In case you're interested, I created a code golf version of this kata:
https://www.codewars.com/kata/6243819a58ad06b6c663d32b - currently python only

(you may add it to the description)

This was super cool! I'm going to start making my own chess interface after this. Then I can fiddle with my own engine too!

This is a confusing kata.

h1 h2 h3 h4 h5 h6 h7 h8
g1 g2 g3 g4 g5 g6 g7 g8
f1 f2 f3 f4 [f5] f6 f7 f8
e1 e2 e3 e4 e5 [e6] e7 e8
d1 d2 d3 [d4] d5 d6 d7 d8
c1 c2 c3 c4 c5 [c6] c7 c8
b1 b2 b3 b4 [b5] b6 b7 b8
[a1] a2 a3 a4 a5 a6 a7 a8

8 possible moves

Added.

Fixed.

It is not mentioned that the result should be sorted.

Moving to an issue.

Javascript, Python translations with random tests, please check and approve :-)

You need to update the description informing us that the result needs to be sorted :-)

Maybe add an image of a chessboard layout?

Needs Random Tests.

if you change your flag on your regex to be 'gi' then you don't need both uppercase and lowercase letters:

/a|e|i|o|u/gi

will match all vowels