Extended Object Literals to review

P T Withington ptw at pobox.com
Mon Mar 14 13:34:51 PDT 2011


On 2011-03-14, at 14:29, Jorge wrote:

> On 14/03/2011, at 18:32, P T Withington wrote:
>> On 2011-03-13, at 18:15, Juan Ignacio Dopazo wrote:
>>> 
>>> 
>>> The idea behind it was to be able to walk down the prototype chain by doing
>>> o.constructor.prototype.contructor.proto... But then I realized that's not
>>> the case even in today's javascript.
>> 
>> I agree that we need this.  (...)
> 
> Isn't that the purpose of Object.getPrototypeOf() ?

If I have a class `c` whose superclass is `s`, I'm trying to understand how I can get from an object that is an instance of `c` to the superclass.  I believe the current desugaring that Alan proposed, which obeys Brendan's recommendation that `constructor` be a property of the prototype results in:

  o = new c();
  o.constructor === c
  o instanceof c => true
  o instanceof s => true
  o.constructor.prototype instanceof s => true

but:

  o.constructor.prototype.constructor === c

?

I don't see how I can recover `s` from `o` (or `c`), which seems like a useful operation.  What am I missing?


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