Regarding parallel for-loops: I'd consider that a separate problem. You'd want parallel for-loops for things like requests to the same API, where each promise is handled the same way. `await.all` is more for handling disparate tasks in parallel without having to resort to thinking in terms of arrays and iteration.
On Tue, Nov 19, 2019 at 10:27 PM Guy Bedford <[email protected]> wrote: > > Typically I find I want to loop over an iterator of items and apply a > function body of work on them in parallel. > > So it would be nice to support full blocks of statements that can do this > work in parallel, instead of relying on just expressions or functions to > achieve this. > > Extending for loops to have a parallel form is another option (I seem to > recall something similar brought up before here): > > ``` > for await.all (const entry of entries) { > await doWork(entry); > } > ``` > > Whether async iteration should be supported or treated as sync or parallel is > another question though, and possibly a confusion of the form. > > On Tue, 19 Nov 2019 at 23:20, Jordan Harband <[email protected]> wrote: >> >> If we have `await.all`, what about `await.race`, `await.allSettled`, >> `await.any`? >> >> On Tue, Nov 19, 2019 at 7:45 PM Jacob Bloom <[email protected]> wrote: >>> >>> To simplify the problem of working with promises in parallel, I >>> propose this new syntax: >>> >>> ```javascript >>> async function initialize() { >>> let foo, bar, baz; >>> await.all { >>> foo = (await request('foo.json')).data; >>> bar = (await request('bar.json')).data; >>> baz = (await request('baz.json')).data; >>> } >>> render(foo, bar, baz); >>> } >>> ``` >>> >>> Each child statement of the curly braces is evaluated in parallel and >>> execution resumes when they've all resolved. >>> >>> **The Problem:** with current syntax, the above function would >>> probably look something like this: >>> >>> ```javascript >>> async function initialize() { >>> const [ >>> { data: foo }, // renaming response.data => foo >>> { data: bar }, >>> { data: baz }, >>> ] = await Promise.all([ >>> request('foo.json'), >>> request('bar.json'), >>> request('baz.json'), >>> ]); >>> render(foo, bar, baz); >>> } >>> ``` >>> >>> For this kind of use case, `Promise.all` leads to "parallel lists" of >>> promises and their return values, which must be kept in sync. Using >>> those values either requires (sometimes deep) destructuring or >>> temporary variables. >>> >>> This structure is also just fundamentally different from working >>> serially in async/await and it forces you to reason about the problem >>> in a specific way. This doesn't appear to be a conscious decision to >>> force good code practices, it's just a limitation that falls naturally >>> out of the current syntax. Thus, we have an opportunity to shift some >>> of the burden back to the language with this new syntax. >>> >>> Here's the full proposal: >>> https://github.com/mrjacobbloom/proposal-await-all -- let me know what >>> you think! >>> _______________________________________________ >>> es-discuss mailing list >>> [email protected] >>> https://mail.mozilla.org/listinfo/es-discuss >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
