spankalee • 5 days ago

I think you're conflating cause and effect in several cases. TypeScript can't be thought of, and would never exist, independently from JavaScript like you're trying to do.

TypeScript wasn't created separate from JavaScript and then chose JavaScript as a backend. TypeScript only exists to perform build-time type checking of JavaScript. There wouldn't be a TypeScript that compiled to something else, because other languages already have their own type systems.

Runtime type-checking isn't part of TypeScript because 1) It isn't part of JavaScript, and TypeScript doesn't add runtime features anymore. 2) It'd be very expensive for simple types, 3) Complex types would be prohibitively expense as you have to both reify the types and perform deep structural checking.

WASM also is natively supported, and with newer extensions like reference types and GC, we're getting closer to the point where a DOM API could be defined. It'll still be a long while, but that's the long-term direction it's heading in. But even then, you would only see a TypeScript-to-WASM compiler[1] because there's already so much TypeScript out there, not because TypeScript is a particularly good language for that environment. A more static language would be a lot better for a WASM target.

[1]: Porfor is already such a compiler for JS and TS, but it does not do runtime type-checking: https://porffor.dev/

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mubou • 5 days ago

I was thinking more along the lines of a TypeScript-like compiled language. For example, AssemblyScript[0] but with the web APIs added back in. (Personally I'd prefer C# or Rust, but you know most devs will want to keep using JS/TS.) WASM isn't natively supported in the way that I'm wishing it were, though; you still have to use JS to bootstrap it, and JS to call back into web apis. In my ideal world, I'd want to be able to compile

    public static void Main() { Document.Body.Append(new Div("hello world")); }
and be able to use it in a page like

    <script src="hello.wasm"></script>
and have that just work without any JS "glue code". Maybe someday. I know they're working on the DOM APIs, but as you said, it's been slow going. Feels like priorities are elsewhere. Even CSS is moving forward with new features faster than WASM is (nesting and view transitions are awesome though).

(Btw when I said "separate runtime type checking" I didn't mean language-level; I was referring to the validation libraries and `typeof`'s that are required today since TS types obviously no longer exist after build. If it were a real static language, then of course you can't store a bool in a string in the first place.)

[0]: https://www.assemblyscript.org/ (Porffor looks neat too. Wonder if it could be useful in plugin architectures? E.g. plugins can written in JS, and the program only needs a WASM interpreter. I'll bookmark it. Thanks.)