text: import { INCREMENT_COUNTER, DECREMENT_COUNTER } from '../constants/ActionTypes';
  
  export default function counter(state = 0, action = {}) {
      switch (action.type) {
          case INCREMENT_COUNTER:
              return state + 1;
          case DECREMENT_COUNTER:
              return state - 1;
          default:
              return state;
      }
  }