Bug report

There is no TypeScript definition for defineFunction and no custom functions can be created in TypeScript context using the approach demonstrated in this Custom functions article.

Reproduction of the problem

Try defining a new function using:
kendo.spreadsheet.defineFunction("Mask",mask).args(maskArgs)

Current behavior

The following error appears:

Propery "defineFunction" does not exist on type 'typeof spreadsheet'

Expected/desired behavior

There shouldn't be any errors

Environment

• Kendo UI version: 2019.3.1023
• jQuery version: x.y
• Browser: [all]