Promises

Rick Waldron waldron.rick at gmail.com
Tue Nov 6 11:35:00 PST 2012


Based on a read through of https://github.com/promises-aplus/promises-spec,
these things initially come to mind, please regard as a loose collection of
varying thoughts that may or may not be completely relevant:

1. The definition of a "promise" is really just a plain object or function
with an expando property, I would think that a language level addition
would require its own standard built-in object: Promise, which when invoked
as a constructor initializes a new promise object which has a "then"
method... Domenic has it covered from there.

2. The notes describe some excellent practical implementation points, but
none of them are actually part of the ECMAScript standard, eg. setTimeout,
process.nextTick. Should these be specified or left unspecified?
Object.observe describes delivery as "Schedule change events to be
delivered asynchronously 'at the end of the turn'", which is not very
specific.

3. Does this belong in the language or would it make more sense to exist as
a "standard module"?


Rick








On Tue, Nov 6, 2012 at 2:15 PM, David Bruant <bruant.d at gmail.com> wrote:

>  Le 06/11/2012 20:07, Axel Rauschmayer a écrit :
>
> That’s at a weird intersection between HTML5 and ECMAScript, (...)
>
> I think it's more historical than anything. The event loop,
> setTimeout/Interval (and promises) belong to the language (ECMAScript), not
> to a library (HTML5) in my opinion.
> ECMAScript 1-5 were concurrency-neutral. A pure ES5 programs has a start
> and an end and that's it. No concurrency whatsoever.
> ES6 is going in that direction too.
> ES7 opens a breach to event loop concurrency with async observers
> (object.observe)
>
> David
>
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> es-discuss at mozilla.org
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>
>
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