title: Why isn't the key property recognised as part of the Event type in typescript
body: <p>I have a function which finds out what button a user pressed using events, and uses the event.key property. However, in the parameter of the function, if i assign it a type Event, the compiler complains that </p>
  
  <blockquote>
    <p>Property 'key' does not exist on type 'Event'.</p>
  </blockquote>
  
  <p>Here is my code.</p>
  
  <pre><code>function getDirection(e:Event):void{
      let directionCode:number = e.key; 
      // code going on here
  }
  </code></pre>
  
  <p>Why isnt the key property recognised on type event. </p>