[javascript] 토큰 새로 고침 후 Angular 4 인터셉터 재시도 요청

To support ES6 syntax the solution needs to be bit modify and that is as following also included te loader handler on multiple request


        private refreshTokenInProgress = false;
        private activeRequests = 0;
        private tokenRefreshedSource = new Subject();
        private tokenRefreshed$ = this.tokenRefreshedSource.asObservable();
        private subscribedObservable$: Subscription = new Subscription();



 intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        if (this.activeRequests === 0) {
            this.loaderService.loadLoader.next(true);
        }
        this.activeRequests++;

        // Handle request
        request = this.addAuthHeader(request);

        // NOTE: if the flag is true it will execute retry auth token mechanism ie. by using refresh token it will fetch new auth token and will retry failed api with new token
        if (environment.retryAuthTokenMechanism) {
            // Handle response
            return next.handle(request).pipe(
                catchError(error => {
                    if (this.authenticationService.refreshShouldHappen(error)) {
                        return this.refreshToken().pipe(
                            switchMap(() => {
                                request = this.addAuthHeader(request);
                                return next.handle(request);
                            }),
                            catchError(() => {
                                this.authenticationService.setInterruptedUrl(this.router.url);
                                this.logout();
                                return EMPTY;
                            })
                        );
                    }

                    return EMPTY;
                }),
                finalize(() => {
                    this.hideLoader();
                })
            );
        } else {
            return next.handle(request).pipe(
                catchError(() => {
                    this.logout();
                    return EMPTY;
                }),
                finalize(() => {
                    this.hideLoader();
                })
            );
        }
    }

    ngOnDestroy(): void {
        this.subscribedObservable$.unsubscribe();
    }

    /**
     * @description Hides loader when all request gets complete
     */
    private hideLoader() {
        this.activeRequests--;
        if (this.activeRequests === 0) {
            this.loaderService.loadLoader.next(false);
        }
    }

    /**
     * @description set new auth token by existing refresh token
     */
    private refreshToken() {
        if (this.refreshTokenInProgress) {
            return new Observable(observer => {
                this.subscribedObservable$.add(
                    this.tokenRefreshed$.subscribe(() => {
                        observer.next();
                        observer.complete();
                    })
                );
            });
        } else {
            this.refreshTokenInProgress = true;

            return this.authenticationService.getNewAccessTokenByRefreshToken().pipe(tap(newAuthToken => {
            this.authenticationService.updateAccessToken(newAuthToken.access_token);
            this.refreshTokenInProgress = false;
            this.tokenRefreshedSource.next();
        }));
        }
    }

    private addAuthHeader(request: HttpRequest<any>) {
        const accessToken = this.authenticationService.getAccessTokenOnly();
        return request.clone({
            setHeaders: {
                Authorization: `Bearer ${accessToken}`
            }
        });
    }

    /**
     * @todo move in common service or auth service once tested
     * logout and redirect to login
     */
    private logout() {
        this.authenticationService.removeSavedUserDetailsAndLogout();
    }