Sorting multiple arrays in Javascript

sortArrays.js

/**
 *  Sorts all arrays together with the first. Pass either a list of arrays, or a map. Any key is accepted.
 *     Array|Object arrays               [sortableArray, ...otherArrays]; {sortableArray: [], secondaryArray: [], ...}
 *     Function comparator(?,?) -> int   optional compareFunction, compatible with Array.sort(compareFunction) 
 */
function sortArrays(arrays, comparator = (a, b) => (a < b) ? -1 : (a > b) ? 1 : 0) {
  let arrayKeys = Object.keys(arrays);
  let sortableArray = Object.values(arrays)[0];
  let indexes = Object.keys(sortableArray);
  let sortedIndexes = indexes.sort((a, b) => comparator(sortableArray[a], sortableArray[b]));

  let sortByIndexes = (array, sortedIndexes) => sortedIndexes.map(sortedIndex => array[sortedIndex]);

  if (Array.isArray(arrays)) {
    return arrayKeys.map(arrayIndex => sortByIndexes(arrays[arrayIndex], sortedIndexes));
  } else {
    let sortedArrays = {};
    arrayKeys.forEach((arrayKey) => {
      sortedArrays[arrayKey] = sortByIndexes(arrays[arrayKey], sortedIndexes);
    });
    return sortedArrays;
  }
}

sortArraysExample.js

let people = ["john", "benny", "sally", "george"];
let peopleIds = [10, 20, 30, 40];

sortArrays([people, peopleIds]);
[["benny", "george", "john", "sally"], [20, 40, 10, 30]] // output

sortArrays({people, peopleIds});
{"people": ["benny", "george", "john", "sally"], "peopleIds": [20, 40, 10, 30]} // output

function sortArrays is a bad name .. how about parallelSort?

default comparator is simply (a, b) => (b - a) for ascending order
sort only looks for the sign (plus or minus), no need for +1 or -1

typeof arrays should be array, so sortableArray is always arrays[0]
dont rely on ordered map values .. when accepting objects-of-arrays, require the object-key to get sortableArray

let sortedIndexes = indexes.sort( .. sort mutates in-place AND returns, so sortedIndexes == indexes

.map( is slower than for (let i = 0; ....) { .. especially in the hot-code function sortByIndexes

variable names are too similar, only adding s is hard to read, add List for example

.. other than that, good job : )

Thank you for taking the time to find and report everything wrong with this piece code.
I hope it gave you some relief.

I hope it gave you some relief.

the best therapy! even better than publishing a better version : P

😂

This is awesome. thanks.