JSDoc is TypeScript

https://culi.bearblog.dev/jsdoc-is-typescript/

by culi • 7 months ago

208 275 7 months ago

culi.bearblog.dev

zackify• 7 months ago

5 years ago I was at a meet up and the guy talking was saying how if you don't like typescript these jsdocs are the way to go. Had to explain to my employer attending that it is still typescript. Didn't seem to believe me and was super against typescript but not jsdocs lol

sntxcmp• 7 months ago

The difference is syntax compression imo.

TheRealPomax4• 7 months ago

Had to explain to my employer attending that it is still typescript

"is" is doing a lot of heavy lifting there: JSDoc and TypeScript are two different ways to explicit prescribe typing in a way that tooling can use to determine correctness. The TS syntax is _far_ more powerful, but JSDoc can do most of the common TS use cases, for folks who want to stay in JS land while still benefiting from type tooling (either invoked or straight up built into the IDE).

culi29• 7 months ago

in a way that tooling can use to determine correctness.

As I pointed out in the article, the "tooling" is exactly TypeScript language services. If you are using JSDoc and you get squigglies or intellisense or any other similar features, you are using TypeScript.

You can copy-paste basically any bit of TypeScript into a JSDoc comment and it will work. JSDoc supports any non-runtime feature of TypeScript (so not enums). Even generics! You can even reference TypeScript utility types!

The whole point of this article was to correct the idea that JSDoc is not TypeScript. It absolutely is! There's almost nothing you can't define in JSDoc that you can't define in a .ts file. Albeit with a sometimes clunkier syntax

Sammi3• 7 months ago

In practice today JSDoc 100% completely and utterly always is Typescript.

It might not have been so originally. It might still be possible to do differently. But in practice today you are getting Typescript in your JSDoc with the out of the box tooling that is everywhere.

llimllib2• 7 months ago

counterpoint: JSDoc is not typescript

If you define a type in a file with @typedef, it is automatically exported and there is nothing you can do to control that: https://github.com/microsoft/TypeScript/issues/46011

I tried making a library this way and lacking control over the visibility of the exported types was really painful; it made my intellisense awful because every type I defined at the root was exported from the library

sureglymop6• 7 months ago

I really like it for web components. Lately I have many "my-component.js" files and it's quite nice to just be able to copy them to new projects and have it all work without a build step. But I'm not sure I would use JSDoc over typescript syntax in a large project.

culi29• 7 months ago

That's technically a fair complaint but feels like a minor nitpick. Just don't `@import` the types you don't want to use.

pjmlp2• 7 months ago

TypeScript won over the alternatives, exactly because it is only a type checker, and not a new language.

Granted they initially weren't down that path, but they course corrected it on time, and not much people use stuff like enums in new code.

user39393823• 7 months ago

Agree. It’s superior. I arrived at this about 2 years ago no regrets. Type safety matters on the tooling side anyway. Unless you’re testing for the runtime I guess?

culi29• 7 months ago

I'm glad to hear you've had a good experience with JSDoc but I want to reiterate that my position isn't that JSDoc is superior. Just that it is TypeScript

user39393823• 7 months ago

Yes I’m saying, starting from equality Id add on to say it’s actually the better form. TypeScripts extra enforcement adds complexity without usefulness.

gaigalas5• 7 months ago

The sooner we get https://github.com/tc39/proposal-type-annotations, the better.

Once we get it, there is still a solid decade before runtimes support it, and optimistically, still more 10 years minimum having to deal with an interpreted language that has acquired an unecessary build step.

I absolutely hated when PHP switched from a phpDoc culture with static analysis (and IDE inconsistencies that would click-take you to stubs as well) to actual types. Not because I hate types, but because of the transition period. Once it's gone, it's such a relief to get rid of unecessary docblocks.

conartist611• 7 months ago

That proposal is a nonstarter. It cannot and will not ever be accepted

botten• 7 months ago

Why?

indolering• 7 months ago

Please elaborate!

gaigalas5• 7 months ago

Something needs to change. I don't care about one specific proposal.

It's miserable having a de-facto build step for an interpreted language. Worst of both worlds.

Maybe just TS is fast, but it encourages developers to put more and more stuff into that build step (and they do, they do that a lot). Culturally, that trend is not going to change unless the main reason for having said build step is removed.

The whole babel/transpiling thing was meant to be temporary. It became temporarily permanent / permanently temporary.

g947o16• 7 months ago

The proposal likely won't go anywhere. The first sentence in README says enough about it.

crummy• 7 months ago

For packages typed with JSDoc, CTRL/CMD clicking on a function will take you to actual code rather than a type declarations file. I much prefer this experience as a dev.

ok i didn't think about this, that's an underrated benefit

agumonkey• 7 months ago

could be a customizable behavior in editor/ide though

g947o16• 7 months ago

There is indeed an option in VSCode "typescript.preferGoToSourceDefinition" --

Prefer Go To Source Definition

Makes `Go to Definition` avoid type declaration files when possible by triggering `Go to Source Definition` instead.

IshKebab• 7 months ago

This works with Typescript too though?

filleduchaos• 7 months ago

It doesn't. You might be thinking of libraries that you wrote, not packages from e.g. npm, which are distributed as JavaScript + type definition files not as TypeScript code.

sureglymop6• 7 months ago

A somewhat related thing programmers must understand is that whether you write typescript, JSX, .astro or .svelte files, you are technically not writing JavaScript.

You should occasionally look at the build artifacts of your framework but also ask yourself whether it is worth it to write code that may not represent what actually ends up being executed.

Lately I just use vite with no starter template but with web components and css modules. It at least feels more convenient than using any framework or library.

umanwizard2• 7 months ago

ask yourself whether it is worth it to write code that may not represent what actually ends up being executed.

Doesn't this describe every programming language?

When you write C, you are technically not writing machine code.

Even when you write JavaScript, what actually gets executed is V8 bytecode and/or machine code (depending on whether the JIT fires).

vlovich123• 7 months ago

Yeah it’s a silly line of reasoning. The transformations of TS -> JS are a lot smaller and simpler than C-> asm / machine code; it’s basically just removing type annotations. Now minification and optimization can make the output a lot more terse, but that can be done for JS too. And it’s not as complicated and detached from the source as an optimizing compiler is.

sureglymop6• 7 months ago

That's correct, however I would say there is a small difference in that most of this code still seems just like JavaScript, sometimes it even feels as though it is JavaScript running in the same context when it then gets compiled to run on server/client.

I think the point I'm trying to make is that this can be confusing or even dangerous especially for new developers. It just doesn't hurt to actually look at the Vite plugins transforming it all to understand it instead of making assumptions if we work with it on the daily.

kaufmann• 7 months ago

Aren't you loosing a lot of the declarative features like signals or similar, when you do your projects without those frameworks?

(asking to learn)

sureglymop6• 7 months ago

Somewhat. I could still use framework agnostic state management libraries/patterns and most are (e.g. svelte signals, jotai, zustand, etc.).

I've even used Proxies directly to implement some reactivity before. However as for the "declarative" parts, I think it's just a little bit of a different way to work but you get used to it and imo it pays off. Knowing the web APIs should be a requirement anyway and it doesn't hurt to work with them directly as much as possible.

wvenable2• 7 months ago

This seems like an issue but in all my practical experience it really isn't. TypeScript becomes JavaScript with the types removed. Then you tree-shake, minify, and whatever is executed is no where near what you actually wrote but at the same it totally is the same because that's no different than any other compilation process.

Occasionally, I have to remember that JavaScript has no types at runtime but it's surprisingly not that often.

sureglymop6• 7 months ago

I mean what makes it more acceptable is that you have HMR and instant preview during development. So, all the transformations and bundling aside, you do see how it runs during development.

However I have been in a few situations at work where all of a sudden we did have issues that required us to dig deeper. There were also some bundling related issues that caused problems in production deployments. At that point many co workers had no idea how to even approach it to be honest.

conartist611• 7 months ago

I still think that JS is very much not TS. Most TS code assumes you never need to check for errors because the type checker proves they can't happen.

Then, paradoxically, with no error checking at runtime, it becomes fully possible for JS code to call into TS code in a way that breaks the shit out of the TS compiler's assumptions. In philosophy then TS and JS are as incompatible as GPL and EULA

epolanski4• 7 months ago

The type checker can only prove what is known at compile time and only if you're disciplined.

To bridge runtime and compile time (as your application will likely get some external data) you've got to use a proper parser such as zod[1] or if you want to stretch it even further effect-schema[2].

[1] https://zod.dev/

[2] https://effect.website/docs/schema/introduction/

girvo2• 7 months ago

I’m currently in love with Arktype, and as it supports Standard Schema it plugs into most places that can take Zod schemas too :)

https://arktype.io/

md2242• 7 months ago

Writing a Typescript program that takes external input but has no runtime error checking is already a mistake, though. Dealing with external input requires type assertions (since Typescript doesn't know what the program is getting at compile-time) and if you write type assertions without ensuring that the assertions are accurate, then that's on you, not Typescript.

However, if your point is that Typescript can lull people into a false sense of safety, then sure, I take your point. You have to understand where type assertions are coming into play, and if that's obscured then the type safety can be illusory. The benefits of Typescript require you to make sure that the runtime inputs to your program are sufficiently validated.

conartist611• 7 months ago

TS certainly thinks of external input as a boundary requiring safety, but usually that would mean form input or CLI args parsing or something.

Usually there's little if any protection against a JS caller providing wrong-type args to TS functions.

billyp-rva• 7 months ago

Writing a Typescript program that takes external input but has no runtime error checking is already a mistake, though.

If it's a service, yes, and that's true no matter what technology the service is using. If it's a library, no, because...

and if you write type assertions without ensuring that the assertions are accurate, then that's on you, not Typescript.

That's on whoever is using the library, not the library author. If the library author provides type definitions, and you as the consumer choose to ignore them, then it's on you.

sethaurus• 7 months ago

It doesn't matter if a library is written in TS or JS; you cannot meaningfully protect against other code calling you incorrectly.

Sure, you can check if they gave you a string instead of a number. But if you receive an array of nested objects, are you going to traverse the whole graph and check every property? If the caller gives you a callback, do you check if it returns the correct value? If that callback itself returns a function, do you check that function's return type too? And will you check these things at every single function boundary?

This kind of paranoid runtime type-checking would completely dominate the code, and nobody does it. Many invariants which exist at compile-time cannot be meaningfully checked at runtime, even if you wanted to. All you can do is offer a type-safe interface, trust your callers to respect it, and check for a few common mistakes at the boundary. You cannot protect your code against other code calling it incorrectly, and in practice nobody does. This is equally true for JS and TS.

strongpigeon• 7 months ago

Oh man, the mention of ScriptSharp brought back memories. I started my career at MSFT on SharePoint and the front end was an ungodly mix of ScriptSharp and other stuff.

I vividly remember being in a meeting with the Exchange team (about building shared frontend components) arguing for us to adopt TS instead as it had a better experience and very rapidly growing popularity (that was about 10 years ago). Plus, as strong as Nikhil [0] was, he was basically the only person behind ScriptSharp while TS had a whole team.

Of course, this being MSFT, this effort went no where. While true that the TS toolchain lacked the tree-shaking that ScriptSharp had, I was just annoyed that we had to build stuff using what was obviously an dead-ish language with limited support, many flaws, and no resources to improve it.

But hey, at least it wasn’t GWT.

[0] https://github.com/nikhilk

culi29• 7 months ago

From what I've read, many of TypeScript's design regrets have political origins. Enums and other features that oppose TS's structural type system were added as compromises with C# developers in MS and similar negotiations with the Angular team in order to increase adoption of TypeScript over alternatives

pavo-etc• 7 months ago

I would love to know where you read this!

paulddraper2• 7 months ago

And in fact, this what the Closure Compiler does…typecheck based on JSDoc.

However, the precision and completeness is not nearly what can be expressed in TypeScript. With generics particularly.

culi29• 7 months ago

Care to give an example? In another reply I pointed out how advanced JSDoc syntax's support for generics is.[0] Even allowing for `extends` and default values for generic slots.

The clunkiest part is in the way you "pass in" a generic to a slot. But this is solved by typing the return type.

I use generics pretty extensively and I've not yet come across a use-case JSDoc couldn't handle

[0] https://news.ycombinator.com/item?id=46267810

paulddraper2• 7 months ago

Ah.....you're putting TypeScript in JSDoc annotations.

Which is a lot different than vanilla JSDoc [1].

I understand.

[1] https://jsdoc.app/

mirekrusin3• 7 months ago

1. there are plenty things you can't express in jsdoc but can in typescript, flow did the right thing here where you have access to full language, not sure why typescript never did it, they could, with the same syntax flow is using

2. you can have navigation that goes to typescript file instead of definition, just arrange your exports in package.json correctly (first ones take precedence)

measurablefunc• 7 months ago

TypeScript's type system is Turing complete so you have access to essentially unlimited expressivity (up to the typechecking termination depth): https://news.ycombinator.com/item?id=14905043

creatonez• 7 months ago

there are plenty things you can't express in jsdoc but can in typescript

This isn't really true anymore, they have systematically added pretty much every type system feature to the JSDoc-like syntax.

g947o16• 7 months ago

Having JSDoc-like syntax isn't the same as it being fully supported. If you have a large enough codebase, you'll likely find a few cases where things work in TypeScript but its equivalent somehow fails type check in JSDoc.

culi29• 7 months ago

Well I'd love to hear some concrete examples if you have any on hand! I was of the same opinion as you until I refactored a project of mine to use JSDoc.

Since any TypeScript type can be expressed in JSDoc, I imagine you're mostly thinking of generics. At least that was my main sticking point. JSDoc does actually have generic slots with the @template tag. Actually using them in practice is a little unintuitive but involves typing the return type. E.g. for a function it'd look like this:

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

efortis5• 7 months ago

and types can be written in .d.ts file(s), which can be used in jsdoc out of the box (no import needed)

afavour2• 7 months ago

ReturnType is TypeScript, no? You’re using JSDoc to express but it’s a TypeScript type.

g947o16• 7 months ago

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.

g947o16• 7 months ago

Last time I checked, there isn't a way to extend types (https://www.typescriptlang.org/docs/handbook/2/objects.html#...) that works exactly like in TypeScript.

mirekrusin3• 7 months ago

Things like type star imports, destructured imports or satisfies operator don't work in jsdoc.

All non erasable constructs won't work as well of course but playing devil's advocate you could explicitly state that you're interested in erasable constructs only because ie. 1) that's what typescript should be doing from day 1 and/or 2) it seem to be the future with ie. nodejs adopting built in type erasure support.

austin-cheney2• 7 months ago

Who cares what some framework guy thinks. When I was writing JavaScript for employment most people doing that work were hyper concerned with how to write code and what other people thought about it. These kinds of opinions and conversations are critically important for beginners, but junior and senior developers never seemed to get past these concerns of basic literacy.

When other developers and non-developers look at JavaScript developers as small children it’s because the maturity difference is very evident from the outside. Once developers get past basic literacy they are free to worry about architecture, performance, scale, platform independence, and more. For most JavaScript developers they just expect some framework to do it for them.

christophilus3• 7 months ago

Dunno. Your comment seems pretty immature and strangely emotional. If you think you’re too good for these sorts of articles and this sort of tech, then maybe you’re also too good for the related discussion.

austin-cheney2• 7 months ago

I guess you are only looking for praise or pity. If that is the case then yes, I am too good/mature for your work and discussions.

akst2• 7 months ago

I'm actually using JSTypes in app, I don't mind it.

I choose to use it because I didn't want to deal with a build step for a smaller project. The project has grown and I am looking at adding a build step for bundling but still not too worried about using JSDoc over TS.

This might be my config, but one thing that does annoy me is whenever I define a lambda, I need to add an doc type. I guess if that's disincentivising me from writing lambdas maybe I should just add a TS compile step lol.

----------------------

Here's an example - I got some config typed with this function https://github.com/AKST/analysis-notebook/blob/c9fea8b465317... - Here's the type https://github.com/AKST/analysis-notebook/blob/c9fea8b465317... - And here's something to generate a more complicated type for defining config knobs https://github.com/AKST/analysis-notebook/blob/c9fea8b465317...

g947o16• 7 months ago

These days you can run TypeScript files as-is (type stripping) for testing in many runtimes, and for bundling, most bundlers support using a ts file as the entry point directly.

akst2• 7 months ago

yep! However this is a website I made for hosting my own notes in the browser browser (sorry for the load times, no bundler so each file is a seperate request)

https://akst.io/vis/20250601-complex-geo/?app=unsw.2102.01-1

That said, when I write tests, I write them in Typescript for that reason.

epolanski4• 7 months ago

Not really, at best it's a verbose and limited subset.

https://github.com/tc39/proposal-type-annotations?tab=readme...

efortis5• 7 months ago

Although it's more verbose, it makes code less dense because it lives outside the function parameters.

Also, it's not a super limited subset. For instance, you can write types in .d.ts the IDE uses those types in jsdoc out of the box.

epolanski4• 7 months ago

The list of things jsdoc cannot do is long but a simple example is overloading, you cannot express this[1] in jsdoc, and if you need to reference .d.ts files you're back at using TypeScript, so the point of JSDoc was...?

If you need precise return typing, conditional types, literal values, etc, you aren't going far if anywhere with JSDoc.

[1] https://shorturl.at/pg5dL

culi29• 7 months ago

It's certainly more verbose but certainly not a limited subset. You can copy paste any typescript Type or Interface in a jsdoc @typedef. As I stated in the article, it's still the TypeScript language service that's analyzing either JSDoc-defined types or TypeScript defined types. It's typescript all the way down

But JSDoc lets you do pretty much everything that isn't a runtime feature of TypeScript (e.g. enums, namespaces, etc). Even generic slots are supported

g947o16• 7 months ago

You just haven't worked in a complex enough project yet.

I found several limitations and already opened several issues on github.

mohsen1• 7 months ago

Webpack is typed using JSDoc and type-checked via TypeScript -- I started this migration a while ago. It works pretty well

culi29• 7 months ago

Wow I had no idea! Have you written anywhere about your experiences?

efortis5• 7 months ago

jsdoc is nice because you don’t have to write the non-helpful types.

---

In WebStorm, jsdoc can be rendered in HTML, which makes the code easier to scan. Here's a side-by-side VSCode vs WebStorm:

https://x.com/efortis/status/1989776568676221137

---

And in jsdoc you can have an inline description:

  @prop {number} width  Video width in pixels

culi29• 7 months ago

you don’t have to write the non-helpful types

This entirely depends on your tsconfig setup. You can run a JSDoc-typed project in strict mode exactly the same way you would a *.ts-typed project.

efortis5• 7 months ago

Do you know if it's possible to do that the other way around?

neallindsay2• 7 months ago

Some TypeScript features are only available through JSDoc. The one I encounter most often is `@deprecated`.

pyrolistical• 7 months ago

What do you mean? Jsdoc has it

https://jsdoc.app/tags-deprecated

christophilus3• 7 months ago

I think he’s saying that only JSDoc has it. Vanilla TS doesn’t.

neallindsay2• 7 months ago

Isn't that what I said?

emseetech2• 7 months ago

I'm a fan of anything that allows me to build with javascript that doesn't require a build step.

Modern HTML/CSS with Web Components and JSDoc is underrated. Not for everyone but should be more in the running for a modern frontend stack than it is.

auxiliarymoose3• 7 months ago

Agreed on native HTML+CSS+JSDoc. An advantage in my use-cases is that built-in browser dev tools become fluid to use. View a network request, click to the initiator directly in your source code, add breakpoints and step without getting thrown into library internals, edit code and data in memory to verify assumptions & fixes, etc.

Especially helpful as applications become larger and a debugger becomes necessary to efficiently track down and fix problems.

bobbylarrybobby• 7 months ago

On the one hand I can see the appeal of not having a build step. On the other, given how many different parts of the web dev pipeline require one, it seems very tricky to get all of your dependencies to be build-step-free. And with things like HMR the cost of a build step is much ameliorated.

prisenco7• 7 months ago

I haven't run into any steps that require one, there's always alternatives.

Do you have anything specific in mind?

junon2• 7 months ago

Webcomponents are a pain in the ass to make, though. That is, sufficiently complex ones. I wish there was an easier way.

prisenco7• 7 months ago

They could have better ergonomics and I hope a successor that does comes out but they're really not that bad.

eric-p7• 7 months ago

I've built Solarite, a library that's made vanilla web components a lot more productive IMHO. It allows minimal DOM updates when the data changes. And other nice features like nested styles and passing constructor arguments to sub-components via attributes.

https://github.com/Vorticode/solarite

jeswin• 7 months ago

It's ok now, at least for me. There are still challenges around theming and styling because of styling boundaries (which makes Web Components powerful, but still). A part of it is about tooling, which can be easier to improve.

Try my tiny web components lib if you want to keep JSX but not the rest of React: https://github.com/webjsx/magic-loop

gedy• 7 months ago

Svelte has a pretty nice support for this via https://svelte.dev/docs/svelte/custom-elements

It's not a no-build option though.

WorldMaker• 7 months ago

I find Web Components aren't as much of a pain to write if you ignore the Shadow DOM. You don't need the Shadow DOM, it is optional. I don't think we are doing ourselves too many favors in how many Web Component tutorials start with or barrel straight into the Shadow DOM as if it was required.

mmcromp• 7 months ago

Why? The half a second for the HMR is taking up too much your day?

prisenco7• 7 months ago

No, because layers of abstraction come at a cost and we have created a temple to the clouds piled with abstractions. Any option to simplify processes and remove abstractions should be taken or at least strongly considered.

Code written for a web browser 30 years ago will still run in a web browser today. But what guarantee does a build step have that the toolchain will still even exist 30 years from now?

And because modern HTML/CSS is powerful and improving at a rapid clip. I don't want to be stuck on non-standard frameworks when the rest of the world moves on to better and better standards.

xigoi• 7 months ago

Having all your code go through a multi-step process that spits out 30 different files makes it impossible to know what’s really happening, which I’m uncomfortable with.

odie5533• 7 months ago

I have not written a line of JavaScript that got shipped as-is in probably a decade. It always goes through Vite or Webpack. So the benefit of JS without a build step is of no benefit to me.

prisenco7• 7 months ago

Dare to dream and be bold.

Seriously, start a project and use only the standards. You'll be surprised how good the experience can be.

winrid• 7 months ago

TS is worth the build step.

prisenco7• 7 months ago

JSDoc is TypeScript.

pjmlp2• 7 months ago

I was already doing that in 2010, with the JSDoc tooling in Eclipse and Netbeans back then.

However I don't get to dictate fashion in developer stacks.

mb2100• 7 months ago

This. Or use ts-blank-space if you prefer TypeScript over JSDoc. That's what we do in https://mastrojs.github.io

fergie• 7 months ago

Modern HTML/CSS with Web Components and JSDoc is underrated.

I've been a front end developer for 25 years. This is also my opinion.

kellengreen• 7 months ago

Came here to write this exact sentiment. Not everything needs a massive build pipeline.

mmcnl• 7 months ago

You don't need a build step anymore with TypeScript since Node 24.

prisenco7• 7 months ago

I'm referring to client-side javascript.

casmn• 7 months ago

I am always using JSDocs whenever i am writing a function - i think this is a good practice for every developer - even if it's a simple function.

afavour2• 7 months ago

Eh. I agree with the principle. I’ve written personal projects with JSDoc because I truly love the idea of finally being done with build systems and just serving the files I write without a step in between.

But it’s more annoying than just writing TypeScript. There are ways to express just about everything TypeScript can but they’re all more difficult and convoluted (generics are a great example). For a project of any reasonable size I’m still going to advocate to use TypeScript.

g947o16• 7 months ago

I work in a codebase that unfortunately does not support TypeScript. I use JSDoc extensively, although not with type check enabled (due to various limitations). I also work on other projects with TypeScript. My own experience is that the DX with "real" TypeScript is much, much better than JavaScript with JSDoc, without question. JavaScript with JSDoc is much more verbose, with a lot of limitations when types get long or complex compared to TypeScript. The official TypeScript language service also does not provide the same level of support in very subtle ways.

Basically, the fact that it works does not mean it works well, and I don't recommend anyone going in this other direction unless they understand what they are getting into.

culi29• 7 months ago

although not with type check enabled (due to various limitations)

Curious what limitations there are on static type checking. It seems like a matter of your IDE setup

My own experience is that the DX with "real" TypeScript is much, much better than JavaScript with JSDoc

I agree with the DX point. I would just point out that if you're using JSDoc and getting intellisense from it, you are using TypeScript

g947o16• 7 months ago

Not a limitation in language service, but an issue with the codebase itself -- legacy codebase with a lot of missing/incorrect typing from upstream JavaScript code (owned by other teams), making it practically impossible to actually run type check.

auxiliarymoose3• 7 months ago

This is how I develop web software, and I've found it productive and maintainable.

A bonus of this approach is that it clearly delineates what type information is available at runtime, vs what type information is just a comment. (especially useful when working with serialized data).

I also like that it generally means all of the preconditions and postconditions for functions are in a single place (both the prose and the technical information are in the JSDoc comment), keeping the code itself low-noise and boiled down to its essence, and providing a natural place to write example inputs and outputs to guide usage.

As for generic types, I use them extensively, and this is made less verbose e.g. on function calls by using an @type annotation on the function which accepts a TypeScript signature without needing separate @template + @param annotations.

It's awesome stuff, and I'm happy that TypeScript works so well with JSDoc!

sgammon2• 7 months ago

No it isn’t, otherwise Closure Compiler would (still) be running MS365

sgammon2• 7 months ago

“There’s nuance” yeah as much in my comment as the headline at the top of the article

etoxin• 7 months ago

So, some history. When SPA's started to boom on the web JSDoc was a life saver for typing. Application state was getting more complex. We needed more guard rails.

Then Google Closure Compiler came along which added type safety via JSDOC and TS came along with (TS)JSDoc support and it's own TS syntax.

The community chose native TS and Google Closure compiler slipped away into the background.

So (TS)JSDoc support is a relic from when Microsoft was trying to get market share from Google.

Today in 2025, TS offers so much more than the (TS)JSDoc implementation. Generics, Enums, Utility types, Type Testing in Vitest, typeguards, plus other stuff.

Today I use TS. I also use plain JSDoc for documentation. e.g. @link and @see for docs. Or @deprecated when I'm flagging a method to be removed. @example for a quick look up of how to use a component.

TS and plain JSDoc are both important together. But (TS)JSDoc alone, is a relic of the past.

culi29• 7 months ago

Today in 2025, TS offers so much more than the (TS)JSDoc implementation. Generics, Enums, Utility types, Type Testing in Vitest, typeguards, plus other stuff.

This was my main impetus for writing this article. Modern JSDoc uses the TypeScript language service. You can use generics, utility types, typeguards (including the `is` keyword), regex parsing, etc all with just JSDoc.

I used these features extensively (especially generics) in a personal project and managed to do it all in JSDoc.

c-hendricks3• 7 months ago

JSDoc does not understand typescript syntax though? The typescript language server just kinda plows through/over JSDoc sure, but try getting JSDoc to parse some of the TS-ified things that JSDoc has alternatives for.

https://github.com/jsdoc/jsdoc/issues/1917

https://github.com/jsdoc/jsdoc/issues/1917#issuecomment-1250...

apatheticonion4• 7 months ago

JSDoc is missing a lot of basic capabilities. For example a TypeDef is automatically exported which can cause collisions and forces you to repeat or inline types.

Types for classes are poor and often you'll find yourself creating a `.d.ts` file or `.ts` file to export non trivial types - however the target file doesn't know how to consume them.

k3vinw3• 7 months ago

I’m curious how type checking is possible in a JDoc project. As far as I’m aware there’s no way to get type checking to work without tsc or a TypeScript LSP plugin.

johnfn• 7 months ago

The article is an explicit response to the point you’re making.

phil2942• 7 months ago

So (TS)JSDoc support is a relic from when Microsoft was trying to get market share from Google.
Today in 2025, TS offers so much more than the (TS)JSDoc implementation. Generics, Enums, Utility types, Type Testing in Vitest, typeguards, plus other stuff.

None of that is true! Please don't share misinformation without looking it up first.

jcbhmr• 7 months ago

JSDoc works great for buildless application setups! One downside is that if you publish a library to npm you still need a build step to generate .d.ts files from your JSDoc type annotations so that npm shows a "TS" badge on the npm package page. This also seems to apply to VSCode's intellisense which keeps trying to poke you to "try to install @types/jsdoc-typed-package to get type information". Other JS ecosystem tooling also doesn't seem to process JSDoc types at all such as jsdocs.io or tsdocs.dev. So for libraries we're stuck with .d.ts generation via "tsc --allowJs --checkJs --declaration ..." even if it's all JS.

npm displays packages with bundled TypeScript declarations https://github.blog/changelog/2020-12-16-npm-displays-packag...

JSDoc-typed node modules require special configuration in consumers to be useful https://github.com/microsoft/TypeScript/issues/19145

Brysonbw• 7 months ago

I'm a big advocate for explicit type annotations in code. Likewise, either or is good with me. However, these days I lean towards using JSDoc only because I prefer not to add typescript lib and an additional build step just to get type safety in a project.

Also, you can use both (if that's what you prefer).

CSSer• 7 months ago

For packages typed with JSDoc, CTRL/CMD clicking on a function will take you to actual code rather than a type declarations file. I much prefer this experience as a dev.

More broadly, this is the default behavior of JS even without JSDoc blocks, and it ought to be the default behavior everywhere, including TS. I'm not alone in this sentiment, but it's incredibly contentious. There's been an open GH issue about it with hundreds of replies for years. I have no idea why they can't just pick a different shortcut for viewing types and call it a day. They'd be doing the entire ecosystem a favor.

Waterluvian• 7 months ago

A few things I've come to personally believe after spending years developing web and robotics software in Python/JavaScript then spending years having to maintain while constantly adding new features and dealing with company pivots:

- The types exist whether you write them down or not.

- If they're not written down, they're written down in your head.

- Your head is very volatile and hard for others to access.

- Typing is an incredibly good form of documentation.

- JSDoc and TypeScript are standards/formats for typing. Like any tools, they both have advantages and disadvantages. Neither is objectively better than the other.

- Make informed decisions on how you'll describe your types, and then be consistent and unsurprising.

- A type checker is the computer saying, "okay then, prove it" about your program's type validity.

- Not every program benefits from the same amount of "prove it."

- Too much can be as bad as too little. You're wasting resources proving throwaway code.

- I like languages that let you decide how much you need to "prove it."

culi29• 7 months ago

JSDoc and TypeScript are standards/formats for typing. Like any tools, they both have advantages and disadvantages. Neither is objectively better than the other.

Agreed. Just to clarify, my intentions with this post weren't to advocate for one over the other. Just to point out that they are the same thing. They are both TypeScript.

KPGv25• 7 months ago

They are both TypeScript.

I take issue with this position because this seems to imply "PureScript and JavaScript are both JavaScript" is a true statement merely because one of them turns into the other with tooling.

mattmanser• 7 months ago

I don't know how anyone can agree with this, because it pivots on this outrageous claim:

"Like any tools, they both have advantages and disadvantages"

You cannot make any argument based on such a position. Putting aside anyone's views on TS or JSDoc, tooling is of extremely variable quality, and lots of tools ARE objectively much worse than other tools.

It we can't point at tools and say this one is better than that one, we might as well give up.

I always remember a scene in Will & Grace where Will is trying to get his boss to say one thing is better than the other. He's brought a lovingly hand-crafted sandwich made with amazing, bread, fillings, etc. and a store bought sandwich made with cheap bread/fillings. He asks his boss to try both and say which one he likes more.

His boss says something like the store bought one reminds him of his grandma's sandwiches, so invokes nostalgia, and still can't make a decision.

Don't be that boss.

john01dav• 7 months ago

- I like languages that let you decide how much you need to "prove it."

Rust is known for being very "prove it," as you put it, but I think that it is not, and it exposes a weakness in your perspective here. In particular, Rust lets you be lax about types (Any) or other proved constraints (borrow checker bypass by unsafe, Arc, or cloning), but it forces you to decide how the unproven constraints are handled (ranging from undefined behavior to doing what you probably want with performance trade-offs). A langauge that simply lets you not prove it still must choose one of these approaches to run, but you will be less aware of what is chosen and unable to pick the right one for your use case. Writing something with, for example, Arc, .clone(), or Any is almost as easy as writing it in something like Python at the start (just arbitrarily pick one approach and go with it), but you get the aforementioned advantages and it scales better (the reader can instantly see (instead of dredging through the code to try to figure it out) "oh, this could be any type" or "oh, this is taken by ownership, so no spooky action at a distance is likely").

throawayonthe• 7 months ago

is that not exactly "deciding how much to prove it?"

MrJohz3• 7 months ago

In practice, though, writing stuff with `Arc` or `.clone()` or `Any` is not as easy as it would be in Python because you've got to write a bunch of extra boilerplate. It's much easier to have local `i64` values that you can pass around as `Copy`. So if all you need are local i64s, then you'll take the easier option and do that.

The same is true at multiple levels. `.clone()` is relatively easy to use, although once you learn the basic rules for referencing, that also becomes easier. `Arc` solves a specific problem you run into at a certain point sharing data between threads, but if you're not sharing data between threads (and most of the time you're not), it's just boilerplate and confusing, so you might avoid it and at worst use `Rc`. `Any` is rarely an obvious choice for most contexts, you really are going to only use it when you need it.

The result is that for most simple cases, the precise and "proven" option is typically the easiest to go for. When you deal with more complicated things, the more complicated tools are available to you. That seems exactly what the previous poster described, where you can decide yourself how much you need to prove a given thing.

user39393823• 7 months ago

I'll take a more definite position. Build pipelines are the devil. Every square inch of surface complexity you add to whatever you're doing, you will pay for it. If there's a way to get the benefits without the build step, that's your choice. You may need runtime type enforcement, so that's not JSDoc, and you're doing that with... JS so that's already suspicious but the use case def exists. JS, the DOM, HTTP, this whole stack is garbage at this point so arguing about the type system is a little idk hard to care about personally. I have a solution that lets you discard most of the web stack, that's more interesting to me.

jama2112• 7 months ago

And if your boss is the type to pivot way too often and want it done yesterday, then they don’t deserve code that is prove in the right places so you just get an LLM to add typing to everything after the fact…

jve2• 7 months ago

then they don’t deserve code that is prove

I don't get it. Types are a way to write code. Nothing to do with how fast/much the code changes.

scotty796• 7 months ago

I like languages that let you decide how much you need to "prove it."

I love that too. Are there any other languages than TS that have this as a core design feature?

jve2• 7 months ago

As I understand that is the core design feature of any strongly typed language.

Culonavirus• 7 months ago

Your head is very volatile and hard for others to access.

One of the lessons you learn while doing this job is that "others" includes "yourself in the future".

(Of course people will tell you this way before you find out yourself, but what do they know...)

have_faith• 7 months ago

"who wrote this garbage?... oh yeah that was me"

christophilus3• 7 months ago

Yeah. I learned this lesson 25 years ago in university. SQL, Lisp, and whatever scripting language I was learning at the time were always much harder to reason about vs statically typed languages— particularly in team projects. Over the years, I’ve gotten comfortable with SQL, but I always prefer static typing when I can get it.

dominicrose2• 7 months ago

The types exist whether you write them down or not

That's easy to say when we're talking about primitive arguments in private functions, or primitive local variables, but let's not ignore the fact that it takes much more work to write a C# program than a Ruby program for instance.

We can see that by looking at a vanillajs library's typescript typings that were created after the js library when typescript didn't exist. The types are insanely complex and if you get one type wrong you can break compilation of some library user's program (its happened to me).

That being said I'm aware that dynamic programming languages are a "use at your own risk" type of language.

dzonga• 7 months ago

are dynamic languages really a "use at your own risk" ? or it's about changing frame of mind ?

my take is if you treat your program as a series of data flows - then use primitives such as maps | arrays - then you don't need as much typing or typing at all. a map doesn't need to take a shape or a Person | Manager - either the keys exist or they don't and almost every language has guards to ensure you can safely navigate existence of keys.

but then again my realm is mostly around - web | data systems - if I was dealing with OS level systems and needed to make sure i have i64 ints then yeah typing would be crucial.

eezing• 7 months ago

Aside from the following, JSDoc is absolutely TypeScript.

Discriminated unions, conditional types, mapped types, template literal types, recursive type aliases, higher-kinded type patterns, generic constraints with conditional inference, the infer keyword, never type exhaustiveness checking, const assertions, readonly tuple and array inference, exact object types, key remapping in mapped types, indexed access types, variance annotations, assertion signatures, strict null checking with flow-sensitive narrowing, definite assignment assertions, the satisfies operator, declaration merging, module augmentation, symbol-typed properties, type-safe enums

…and not written via comments

culi29• 7 months ago

Yes, all of these are supported in JSDoc because they are supported in TypeScript. Because JSDoc is TypeScript. You can either define your types in JSDoc comments or in .ts files.

I really mean it. You can even use the @satisfies operator like so

  /** @satisfies {Type} */

Discriminated unions, conditional types, mapped types, template literal types, etc work exactly the same way if you define them in a JSDoc comment as if you define them in a .ts file

cutler• 7 months ago

Sounds like Scala type fetishism all over again.

brazukadev4• 7 months ago

I like the mention to someone from the React team as it seems TypeScript/type safety did not help them create better, safer software.

jason_oster• 7 months ago

Writing better, safer software is more of a cultural problem than a language problem. Languages can only do so much.

notpushkin• 7 months ago

What I would really like to see is a TS compiler that emits .js libraries with typing information compiled as JSDoc comments.

apatheticonion4• 7 months ago

Personally, given the limitations of JSDoc, I'd like to see a header-file like definition system for build-less applications (like libraries).

    /
      index.js
      index.d.ts

Where values in `index.js` can be typed in the header file with complete TypeScript syntax and those types are present in the target file via intellisense and type checking

    // index.js
    function useStr(x){} // has intellisense for "string"

    useStr("Hello")
    useStr(42) // IDE and type checker error

And

    // index.d.ts
    declare function useStr(x: string): void

MrJohz3• 7 months ago

This can be done, and is done in some projects, but the problem is that you need to manually maintain both sets of files, which can easily go out of sync if you're not careful. You also lose out on the ability to check your own code - using the header file you've written there, you can't really check the implementation of `useStr` to check that it works.

The advantage of JSDoc is that the TypeScript compiler treats it as equivalent to TypeScript source code, which means you've still got access to type checking inside your functions.

One thing I've seen in a few places is still to have DTS files that declare all sorts of types that are used in the application, and then have those files imported by JSDoc comments. That way, you've got TypeScript syntax for your types, which tend to get bulky and difficult to read in JSDoc syntax, but you still don't need a build system because the DTS imports are ignored completely at runtime.

apatheticonion4• 7 months ago

You can define a declaration file alongside its target however the target does not use the types defined within its declaration within itself - only consumers see the types.

There are three issues with that.

The first is that JSDoc doesn't support everything you need in TypeScript and there is a lot of inlining (like typedef causes collisions, there's no importing a type without also re-exporting it from the importing file unless you inline the import)

The second is that JSDoc isn't picked up from imported libraries (or at least I don't think it is?)

Lastly, you still need a transpiler to remove the comments and build d.ts files.

In the end, JSDoc isn't practical for projects. The header file strategy means you don't need to transpile ever (only a typechecker) and you'd get the full suite of TypeScript functionality - at the cost of synchronization overhead.

For a project using JSDoc, you'll graduate to TypeScript when there is sufficient complexity anyway. Migrating from a d.ts file is way easier (potentially automatable) than migrating from JSDoc.

auggierose• 7 months ago

Been there, tried that. When starting to write JavaScript in anger 3 or 4 years ago, I started out with JSDoc, because my impression was also, hey, that is like TypeScript, but closer to the metal and maybe with less magic. A few months in I realised that TypeScript is just a better and more well-rounded implementation of what JSDoc has to offer (I don't remember now, but there were annoying things that you would expect would work in JSDoc, but didn't quite).

Just use TypeScript.

Lorin2• 7 months ago

Not when the TS team refuses to fix long standing issues preventing JSDOC from operating properly in VSC, for example https://github.com/microsoft/TypeScript/issues/16665

n2d4• 7 months ago

To be honest, I find Ryan Cavanaugh's argument against this quite convincing. It's weird to have something documented if you import the .ts file, but not if you import a .d.ts generated from it. If you want to show the value of the default argument of a function, you should probably just add it to the doc comment — not the type.

Lorin2• 7 months ago

The argument is that it doesn't surface the default written within the jsdoc block comment even when provided by the developer.

tobyhinloopen2• 7 months ago

Take it from a massive TypeScript nerd: JSDoc is not an anti-TypeScript position to take. It is the same powerful static analysis without the build step.

Ahum https://nodejs.org/en/learn/typescript/run-natively

eevilspock• 7 months ago

that's limited to node. won't work in a browser.

tobyhinloopen2• 7 months ago

Oh right I forgot Javascript also runs in a browser

spoiler2• 7 months ago

Technically there's still a build step happening under the hood! But another benefit of shifting TS into JSDoc comments is that it also works in browsers. That being said, while I understand the aversion to unnecessary complexity, I'm personally fine with a build step to remove TS. It's a much nicer syntax IMO. And with tools like `swc` for type stripping, it's pretty snappy too.

w3news• 7 months ago

Thanks, I use JSDoc for several years, and also validate it with Typescript. So I just write plain Javascript with JSDoc, with no build step. Typescript only validates the types, and not transforming the code. Did you also know that you can import Typescript types/interfaces in JSDoc? So for me typescript is not a language anymore, I use only the tool to validate the types.

Best thing for me was not removing the code transformation (convert ts to js), but separate runtime code with documentation code, like the types. Gives you much more clear insight that the types you write to describe what you expect the type will be is not forced on runtime, but is just for you as developer to know it. And when you validate the input is the right type, it is much more clear that it is the runtime type validation.

You can still use JSDoc in your typescript files, but why do you want to do that? There is no reason to do that.

So using JSDoc or Type Annotation, both works the same, same benefits, it is only personal preferences. Both have its pros and cons. For me the JSDoc has more benefits. Some other people prefer annotations. But there is not 1 that is better in controlling the types, has more options. (Also the enum can be done if you are using JSDoc, but is a little different)

supernes• 7 months ago

You can still use JSDoc in your typescript files, but why do you want to do that?

JSDoc is more than type annotations. I use it for method and parameter descriptions, deprecation notices, inline examples, etc even in TS files.

Hrun0• 7 months ago

I’m surprised TypeScript is controversial to some people. Having worked on a large vanilla JavaScript framework, the benefits were pretty clear.

embedding-shape5• 7 months ago

Many of us don't encounter the sort of problems Typescript offers to solve. As most programming languages, most of the bugs I create when using JS is logic bugs, and those are solves by unit testing, not "more types". It was a long time ago I managed to push broken frontend code because of assuming the wrong types, so personally I don't find TS that valuable. But obviously others seem severely impacted by those types of issues, otherwise TS wouldn't be so popular in the first place. People be different :shrug:

culi29• 7 months ago

Myself and this post are also pro-TypeScript!

Merad• 7 months ago

Can you perform type checking with JSDoc? As in, run type checks in CI/CD, commit hooks, etc?

matt_kantor10• 7 months ago

Yes. As described in the article, the TypeScript compiler understands type annotations that are written in JSDoc syntax. So you can use `tsc`, just like you would to check `.ts` files.

columk• 7 months ago

To address point 2 you can enable the VSCode setting: "TypeScript: Prefer Go To Source Definition".

If it's your own library you can add declarationMap: true to your tsconfig.

I almost always want to see the source when I cmd+click.

hilarycheng• 7 months ago

JSDoc is great. But remember, JSDoc is used for well trained developer. For those junior programmer, they will totally ignore it and write lots of shxt code. At least TypeScript can force them to use correct type like forcing them not to use "any" type.

braebo• 7 months ago

JSDoc is ugly, clumsy, and leads to worse types on average over time. Typescript can be executed directly these days just use Bun and build steps are instant.

JSDoc is TypeScript

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