Your listener id (must be unique for all layer events)
Your listener function
// Each time a layer thematic condition visibility state is changed this method is processed
JMap.Event.Layer.on.thematicConditionsVisibilityChange(
   "custom-thematic-conditions-visibility-change",
   params => {
     console.log(
       `Layer id="${params.layerId}", ` +
       `thematic id="${params.thematicId}" ` +
       `hidden conditions="${params.hiddenConditionIds.toString()}"`
     )
   }
)
JMap.Event.Layer.on.thematicConditionsVisibilityChange
This event is triggered when the visibility state of a layer thematic condition changes.
It works only for JMap Server server, for style rule thematics.