如果属性没有值，则返回Wix SetProperty

$w('#elementId').setProperty('propertyName', value);

$w.onReady(function () {
    $w('#myElement').getProperty('myProperty')
        .then((value) => {
            if (value === undefined) {
                $w('#myElement').setProperty('myProperty', 'defaultValue')
                    .then(() => {
                        console.log('Property set successfully');
                    })
                    .catch((error) => {
                        console.error('Failed to set property:', error);
                    });
            } else {
                console.log('Property already has a value:', value);
            }
        })
        .catch((error) => {
            console.error('Failed to get property:', error);
        });
});