Example Angular v5 Http lib override to include auth headers

http.ts

import { Injectable } from '@angular/core';
import {
  Http,
  XHRBackend,
  RequestOptions,
  Request,
  RequestOptionsArgs,
  Response,
  Headers
} from '@angular/http';
import { Observable } from 'rxjs/Observable';

import 'rxjs/add/observable/throw';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/catch';

import { AuthService as Auth } from './auth.service';

@Injectable()
export class HttpService extends Http {
  private token: string;

  static useFactory(backend: XHRBackend, options: RequestOptions) {
    return new HttpService(backend, options);
  }

  constructor (
    backend: XHRBackend,
    options: RequestOptions
  ) {
    super(backend, options);
  }

  request(
    url: string|Request,
    options?: RequestOptionsArgs
  ): Observable<Response> {

    const token = Auth.getToken();
    this.token = token.value;

    if (typeof url === 'string') {
      if (!options) {
        options = {headers: new Headers()};
      }
      options.headers.set('x-access-token', `${this.token}`);
    } else {
      url.headers.set('x-access-token', `${this.token}`);
    }

    return super.request(url, options)
      .do((res: Response) => {
          // all is well
      }, (error: any) => {
        // user should re-authenticate if not already on the login page
        if (error.status === 403) {
          Auth.logout();
        }
      })
      .catch(this.catchAuthenticationError(this));
  }

  private catchAuthenticationError (self: HttpService) {
    return (response: Response) => Observable.throw(response);
  }
}