[Home](./index.md) > [puppeteer](./puppeteer.md) > [EventEmitter](./puppeteer.eventemitter.md) > [once](./puppeteer.eventemitter.once.md) ## EventEmitter.once() method Like `on` but the listener will only be fired once and then it will be removed. Signature: ```typescript once(event: EventType, handler: Handler): EventEmitter; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | event | [EventType](./puppeteer.eventtype.md) | the event you'd like to listen to | | handler | [Handler](./puppeteer.handler.md) | the handler function to run when the event occurs | Returns: [EventEmitter](./puppeteer.eventemitter.md) `this` to enable you to chain method calls.