[spartanatreyu]

Not that person, but is there an easy way to write something like a basic semver?

export type SemVer = `${number}.${number}.${number}`;

Could you extend it to work with regex groups like:

export const SemVerRegex = /^(?<major>0|[1-9]\d)\.(?<minor>0|[1-9]\d)\.(?<patch>0|[1-9]\d)(?:-((?:0|[1-9]\d|\d[a-zA-Z-][0-9a-zA-Z-])(?:\.(?:0|[1-9]\d|\d[a-zA-Z-][0-9a-zA-Z-]))))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$/;

Could the groups be extracted so you the type back if you ran the regex on a string like: "1.2.3", or "1.2.3-prerelease"?

[matt_kantor]

I don't understand the second part of your comment (that's a value, not a type), but the first part looks like this:

    /** @typedef {`${number}.${number}.${number}`} SemVer */

Here's a playground: https://www.typescriptlang.org/play/?filetype=js#code/PQKhAI...

[spartanatreyu]

Thanks for the example, I had a good play around with it.

The second part of my comment is a value yes, but it's implicitly typed by typescript automatically. I was asking about how to use that type (and it's internals) in jsdoc.

[matt_kantor]

> it's implicitly typed by typescript automatically

What do you mean by this? Can you share an example?

Regular expressions do not act as type guards, and there's no way to express a type that allows one regular expression but rejects another (they're all just `RegExp`): https://www.typescriptlang.org/play/?target=5#code/MYewdgzgL...

[spartanatreyu]

You wouldn't use `test()` like in your example.

`test()` only returns a boolean, you want to look at `exec()` which returns the result of the regular expression (typed as: `RegExpExecArray | null` which you can narrow down to `RegExpExecArray` by checking if the result is null or not).

RegExpExecArray gives you a structure that looks different between the jsdoc version and the typescript version.

The typescript version has `.groups` inside RegExpExecArray.

You can use that as is, or you can add some extra type utilities to extract the named groups from inside the regex. (If you look inside typescript's issues on github you'll find a whole bunch of them that people have wanted typescript to include by default).

There's a few regex PRs to add extraction and syntax checking to typescript by default, but they're delayed until after the compiler switch from ts to go. (but there's porting to go in the PRs anyway).

[matt_kantor]

Thanks for the reply.

> RegExpExecArray gives you a structure that looks different between the jsdoc version and the typescript version.

> The typescript version has `.groups` inside RegExpExecArray.

The JSDoc version has `.groups` too, and it appears to be typed identically to the TypeScript version given similar configuration.

Here's the TypeScript version: https://www.typescriptlang.org/play/?target=5&strictNullChec...

And here's the JSDoc version: https://www.typescriptlang.org/play/?target=5&strictNullChec...

Could you show me what you mean in the playground? You can change it to JSDoc mode by selecting "JavaScript" in the "Lang" dropdown in the "TS Config" tab.

[spartanatreyu]

Your examples has groups only typed as { [key: string]: string }.

It isn't narrowed down to the actual named capture groups inside the regex.

For the whole semver example, we'd want something typed as: { major: string, minor: string, patch: string }.

(sidenote for this semver example and not regex in general: they will be strings because a major of "01" and a patch of "3-prerelease" are both valid. You can parse them into ints later depending on what you're actually doing with the semver)

---

For an example of a type narrowed regex in the ts playground, I'll take the lazy route and point you to an example someone else has made:

https://www.typescriptlang.org/play/?ssl=1&ssc=39&pln=1&pc=3...

You can use a utility library (e.g. ts-regexp, arkregex, etc...), you can use one of the utilities that are shared around the typescript spaces online for the one part you need, or you can make your own utility type.

---

For my use-case, I just want to know that I can change either my code or regex and I'll be alerted before runtime or buildtime if I've forgotten to account for something.

To carry on with the semver example, if a fourth piece of data was added to the incoming string (e.g. product name, build timestamp, build variant, etc...) and I forgot to update both the code and the regex together and instead only updated one, I'd want an alert in my IDE to tell me that I forgot to update the other one.

[g947o]

it is possible to do many of these with @typedef, but it gets difficult with JSDoc very quickly. In TypeScript you can easily create multi-line type aliases. Not quite so in JSDoc.