module.exports.selectiveMerge = (defaultObj, newObj) => {
  const merged = Object.assign({}, defaultObj, newObj);
  for (let propName in merged) {
    if (defaultObj[propName] === undefined) delete merged[propName];
  }
  return merged;
};

filteredMyObjects$ = this.stateService.myObjects$
    .pipe(
      tap((myObjects) => {
        if (!myObjects || !myObjects.length) {
          this.stateService.requestMyObjects();
        }
      }),
      filter((myObjects) => myObjects && (myObjects.length !== 0))
    );

    
public getCurrentUserDetails() {
    // if current user record exists, return it
    if (!_.isNil(this.currentUser)) {
        return of(this.currentUser);
    }

    // if an HTTP request to fetch the user is in progress, return that
    if (!_.isNil(this.currentUserRequest)) {
        return this.currentUserRequest;
    }

    // Otherwise, generate a new multicastable HTTP request
    // publishReplay(1) together with refCount() allows multiple subscribers
    // to consume the observable while only generating a single HTTP request
    this.currentUserRequest = this.http.get<IJsonObject>(this.currentUserUrl).pipe(
        map((response) => this.setCurrentUserDetails(response)),
        tap({
            complete: () => {
                this.currentUserRequest = null;
            }
        }),
        catchError((response: HttpErrorResponse) => throwError(response.error)),
        publishReplay(1),
        refCount()
    );

    return this.currentUserRequest;
}

userService.getCurrentUserDetails().subscribe(...)