ools (<code>Cmd</code> + <code>Shift</code> + <code>I</code>)
  and run <code>document.querySelector("#my-widget")</code>. If the element
  is found, the widget is functioning correctly. If <code>undefined</code> is
  returned, double-check that the <a href="#root/_help_BFs8mudNFgCS">note</a> has
  the <code>#widget</code>  <a href="#root/_help_zEY4DaJG4YT5">attribute</a>.</p>
<h3>Step 2: Adding an UI Element</h3>
<p>Next, let's improve the widget by adding a button to it.</p><pre><code class="language-text