There are, but they have huge performance or usability penalties.

Stuff like intents "this is a math library, it is not allowed to access the network or filesystem".

At a higher level, you have app sandboxing, like on phones or Apple/Windows store. Sandboxed desktop apps are quite hated by developers - my app should be allowed to do whatever the fuck it wants.

Do they actually have huge performance penalties in Javascript?

I would have thought it wouldn't be too hard to design a capability system in JS. I bet someone has done it already.

Of course, it's not going to be compatible with any existing JS libraries. That's the problem.

You can do that by screening module imports with zero runtime penalty.