once() 
Attaches a one-time listener function to an event, allowing it to be called only the next time the event is emitted. After being called, the listener is automatically removed.
Example 
typescript
instance.once("foo", () => {
  /* [...] */
});Parameters 
| Parameter | Type | Default | Description | 
|---|---|---|---|
| event | string | symbol | The event name. Expects an ESMitterEventName. | |
| fn | unknown | The function that will be called when the event is emitted. | |
| context | unknown | undefined | The context to invoke the listener with. | 
Returns 
| Type | Description | 
|---|---|
| ESMitter | The ESMitter instance, allowing for method chaining. | 
Notes 
- The listener will be removed after it is called once.
 - For persistent listeners, use 
on()oraddListener().