GH-39131: [JS] Add at() for array like types

[domoritz]

Arrays in JavaScript have at instead of get so here we are making our arrays more consistent.

This PR still maintains support for get but deprecates it. We can remove get after one version of supporting both.

• GitHub Issue: [JS] Implement at for array like types #39131

[github-actions]

⚠️ GitHub issue #39131 has been automatically assigned in GitHub to PR creator.

[domoritz]

@trxcllnt and I agreed offline to wrap indexes accesses so that any index is valid. The behavior in js is to only index -length ... length and return undefined otherwise but that seems less consistent than to just always wrap. Also, the types can be composer since we never return undefined.

[trxcllnt]

-1 for renaming get() to at(). I'm fine adding at(), but get() and set() are equivalent to accessing an element by subscript index, e.g. x = xs[0] and xs[0] = x.

We've tried to get rid of them in the past in favor of proxies, but they're still the fastest way to access elements besides enumerating the data directly (via iterators or arraybuffers).

[domoritz]

I see. So you are saying we should keep the get visitor and just make at a method that calls get?

Isn't at as I implemented equivalent to get within the valid range of values? Do we want to keep get because it's slightly faster than at?

[domoritz]

Redone in #40730