Rearrange object structure

rearrange.js

import _ from 'lodash';


const isPlainObject = value =>
  value === Object(value) &&
  !Array.isArray(value);

function* leaves(node, path = []) {
  if (!isPlainObject(node)) {
    return yield {value: node, path};
  }

  for (const [key, childNode] of Object.entries(node)) {
    yield* leaves(childNode, [...path, key]);
  }
}

const applyPermutation = (arr, perm) => arr.map((_, idx) => arr[perm[idx]]);

function rearrange(node, permutation) {
  const output = {};

  for (const {path, value} of leaves(node)) {
    _.set(output, applyPermutation(path, permutation), value);
  }

  return output;
}


export {rearrange};

Usage:

const grades = {bob: {math: 10, french: 20,}, alice: {math: 14, french: 15,}}
rearrange(grades, [1, 0]); // => { math: { bob: 10, alice: 14 }, french: { bob: 20, alice: 15 } }