On Oct 19, 2013, at 7:55 AM, Rick Waldron wrote:
>
>
> On Sat, Oct 19, 2013 at 10:25 AM, teramako <teram...@gmail.com> wrote:
> Hi
>
> I believe Object.assign never update the target's [[prototype]]. But current
> rev19 spec is using Put. So I'm afraid of following case will update the
> [[prototype]].
>
> var soruce = {};
> Object.defineProperty(source, "__proto__", {
> value: { a: "A", b: "B" },
> enumerable: true
> });
> var target = {};
> Object.assign(target, source);
> Is this expected result ? and is there a plan to change to
> DefinePropertyOrThrow from Put ?
>
>
> Object.assign is essentially a "batch property assignment with Put"; I
> believe what you're describing above is Object.mixin, which is "batch
> property definition with DefinePropertyOrThrow".
>
Actually, this is a good point. As currently specified Object.assign of with
an own __proto__ property on the RHS object will trigger a [[SetPrototypeOf]]
on the LHS object. Is that what we want. It is a direct fallout of specifying
Object.assign as the equivalent of a sequence of property assignments from the
RHS to the LHS. "__proto__" could be special cased. But should it?
Object.mixin doesn't have this issue because, as Rick points out, it uses
GetOwnProperty/DefineProperty instead of Get/Set.
Anybody want to argue that Object.assign shouldn't trigger [[SetPrototypeOf]]?
Allen
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