detachEvent of common helpers, Methods Webix Docs

detaches a handler from an event (which was attached before by the attachEvent method)

void detachEvent(string id);

stringthe event id (the result of the attachEvent operation)

var myEvent = $$("mylist").attachEvent("onItemClick", function (){
    ...//event handler code
});
...
$$("mylist").detachEvent(myEvent);