eal-time validation errors from the card Element.
        card.addEventListener('change', function (event) {
            var displayError = document.getElementById('card-errors');
            if (event.error) {
                displayError.textContent = event.error.message;
            } else {
                displayError.textContent = '';
            }
        });
        // Handle form submission.
        var form = document.getElementById('payment-form');
        form.addEventListener('submit', function