[Angular] HostListener Method Arguments - Blocking Default Keyboard Behavior

We are going to see how to using method arguments for @HostListener.

First, we can use HostListener without method arguments:

    @HostListener(‘dblclick‘)
    toggle(){
        this.collapsed = !this.collapsed;
    }

It works fine. 

But if we need to get the $event object and do something with it, for example using preventDefault() from the event object. Then we need to use method arguments:

  @HostListener(‘keydown‘, [‘$event‘, ‘$event.keyCode‘])
  onKeyDown($event: KeyboardEvent, keyCode) {if(keyCode !== TAB) {
      $event.preventDefault();
    }
  }

Here we inject ‘$event‘ and ‘$event.keyCode‘ into the method arguments. So for onKeyDown() method, we are able to inject those as well.

[Angular] HostListener Method Arguments - Blocking Default Keyboard Behavior

原文：http://www.cnblogs.com/Answer1215/p/7226104.html