Enumerations

Added in 1.10 (2019 October)

Added in 1.9 (2019 May)

Added in 1.8 (2018 September)

Added in 1.7 (2018 May)

These did appear in the Shared API but have since been removed

CustomFunctionValueType (Excel)

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Excel.CustomFunctionValueType.string - A string type in Excel. 
Excel.CustomFunctionValueType.Number ("number") - A number type in Excel, such as dates, currencies, and other numbers. 
Excel.CustomFunctionValueType.Invalid ("invalid") - An invalid type in Excel. 
Excel.CustomFunctionValueType.Boolean ("boolean") - A boolean type in Excel. 
Excel.CustomFunctionValueType.IsoDate ("isodate") - An ISO Date in Excel. 

CustomFunctionDimensionality (Excel)

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Excel.CustomFunctionDimensionality.Scalar ("scalar") - A single cell's value in Excel. 
Excel.CustomFunctionDimensionality.Matrix ("matrix") - A range of values in Excel, with one or more rows, and one or more columns. In JavaScript, a range is implemented as an array, where each array element is another array.