title: addEventListener DOMContentLoaded not working
body: <p>I'm trying to create a simple script that will add a listener to a button to trigger a function that displays an alert when the page is fully loaded.</p>
  
  <p>The script is to be implemented in a Chrome Extension</p>
  
  <p>I'm using the following code:</p>
  
  <pre><code>    document.addEventListener('DOMContentLoaded', function () {
          showalert();
          document.querySelector('button').addEventListener('click', showalert());
      });
  
      function showalert() {
          alert("you just pressed the button");
      }
  </code></pre>
  
  <p>And my HTML</p>
  
  <pre><code>    &lt;button id="button"&gt;button&lt;/button&gt;
  </code></pre>
  
  <p>The listener is never added to the button, also the first showalert(); is not fired.</p>
  
  <p>I'm probably being stupid here, but I'm failing to see why this is not working. Any help would be greatly appreciated! </p>
  
  <p>JSfiddle: <a href="http://jsfiddle.net/bunker1/fcrwt/1/" rel="noreferrer">http://jsfiddle.net/bunker1/fcrwt/1/</a></p>