Intent to ship: change-array-by-copy

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Tim Chevalier

Mar 20, 2023, 5:42:44 PM3/20/23

As of 3/31/2023, I intend to submit a pull request to turn the change-array-by-copy feature on by default. It has been developed behind the javascript.options.experimental.enable_change_array_by_copy preference. It is shipping unflagged in Safari/JavaScriptCore and Chrome/v8.

The change-array-by-copy JavaScript feature introduces four new methods on Arrays and TypedArrays that do non-destructive transformations on arrays (returning a copy of the array). Code examples can be found at . The proposal is complete and has been merged into the ECMAScript spec ( )

The tracking bug for shipping this feature unflagged to Nightly is

I don't think a previous "intent to prototype" email was sent. As far as I know, this feature doesn't require any special DevTools support; I'm also not aware of any security or privacy concerns. Tests for each of the four new methods (toReversed, toSorted, toSpliced, and with) are included in test262. ( and ).



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