NativeScript - How to Convert Magnetic Heading Degrees to True Heading Degrees

import * as geoLocation from "@nativescript/geolocation";

@Injectable()
export class LocationService {
    private locationManager : CLLocationManager;
    constructor() {
      this.locationManager = CLLocationManager.alloc().init();
      this.locationManager.desiredAccuracy = 3;
      this.locationManager.distanceFilter = 0.1;
      this.locationManager.headingFilter = 0.1;
    }

      getHeading(): number {
    return this.locationManager?.heading?.magneticHeading;
}

    convertDegreesToDirectionText(direction: number): string {
        if (direction == null) {
            return "N/A";
        }
        if (direction > 337.5) {
            return "North";
        }
        if (direction <= 22.5 && direction >= 0) {
            return "North";
        }
        if (direction > 22.5 && direction < 67.5) {
            return "Northeast";
        }
        if (direction >= 67.5 && direction <= 112.5) {
            return "East";
        }
        if (direction > 112.5 && direction < 157.5) {
            return "Southeast";
        }
        if (direction >= 157.5 && direction <= 202.5) {
            return "South";
        }
        if (direction > 202.5 && direction < 247.5) {
            return "Southwest";
        }
        if (direction >= 247.5 && direction <= 292.5) {
            return "West";
        }
        if (direction > 292.5 && direction < 337.5) {
            return "Northwest";
        }
        return "Could not determine direction.";
    }

  startUpdatingLocation(): void {
    this.locationManager.startUpdatingLocation();
  }

  stopUpdatingLocation(): void {
    this.locationManager.stopUpdatingLocation();
  }

  startUpdatingHeading(): void {
    this.locationManager.startUpdatingHeading();
  }

  stopUpdatingHeading(): void {
    this.locationManager.stopUpdatingHeading();
  }
}

import { Component, OnInit } from '@angular/core';
import { LocationService } from './location.service';

@Component({
  selector: 'ns-details',
  templateUrl: './item-detail.component.html',
})
export class ItemDetailComponent implements OnInit {
  item: Item;
  constructor(private locationService: LocationService) {
    this.locationService.startUpdatingLocation();
    this.locationService.startUpdatingHeading();
  }

  ngOnInit(): void {  
     console.log('Magnetic Heading',this.locationService.getHeading());
     console.log('Magnetic Heading Text',this.locationService.convertDegreesToDirectionText(this.locationService.getHeading()));
  }

}