• I’m not sure this proposal can replace Typescript. It doesn’t support any of the more powerful Typescript features as far as I can tell. Basic types in Javascript are a great step forward, but I don’t expect them to be very popular if they can’t describe things like partial JSON objects for working with APIs.

      Out of all the transpiler steps in “modern” JS, I don’t think I’ve ever seen Typescript suck up all that much performance. Splitting code into streaming files, doing whatever dark magic makes modern JS compatible with IE 9 for some reason, and setting up hot reloads used to be the heaviest part of my workflow. Working with Typescript sucked up a lot of RAM in my IDE, but that as mostly because the types I was working with were created in Javascript that read like code golfing sometimes, generating three or four types for every possible API call.