Not a kata issue, your code does not comply to below

Note: if multiple products have the same revenue, order them according to their original positions in the input list.

I agree with (1), though you won't always be able to achieve it of course, but I think function should break when passed ( 5 ), unless the specs specifically say to handle both ([int]) and (int,int,..) ( which I would consider bad design ).

I actually like strong, static typing better than everything JS allows.

const ouroboros = (a, n) => ...

That's not a valid solution. You're doing a completely different thing from what is asked.

@PolyDevil: I've added 'ba' => ['b', 1] to JS test cases. The original Python had such a test case.

Nice catch! https://www.codewars.com/kata/reviews/5990bc7a10038ae59f000078/groups/5f428a9004f716000131e1a6

Several mixed topics, in there.

• issue/not issue: the label, on CW, is reserved to problem in the kata itself (wrong tests, wrong code, wrong description, ...). In your case, the correct label would actually be "question".
• Node.js sort the strings accordingly to the very specifications of this or that node.js version. Here, you're stuck with the available versions, so you have to deal with the specifications of those sort functions. And in those, [].sort isn't "stable". You can consider it a problem in JS (I'd actually agree about that x) ), but it's still not a kata issue.
• on your side, you have to deal with that problem. You cannot rely on an unexisting feature to actually solve the task in a specific context (hence sort isn't stable), so you have to find another way to solve it. Hint: do one single pass on the string or pick an external library.

It works in chrome. Probably on latest node as well.

that's possible, but not the current context, so... ;o

note: read this?

not an issue. Your code isn't following the specifications:

If there are two or more characters with the same l return the first in order of appearance

This has nothing to do with alphabetical order.

Well, sometimes, you might comment: nice solution or something. Then, everyone can see it.

Well, not all posts in a solution contain spoilers. It's just the way it works.

Please, use spoiler flag, your post was visible in the homepage discourse.