title: Javascript event custom property disappears
body: <p>I have an iFrame inside my document, which at one point triggers a custom event:</p>
  
  <pre><code>function notifyEnd(gameStatus) {
      var fireOnThis = parent.document;
      var evObj = document.createEvent('Event');
      evObj.gameStatus = gameStatus;
      evObj.initEvent('gameEnd', true, true);
      fireOnThis.dispatchEvent(evObj);
  }
  </code></pre>
  
  <p>Please note the gameStatus property set on the event.</p>
  
  <p>My document registers an event listener for this event:</p>
  
  <pre><code>document.addEventListener('gameEnd', function(e) {
      document.getElementById("gameEndForm:gameStatus").value = e.gameStatus;
      document.getElementById("gameEndForm:gameCompleteButton").click();
  }, true);
  </code></pre>
  
  <p>However, when the event is fired, the "gameStatus" property has an "undefined" value. I couldn't find any clue as to what could cause such a behaviour.</p>
  
  <p>Thanks for your help,<br>
  Sébastien</p>