title: "scroll" event listener not triggering
body: <p>I'm currently working on a vanilla JS plugin, and I need to update a value on scroll, so I attached an event listener to the document to trigger a function that should update the aforementioned value.</p>
  
  <p>Thing is, it works on document load but not on scroll. It's as if the scroll event isn't working at all.</p>
  
  <p>Currently, my JS part looks something like this:</p>
  
  <pre><code>var currentPosition = 0;
  
  var updatePosition = function() {
    currentPosition = document.body.scrollTop;
    document.getElementById('indicator').textContent = currentPosition;
  };
  
  document.addEventListener('scroll', updatePosition());
  </code></pre>
  
  <p>Here's a fiddle to make it a bit more clear: <strong><a href="http://jsfiddle.net/1vqjanLm/1/" rel="nofollow">JSFIDDLE</a></strong></p>
  
  <p>I tried attaching the event listener on both the body and the window, it makes no difference whatsoever.</p>