title: how to re-render the part of the react component that depends on the Map in its State
body: <pre><code>class App extends Component {
  
  this.state = {      
    myMap: new Map()
  };
  </code></pre>
  <p>when updating the Map...</p>
  <pre><code>{this.state.myMap.forEach((value, key, map) =&gt;  {   
              console.log(key) 
              return &lt;tr&gt;
                &lt;span&gt;{key}&lt;/span&gt;
  </code></pre>
  <p><code>console.log(key)</code>     logging ok
  <code>&lt;span&gt;{key}&lt;/span&gt;</code>  //not rendering</p>