code: function addListenerToEventMap(element, type, listener, useCapture, data) {
          var eventNameLowercase = type.toLowerCase();
          if (!element._eventsMap) {
              element._eventsMap = {};
          }
          if (!element._eventsMap[eventNameLowercase]) {
              element._eventsMap[eventNameLowercase] = [];
          }
          element._eventsMap[eventNameLowercase].push({
              listener: listener,
              useCapture: useCapture,
              data: data
          });
      }
docs: Helpers for managing element._eventsMap for custom events