The random tests for javascript show this:
input key was: xrvgxfnia , input text was: pDHt- trVv!batDINVZrv-&eYu
expected: jDDe- ndZe!s[t@THHDam-&Yq
Here you can see that 'a' is turned into '[', 'D' is turned into '@' and 'e' is turned into ''.
As the task mentions to respect cases and keep special characters, spaces, numbers and punctuation, I can only conclude that the tests do not do what the description says. This is probably same issue as reported below.

• It's not clear from the example in the description whether the additional steps of [0, -1, -2, -3] are based on the iteration number, or the key characters
• No fixed tests
• The tests shouldn't log anything
• The reference solution does not correctly adjust characters to [a; z] and [A; Z] ranges
• A vigenere cipher with each key-character shifted by key length is still a vigenere cipher, so it's a duplicate