return false;

$('body').on('beforeSubmit', ‘form#formId', function () {
     var form = $(this);
     // return false if form still have some validation errors
     if (form.find('.has-error').length) {
          return false;
     }
     // submit form
     $.ajax({
          url: form.attr('action'),
          type: 'post',
          data: form.serialize(),
          success: function (response) {
               // do something with response
          }
     });
     return false;
});