Listenable Interface
An object which allows the registration of listeners so that subscribers can be notified when an event happens.
This type is "sealed," meaning that code outside of the library defining it should not implement or extend it. Future versions of this type may add members or make typing of readonly members more specific.
Signature
/** @sealed */
export interface Listenable<TListeners extends object>
Type Parameters
| Parameter | Constraint | Description |
|---|---|---|
| TListeners | object |
Methods
| Method | Return Type | Description |
|---|---|---|
| off(eventName, listener) | void | Deregister an event listener. |
| on(eventName, listener) | Off | Register an event listener. |
Method Details
off
Deregister an event listener.
Signature
off<K extends keyof Listeners<TListeners>>(eventName: K, listener: TListeners[K]): void;
Type Parameters
| Parameter | Constraint | Description |
|---|---|---|
| K | keyof Listeners<TListeners> |
Remarks
If listener is not currently registered, this method will have no effect.
Listeners may also be deregistered by calling the deregistration function returned when they are registered.
Parameters
| Parameter | Type | Description |
|---|---|---|
| eventName | K | The name of the event. |
| listener | TListeners[K] | The listener function to remove from the current set of event listeners. |
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
Registering the exact same listener object for the same event more than once will throw an error. If registering the same listener for the same event multiple times is desired, consider using a wrapper function for the second subscription.
Parameters
| Parameter | Type | Description |
|---|---|---|
| eventName | K | The name of the event. |
| listener | TListeners[K] | The listener function to run when the event is fired. |
Returns
A function which will deregister the listener when called. Calling the deregistration function more than once will have no effect.
Listeners may also be deregistered by passing the listener to off().
Return type: Off