Suggestion: Destructuring object initializer.

Isiah Meadows isiahmeadows at gmail.com
Sat Feb 10 23:33:32 UTC 2018


>
>
Another common reaction is "big deal, saving a few characters or lines".
> But more than one recent language feature also falls into this category of
> mainly or purely sugar and brevity. For instance, property spread syntax is
> pretty much just sugar for `Object.assign`, yet everyone seems to think
> it's the best thing since sliced bread.
>

My understanding of this differs:

- It was to bring feature parity with array spread destructuring.
- The proposal included both merging and extracting.
- It actually optimized for an exceptionally common case (React circles
benefitted the most, but others did quite a bit, too), immutable update of
record-like objects. In my experience, that scenario is *more* common than
array spread (beyond rest parameters), and engines can optimize for objects
that are not referenced elsewhere by not actually copying them, something
harder to do with `Object.assign`.\*
- You *could* implement it via `Object.assign`, but it chopped the number
of characters down to less than half for most cases if you're not just
merging. Most of these pick proposals aren't coming close.

\* I don't know/believe if they do, but it's pretty easy to implement with
type info.


> Bob
>
> On Sat, Feb 10, 2018 at 10:07 AM, Naveen Chawla <naveen.chwl at gmail.com>
> wrote:
>
>> Sorry sent by accident before my message was edited properly. My basic
>> point was that since curly braces are used for both destructuring and
>> object literals, there's an issue with being able to glance at the code and
>> quickly discern what's happening if they are mixed together in the same
>> piece of syntax. Not impossible, just a potential source of bugs and/or
>> delay in understanding the data structure being declared.
>>
>> On Sat, 10 Feb 2018 at 10:01 Naveen Chawla <naveen.chwl at gmail.com> wrote:
>>
>>> I'm not a TC39 member, but I have a little readability issue with
>>> destructuring inside an object:
>>>
>>> ```js
>>> { {p1, p2} = p, {q1, q2} = q }
>>> ```
>>>
>>> has a very different meaning than
>>>
>>> ```js
>>> { p: {p1, p2}, {q1, q2} = q }
>>> ```
>>>
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