custom-forminator-js-validation.php

<?php

add_action( 'wp_footer', function(){ ?>
<script>
	(function ($) {
		$(function () {
			$(document).on("after.load.forminator", function (e, id) {
				var cvalinput = $('.custom-validate input');

				let regx = /^[0-9]*$/;

				$(cvalinput).bind('focusout keyup ', function () {

					if (regx.test($(this).val()) || $(this).val() === '') {

						$(this).parent().parent().find('label.forminator-label--validation').remove();

					} else {

						if (!$(this).parent().parent().find('label.forminator-label--validation').length) {

							$(this).parent().parent().append('<label class="forminator-label--validation">Only alphanumeric characters are allowed.</label>');

						}

					}
				});
			});
		});
	})(window.jQuery);
</script>
<?php }, 21); ?>