On Jun 13, 2014, at 12:07 PM, Jussi Kalliokoski wrote:
>
>
> function Foo () {}
>
> Foo.prototype[Symbol.create] = null;
@@create methods are normally defined as methods of the constructor function
rather than as an instance method on the prototype. So the above should be:
Foo[Symbol.create] = null;
>
> // ???
> // Maybe error out, like currently host objects without [[Construct]]:
> // TypeError: Foo is not a constructor.
> new Foo();
as currently specified [1] (and after I fix a bug I just noticed) it will fall
back to doing the equivalent of Object.create().
I did that to maximize backwards compatibility for this specific situation:
function Foo() {};
Foo.__proto__ = null; //in ES6 default @@create inherited from
Function.prototype becomes unavailable
new Foo; //but in ES1-5 this still does the equivalent of Object.create();
If we go down the route of eliminating [[Construct]] and are willing to break
backwards compat. for this case, then we could make 'new' throw if a
constructor doesn't have a callable @@create. That would provide a good way to
indicate that a function is not a constructor (which is current determine based
upon it having a [[Construct]] internal method.
Allen
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