addEventListener method

void addEventListener(
  1. String type,
  2. Function listener
)

Implementation

void addEventListener(String type, Function listener) {
  _listeners ??= {};

  Map<String, List<Function>> listeners = _listeners!;

  if (listeners[type] == null) {
    listeners[type] = [];
  }

  if (!listeners[type]!.contains(listener)) {
    listeners[type]!.add(listener);
  }
}