Map (and some other classes) emit events in response to user interactions or changes in state.
Evented is the interface used to bind and unbind listeners for these events.
The function to be called when the event is fired. The listener function is called
with the data object passed to fire, extended with the target and type properties.
Adds a listener that will be called only once to a specified event type.
The listener will be called the first time the event fires after the listener is registered.