title: redux-persist - When to persist reducer?
body: <p>The <a href="https://github.com/rt2zz/redux-persist" rel="nofollow noreferrer">redux-persist</a> library provides ways to store redux state tree into some sorts of storage, and rehydrate when app is re-opened.</p>
  
  <p>I see the need of restoring the state tree because it contains useful data, but the library also includes a feature for <strong>persisting reducers</strong>.</p>
  
  <pre><code>const persistedReducer = persistReducer(persistConfig, rootReducer)
  </code></pre>
  
  <p>I cannot quite understand the motivation behind since I believe reducers are just functions to mutate the state. Those are well-defined in the code, compared to dynamic data in state tree.</p>
  
  <p><strong>When should we persist reducer? Any example showing why it is helpful?</strong></p>