Listenable Interface
Packages > @fluidframework/tree > Listenable
An object which allows the registration of listeners so that subscribers can be notified when an event happens.
Signature
/** @sealed */
export interface Listenable<TListeners extends object>
Type Parameters
| Parameter | Constraint | Description |
|---|---|---|
| TListeners | object |
Methods
| Method | Return Type | Description |
|---|---|---|
| on(eventName, listener) | Off | Register an event listener. |
Method Details
on
Register an event listener.
Signature
on<K extends keyof Listeners<TListeners>>(eventName: K, listener: TListeners[K]): Off;
Type Parameters
| Parameter | Constraint | Description |
|---|---|---|
| K | keyof Listeners<TListeners> |
Remarks
Do not register the exact same listener object for the same event more than once. Doing so will result in undefined behavior, and is not guaranteed to behave the same in future versions of this library.
Parameters
| Parameter | Type | Description |
|---|---|---|
| eventName | K | The name of the event. |
| listener | TListeners[K] | the handler to run when the event is fired by the emitter |
Returns
a function which will deregister the listener when called. This deregistration function is idempotent and therefore may be safely called more than once with no effect.
Return type: Off