Editorial: Rename predicate function parameter of Array methods

[shvaikalesh]

This change makes naming more descriptive and consistent with Array.prototype.find and Array.prototype.findIndex.

b662dff is a follow-up of #1411.
See also #1786.

[bakkot]

A lot of these names make it into documentation; I am a little hesitant to change them.

[devsnek]

I really like this change

[ljharb]

I am highly concerned about the documentation and polyfill churn this change will cause.

[shvaikalesh]

I've checked MDN: for Array methods, first function parameter is always a callback (even for newer find and findIndex). Is there a docs that precisely follow the names in spec?

[bakkot]

TypeScript's typedefs, for example, which I believe are used for integration in some editors (and which therefore surface these names to users of those editors).

[devsnek]

what happens if those names change or don't change?

[mathiasbynens]

I’ve always considered the parameter names used in the spec to be implementation details (of the spec), similar to how the names of variables in spec algorithm steps are implementation details. Documentation can use any names whatsoever.

[michaelficarra]

I like it. My only concern would be on another spec having a normative reference to one of these names, such as by specifying a change/insertion of algorithm steps that refer to the name. But barring somebody providing an example of this dependency, I'm in favour of the change.

[DanielRosenwasser]

We might just change it in TypeScript because we like the change ourselves; but to have the .d.ts files align, is there a reason not to apart from auto-generation churn?