A function that finds all combinations of numbers in an array the sum of which equals a certain number

sumOfCombinations.js

function arraySum(arr) {
  return arr.reduce((sum, next) => sum + next, 0);
}

function padLeft(string, size) {
  let res = string;
  while (res.length < size) {
    res = `0${res}`;
  }
  return res;
}

function turnIntoIndexes(binaryString) {
  return binaryString
    .split('')
    .map((n, index) => (n === '1' ? index : null))
    .filter(Number.isInteger);
}

function getAllCombinations(arr) {
  const combinations = [];
  const max = 2 ** arr.length;
  let n = 0;

  while (++n < max) {
    const binaryString = n.toString(2);
    const visualPosition = padLeft(binaryString, arr.length);
    const indexes = turnIntoIndexes(visualPosition);
    const combination = indexes.map(i => arr[i]);
    combinations.push(combination);
  }

  return combinations;
}

function sumOfCombinations(values, desiredSum = 10) {
  const combinations = getAllCombinations(values);
  return combinations.filter(
    combination => arraySum(combination) === desiredSum,
  );
}

module.exports = {
  arraySum,
  sumOfCombinations,
};

sumOfCombinations.test.js

const assert = require('assert');
const { arraySum, sumOfCombinations } = require('./sumOfCombinations');

/** test arraySum */
assert.equal(arraySum([1, 2, 3]), 6, '1 + 2 + 3 equals 6');
assert.equal(arraySum([97, 1, 1, 1]), 100, '97 + 1 + 1 + 1 equals 100');

/** test sumOfCombinations */
const sum = 10;
const res1 = sumOfCombinations([1, 2, 3, 4, 5], sum);
assert.equal(res1.length, 3, "should've found 3 combinations");
assert.ok(
  res1.every(combination => arraySum(combination) === sum),
  'Sum of every combination should be correct',
);

const res2 = sumOfCombinations([1, 2, 3, 4, 5, 13, 45, 9, 7, 8], sum);
assert.equal(res2.length, 7, "should've found 7 combinations");
assert.ok(
  res2.every(combination => arraySum(combination) === sum),
  'Sum of every combination should be correct',
);

const res3 = sumOfCombinations([1, 1, 1, 1, 1, 1, 1, 1, 1, 1], sum);
assert.equal(res3.length, 1, "should've found 1 combination");
assert.ok(
  res3.every(combination => arraySum(combination) === sum),
  'Sum of every combination should be correct',
);

const res4 = sumOfCombinations([54, 234, 12, 99, 10], sum);
assert.equal(res4.length, 1, "should've found 1 combination");
assert.ok(
  res4.every(combination => arraySum(combination) === sum),
  'Sum of every combination should be correct',
);

console.log('all tests passed');