[scott_s]

Can someone explain why this:

  geolocator.getLatLng("Forest Park, St. Louis, MO", displayMapAt);

Is better than this?

  displayMapAt(geolocator.getLatLng("Forest Park, St. Louis, MO"));

That is, why is it more sensible for getLatLng to accept a callback function that will accept its result, when one can just pass its result to a function?

[abecedarius]

I expect the call to geolocator requires a network round-trip, with displayMapAt getting scheduled to be called when the result appears; meanwhile your code can do other things. (I'm not familiar with this API, though; I could be wrong.)

Another way to do this sort of thing, that might feel more composable: have geolocator.getLatLng() return a 'promise' object that will be asynchronously resolved.