code: function (successCB, failureCB, args, env) {
          var result = new PluginResult(args, env);
          var response = g11n.getInstance().InvokeMethod('getPreferredLanguage', args);
          var data = JSON.parse(response);
          console.log('getPreferredLanguage: ' + JSON.stringify(response));
  
          if (data.error !== undefined) {
              result.error({
                  code: data.error.code,
                  message: data.error.message
              });
          } else {
              result.ok({
                  value: data.result
              });
          }
      }
docs: Returns the string identifier for the client's current language.
  It returns the language identifier string to the successCB callback with a
  properties object as a parameter. If there is an error getting the language,
  then the errorCB callback is invoked.
  
  @param {Function} successCB
  @param {Function} errorCB
  
  @return Object.value {String}: The language identifier
  
  @error GlobalizationError.UNKNOWN_ERROR
  
  Example
  globalization.getPreferredLanguage(function (language) {alert('language:' + language.value + '\n');},
  function () {});