angular 4 directive that emit an event when click event happen outside of target

click-outside.directive.ts

import {Directive, ElementRef, Output, EventEmitter, HostListener} from '@angular/core';

@Directive({
  selector: '[appClickOutside]'
})
export class ClickOutsideDirective {
  constructor(private _elementRef: ElementRef) {
  }

  @Output()
  public clickOutside = new EventEmitter();

  @HostListener('document:click' , ['$event.target']) onClick( target) {
    const clickedInside = this._elementRef.nativeElement.contains(target);
    if (!clickedInside) {
      this.clickOutside.emit(null);
    }
  }
}