Angular Http Interceptor

rest.interceptor.ts

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

@Injectable()
export class RestInterceptor implements HttpInterceptor {
  baseUrl: string; // base API url
  token: string; // Initialize from login

  constructor() {}

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const url = `${this.baseUrl}/${request.url}`;
    const setHeaders = { Authorization: this.token };
    request = request.clone({ url, setHeaders });

    return next.handle(request).pipe(
      catchError(
        (error: HttpErrorResponse): Observable<HttpEvent<any>> => {
          // console.log(error);
          // alert(error);
          // this.someMessageService.send(error);
          // error tracking API
          return throwError(error);
        }
      )
    );
  }
}