Load Google Maps JS API in component [Angular]

You can use Promise to load google API asynchronously whenever you want.

// map-loader.service.ts
import ...
declare var window: any;

@Injectable()
export class MapLoader {

    private static promise;
    map: google.maps.Map;

    public static load() {
        if (!MapLoader.promise) { // load once
            MapLoader.promise = new Promise((resolve) => {
                window['__onGapiLoaded'] = (ev) => {
                    console.log('gapi loaded')
                    resolve(window.gapi);
                }
                console.log('loading..')
                const node = document.createElement('script');
                node.src = 'https://maps.googleapis.com/maps/api/js?key=<YOUR _API_KEY>&callback=__onGapiLoaded';
                node.type = 'text/javascript';
                document.getElementsByTagName('head')[0].appendChild(node);
            });
        }

        return MapLoader.promise;
    }

    initMap(gmapElement, lat, lng) {

        return MapLoader.load().then((gapi) => {
            this.map = new google.maps.Map(gmapElement.nativeElement, {
                center: new google.maps.LatLng(lat, lng),
                zoom: 12
            });
        });
    }
}

Component

//maps.component.ts

...
@Component({
  selector: 'maps-page',
  templateUrl: './maps.component.html'
})
export class MapsComponent implements OnInit {       

  @ViewChild('gmap') gmapElement: any;
  constructor(public mapLoader: MapLoader) { }

  ngOnInit() {

      this.mapLoader.initMap(this.gmapElement, -37.81, 144.96)  // await until gapi load
  }

  ...
}

Component HTML

// maps.component.html
<div #gmap ></div>

Don't forget to add CSS to the element.

A solutionis to create the script tag dynamically in ngAfterViewInit()

import { DOCUMENT } from '@angular/common';
...

constructor(private @Inject(DOCUMENT) document, 
            private elementRef:ElementRef) {};

ngAfterViewInit() {
  var s = this.document.createElement("script");
  s.type = "text/javascript";
  s.src = "https://maps.googleapis.com/maps/api/js?key=API_KEY";
  this.elementRef.nativeElement.appendChild(s);
}

See also https://github.com/angular/angular/issues/4903

Update

<div id="map" #mapRef></div>

---

export class GoogleComponent implements OnInit {
      @ViewChild("mapRef") mapRef: ElementRef;
      constructor() { }
    
      ngOnInit() {
        this.showMap();
      }
    
      showMap() {
        console.log(this.mapRef.nativeElement);
        const location = { lat: 28.5355, lng: 77.3910 };
        var options = {
          center: location,
          zoom: 8
        }
    
        const map = new google.maps.Map(this.mapRef.nativeElement, options);
        this.addMarket(map, location);
      }
      addMarket(pos, map) {
        return new google.maps.Marker({
          position: pos,
          map: map,
        });
      }
    
    }