ES6 support in Functions
The documentation says that functions can use ES6+ features, however creating a typed array results in an error:
error:
ReferenceError: 'Uint8Array' is not defined
8
votes

Most ES6 syntax should now be supported in Realm Functions. If there are specific additional features you would like added please file a separate feature request.
Additional information:
https://docs.mongodb.com/realm/functions/js-feature-compatibility/index.html