Fill blanks

function fillBlanks(){
  const ss = SpreadsheetApp.getActiveSpreadsheet()
  const sheet = ss.getSheetByName('Data')
  const values = sheet.getRange(1,1,sheet.getLastRow()).getValues().flat()

  for (let i = 0; i < values.length; i++){
    if(values[i] == ""){
      sheet.getRange(i+1,1).setValue('Test')
    }
  }

}