Add displayMessageFormAsync to office.js so that it accepts a callback
In the current displayMessageForm, when a newly created item.itemId is specified there is a high probability of failure.
When displayMessageForm form fails the caller is never made aware.
Allowing a callback to be passed would permit the request to handle the failure.
The ability to display a message form should permit a callback to be passed that expects an indicator of success/failure for the request.
we have now all the display APIs in Preview! please check our documentation here