Yet another attempt at typed JS data

Michael Haufe tno at thenewobjective.com
Mon Feb 10 20:21:16 UTC 2020


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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