code: function setupCustomFileProperties(files, groupID) {
          for (var i = 0; i < files.length; i++) {
              var file = files[i];
              file.extra = {
                  nameNoExtension: file.name.substring(0, file.name.lastIndexOf('.')),
                  extension: file.name.substring(file.name.lastIndexOf('.') + 1),
                  fileID: i,
                  uniqueID: getUniqueID(),
                  groupID: groupID,
                  prettySize: prettySize(file.size)
              };
          }
      }
docs: setupCustomFileProperties: modify the file object with extra properties