code: function (payload, callback) {
                  var i13nNode = payload.i13nNode;
                  if (i13nNode) {
                      var model = i13nNode.getMergedModel();
                      var hitType = 'event';
                      var params = {
                          hitType: hitType,
                          eventCategory: model.category || DEFAULT_CATEGORY,
                          eventAction: model.action || DEFAULT_ACTION,
                          eventLabel: model.label || i13nNode.getText(payload.target) || DEFAULT_LABEL,
                          eventValue: model.value || DEFAULT_VALUE,
                          transport: model.transport || DEFAULT_TRANSPORT,
                          nonInteraction: model.nonInteraction || DEFAULT_NON_INTERACTION,
                          hitCallback: callback
                      };
                      _command.call(this, {
                          tracker: model.tracker || '',
                          commandName: 'send',
                          arguments: [
                              hitType,
                              params
                          ]
                      });
                  } else {
                      callback && callback();
                  }
              }
docs: click handler
  @method pageview
  @param {Object} payload payload object
  @param {Object} payload.category category
  @param {Object} payload.action action
  @param {Object} payload.label label
  @param {Function} calback callback function