title: Correct way to define an empty dom element in React
body: <p>I send an optional parameter <code>checkbox</code> inside a prop to a component:</p>
  
  <pre><code>var checkBox = this.props.checkbox ? &lt;span className='checkbox'&gt;&lt;/span&gt; : null;
  </code></pre>
  
  <p>Then I put it like this:</p>
  
  <pre><code>&lt;div&gt;
      ...
      {checkBox}
      ...
  &lt;/div&gt;
  </code></pre>
  
  <p>As seen from above, I assign null to the variable. But I can instead assign empty string <code>''</code> which seems to give the same result.</p>
  
  <p>What's the proper one?</p>