Hi Jeremy,
Thanks for the proposal. I've been advocating a minimalist approach to classes
for a while now; I think it's a good goal. A few of us sketched out something
similar on a whiteboard in the last face-to-face meeting; at least, it used the
object literal body. We hadn't thought of two of your ideas:
1) allowing class expressions to be anonymous
2) allowing the RHS to be an arbitrary expression
I like #1; we have a lot of agreement around classes being first-class, and
that just fits right in.
But with #2 I'm not clear on the intended semantics. You say this could be
desugared but don't provide the details of the desugaring. The RHS is an
arbitrary expression that evaluates to the prototype object (call it P), but
the extends clause is meant to determine P's [[Prototype]], right? Do you
intend to mutate P's [[Prototype]]? I wouldn't agree to that semantics.
Another thing that this doesn't address is super(). Right now in ES5 and
earlier, it's pretty painful to call your superclass's constructor:
class Fox extends Animal {
constructor: function(stuff) {
Animal.call(this, stuff);
...
}
}
In general, I think your arbitrary-expression-RHS design is incompatible with
the super keyword, which needs to be lexically bound to its class-construction
site. I'll have to think about it, though.
However, I think the approach of an object literal body (and only an object
literal body) works well. I suspect you could still implement all your examples
of dynamically-computed classes, although probably with a little more work in
some cases.
Dave
On Oct 31, 2011, at 6:57 PM, Jeremy Ashkenas wrote:
> 'Evening, ES-Discuss.
>
> After poking a stick in the bees' nest this morning (apologies, Allen), and
> in the spirit of loyal opposition, it's only fair that I throw my hat in the
> ring.
>
> Here is a proposal for minimalist JavaScript classes that enable behavior
> that JavaScripters today desire (as evidenced by libraries and languages
> galore), without adding any new semantics beyond what already exists in ES3.
>
> https://gist.github.com/1329619
>
> Let me know what you think, and feel free to fork.
>
> Cheers,
> Jeremy Ashkenas
> _______________________________________________
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
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