Reflect.hasOwn

Isiah Meadows isiahmeadows at gmail.com
Wed Sep 28 23:36:08 UTC 2016


I'll admit I use them partially out of laziness and partially because
engines already optimize for this much better than with actual maps (only
string keys). I frequently alias `const hasOwn =
Object.prototype.hasOwnProperty`, so this wouldn't do much for me other
than saving a declaration in each file I use it. Honestly, though, I feel
it was a design flaw from the start to be on the prototype, but we can't
just time travel and fix it.

On Tue, Sep 6, 2016, 16:42 Maël Nison <nison.mael at gmail.com> wrote:

> JSON.parse() and object literals are big sources of objects-as-maps. In
> both of these cases, using the `in` operator won't give the right answer.
>
> Le mar. 6 sept. 2016 à 22:11, Domenic Denicola <d at domenic.me> a écrit :
>
>> Reflect is a namespace that contains the proxy traps (it’s a bit of an
>> unfortunate name), so we shouldn’t be adding things to it that are not part
>> of the meta-object protocol.
>>
>> A new namespace, or using Object, might be OK. I think that it will still
>> be controversial, since this proposal is in support of an objects-as-maps
>> programming style which has caused many problems in the past and should not
>> be encouraged. See e.g.
>> http://www.2ality.com/2012/11/proto-breaks-webapps.html.
>>
>> If you are using objects-as-maps safely, you’d use Object.create(null),
>> in which case the `in` operator works fine and there's no need for
>> hasOwnProperty incantations.
>>
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