JavaScript regular expressions support word matcher escape sequences \w and \W instead of [a-zA-Z0-9_] and [^a-zA-Z0-9_], respectively, for regular expressions.
Those escape sequences are more concise than writing out the full character class sets.
This rule reports on any character sets that can be replaced by \w or \W word matchers.
If your codebase has an established convention of using explicit character classes for readability, or if you prefer consistency with patterns that use partial word character ranges (like [a-z0-9]), you might prefer to disable this rule.