TranslateLoader for multiple JSON files

MultiTranslateHttpLoader.ts

import {HttpClient} from '@angular/common/http';
import {TranslateLoader} from '@ngx-translate/core';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/observable/forkJoin';

export function translateLoader(http: HttpClient) {
  
  return new MultiTranslateHttpLoader(http, [
    {prefix: './assets/i18n/', suffix: '.json'},
    {prefix: './assets/i18n/countries-', suffix: '.json'}
  ]);
}

export class MultiTranslateHttpLoader implements TranslateLoader {
  
  constructor(private http: HttpClient,
              public resources: { prefix: string, suffix: string }[] = [{
                prefix: '/assets/i18n/',
                suffix: '.json'
              }]) {}

  /**
   * Gets the translations from the server.
   * @param lang
   * @returns {any}
   */
  public getTranslation(lang: string): any {
    return Observable.forkJoin(this.resources.map(config => {
        return this.http.get(`${config.prefix}${lang}${config.suffix}`);
    })).map(response => {
        return response.reduce((a, b) => {
        return Object.assign(a, b);
      });
    });
  }
}