> Sorry to be dense, but I still don't get it. How can an object have duplicate
> properties? I understand that own properties override properties on
> prototypes.
When you look at the object literal
var source = { foo: 123 };
then you have e.g.
"toString" in source === true
"hasOwnProperty" in source === true
When doing
var target = {};
Object.extend(target, source)
then target gets all those properties *again* (in addition to inheriting them
from Object.prototype).
target.hasOwnProperty(toString) === true
Object.getPrototypeOf(target).hasOwnProperty === true
The following illustrates duplicate properties:
var proto = { foo: 123 };
var obj = Object.create(proto);
console.log(obj.foo === 123); // true
obj.foo = 345;
console.log(proto.foo === 123); // true
Thus, the property "foo" exists twice.
> I don’t see a simple way of “fixing” (property descriptors do have their
> uses) Object.create().
>
> Just allow the second argument to be property descriptor *or* object.
Problem: property descriptors are indistinguishable from normal objects, they
*are* normal objects.
> But, in a way, the proto operator <| is that fix.
>
> Well as far as I can make out from
> http://wiki.ecmascript.org/doku.php?id=harmony:proto_operator that operator
> is limited to member expressions.
Right, my bad, the rhs has to be an object literal. But that still takes are of
many (if not most) use cases.
--
Dr. Axel Rauschmayer
[email protected]
twitter.com/rauschma
home: rauschma.de
blog: 2ality.com
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