title: Avoid Adding Event Multiple Times
body: <p>I am dynamically adding events using <code>addEvent("keydown", function() {});</code> to an element. My problem is that there are times when this code get's run on the same element twice or more. The behavior becomes clunky as the function registered for that event runs a couple of times.</p>
  
  <p>Is there a way for me to only run the code above only once on an element? Maybe check if the event has already been added before?</p>