Error handling - server-error.interceptor.ts

server-error.interceptor.ts

import { Injectable } from '@angular/core';
import { 
  HttpEvent, HttpRequest, HttpHandler, 
  HttpInterceptor, HttpErrorResponse 
} from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { retry, catchError } from 'rxjs/operators';

@Injectable()
export class ServerErrorInterceptor implements HttpInterceptor {

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

    return next.handle(request).pipe(
      retry(1),
      catchError((error: HttpErrorResponse) => {
        if (error.status === 401) {
          // refresh token
        } else {
          return throwError(error);
        }
      })
    );    
  }
}

This code gives me error "ERROR TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable". The problem is that interceptor must return Observable<HttpEvent> but line 20 ("return throwError(error);") is in else block so if line 17 condition is true it never returns it.

throwError(error); ==> Deprecated
instead, use it: return throwError(() => error);