Google apps script to export an individual sheet as csv file

export-named-sheet-as-csv.gs

/*
 * script to export data of the named sheet as an individual csv files
 * sheet downloaded to Google Drive and then downloaded as a CSV file
 * file named according to the name of the sheet
 * original author: Michael Derazon (https://gist.github.com/mderazon/9655893)
*/

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

function saveAsCSV() {
  var ss = SpreadsheetApp.getActiveSpreadsheet(); 
  var sheet = ss.getSheetByName('Primary Time');
  // 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 = 0; 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);
  }
}

Hello, in my case I got a correct downloadURL but only working if I manually introduce it to the browser. However if url is called within the Apps Script (showModalDialog()) I got initial 303 status redirection followed up 18 302 status redirection since I end up with ERR_TOO_MANY_REDIRECTS. Any clue?

• Folder is created OK
• Csv file is created OK
• URL file is created OK
• By changing folder permissions is not working aswell.

Other approach I did--> If I just copy the GET request from manually get File > Download > CSV in the browser works but within the dialog got this error:

Thanks!