addListener method
Implementation
@VoltronMethod(kModuleAddListener)
void addListener(String name, JSPromise promise) {
var count = 0;
if (_eventMap.containsKey(name)) {
count = _eventMap[name]!;
}
count++;
if (count == 1) {
handleAddListener(name);
}
_eventMap.remove(name);
_eventMap[name] = count;
}