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function sortSheets(){
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheetNameArray = [];
  var sheets = ss.getSheets();
  for (var i = 0; i < sheets.length; i++) {
    sheetNameArray.push(sheets[i].getName());
  }
  sheetNameArray.sort();
  for( var j = 0; j < sheets.length; j++ ) {
    ss.setActiveSheet(ss.getSheetByName(sheetNameArray[j]));
    ss.moveActiveSheet(j + 1);
  }
}