According to specs: Replace every letter in the string with the letter following it in the alphabet (c becomes d, z becomes a). Then capitalize every vowel in this new string (a, e, i, o, u) and finally return this modified string.

If the input string contains a capital letter ("Argument goes here" for example), the capital letters will not be modified as they are not contained by the alpha string "abcdefghijklmnopqrstuvwxyz".

Output for "Argument goes here" is "AshvnfOU hpft Ifsf" but should be "BshvnfOU hpft Ifsf".

This could be solved by modifying alpha and newalpha as follows:
var alpha = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
var newAlpha = "bcdEfghIjklmnOpqrstUvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZA";