Angular HttpBackend implementation using request library

request-backend-test.ts

import { HttpClient } from '@angular/common/http';
import { RequestBackend } from './request-backend';
import * as request from 'request';

let backend = new RequestBackend(request);
let http = new HttpClient(backend);
let response = http.get('https://www.google.com/');

response.subscribe(res => console.log(res));

request-backend.ts

import { HttpBackend, HttpRequest, HttpEvent, HttpResponse, HttpHeaders } from '@angular/common/http';
import { Observable } from 'rxjs';

export class RequestBackend extends HttpBackend {
  constructor(private request: any) {
    super()
  }

  handle(req: HttpRequest<any>): Observable<HttpEvent<any>> {
    return new Observable((observer) => {
      let url = req.urlWithParams;
      let method = req.method;
      let headers = {};
      for (let key of req.headers.keys()) {
        headers[key] = req.headers.get(key);
      }
      return this.request({
        url,
        method,
        headers,
      }, (err, res, body) => {
        if (err) {
          observer.error(err);
          return observer.complete();
        }
        let headers = new HttpHeaders();
        for (let key in res.headers) {
          headers.set(key, res.headers[key]);
        }
        let status = res.statusCode;
        let statusText = res.statusMesage;
        let url = res.url;
        let response = new HttpResponse({
          body,
          headers,
          status,
          statusText,
          url,
        });
        observer.next(response);
        return observer.complete();
      });
    });
  }
}