boolean isValid = (email != null ? email.contains("@") : false) the goal of client-side validation is to ensure that you can actually make that network call to

boolean isValid = (email != null ? email.contains("@") : false) the goal of client-side validation is to ensure that you can actually make that network call to do a real validation. the rfc is so complicated it's not even worth getting into this business, as evidenced by op's regex. would love to see some unit tests for that thing.