Comment by mdhb | Hacker News Reader

Comment by mdhb | Hacker News Reader

Parent Full thread

I genuinely don’t understand this sentiment at all. Typescript looks great when you put it next to JavaScript in most cases. And looks like shit when you put it next to any other modern language that emerged from a similar time frame (Kotlin, Dart, Swift etc..)

I really don’t see TypeScript destined for long term success with the rise of Wasm on the web. It is only where it is currently because it has operated at a huge advantage of being the only viable solution to a problem that every web developer has needed.

I say this as someone who writes a lot of typescript professionally and a lot of Dart for everything else I possibly can. The difference between the two is huge on almost every factor I can think of where Dart wins by a considerable margin. I’m thankful that Typescript existed at a time when it did but I don’t think it’s in anyway actually a good or sensible language (because it’s so closely to JavaScript) and I can’t wait to not have to use it in the future because better options exist and are becoming viable for more use cases.

Have you engaged with the advanced features? TS is the only mainstream language that lets you express pretty much everything in the typesystem, to the point where I frequently have to hold myself back.

Having used Swift and Kotlin in the past, their typesystems don’t come close to the flexibility with which you can wrangle data in TS. Many concepts that I would consider fundamental are either not present or require complicated syntax eg.: product types A & B, sum types A | B, { …spreading }.

And where Swift needs custom syntax such as `guard let` and `case let` to narrow types, Typescript is able to analyze normal control flow.

For practical reasons, there are a ton of ugly workarounds, but I’d rather live with those than go back to the rigid “Java++” languages.

> product types A & B, sum types A | B

those are intersection types and union types and are much more unique and rare in type systems eg all typed functional languages have product/sum types but typescript is the only mainstream language I know to have unions and intersection.

The problem is the type system is not strong, where structural typing can cause a lot of issues, such as adding a property to an object for example and the typechecker will not care. This does not happen in more strongly, non-structural typed languages.

Yeah that's one of the practical workarounds I mentioned. It mostly comes up while spreading (which is why spreads should usually go first) and when persisting (which is why your ORM should have a runtime schema).

But it's a double edged sword:

- You can brand types with additional information. For example, React Query does this to keep track of which type is stored under which cache-key. This is where most strongly typed languages just give up.

- You can progressively extend/narrow types without having to worry about inheritance. Invariants can be statically checked by encoding them in a type: eg IssuedInvoice = Invoice & { … }. A function that needs only a subset of a domain-object can specify this rather than requiring the email-address to verify a phone number.

- You can even emulate nominal types using keyed unions.

The first two alone have saved me from more errors than structural typing introduced.

Why is Dart better in your experience?

Well: Static types exist at runtime, VM can optimize using type information (Inline caching, Devirtualization, predictable, fixed object layout), AOT compiled, Dart’s type system is sound, language-supported Isolates (wow feature), hot reload at runtime (wow feature) since Dart can patch classes and functions in memory.

That's a really good list. Thanks. I also miss type annotations not being reflected at runtime (like in Python). Would be great for things like schema validations at runtime. That said, I understand the challenges: that would require changing JS, and that would make JS files larger.

Reply on news.ycombinator.com