redux action without switch

counter.js

import * as types from '../actions/actionTypes';

const initialState = {
  count: 0
};

export default counter = (state = initialState, action = {}) => {
  return {
      [types.INCREMENT]: {
        ...state,
        count: state.count + 1
      },
      [types.DECREMENT]: {
        ...state,
        count: state.count - 1
      }
    }[action.type] || state;
}