enumMap flow util

enumMap.js

export type EnumNames = 'A' | 'B' | 'C';

export type EnumMap<K: string, V, O: Object = *> = O & {
  [K]: V & $ElementType<O, K>,
};

export type SpecificMap = EnumMap<EnumNames, any>;
const cbNames: EnumMap<EnumNames, (any) => void> = {
  A: v => v,
  B: v => v.prop,
  C: () => {},
};