class ObservableObjecttype

type ObservableObject​.AttachListener

Type definition for a callback, or set of callbacks that can be passed to the ObservableObject.attach method.

type AttachListener<T extends ObservableObject> =
  | ((event: ObservableEvent) => Promise<void> | void)
  | {
      handler?: (object: T, event: ObservableEvent) => Promise<void> | void;
      detached?: (object: T) => void;
    }
  | {
      delegate?: ObservableObject.EventDelegate;
      detached?: (object: T) => void;
    };

Notes

• If a single function is provided, it will be called for all events emitted by the object.
• If an object with handler property is provided, that function will be called for all events, and the detached function will be called when the object is detached or unlinked.
• If the object includes a delegate property instead of handler, the delegate runs after all listen() handlers, allowing listeners to call stopPropagation(). If the event is not stopped and the delegate method returns falsy, the event bubbles up to the parent.

Related

• class ObservableObject
  The base class of all observable objects, which can be placed into a tree structure to enable event handling and data binding.