adding google analytics to angular

1 ...
2import{Router, NavigationEnd} from '@angular/router';
3...
4declare let gtag: Function;
5...
6export class AppComponent {
7  constructor(public router: Router){   
8      this.router.events.subscribe(event => {
9         if(event instanceof NavigationEnd){
10             gtag('config', 'xx-xxxxx-xx', 
11                   {
12                     'page_path': event.urlAfterRedirects
13                   }
14                  );
15          }
16       }
17    )}
18}