Lighthouse/src/Store/Reducers/user.js

import { handleActions } from 'redux-actions'
import { LOGIN, LOGOUT, CHANGE_PIC } from '../Actions'

const user = handleActions({
  [LOGIN]: (state, action) => action.payload,
  [LOGOUT]: (state, action) => null,
  [CHANGE_PIC]: (state, action) => ({ ...state, photoURL: action.payload })
}, null);

export default user;