Persist redux state to local storage

index.js

import { store } from './fileWhereStoreLives';

// add this code in your app's entry point file to
// set localStorage when navigating away from app
window.onbeforeunload = function(e) {
  const state = store.getState();
  localStorage.setItem(
    'local-storage-key',
    JSON.stringify(state.stateYouWantToPersist)
  );
};

reducer.js

import { importedState } from './fileWhereStateLives';

// define your reducer's initial state:
const initialState = {
  ...importedState;
};

// define default state for each subsequent visit. 
// if localStorage with this key exists, assign it 
// to this variable, otherwise, use initialState.
const defaultState = JSON.parse(
  localStorage.getItem('local-storage-key')
) || initialState;

// set defaultState of reducer to result of above operation
const reducer = (state = defaultState, action) => {
  switch (action.type) {
    case 'DO_SOMETHING_COOL':
      return {
        ...state,
        ...action.newState
      };
    default:
      return state;
  }
}

export default reducer;