code: function (params) {
          var countries = _data;
          var subset = [], i = 0;
          if (params.whitelist) {
              var whitelist = params.whitelist.split(",");
              for (i = 0; i < _data.length; i++) {
                  if (whitelist.indexOf(_data[i][1]) !== -1) {
                      subset.push(_data[i]);
                  }
              }
              countries = subset;
          } else if (params.blacklist) {
              var blacklist = params.blacklist.split(",");
              for (i = 0; i < _data.length; i++) {
                  if (blacklist.indexOf(_data[i][1]) === -1) {
                      subset.push(_data[i]);
                  }
              }
              countries = subset;
          }
  
          if (params.preferred) {
              countries = _applyPreferredCountries(countries, params.preferred, params.preferredDelim);
          }
  
          _countries = countries;
  
          // now init the regions
          _initRegions();
      }
docs: called on country field initialization. It reduces the subset of countries depending on whether the user specified a white/blacklist and parses the region list to extract the