Subscription

Subscription object is returned by Chart Methods. Using this object you can subscribe to a chart event and unsubscribe from it. So it has two methods:

subscribe(object, method, singleshot)

1. object is a context to be used as this pointer for method function. Use null if you don't need the context.
2. method is a function to be called when the event happens
3. singleshot is an optional argument. Set it to true to be automatically unsubscribed when the event happens first time.

unsubscribe(object, method)

Use the same object and method which you used in subscribe function to unsubscribe from the event.