TypeError: Cannot find function hasnext in object FolderIterator

I am trying to copy my some of the folders in google drive using google scripts and I get error on the topFolder.hasnext() line .I've already seen the answers of these questions and they didn't help :

TypeError: Cannot find function hasNext in object (Folder with date ID)

Why cannot Object FolderIterator find function getId?

TypeError: Cannot find function hasNext in object

My code is like this :

function onOpen(){
   SpreadsheetApp.getUi()
   .createMenu("Hello there  Click Me")
   .addItem('Copy the files and folder to your specified dir','fCopier')
   .addToUi()
    }

var thisSheet = SpreadsheetApp.getActiveSheet();
var folderId = thisSheet.getRange("B1").getValue();
var folderId = folderId.toString().trim();
var ttopFolder = DriveApp.getFolderById(folderId);
var topFolder = ttopFolder.getFolders();
var desFolder = thisSheet.getRange("B3").getValue();
var desFolder = desFolder.toString().trim();
var reallyDesFolder = DriveApp.getFolderById(desFolder);
var forFilelist = ttopFolder.getFiles();




  var topper = [];
  while(topFolder.hasnext()){
    topper.push(topFolder.next());
  }



  var filer = [];
  while(forFilelist.hasNext()){
    filer.push(forFilelist.next())
  }

function fCopier(){
  for (var i = 0; i < topper.length; i++) {
    var finalfolders = topper[i];
  }
  var folderCompleto = reallyDesFolder.createFolder(finalfolders);

for(var j =0; j<filer.length; j++){
  var finalfiles = filer[j];
  }
var fileCompleto = finalfiles.makeCopy(reallyDesFolder); 

}

I do not understand why it cannot find hasnext function because in the gs documentation it is similar like this:

 var folders = DriveApp.getFolders();
 while (folders.hasNext()) {
   var folder = folders.next();
   Logger.log(folder.getName());
 }