformed = [];

Object.keys(foo).forEach(function (outerKey) {
  Object.keys(foo[outerKey]).forEach(function (innerKey) {
    fooTransformed.push({
      outer: outerKey,
      inner: innerKey
    });
  });
});

它的工作原理，但我认为这不是好（即，它不是最好有两个嵌套循环）。是否有关于如何实现这更好的方式（我可以想像，有一个相当考究单纯的功能性解决方案，但我想不出任何）？

It works, but I think it's not "nice" (i.e., it's not nice to have two nested loops). Is there a better way on how to achieve this (I could imagine that there is a quite elegant purely functional solution, but I can't think of any)?

推荐答案

使用地图和减少：

> Object.keys(foo).map(function(key) { 
      return Object.keys(foo[key]).map(function(val) {
          return {outer: key, inner: val} } ) 
      }).reduce(function(a,b) { return a.concat(b) })

[ { outer: 'a', inner: 'b' },
  { outer: 'a', inner: 'c' },
  { outer: 'd', inner: 'e' } ]

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