Alternation is used to match a single regular expression out of several possible regular expressions. If one of the alternatives is empty it would
match any input, which is most probably a mistake.
Noncompliant code example
/Jack|Peter|/.test('John'); // Noncompliant - returns 'true'
/Jack||Peter/.test('John'); // Noncompliant - returns 'true'
Compliant solution
/Jack|Peter/.test('John'); // returns 'false'
Exceptions
One could use an empty alternation to make a regular expression group optional. Rule will not report on such cases.
/mandatory(-optional|)/.test('mandatory'); // returns 'true'
/mandatory(-optional|)/.test('mandatory-optional'); // returns 'true'
However, if there is a quantifier after the group the issue will be reported as using both | and quantifier is redundant.
/mandatory(-optional|)?/.test('mandatory'); // Noncompliant - using both `|` inside the group and `?` for the group.
