title: What are the differences between firstChild and [0]?
body: <p>Do they serve the same purpose? If so, is <code>firstChild</code> better than <code>[0]</code>?</p>
  
  <pre><code>document.getElementsByTagName('div')[0]
  // versus
  document.getElementsByTagName('div').firstChild
  </code></pre>
  
  <p>Could it possibly be that <code>[0]</code> is more consuming?</p>