问如何按所选列将google sheet导出为CSV

EN

function menu() {
 var ui = SpreadsheetApp.getUi();
 var menu = ui.createMenu('Menu');
 var item = menu.addItem('PICC', 'picc');
 var item2 = menu.addItem('Export to CSV', 'csv');
 item.addToUi();
 item2.addToUi()
 };

 function onOpen() {
   var ss = SpreadsheetApp.getActiveSpreadsheet();
   var csvMenuEntries = [{name: "Download Primary Time File", functionName: "saveAsCSV"}];
  //ss.addMenu("Creating a Timetable", csvMenuEntries);

  var ui = SpreadsheetApp.getUi();
  var menu = ui.createMenu('Menu');
  var item = menu.addItem('PICC', 'picc');
  var item2 = menu.addItem('Export to CSV', 'csv');
  item.addToUi();
  item2.addToUi()
  };

  function saveAsCSV() {
    var ss = SpreadsheetApp.getActiveSpreadsheet(); 
    var sheet = ss.getSheetByName("sheet1");
  // create a folder from the name of the spreadsheet
    var folder = DriveApp.createFolder(ss.getName().toLowerCase().replace(/ /g,'_') + '_csv_' + new Date().getTime());
  // append ".csv" extension to the sheet name
     fileName = sheet.getName() + ".csv";
  // convert all available sheet data to csv format
     var csvFile = convertRangeToCsvFile_(fileName, sheet);
  // create a file in the Docs List with the given name and the csv data
     var file = folder.createFile(fileName, csvFile);
  //File downlaod
    var downloadURL = file.getDownloadUrl().slice(0, -8);
    showurl(downloadURL);

   }

   function showurl(downloadURL) {
     var app = UiApp.createApplication().setHeight('60').setWidth('150');
    //Change what the popup says here
     app.setTitle("Your timetable CSV is ready!");
     var panel = app.createPopupPanel()
     //Change what the download button says here
     var link = app.createAnchor('Click here to download', downloadURL);
     panel.add(link);
     app.add(panel);
     var doc = SpreadsheetApp.getActive();
     doc.show(app);
     }

     function convertRangeToCsvFile_(csvFileName, sheet) {
     // get available data range in the spreadsheet
     var activeRange = sheet.getDataRange();
     try {
           var data = activeRange.getValues();
           var csvFile = undefined;

     // loop through the data in the range and build a string with the csv data
        if (data.length > 1) {
            var csv = "";
        for (var row = 1; row < data.length; row++) {
        for (var col = 0; col < data[row].length; col++) {
        if (data[row][col].toString().indexOf(",") != -1) {
             data[row][col] = "\"" + data[row][col] + "\"";
          }
         }

         // join each row's columns
         // add a carriage return to end of each row, except for the last one
        if (row < data.length-1) {
           csv += data[row].join(",") + "\r\n";
         }
            else {
               csv += data[row];
               }
         }
            csvFile = csv;
       }
       return csvFile;
      }
         catch(err) {
         Logger.log(err);
         Browser.msgBox(err);
      }
    }