Proposal: Property Accessor Function Shorthand

sup at aguz.me sup at aguz.me
Sat Dec 7 22:01:04 UTC 2019


> > > I do find it surprising that property access isn't addressed there,
> > > but it seems like it was likely just overlooked - it has no mention in
> > > the repo, in the open issues, or even in the closed issues or any of
> > > the open or closed pull requests.
Actually, they do seem to address it here as a non-goal:
https://github.com/tc39/proposal-partial-application#support-for-receiver-placeholder

If we had that, then we wouldn’t need a specific syntax for property accessors. However, arrow functions are already pretty compact, so I don’t feel a strong desire for this `receiver placeholder` syntax or something like Kotlin’s `it`. I know the same logic applies to a `property accessor` proposal, but accessing properties in JS is extremely common and in my opinion, deserving of a syntax shorthand.

--

Agustín Zubiaga
On Dec 7, 2019, 3:04 PM -0500, Bob Myers <rtm at gol.com>, wrote:
> Can you clarify in what sense you see this as a special case of that proposal?
> To put it in very simple terms, we would like to do something like `array.map(.name)`.
>
> > On Tue, Dec 3, 2019 at 3:33 AM Isiah Meadows <contact at isiahmeadows.com> wrote:
> > > BTW, all this is very much just a special case of this (existing stage
> > > 1) proposal, and is part of why it exists:
> > > https://github.com/tc39/proposal-partial-application
> > >
> > > I do find it surprising that property access isn't addressed there,
> > > but it seems like it was likely just overlooked - it has no mention in
> > > the repo, in the open issues, or even in the closed issues or any of
> > > the open or closed pull requests.
> > >
> > > -----
> > >
> > > Isiah Meadows
> > > contact at isiahmeadows.com
> > > www.isiahmeadows.com
> > >
> > > On Tue, Dec 3, 2019 at 5:43 AM Michael Luder-Rosefield
> > > <rosyatrandom at gmail.com> wrote:
> > > >
> > > > At the cost of adding more code, but giving more power, perhaps what we want is something akin to Kotlin's `it` keyword:
> > > > https://kotlinlang.org/docs/reference/lambdas.html?_ga=2.238822404.500195435.1575368476-1345353619.1575368476#it-implicit-name-of-a-single-parameter
> > > >
> > > > it: implicit name of a single parameter
> > > > It's very common that a lambda expression has only one parameter.
> > > > If the compiler can figure the signature out itself, it is allowed not to declare the only parameter and omit ->. The parameter will be implicitly declared under the name it:
> > > > ints.filter { it > 0 } // this literal is of type '(it: Int) -> Boolean'
> > > >
> > > >
> > > > What we'd want is something concise and non-ambiguous to fulfill the same role; something that cannot currently be a valid identifier, maybe. This is the point where I start scanning the keyboard for underutilised symbols... I'm thinking the hash symbol would work. To re-use the original example:
> > > >
> > > > ```js
> > > > const activeProducts = products.filter(#.active);
> > > > const productNames = products.map(#.name);
> > > > const sortedProducts = _.sortBy(products, #.name);
> > > > const { true: activeProducts, false: inactiveProducts } = _.groupBy(products, #.active);
> > > > ```
> > > >
> > > > It makes intuitive sense in 2 ways, I think; # makes you think of the object hash you're extracting a property from, and also is familiar as something's id from CSS selectors.
> > > >
> > > > We could also extend it to represent multiple parameters: # is also aliased as #0, the 2nd parameter is #1, etc.
> > > >
> > > > Further, dynamic properties would work too: `const fooProducts = products.filter(#[foo]);
> > > > --------------------------
> > > > Dammit babies, you've got to be kind.
> > > >
> > > >
> > > > On Mon, 2 Dec 2019 at 22:32, Waldemar Horwat <waldemar at google.com> wrote:
> > > >>
> > > >> On 11/24/19 9:17 PM, Bob Myers wrote:
> > > >> > FWIW, the syntax `.propName` does appear to be syntactically unambiguous.
> > > >>
> > > >> It conflicts with contextual keywords such as `new . target`.
> > > >>
> > > >>      Waldemar
> > > >> _______________________________________________
> > > >> es-discuss mailing list
> > > >> es-discuss at mozilla.org
> > > >> https://mail.mozilla.org/listinfo/es-discuss
> > > >
> > > > _______________________________________________
> > > > es-discuss mailing list
> > > > es-discuss at mozilla.org
> > > > https://mail.mozilla.org/listinfo/es-discuss
> > > _______________________________________________
> > > es-discuss mailing list
> > > es-discuss at mozilla.org
> > > https://mail.mozilla.org/listinfo/es-discuss
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20191207/f57a36b7/attachment-0001.html>


More information about the es-discuss mailing list