ISFORMULA
function ISFORMULA(arg1: ApiRange = null): number | string | booleanDescription
Checks whether a reference is to a cell containing a formula, and returns TRUE or FALSE.
Parameters
Is a reference to the cell you want to test. Reference can be a cell reference, a formula, or name that refers to a cell.
Returns
number | string | booleanTry It
const oWorksheet = Api.GetActiveSheet();
// Set the formula in cell B3
oWorksheet.GetRange("B3").SetValue("=SUM(5, 6)");
// Check if there is a formula in C3
var oFunction = Api.GetWorksheetFunction();
var result = oFunction.ISFORMULA(oWorksheet.GetRange("B3"));
oWorksheet.GetRange("C3").SetValue(result);