[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)