Picking (deconstructing) properties into object literals

[Mark]

Definitely agree with isiah and kai. The proposal original mentioned is not
as readable as its less-terse counterparts. I'm all for less code that does
more, but not at the expense of not being able to easily look at the code
and understand what's going on.  And if not, there had better be a good
reason to introduce it into the spec. Hope this helps!

On Wed, Aug 23, 2017, 12:45 AM kai zhu <kaizhu256 at gmail.com> wrote:

> -1 and agree with isiah
>
> furthermore, i see javascript deconstruction as a never-ending
> can-of-worms that too-often devolves into ruby-esque confusion / arguments
> over the “best” way to do assignments. NO AMOUNT of language-spec changes
> will resolve all these arguments, so forget about it.
>
> p.s. the principle of avoiding language-spec changes that snowball into
> necessitating future language-spec changes, *when established good-enough
> solutions already exist*, should be used more often by tc39 (and also
> avoid needlessly de-optimizing engine-implementations and making the
> overall world-wide-web slower).
>
> On Aug 23, 2017, at 12:36 PM, Isiah Meadows <isiahmeadows at gmail.com>
> wrote:
>
> Honestly, I'm not sure how necessary this really is. `_.pick` exists
> in Lodash, Underscore, and Ramda, but I'm not seeing it in persistent
> data structure libraries like Immutable.js [1] or Mori [2], where it
> would seemingly be *more* critical.
>
> [1]: https://facebook.github.io/immutable-js/docs/#/Map
> [2]: https://swannodette.github.io/mori/
>
> For what it's worth, with those libraries, if you'd want something
> like `pick`, you could use something like this:
>
> ```js
> // Immutable.js
> function pick(map, keys) {
>    return map.filter((_, key) => keys.includes(key))
> }
>
> // Mori
> function pick(map, ...keys) {
>    return mori.reduce(
>        (acc, key) => mori.assoc(acc, key, mori.get(map, key)),
>        mori.hashMap(), keys)
> }
> ```
> -----
>
> Isiah Meadows
> me at isiahmeadows.com
>
> Looking for web consulting? Or a new website?
> Send me an email and we can get started.
> www.isiahmeadows.com
>
>
> On Tue, Aug 22, 2017 at 11:22 PM, Bob Myers <rtm at gol.com> wrote:
>
> Extending the ways we can construct object literals has been a sort of
> theme
> in JS language design recently, with shorthand object notation in ES6, and
> now spread properties. The motivations include conciseness and readability.
>
> With destructuring assignment, the community decided it made sense to add
> syntax to easily destructure selected properties of an object into
> variables. With spread properties, the community is deciding it makes sense
> to add syntax to easily include all properties from one object into an
> object literal. The missing piece is the ability to include selected
> properties of an object into an object literal.
>
> When asked by people we are mentoring or teaching how to create an object
> containing selected properties from other objects (which happens with
> surprising frequency), we usually just tell them to write
>
> ```js
> {p: a.p, q: a.q, r: b.r, s: b.s}
> ```
>
> Or sometimes
>
> ```js
> const {p, q} = a;
> const {r, s} = b;
> const newObj = {p, q, r, s};
> ```
>
> Neither of which is ideal. In this proposal, we allow the following syntax:
>
> ```js
> { {p, q} = a, {r, s} = b }
> ```
>
> Here, the `{p, q} = a` is exactly the same production as the spec's
> *AssignmentExpression**, as used in destructuring assignment. That includes
> the ability to rename properties (`{q1: q2} = a}`), specify defaults (`{q1
> =
> 42} = a`), and pick out nested properties (`{q1: {q11}} = a`). In other
> words, we take full advantage of the power of current destructuring
> assignment syntax when picking properties into object literals. The sole
> new
> syntactic aspect in this proposal is the ability to place the
> *AssignmentExpression* construct *inside* an object literal.
>
> A fuller description of this proposal can be found at
> https://github.com/rtm/js-pick-notation.
>
> --
> Bob
>
>
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