Redux reducer using object literal instead of a switch statement

reduxObjectLiteral.js

import {createStore} from 'redux';

const counter = (state = 0, action) => {
  const index = {
    'INCREMENT': () => {
        return state+1;
    },
    'DECREMENT': () => {
        return state-1;
    },
    'DEFAULT': () => {
        return state;
    }
  };
  return (index[action.type] || index['DEFAULT'])();
}

const store = createStore(counter);

store.subscribe( () => { console.log(store.getState()); } );

store.dispatch({ type: 'INCREMENT' });
store.dispatch({ type: 'DECREMENT' });