mergeInitialState.js

const merge = (initialValue, hydratedValue) => {
  if (!isObjectLike(initialValue)) {
    return initialValue;
  }
  return {...hydratedValue, ...initialValue};
};

const useStorage = (state, setState, initialValue) => {
  const [rehydrated, setRehydrated] = useState(false);
  const [error, setError] = useState(null);

  useEffect(() => {
    localforage.getItem(config.key, (err, value) => {
      if (err) {
        setRehydrated(true);
        return setError(err);
      }
      // Merge initialValue with persist value
      let mergedValue = rehydrated(value);
      if (initialValue) {
        mergedValue = merge(initialValue, mergedValue);
      }
      setState(mergedValue);
      setRehydrated(true);
    });
  }, []);

  useEffect(() => {
    if (isNil(state) || isEmpty(state)) {
      localforage.removeItem(config.key);
    }
    localforage.setItem(config.key, hydrate(state));
  }, [state]);
  
  return {
    rehydrated,
    error,
  };
};