Regex Domain Name Wildcard. No regex just wildcard domain names eg. Catch-all Domain Wildcard Suffix.
Used in regular expressions these are simply whole words that are composed only of alpha characters A to Z and a to z. The wildcard an regular-expression strings are test strings. I think youd better use some other ways combined with the class you showed to check the URL.
In some card games the Joker is a wildcard and can represent any card in the deck.
The domain name should not start or end with hyphen - eg. In cPanel navigate to the Subdomains icon in the Domains section. For my use case where its the domain itself that I want to be wildcarded ie. Whatsoever I will be using the primary domain at all the times.