middleware.ts

export const actionToPlainObjectMiddleware = store => next => action => {
  if (typeof action === 'object' && action.type) {
    const toForward = { ...action };
    return next(toForward);
  } else if (typeof action === 'function') {
    let toForward = action();
    toForward = { ...toForward };
    return next(toForward);
  } else {
    throw new Error('Action must be FSA');
  }
};

// Just as an FYI, This is how I am dispatching the first action
store.dispatch(new windowActions.LoadWindowStateFromStorage());

// And this is how my store is setup
const epicsMiddleware = createEpicMiddleware(windowEpics);

export const store = createStore(
  windowStateReducer,
  applyMiddleware(actionToPlainObjectMiddleware, epicsMiddleware),
);
replayActionMain(store);