<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css"> <script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script> <script src="//code.jquery.com/jquery-1.11.1.min.js"></script> <!------ Include the above in your HEAD tag ----------> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous"> <div class="container"> <div class="jumbotron"><h2>Buy a domain name</h2> <div class="row"> <form method="post" name="formDomain" id="formDomain" action="?page=ajaxcheck"> <div class="input-group col-xs-5"> <input class="form-control form-control-lg" name="domain" id="domain" autocomplete="off" type="text" required="true"> <select name="dot" id="dot" class="custom-select form-control-lg dropdown-toggle"> <option value="fr">.fr</option> <option value="com">.com</option> <option value="eu">.eu</option> <option value="org">.org</option> </select> </div><br /> <input value="Try" type="submit" id="tryDomain" name="tryDomain" class="btn btn-primary btn-lg btn-block"> </form> </div> </div> </div> <script src="https://code.jquery.com/jquery-2.1.4.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>

$(document).ready(function() { $('#formDomain').on('keyup keypress blur change', function(e) { $('input[name=tryDomain]').val('Try ' + $('#domain').val() + '.'+$('#dot option:selected').val()); }); });