code: function (key) {
              var newLocaleData;
  
              if (key === undefined) {
                  return this._locale._abbr;
              } else {
                  newLocaleData = moment.localeData(key);
                  if (newLocaleData != null) {
                      this._locale = newLocaleData;
                  }
                  return this;
              }
          }
docs: If passed a locale key, it will set the locale for this instance.  Otherwise, it will return the locale configuration variables for this instance.