Angular 4+ HttpClient+Observable

import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import { environment } from '../../../environments/environment';
import { catchError } from 'rxjs/operators';

export class RequestBase {
  constructor(protected http: HttpClient) {}

  protected post(url: string, data: any): Observable<any> {
    return this.http.post(`${environment.API_BASE}${url}`, JSON.stringify(data), { withCredentials: true });
  }

  // private defaultErrorHandler(error: HttpErrorResponse) {
  //   return thorwError()
  // }
}

import { Injectable } from '@angular/core';
import { RequestBase } from './request-base';
import { Observable } from 'rxjs/Observable';
import { HttpClient } from '@angular/common/http';
import { environment } from '../../../environments/environment';

@Injectable()
export class Request extends RequestBase {
  constructor(protected http: HttpClient) {
    super(http);
  }


  public esNativeSearch(para: any ): Observable<any> {
    return this.post('', para);
  }
  }