A regex should never include a repetitive pattern whose body would match the empty string. This is usually a sign that a part of the regex is
redundant or does not do what the author intended.
Noncompliant code example
"/(?:)*/" // same as the empty regex, the '*' accomplishes nothing
"/(?:|x)*/" // same as the empty regex, the alternative has no effect
"/(?:x|)*/" // same as 'x*', the empty alternative has no effect
"/(?:x*|y*)*/" // same as 'x*', the first alternative would always match, y* is never tried
"/(?:x?)*/" // same as 'x*'
"/(?:x?)+/" // same as 'x*'
Compliant solution
"/x*/"
