title: react-redux: What is the difference between state.setIn() and state.set()?
body: <p>I've seen the use of <code>setIn()</code> and <code>set()</code> in some react-redux code:</p>
  <pre><code>state.setIn(...);
  state.set(...);
  </code></pre>
  <p>I've found some documentation here <a href="https://facebook.github.io/immutable-js/" rel="nofollow noreferrer">https://facebook.github.io/immutable-js/</a>
  But unfortunately the method is not documented in detail.</p>
  <p>I also found some other questions: <a href="https://stackoverflow.com/questions/27286134/using-reacts-immutable-helper-with-immutable-js">Using React&#39;s immutable helper with Immutable.js</a>
  But these do not answer my question.</p>
  <p>I understand, that it must do some immutable stuff?
  But what's the immutable thing here?
  And what's the difference between <code>set()</code> and <code>setIn()</code>?
  Why do we need immutable?</p>