Recursive File List from Google Drive

function onOpen() {
    var ss = SpreadsheetApp.getActiveSpreadsheet();
    var searchMenuEntries = [{
        name: "Create a File List from Folder",
        functionName: "start"
    }];
    ss.addMenu("File List", searchMenuEntries);
}


function start() {
    var sheet = SpreadsheetApp.getActiveSheet();
    sheet.clear();
  //Comment below enable it if you need one sheet
    sheet.appendRow(["Name", "Folder", "Type", "Date", "Size", "URL" ]);

    var folderName = Browser.inputBox("Enter Folder Name (this will destroy the current spreadsheet):");
    //var folderName = "Safety Subdomain Assets";

    var folder = DriveApp.getFoldersByName(folderName);

    if (folder.hasNext()) {
        processFolder(folder);
    } else {
        Browser.msgBox('Folder not found!');
    }


    function processFolder(folder) {
        while (folder.hasNext()) {
            var f = folder.next();
            var contents = f.getFiles();
            addFilesToSheet(contents, f);
            var subFolder = f.getFolders();
            processFolder(subFolder);
        }
    }

    function addFilesToSheet(files, folder) {      
        var data;
        var folderName = folder.getName();
      //Delete this two lines below if you need one Sheet
//      sheet.appendRow(["Folder: " + folder]);
//      sheet.appendRow(["Name", "Folder", "Type", "Date", "Size", "URL" ]);
        while (files.hasNext()) {
            var file = files.next();
            Logger.log(file.getName());

            sheet.appendRow([
      file.getName(),
      folderName,
      file.getMimeType(),
      file.getDateCreated(),
      file.getSize()/1024,
      file.getUrl()  

    ]);
        }
    }

}