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Re: document.register and ES6

From: Daniel Buchner <daniel@mozilla.com>
Date: Wed, 6 Feb 2013 12:41:50 -0800
Message-ID: <CAHZ6zJFE1=qT-hPtf+aOiaaptAaiavv+GaVuXthfZRZorOpPHw@mail.gmail.com>
To: Scott Miles <sjmiles@google.com>
Cc: Erik Arvidsson <arv@chromium.org>, Dimitri Glazkov <dglazkov@google.com>, public-webapps <public-webapps@w3.org>, Boris Zbarsky <bzbarsky@mit.edu>
Scott: is this example not intended to work in IE9? It throws, the output
object is missing the 'oranginate' method.

Daniel J. Buchner
Product Manager, Developer Ecosystem
Mozilla Corporation


On Wed, Feb 6, 2013 at 12:32 PM, Scott Miles <sjmiles@google.com> wrote:

> There were several errors in my pseudo-code, here is a working version:
>
> http://jsfiddle.net/yNbnL/1/
>
> S
>
>
> On Wed, Feb 6, 2013 at 12:01 PM, Scott Miles <sjmiles@google.com> wrote:
>
>> Errata:
>>  makePrototypeTwiddlingConstructorForDomNodes needs to know the extendee
>>
>>  var ctor = makePrototypeTwiddlingConstructorForDomNodes(inExtends,
>> inClass);
>>
>>
>> On Wed, Feb 6, 2013 at 11:59 AM, Scott Miles <sjmiles@google.com> wrote:
>>
>>> On Wed, Feb 6, 2013 at 11:18 AM, Erik Arvidsson <arv@chromium.org>wrote:
>>>
>>>> On Wed, Feb 6, 2013 at 1:38 PM, Scott Miles <sjmiles@google.com> wrote:
>>>> > Sorry, replace MyButton.super() with MyButton.super.call(this);
>>>> >
>>>> >
>>>> > On Wed, Feb 6, 2013 at 10:37 AM, Scott Miles <sjmiles@google.com>
>>>> wrote:
>>>> >>
>>>> >> So, neglecting issues around the syntax of document.register and the
>>>> >> privatization of callbacks, is it fair to say the following is the
>>>> intended
>>>> >> future:
>>>> >>
>>>> >> class MyButton extends HTMLButtonElement {
>>>> >>   constructor() {
>>>> >>     super();
>>>> >>     // make root, etc.
>>>> >>   }
>>>> >> }
>>>> >> document.register('x-button', MyButton);
>>>> >>
>>>> >> If so then can we do this in the present:
>>>> >>
>>>> >> MyButtonImpl = function() {
>>>>
>>>> What do you mean here?
>>>>
>>>> >>   MyButton.super();
>>>>
>>>> Did you get that backwards? I don't see how MyButtonImpl can be
>>>> derived from MyButton.
>>>>
>>>
>>> Its not. The 'super' means 'the super-class constructor for MyButton
>>> that does not include magic DOM object generation' (in this case,
>>> HTMLButtonElement). For MyDerivedButton, MyDerivedButton.super would point
>>> to MyButtonImpl.
>>>
>>> The existence of MyButtonImpl is an unfortunate side-effect of needing a
>>> generated constructor.
>>>
>>> The idea is to correspond as closely as possible with the ES6
>>> version. MyButtonImpl goes away in ES6, it's purpose in the meantime is
>>> just to provide something that looks like a proper class.
>>>
>>> I could write it this way:
>>>
>>> *MyButton = function() {
>>>
>>>   MyButton.super();
>>>   // make root, etc.
>>> };
>>> MyButton.prototype = Object.create(HTMLButtonElement, { ... });*
>>> *
>>> MyButton = document.register(‘x-button’, MyButton);
>>> *
>>>
>>> Written this way, MyButton no longer refers to the constructor you
>>> specified, but instead refers to the generated constructor. This is
>>> conceptually cleaner, but it's a bit tricky. For maximum clarity, I named
>>> the internal version MyButtonImpl in my example code, but there is no
>>> reason to have that symbol.
>>>
>>>
>>>>
>>>> >>   // make root, etc.
>>>> >> };
>>>> >> MyButtonImpl.prototype = Object.create(HTMLButtonElement, { ... });
>>>> >>
>>>> >> // the ‘real’ constructor comes from document.register
>>>> >> // register injects ‘super’ into MyButton
>>>> >> MyButton = document.register(‘x-button’, MyButtonImpl);
>>>>
>>>> What is the relationship between MyButton and MyButtonImpl?
>>>>
>>>> If MyButton.__proto__ === MyButtonImpl and
>>>> MyButton.prototype.__proto__ === MyButtonImpl.prototype then this
>>>> might work (but this cannot be polyfilled either).
>>>>
>>>>
>>> MyButton.prototype == MyButtonImpl.prototype or
>>> MyButton.prototype.__proto__ == MyButtonImpl.prototype, depending on needs.
>>>
>>> MyButton itself does magic DOM construction work that we cannot do with
>>> normal inheritance, then invokes MyButtonImpl. MyButtonImpl is never used
>>> as a constructor itself (not as an argument to 'new' anyway).
>>>
>>> From the user's perspective, he has made a single class which implements
>>> his element (the goal!). The unfortunate name shenanigan (I called my class
>>> MyButtonImpl, but after 'register' I refer to it as MyButton) is the
>>> simplest way I could conceive to overcome the 'generated constructor'
>>> problem.
>>>
>>> To be clear, everything I come up with is intended to polyfill (modulo
>>> my error), because I generally am writing those myself (at first anyway).
>>> One version might look like this:
>>>
>>> document.register = function(inExtends, inClass) {
>>>   var ctor = makePrototypeTwiddlingConstructorForDomNodes(inClass);
>>>   ctor.prototype = inClass.prototype;
>>>   addToTagRegistry(inExtends, ctor, inClass);
>>>   ctor.super = getClassForExtendee(inExtends);
>>>   return ctor;
>>> };
>>>
>>>
>>> --
>>>> erik
>>>>
>>>
>>>
>>
>
Received on Wednesday, 6 February 2013 20:42:48 GMT

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