Re: Conditional object properties

[Reinis Ivanovs]

It works in Babel without the parenthesis.

On Wed, Nov 2, 2016 at 5:08 PM, Luke Mitchell  wrote:

> That works, although you have to add parenthesis. It's a nice solution
> but it is still a bit more verbose with the spread, the parenthesis
> and the `: null`.
>
> ```
> let cond = true;
> let obj = {
>   prop1: 'hello',
>   ...(cond ? {prop2: 'world'} : null)};
> // { prop1: 'hello', prop2: 'world' }
>
> cond = false;
> let obj = {
>   prop1: 'hello',
>   ...(cond ? {prop2: 'world'} : null)};
> // { prop1: 'hello' }
> ```
>
> On Wed, Nov 2, 2016 at 2:42 PM, Reinis Ivanovs  wrote:
> > No need for new syntax, you can just do this:
> >
> > ```
> > {...cond ? {prop: value} : null}
> > ```
> >
> > I find it about the same in readability.
> >
> > On Wed, Nov 2, 2016 at 2:18 PM, Luke Mitchell  wrote:
> >>
> >> Hi all,
> >>
> >> I often come across a situation where I wish to extend an object
> >> (usually an argument for an API request) if a particular condition is
> >> satisfied, such as the presence of a function parameter. Currently the
> >> only way to do this is by assigning the object to a variable, checking
> >> the condition using an `if` statement and then extending the object. I
> >> am proposing the inclusion of an operator that allows a property to be
> >> included, subject to a particular condition, inside the object
> >> definition.
> >>
> >> The operator looks like this:
> >>
> >> ```
> >> let obj = {
> >>   cond ? prop: value
> >> };
> >>
> >> ```
> >>
> >> The operator could also be used with a block statement, allowing
> >> multiple properties to be included:
> >>
> >> ```
> >> let obj = {
> >>   cond ? {
> >> prop1: value1,
> >> prop2: value2
> >>   }
> >> };
> >> ```
> >>
> >> I have created a draft proposal and would love to hear any thoughts
> >> you have on the matter. You can find it on my GitHub, at the link
> >> below.
> >>
> >> https://github.com/lukem512/proposal-condition-property-definitions
> >>
> >> Kind regards,
> >> Luke
> >> ___
> >> es-discuss mailing list
> >> es-discuss@mozilla.org
> >> https://mail.mozilla.org/listinfo/es-discuss
> >
> >
>
>
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Re: Conditional object properties

[Bergi]

Luke Mitchell schrieb:

Hi all,

I often come across a situation where I wish to extend an object
(usually an argument for an API request) if a particular condition is
satisfied, such as the presence of a function parameter. Currently the
only way to do this is by assigning the object to a variable, checking
the condition using an `if` statement and then extending the object. I
am proposing the inclusion of an operator that allows a property to be
included, subject to a particular condition, inside the object
definition.


You can already do
```js
let obj = Object.assign({
…
}, cond ? { prop: value } : null);
```
Or depending on your condition, also just `cond && { prop: value }`.

The object spread proposal will achieve the same, without the need for 
any extra operator.


- Bergi
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Re: Conditional object properties

[Luke Mitchell]

That works, although you have to add parenthesis. It's a nice solution
but it is still a bit more verbose with the spread, the parenthesis
and the `: null`.

```
let cond = true;
let obj = {
  prop1: 'hello',
  ...(cond ? {prop2: 'world'} : null)};
// { prop1: 'hello', prop2: 'world' }

cond = false;
let obj = {
  prop1: 'hello',
  ...(cond ? {prop2: 'world'} : null)};
// { prop1: 'hello' }
```

On Wed, Nov 2, 2016 at 2:42 PM, Reinis Ivanovs  wrote:
> No need for new syntax, you can just do this:
>
> ```
> {...cond ? {prop: value} : null}
> ```
>
> I find it about the same in readability.
>
> On Wed, Nov 2, 2016 at 2:18 PM, Luke Mitchell  wrote:
>>
>> Hi all,
>>
>> I often come across a situation where I wish to extend an object
>> (usually an argument for an API request) if a particular condition is
>> satisfied, such as the presence of a function parameter. Currently the
>> only way to do this is by assigning the object to a variable, checking
>> the condition using an `if` statement and then extending the object. I
>> am proposing the inclusion of an operator that allows a property to be
>> included, subject to a particular condition, inside the object
>> definition.
>>
>> The operator looks like this:
>>
>> ```
>> let obj = {
>>   cond ? prop: value
>> };
>>
>> ```
>>
>> The operator could also be used with a block statement, allowing
>> multiple properties to be included:
>>
>> ```
>> let obj = {
>>   cond ? {
>> prop1: value1,
>> prop2: value2
>>   }
>> };
>> ```
>>
>> I have created a draft proposal and would love to hear any thoughts
>> you have on the matter. You can find it on my GitHub, at the link
>> below.
>>
>> https://github.com/lukem512/proposal-condition-property-definitions
>>
>> Kind regards,
>> Luke
>> ___
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: Conditional object properties

[Reinis Ivanovs]

No need for new syntax, you can just do this:

```
{...cond ? {prop: value} : null}
```

I find it about the same in readability.

On Wed, Nov 2, 2016 at 2:18 PM, Luke Mitchell  wrote:

> Hi all,
>
> I often come across a situation where I wish to extend an object
> (usually an argument for an API request) if a particular condition is
> satisfied, such as the presence of a function parameter. Currently the
> only way to do this is by assigning the object to a variable, checking
> the condition using an `if` statement and then extending the object. I
> am proposing the inclusion of an operator that allows a property to be
> included, subject to a particular condition, inside the object
> definition.
>
> The operator looks like this:
>
> ```
> let obj = {
>   cond ? prop: value
> };
>
> ```
>
> The operator could also be used with a block statement, allowing
> multiple properties to be included:
>
> ```
> let obj = {
>   cond ? {
> prop1: value1,
> prop2: value2
>   }
> };
> ```
>
> I have created a draft proposal and would love to hear any thoughts
> you have on the matter. You can find it on my GitHub, at the link
> below.
>
> https://github.com/lukem512/proposal-condition-property-definitions
>
> Kind regards,
> Luke
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
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Re: Conditional object properties

[Boris Zbarsky]

On 11/2/16 9:04 AM, kdex wrote:

I'd imagine that from an engine point of view, this means that fewer
object shapes land in memory, at least for v8.


I'm pretty sure it means nothing of the sort in SpiderMonkey (in terms 
of memory usage, not in terms of object shapes that flow through 
subsequent shape guards), for what it's worth.  I'm not sure it's worth 
adding things to the standard just to work around implementation quirks 
of a specific implementation.


No opinion on the ergonomics argument.


Reducing the number of object shapes currently boils down to using an
object literal and setting the properties to `value || null` instead of
extending the object with new properties imperatively.


This actually creates _more_ object shapes in SpiderMonkey, I believe, 
though fewer shapes that flow through code locations.  So it depends on 
whether you're trying to optimize memory usage or performance.  And of 
course on whether you're tuning to a particular engine's current 
implementation strategy...


-Boris
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Re: Conditional object properties

[Luke Mitchell]

Aside from performance, the operator also leads to denser code which is easier 
to write. Talking to my colleagues, I was told that two of them could have used 
it already this morning!

Luke Mitchell

Luke Mitchell

Software Developer

On Wed, 02 Nov 2016 at 13:12 Isiah Meadows

<
mailto:Isiah Meadows 
> wrote:

a, pre, code, a:link, body { word-wrap: break-word !important; }

That's not likely to make any serious performance difference with an ajax call. 
And in tight loops, I try avoid conditionals and object creation anyways, to 
avoid branch prediction fails (in both the engine and CPU) and costly 
allocation. (Most engines only do a limited form of pooling for faster GC.)

On Wed, Nov 2, 2016, 09:04 kdex <
mailto:k...@kdex.de
> wrote:

I'd imagine that from an engine point of view, this means that fewer

object shapes land in memory, at least for v8.

Reducing the number of object shapes currently boils down to using an

object literal and setting the properties to `value || null` instead of

extending the object with new properties imperatively.

On Wednesday, November 2, 2016 12:38:05 PM CET Isiah Meadows wrote:

> What benefit would this bring over imperatively adding properties?

>

> On Wed, Nov 2, 2016, 08:18 Luke Mitchell <
mailto:l...@enki.com
> wrote:

>

> > Hi all,

> >

> > I often come across a situation where I wish to extend an object

> > (usually an argument for an API request) if a particular condition is

> > satisfied, such as the presence of a function parameter. Currently the

> > only way to do this is by assigning the object to a variable, checking

> > the condition using an `if` statement and then extending the object. I

> > am proposing the inclusion of an operator that allows a property to be

> > included, subject to a particular condition, inside the object

> > definition.

> >

> > The operator looks like this:

> >

> > ```

> > let obj = {

> >   cond ? prop: value

> > };

> >

> > ```

> >

> > The operator could also be used with a block statement, allowing

> > multiple properties to be included:

> >

> > ```

> > let obj = {

> >   cond ? {

> >     prop1: value1,

> >     prop2: value2

> >   }

> > };

> > ```

> >

> > I have created a draft proposal and would love to hear any thoughts

> > you have on the matter. You can find it on my GitHub, at the link

> > below.

> >

> >
https://github.com/lukem512/proposal-condition-property-definitions
> >

> > Kind regards,

> > Luke

> > ___

> > es-discuss mailing list

> >
mailto:es-discuss@mozilla.org
> >
https://mail.mozilla.org/listinfo/es-discuss
> >

>

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Re: Conditional object properties

[Isiah Meadows]

That's not likely to make any serious performance difference with an ajax
call. And in tight loops, I try avoid conditionals and object creation
anyways, to avoid branch prediction fails (in both the engine and CPU) and
costly allocation. (Most engines only do a limited form of pooling for
faster GC.)

On Wed, Nov 2, 2016, 09:04 kdex  wrote:

> I'd imagine that from an engine point of view, this means that fewer
> object shapes land in memory, at least for v8.
>
> Reducing the number of object shapes currently boils down to using an
> object literal and setting the properties to `value || null` instead of
> extending the object with new properties imperatively.
>
> On Wednesday, November 2, 2016 12:38:05 PM CET Isiah Meadows wrote:
> > What benefit would this bring over imperatively adding properties?
> >
> > On Wed, Nov 2, 2016, 08:18 Luke Mitchell  wrote:
> >
> > > Hi all,
> > >
> > > I often come across a situation where I wish to extend an object
> > > (usually an argument for an API request) if a particular condition is
> > > satisfied, such as the presence of a function parameter. Currently the
> > > only way to do this is by assigning the object to a variable, checking
> > > the condition using an `if` statement and then extending the object. I
> > > am proposing the inclusion of an operator that allows a property to be
> > > included, subject to a particular condition, inside the object
> > > definition.
> > >
> > > The operator looks like this:
> > >
> > > ```
> > > let obj = {
> > >   cond ? prop: value
> > > };
> > >
> > > ```
> > >
> > > The operator could also be used with a block statement, allowing
> > > multiple properties to be included:
> > >
> > > ```
> > > let obj = {
> > >   cond ? {
> > > prop1: value1,
> > > prop2: value2
> > >   }
> > > };
> > > ```
> > >
> > > I have created a draft proposal and would love to hear any thoughts
> > > you have on the matter. You can find it on my GitHub, at the link
> > > below.
> > >
> > > https://github.com/lukem512/proposal-condition-property-definitions
> > >
> > > Kind regards,
> > > Luke
> > > ___
> > > es-discuss mailing list
> > > es-discuss@mozilla.org
> > > https://mail.mozilla.org/listinfo/es-discuss
> > >
> >
>
> ___
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>
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Re: Conditional object properties

[kdex]

I'd imagine that from an engine point of view, this means that fewer
object shapes land in memory, at least for v8.

Reducing the number of object shapes currently boils down to using an
object literal and setting the properties to `value || null` instead of
extending the object with new properties imperatively.

On Wednesday, November 2, 2016 12:38:05 PM CET Isiah Meadows wrote:
> What benefit would this bring over imperatively adding properties?
> 
> On Wed, Nov 2, 2016, 08:18 Luke Mitchell  wrote:
> 
> > Hi all,
> >
> > I often come across a situation where I wish to extend an object
> > (usually an argument for an API request) if a particular condition is
> > satisfied, such as the presence of a function parameter. Currently the
> > only way to do this is by assigning the object to a variable, checking
> > the condition using an `if` statement and then extending the object. I
> > am proposing the inclusion of an operator that allows a property to be
> > included, subject to a particular condition, inside the object
> > definition.
> >
> > The operator looks like this:
> >
> > ```
> > let obj = {
> >   cond ? prop: value
> > };
> >
> > ```
> >
> > The operator could also be used with a block statement, allowing
> > multiple properties to be included:
> >
> > ```
> > let obj = {
> >   cond ? {
> > prop1: value1,
> > prop2: value2
> >   }
> > };
> > ```
> >
> > I have created a draft proposal and would love to hear any thoughts
> > you have on the matter. You can find it on my GitHub, at the link
> > below.
> >
> > https://github.com/lukem512/proposal-condition-property-definitions
> >
> > Kind regards,
> > Luke
> > ___
> > es-discuss mailing list
> > es-discuss@mozilla.org
> > https://mail.mozilla.org/listinfo/es-discuss
> >
> 

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Re: Conditional object properties

[Isiah Meadows]

What benefit would this bring over imperatively adding properties?

On Wed, Nov 2, 2016, 08:18 Luke Mitchell  wrote:

> Hi all,
>
> I often come across a situation where I wish to extend an object
> (usually an argument for an API request) if a particular condition is
> satisfied, such as the presence of a function parameter. Currently the
> only way to do this is by assigning the object to a variable, checking
> the condition using an `if` statement and then extending the object. I
> am proposing the inclusion of an operator that allows a property to be
> included, subject to a particular condition, inside the object
> definition.
>
> The operator looks like this:
>
> ```
> let obj = {
>   cond ? prop: value
> };
>
> ```
>
> The operator could also be used with a block statement, allowing
> multiple properties to be included:
>
> ```
> let obj = {
>   cond ? {
> prop1: value1,
> prop2: value2
>   }
> };
> ```
>
> I have created a draft proposal and would love to hear any thoughts
> you have on the matter. You can find it on my GitHub, at the link
> below.
>
> https://github.com/lukem512/proposal-condition-property-definitions
>
> Kind regards,
> Luke
> ___
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
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Conditional object properties

[Luke Mitchell]

Hi all,

I often come across a situation where I wish to extend an object
(usually an argument for an API request) if a particular condition is
satisfied, such as the presence of a function parameter. Currently the
only way to do this is by assigning the object to a variable, checking
the condition using an `if` statement and then extending the object. I
am proposing the inclusion of an operator that allows a property to be
included, subject to a particular condition, inside the object
definition.

The operator looks like this:

```
let obj = {
  cond ? prop: value
};

```

The operator could also be used with a block statement, allowing
multiple properties to be included:

```
let obj = {
  cond ? {
prop1: value1,
prop2: value2
  }
};
```

I have created a draft proposal and would love to hear any thoughts
you have on the matter. You can find it on my GitHub, at the link
below.

https://github.com/lukem512/proposal-condition-property-definitions

Kind regards,
Luke
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