Board Thread:Support Requests - Getting Technical/@comment-3398493-20180402155228/@comment-27345308-20180403145735

All ES6 features aren't supported, using ES3 keywords such as  in property names isn't really supported and some invalid tokens can also make ResourceLoader choke.

Basically your syntax should be as if you're writing JavaScript ES3 but the methods you're using should be available in ES5.