title: How to have conditional elements and keep DRY with Facebook React's JSX?
body: <p>How do I optionally include an element in JSX?  Here is an example using a banner that should be in the component if it has been passed in.  What I want to avoid is having to duplicate HTML tags in the if statement.</p>
  
  <pre><code>render: function () {
      var banner;
      if (this.state.banner) {
          banner = &lt;div id="banner"&gt;{this.state.banner}&lt;/div&gt;;
      } else {
          banner = ?????
      }
      return (
          &lt;div id="page"&gt;
              {banner}
              &lt;div id="other-content"&gt;
                  blah blah blah...
              &lt;/div&gt;
          &lt;/div&gt;
      );
  }
  </code></pre>