Proposal: syntactic sugar for extracting fields from objects

Bob Myers rtm at gol.com
Thu May 30 18:43:00 UTC 2019


It would be fabulous if we could get one or more of these proposals
implemented as a Babel feature, but I think this would require the Babel
team making the relevant changes to Babylon, and my understanding is that
they do this only for features that have at least already started down the
committee track--understandable, but a kind of catch-22.

You are one of many people whoi have wondered about this kind of feature
over the years, including dozens of Stack Overflow members, calling it by
different names, including picking, extended destructuring, extended dot
notation, picked properties, etc. My own proposal at
https://github.com/rtm/js-pick-notation is just one of several, although I
should mention that it represents the outcome of multiple iterations of
research and thinking, and its documentation is IMHO relatively clean and
complete, although it does not include the actual proposed changes to the
ECMAScript spec which need to be created at some point.

Bob

On Thu, May 30, 2019 at 11:29 AM Jacob Pratt <jhprattdev at gmail.com> wrote:

> My understanding is that Babel does support proposals, even if they
> require new syntax. Of course, it would require changes to the parser
> that's beyond my understanding of the codebase. I'd certainly help out in
> whatever ways I'm able to.
>
> For the record, though, I actually had this idea completely separate from
> the proposal — I ran across it when searching to see if anyone else had
> proposed such a syntax/language feature.
>
> On Thu, May 30, 2019, 14:24 Bob Myers <rtm at gol.com> wrote:
>
>> I don't know what "community" means, other than a bunch of people
>> subscribing to this ML, and I can't imagine how one would define, or
>> achieve, or identify, a "consensus" of that community, or why or how the
>> community would vote on anything, or what such the results of such a vote
>> would mean.
>>
>> The very next step is to identify a champion. Such a champion would
>> presumably help to shape, review, and choose between alternatives for the
>> proposals. However, given the failure of my half-hearted efforts to find a
>> champion, and the fact that no one has emerged as champion over the several
>> years since these discussions started, allow me to be pessimistic.
>>
>> It's odd to me because features such as property spread/rest notation,
>> and before that destructuring, have clearly demonstrated the appetite of
>> the "community" for language changes to better support manipulation of
>> properties--not surprising, since objects and their properties can be
>> considered the fundamental data structures of the language. This specific
>> proposal has a relatively small syntactic footprint in my opinion, and
>> measures up well against the majority of criteria that people commonly
>> apply to language design decisions and have been documented on this list. I
>> can only conclude that wiser minds than my own have concluded that this
>> particular feature simply does not rise to the level of priority of other
>> features that are progressing down the pipeline.
>>
>> WIth regard to the notion of implementing this feature on a test basis,
>> the most obvious approach to doing that is as a Babel plug-in, but based on
>> my research--please-correct me if I'm wrong--Babel supports many kind of
>> transformations but not entirely new syntax as is the case here; that
>> requires essentialy rewriting internal parts of its parser. I have
>> experimented with a Sweet implementation with some success, but actually
>> I'm not really sure what that is supposed to demonstrate or if anyone would
>> care.
>>
>> Bob
>>
>> On Thu, May 30, 2019 at 12:29 AM guest271314 <guest271314 at gmail.com>
>> wrote:
>>
>>> Not a rule. Just an email to this board.
>>>
>>> On Thu, May 30, 2019 at 7:26 AM Григорий Карелин <grundiss at gmail.com>
>>> wrote:
>>>
>>>> I'm new to this community, so I'd appreciate if you clarify: is that
>>>> your opinion or is it kind of rule written somewhere?
>>>>
>>>> чт, 30 мая 2019 г. в 09:59, guest271314 <guest271314 at gmail.com>:
>>>>
>>>>> > Wouldn't it be better to consolidate the decision? I mean as OP I
>>>>> vote for `from`, but if majority will say they better like `x.{y, z}` I'll
>>>>> take it.
>>>>>
>>>>> No. There should not be any prohibition as to the additions different
>>>>> solutions to a single proposal. Neither proposal is "better" right now as
>>>>> neither have been coded, tested, and if necessary, specified. A simple
>>>>> majority does not mean correct or complete. The more approaches available
>>>>> the more ability to compose the code from different perspectives,
>>>>> outputting the same result; expanding the language both in syntax and reach
>>>>> as to possible composition, without setting an arbitrary specification to a
>>>>> single majority at only this point in time.
>>>>>
>>>>> The tersest have been able to achieve so far on a single line using an
>>>>> immediately invoked arrow function and object rest which requires writing
>>>>> the identifier twice.
>>>>>
>>>>> If part of the requirement for the proposal is terse code, following
>>>>> the pattern of an immediately invoked arrow function if  ```=``` operator
>>>>> between expressions ```()``` the arrow `>` and return value could be
>>>>> omitted as being designated implicit immediately invoked arrow function
>>>>> with default return value set from the destructured parameters, or
>>>>> ```undefined``` set as value of target identifiers, or plain object
>>>>> ```{}```, resulting in the syntax, within at least an object literal,
>>>>> possibly preceded by spread syntax, will result in
>>>>>
>>>>> ```let obj = {otherData:'other
>>>>> data',...(({firstName,lastName})=(user.profile)}```
>>>>>
>>>>> being equivalent to
>>>>>
>>>>> ```let obj = {otherData:'other
>>>>> data',...(({firstName,lastName})=>({firstName,lastName}))(user.profile)}```
>>>>>
>>>>>
>>>>> On Thu, May 30, 2019 at 6:38 AM Григорий Карелин <grundiss at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Wouldn't it be better to consolidate the decision? I mean as OP I
>>>>>> vote for `from`, but if majority will say they better like `x.{y, z}` I'll
>>>>>> take it.
>>>>>>
>>>>>> чт, 30 мая 2019 г. в 06:35, guest271314 <guest271314 at gmail.com>:
>>>>>>
>>>>>>> > I think it's possible to find someone who will represent the will
>>>>>>> of community.
>>>>>>>
>>>>>>> Individuals can compose the code right now.
>>>>>>>
>>>>>>> > At the moment the question is does community have will to add
>>>>>>> proposed sugar to the language, and if so, which version.
>>>>>>>
>>>>>>> Why would there be any restriction on the versions of syntax which
>>>>>>> would achieve the requirement? The original proposal using ```from``` and
>>>>>>> other proposals could each be created, tested, specified.
>>>>>>>
>>>>>>> On Wed, May 29, 2019 at 7:37 PM Григорий Карелин <grundiss at gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> True
>>>>>>>>
>>>>>>>> I think it's possible to find someone who will represent the will
>>>>>>>> of community.
>>>>>>>>
>>>>>>>> At the moment the question is does community have will to add
>>>>>>>> proposed sugar to the language, and if so, which version.
>>>>>>>>
>>>>>>>> ср, 29 мая 2019 г. в 22:30, Oriol _ <oriol-bugzilla at hotmail.com>:
>>>>>>>>
>>>>>>>>> If you want to add this you will need a champion, see
>>>>>>>>> https://github.com/tc39/ecma262/blob/master/CONTRIBUTING.md#new-feature-proposals
>>>>>>>>>
>>>>>>>>> -- Oriol
>>>>>>>>>
>>>>>>>>> El 29/5/19 a les 21:15, Григорий Карелин ha escrit:
>>>>>>>>>
>>>>>>>>> I agree.
>>>>>>>>>
>>>>>>>>> So, what does community think? Do we want to have “destructuring
>>>>>>>>> picking” sugar in JS and if we do, which syntax looks more attractive?
>>>>>>>>>
>>>>>>>>> I’d suggest to vote
>>>>>>>>>
>>>>>>>>> _______________________________________________
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>> es-discuss at mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>
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