1658308 - Implement the .at() proposal

Status: RESOLVED FIXED

(Core :: JavaScript: Standard Library, enhancement, P3)

Description

[Yulia Startsev [:yulia]]

https://github.com/tabatkins/proposal-item-method

The proposal is currently on Stage 2.

Comment 1

[Tom S [:evilpie]]

Attachment: Bug 1658308 - Implement Array.prototype.item and %TypedArray%.prototype.item in Nightly. r?anba

Comment 2

[Tom S [:evilpie]]

Attachment: Bug 1658308 - Constant folding for boxed MToNumberInt32 inputs. r?jandem

I noticed this while looking at the iongraph for a simple item call
with a constant parameter. The input is boxed because before optimization
it is apparently an untyped PHI.

Depends on D90732

Comment 3

[Tom S [:evilpie]]

Attachment: Bug 1658308 - Some basic item tests. r?anba

I only added some very basic tests here under the assumption that
test262 is going to add a broader range of tests.

Depends on D90732

Comment 4

[Tom S [:evilpie]]

Apparently the item proposal advanced to Stage 3, but with String.prototype.item still included. However there seems to be some agreement that this should probably not be part of the proposal at least without a better justification: https://github.com/tc39/proposal-item-method/issues/20

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f43cdaab8611
Implement Array.prototype.item and %TypedArray%.prototype.item in Nightly. r=anba
https://hg.mozilla.org/integration/autoland/rev/cd81e5f20c95
Some basic item tests. r=anba
https://hg.mozilla.org/integration/autoland/rev/37ddb997bbf6
Constant folding for boxed MToNumberInt32 inputs. r=jandem

Comment 6

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/f43cdaab8611
https://hg.mozilla.org/mozilla-central/rev/cd81e5f20c95
https://hg.mozilla.org/mozilla-central/rev/37ddb997bbf6

Comment 7

[Kagami Rosylight [:saschanaz] (they/them)]

Now stage 3: https://github.com/tc39/proposals/commit/67f65774a14d83b0e47c465649bad3a72b4eb64b

Comment 8

[Tom S [:evilpie]]

Attachment: Bug 1658308 - Implement String.prototyp.item in Nightly. r?anba

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5bc024234126
Implement String.prototyp.item in Nightly. r=anba

Comment 11

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/5bc024234126

Comment 12

[Tom S [:evilpie]]

André pointed out that we will need to handle Array.prototype[@@unscopables] at some point: https://github.com/tc39/proposal-item-method/issues/30.

Comment 13

[Tom S [:evilpie]]

I opened another issue for the web compatibility issue with Yui2 that broke bugzilla: https://github.com/tc39/proposal-item-method/issues/31

Comment 14

[Andreea Pavel [:apavel]]

Backed out for the reason mentioned above: https://hg.mozilla.org/mozilla-central/rev/b8d82fc2371e020ade6144aa7f5892bf979761bb

Comment 15

[Tom S [:evilpie]]

Attachment: Bug 1658308 - Backout Array.prototype.item and %TypedArray%.prototype.item.

There are too many web compatibility issues. Keeping this on Nightly is not going
to be useful.

Comment 16

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8b1680a2b965
Backout Array.prototype.item and %TypedArray%.prototype.item.

Comment 17

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/8b1680a2b965

Comment 18

[Tom S [:evilpie]]

Attachment: Bug 1658308 - Implement the .at() proposal. r?jandem

Comment 19

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/aac43ddfdb12
Implement the .at() proposal. r=jandem

Comment 20

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/aac43ddfdb12

Comment 21

[Alexandre Folle de Menezes]

It doesn't seem to work with this test from http://kangax.github.io/compat-table/esnext/ :
return [
'Int8Array',
'Uint8Array',
'Uint8ClampedArray',
'Int16Array',
'Uint16Array',
'Int32Array',
'Uint32Array',
'Float32Array',
'Float64Array',
'BigInt64Array',
'BigUint64Array'
].every(function (TypedArray) {
var Constructor = globalThis[TypedArray];
if (typeof Constructor !== 'function') {
return true;
}
var arr = new Constructor([1, 2, 3]);
return arr.at(0) === 1
&& arr.at(-3) === 1
&& arr.at(1) === 2
&& arr.at(-2) === 2
&& arr.at(2) === 3
&& arr.at(-1) === 3
&& arr.at(3) === undefined
&& arr.at(-4) === undefined;
});

Should it?

Comment 22

[Tom S [:evilpie]]

The error is "can't convert 1 to BigInt". Coming from doing new BigInt64Array([1, 2, 3]) (via new Constructor ..) So the test is wrong and the failure is unrelated to at.

Comment 23

[Chris Mills [:cmills]]

Setting this to dev-doc-complete. @rumyra documented it, the details are all available at https://github.com/mdn/content/issues/307, and the pages should appear on MDN in the next 24 hours or so.