code: function processItem(path) {
              var deferred = new $.Deferred(),
                  fileEntry = FileSystem.getDirectoryForPath(path);
  
              fileEntry.exists(function (err, exists) {
                  if (!err && exists) {
                      deferred.resolve();
                  } else {
                      deferred.reject();
                  }
              });
  
              return deferred.promise();
          }
docs: Helper func for Async.firstSequentially()