Repeat request (Angular2 - http.get) n seconds after finished

Question

I played around with angular2 and got stuck after a while.

Using http.get works fine for a single request, but I want to poll live-data every 4 seconds,

Answer 1

Update to RxJS 6

import { timer } from 'rxjs';
import { concatMap, map, expand, catchError } from 'rxjs/operators';

pollData$ = this._http.get(this._url)
  .pipe(
    map(this.extractData),
    catchError(this.handleError)
  );

pollData$.pipe(
  expand(_ => timer(4000).pipe(concatMap(_ => pollData$)))
).subscribe();

---

I'm using RxJS 5 and I'm not sure what the RxJS 4 equivalent operators are. Anyway here is my RxJS 5 solution, hope it helps:

var pollData = this._http.get(this._url)
            .map(this.extractData)
            .catch(this.handleError);
pollData.expand(
  () => Observable.timer(4000).concatMap(() => pollData)
).subscribe();

The expand operator will emit the data and recursively start a new Observable with each emission