code: function TabsEvent(type, index) {
        classCallCheck(this, TabsEvent);
  
        this.type = type;
  
        /** @type {number} */
        this.index = index;
  
        /** @type {boolean} Whether `preventDefault` has been called. */
        this.defaultPrevented = false;
      }
docs: Object representing a tab event.
  @param {string} type Event type.
  @param {number} index Index of tab.
  @constructor