 apply custom Bootstrap validation styles to
          var forms = document.getElementsByClassName('needs-validation');

          // Loop over them and prevent submission
          var validation = Array.prototype.filter.call(forms, function(form) {
            form.addEventListener('submit', function(event) {
              if (form.checkValidity() === false) {
                event.preventDefault();
                event.stopPropagation();
              }
              form.classList.add('was-validated');