How to identify shared mailbox or folder in multi select

Question

The recommended way of identifying whether a mailbox or folder is shared is to check the shared properties on an item:

Office.context.mailbox.item.getSharedPropertiesAsync((result) => {

if (result.status === Office.AsyncResultStatus.Failed) {

console.error("The current folder or mailbox isn't shared.");

return;

}

const sharedProperties = result.value;

console.log(`Owner: ${sharedProperties.owner}`);

console.log(`Permissions: ${sharedProperties.delegatePermissions} `);

});

Since the item property is undefined in multi-select; how can it be checked when multiple mails are selected?