Description Suggestion JavaScript
If the input array contains anything other than integers, then return undefined.
Iterate through the array cubing each element meaning e³ or e*e*e.
Grab only the odd cubed elements and return the sum.

The returning undefined aspect of this Kata is a hindrance and it's problematic tbh

cool

It returns 0, as it is the sum of cubed odd numbers, where -3 cubed is -27 so it is infact:

-3 * -3 * -3 = -27 and 3 * 3 * 3 = 27 therefore -27 + 27 = 0

Why would this test suppose to return 0 ?

Test.assertEquals(cubeOdd([-3,-2,2,3]), 0);

3 * 3 * 3 = 27?

Find the sum of the odd numbers within an array, after cubing the initial integers

but

The function should return undefined/None/nil/NULL if any of the values aren't numbers

so, what if number is float (not equal to its integer part)? It is a number, but it is not an odd number (even or odd are defined only for integer)
Seems like, text might be
"The function should return undefined/None/nil/NULL if any of the values aren't integers"
and there must be any test with float (at least there are none of those in python version)

For JavaScript, no. For TypeScript, yes.

Hm I tried to put this with null instead of 0, anyone know why this works over null?

Use spoiler flag next time, please.

The name is repeatStr. It's called arrow function expression. It's missing const or let tho.