code: function CancelableEvent (type, eventInit) {
          if ( eventInit === void 0 ) eventInit = {};
  
          Object.assign(this, CancelableEvent.defaults(), eventInit, { type: type });
  
          Object.defineProperties(this, {
              type: _makeCancelableEventProps(),
              cancelable: _makeCancelableEventProps(),
              nativeEvent: _makeCancelableEventProps(),
              target: _makeCancelableEventProps(),
              relatedTarget: _makeCancelableEventProps(),
              vueTarget: _makeCancelableEventProps()
          });
  
          var defaultPrevented = false;
  
          this.preventDefault = function preventDefault() {
              if (this.cancelable) {
                  defaultPrevented = true;
              }
          };
  
          Object.defineProperty(this, 'defaultPrevented', {
              enumerable: true,
              get: function get() {
                  return defaultPrevented
              }
          });
      }
docs: Custom cancelable event.