TypeError: Cannot find function hasNext in object

问题

I'm trying to save an email in to a particular drive folder however getting error message

TypeError: Cannot find function hasNext in object

Any idea how I can overcome this.

function saveGmailToDrive() { 
    var gmailLabels  = "SaveToDrivetest";  
    var driveFolder  = "Emails saved by " + Session.getActiveUser().getEmail()

    /* Gmail Label that contains the queue */
    var label = GmailApp.getUserLabelByName(gmailLabels) ? 
                    GmailApp.getUserLabelByName(gmailLabels) :
                    GmailApp.createLabel(gmailLabels);

    var threads = GmailApp.search("in:" + gmailLabels, 0, 5);  

    if (threads.length > 0) {    
        /* Google Drive folder where the Files would be saved */
        var folders = DriveApp.getFolderById("0B9Ug3fXvrl5HeGRddddMcE93bkE3Q1k");
        var folder = folders.hasNext() ?
                         folders.next() : 
                         DriveApp.createFolder(driveFolder);
    }

回答1:

In general: if the noun after "get" is in plural form, you get an iterator to be used with hasNext and next methods. If that noun is in singular form, you get a single object. Examples:

• getFileById returns one File
• getFiles returns an iterator
• getFilesByName returns an iterator
• getFilesByType returns an iterator
• getFolderById returns one Folder
• getFolders returns an iterator
• getFoldersByName returns an iterator

来源：https://stackoverflow.com/questions/46834799/typeerror-cannot-find-function-hasnext-in-object