Angular2 Router Loading Screen

app.component.ts

export class AppComponent {
  routerLoading$: Observable<boolean>;
  constructor(private router: Router) {
    this.routerLoading$ = this.router.events.flatMap(event => {
      if (event instanceof NavigationStart) {
        return [true];
      }
      if (event instanceof NavigationEnd ||
        event instanceof NavigationCancel ||
        event instanceof NavigationError) {
        return [false];
      }

      return Observable.never();
    });
  }
}

// HTML
<div>
  <div class="router-loading-indicator" *ngIf="routerLoading$ | async">
    <spinner></spinner>
  </div>
  <router-outlet></router-outlet>
</div>