proposal-private-methods VS proposal-change-array-by-copy

But with the new ECMAScript class fields proposal we can do this easily and gracefully by using private fields as seen below:

Private instance methods and accessors Class Public Instance Fields & Private Instance Fields Static class fields and private static methods

Don't forget that abomination of syntax which is https://github.com/tc39/proposal-private-methods

This is not currently true. But there are proposals, currently in stage 3 for allowing this.

Private instance methods and accessors

There is a proposal for private methods but its not yet standard. However, they are currently supported in chromium browsers and in firefox after enabling a flag. These, however, only work using the class syntax, not in constructor functions like that used in your example.

The new change array by copy methods (ES2023) will also work with tuples. So while you can't

Change Array by Copy

Stage 3 Change array by copy proposal offers methods like sortTo() that return a new array instead of mutating the original.

Note: there's a stage 3 proposal that introduces copy = arr.toSorted().

Change Array by Copy: Provides additional methods on Array.prototype and TypedArray.prototype to enable changes on the array by returning a new copy of it with the change.

The proposal is described here, with the other methods being:

Proposal, Polyfill

You're unlikely to see any new methods being added to JavaScript's Array that would modify an array in place like reverse() and sort() do. In fact some of the new methods that are being added are versions of reverse() and sort() (and splice()) that create copies rather than modifying the originals. Read more about them here: Proposal: Change Array by copy.

Since cloning is so common, a new specification has been written which has reached stage 3, which will give us a host of new ways to copy and then change an array. This proposal is called the "Change Array by Copy" proposal. Let's take a look at how it works.