Configuring preloaded state to save after each action on the store

savePreloadedStateMiddleware.js

import { applyMiddleware, createStore } from "redux";
import thunk from "redux-thunk";

import reducer from "./api";

function savePreloadedState({ getState }) {
  return next => action => {
    const returnValue = next(action);
    // just point the __PRELOADED_STATE__ at the state after this action.
    window.__PRELOADED_STATE__ = getState();

    // we're not modifying the state, just spying on it.
    return returnValue;
  };
}

const store = createStore(
  reducer,
  applyMiddleware(thunk, savePreloadedState)
);