title: how to merge nested maps in immutable.js
body: <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="true">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>import {Map} from 'immutable'
  
  let map1 = Map({a:1,b:{c:2,d:3,e:1});
  let map2 = Map({c:100,d:400});</code></pre>
  </div>
  </div>
  </p>
  
  <p>how do I get <code>Map {a:1,b:{c:100,d:400,e:1}}</code> by merging map1 and map2?</p>