> 1. every call to `new Foo(...args)` creates a distinct object not
reference-equal to any other such call.
Would this mean
```
function factory() { return []; }
```
would qualify as a constructor?
On Fri, Jan 20, 2017 at 5:29 PM, Scott Sauyet <[email protected]> wrote:
> Bradley Meck wrote:
> > I am unsure the exact question.
>
> I certainly agree that it's not a well-formulated question. Perhaps
> in the end it's not even coherent. But it seems to make some sense.
> I suspect that the answer is simply that it cannot be done. But I
> don't know how to demonstrate that.
>
>
> > `new` will allocate an object with a prototype for sure, but it is never
> > guaranteed to return that object even with classes.
> >
> > ```js
> > let a = {};
> > class Foo {
> > constructor() {
> > return a;
> > }
> > }
> > const g = new Foo();
> > console.log(new Foo() === g);
> > ```
>
> Which demonstrates that `Foo` by such a criterion is not a reasonable
> constructor function. I think that makes sense. It clearly isn't
> one.
>
> > If the question is "How can an external observer know if a constructor
> > returns `this` vs some other object?" the answer is, you cannot.
>
> No, I don't think that's the central point. But perhaps the examples
> above do capture something fundamental. Even if we cannot prove it
> about an arbitrary function, that seems like a minimal criteria for a
> function to be a reasonable constructor:
>
> > A function, `Foo` can be used as a constructor function if
> > 1. every call to `new Foo(...args)` creates a distinct object not
> reference-equal to any other such call.
> > 2. ??
>
> Does that make sense? Are there other important criteria?
>
> Of course this doesn't help us answer whether a particular function
> actually meets these criteria, but it's a start.
>
> -- Scott
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