Angular 5 HttpInterceptor Retry Request

The rxjs 'do' operator does not modify the observer. Returning the 'next.handle(...)' should not work.

Try to use the 'catch' operator instead.

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).catch(() => {
      const newReq = req.clone();
      return next.handle(newReq);
    });
  }

Do not forget to import the catch operator:

import 'rxjs/add/operator/catch';

I always use this code to authenticate, so i will use subjects to implement this logic

import { Injectable } from '@angular/core';
import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor, HttpErrorResponse } from '@angular/common/http';
import { AuthService } from '../services/auth.service';
import { Observable, throwError, BehaviorSubject } from 'rxjs';
import { catchError, filter, take, switchMap } from 'rxjs/operators';

@Injectable()
export class TokenInterceptor implements HttpInterceptor {

  private isRefreshing = false;
  private refreshTokenSubject: BehaviorSubject<any> = new BehaviorSubject<any>(null);

  constructor(public authService: AuthService) { }

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    if (this.authService.getJwtToken()) {
      request = this.addToken(request, this.authService.getJwtToken());
    }

    return next.handle(request).pipe(catchError(error => {
      if (error instanceof HttpErrorResponse && error.status === 401) {
        return this.handle401Error(request, next);
      } else {
        return throwError(error);
      }
    }));
  }

  private addToken(request: HttpRequest<any>, token: string) {
    return request.clone({
      setHeaders: {
        'Authorization': `Bearer ${token}`
      }
    });
  }

  private handle401Error(request: HttpRequest<any>, next: HttpHandler) {
    if (!this.isRefreshing) {
      this.isRefreshing = true;
      this.refreshTokenSubject.next(null);

      return this.authService.refreshToken().pipe(
        switchMap((token: any) => {
          console.log('Token refreshed');
          this.isRefreshing = false;
          this.authService.saveAccessToken(token['access']);
          this.refreshTokenSubject.next(token['access']);
          return next.handle(this.addToken(request, token['access']));
        }),catchError(error => {
          console.log('hi88888888888888');
          if (error instanceof HttpErrorResponse && error.status === 401) {
            this.authService.logout();
            return
          } else {
            return throwError(error);
          }
        }));

    } else {
      return this.refreshTokenSubject.pipe(
        filter(token => token != null),
        take(1),
        switchMap(jwt => {
          console.log(jwt);
          return next.handle(this.addToken(request, jwt));
        }));
    }
  }
}