redux-simple.js

const initialState = {
  count: 0,
  counting: false
}

// Actions
export function reset() {
  return { type: 'COUNTER_RESET' }
}

export function increment(n) {
  return { type: 'COUNTER_INCREMENT', n }
}

// Reducer
export default function counterReducer(state = initialState, action) {
  switch (action.type) {
    case 'COUNTER_RESET':
      return { ...state, count: 0 }
    case 'COUNTER_INCREMENT':
      return { ...state, count: state.count + action.n }
    default:
      return state
  }
}