How to make a callback to Google Maps init in separate files of a web app

Question

When I had my Google Maps API snippet:

Answer 1

I could fix it in my code by using the callback and declaring the initMaps function on window as you did:

window.initMap = function(){
  //...
}

However, the trick was to load my custom JS (which also includes the above declaration of initMaps) before loading Google Maps:

Hope this helps.