title: Angular2, HostListener, how can I target an element? can I target based on class?
body: <p>In Angular2, how can I target an element within the HostListener decorator?</p>
  
  <pre><code>@HostListener('dragstart', ['$event'])
      onDragStart(ev:Event) {
          console.log(ev);
      }
  
  @HostListener('document: dragstart', ['$event'])
      onDragStart(ev:Event) {
          console.log(ev);
      }
  
  @HostListener('myElement: dragstart', ['$event'])
      onDragStart(ev:Event) {
          console.log(ev);
      }
  
  @HostListener('myElement.myClass: dragstart', ['$event'])
      onDragStart(ev:Event) {
          console.log(ev);
      }
  </code></pre>
  
  <p>The two first work. Any other thing I've tried raises an <code>EXCEPTION: Unsupported event target undefined for event dragstart</code></p>
  
  <p>So, can I implement it to a targeted element? How?</p>