var username = $('#username'); var hint = $('#usernamehint'); function fixUsername() { var s = username.val(). toLowerCase(). replace(/[^0-9a-z\-_]/g, ""); if (s !== username.val()) username.val(s); if (s.length > 0) hint.text("http://bitlove.org/" + s); else hint.text(""); } username.bind('change', fixUsername); username.bind('input', fixUsername); username.bind('keyup', fixUsername);