rest-api.ts

import { HttpClient, HttpHeaders, HttpHeaderResponse } from '@angular/common/http';
import { Injectable } from '@angular/core';
// import { Observable } from 'rxjs/Observable';
// import { resolveDefinition } from '@angular/core/src/view/util';
import 'rxjs/add/operator/map';

/*
  Generated class for the RestApiProvider provider.

  See https://angular.io/guide/dependency-injection for more info on providers
  and Angular DI.
*/
@Injectable()
export class RestApiProvider {
  private API_URL = "http://localhost:3000/api/user";

  constructor(private http: HttpClient) {
    console.log('Hello RestApiProvider Provider');
  }

  postPergamum(username: string, password: string) {
    return new Promise((resolve, reject) => {
      var data = {
        "username": username,
        "password": password
      };

      let headers = new HttpHeaders();
      // headers.append("Content-type", "application/json");
    
      // let options = new HttpHeaderResponse({ headers: headers});
      headers.set("Content-Type", "application/json");

      this.http.post(this.API_URL, JSON.stringify(data), {headers: headers})
        .subscribe((result: any) => {
          resolve(result.json());
        }, (error) => {
          reject(error.json());
        });
    });
  }
}