For some reason I don't want to use npm or Atmosphere Google Maps packages in my Meteor app. And try to use Google maps directly. So, inside a React Component I have the following render method and onMapLoaded() class method:
render(){
    return(
        <div ref={el => (this.instance = el)}>
            <p>Map</p>
            <script async defer
                    src={"https://maps.googleapis.com/maps/api/js?key=" 
                    + GoogleMapsKey 
                    + "&callback=" + ????}>
                </script>
            </div>
        );
    }
Can't figure out, how to pass as the callback this.onMapLoaded function ref, not it's value.
It's no dublicate, because there are no explanation how pass React Component' method to script as a paramether.
