angular-url-interceptor-sample.ts

export class UrlInterceptor implements HttpInterceptor {
  constructor(private configService: ConfigService) { }

  intercept(req: HttpRequest<any>, next: HttpHandler):
    Observable<HttpEvent<any>> {
    // get API url depending on actual enviroment(prod, local etc)
    const api_url = this.configService.getApiUrl();
    // concat method name with API url
    const request_url = api_url + req.url;
    const intercepted = req.clone({ url: request_url });
    
    return next.handle(intercepted);
  }
}