@ngx-translate/core with nativescript-angular

index.ts

import { TranslateLoader, TranslateModule } from '@ngx-translate/core';
import * as fs from 'tns-core-modules/file-system';

@Injectable()
export class NSTranslateLoader extends TranslateLoader {
  public getTranslation(lang: string) {
    return fromPromise(fs.File.fromPath(fs.path.join(fs.knownFolders.currentApp().path, `/assets/i18n/`, `${lang}.json`)).readText('UTF-8'))
      .map((text: string) => JSON.parse(text));
  }
}

// In AppModule imports:
    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useClass: NSTranslateLoader,
      },
    }),