See also, Hegel, which also wants to statically type check JS without TS necessarily. Looks like this space is heating up!
Very glad to see so many afford to make javascript a better language there! I played it around, and I found Hegel seems not to support dynamic features like modifications of objects or prototypes. And this is the real difficulty of implementing a sound and complete type system to a dynamic script language like javascript.
Can you share if they have any plans for that?
https://hegel.js.org/try#GYVwdgxgLglg9mABFApgZygCgIYEpEDeAUI...
https://hegel.js.org/try#MYewdgzgLgBCMF4YG8CGAuFAjTBGAvvgNwB...