In my experience with web browsers, you can't do this because Javascript can NEVER block. For example, if a function takes too long to run, it blocks rendering of the page. If there were ways to make Javascript asynchronously, browsers would have implemented it already, so I assume they can't do it without potential backward incompatibility.

One exception is alert(), which blocks and shows a dialog. But I don't think I've ever seen a website use it instead of showing a "normal" popup with CSS. It looks ugly so it's only used to debug that code actually runs.

I'm not knowledgeable about low-level interruptions, but I think you would need at least some runtime code to implement blocking the thread. In any case, even if the language provides this, you can't use it because the main thread is normally a GUI thread that can't respond to user interaction if it's blocked by another thread. That's the main point of using (background) threads in the first place: so the main thread never blocks from IO bottlenecks.