> For the complete documentation index, see [llms.txt](https://bryan-guner.gitbook.io/my-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bryan-guner.gitbook.io/my-docs/mynotes/react-docs/event-pooling.md).

# Event Pooling

> Note
>
> This page is only relevant for React 16 and earlier, and for React Native.
>
> React 17 on the web **does not** use event pooling.
>
> Read more about this change in React 17.

The `SyntheticEvent` objects are pooled. This means that the `SyntheticEvent` object will be reused and all properties will be nullified after the event handler has been called. For example, this won't work:

```javascript
function handleChange(e) {
  // This won't work because the event object gets reused.
  setTimeout(() => {
    console.log(e.target.value); // Too late!
  }, 100);
}
```

If you need to access event object's properties after the event handler has run, you need to call `e.persist()`:

```javascript
function handleChange(e) {
  // Prevents React from resetting its properties:
  e.persist();

  setTimeout(() => {
    console.log(e.target.value); // Works
  }, 100);
}
```