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My main issue with Enums in Typescript: 1. Because they have a runtime representation, I cannot do `import type` — and I am importing the entire file (which mi

My main issue with Enums in Typescript: 1. Because they have a runtime representation, I cannot do `import type` — and I am importing the entire file (which might have a side effect). While it's still not justified (ideally importing should not do anything) the reality in JavaScript is different. 2. I can swap the enum value with a number or a string and it would still work, even if invalid. See https://www.typescriptlang.org/play?#code/KYOwrgtgBAggxgFwJYHsRQN4CgpQKIByMAQgDJ5QC8UADADQ5QAiAkgMonlVQCMWAvliwATYHAA2AQwBOwKADMwIRKnTCUbBGHnyAFAHcAFpIQAuWCrQBKcwCMUKccEkgA3EPWbte+MjQA6Qk48K1coAHpwqAB5AGsRDS0dXV9Vf1YOMhCwyJiAaQSvZJ4aUIioghQEKFlJcXEATyg4B3EhUEgoTWkkEABzVLRMRiCs7gAiPBBJWydxhlwM4ImmJABnGbmBIA https://www.typescriptlang.org/play?#code/KYOwrgtgBAggxgFwJY... for an example 3. On the other hand, I cannot use strings to create an Enum (https://www.typescriptlang.org/play?#code/KYOwrgtgBAygLgJwJYgOYEEDGckHsRQDeAUFFAKIBy6AQgDLlQC8UAROSAIYBGANsKwA0pKABEAkjFoNmbUUgDOPfq2IBfYsUz4FcKJwBcsRCgzY8BFuy58BUAPT2olXHs69euAO7AAJkA https://www.typescriptlang.org/play?#code/KYOwrgtgBAygLgJwJY...) — this is the exact opposite of n. 2 4. Duplicates are possible: https://www.typescriptlang.org/play?#code/KYOwrgtgBAIghgTwPIDMDqxgGsoG8BQUUAymCACaIA0hUAsgPYXW0AqYwAzpQjURuRBcefKKwAWYAE7dEUALxQATKIBiUgJYjaxOABdpPfAF8gA https://www.typescriptlang.org/play?#code/KYOwrgtgBAIghgTwPI...

nidu 6y ago
1. You can define enum like `const enum A {...}` and they will not have runtime representation.
- XVincentX 6y ago
  Correct, but that does not solve the other issues I pointed. Additionally, const enums DO NOT have an associated type. That is a problem in libraries, since users cannot reuse the type definition around (it back ports to a string or a number)
- Jasper_ 6y ago
  const enum doesn't work when in transpileOnly mode (e.g. webpack, Parcel), and Babel treats "const enum" the same as "enum". I'd really love a non-broken const enum in TypeScript, though.
  - XVincentX 6y ago
    I'd love to see them out of the language. I do not have evidence/document supporting this, but I think it was ultimately a failed attempt of copying the C# feature ignoring the fact that JavaScript works differently.
dvdgsng 6y ago
Why is #3 a problem? It's a feature! Enums are a great way to enforce values to a predefined set. I don't want you to work around it with random strings. Use the enum. That's what it is there for.

nidu 6y ago

1. You can define enum like `const enum A {...}` and they will not have runtime representation.

XVincentX 6y ago
Correct, but that does not solve the other issues I pointed. Additionally, const enums DO NOT have an associated type. That is a problem in libraries, since users cannot reuse the type definition around (it back ports to a string or a number)
Jasper_ 6y ago
const enum doesn't work when in transpileOnly mode (e.g. webpack, Parcel), and Babel treats "const enum" the same as "enum". I'd really love a non-broken const enum in TypeScript, though.
- XVincentX 6y ago
  I'd love to see them out of the language. I do not have evidence/document supporting this, but I think it was ultimately a failed attempt of copying the C# feature ignoring the fact that JavaScript works differently.

dvdgsng 6y ago

Why is #3 a problem? It's a feature! Enums are a great way to enforce values to a predefined set. I don't want you to work around it with random strings. Use the enum. That's what it is there for.