CODE EXAMPLE FOR TYPESCRIPT

google sheets app script get last cell has value with empty cells

const ss = SpreadsheetApp.getActive();
const sh = ss.getSheetByName('Sheet1')
const lrow = sh.getLastRow();
const Avals = sh.getRange("A1:A"+lrow).getValues();
const Alast  = lrow - Avals.reverse().findIndex(c=>c[0]!='');