“ …esbuild has built-in support for parsing TypeScript syntax and discarding the type annotations.”.
Type discarding bundlers are used to accelerate the feedback loop that otherwise would be significantly slower if they were limited to using tsc—especially in large code bases.
Relying on TypeScript specific features (e.g. decorators) essentially blocks that build time optimization.
Using non-JavaScript TypeScript features comes with significant tradeoffs. By and large TypeScript is being used as a JavaScript type linter, either with it's own “more convenient” syntax or in combination with JSDoc.
Using TypeScript as a “language” presents it's own risk.
“ …esbuild has built-in support for parsing TypeScript syntax and discarding the type annotations.”.
The point being? I could not infer.
Type discarding bundlers are used to accelerate the feedback loop that otherwise would be significantly slower if they were limited to using tsc—especially in large code bases.
I completely agree. However, tsc !== TypeScript. The compiler of choice is not the language itself. The language still carries many benefits, regardless of the compiler/transpiler of choice. So I guess I continue to miss your point.
Regarding build times: Yes, using TypeScript adds a "transpilation/compilation" step to the CI/CD. But how much are we talking about? Does anybody have benchmarks lying around?
… TypeScript is being used as a JavaScript type linter [not as a compile-to-JS language].
step to the CI/CD.
I'm not talking about CI/CD. I'm talking about during normal development and/or micro testing; development approximating REPL-driven programming (… a set of tools and practices for programming that emphasize fast and rich feedback). It allows you to bypass many specious TS-errors until you are ready to address them in earnest and run a «full blown» type check, not just stripping the type annotations.
Ok, I saw the video. OMG. Is people like this now? In the video:
TypeScript is a linter because it produces JS.
Is C# a linter because it produces MSIL? OMG. Clearly this person and anyone that backs him up has lost the depth in their train of thought. Pretty much the entire video should be deleted.
People reading this: Did you know that before C, languages were untyped? Do you know how types are really used by compilers? My guess is No, you don't know because you keep minimizing the importance of types. I'll leave this as homework assignment to you all, avid followers of the "kill TypeScript because typing is linting" movement.
I'm talking about during normal development and/or micro testing;
This already exists and TypeScript does not interfere with it. Literally every Vite + TS + <Technology> project uses esbuild to provide this experience. Is TypeScript getting in the way of this? How? When? Where? I don't see the relation between TypeScript and the inability to have REPL-like development experiences. It sounds to me that people are thinking tsc to be mandatory when using TypeScript. Is not.
I don't see the relation between TypeScript and the inability to have REPL-like development experiences.
The (lack of) type checking speed of tsc. Nobody uses anything else for type checking as all the alternatives strictly strip but do not type check (and perhaps even transform).
As I alluded to before, TypeScript was never about type safety, it's about “somewhat safer types as long as it doesn't cause the developer any additional effort”— i.e. developer convenience first.
It has always been my contention that people who care about types would use something more like ReScript rather than TypeScript and simply accept the burden of managing JS interoperability. TypeScript makes many (permanent) compromises in order to allow progressive adoption on a JS code base and to consume pure-JS libraries.
"kill TypeScript because typing is linting" movement.
It's too far gone for that. Again: TypeScript's popularity has nothing to do with types but everything to do with developer convenience via Intellisense. Accepting anything else is just being in denial.
“Note that Vite only performs transpilation on .ts files and does NOT perform type checking. It assumes type checking is taken care of by your IDE and build process.”
Vite achieves it's level of experience by bypassing the type checking stage entirely. Most of the time people just fix the issues as they see them in their editor via LSP. Then in CI/CD tsc -noEmit is used to catch any errors that may have been missed.
The (lack of) type checking speed of tsc. Nobody uses anything else for type checking as all the alternatives strictly strip but do not type check (and perhaps even transform).
Ok, but this is tsc, the compiler, notTypeScript, the language.
It's too far gone for that. Again: TypeScript's popularity has nothing to do with types but everything to do with developer convenience via intellisense. Accepting anything else is being in denial.
Intellisense is the live reflection of the compiler. Wanting this live reflection is nothing to be ashamed of. To say that you "want Intellisense but not compilation" is impossible, as Intellisense is completely predicated in the compiliation process.
Vite achieves it's level of experience by bypassing the type checking stage entirely.
Yes, and there's nothing wrong with that. You, as a developer, should be fully aware of this. You, as a developer, once you are happy with your product, should then kick off the TS compiler to ensure your project is error-free. You, as a developer, should include TS compilation in CI/CD as well. How does any of this preventing REPL-like experiences?? The concept of TS somehow getting in the way simply escapes me. Because most people don't do it properly, then it is TypeScript's fault and must be stopped? Or are people saying that this is "a bad thing" because somehow compilation should be in every single scenario every second of the way or not exist at all? That would also be non-sense to me.
Ok, but this is tsc, the compiler, not TypeScript, the language.
Some would argue that tsc isn't a compiler in the original sense.
In the early days of C++, Cfront was identified as a cross-compiler largely because it did not change the granularity/level of it's output―it performed a code transformation but stayed on the same high level of language. Later the term transpiler was coined for transforming-compiler underlining that the transformed output wasn't operating at a finer granularity (e.g. assembler).
Given that it is possible to just strip the TypeScript annotations with minimal transformation, TypeScript is just a tsc syntax for JavaScript rather than a language. Admittedly TS JSDoc would have been the more authentic solution but that would have never gained any widespread adoption because it would have been too inconvenient for application developers.
TypeScript has always been squarely targeted at application developers rather than library authors which always had other ways of providing the “types” to support their users development environment's code completion:
“TypeScript began its life as an attempt to bring traditional object-oriented types to JavaScript so that the programmers at Microsoft could bring traditional object-oriented programs to the web. As it has developed, TypeScript’s type system has evolved to model code written by native JavaScripters. The resulting system is powerful, interesting and messy.”
should then kick off the TS compiler to ensure your project is error-free.
It emphasizes how TypeScript is just lipstick on JavaScript.
This is so harsh! Made me laugh. 😄
Ok, so this feud is making my head spin. On one side, there is people saying TypeScript should not exist. On the other, there's people like me saying TypeScript provides value. The main issue is that people whine about their source code being more difficult to maintain for something that gives them nothing. Am I correct so far? If yes, these people say that, because of its alleged zero value it should not exist. This is the overall view.
Now, especifically:
TypeScript compilation is just linting because it brings nothing to the table.
TypeScript compilation precludes or "soils" the REPL-like experience.
I think we can agree that #2 is false. Let's see about #1.
One of the things that I like the most of TypeScript because I can state the data types, is catching missing logic. A very simplified example:
Because I can specify the data types, both Intellisense and the transpilation step (tsc) will tell me that I forgot the fact that value could be undefined.
TypeScript compilation precludes or "soils" the REPL-like experience.
I think we can agree that #2 is false.
I don't see how. Starting with TypeScript the REPL-like experience can only be realized by using a type stripper. There is no --transpileOnly flag in tsc so the type checking (executing in a JS runtime) bogs the feedback cycle down. The only other way to bypass tsc is to write plain JavaScript an annotate it with TS types inside JSDoc annotations.
Aside:
Nobody is going to argue that React isn't “popular” (whatever else one might think of it). React isn't developed with TypeScript. The DefinitelyTyped types are maintained by the React team but React itself is typed with Flow. AFAIK Flow was developed with OCaml which is fairly popular with compiler writers because it's binary execution speeds are "close to a compiler written in plain C". It stands to reason that Flow never had the tsc speed issues so it never slowed the React team's development flow.
Many people prefer Flow over TypeScript however Flow never caught on, perhaps because MS Windows wasn't supported until late 2016 by which time DefinitelyTyped was already firmly established and now the Angular 2 release further increased general interest in TypeScript.
In some ways one could say that TypeScript is more a product of a "productivity culture" while Flow seems to lean more towards the outcome of an "engineering culture" (though I would classify React itself as a product designed for a "productivity culture").
Am I correct so far?
People value TypeScript for the developer convenience it provides in their development environment, primarily VSCode (or any other LSP supporting environment).
Library authors requiring strict control over the runtime JavaScript code (for whatever reason) elect to use TS JSDoc primarily to deliver consistent TypeScript types for their users, with the side benefit of (only) on demand tsc static type analysis.
Do linters do this?
Linters in the original sense no.
But in the web dev world the concept of static analysis tools for dynamic languages was virtually unheard of (example Erlang: dialyzer; Elixir: dialyxir).
Flow had the right idea: be a static analysis tool that supports an inline type syntax and be fast enough to never get in the way.
TypeScript started with ambitions to be a language but the enum fiasco just drives the home the point that deviating from the JavaScript baseline only comes back to haunt (and hurt) TypeScript.
So in the web dev world static analysis tools were explained as "type linters".
Ok, I see that you are incapable of admitting that tsc !== TypeScript, which makes you repeat over and over the idea that esbuild is a "trash remover". I guess we will just have to agree to disagree. REPL-like experiences are possible today for TypeScript-powered projects, whether you want to admit it or not. TypeScript is in no way an impediment to this.
Furthermore, I have demonstrated fully that TypeScript does bring value to the table using a 3-line example. I have fully demonstrated what probably is the greatest benefit of this language. Whether or not you want to admit it, is again, up to you.
I believe I'll just let other people reading this judge for themselves. I will end my participation here saying: Make your own minds. Always be critical to what you hear and read. I personally think this whole movement has no reason to be, and that TypeScript is an invaluable asset that helps developers produce better code faster.
I have demonstrated fully that TypeScript does bring value to the table using a 3-line example.
Value that can be delivered with static type analysis alone. No language required.
The point is that Flow delivers exactly the same value, according to some people at a higher level of quality, without proclaiming itself as a language but simply as a “static type checker”.
So:
Betting on TypeScript tooling as a static type checker (TS-as-a-devtool) is where the current value is.
Using it as a language is risky especially for features that are not on the current list of TC39 proposals.
Ok, so clearly you want to continue arguing. The problem I have, and I say this without trying to be antagonist, is that you are like Alexa:
Me: "Alexa, isn't this a TypeScript-exclusive feature?"
Alexa: "Facebook uses Flow for type checking."
If you can actually stay on topic, I'll be glad to continue the discussion. If you, however, are incapable of reasoning within the boundaries of the topic, I'll just make myself scarce. I am not, and will not be, diverted by off-topic subjects. I am also not interested in other people's words. I'm interested in your own and my own. We are the ones in this discussion, not others. All your quoting is irrelevant to me because I make my own mind and not comply with others just because of their alleged reputations.
I'll start: I love, as many of us do, VS Code. Flow and VS Code are not a thing. Therefore, it is not going to be a thing for us to move to Flow. Let's just drop Flow. Let's talk about things that could actually happen.
Let's discuss the very important matter: TypeScript exists, is a language and comes with tsc from Microsoft. tsc is not very performant. Is this a "language" feature? It is not. Why? Anyone could make a better transpiler and the language itself would be unaffected. Agreed? If yes, you must also agree by extension, that tsc !== TypeScript. Yes? No? Discuss, but stay on topic. I am not interested in stories about the history of pictographic communications in caves found in the Middle East that date from 15.000 BC.
Ok, yes. I see your point more clearly now. Because JsDoc goes into comments, there's no stripping to do. That is most certainly a clear advantage, probably the greatest advantage over TypeScript, no doubt.
So, we have two options for type safety: One that uses comments, and one that doesn't, and people say the latter can go away. I guess it is only logical. Unless, that is, that TypeScript (the latter) has something else in its favor, and there is.
TypeScript can bring new JavaScript features to life faster. Yes, you have already argued about how that could be problematic. Still, it is a feature that only TypeScript provides. I believe in the democratic process of every developer to choose their tooling, and I truly believe that this is one of those cases. It is no small thing, in my opinion. Yes, there will be people that say this doesn't justify the grievances of transpiling. I get that.
At this point, I must admit you have me half-convinced. See? All that ranting about Flow and all those quoting got you nowhere with me, but your succinct demonstration got me thinking!
I could probably ask you about the capabilities of JsDoc, but I suppose that I should just investigate that on my own to determine whether or not I should opt for JsDoc. For example, it is very difficult for me (or impossible, really) to imagine I can define the types I need for an entire project with just comments. I am a back-end developer, so my experience with JavaScript is not very extensive. My main concern right now is: Can I define the data models of an entire application in JsDoc, centrally in one location and use the definitions in the rest of the project?
UPDATE: Question: Is JsDoc a thing by itself? Or must it always piggyback ride on TypeScript? I must confess I'm confused about this topic for the first time. I am concluding that in VS Code all that is needed is the language server. If this is true, and JsDoc can provide an alternative to at least most of TypeScript features, it is something I must learn ASAP. The one thing that would seriously worry me is not having a CI/CD method of making sure developers did their work of honoring all of the Intellisense feedback.
This thread is quite interesting.
Here is my personal opinion, TypeScript is definitely prone to adding aggressive syntax sugar due to its compilation-based nature.
And these are a kind of auto code.
However, the basic JS syntax has been sufficient since ES6.
Some features may require polyfills, but if you only use the basic JavaScript syntax, TypeScript will simply perform type checking, which means that you don't even need to copy my source code from the src folder to the dist folder.
Of course, TypeScript provides a watch feature, so in many cases these limitations will not be felt significantly. But it's not zero.
Perhaps the biggest advantage of JSDoc is that you can see the actual implementation code using VSCE's ctrl + left click while using the library.
This is not possible with js or compiled ts.
Perhaps the JSDoc example in my Stackblitz will answer your questions.
Yes but the intent is only to document, not type check (e.g. like Doxygen).
Or must it always piggyback ride on TypeScript?
That is why I go out of my way to use the term TS JSDoc when referring to applying TypeScript types to JavaScript code via JSDoc. I suppose the choice of using JSDoc was influenced by the fact that Google's Closure Compiler already used JSDoc to carry type hints.
I must confess I'm confused about this topic for the first time.
A large segment of the TS user community is. Back in May it became very clear that many did not understand the tool chain they work with day-to-day when there was a social media uproar against SvelteKit moving to JSDoc when in fact the team:
wasn't giving up type checking (they were just moving it later into the development workflow)
was still going to supply their user community with verified TypeScript types.
I am concluding that in VS Code all that is needed is the language server.
It is the defacto choice but lots of editors/IDEs are capable of supporting the language server protocol (IntelliJ WebStorm, neo/vim, etc.).
If this is true, and JsDoc can provide an alternative to at least most of TypeScript features, it is something I must learn ASAP.
Be advised, in my experience using TS JSDoc effectively requires a higher level of tooling knowledge/competence than just using TS syntax in an LSP supported editor. So typically it makes sense to spend ones time first with the pure TS syntax because it (at least on the surface) seems more familiar coming from the likes of C#/Java.
But TypeScript's type manipulation syntax (and the way it extracts information from value space into type space) can take some time getting used to.
That isn't to say the TS JSDoc isn't without its annoyances.
Many simply prefer their types conflated with the implementation because that is what they are familiar with from other languages (Haskell/Elm converted me to separating types from implementation) and they resent having to type more (Typing is not a programming bottleneck).
Having to juggle between undefined and void in the type declarations until it finally works is tedious (tsc seems to randomly shallow undefined from sum types otherwise). And in case you didn't notice I couldn't get value ?? 1 to type check in your example leading me to use value ? value : 1 instead; so you are sometimes forced to write your code a certain way for the type checking to work as intended.
would seriously worry me is not having a CI/CD method
That is what tsc -noEmit is used for. For whole project type checking there is no way to get around tsc right now but if it is confined to CI/CD it isn't a big issue.
For example, it is very difficult for me (or impossible, really) to imagine I can define the types I need for an entire project with just comments.
In practice you don't.
You will still have *.ts files (see this comment) to hold shared or complex types but only for declaring types or extracting type information from JS files (another complaint against TS JSDoc is the frequent separation of TS types and JS implementation 🤷). In JS files you can import these types for reference.
Can I define the data models of an entire application in JsDoc, centrally in one location and use the definitions in the rest of the project.
You could simply define all the types with TypeScript syntax in *.ts files and just import those types into the JS files.
I am a back-end developer
The thing is in back-end code there is little incentive to use TS JSDoc (just stick to writing a JavaScript with types TS flavour to be on the safe side). It can be useful when you identify code on the hot path that is less than optimal (due to the TS transform) allowing you to take direct control over the exact JS runtime code.
Using JS can be a lot more critical on front end packages where either size matters or where the TypeScript syntax creates a barrier to using a certain parser for some niche code analysis tool or bespoke compiler.
This thread of argumentation has really piqued my interest. I am already well aware of tsserver's built-in support for JSDoc annotations, but you have convinced me to more seriously consider it as a means to further minimize the TypeScript surface in my project (particularly for very simple type annotations in function parameters). More complex typings would, of course, still remain in .ts files, but I am quite attracted to the idea of moving more TypeScript syntax into JSDoc instead.
This is not to say that TypeScript is evil. I intend to minimize the TypeScript surface to better emphasize the sufficiency of language semantics when it comes to .js files—specifically the OCaml-like assertion that "pure type inference is sufficient".
ngl TS JSDoc can be a bit painful, especially in the beginning and too painful for many to even stick with it for any length of time, mostly because esbuild sidelined the constant need for tsc anyway.
That said with TS JSDoc your premise becomes “JavaScript first, then Types”.
I'd say it's only painful when trying to jam a bunch of TypeScript syntax into it. At that point, we may as well just use TypeScript for that, which is syntactically superior over the hacky shoehorning of TypeScript syntax into JavaScript comments. For simpler annotations of function parameters, however, TS JSDoc is fine with me.
That said with TS JSDoc your premise becomes “JavaScript first, then Types”.
You know, this is actually pretty good. Perhaps that is my ultimate end goal. 🤔
Thank you, @peerreynders for the details. So we are kind in the middle of things where there is no definite alternative to TypeScript.
My take from your explanation is, and correct any details if I miss any:
JsDoc is dependant on TypeScript, and that's why you refer to the solution as "TS JsDoc".
JsDoc cannot be used to document an entire project, so .d.ts files are still needed.
There is no alternative in the CI/CD: tsc is king right now in this arena.
If we can, we can maximize REPL-like experiences by avoiding TS in web projects. Not that it is super bad right now, since esbuild does a tremendous job of transpiling TS code. It just doesn't type-check.
I guess, then, that fighting over TypeScript at this point in time is of no consequence: There's no alternative. There should be no feud until the day comes where an alternative is available. Then we can be at each others' throats. 😄
JsDoc cannot be used to document an entire project, so .d.ts files are still needed.
In a TS JSDoc project *.d.ts and *.ts play different roles:
The project consumes *.d.ts files that provide the missing type information for dependencies, either supplied or DIY (handwritten types).
The project declares it's (internal and) published types in any number of *.ts files.
tsc can then be configured to output a *.d.ts for consumers of the project
There should be no feud
There is no feud. Just a case of many TS developers dismissing TS JSDoc out hand mostly based on developer convenience, additional learning curve and confusion about the difference between JSDoc and TS JSDoc.
@peerreynders I think you make some fair points about TS, but your comparison between dialyzer and TS is entirely a reach. First of all, dialyzer gives you some type safety to Erlang but doesn't extend the language, nor does it let you annotate or operate on types (the language already does that). A fairer comparison would be between Liquid Haskell and TS. Because both are extensions to the language, they are not just a "fancy linter" but an actual extension of the language. That is the case because Typescript enhances Javascript not just with type-safety but with the ability to annotate types and also with features that let you catch another whole class of type errors using, for instance, dependent types. But even if there were no dependent types, TS brings the benefits of a fully-fledged type system because that is what TS is, i.e., a programming language with a static type system.
I understand your argument revolves around typescript's main focus, not being type safety but developer convenience. Although it is a valid point, it's a partial truth. Typescript chose to have unsoundness to make its adoption more accessible, but no language is entirely sound. For example, Haskell is unsound concerning FFI and undefined, or C# is unsound concerning null or typecasting. Thus, it is better to talk of soundness for a set of runtime type errors. In that sense, a language can be more type-safe than others, or in other words, it can be more sound than others, but that doesn't mean the lesser one does not have type-safety. So, type-safety is a critical characteristic that Typescript brings to the table. Still, you have to be extra careful when using its unsound aspects (as in other type-safe languages).
Finally, though you bring up some valid points, I think saying TS is not its language (like Rescript, Purescript, ELM, etc...) is missing the main point of why one should use (TS, Hegel, and Flow) and their difference to JSDocs or a linter.
UPDATE
To be fair, I am being a bit hyperbolic about dialyzer and TS; I think those tools are comparable regarding type checking, although they serve different purposes. But the main point is that a linter does not extend the capability of the language, which is why not every type-checker is a linter.
your comparison between dialyzer and TS is entirely a reach.
It was made to reinforce the idea of using TS tooling for the purpose of static analysis in reference to this tweet, i.e. TS-as-a-devtool rather than TS-as-a-language.
linter does not extend the capability of the language,
In what way does TypeScript extend the capability of JavaScript? JavaScript can be used in ways that can't be statically typed in TypeScript (the point of The Trouble with TypeScript). TypeScript may be a superset to JavaScript in terms of developer features but TypeScript can only express a subset of all valid JavaScript code.
I think saying TS is not its language is missing the main point of why one should use and their difference to JSDocs or a linter.
The discussion was around the primarily value proposition behind the TS tooling ecosystem. In particular:
Betting on TypeScript tooling as a static type checker (TS-as-a-devtool) is where the current value is.
Using it as a language is risky especially for features that are not on the current list of TC39 proposals.
Leveraging TS language features that aren't (soon becoming) standard in JS can easily make portions of that ecosystem inaccessible. The example I chose:
Relying on TypeScript specific features (e.g. decorators) essentially blocks that build time optimization.
“The solution was to get a plugin that negated all of the performance gained by ignoring TypeScript. The plugin runs each typescript file through tsc before passing it to esbuild.”
Once one accepts that the primary value of TS comes from adding types to JavaScript the next step is to acknowledge that the same benefit can be derived (albeit with a bit more pain) by simply using JavaScript and augmenting it with TS types via JSDoc (which is different from JSDoc for documentation).
In the past few months a lot of the "you can't do this with TS JSDoc" statements have been proven wrong even though some of the solutions are ugly or downright flaky.
Preact switched to TS JSDoc ~2020 and SvelteKit in May 2023; so even if it's somewhat tedious it must cover all the bases.
It is this approach of using TS-as-a-devtool (rather than TS-as-a-language) that describes using TS as a "type linter" or more formally as a static analysis tool,
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The industry is moving away from that; esbuild → Content Types → TypeScript:
“ …esbuild has built-in support for parsing TypeScript syntax and discarding the type annotations.”.
Type discarding bundlers are used to accelerate the feedback loop that otherwise would be significantly slower if they were limited to using
tsc—especially in large code bases.Relying on TypeScript specific features (e.g. decorators) essentially blocks that build time optimization.
Using non-JavaScript TypeScript features comes with significant tradeoffs. By and large TypeScript is being used as a JavaScript type linter, either with it's own “more convenient” syntax or in combination with JSDoc.
Using TypeScript as a “language” presents it's own risk.
The point being? I could not infer.
I completely agree. However,
tsc !== TypeScript. The compiler of choice is not the language itself. The language still carries many benefits, regardless of the compiler/transpiler of choice. So I guess I continue to miss your point.Regarding build times: Yes, using TypeScript adds a "transpilation/compilation" step to the CI/CD. But how much are we talking about? Does anybody have benchmarks lying around?
… TypeScript is being used as a JavaScript type linter [not as a compile-to-JS language].
I'm not talking about CI/CD. I'm talking about during normal development and/or micro testing; development approximating REPL-driven programming (… a set of tools and practices for programming that emphasize fast and rich feedback). It allows you to bypass many specious TS-errors until you are ready to address them in earnest and run a «full blown» type check, not just stripping the type annotations.
“I often wish I worked in a language where I could start dynamic and end statically”
Ok, I saw the video. OMG. Is people like this now? In the video:
Is C# a linter because it produces MSIL? OMG. Clearly this person and anyone that backs him up has lost the depth in their train of thought. Pretty much the entire video should be deleted.
People reading this: Did you know that before C, languages were untyped? Do you know how types are really used by compilers? My guess is No, you don't know because you keep minimizing the importance of types. I'll leave this as homework assignment to you all, avid followers of the "kill TypeScript because typing is linting" movement.
This already exists and TypeScript does not interfere with it. Literally every
Vite + TS + <Technology>project uses esbuild to provide this experience. Is TypeScript getting in the way of this? How? When? Where? I don't see the relation between TypeScript and the inability to have REPL-like development experiences. It sounds to me that people are thinkingtscto be mandatory when using TypeScript. Is not.The (lack of) type checking speed of
tsc. Nobody uses anything else for type checking as all the alternatives strictly strip but do not type check (and perhaps even transform).As I alluded to before, TypeScript was never about type safety, it's about “somewhat safer types as long as it doesn't cause the developer any additional effort”— i.e. developer convenience first.
It has always been my contention that people who care about types would use something more like ReScript rather than TypeScript and simply accept the burden of managing JS interoperability. TypeScript makes many (permanent) compromises in order to allow progressive adoption on a JS code base and to consume pure-JS libraries.
It's too far gone for that. Again: TypeScript's popularity has nothing to do with types but everything to do with developer convenience via Intellisense. Accepting anything else is just being in denial.
Please read the documentation:
“Note that Vite only performs transpilation on
.tsfiles and does NOT perform type checking. It assumes type checking is taken care of by your IDE and build process.”Vite achieves it's level of experience by bypassing the type checking stage entirely. Most of the time people just fix the issues as they see them in their editor via LSP. Then in CI/CD
tsc -noEmitis used to catch any errors that may have been missed.PS: Deno skips type checking by default as well.
Ok, but this is
tsc, the compiler, notTypeScript, the language.Intellisense is the live reflection of the compiler. Wanting this live reflection is nothing to be ashamed of. To say that you "want Intellisense but not compilation" is impossible, as Intellisense is completely predicated in the compiliation process.
Yes, and there's nothing wrong with that. You, as a developer, should be fully aware of this. You, as a developer, once you are happy with your product, should then kick off the TS compiler to ensure your project is error-free. You, as a developer, should include TS compilation in CI/CD as well. How does any of this preventing REPL-like experiences?? The concept of TS somehow getting in the way simply escapes me. Because most people don't do it properly, then it is TypeScript's fault and must be stopped? Or are people saying that this is "a bad thing" because somehow compilation should be in every single scenario every second of the way or not exist at all? That would also be non-sense to me.
So?
Some would argue that
tscisn't a compiler in the original sense.In the early days of C++, Cfront was identified as a cross-compiler largely because it did not change the granularity/level of it's output―it performed a code transformation but stayed on the same high level of language. Later the term transpiler was coined for transforming-compiler underlining that the transformed output wasn't operating at a finer granularity (e.g. assembler).
Given that it is possible to just strip the TypeScript annotations with minimal transformation, TypeScript is just a
tscsyntax for JavaScript rather than a language. Admittedly TS JSDoc would have been the more authentic solution but that would have never gained any widespread adoption because it would have been too inconvenient for application developers.TypeScript has always been squarely targeted at application developers rather than library authors which always had other ways of providing the “types” to support their users development environment's code completion:
“TypeScript began its life as an attempt to bring traditional object-oriented types to JavaScript so that the programmers at Microsoft could bring traditional object-oriented programs to the web. As it has developed, TypeScript’s type system has evolved to model code written by native JavaScripters. The resulting system is powerful, interesting and messy.”
This is the step that is considered "type linting" (aka static type analysis/checking).
It emphasizes how TypeScript is just lipstick on JavaScript.
This is so harsh! Made me laugh. 😄
Ok, so this feud is making my head spin. On one side, there is people saying TypeScript should not exist. On the other, there's people like me saying TypeScript provides value. The main issue is that people whine about their source code being more difficult to maintain for something that gives them nothing. Am I correct so far? If yes, these people say that, because of its alleged zero value it should not exist. This is the overall view.
Now, especifically:
I think we can agree that #2 is false. Let's see about #1.
One of the things that I like the most of TypeScript because I can state the data types, is catching missing logic. A very simplified example:
Because I can specify the data types, both Intellisense and the transpilation step (
tsc) will tell me that I forgot the fact thatvaluecould beundefined.This makes me correct my code to:
Do linters do this? Is this kind of feature available in eslint? Or is it something that only TypeScript can do?
I don't see how. Starting with TypeScript the REPL-like experience can only be realized by using a type stripper. There is no
--transpileOnlyflag intscso the type checking (executing in a JS runtime) bogs the feedback cycle down. The only other way to bypasstscis to write plain JavaScript an annotate it with TS types inside JSDoc annotations.Aside:
Nobody is going to argue that React isn't “popular” (whatever else one might think of it). React isn't developed with TypeScript. The DefinitelyTyped types are maintained by the React team but React itself is typed with Flow. AFAIK Flow was developed with OCaml which is fairly popular with compiler writers because it's binary execution speeds are "close to a compiler written in plain C". It stands to reason that Flow never had the
tscspeed issues so it never slowed the React team's development flow.Many people prefer Flow over TypeScript however Flow never caught on, perhaps because MS Windows wasn't supported until late 2016 by which time DefinitelyTyped was already firmly established and now the Angular 2 release further increased general interest in TypeScript.
In some ways one could say that TypeScript is more a product of a "productivity culture" while Flow seems to lean more towards the outcome of an "engineering culture" (though I would classify React itself as a product designed for a "productivity culture").
People value TypeScript for the developer convenience it provides in their development environment, primarily VSCode (or any other LSP supporting environment).
People valuing reliable static type analysis have to look elsewhere.
Library authors requiring strict control over the runtime JavaScript code (for whatever reason) elect to use TS JSDoc primarily to deliver consistent TypeScript types for their users, with the side benefit of (only) on demand
tscstatic type analysis.Linters in the original sense no.
But in the web dev world the concept of static analysis tools for dynamic languages was virtually unheard of (example Erlang: dialyzer; Elixir: dialyxir).
Flow had the right idea: be a static analysis tool that supports an inline type syntax and be fast enough to never get in the way.
TypeScript started with ambitions to be a language but the enum fiasco just drives the home the point that deviating from the JavaScript baseline only comes back to haunt (and hurt) TypeScript.
So in the web dev world static analysis tools were explained as "type linters".
Ok, I see that you are incapable of admitting that
tsc !== TypeScript, which makes you repeat over and over the idea that esbuild is a "trash remover". I guess we will just have to agree to disagree. REPL-like experiences are possible today for TypeScript-powered projects, whether you want to admit it or not. TypeScript is in no way an impediment to this.Furthermore, I have demonstrated fully that TypeScript does bring value to the table using a 3-line example. I have fully demonstrated what probably is the greatest benefit of this language. Whether or not you want to admit it, is again, up to you.
I believe I'll just let other people reading this judge for themselves. I will end my participation here saying: Make your own minds. Always be critical to what you hear and read. I personally think this whole movement has no reason to be, and that TypeScript is an invaluable asset that helps developers produce better code faster.
Value that can be delivered with static type analysis alone. No language required.
The point is that Flow delivers exactly the same value, according to some people at a higher level of quality, without proclaiming itself as a language but simply as a “static type checker”.
So:
Betting on TypeScript tooling as a static type checker (TS-as-a-devtool) is where the current value is.
Using it as a language is risky especially for features that are not on the current list of TC39 proposals.
Ok, so clearly you want to continue arguing. The problem I have, and I say this without trying to be antagonist, is that you are like Alexa:
If you can actually stay on topic, I'll be glad to continue the discussion. If you, however, are incapable of reasoning within the boundaries of the topic, I'll just make myself scarce. I am not, and will not be, diverted by off-topic subjects. I am also not interested in other people's words. I'm interested in your own and my own. We are the ones in this discussion, not others. All your quoting is irrelevant to me because I make my own mind and not comply with others just because of their alleged reputations.
I'll start: I love, as many of us do, VS Code. Flow and VS Code are not a thing. Therefore, it is not going to be a thing for us to move to Flow. Let's just drop Flow. Let's talk about things that could actually happen.
Let's discuss the very important matter: TypeScript exists, is a language and comes with
tscfrom Microsoft.tscis not very performant. Is this a "language" feature? It is not. Why? Anyone could make a better transpiler and the language itself would be unaffected. Agreed? If yes, you must also agree by extension, thattsc !== TypeScript. Yes? No? Discuss, but stay on topic. I am not interested in stories about the history of pictographic communications in caves found in the Middle East that date from 15.000 BC.Faster transpilers have already been delivered.
As far as I'm aware
tsc(and LSP) is the only tool capable of type checking the TypeScript syntax and nobody is working on changing that.And as to your example:
TS playground
tsc• variable declaration space
• type declaration space
Fixed:
Which just emphasizes again that TypeScript adoption/popularity is primarily about developer convenience rather than safe types.
Great! We are getting somewhere now. Tell me: Is the benefit coming from JsDoc, or Typescript enforcing JsDoc? Because in jsfiddle.net:
I get no feedback.
tscor LSP parse the type syntax inside the JSDoc annotation to fill in the "type space gaps" in the JavaScript code.tscor LSP determine whether the code type checks.Ok, yes. I see your point more clearly now. Because JsDoc goes into comments, there's no stripping to do. That is most certainly a clear advantage, probably the greatest advantage over TypeScript, no doubt.
So, we have two options for type safety: One that uses comments, and one that doesn't, and people say the latter can go away. I guess it is only logical. Unless, that is, that TypeScript (the latter) has something else in its favor, and there is.
TypeScript can bring new JavaScript features to life faster. Yes, you have already argued about how that could be problematic. Still, it is a feature that only TypeScript provides. I believe in the democratic process of every developer to choose their tooling, and I truly believe that this is one of those cases. It is no small thing, in my opinion. Yes, there will be people that say this doesn't justify the grievances of transpiling. I get that.
At this point, I must admit you have me half-convinced. See? All that ranting about Flow and all those quoting got you nowhere with me, but your succinct demonstration got me thinking!
I could probably ask you about the capabilities of JsDoc, but I suppose that I should just investigate that on my own to determine whether or not I should opt for JsDoc. For example, it is very difficult for me (or impossible, really) to imagine I can define the types I need for an entire project with just comments. I am a back-end developer, so my experience with JavaScript is not very extensive. My main concern right now is: Can I define the data models of an entire application in JsDoc, centrally in one location and use the definitions in the rest of the project?
UPDATE: Question: Is JsDoc a thing by itself? Or must it always piggyback ride on TypeScript? I must confess I'm confused about this topic for the first time. I am concluding that in VS Code all that is needed is the language server. If this is true, and JsDoc can provide an alternative to at least most of TypeScript features, it is something I must learn ASAP. The one thing that would seriously worry me is not having a CI/CD method of making sure developers did their work of honoring all of the Intellisense feedback.
This thread is quite interesting.
Here is my personal opinion, TypeScript is definitely prone to adding aggressive syntax sugar due to its compilation-based nature.
And these are a kind of auto code.
However, the basic JS syntax has been sufficient since ES6.
Some features may require polyfills, but if you only use the basic JavaScript syntax, TypeScript will simply perform type checking, which means that you don't even need to copy my source code from the src folder to the dist folder.
Of course, TypeScript provides a watch feature, so in many cases these limitations will not be felt significantly. But it's not zero.
Perhaps the biggest advantage of JSDoc is that you can see the actual implementation code using VSCE's ctrl + left click while using the library.
This is not possible with js or compiled ts.
Perhaps the JSDoc example in my Stackblitz will answer your questions.
Yes but the intent is only to document, not type check (e.g. like Doxygen).
That is why I go out of my way to use the term TS JSDoc when referring to applying TypeScript types to JavaScript code via JSDoc. I suppose the choice of using JSDoc was influenced by the fact that Google's Closure Compiler already used JSDoc to carry type hints.
A large segment of the TS user community is. Back in May it became very clear that many did not understand the tool chain they work with day-to-day when there was a social media uproar against SvelteKit moving to JSDoc when in fact the team:
It is the defacto choice but lots of editors/IDEs are capable of supporting the language server protocol (IntelliJ WebStorm, neo/vim, etc.).
Be advised, in my experience using TS JSDoc effectively requires a higher level of tooling knowledge/competence than just using TS syntax in an LSP supported editor. So typically it makes sense to spend ones time first with the pure TS syntax because it (at least on the surface) seems more familiar coming from the likes of C#/Java.
But TypeScript's type manipulation syntax (and the way it extracts information from value space into type space) can take some time getting used to.
That isn't to say the TS JSDoc isn't without its annoyances.
Many simply prefer their types conflated with the implementation because that is what they are familiar with from other languages (Haskell/Elm converted me to separating types from implementation) and they resent having to type more (Typing is not a programming bottleneck).
Having to juggle between
undefinedandvoidin the type declarations until it finally works is tedious (tscseems to randomly shallowundefinedfrom sum types otherwise). And in case you didn't notice I couldn't getvalue ?? 1to type check in your example leading me to usevalue ? value : 1instead; so you are sometimes forced to write your code a certain way for the type checking to work as intended.That is what
tsc -noEmitis used for. For whole project type checking there is no way to get aroundtscright now but if it is confined to CI/CD it isn't a big issue.In practice you don't.
You will still have
*.tsfiles (see this comment) to hold shared or complex types but only for declaring types or extracting type information from JS files (another complaint against TS JSDoc is the frequent separation of TS types and JS implementation 🤷). In JS files you can import these types for reference.You could simply define all the types with TypeScript syntax in *.ts files and just import those types into the JS files.
The thing is in back-end code there is little incentive to use TS JSDoc (just stick to writing a JavaScript with types TS flavour to be on the safe side). It can be useful when you identify code on the hot path that is less than optimal (due to the TS transform) allowing you to take direct control over the exact JS runtime code.
Using JS can be a lot more critical on front end packages where either size matters or where the TypeScript syntax creates a barrier to using a certain parser for some niche code analysis tool or bespoke compiler.
This thread of argumentation has really piqued my interest. I am already well aware of
tsserver's built-in support for JSDoc annotations, but you have convinced me to more seriously consider it as a means to further minimize the TypeScript surface in my project (particularly for very simple type annotations in function parameters). More complex typings would, of course, still remain in.tsfiles, but I am quite attracted to the idea of moving more TypeScript syntax into JSDoc instead.This is not to say that TypeScript is evil. I intend to minimize the TypeScript surface to better emphasize the sufficiency of language semantics when it comes to
.jsfiles—specifically the OCaml-like assertion that "pure type inference is sufficient".ngl TS JSDoc can be a bit painful, especially in the beginning and too painful for many to even stick with it for any length of time, mostly because esbuild sidelined the constant need for
tscanyway.That said with TS JSDoc your premise becomes “JavaScript first, then Types”.
I'd say it's only painful when trying to jam a bunch of TypeScript syntax into it. At that point, we may as well just use TypeScript for that, which is syntactically superior over the hacky shoehorning of TypeScript syntax into JavaScript comments. For simpler annotations of function parameters, however, TS JSDoc is fine with me.
You know, this is actually pretty good. Perhaps that is my ultimate end goal. 🤔
Thank you, @peerreynders for the details. So we are kind in the middle of things where there is no definite alternative to TypeScript.
My take from your explanation is, and correct any details if I miss any:
tscis king right now in this arena.I guess, then, that fighting over TypeScript at this point in time is of no consequence: There's no alternative. There should be no feud until the day comes where an alternative is available. Then we can be at each others' throats. 😄
In a TS JSDoc project *.d.ts and *.ts play different roles:
tsccan then be configured to output a *.d.ts for consumers of the projectThere is no feud. Just a case of many TS developers dismissing TS JSDoc out hand mostly based on developer convenience, additional learning curve and confusion about the difference between JSDoc and TS JSDoc.
@peerreynders I think you make some fair points about TS, but your comparison between dialyzer and TS is entirely a reach. First of all, dialyzer gives you some type safety to Erlang but doesn't extend the language, nor does it let you annotate or operate on types (the language already does that). A fairer comparison would be between Liquid Haskell and TS. Because both are extensions to the language, they are not just a "fancy linter" but an actual extension of the language. That is the case because Typescript enhances Javascript not just with type-safety but with the ability to annotate types and also with features that let you catch another whole class of type errors using, for instance, dependent types. But even if there were no dependent types, TS brings the benefits of a fully-fledged type system because that is what TS is, i.e., a programming language with a static type system.
I understand your argument revolves around typescript's main focus, not being type safety but developer convenience. Although it is a valid point, it's a partial truth. Typescript chose to have unsoundness to make its adoption more accessible, but no language is entirely sound. For example, Haskell is unsound concerning FFI and undefined, or C# is unsound concerning null or typecasting. Thus, it is better to talk of soundness for a set of runtime type errors. In that sense, a language can be more type-safe than others, or in other words, it can be more sound than others, but that doesn't mean the lesser one does not have type-safety. So, type-safety is a critical characteristic that Typescript brings to the table. Still, you have to be extra careful when using its unsound aspects (as in other type-safe languages).
Finally, though you bring up some valid points, I think saying TS is not its language (like Rescript, Purescript, ELM, etc...) is missing the main point of why one should use (TS, Hegel, and Flow) and their difference to JSDocs or a linter.
UPDATE
To be fair, I am being a bit hyperbolic about dialyzer and TS; I think those tools are comparable regarding type checking, although they serve different purposes. But the main point is that a linter does not extend the capability of the language, which is why not every type-checker is a linter.
It was made to reinforce the idea of using TS tooling for the purpose of static analysis in reference to this tweet, i.e. TS-as-a-devtool rather than TS-as-a-language.
In what way does TypeScript extend the capability of JavaScript? JavaScript can be used in ways that can't be statically typed in TypeScript (the point of The Trouble with TypeScript). TypeScript may be a superset to JavaScript in terms of developer features but TypeScript can only express a subset of all valid JavaScript code.
The discussion was around the primarily value proposition behind the TS tooling ecosystem. In particular:
Leveraging TS language features that aren't (soon becoming) standard in JS can easily make portions of that ecosystem inaccessible. The example I chose:
Using decorators would mean foregoing
esbuild(and therefore Vite) altogether or essentially crippling that development setup:“The solution was to get a plugin that negated all of the performance gained by ignoring TypeScript. The plugin runs each typescript file through
tscbefore passing it toesbuild.”Once one accepts that the primary value of TS comes from adding types to JavaScript the next step is to acknowledge that the same benefit can be derived (albeit with a bit more pain) by simply using JavaScript and augmenting it with TS types via JSDoc (which is different from JSDoc for documentation).
In the past few months a lot of the "you can't do this with TS JSDoc" statements have been proven wrong even though some of the solutions are ugly or downright flaky.
Preact switched to TS JSDoc ~2020 and SvelteKit in May 2023; so even if it's somewhat tedious it must cover all the bases.
It is this approach of using TS-as-a-devtool (rather than TS-as-a-language) that describes using TS as a "type linter" or more formally as a static analysis tool,