I think I found the answer:
How to open Excel workbook using data from a service call in Excel Javascript API (Add-in)
I am in the process of "porting" some old code running in Excel desktop (365) - some VB code that gets data from a server and then writes the file to a temp file on local disk and then makes a call to open the workbook:
Set tempBook = Workbooks.Open(tempName, True, True, , , , True, , , , , , False)
To open the workbook from the temp file.
The full API is:
Function Open(Filename As String, [UpdateLinks], [ReadOnly], [Format], [Password], [WriteResPassword], [IgnoreReadOnlyRecommended], [Origin], [Delimiter], [Editable], [Notify], [Converter], [AddToMru], [Local], [CorruptLoad]) As Workbook
Member of Excel.Workbooks
I am now building an add-in for Excel Javascript API (currently targeting Web), and need to know the moral equivalent to Workbooks.Open in the new API. Is there a method to retrieve open a Workbook using a stream or local file? Is the HTML5 Filesystem API supported?
Thanks