test-routing-no-snapshot-example.ts

@Component({
    selector: 'app-dummy-component',
    templateUrl: './dummy-component.component.html',
})
export class DummyComponent implements OnInit {

    constructor(public route: ActivatedRoute) {
    }

    ngOnInit(): void {
        this.route.queryParams
            .pipe(
                map(qs => qs[QueryParamNames.id]),
                distinctUntilChanged(),
                tap(id => {
                    if (id) {
                        // load the item and show the edit form
                    } else {
                        // load the creation form
                    }
                }),
            )
            .subscribe();
    }

}