CODE EXAMPLE FOR JAVASCRIPT

apps script get last row with data

  var cur_ss = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var data = cur_ss.getDataRange().getValues();
  
  var Avals = cur_ss.getRange("B9:B").getValues();
  var Alast = Avals.filter(String).length;
  return (Alast + 9);