Support for generics is limited in JSDoc compared to TypeScript, especially when arrow function is involved. Things that work fine in TypeScript trigger errors even though they are syntactically the same.

▲ culi 2 days ago | parent [-]

Because AirBnB's ESLint config has been burned into my brain I almost only use arrow functions. I also use generics extremely often. It's definitely a little more clunky but I haven't run into anything you can do in TypeScript that you can't do in JSDoc.

JSDoc also allows you to type stuff in-line. For example I often have to type an empty array like so:

  const [books, setBooks] = useState(/** @type {Book[]} */([]));

If you have a tangible example of a problem you've run into, I'd love to walk through it.

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g947o 2 days ago | parent [-]

JavaScript example:

https://www.typescriptlang.org/play/?filetype=js#code/PTAEAE...

Almost equivalent typescript code:

https://www.typescriptlang.org/play/?#code/C4TwDgpgBA6glsAFg...

(I had to make it a little bit different from the JS code to make it compile)

(Well, this is not exactly about arrow function I guess. I remembered that part wrong.)

Note that I cannot make the type check in JS code to pass. Whatever I do, there is always a error. Meanwhile, it does not take much to TS code to work.

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culi a day ago | parent [-]

Try this out. I think it's a much more faithful representation of your TypeScript example too. JSDoc just wants you to be explicit about the default for generic slots (which is `unknown` in TypeScript).

https://www.typescriptlang.org/play/?filetype=js#code/PTAEAE...

Hover over the variables and you should see that the type inference is working just the same as in your TypeScript example

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g947o a day ago | parent [-]

Ah I see. Looks like you avoided using the "@callback" tag but instead used the "@typedef" tag directly. Thanks!

I do think it illustrates a problem with TypeScript's support for JSDoc though. You see, I started with the code in JS and could not make it work, after which I translated it to TS. In JS/JSdoc, "@callback" is the "idiomatic" way of defining a function callback type with JSDoc. (It also makes it easier to add documentation for each parameter if necessary.) And indeed, @callback works the most of the time, except in such cases where these JSDoc tags don't work nicely together, and these alternatives become necessary.

	▲	culi a day ago \| parent [-]
		This is absolutely a fair point. JSDoc predates TypeScript by over a decade. It's not until more recently that the syntaxes have started to converge. My brain definitely works in TypeScript so I tend to translate from there. I definitely consider myself more familiar with TypeScript than with JSDoc, but sometimes (e.g. here) that's a benefit not a weakness