hytopia/docs/server.eventrouter.once.md

The HYTOPIA SDK makes it easy for developers to create massively multiplayer games using JavaScript or TypeScript.

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[Home](./index.md) &gt; [server](./server.md) &gt; [EventRouter](./server.eventrouter.md) &gt; [once](./server.eventrouter.once.md)

## EventRouter.once() method

Register a listener for a specific event type that will be invoked once.

**Signature:**

```typescript
once<TEventType extends keyof EventPayloads>(eventType: TEventType, listener: (payload: EventPayloads[TEventType]) => void): void;
```

## Parameters

<table><thead><tr><th>

Parameter


</th><th>

Type


</th><th>

Description


</th></tr></thead>
<tbody><tr><td>

eventType


</td><td>

TEventType


</td><td>

The type of event to listen for.


</td></tr>
<tr><td>

listener


</td><td>

(payload: [EventPayloads](./server.eventpayloads.md)<!-- -->\[TEventType\]) =&gt; void


</td><td>

The listener function to invoke when the event is emitted.


</td></tr>
</tbody></table>
**Returns:**

void