Create enum

createEnum.js

function createEnum(arr) {
  const obj = arr.reduce((accum, item, index) => {
    index = index.toString();
    accum[index] = item;
    accum[item] = index;
    return accum;
  }, {});

  Object.defineProperties(obj, {
    names: {
      configurable: false,
      enumerable: false,
      get: () => () => arr,
      set: undefined
    },
    numericals: {
      configurable: false,
      enumerable: false,
      get: () => () => arr.map((_, i) => i),
      set: undefined
    }
  });

  Object.freeze(obj);

  return obj;
}