Using SwitchMap to review an observable and then poll for another via a async call

wordpress-switchMap-to-convert-async-call.ts

@Component({
    template: `
      <input [formControl]="petControl"/>
      <span *ngIf="isPetExists">Pet already exists!</span>
    `
})
export class PetComponent implements OnInit {
    petControl = new FormControl('');
    isPetExists = false;
    constructor(private service: Service) {}
    ngOnInit() {
        this.petControl.valueChanges
          .pipe(debounceTime(500), 
                switchMap((value: string) => {
                return this.service.isPetExists(value);
            }).subscribe((isPetExists: boolean) => {
                this.isPetExists = isPetExists;
            });
        }
    }
}