[STRML]

Reflect.ownKeys will list all keys (string or symbol or otherwise) of an object. It's not clear from the article if it can be excluded via an ES5 definition with `enumerable: false`; perhaps so? In that case, this is pretty cool.

[chriswarbo]

I'm not sure of the JS implementation in particular, but it wouldn't surprise me. Keep in mind that the security/encapsulation features of many languages (private, final, const, etc.) can be bypassed using reflection, especially in "more dynamic" languages like Javascript.

[Arnavion]

There's also Object.getOwnPropertySymbols()

At any rate, Symbol properties aren't meant to be a bullet-proof way to hide private properties. They just reduce the default public API surface of an object by suppressing its internals.