title: Selecting second children of first div children in javascript
body: <p>I have an html that look something like this:</p>
  
  <pre><code>&lt;div id="mainDiv"&gt; &lt;-- I have this
      &lt;div&gt;
          &lt;div&gt;&lt;/div&gt;
          &lt;div&gt;&lt;/div&gt; &lt;-- I need to get this
      &lt;/div&gt;
      &lt;span&gt;&lt;/span&gt;
      &lt;more stuff /&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>i am using:</p>
  
  <pre><code>var mainDiv = document.getElementById('mainDiv');
  </code></pre>
  
  <p>because I need that div in a var, but i also need to get that second div on the first div inside mainDiv into a variable. </p>
  
  <p>How could I do it in a simple cross-browser way?</p>