undefined | Better HN

0 pointscromwellian4y ago0 comments

Enums and namespaces are hardly complex code gen or generate 'issues'. People would often manually namespace in JS a few years ago, and namespaces and enums can really just be seen a lightweight holder object instances. Indeed, enums in Java are class instances.

Besides, there is an straightforward way to remove enums from a program just like removing type annotations: Inline them as static fields of an object.

There is a simple syntactic transformation.

    e.g. change 'enum' to 'const', add a '=' before the '{' 
    and use ':' instead of '='
    const HttpMethod = {
      Get: 'GET',
      Post: 'POST'
    };

    // now this no longer breaks
    const method = HttpMethod.Post;

Namespaces can be translated in almost the exactly same way.

0 comments

chrismorgan4y ago

Trouble with your const there as written is that you don’t have a type that’s equal to "GET" | "POST". Fortunately, this can be done without repetition or too much bother:

  const HttpMethod = {
      Get: 'GET',
      Post: 'POST',
  } as const;
  type HttpMethod = (typeof HttpMethod)[keyof typeof HttpMethod];

Maybe wrap the `{…} as const` in Object.freeze(…) for good measure.

It’d be really nice if they’d improve the ergonomics on this in some way (`type Values<T> = T[keyof T]` would reduce it to `type HttpMethod = Values<typeof HttpMethod>`, which is a start but not enough), to make it a genuine and suitable alternative to enum (minus the other frippery that’s generated) and const enum (because it’s pure JavaScript, not an extension).

j / k navigate · click thread line to collapse

0 comments

chrismorgan4y ago

Trouble with your const there as written is that you don’t have a type that’s equal to "GET" | "POST". Fortunately, this can be done without repetition or too much bother:

  const HttpMethod = {
      Get: 'GET',
      Post: 'POST',
  } as const;
  type HttpMethod = (typeof HttpMethod)[keyof typeof HttpMethod];

Maybe wrap the `{…} as const` in Object.freeze(…) for good measure.

j / k navigate · click thread line to collapse