packages/redux-saga/examples/real-world/reducers/index.js
function errorMessage(state = null, action) {
  const { type, error } = action

  if (type === ActionTypes.RESET_ERROR_MESSAGE) {
    return null
  } else if (error) {
    return action.error
  }

  return state
}
function errorMessage(state = null, action) {
  const { type, error } = action

  if (type === ActionTypes.RESET_ERROR_MESSAGE) {
    return null
  } else if (error) {
    return action.error
  }

  return state
}
Updates error message to notify about the failed fetches.