Well, of course not. You can't "run" TypeScript.
I don't think you could give general advice on what is slower as that's a constantly moving target.
Looks like assemblyscript compiles "a strict variant of TypeScript" directly to Wasm:
https://github.com/AssemblyScript/assemblyscript
This is pretty close to "running" TypeScript.
Never heard of AssemblyScript, but yeah, it or a statically typed language like it is where frontend development needs to go. In concordance with my point about TS being fundamentally unsuitable, the AssemblyScript docs (https://www.assemblyscript.org/basics.html#strictness) say:
> WebAssembly is fundamentally different from JavaScript, ultimately enabling entirely new use cases not only on the web. Consequently, AssemblyScript is much more similar to a static compiler than it is to a JavaScript VM. One can think of it as if TypeScript and C had a somewhat special child.
> Unlike TypeScript, which targets a JavaScript environment with all of its dynamic features, AssemblyScript targets WebAssembly with all of its static guarantees, hence intentionally avoids the dynamicness of JavaScript where it cannot be compiled ahead of time efficiently.
"It's just a type checker for JavaScript" - not really. It's a language that transpiles to JavaScript and it happens to be a superset of JavaScript (namespaces and enums, anyone?).
But saying that it's just a layer on top of JavaScript sounds like saying C++ is just a layer on top of C.
C++ used to be just a layer on top of C, but not anymore. If it still was, it wouldn't be a bad thing to say.
Type checks that run during compilation/transpilation/typechecking do not "run" as the code is executed. This is what happens with Typescript, and that's what the original commenter was saying.
When people talk about C performance, they mean the performance of the code written in C and (ultimately) compiled to machine language. Very seldom they mean the speed of compilation (though they sometimes do, in which case they almost always explicitly mention "compilation").
When people talk about Typescript performance, they either mean Javascript performance or, more likely, the speed with which Typescript type-checks their code; the latter doesn't happen in run time. That's what the original commenter meant when they said "you cannot run Typescript". It's also what TFA means by "performant".
[0] -- https://deno.land/