Cannot convert class to object in spreadsheet - arrays

Question

I wish to get a couple of properties of all the folders in my GDrive and write these properties to a spreadsheet. Because of the large number of folders (over 300) I have decided to use Paging and Batch processing. This seems to be working but I can't seem to write the Array[][] I've created in the batch processing to the spreadsheet.
I'm am getting the following error when I try to set the values in my spreadsheet:
Cannot convert (class)#3cc8188e to Object[][].
I did not find any listed questions that were similar to my problem.
The last line of the script is highlighted when the error appears. Code is:
function myFunction() {
var folder = DocsList.getFolder('MyFolder');
var subfolders = null;
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
var cell = sheet.getRange('a1');
var x = 0;
var pageSize = 250;
var token = null;
var xfolders = new Array(500);
do {
var resultset = folder.getFoldersForPaging(pageSize, token);
subfolders = resultset.getFolders();
token = resultset.getToken();
x = subfolders.length;
for (var a = 0; a < subfolders.length; a++) {
var contents = subfolders[a].getFiles();
xfolders[a] = new Array(6);
if(contents.length>0) {
xfolders[a][0] = subfolders[a].getName();
xfolders[a][1] = subfolders[a].getDateCreated();
xfolders[a][2] = subfolders[a].getLastUpdated();
xfolders[a][3] = contents.length;
xfolders[a][4] = subfolders[a].getSize();
xfolders[a][5] = a;
}
}
} while (subfolders.length > pageSize)
sheet.getRange(1, 1, x, 6).setValues(xfolders);
}

Answer 1

You've started with an array xfolders for which you've initialized a length. There's no need to do this - it's enough to know that it's an array. Later you call getRange() with rows==x, where x = subfolders.length... and if that isn't 500 (the length of xfolders) you will end up with your error. (...because you have undefined array elements.)
What you need to do is make sure that the range you're writing to has the same dimensions as the values you're presenting. One way to do that is to calculate the range dimensions using xfolders itself.
Here's your function, refactored to grow xfolders dynamically, and then to use its dimensions for output to the spreadsheet.
function myFunction() {
var folder = DocsList.getFolder('MyFolder');
var subfolders = null;
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
var cell = sheet.getRange('a1');
var pageSize = 250;
var token = null;
var xfolders = [];
do {
var resultset = folder.getFoldersForPaging(pageSize, token);
subfolders = resultset.getFolders();
token = resultset.getToken();
for (var a in subfolders) {
var contents = subfolders[a].getFiles();
xfolders[a] = [];
if(contents.length>0) {
xfolders[a][0] = subfolders[a].getName();
xfolders[a][1] = subfolders[a].getDateCreated();
xfolders[a][2] = subfolders[a].getLastUpdated();
xfolders[a][3] = contents.length;
xfolders[a][4] = subfolders[a].getSize();
xfolders[a][5] = a;
}
}
} while (subfolders.length == pageSize) // Quit when we aren't getting enough folders
sheet.getRange(1, 1, xfolders.length, xfolders[0].length).setValues(xfolders);
}