Cross posting from our Dev blog:
Custom functions (similar to "user-defined functions", or "UDFs") are JavaScript functions that you can build as part of your add-in. Users can see and run those functions in Excel alongside built-in functions like =SUM or =VLOOKUP. The best part is that those same functions will work everywhere add-ins do: on your PC, Mac, and iPad, and even in Excel Online. But for now the Developer Preview is only available on Windows.
Published Dec 15, 2017
Version 1.0Olaf Hubel
Former Employee
Joined June 24, 2016
Excel Blog
Subscribe to the Excel Blog to get the latest product announcements and updates