That already exists - `Array.from({ length: 4 }, () => whatever)` - I
assume that the hope is to have an array where it is *impossible* for it to
have the wrong "kind" of data, and a userland factory function wouldn't
provide that.On Sun, Feb 9, 2020 at 10:39 AM kai zhu <[email protected]> wrote: > > It's a bit of a mess to create an Array that is not holed and gets best > optimizations [1], and this proposal would like to address that exact case. > > could the performance issue be resolved more easily with a simple > static-function `Array.repeat(<length>, <repeater>)`? > > ```js > let structuredList; > structuredList = Array.repeat(4, function (ii) { > return { > index: 2 * ii + 1, > tags: [] > }); > /* > structuredList = [ > { index: 1, tags: [] }, > { index: 3, tags: [] }, > { index: 5, tags: [] }, > { index: 7, tags: [] } > ]; > */ > ``` > > the only time i can practically enforce the shape of a "StructuredArray" > is during element-insertion, > and a userland insertion/creation function would be just as effective as a > StructuredArray constructor. > > enforcing shapes during element deletions and updates are going to be hard > and likely just as confusing with StructuredArray as they are with regular > Array. > > also note that most javascript arrays need to be easily JSON-serialized > for message-passing > over-the-wire (commonly http) to external systems. > > -kai > > On Sat, Feb 8, 2020 at 3:46 AM Andrea Giammarchi < > [email protected]> wrote: > >> > having to retroactively add checks like... >> >> we already have typed arrays in JS so I don't think this would be any >> different >> >> > I _think_ that moderns virtual machines already did these optimisations >> despite there isn't a TypedArray like that. >> >> It's a bit of a mess to create an Array that is not holed and gets best >> optimizations [1], and this proposal would like to address that exact case. >> >> [1] https://v8.dev/blog/elements-kinds >> >> >> >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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