illustrator recursive getfiles

function getFiles(folder, search) {
  var items = folder.getFiles();
  var files = [];
  for (var i=0; i < items.length; i++) {
    var item = items[i];
    if (item instanceof Folder && item.name != '.' && item.name != '..') {
      files.concat(getFiles(folder));
    } else if (item instanceof File && item.name.toLowerCase().indexOf(search) > -1) {
      files.push(item);
    }
  }
  return files;
}

var folder =  new Folder('category');
var files = getFiles(folder, '.jpg');
for (var i=0; i<files.length; i++) {
  var file = files[i];
  // file
}