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post.js

const INITIAL_STATE = {
     token: null,
     userId: null,
     error: null,
     loading: false,
 };
 
// ... 
 
 const reducer = (state = INITIAL_STATE, action) => {
     switch(action.type) {
         case actionTypes.AUTH_START: 
             return {...state, ...{ loading: true, error: null }};
         case actionTypes.AUTH_SUCCESS:
             return {...state, token: action.token, userId: action.userId, loading: false };
         case actionTypes.AUTH_FAIL:
             return {...state,  loading: false, error: action.error };
         case actionTypes.AUTH_LOGOUT:
             return {...state, token: null, userId: null };
         default: return state;
     }
 };
 
 export default reducer;