Datamaps get list of country codes

Got it!

var countries = Datamap.prototype.worldTopo.objects.world.geometries;
for (var i = 0, j = countries.length; i < j; i++) {
  console.log(countries[i].properties);
}

// > Object {name: "South Africa"}
// > Object {name: "Zambia"}
// > Object {name: "Zimbabwe"} 

Here is a list of the ISO-3166-1 3 letter country codes for reference.