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Re: [Proxy] No way to hook property creation?

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JJ wrote:

> On Mon, 22 Aug 2022 01:08:06 +0200, Thomas 'PointedEars' Lahn wrote:
>> is one of the reasons why it is *deprecated* since ECMAScript Edition 5,
> 
> Yet, ECMAScript later added `Symbol.unscopables` to support `with`.

Only to make ES 5− code that still uses “with” for *read* access easily 
compatible with ES 6+:

<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/unscopables>

But:

,-<https://262.ecma-international.org/13.0/#sec-with-statement>
| 
| | LEGACY
| |
| | 14.11 The with Statement
| |
| | NOTE 1: Use of the <Legacy> “with” statement is discouraged in new
                                                 ^^^^^^^^^^^^^^^^^^^^^
| | ECMAScript code. Consider alternatives that are permitted in both
    ^^^^^^^^^^^^^^^
| | strict mode code and non-strict code, such as destructuring assignment.
| |
| | […]

,-<https://262.ecma-international.org/13.0/#sec-conformance>
| 
| A conforming implementation of ECMAScript must implement *Legacy*
| subclauses, unless they are also marked as Normative Optional. All of the 
| language features and behaviours specified within Legacy subclauses have 
| one or more undesirable characteristics. However, their continued usage in 
| existing applications prevents their removal from this specification. 
| These features are not considered part of the core ECMAScript language. 
| Programmers should not use or assume the existence of these features and 
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| behaviours when writing new ECMAScript code.
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| 
| | LEGACY
| | 
| | 2.2 Example Legacy Clause Heading
| | 
| | Example clause contents.

>> and *code containing it cannot even be executed* in Strict Mode.
> 
> I'm using `with`, so I don't use Strict mode in the first place.

PEBKAC.

>> This has nothing to do with the capabilities of the Proxy object because
>> its instance does not even "see" that write access.
> 
> That is correct. It's not supposed to and can not be the job for Proxy.
> And that's the problem, because Proxy doesn't have a way to intercept
> property creation.

1. That is false, as I have demonstrated previously.

2. Again: The Proxy instance is NOT the target object in what only *seems*
   to be a property-write access facilitated with the “with” statement.

>> You can determine whether a property is being created in the “set”
>> handler of the Proxy instance:
> 
> That's not possible, because `set()` will only be called if the JS engine
> already know that the property exists as reported by `has()`.

I have demonstrated that to be false previously, too.

-- 
PointedEars
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2
Please do not cc me. /Bitte keine Kopien per E-Mail.

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Thread

[Proxy] No way to hook property creation? JJ <jj4public@outlook.com> - 2022-08-07 12:56 +0700
  Re: [Proxy] No way to hook property creation? "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2022-08-20 17:17 -0700
    Re: [Proxy] No way to hook property creation? JJ <jj4public@outlook.com> - 2022-08-21 14:30 +0700
      Re: [Proxy] No way to hook property creation? "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2022-08-21 15:37 -0700
  Re: [Proxy] No way to hook property creation? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2022-08-22 01:08 +0200
    Re: [Proxy] No way to hook property creation? JJ <jj4public@outlook.com> - 2022-08-23 03:31 +0700
      Re: [Proxy] No way to hook property creation? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2022-08-24 01:45 +0200
      Re: [Proxy] No way to hook property creation? TheScreamingFedora <sebaslogo@gmail.com> - 2022-08-25 08:39 -0700
    Re: [Proxy] No way to hook property creation? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2022-08-27 22:40 +0200

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