An example for a user-land implementation

[Bnaya]

A while back I wrote a library that exposes js data types behind a proxy, and uses [Shared]ArrayBuffer as the heap
https://github.com/Bnaya/objectbuffer
The objects are free-form

You can transfer the [Shared]ArrayBuffer to a WebWorker/worker_thread, and with the appropriate locking, you can have shared memory js objects

The memory management is done via some kind of reference counting, and user-triggered free pass
While the library actually works, the reason i didn't really use it, is that strings will never be efficient as far as I can see