code: function reFile(filename, nfilename) {
      return new Promise(function (fulfill, reject) {
          fs.rename(filename, nfilename, function (err) {
              return err ? reject(err) : fulfill();
          });
      });
  }
docs: Rename the filename to nfilename. If nfilename and filename are not in the same physical path, the move file action will be triggered.
  Asynchronous mode
  @param {string} filename
  @param {string} nfilename
  @returns {*}