addEventListener method
Add an event listener @return The self object, for chainability.
Implementation
EventTarget addEventListener(String type, Function(dynamic) listener) {
_listeners ??= {};
final listeners = _listeners;
if (listeners?[type] == null) {
listeners![type] = [];
}
if (!listeners![type]!.contains(listener)) {
listeners[type]!.add(listener);
}
return this;
}