code: function(category, action, options) {
        if(!category || !action) {
          warn('event: both `category` and `action` are required.');
          return;
        }
  
        if(options && typeof options.eventValue !== 'undefined' && typeof options.eventValue !== 'number') {
          warn('event: expected `options.eventValue` to be a Number.');
          options.eventValue = undefined;
        }
  
        if(options && options.nonInteraction && typeof options.nonInteraction !== 'boolean') {
          warn('event: expected `options.nonInteraction` to be a boolean.');
          options.nonInteraction = false;
        }
  
        _set.call(this, 'send', 'event', category, action, options);
  
        return this;
      }
docs: https://developers.google.com/analytics/devguides/collection/analyticsjs/events