Re: Object.equals() and Object.clone()

[Alexander Jones]

Object has this unfortunate complication of prototypes, i.e.:

```
const objA = {foo: 1, bar: 2};
const objB = Object.create(objA);
equals(objA, objB) === ?
```

And also there is metadata on each property that can vary (one object has a
property which is configurable, and the other has the same property which
is not configurable), and raise similar questions.

Neither of these questions exist on ES's Map type, or Immutable.js's Map
and List types, for example.

IMO we should be looking at ways to make those types more suitable for many
of the use cases of Object.

On 15 November 2016 at 01:25, Kevin Barabash  wrote:

> It would be nice if deep equality checking and deep cloning of objects was
> included in the standard library.  Has there been any proposals around
> including these in the past?
>
> – Kevin
>
>
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RE: Object.equals() and Object.clone()

[Domenic Denicola]

The biggest problem with structured clone is that there’s no way to just invoke 
it directly. Doing so has been proposed a few times, most recently at 
https://github.com/whatwg/html/issues/793, but no implementers have expressed 
interest.

From: es-discuss [mailto:es-discuss-boun...@mozilla.org] On Behalf Of Kevin 
Barabash
Sent: Monday, November 14, 2016 23:51
To: Eric Devine <devin...@gmail.com>
Cc: es-discuss <es-discuss@mozilla.org>
Subject: Re: Object.equals() and Object.clone()

I didn't know about structured clone so I looked it up.  It looks pretty 
promising.  As for checking if two things are equal, maybe it makes sense for 
objects to define their own `.equals(other)` methods.

https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm

On Mon, Nov 14, 2016 at 9:31 PM, Eric Devine 
<devin...@gmail.com<mailto:devin...@gmail.com>> wrote:
How about beginning with the HTML structured clone algorithm, and a 
`Symbol.clone` property to allow an object to optionally define it's own 
cloning behavior?

On Mon, Nov 14, 2016 at 9:02 PM, Isiah Meadows 
<isiahmead...@gmail.com<mailto:isiahmead...@gmail.com>> wrote:
I agree. Also, consider iterables. Should their `Symbol.iterator` method be 
called? There's no obvious behavior for the details, and people's opinions 
differ on what should be correct.

On Mon, Nov 14, 2016, 20:58 Frankie Bagnardi 
<f.bagna...@gmail.com<mailto:f.bagna...@gmail.com>> wrote:
It's pretty hard to decide how these behave, specifically with custom classes. 
Focusing on Object.clone...

- with classes do you call the constructor, and with what arguments?
- HTMLElement and sub classes can't be constructed directly, what happens with 
them?
- do you copy internal properties? this would make it hard to polyfill
- how does it behave with getters and setters?
- with regular expressions do you copy the lastIndex?

Most of those apply to Object.equals also.



On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
<kev...@khanacademy.org<mailto:kev...@khanacademy.org>> wrote:
It would be nice if deep equality checking and deep cloning of objects was 
included in the standard library.  Has there been any proposals around 
including these in the past?

– Kevin


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Re: Object.equals() and Object.clone()

[Kevin Barabash]

I didn't know about structured clone so I looked it up.  It looks pretty
promising.  As for checking if two things are equal, maybe it makes sense
for objects to define their own `.equals(other)` methods.

https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm

On Mon, Nov 14, 2016 at 9:31 PM, Eric Devine  wrote:

> How about beginning with the HTML structured clone algorithm, and a
> `Symbol.clone` property to allow an object to optionally define it's own
> cloning behavior?
>
> On Mon, Nov 14, 2016 at 9:02 PM, Isiah Meadows 
> wrote:
>
>> I agree. Also, consider iterables. Should their `Symbol.iterator` method
>> be called? There's no obvious behavior for the details, and people's
>> opinions differ on what should be correct.
>>
>> On Mon, Nov 14, 2016, 20:58 Frankie Bagnardi 
>> wrote:
>>
>> It's pretty hard to decide how these behave, specifically with custom
>> classes. Focusing on Object.clone...
>>
>> - with classes do you call the constructor, and with what arguments?
>> - HTMLElement and sub classes can't be constructed directly, what happens
>> with them?
>> - do you copy internal properties? this would make it hard to polyfill
>> - how does it behave with getters and setters?
>> - with regular expressions do you copy the lastIndex?
>>
>> Most of those apply to Object.equals also.
>>
>>
>>
>> On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
>> wrote:
>>
>> It would be nice if deep equality checking and deep cloning of objects
>> was included in the standard library.  Has there been any proposals around
>> including these in the past?
>>
>> – Kevin
>>
>>
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>> ___
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>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>> ___
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>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>
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Re: Object.equals() and Object.clone()

[Frankie Bagnardi]

I guess it could throw if it's unable to clone something. This would
include *any* class without `Symbol.clone`. The error messages would need
to be outstanding for it to be practical. Like showing the path to the
thing that can't be cloned and the name of the constructor.


On Mon, Nov 14, 2016 at 9:01 PM, Michael Theriot <
michael.lee.ther...@gmail.com> wrote:

> I think you'd definitely need to call the constructor for classes because
> of scoped variables (e.g. scoped weakmap for private properties).
>
> I would like a way to compare simple objects like identical arrays though.
>
> On Mon, Nov 14, 2016 at 7:58 PM, Frankie Bagnardi 
> wrote:
>
>> It's pretty hard to decide how these behave, specifically with custom
>> classes. Focusing on Object.clone...
>>
>> - with classes do you call the constructor, and with what arguments?
>> - HTMLElement and sub classes can't be constructed directly, what happens
>> with them?
>> - do you copy internal properties? this would make it hard to polyfill
>> - how does it behave with getters and setters?
>> - with regular expressions do you copy the lastIndex?
>>
>> Most of those apply to Object.equals also.
>>
>>
>>
>> On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
>> wrote:
>>
>>> It would be nice if deep equality checking and deep cloning of objects
>>> was included in the standard library.  Has there been any proposals around
>>> including these in the past?
>>>
>>> – Kevin
>>>
>>>
>>> ___
>>> es-discuss mailing list
>>> es-discuss@mozilla.org
>>> https://mail.mozilla.org/listinfo/es-discuss
>>>
>>>
>>
>> ___
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>>
>>
>
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Re: Object.equals() and Object.clone()

[Michael Theriot]

I think you'd definitely need to call the constructor for classes because
of scoped variables (e.g. scoped weakmap for private properties).

I would like a way to compare simple objects like identical arrays though.

On Mon, Nov 14, 2016 at 7:58 PM, Frankie Bagnardi 
wrote:

> It's pretty hard to decide how these behave, specifically with custom
> classes. Focusing on Object.clone...
>
> - with classes do you call the constructor, and with what arguments?
> - HTMLElement and sub classes can't be constructed directly, what happens
> with them?
> - do you copy internal properties? this would make it hard to polyfill
> - how does it behave with getters and setters?
> - with regular expressions do you copy the lastIndex?
>
> Most of those apply to Object.equals also.
>
>
>
> On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
> wrote:
>
>> It would be nice if deep equality checking and deep cloning of objects
>> was included in the standard library.  Has there been any proposals around
>> including these in the past?
>>
>> – Kevin
>>
>>
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>>
>
> ___
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> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: Object.equals() and Object.clone()

[Eric Devine]

How about beginning with the HTML structured clone algorithm, and a
`Symbol.clone` property to allow an object to optionally define it's own
cloning behavior?

On Mon, Nov 14, 2016 at 9:02 PM, Isiah Meadows 
wrote:

> I agree. Also, consider iterables. Should their `Symbol.iterator` method
> be called? There's no obvious behavior for the details, and people's
> opinions differ on what should be correct.
>
> On Mon, Nov 14, 2016, 20:58 Frankie Bagnardi  wrote:
>
> It's pretty hard to decide how these behave, specifically with custom
> classes. Focusing on Object.clone...
>
> - with classes do you call the constructor, and with what arguments?
> - HTMLElement and sub classes can't be constructed directly, what happens
> with them?
> - do you copy internal properties? this would make it hard to polyfill
> - how does it behave with getters and setters?
> - with regular expressions do you copy the lastIndex?
>
> Most of those apply to Object.equals also.
>
>
>
> On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
> wrote:
>
> It would be nice if deep equality checking and deep cloning of objects was
> included in the standard library.  Has there been any proposals around
> including these in the past?
>
> – Kevin
>
>
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> ___
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> https://mail.mozilla.org/listinfo/es-discuss
>
>
> ___
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>
>
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Re: Object.equals() and Object.clone()

[Isiah Meadows]

I agree. Also, consider iterables. Should their `Symbol.iterator` method be
called? There's no obvious behavior for the details, and people's opinions
differ on what should be correct.

On Mon, Nov 14, 2016, 20:58 Frankie Bagnardi  wrote:

It's pretty hard to decide how these behave, specifically with custom
classes. Focusing on Object.clone...

- with classes do you call the constructor, and with what arguments?
- HTMLElement and sub classes can't be constructed directly, what happens
with them?
- do you copy internal properties? this would make it hard to polyfill
- how does it behave with getters and setters?
- with regular expressions do you copy the lastIndex?

Most of those apply to Object.equals also.



On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
wrote:

It would be nice if deep equality checking and deep cloning of objects was
included in the standard library.  Has there been any proposals around
including these in the past?

– Kevin


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Re: Object.equals() and Object.clone()

[Frankie Bagnardi]

It's pretty hard to decide how these behave, specifically with custom
classes. Focusing on Object.clone...

- with classes do you call the constructor, and with what arguments?
- HTMLElement and sub classes can't be constructed directly, what happens
with them?
- do you copy internal properties? this would make it hard to polyfill
- how does it behave with getters and setters?
- with regular expressions do you copy the lastIndex?

Most of those apply to Object.equals also.



On Mon, Nov 14, 2016 at 6:25 PM, Kevin Barabash 
wrote:

> It would be nice if deep equality checking and deep cloning of objects was
> included in the standard library.  Has there been any proposals around
> including these in the past?
>
> – Kevin
>
>
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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