JavaScriptCore features

Anyone know exactly what JavaScript features are supported by the version of JavaScriptCore used by the version of RN used by Expo? There are a bunch of Babel transforms listed at https://docs.expo.io/versions/latest/react-native/javascript-environment/ but it’s not clear to me that those are all actually needed by JavaScriptCore.

For various reasons, we are interested in avoiding (or minimizing) transpilation and so would like to know exactly what features we can use in our code.

Thanks in advance.

-Mark