title: React: adding props to an existing component
body: <p>I'm trying to figure out how to clone an existing element with additional props.</p>
  
  <p>For reference:</p>
  
  <pre><code>this.mainContent = &lt;Hello message="Hello world!" /&gt;
  </code></pre>
  
  <p>I attempted to do something like</p>
  
  <pre><code>React.createElement(this.mainContent, Object.assign({}, 
     this.mainContent.props, { anotherMessage: "nice to meet ya!" }));
  </code></pre>
  
  <p>but it's not working. </p>
  
  <p>How would I accomplish this?</p>