store.js

import { createStore } from 'redux'

const eevee = { especie: 'Eevee', level: 1 };

const eeveelution = (state = eevee, action) => {
  switch (action.type){
    case 'WATER_STONE':
      return { ...state, specie: 'Vaporeon' };
    case 'THUNDER_STONE':
      return { ...state, specie: 'Jolteon' };
    case 'FIRE_STONE':
      return { ...state, specie: 'Flareon' };
    case 'LEVEL_UP':
      return { ...state, level: state.level + 1};
    default:
      return state;
  }
}

const store = createStore(eeveelution);

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

console.log(store);

store.dispatch({ type: 'WATER_STONE' });
store.dispatch({ type: 'LEVEL_UP' });
store.dispatch({ type: 'THUNDER_STONE' });
store.dispatch({ type: 'WATER_STONE' });

console.log(eevee);