What does "turning into Java" even mean? What exactly are you afraid of?
Having actual integers? Threads? Better tooling?
The `class` keyword? It makes the code less verbose.
Optional types? Would you rather write JSDoc comments?
Optional typing actually works amazingly well. You need very few type annotations to get all the tooling benefits. Typically, it's enough to annotate the headers of your function. Type inference takes care of the rest.
1) I was commenting on how they didn't answer the question.
2) JS and Java have very real differences. Turning one into the other DEFINITELY comes with consequences. Maybe you like them, maybe you don't, but it's clearly a legit question.
Regarding #1:
The optional part wasn't Perl6-style optional typing (which I'd be fine with), as I read it, but USING their system at all.
If I teach how to juggle chainsaws, and someone says "isn't that dangerous?" and I respond "No, you don't have to do it", I've not addressed the question at all.
Regarding #2:
For me, it'd be threads (a simple system that is almost never painless), classes (JS today has objects but not classes, and it's a fundamental part of how it works), compilation, and most importantly typing. "Session session = Session.getSession()" is not something I enjoy typing.
Q: "Are you turning Javascript into Java?" A: "No, it's optional"
That's not a strong denial, I was hoping for a more substantial response.