// create-index.tsx
import { Action } from 'redux';

type Handlers<State, Types extends string, Actions extends Action<Types>> = {
  readonly [Type in Types]: (state: State, action: Actions) => State;
};

export const createReducer = (initialState, handlers) => (state = initialState, action) =>
  handlers.hasOwnProperty(action.type) ? handlers[action.type](state, action) : state;