This is my personal Github site for posting links to various JavaScript-related projects. Some Smalltalk and perhaps some Java (the weakling in the family - it needs static typing props :)) as well
I had a first attempt a few years ago. At that time, my idea to work around the lack of green threads in JavaScript was to use continuation-passing style. Such an implementation would also elegantly solve the issue of resumable exceptions. But, while theoretically doable (leaving aside the horrible looking generated JavaScript sources), stack growth was prohibitive. This was made worse by the fact that any operations on primitives would also have to be implemented, very expensively, as CPS. Essentially no optimization seemed possible unless combined with type inferencing. While I did have prior experience with type inferencing and I had used it succesfully to transpile Smalltalk to Java, in this case, it seemed to defeat the purpose: inferencing types in order to transpile dynamically typed Smalltalk to dynamically typed JavaScript.
As JavaScript has added new features in the last few years, the time seems ripe for a second attempt using the latest and greatest of what JavaScript now offers: weak references, classes (with parallel hierarchies! and fields), bigint, proxies, (plus other niceties like promises, dynamic imports, globalThis), and, last but not least, generators. With generators we have an alternative way of implementing green threads that does not suffer from the drawbacks of CPS Of course, we'll have to see how well they scale in practice, since in our approach, all Smalltalk methods are translated as generator methods and all invocations are translated as yield* invocations. The idea is to surface the preemption points in the generated JavaScript methods, as the only (conditional) yield expressions. The active process becomes inactive when the condition is met (so when yield gets executed). Processes are resumed via top-level (well, at the bottom of the stack) next() invocations.
Update (July 7, 2023): Almost three years have passed since I wrote the above paragraphs, but finally, the idea behind the second attempt has borne fruit. Now, if you click on the button below, you will find some real, running code in that repository