const a1 = new List(['a', 'b', 'c']);
const a2 = new List(['x', 'y', 'z']);

const combinedArray = combineArrays(a1,a2);
=> combinedArray: ['a-x', 'a-y', 'a-z', 'b-x', 'b-y', 'b-z', 'c-x', 'c-y', 'c-z']

import { List } from 'immutable';

const combineArray = (arrayA = new List([]), arrayB = new List([])) => {
  if (arrayA.count() === 0) {
  return arrayB;
}

if (arrayB.count() === 0) {
  return arrayA;
}

let combinations = new List([]);

combinations = arrayA.reduce((accum, value) => {
  if (value) {
    return accum.push(arrayB.reduce((accum2, value2) => {
      if (value2) {
        return accum2.push(`${value}-${value2}`);
      }
      return value;
    }, new List([])));
  }

  return accum;
}, new List([]));

  return combinations.flatten(true);
};

export default combineArray;

import { List } from 'immutable';

const combineArray = (arrayA = new List([]), arrayB = new List([])) => {
  if (arrayA.isEmpty()) { return arrayB; }
  if (arrayB.isEmpty()) { return arrayA; }

  return arrayA.flatMap(valueA => (
    arrayB.map(valueB => (
      `${valueA}-${valueB}`
    ))
  ));
};

export default combineArray;