This is great but -if I dare - wouldn't it be time to allow js to have type annotations [1] ? As in python, treat it as comments for now but with real syntax and let interesting dialects emerge from the consensus ? I like jsdoc but the syntax is urgh.
It will be impossibly exciting if that proposal happens. I hate build steps, one of the reasons I latched onto JS for my career, but TS is just so good that I had to go full blast with it after using it for the first time.
[1] https://github.com/tc39/proposal-type-annotations