Check user has internet connection or not using Angular 2

ts

export class ExtendedHttpService extends Http {
constructor(backend: XHRBackend, defaultOptions: RequestOptions) {
        super(backend, defaultOptions);
    }
request(url: string, options?: RequestOptionsArgs): Observable<Response> {
        return super.request(url, options).catch((error: Response) => {
         if (error.status === 0) {
         this._router.navigateByUrl('/no-internet', { skipLocationChange: true });
         let timer = 1000; // in milliseconds
         Observable.interval(timer * 2).subscribe(x => {
             if (timer == 3600000) {
                 timer = 1000;
             } else {
                 timer = timer * 2;
             }
             this.onlineCheck(url).then(() => {
                 // Has internet connection, carry on 
                 window.location.reload();
             })
             });
           }
        })
        .do((res: Response) => {
         // apply logic here for all HTTP request success
        });
    }
 
 onlineCheck(url) {
    let xhr = new XMLHttpRequest();
    return new Promise((resolve, reject) => {
      xhr.onload = () => {
        // Set online status
        this.isOnline = true;
        resolve(true);
      };
      xhr.onerror = () => {
        // Set online status
        this.isOnline = false;
        reject(false);
      };
      xhr.open('GET', url, true);
      xhr.send();
    });
  }
}