by bastawhiz | 2025-08-17 14:45:32+00:00
> many of the restrictions that people associate with JS are due to VMs being designed to run untrusted code. If you compile your trusted TS/JS to native you can do many new things, such as use traditional threads, fork, and have proper low level memory access. Separating the concept of TS/JS from the runtime is long overdue.

This is just outright wrong. JS limitations come from lots of things:

1. The language has almost zero undefined behavior by design. Code will essentially never behave differently on different platforms.

2. JS has traditional threads in the form of web workers. This interface exists not for untrusted code but because of thread safety. That's a language design, like channels in Go, rather than a sandboxing consideration.

3. Pretty much every non-browser JS runtime has the ability to fork.

4. JS is fully garbage collected, of course you don't get your own memory management. You can use buffers to manage your own memory if you really want to. WASM lets you manage your own memory and it can run "untrusted" code in the browser with the WASM runtime; your example just doesn't hold water. There's no way you could fiddle with the stack or heap in JS without making it not JS.

5. The language comes with thirty years of baggage, and the language spec almost never breaks backwards compatibility.

Ironically Porffor has no IO at the moment, which is present in literally every JS runtime. It really has nothing to do with untrusted code like you're suggesting.

> You can fork a process per request and throw it away each time reclaiming all memory, or have a very simple arena allocator that works at the request level. It would be incredibly performant and not have the overhead of a full GC implementation.

You also must admit that this would make Porffor incompatible with existing runtimes. Code today can modify the global state, and that state can and does persist across requests. It's a common pattern to keep in-memory caches or to lazily initialize libraries. If every request is fully isolated in the future but not now, you can end up with performance cliffs or a system where a series of requests on Node return different results than a series of requests on Porffor.

As for arena allocation, this makes it even less compatible with Node (if not intractable). If means you can't write (in JS) any code that mutates memory that was initialized during startup. If you store a reference to an object in an arena in an object initialized during startup, at the end of the request when the arena is freed you now have a pointer into uninitialized memory.

How do you tell the developer what they can and cannot mutate? You can't, because any existing variable might be a reference to memory initialized during startup. Your function might receive an object as an argument that was initialized during startup or one that's wasn't, and there's no way to know whether it's safe to mutate it.

Long story short, JS must have a garage collector to free memory, or it's not JS.

> It is unlikely that many people would run something compiled with Porffor in a WASM runtime, but the portability it brings is very compelling.

Node (via SEA in v20), bun, and deno all have built in tooling for generating a self-contained binary. Granted, the runtime needs to work for your OS and CPU, but the exact same thing could be said about a WASM runtime.

And of course there are hundreds of mature bundlers that can compile JS into a single file that runs in various runtimes without ever thinking about platform. It's weird to even consider portability of JS as a benefit because JS is already almost maximally portable.

> This experiment from Oliver doesn't show that Porffor is ready for production, but it does validate that he is on the right track, and that the ideas he is exploring are correct.

It validates that the approach to building a compiler is correct, but it says little about whether the project will eventually be usable and good. It's unlikely it'll get faster, because robust JS compatibility will require more edge cases to be handled than it currently does, and as Porffor's own README says, it's still slower than most JITted runtimes. A stable release might not yield much.