On Wed, Jul 18, 2018 at 11:05 AM Michael Theriot <
michael.lee.ther...@gmail.com> wrote:
> I think `in` and `instanceof` could both benefit from having negated
> versions.
>
> Assuming the developer is using `in` correctly, hasOwnProperty concerns
> are irrelevant. Either way they would attempt to use !(a in b), not
> !hasOwnProperty.
>
Why should we assume the developer is using `in` correctly?
Apologies if I buried my question at the end. It was, what are the use
cases for `in` that would not be better served by an ergonomic, infix
hasOwnProperty?
Same reason we don't use...
> !(a == b) // a != b
> !(a === b) // a !== b
>
> !(a > b) // a <= b
> (!(a > b) && !(a == b)) // a < b
>
I'm not sure this is relevant to your larger point, and I've already
conceded ergonomics, but
these last two are not equivalent because NaN is weird.
a = NaN, b = 0
[!(a > b), a <= b] // [true, false]
[!(a > b) && !(a == b), a < b] // [true, false]
> On Thursday, June 28, 2018, 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()
>> }
>>
>> What about a !in operator to write it like this?
>> if ('x' !in obj && 'y' !in obj) {
>> doit()
>> }
>>
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