[Home](./index.md) > [puppeteer](./puppeteer.md) > [CommonEventEmitter](./puppeteer.commoneventemitter.md) > [once](./puppeteer.commoneventemitter.once.md)
## CommonEventEmitter.once() method
Signature:
```typescript
once(event: EventType, handler: Handler): CommonEventEmitter;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| event | [EventType](./puppeteer.eventtype.md) | |
| handler | [Handler](./puppeteer.handler.md) | |
Returns:
[CommonEventEmitter](./puppeteer.commoneventemitter.md)