createEnum.js

/* @flow */

import { Record } from 'immutable';

interface $EnumInterface<T: Object> extends Record<T> {
  items: Function;
  fromValue: Function;
}

const createEnum = <T: Object>(items: T): $EnumInterface<T> => {
  class Enum extends Record(items) {
    // `this` here is an instance of Record so all instance methods are available!
    items = () => this.toArray();
    fromValue = value => this.find(item => item.value === value);
  }

  return new Enum();
};

export default createEnum;