[tylerchurch]

I think the main complaints are:

1. Enums are one of the few TypeScript features that isn't a type annotation that can simply be erased. Enums emit code and don't have an equivalent JS feature.

2. Const enums are unsupported by some bundlers/build tools, and so people try to use them and then got burned at build time.

3. The use cases covered by enums are often better served by union types.

None of the above is necessarily fatal for the feature. Certainly people used to enums in other languages still like them. But all 3 combined and the general recommendation these days ends up being just don't use them.

[AprilArcus]

FWIW, Babel has supported const enums for a few years now (since 7.15)

https://babeljs.io/blog/2021/07/26/7.15.0

[rictic]

Yeah, tools can add support for them, but they're fundamentally a whole-program-optimization in a build chain that's 99.9% file-by-file.

Supporting const enums will, by necessity, greatly reduce the maximum performance that toolchain can achieve, because you have to evaluate the entire project to tell whether `Foo.BAR` should be left alone or replaced with a constant defined elsewhere. And in the worst case of an ambient declaration, "elsewhere" could be any file in the project.