https://www.oktabit.gr/static/js/bootstrap_form_validation.js

1// Example starter JavaScript for disabling form submissions if there are invalid fields //
2(function() {
3  'use strict';
4  window.addEventListener('load', function() {
5    // Fetch all the forms we want to apply custom Bootstrap validation styles to
6    var forms = document.getElementsByClassName('needs-validation');
7    // Loop over them and prevent submission
8    var validation = Array.prototype.filter.call(forms, function(form) {
9      form.addEventListener('submit', function(event) {
10        if (form.checkValidity() === false) {
11          event.preventDefault();
12          event.stopPropagation();
13        }
14        form.classList.add('was-validated');
15      }, false);
16    });
17  }, false);
18})();