I have successfully created some code to extract data from a 2D array using A1 notation. Handy to avoid multiple calls to GAS services whit ordinary getRange calls.
While the code perfectly works in javascript, it throws an error in Google Apps Script upon saving.
The offending code is:
return matrix.slice(startRow, endRow + 1).map(i => i.slice(startCol, endCol + 1))
GAS seems rejecting code in the .map function.