auth.js

export const getCurrentUser = () => (dispatch, getState) => {
  const { currentUser } = getState().authenticationRequest
  if (currentUser) {
    return dispatch({
      type: 'CURRENT_USER_SUCCESS',
      currentUser
    })
  }

  dispatch({
    type: 'CURRENT_USER_REQUEST'
  })

  return fetchCurrentUser()
    .then(currentUser => {
      dispatch({
        type: 'CURRENT_USER_SUCCESS',
        currentUser
      })
    })
    .catch(err => {
      dispatch({
        type: 'CURRENT_USER_FAILURE',
        err: err
      })
    })
}