A simpler Redux boilerplate

store.js

import { combineReducers, createStore } from "redux";
import Type from "union-type";

// MESSAGES

const Msg = Type({ INCREMENT: [], DECREMENT: [], DEFAULT: [] });

// UPDATE

const nextState = Msg.caseOn({
  INCREMENT: state => state + 1,
  DECREMENT: state => state - 1,
  DEFAULT: state => state,
  _: state => state
});

function counter(state = 0, { type = Msg.DEFAULT, payload = null }) {
  if (typeof type === "string") return state;
  return nextState(type, state);
}

// STORE

const store = createStore(
  combineReducers({
    counter
  }),
  window.__REDUX_DEVTOOLS_EXTENSION__ && window.__REDUX_DEVTOOLS_EXTENSION__()
);

// EXPORTS - ACTIONS & STORE

export const add = () => store.dispatch({ type: Msg.INCREMENT });
export const subtract = () => store.dispatch({ type: Msg.DECREMENT });
export default store;