Object.mixin rather than Object.getOwnPropertyDescriptors

[Claude Pache]

Le 22 avr. 2014 à 21:05, Andrea Giammarchi <andrea.giammarchi at gmail.com> a écrit :

> IMO every time you use `getOwnPropertyDescriptor` over a `getOwnPropertyNames` you are asking for a `getOwnPropertyDescriptors` implementation, that's the use case.

And in these cases, again, are the descriptors used for something else than applying them immediately to another object? (This is a real question, for personally I barely use `getOwnPropertyNames` for other purpose than debugging.)

> 
> Twisting your question, do you have any use case for `getOwnPropertyNames` that won't require later on `getOwnPropertyDescriptor` ?

Maybe, but `Object.getOwnPropertyNames` and `Object.getOwnPropertyDescriptor` (in ES5) are fundamental methods that cannot be decomposed into other methods, and on which libraries can build more complex functionalities. (Not sure about the `getOwnProperty{Names,Symbol}` dichotomy of ES6, but that's another question.) On the other hand `Object.getOwnPropertyDescriptors` and `Object.mixin` are complex methods.

—Claude

> 
> 
> On Tue, Apr 22, 2014 at 11:59 AM, Claude Pache <claude.pache at gmail.com> wrote:
> 
> Le 22 avr. 2014 à 19:58, Andrea Giammarchi <andrea.giammarchi at gmail.com> a écrit :
> 
> > while I think that
> > Object.create(
> >
> >
> > Object.getPrototypeOf(originalObject),
> >
> >
> > Object.getOwnPropertyDescriptors(originalObject)
> > )
> > looks semantically better than
> > Object.mixin(
> >
> >
> > Object.create(Object.getPrototypeOf(originalObject)),
> >
> >   originalObject
> >
> > )
> > I also think that Object.mixin could be used for similar cases but I am not sure if:
> >       • is able to mixin also not enumerable and Symbols
> 
> When it was still in the ES6 draft, `Object.mixin` *did* copy all own properties.
> 
> >       • performs some unrequired magic such rebinding getters and setters that should not happen or actually does not make sense to me
> 
> My feeling is that in most cases where that magic is not required, it is also not very important. Or there could be an option for enabling/disabling that functionality, for that would seem better to me than two wildly different ways for getting almost the same result.
> 
> > The reason such long method name has been proposed was for symmetry with defineProperties and as meaningful plural version that should not exclude Object.mixin
> >
> > Long story short, when mixin is needed, use mixin, otherwise when all descriptors are needed, use getOwnPropertyDescriptors?
> 
> Do you have cases where getting all descriptors is used for something else than setting them immediately to another object? My point is that I don't see the added value of `Object.getOwnPropertyDescriptiors` once you have a correctly designed `Object.mixin`-like method.
> 
> —Claude
> 
> 
> >
> > In few words I don't see how having both could hurt anyone
> >
> >
> >
> >
> > On Tue, Apr 22, 2014 at 10:27 AM, Claude Pache <claude.pache at gmail.com> wrote:
> > Hi,
> >
> > There has been request to add `Object.getOwnPropertyDescriptors` (plural) to the standard. Reviewing use cases presented in thread [1] or in older thread [2], it seems to me that all of them boil down to copy all own properties of one object to another, e.g.,
> >
> >     Object.defineProperties(target, Object.getOwnPropertyDescriptors(source))
> >     Object.create(proto, Object.getOwnPropertyDescriptors(source))
> >     // etc.
> >
> > However, this is exactly what `Object.mixin` (deferred from ES6) was designed for:
> >
> >     Object.mixin(target, source)
> >     Object.mixin(Object.create(proto), source)
> >     // etc.
> >
> > Besides being shorter to write, `Object.mixin` has the advantages of (1) not creating an intermediate object; (2) taking care of some subtleties, like rebinding `super` for methods, getters and setters if needed.
> >
> > Therefore, I think that `Object.mixin` is a better function to have than `Object.getOwnPropertyDescriptors`.
> >
> > —Claude
> >
> >
> > [1] http://esdiscuss.org/topic/object-getownpropertydescriptors-o-plural
> > [2] http://esdiscuss.org/topic/object-getownpropertydescriptor
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> > es-discuss at mozilla.org
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> >
> 
>