You need not to go from 1 up to n. You should find an optimal stopping point / upper-boundary where you can obtain all te divisors of n.

It is an efficient solution.

I am afraid you should read again the description. This test is the same in all languages.

Pleasure! Of course you might need a 'break' statement in some situations.

Oh man, while True is wonderful, thank you for showing it, I didn't know we can do such awesome thing.

Which might necessitate tiebreaking on indices, which you will then have to make available.

Sometimes implementing your own sort is not the worst solution.

Some really questionable design decisions have been made in JS ( EcmaScript ) historically, and this is one of them.

Recent specifications / implementations guarantee stable sorting, I think, but it's too late already and you can never fully trust sorting in JS. You'll always have to think about it.

Sort not being stable means you are not guaranteed how equal elements are ordered, and yes it's all over the place depending on engine or even it's version. To make sorting stable just define enough tiebreakers in a function passed to sort.

Interesting. A boolean is subtracted from a boolean?

...true = 1,
false = 0, correct?

Ahh, very interesting... took me a good while to wrap my head around this one. Javascript's sort is hard to understand at first, but powerful!

Does this mean we should be implementing our own sort algorithms in Javascript? Or does it now have a stable sort?

Nice palindrome algorithm!

Your code is very hard to read

console.log(start, end);
The value of the last fragment and the 3rd fragment are strongly hinted at in the example test cases. Plug those in first, then look at the expected results for the other tests.