Andrea Giammarchi wrote:
__Current Status__
(Thanks for the dunders! :-P)
Instead of formalizing its form, ES6 accepted `Object.setPrototypeOf`
as described in specs and decided to silently move beside, but still
have in specs, the dunder `__proto__` form, fixing at least a couple
of related gotchas so that:
* unless explicitly set as property, `__proto__` is a named property
for every object that should not affect inheritance so that
`obj["__proto__"]` or `obj[key]` where `key` is the string
`"__proto__"` should not hot/swap the prototypal chain
I'm not sure what you mean here, but first, __proto__ is not specified
in ES6 drafts as an own property. See
http://people.mozilla.org/~jorendorff/es6-draft.html#sec-B.2.2.1
B.2.2.1
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-object.prototype.__proto__>
Object.prototype.__proto__
Object.prototype.__proto__ is an accessor property with attributes {
[[Enumerable]]: false, [[Configurable]]: true }. The [[Get]] and [[Set]]
attributes are defined as follows
B.2.2.1.1
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-get-object.prototype.__proto__>
get Object.prototype.__proto__
The value of the [[Get]] attribute is a built-in function that requires
no arguments. It performs the following steps:
1. Let /O/ be the result of calling ToObject
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-toobject> passing
the *this* value as the argument.
2. ReturnIfAbrupt
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-returnifabrupt>(/O/).
3. Return the result of calling the [[GetPrototypeOf]] internal method
of /O/.
B.2.2.1.2
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-set-object.prototype.__proto__>
set Object.prototype.__proto__
The value of the [[Set]] attribute is a built-in function that takes an
argument proto. It performs the following steps:
1. Let /O/ be CheckObjectCoercible
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-checkobjectcoercible>(*this*
value)/./
2. ReturnIfAbrupt
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-returnifabrupt>(/O/).
3. If Type
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-ecmascript-data-types-and-values>(/proto/)
is neither Object or Null, then return /proto/.
4. If Type
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-ecmascript-data-types-and-values>(/O)/
is not Object, then return /proto/.
5. Let /status/ be the result of calling the [[SetPrototypeOf]]
internal method of /O/ with argument /proto/.
6. ReturnIfAbrupt
<http://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-returnifabrupt>(/status/).
7. If /status/ is *false*, then throw a *TypeError* exception.
8. Return /proto/.
/be
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