Is this really the most direct way to get %AsyncIteratorPrototype%?
When creating iterators and async iterators outside generators, it'd be extremely useful to have these exposed more easily accessible...
Generators are super useful about 99% of the time in my experience, but there is that 1% where generators don't really work - this is not uncommon when you're adapting something to one of those two interfaces, like adapting an event emitter, and a few of the more complex operators, like "zip" (which is just easier to write using a raw iterator).
Isiah Meadows contact at isiahmeadows.com, www.isiahmeadows.com
Isiah Meadows contact at isiahmeadows.com, www.isiahmeadows.com
More or less, but just language-exposed. And apart from those two, I don't think there's a major reason to expose most of the rest. About the only reason I've encountered to want to make that distinction for anything else with internal prototypes is object inspection.
Alternatively, we could expose Iterator/AsyncIterator constructors
that happen to have their prototype properties set to the relevant
iterator prototypes. That would arguably be more useful and flexible,
since iterator classes could just extends Iterator, and if you want
the object literal/Object.create route, you could just use
Iterator.prototype or AsyncIterator.prototype.
Isiah Meadows contact at isiahmeadows.com, www.isiahmeadows.com
On Tue, Aug 14, 2018 at 7:12 PM, Isiah Meadows <isiahmeadows at gmail.com> wrote:
When creating iterators and async iterators outside generators, it'd be extremely useful to have these exposed more easily accessible...
Agreed.
On Tue, Aug 14, 2018 at 7:18 PM, Jordan Harband <ljharb at gmail.com> wrote:
Something like this: ljharb/es-abstract/blob/master/GetIntrinsic.js#L40-L46
or
tc39/test262/blob/c55d2ab7c344e35a3ceb93cf1d4d30019584db82/harness/wellKnownIntrinsicObjects.js
I must be misreading those or something, but as far as I can tell, they both (I think they're basically the same thing) just give you a specific generator object, not %AsyncIteratorPrototype%: jsfiddle.net/urv04Lp7
-- T.J. Crowder
On Tue, Aug 14, 2018 at 7:42 PM, T.J. Crowder <tj.crowder at farsightsoftware.com> wrote:
I must be misreading those or something, but as far as I can tell, they both (I think they're basically the same thing) just give you a specific generator object, not %AsyncIteratorPrototype%: jsfiddle.net/urv04Lp7
Yeah, I think you have to go three levels along the prototype chain
from what those give you to get to %AsyncIteratorPrototype%:
jsfiddle.net/dbh9j7av Which makes sense (proto on the gen
object is the async generator function's .prototype; its prototype
is AsyncGeneratorFunction.prototype, and its prototype is
%AsynIteratorPrototype%). But again, maybe I'm missing something.
(If not, I probably need to send a PR to tc39 / test262.)
-- T.J. Crowder
This is the way I've found so far, allocating as few temporary objects as possible (one, can't get rid of that temp function):
const AsyncIteratorPrototype = Object.getPrototypeOf( Object.getPrototypeOf( async function*(){} ).prototype );or, showing the steps more clearly:
const asyncGeneratorFunctionInstance = async function*(){}; const AsyncGeneratorFunction = Object.getPrototypeOf(asyncGen eratorFunctionInstance); const AsyncGeneratorPrototype = AsyncGeneratorFunction.prototype; const AsyncIteratorPrototype = Object.getPrototypeOf(AsyncGen eratorPrototype);(I could create an async generator by calling that temporary async generator function, but then I just have to do another
Object.getPrototypeOf, so it doesn't really buy me anything.)Is there something more direct? (Remember that
AsyncGeneratorFunctionisn't globally exposed likeFunctionis. None of the new subclasses of Function constructors are exposed; according to this thread, there weren't enough strong use cases [that thread is forGeneratorFunction, but we can extrapolate].)-- T.J. Crowder
This is the way I've found so far, allocating as few temporary objects as possible (one, can't get rid of that temp function): ```js const AsyncIteratorPrototype = Object.getPrototypeOf( Object.getPrototypeOf( async function*(){} ).prototype ); ``` or, showing the steps more clearly: ```js const asyncGeneratorFunctionInstance = async function*(){}; const AsyncGeneratorFunction = Object.getPrototypeOf(asyncGen eratorFunctionInstance); const AsyncGeneratorPrototype = AsyncGeneratorFunction.prototype; const AsyncIteratorPrototype = Object.getPrototypeOf(AsyncGen eratorPrototype); ``` (I could create an async generator by calling that temporary async generator function, but then I just have to do another `Object.getPrototypeOf`, so it doesn't really buy me anything.) Is there something more direct? (Remember that `AsyncGeneratorFunction` isn't globally exposed like `Function` is. None of the new subclasses of Function constructors are exposed; according to [this thread][1], there weren't enough strong use cases [that thread is for `GeneratorFunction`, but we can extrapolate].) -- T.J. Crowder [1]: https://esdiscuss.org/topic/why-generatorfunction-constructor-isn-t-directly-exposed-to-end-users -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20180814/ec60dc50/attachment-0001.html>