Angular 8 http interceptor error handling code example

Example 1: interceptor error handling angular 9

import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpErrorResponse } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';
export class HttpErrorInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request)
      .pipe(
        catchError((error: HttpErrorResponse) => {
          let errorMsg = '';
          if (error.error instanceof ErrorEvent) {
            console.log('this is client side error');
            errorMsg = `Error: ${error.error.message}`;
          }
          else {
            console.log('this is server side error');
            errorMsg = `Error Code: ${error.status},  Message: ${error.message}`;
          }
          console.log(errorMsg);
          return throwError(errorMsg);
        })
      )
  }
}

Example 2: angular interceptor error handling

// src/app/auth/jwt.interceptor.ts

// ...
import 'rxjs/add/operator/do';

export class JwtInterceptor implements HttpInterceptor {

  constructor(public auth: AuthService) {}

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    
    return next.handle(req).do((event: HttpEvent<any>) => {
      if (event instanceof HttpResponse) {
        // do stuff with response if you want
      }
    }, (err: any) => {
      if (err instanceof HttpErrorResponse {
        if (err.status === 401) {
          // redirect to the login route
          // or show a modal
        }
      }
    });
  }
}