Spreadsheet =SUMPRODUCT(A$1:A$39*(B$1:B$39=C1))

Webix JS
#1

Is there an equivalent in webix without custom functions. I know I am pushing the boundaries but this would be useful.

#2

This isn’t important to me. I can write a custom function in Webix. Similarly for Excel (XLL)

#3

Here is full list of methods supported by Webix Spreadsheet 9.0

It does include SUMPRODUCTS