puppeteer/website/versioned_docs/version-21.7.0/api/puppeteer.eventemitter.on.md
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---
sidebar_label: EventEmitter.on
---
# EventEmitter.on() method
Bind an event listener to fire when an event occurs.
#### Signature:
```typescript
class EventEmitter {
on<Key extends keyof EventsWithWildcard<Events>>(
type: Key,
handler: Handler<EventsWithWildcard<Events>[Key]>
): this;
}
```
## Parameters
| Parameter | Type | Description |
| --------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ |
| type | Key | the event type you'd like to listen to. Can be a string or symbol. |
| handler | [Handler](./puppeteer.handler.md)&lt;[EventsWithWildcard](./puppeteer.eventswithwildcard.md)&lt;Events&gt;\[Key\]&gt; | the function to be called when the event occurs. |
**Returns:**
this
`this` to enable you to chain method calls.