Yet another attempt at typed JS data

Andrea Giammarchi andrea.giammarchi at gmail.com
Mon Feb 10 23:25:58 UTC 2020


> Given your history I know better than to assume what you know…

I've no idea what you are talking about, but this should be no venue for
these kind of answers.

My history in this thread explained the proposal, the intent, and linked
all the facts around it, and before your pointless answer, so please keep
your biases for yourself.

Thank you.


On Mon, Feb 10, 2020 at 10:13 PM Michael Haufe <tno at thenewobjective.com>
wrote:

> Given your history I know better than to assume what you know…
>
>
>
> The definition of sparse in the spec (while not explicitly in its own
> section) is straightforward.
>
>
>
> V8’s inability or unwillingness to perform a safe “upcast” internally to
> an appropriate tag doesn’t seem to provide enough weight to introduce a new
> construct.
>
>
>
>
>
> *From:* Andrea Giammarchi <andrea.giammarchi at gmail.com>
> *Sent:* Monday, February 10, 2020 2:26 PM
> *To:* Michael Haufe <tno at thenewobjective.com>
> *Cc:* Bergi <a.d.bergi at web.de>; es-discuss at mozilla.org
> *Subject:* Re: Yet another attempt at typed JS data
>
>
>
> Great, now maybe you also read how it works behind the scene, and debug
> properly to understand that every array is holey, including the latter one,
> to date.
>
>
>
> https://v8.dev/blog/elements-kinds
>
>
>
> Please, let's assume for a second I knew what I was talking about, when
> I've said it's a mess to not have holey arrays, thanks.
>
>
>
> On Mon, Feb 10, 2020 at 9:21 PM Michael Haufe <tno at thenewobjective.com>
> wrote:
>
> Array(3)
> //  [empty × 3]
>
> Array(3).fill()
> // [undefined, undefined, undefined]
>
> Array(3).fill('whatever')
> // ["whatever", "whatever", "whatever"]
>
>
> -----Original Message-----
> From: es-discuss <es-discuss-bounces at mozilla.org> On Behalf Of Bergi
> Sent: Monday, February 10, 2020 1:27 PM
> To: es-discuss at mozilla.org
> Subject: Re: Yet another attempt at typed JS data
>
> Hello!
>
> > Unfortunately, `Array.from({ length: 4 }, () => whatever)` produces a
> > holey array
>
> Does it? But really, if the performance difference betweeen HOLEY and
> PACKED arrays were large enough to be relevant[1], the engine programmers
> would certainly already have optimised all those trivial cases where an
> array is filled gradually to produce the more efficient representation.
>
> kind regards,
>  Bergi
>
> [1]: it probably isn't:
> https://stackoverflow.com/questions/54481918/#comment95848513_54485509
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