from chaining to piping

app.service.ts

import { Component } from '@angular/core';

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/retry';
import 'rxjs/add/operator/map';

import { HttpClient } from '@angular/common/http';

@Injectable()
export class AppService implements OnInit {

    constructor(private http: HttpClient) {}
    
    ngOnInit(){
        this.appConfig = this.http.get(this.configUrl);
    }
    
    get(url: string):  Observable<any> {
        let headers = new Headers({'Content-Type' : 'application/json'});
        let options = new RequestOptions({headers: headers});

        return this.http.get(this.rootUrl+url, options)
            .retry(3), // Retry up to 3 times before failing
            .map((response: Response) => <any> response.json()),
            .catch(err => of([]))
        );
    }
}