Example of an angular auth interceptor

auth-interceptor.ts

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';
import { AuthContextManagerService } from './some/where/authContextService.ts';

@Injectable()
export class AuthorizationInterceptor implements HttpInterceptor {
  constructor(private authContextService: AuthContextManagerService) {}

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const authContext = this.authContextService.getAuthContext();
    const token = authContext && authContext.accessToken;

    if (!token || !this.needAuthHeader(req)) {
      return next.handle(req);
    }

    return next.handle(
      req.clone({
        setHeaders: { Authorization: token },
      })
    );
  }

  /**
   * determine which requests should contain the Authorization token
   */
  private needAuthHeader(req: HttpRequest<any>): boolean {
    return req.url.startsWith('https://') || req.url.indexOf('localhost') > 0;
  }
}