Using reluctant quantifiers (also known as lazy or non-greedy quantifiers) in patterns can often lead to needless backtracking, making the regex
needlessly inefficient and potentially vulnerable to catastrophic backtracking.
Particularly when using .*? or .+? to match anything up to some terminating character, it is usually a better idea to
instead use a greedily or possessively quantified negated character class containing the terminating character. For example <.+?>
should be replaced with <[^>]++>.
Noncompliant code example
/<.+?>/
/".*?"/
Compliant solution
/<[^>]++>/
/"[^"]*+"/
or
/<[^>]+>/
/"[^"]*"/
Exceptions
This rule only applies in cases where the reluctant quantifier can easily be replaced with a negated character class. That means the repetition has
to be terminated by a single character or character class. Patterns such as the following, where the alternatives without reluctant quantifiers are
more complicated, are therefore not subject to this rule:
/<!--.*?-->/
-/\*.*?\*/-
