I need to fetch recurrence data for appointments like Repeat, From, To fields. In addition, I also need to get daily, weekly, or monthly pattern details for my Outlook office Add-in while it is in compose mode.
In an Outlook web add-in when something is not available directly from Office.js library you can try to get access to those data using Exchange Web Services.
Fortunately, Office.js provides two ways to access EWS.
makeEwsRequestAsync
in Office.context.mailboxgetCallbackTokenAsync
from Office.Context.mailblox
to retrieve such a token. In this link you will find an example on how to use this technique to retrieve email attachments (not available in Office.js)To answer more precisely, the EWS seems to expose the information you need regarding recurrence, To etc. for appointments, see this link.