Web workers don't share memory (other than SAB) with the main thread, they are far from traditional threads. These APIs are designed the way they are to protect end users, stop sites from consuming resources or bad code blocking the main thread. None of that is needed to be that way on the server. There is zero reason that a JS implementation cannot implement proper threads within the same memory space. The issue is that all js engines are derived from the browser where that isn't wanted, they simply don't have support for it. Traditional threads need careful use,

Nowhere did I say that full, or even any, compatibility with Node is needed - it isn't.

We need to stop conflating JS the language with the runtimes.

A JS runtime absolutely can get by without a GC, you just never dealloc and consume indefinitely. That doesn't change any semantics of the language, if a value/object is inaccessible, it's inaccessible...

An arena allocator provides a route to say embedding a js-to-native app in a single threaded web server like Nginx, you don't need to share memory between what in effect become "isolates".

NodeJS has worker threads[0] already

[0]: https://nodejs.org/docs/latest/api/worker_threads.html

> Web workers don't share memory (other than SAB) with the main thread, they are far from traditional threads. These APIs are designed the way they are to protect end users, stop sites from consuming resources or bad code blocking the main thread. None of that is needed to be that way on the server.

It doesn't protect end users any more than it protects servers. Node could easily expose raw threading, but they don't because nearly the whole language isn't thread safe and everything would break. It has almost nothing to do with protecting users, it's a language design decision that enforces other design constraints.

> We need to stop conflating JS the language with the runtimes

If you're just sharing syntax but the standard library is different and essentially none of the code is compatible, it's not the same language. ECMAScript specifies all of the things you're talking about, and that is JavaScript, irrespective of the runtime.

> A JS runtime absolutely can get by without a GC, you just never dealloc and consume indefinitely. That doesn't change any semantics of the language, if a value/object is inaccessible, it's inaccessible...

If you throw away the whole heap on every request, now every request it's definitionally a "cold start". Which negates the singular benefit that this post is calling out. Porffor is still not faster than JITed engines at runtime, and initializing the code still has to happen.

> Nowhere did I say that full, or even any, compatibility with Node is needed - it isn't.

You have to square what you're saying with this statement. What you're describing is JavaScript in syntax only. You're talking about major departures from the formal language spec. Existing JavaScript code is likely to break. Why not just make a new language and call it something else, like Crystal is to Ruby? It works different, you're saying it doesn't care about compatibility... Why even call it JS then?