Good point. I've never needed falsey valid values in my obj/maps yet, so
it'll continue to be very rare that I will need to use `in` (and I'll
continue to prefer !obj.x when I don't).
However, for this proposal I would prefer a new keyword like `notin`
instead of `!in`, because the `!` followed by a word normally indicates the
inverse boolean of a value in other cases, whereas a clean break like
`notin` I think seems clearer. Reserved keyword would probably be needed
though?
On Tue, 10 Jul 2018 at 09:44 Jordan Harband <ljh...@gmail.com> wrote:
> `!obj.x` will return true for any falsy property - null, undefined,
> positive or negative zero, NaN, and the empty string. `!(x in obj)` will
> return true only if `x` is not an own property on `obj` nor anything in its
> prototype chain. They are decidedly different tests and they check for
> decidedly different things.
>
> On Mon, Jul 9, 2018 at 9:08 PM, Naveen Chawla <naveen.c...@gmail.com>
> wrote:
>
>> I don't use `in`.
>>
>> What do I get with `'x' !in obj` or `!(x in obj)` that I don't get with
>> !obj['x'] ?
>>
>> Genuinely asking - I don't know what I am missing.
>>
>> I use obj[x] because I believe it's a more familiar syntax and I believe
>> I get the same outcome..(?)..
>>
>> On Mon, 9 Jul 2018 at 22:41 Steve Fink <sph...@gmail.com> wrote:
>>
>>> +1 from me for !in. It's a surprisingly common nuisance.
>>>
>>> And I don't care for the !obj.x workaround at all -- even if you can
>>> survive the difference in semantics, from a code reading point of view this
>>> is saying something entirely different.
>>>
>>> And it is very different semantically. 'x' in obj does [[HasProperty]];
>>> obj.x does [[GetProperty]]. With
>>>
>>> obj = { get x() { print("getter"); return 3; } };
>>>
>>> then |"x" in obj| does not print "getter" while |obj.x| does.
>>>
>>>
>>> On 06/29/2018 12:26 AM, Cyril Auburtin wrote:
>>>
>>>
>>> ```js
>>> if (!obj.x && !obj.y) {
>>> doit()
>>> }
>>> ```
>>> The cases where they are equal to 0, '', null, undefined shouldn't
>>> matter imo, if for example those x and y are numbers, they would be
>>> defined, defaulted to 0, and you would test for `!== 0` rather if needed
>>>
>>> Le jeu. 28 juin 2018 à 18:31, Guylian Cox <guylian...@gmail.com> a
>>> écrit :
>>>
>>>> I agree, it's very annoying to have to write it !(x in y). I've been
>>>> wanting this operator for a very, very long time.
>>>>
>>>> If there is interest for !in, I think !instanceof deserves to be
>>>> included too.
>>>>
>>>> Le jeu. 28 juin 2018 à 18:19, T.J. Crowder <
>>>> tj.crow...@farsightsoftware.com> a écrit :
>>>>
>>>>> On Thu, Jun 28, 2018 at 5:14 PM, Tobias Buschor <
>>>>> tobias.busc...@shwups.ch> wrote:
>>>>> > I dont like to write:
>>>>> > if ( !('x' in obj) && !('y' in obj) ) {
>>>>> > doit()
>>>>> > }
>>>>> >
>>>>> > I was even tempted to write it that way:
>>>>> > if ('x' in obj || 'y' in obj) { } else {
>>>>> > doit()
>>>>> > }
>>>>>
>>>>> There's
>>>>>
>>>>> ```js
>>>>> if (!('x' in obj || 'y' in obj)) {
>>>>> doit()
>>>>> }
>>>>> ```
>>>>>
>>>>> That said, I've wanted !in many a time, in a minor sort of way...
>>>>>
>>>>> -- T.J. Crowder
>>>>> _______________________________________________
>>>>> es-discuss mailing list
>>>>> es-discuss@mozilla.org
>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>
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