var formIsValid = false;

$(document).ready(function () {
    $('input[type=radio]').change(
            function () {
                var clickedRadio = this;
                var afterClickedRadio = false;

                var radios = document.querySelectorAll('input[type=radio]');
                for (i = 0; i < radios.length; ++i) {
                    var radio = radios[i];
                    if (radio == clickedRadio) {
                        afterClickedRadio = true;
                        continue;
                    }
                    if (!afterClickedRadio && clickedRadio.value == 'left' && radio.value == 'left') {
                        radio.checked = true;
                    }
                    if (afterClickedRadio && clickedRadio.value == 'right' && radio.value == 'right') {
                        radio.checked = true;
                    }
                }
                formIsValid = $('#form')[0].checkValidity();
                if (formIsValid) {
                    $('#confirm').prop('disabled', false);
                }
            }
    );

$('#confirm').click(function() {
    var radios = document.querySelectorAll('input[type=radio]');

    for (i = 0; i < radios.length; ++i) {
        var radio = radios[i];
        if (radio.value == 'right' && radio.checked) {
            $('switching_point').val(radio.dataset.amount);
            break;
        } else {
            $('switching_point').val(9999);
        }
    }
    return false;
});

    });