В example.component.ts
import { Observable } from 'rxjs';
В example.component.html
Observable.interval(2000).map(valor => 'Async value');
В example.component.ts
import { Observable, interval, pipe } from 'rxjs';
import {switchMap, map} from 'rxjs/operators';
В example.component.html
valorAsync = interval(2500).pipe(map(valor => 'Async value'));