Async variant

[yuchi]

Brought from a comment to the original proposal Gist by @Jamesernator:

Will there also be an async variant in this proposal, or would that be a consideration for later proposals? e.g.

const file = do async { // or async do or something
    const response = await fetch('some-resource.txt') // the main purpose of a async do would be to allow await
    response.text()
}
// file is the promise response response.text()

Please note that the discussion went on on the original thread.

[jakearchibald]

This would work really well for functions that take promises. Eg fetchEvent.respondWith in service worker, or event.waitUntil which is used in a few specs like the web locks proposal.

So instead of:

event.respondWith(async function() {
  const cachedResponse = await caches.match();
  return cachedResponse || fetch(event.request);
}());

Folks could do:

event.respondWith(do async {
  const cachedResponse = await caches.match();
  cachedResponse || fetch(event.request);
});

[be5invis]

Also there could be do * {} for generators/monads.

do * {
 const x = yield get()
 yield set(x +1);
}

[qubyte]

Came here inspired by upcoming Rust async blocks. 👍

[atg]

Seems to me it should be async do rather than do async, for symmetry with async function() { } etc.

[bakkot]

I think this is a great idea, and I've begun a proposal for this. Feel free to follow along there.