>> So you don’t think the two roles clash semantically? (1) “Turn an object
>> exemplar into a class” versus (2) “get the class of an object”. Both are
>> definitely useful! But that they can be performed by the same operator seems
>> like a happy coincidence. If (1) was to be further refined, e.g., as Brendan
>> suggested, by throwing an exception if an object exemplar does not have a
>> "constructor" method then it seems both roles would drift further apart. I’m
>> mainly arguing for a clear separation of concerns.
>
> The two roles are the same!
=== Role 1 ===
> The value of the constructor property of an object exemplar is a function
> exemplar (AKA class exemplar) whose prototype property's value is the object
> exemplar. When you say:
> let P = class {constructor() {} };
> You aren't turning an object exemplar into a class exemplar your are simply
> accessing the class exemplar that is explicitly defined as part of the
> object exemplar.
>
> The above let is also equivalent to:
>
> let PrototypalP = {constructor(){} };
> let P = class PrototypalP;
>
> which is equivalent to:
>
> let P = class {constructor(){} };
> let PrototypalP = P.prototype;
=== Role 2 ===
> Finally, when I talk about an object's constructor I include the possibility
> that 'constructor' is inherited, so the above identifies only hold when an
> own constructor property is explicitly provided. In fact, that is really
> what I mean by an object exemplar
>
> var foo = { };
> class foo is Object; //true
> ??? Object.prototype is foo; //also true
>
> bar = new foo; //same as new foo.constructor which is the same as new
> Object
> class bar is class foo; //and both === Object.
>
> It all falls out of the plumbing.
That makes sense (apart from the line marked with ???).
I like to have a human language, intuitive description for what an operator
does. How about the following one for `class`?
“Retrieve the class (function exemplar) of the operand”
or “go to the nearest class” [in the case of an object exemplar, the
nearest class is inside the exemplar]
But the description is *not* “determine the constructor function that created
the operand”.
--
Dr. Axel Rauschmayer
a...@rauschma.de
home: rauschma.de
twitter: twitter.com/rauschma
blog: 2ality.com
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