ng-router-state#read-from-history.ts

@Component({
  selector: 'app-details-page',
  template: '<pre>{{ state$ | async | json }}</pre>'
})
export class DetailsPageComponent implements OnInit {
  state$: Observable<object>;
  
  constructor(public activatedRoute: ActivatedRoute) {}
  
  ngOnInit() {
    this.state$ = this.activatedRoute.paramMap
      .pipe(map(() => window.history.state))
  }
}