[smackeyacky]

I have been working with node for a couple of years now, not my choice but it isn’t tragic. This team uses TypeScript,

I honestly don’t get the problem TypeScript is trying to solve. JavaScript has lots of wacky problems but its main advantage to me was the loosy goosy approach to types. I was a smalltalk programmer back in the 1990s and it felt pretty comfortable if very primitive in the way of tools.

Typescript just seems unnecessary. Not sure why nobody built something like reentrent exceptions or cool stuff like that, instead they built a stupid jail that down compiles to unreadable sludge.

Now I find out there were competing jails. What a strange ecosystem.

[lucianbr]

How large are the projects you worked on? Usually type safety is more useful and appreciated in large projects, where strict interfaces between modules are more valuable. In small projects, the advantage is for the loosy-goosy, because you can move faster and anyway you have the whole thing in your head, or most of it.

There is a lot of text written and voice recorded over what type safety is good for. It's reasonable to disagree, but to "honestly don't get" what the point of it is seems kinda strange. Like you haven't really looked into it.

[mhh__]

I think the point isn't really about the value of type safety but rather the value-add of bothering with the whole of typescript (as in the type safety they provide rather than an abstract ideal) versus some other solution.

It's quite annoying IMO. Some of the things it can be infer are reasonably impressive but then that gets balanced out with having to write out a lot of crap that something a bit more HM-like would be able to nail immediately (rather than just "Any!? Fuck you").

That and the refusal to add other value-adds (despite being a compiler in all but name) hobbles the union types and so on.

[throwaway11460]

Could you give me some examples of this unnecessary code? Are you using type inference to its full capabilities? It's only really necessary to declare types at interfaces (function arguments, etc)... Is that what you're referring to?

[igouy]

"Type safety is the property that no primitive operation ever applies to values of the wrong type."

Smalltalk is type safe & not statically checked.

page 263 "Programming Languages: Application and Interpretation"

[pdf] https://cs.brown.edu/~sk/Publications/Books/ProgLangs/2007-0...

[ReflectedImage]

It's not really true that type safety is useful for large projects.

It's generally better to do proper micro-services.

Type safety is the inferior way of doing it where you get hit with a double whammy of long compile times and extreme code verbosity.

[zogrodea]

Network API contracts/documentation are just an attempt of type safety over the untyped network boundary.

Network communications are the most tedious and annoying part of programming for me because of the validation of the request body and checking that it has all the fields needed.

Microservices only increase the amount of documentation needed. I would prefer to lessen the amount of documentation by letting the compiler/code do the work instead.

[ReflectedImage]

No, it's forced modularity. It's saying there are hard lines between parts of your program that can't be crossed. This prevents the over time formation of spaghetti code.

It's like British tanks in WW2, your system is composed out of standard parts. Not necessary the best, but standard parts and that's what tends to be important.

[madeofpalk]

Maybe I'm just not as good of a developer as you, but I often fail to understand 100% of the codebase, or I even make mistakes sometimes. Having a system catch my back to tell me what else I need to update in my refactor is a huge help for me. Maybe that's just not a problem those 10x developers have?

> instead they built a stupid jail that down compiles to unreadable sludge

Does it? The Typescript compiler mostly just erases types, leaving the code otherwise the same. Here's a non-trival example https://tsplay.dev/mA078N, where the output is basically the same as the input, just with type syntax erased.

IIRC the only 'language feature' that Typescript actually compiles is enums, which is a bit of a big blob. There's compiler flags to 'fix' that, or you can just not use enums.

[pjc50]

> I was a smalltalk programmer back in the 1990s

Smalltalk (and languages in the same academic orbit, like LISP derivatives) seems to be a tool that fits a few people's hands very well, but there are no large smalltalk projects for two reasons:

- that doesn't actually suit most people, so it's harder to find developers

- the language maps well to one (1) human brain that keeps a model of what's happening, but that breaks down when larger teams of developers are involved.

I guess that keeps the "small" in smalltalk.

[igouy]

How do you know whether or not "there are no large smalltalk projects" (whether or not there have been large Smalltalk projects)?

Seems like we need do no more than assert: Yes there are!

~

But it's more interesting to look at how a real Smalltalk project worked:

"A very large Smalltalk application was developed at Cargill to support the operation of grain elevators and the associated commodity trading activities. The Smalltalk client application has 385 windows and over 5,000 classes. About 2,000 classes in this application interacted with an early (circa 1993) data access framework. The framework dynamically performed a mapping of object attributes to data table columns.

Analysis showed that although dynamic look up consumed 40% of the client execution time, it was unnecessary.

A new data layer interface was developed that required the business class to provide the object attribute to column mapping in an explicitly coded method. Testing showed that this interface was orders of magnitude faster. The issue was how to change the 2,100 business class users of the data layer.

A large application under development cannot freeze code while a transformation of an interface is constructed and tested. We had to construct and test the transformations in a parallel branch of the code repository from the main development stream. When the transformation was fully tested, then it was applied to the main code stream in a single operation.

Less than 35 bugs were found in the 17,100 changes. All of the bugs were quickly resolved in a three-week period.

If the changes were done manually we estimate that it would have taken 8,500 hours, compared with 235 hours to develop the transformation rules.

The task was completed in 3% of the expected time by using Rewrite Rules. This is an improvement by a factor of 36."

from “Transformation of an application data layer” Will Loew-Blosser OOPSLA 2002

http://portal.acm.org/citation.cfm?id=604258

[randomdata]

> but there are no large smalltalk projects for two reasons:

But mostly because it was expensive. Objective-C and Ruby got you halfway there for free, and there is nothing developers love more than something that is free.

[igouy]

(Elephant in the room) Free-as-in-beer Java!

[ReflectedImage]

Well it's a lack of training problem.

Someone properly trained with something like Smalltalk will on average output 3x the amount of software as someone trained on something like Java.

There are big advantages to doing it.

[EMM_386]

> Well it's a lack of training problem.

The industry spends billions of dollars on developers writing Java. If they could spend 3 times less by simply training developers to use Smalltalk instead, they'd be doing it.

They're not, because that's not the problem.

[randomdata]

> If they could spend 3 times less by simply training developers to use Smalltalk instead, they'd be doing it.

No they wouldn't. While not bad long-term thinking, by the time developers are up to speed with Smalltalk and realizing three times the output, the competition using the ecosystem its developers already knew will have launched something and won over the customers. It doesn't matter how much software you can crank out after you've already lost.

[sebstefan]

It solves the problem of having your type mismatches happening at runtime as exceptions and weird behaviors when they could be happening at compile-time as a type error instead

I've worked with both Javascript and Typescript and the ease of patching up Typescript projects you're not familiar with is unmatched compared to Javascript. At least when my code compiles, I'm sure the plumbing is correct

[vundercind]

> JavaScript has lots of wacky problems but its main advantage to me was the loosy goosy approach to types.

It runs in the browser. That’s always been its only advantage. Even now that it’s much better than it used to be: still true.

> Not sure why nobody built something like reentrent exceptions or cool stuff like that, instead they built a stupid jail that down compiles to unreadable sludge.

TIL machine-readable and -verifiable versions of the documentation you should be writing anyway (but probably aren’t) is a jail.

Also one of the reasons I didn’t worry about it going the way of other compile-to-JS languages is that it’s output is nearly identical to what I would have written anyway, so it’s got a clean and easy “escape hatch”. But maybe I write unreadable sludge.

[tom_]

I've had it generate some verbose stuff when using .?, along these lines:

    (_c = this.log) === null || _c === void 0 ? void 0 : _c.withIndent('    ', () => {
        var _a;
        // (pointless ?. silence eslint)
        (_a = this.log) === null || _a === void 0 ? void 0 : _a.pn(`Buffer address: 0x${utils.hex8(bufferAddress)} `);
    });

This was originally this:

    this.log?.withIndent('    ', () => {
        // (pointless ?. silence eslint)
        this.log?.pn(`Buffer address: 0x${utils.hex8(bufferAddress)} `);
    });

If you have a long chain of ?., perhaps it gets really ugly.

[fallingsquirrel]

It's just downleveling the syntax so it runs in browsers that are too old to support `?.` (similar to what Babel would do). If you set your compile target to es2020 or later it will emit `?.` verbatim.

[vundercind]

Oh no, they’ve added more features JS doesn’t actually support. Enums were one thing, this was… an extremely bad idea. I hope it’s not a sign they’re gonna move farther into being a separate language.

[edit] oh no wait that’s in newer JS versions, you’re just “compiling” to a version that doesn’t support it. Update your target to a version that supports the feature you used and it should be fine.

[madeofpalk]

Right - if you use a language feature that is newer than your compile target, it will compile down 'modern' syntax like that. I'm not sure what else you would expect.

[tom_]

The discussion topic was cases where the js output includes a bunch of extra junk, so this is just intended as an example of that! Mostly the output looks pretty much like the input.

(The compile target in my case is ES2017, as configured in August 2018. I can probably update that.)

[G3rn0ti]

I think the biggest advantage TypeScript gives is discoverability when using a language server driven development environment. Hover over a function and you’ll get its signature and doc string. This will work quite quickly due all of the type information pointing back to its definition. This kind of static analysis is impossible in a weakly typed language due to the fact a random variable could hold anything at runtime. In this case an IDE cannot help you much inside an unfamiliar code base.

At my workplace a team of test engineers wrote an entire little test framework around our application. It‘s using webdriver.io under the hood but defines all test classes in type script. Everytime I need to inspect a failing test I open it up in my Emacs and jump around the test method definitions quickly and easily and enjoy inline doc strings popping up wherever I set my cursor on. So the task of fixing a test becomes quite easy despite not having written the framework. Back when we used JS or Perl this task used to be quite obscure.

On the other hand when I see react applications written in typescript I become quite skeptical of the supposed architectural benefits of static typing in front end logic. While React applications were already difficult to grasp, static typing constraint make refactorings even more headachy and I receive Java‘s spring framework vibes constantly.

[pjc50]

> I think the biggest advantage TypeScript gives is discoverability when using a language server driven development environment.

+1: I'm much slower working in environments where I have to do this manually. This is why I've been infiltrating Python type annotations in our codebase.

[IshKebab]

It sounds like you have simply not experienced the problems that loosy goosy types cause. They tend to be biggest when you're working on large projects and on other people's code.

If you've only done small projects or projects where you are the primary author then you may not run into the issues. You essentially end up doing what Typescript does but in your head without writing anything down.

The problems it solves are:

* Bugs! It catches lots of bugs.

* Navigating code efficiently. You can just click stuff to go to its definition or uses.

* Refactoring code reliably. You can now rename variables without making mistakes.

* Reading code. It can be extremely difficult to understand code without static types because you don't know what anything is or where anything goes unless you run it (which can be very difficult).

Not Typescript, but as an example I was trying to understand some code in Gitlab like `auto_cancel_from_rules.merge(auto_cancel_from_config)`. "what does `merge` do?" I wondered.

Literally could not find it. You can't search for `merge`, way too many results. I don't know what the types of the variables are so I can't look it up. I spent about 15 minutes looking around and eventually gave up.

With static types you can literally just click it and it will take you to the definition.

[jerf]

If I never again in my career have to encounter the God Function that everything in the system calls one way or another and takes 9 arguments, all of which are something like "either a string identifying an ID, or a function yielding a string, or a function that yields a list or an iterator of strings, or an object with a GetID method, or if the third parameter was falsy, a function to be called if the user is not authenticated", I will be pleased. Or the function that has literally 40 parameters, 36 of them optional, and while each of them may be individually reasonably well defined you will never work out what all combinations of them do, and you can also know there is no test and no spec for all possible combinations. (Unlike the former which is characteristic of local codebases and bad discipline, the latter is the basis of major dynamic scripting language libraries.)

Dynamic typing doesn't have to get that messy, but it takes discipline that is very hard to enforce at scale. Static typing can sort of approximate that level of mess but it takes a lot more work, and perhaps even more importantly, it's a lot safer to fix. But every significantly-sized dynamic scripting code base I've encountered has certainly had at least one of those two issues deeply, deeply ground into it.

[randomdata]

> Bugs! It catches lots of bugs.*

Unlikely. Maybe if you are using a language with a complete type system (let's face it, you are not), but otherwise you are necessarily going to have to encode all the type information into your tests anyway, so you haven't gained anything on this front. A partial type system cannot replace these tests.

Your other points are the real wins, though.

[IshKebab]

I didn't say it catches all bugs. I said it catches lots of bugs, which it absolutely does.

It's literally impossible to write tests to find all bugs. Most tests don't come remotely close to that, so there's always going to be bugs that static type checks find that tests don't.

There's a great paper that shows that even after tests, Typescript would catch 15% of Javascript bugs: https://earlbarr.com/publications/typestudy.pdf

Also the fact static typing eliminates entire classes of bugs means you need to write far fewer tests. I've seen Python tests that literally fed different types into functions and verified that they accepted them. What a misguided waste of effort!

[randomdata]

> I didn't say it catches all bugs.

It is always telling when someone starts getting worked up about something, especially when that something wasn't even said or implied.

> Also the fact static typing eliminates entire classes of bugs means you need to write far fewer tests.

You don't need to write any more tests in the absence of static types. The purpose of testing is not to act as a replacement for static types and if you find yourself writing tests just for the sake of testing types, you know you're doing something horribly wrong. But, you necessarily have to encode type information into the tests in order of them to execute. After all, if that wasn't the case, you wouldn't even be able to catch bugs with a type system. As such, you gain that indirectly.

> I've seen Python tests that literally fed different types into functions and verified that they accepted them. What a misguided waste of effort!

Sure, I've seen developers do all kinds of stupid things too. In fact, give them Typescript and they will just litter the code with `any` everywhere – something I've witnessed far too often. There is no technical solution to bad developers. Was there supposed to be some meaningful takeaway here?

[IshKebab]

> You don't need to write any more tests in the absence of types.

To achieve the same level of quality, yes you absolutely do. This is actually a fairly fundamental fact about static typing. Static typing is a weak form of formal verification, or equivalently formal verification is just really really strong static typing. Clearly you don't need to write as many tests for formally verified code. The same is true (to a lesser extent) for "ordinary" static typing.

> Sure, I've seen developers do all kinds of stupid things too.

It's not stupid if you have a static typing system available! The stupidity was relying on tests to verify types, instead of ... you know, the thing whose whole purpose is to verify types.

[randomdata]

> This is actually a fairly fundamental fact about static typing.

If you have a complete type system. But as we are specifically talking about partial type systems, you have to already cover all your bases for where the type system is lacking, and by virtue of that you are going to overlap with what the type system also covers.

> It's not stupid if you have a static typing system available!

There is no reason for it, static type system or not.

[agos]

it catches them before writing tests, which is a clear win

[randomdata]

Except you need to write the test first, else there is no way to ensure that your tests actually work and aren't passing because your tests have bugs. So what have you won, exactly?

[IshKebab]

It's much faster to find bugs because an IDE instantly underlines the exact line where the mistake is as you write it, than it is to write a load of code and then debug failing tests.

And as I said in the other comment, tests won't catch all of the mistakes that static typing will catch anyway.

[randomdata]

If you have a complete type system, sure. Then you have constraint on the subtle mistakes one is likely to make.

The partial type systems found in languages people actually use, though, only constrain the most glaring of mistakes that you are almost never going to make. Not impossible that you could make one, but highly unlikely. Certainly not on the order of "lots". More like once in a blue moon.

Refactoring is a different story. Having an editor that lights up like a Christmas tree when code changes breaks existing relationships is a huge boon, and with good refactoring tools you almost never have to break the relationships in the first place. This is where (partial) static typing truly shines.

[igouy]

Write a little bit of code and debug one failing test? TDD?

[agos]

I don't "need" to write test firsts. TDD is one good way of writing software, but not the only one and not a requirement to write good software.

[eternityforest]

Type checking has caught SO many bugs that would otherwise have taken a 30 second test to find. The time savings really adds up, and it catches a fair amount of bugs that otherwise would have made it to prod.

To me it's one of the top requirements for a modern language.

[wruza]

It’s practical. You change your structures and forget places to fix. Typescript trying to solve that.

Edit: Also you can follow typedefs of a library and make sense of it without relying on its documentation quality or deciphering the code.

[stiiv]

In my opinion, JavaScript's main advantage is that it can be run in browsers in addition to other (i.e. server) environments.

If you're building something simple, and the type/shape of function parameters is either very obvious or very well-guarded, TypeScript's returns diminish.

However:

As a reviewer of complex code, I want to see annotations so that I can better understand what I'm reviewing.

As an author of complex code, I want to clearly communicate the intent of functions I write, so that they are not misused by other developers.

As someone who supports the use of my software, I want to reduce errors by guaranteeing the correct types/shapes of function arguments.

...and I'm just getting started. These are all very compelling needs in my experience.

[Vinnl]

> that down compiles to unreadable sludge.

I think there might be a couple of other tools around in your setup (that might influence your feelings). TypeScript mostly just strips out type annotations, so the output looks pretty close to your input.

[imetatroll]

I have never had typescript really get in my way and it does have an escape hatch if you need it so, personally, I would always prefer to use it.

[verelo]

This is so my experience. Also when you can just declare something as “any” and effectively say f it to the entire concept they’re trying to enforce…what’s the point? From time to time human nature takes over and you use any, and the disease has started the spread. If i wanted loose types, i wouldn’t have used typescript. So “pick a side” is all i can ever think when i work with ts.

[tom_]

You need a getout clause sometimes, and it's useful to have one. (You should prefer "unknown", though, which requires you to cast the value on each use, over "any", which treats the value as being of all possible types. You can configure eslint to moan at you if you use "any": https://typescript-eslint.io/rules/no-explicit-any/)

[vundercind]

“Any” is incredibly useful. It lets you transition JS code to TS without having to do the whole thing at once. It lets you work with libraries written in JavaScript without having to immediately find or write types for them. The language would be nearly unusable in the real world without it, and that’d have been even more true in its early days.

[seper8]

You know you can do loose types in C# and many other "strongly typed" languages too?

[wruza]

The point is you have most things covered and that one that is too complex to type you ignore and rely on softer contracts there.