addEventListener method

EventTarget addEventListener(
  1. String type,
  2. dynamic listener(
    1. dynamic
    )
)

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;
}