问如何在angular 6和rxjs 6中有新请求时取消正在进行的HTTP请求

EN

constructor(
  private rxnsSearchService: RxnsSearchService,
  private rxnsSearchHitCountService: RxnsSearchHitCountService
) { }
const rxnsObservable: Observable<Array<any>> = this.rxnsSearchService.getReactions(this.searchParams, filters);
const headCountObservable: Observable<number> = this.rxnsSearchHitCountService.getHitCount(this.searchParams, filters);
forkJoin([rxnsObservable, headCountObservable]).pipe().subscribe((results) => { //handling results 
},
  error => {
    console.log(error);
  });

export class RxnsSearchService {
  sub: Subject<any> = new Subject();
  constructor(private httpClient: HttpClient) {}

  getReactions(params: Params, offset: number, perPage: number, filters: any) {
    const body = {
      filters: filters,
      query: params.query
    };
     return this.httpClient.post(environment.rxnsSearch, body).pipe(
      map((response: Array<any>) => {
        return response;
      }),
      catchError(error => {
        console.log(error);
        return throwError(error);
      })
    );
  }
}

export class RxnsSearchHitCountService {
  constructor(private httpClient: HttpClient) {}

  getHitCount(params: Params, filters: any) {
    const body = {
      filters: filters,
      query: params.query,
    };
    return this.httpClient.post(environment.rxnsSearchHitCount, body).pipe(
      map((response: number) => {
        return response;
      }),
      catchError(error => {
        console.log(error);
        return throwError(error);
      })
    );
  }
}