angular communication with mobile app

import { Component, OnInit } from '@angular/core';

declare const iOS: any;
declare const Android: any;

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss']
})
export class AppComponent implements OnInit {

  constructor() { }

  ngOnInit() {
    this.callMobileFunction();
  }

  getMobileOperatingSystem() {
    const userAgent = navigator.userAgent || navigator.vendor || window['opera'];
    // Windows Phone must come first because its UA also contains "Android"
    if (/windows phone/i.test(userAgent)) {
      return 'Windows Phone';
    }
    if (/android/i.test(userAgent)) {
      return 'Android';
    }
    // iOS detection from: http://stackoverflow.com/a/9039885/177710
    if (/iPad|iPhone|iPod/.test(userAgent) && !window['MSStream']) {
      return 'iOS';
    }
    return 'unknown';
  }

  callMobileFunction() {
    const checkDevice = this.getMobileOperatingSystem();
    if (checkDevice === 'iOS') {
      iOS.calliOSFunction(); // function in ios
    } else if (checkDevice === 'Android') {
      Android.callAndroidFunction(); // function in android
    }
  }
}