why don't you use ORDER BY?

Already fixed

How did you solve it? I have it working on node, but not in codewars?

Agree. Schema is subject to change, so developers better specify the column names.

It does unless ES6 tail-call optimization takes effect. In this implementation, it does not take effect, because function call to map is not in tail-call position. See here: http://www.2ality.com/2015/06/tail-call-optimization.html

Does it not create a burden on memory with long list because of recursion and call stack ?

Yes - the function 'map' calls itself with the next node in the list. More info here

Is what you did called recursion? (using a function inside of itself)

I agree. Wording in this kata is an issue

I believe there's an issue with JS small cases:
number = 4, expected 0, but should expect 3 instead, number = 6, expected 3, but really should expect 8 (3 + 5)

Often this works for this problem:

1. Copy your solution-code
2. Refresh the whole site
3. Try again to submit

It is not a bug of the kata but a CW bug, report it : Forum -> Bugs.