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// message is constructed using helper functions
const HelperFunction = ({count}) =>
  <Trans>
    {plural(count, {
      one: "One glass",
      other: "# glasses"
    })} or wine
  </Trans>
  
// message written using template literals

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const mapStateToProps = (state) => ({
  todos: allTodos(state)  // instead of state.todos
})

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const initialState = {
  todos: []
}

const reducer = (state = initialState, action = {}) => {
  if (action.type === 'ADD_TODO') {
      return {
        ...state,
        todos: [...state.todos, action.payload]
      }

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const initialState = {
  user: null
}

const getUser = state => state.user
const isAuthenticated = state => Boolean(getUser(state))

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const initialState = {
  user: {
    name: 'anonymous',
    token: null
  }
}

const getUser = state => state.user || {}
const isAuthenticated = state => Boolean(getUser(state).token)
const isAnonymous = state => !isAuthenticated(user)

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// const reducer = ...

const ID = 'auth'
const local = state => state[ID]

const getUser = state => local(state).user
const isAuthenticated = state => Boolean(getUser(state))

export default {[ID]: reducer}

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module Y2017.M06.D07.Exercise where

{--
So, here's one of the questions Amazon asks developers to test their under-
standing of data structures.

You have a binary tree of the following structure:

        A
       / \

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export const fetchSaga = (entity, api) => function* ({ payload }) {
  try {
    const data = yield call(api, payload)
    yield put(entity.response(data))
  }
  catch(error) {
    yield put(entity.response(error))
  }
}

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function ApiGetUser({ id }) {
  return fetch(url`/user/${id}`)
}

// Just an example. Action creators are usually 
// created using `createAction` from `redux-actions`
const getUser = {
  request: (id) => ({ 
    type: 'USER_GET@REQUEST', 
    payload: { id } 

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export function* checkConnection () {
  let interval = 1

  // eslint-disable-next-line no-constant-condition
  while (true) {
    // race == wait for effect which comes first
    const { timeout, up } = yield race({
      // ping triggered manually
      // e.g: 'reconnect now' button
      ping: take(action.networkPing),