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Dan Abramov 4 years ago
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      content/blog/2020-08-10-react-v17-rc.md

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content/blog/2020-08-10-react-v17-rc.md
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@ -81,6 +81,10 @@ This change also **makes it easier to embed React into apps built with other tec
We've confirmed that [numerous](https://github.com/facebook/react/issues/7094) [problems](https://github.com/facebook/react/issues/8693) [reported](https://github.com/facebook/react/issues/12518) [over](https://github.com/facebook/react/issues/13451) [the](https://github.com/facebook/react/issues/4335) [years](https://github.com/facebook/react/issues/1691) [on](https://github.com/facebook/react/issues/285#issuecomment-253502585) [our](https://github.com/facebook/react/pull/8117) [issue](https://github.com/facebook/react/issues/11530) [tracker](https://github.com/facebook/react/issues/7128) related to integrating React with non-React code have been fixed by the new behavior.
>Note
>
>You might be wondering whether this breaks [Portals](/docs/portals.html) outside of the root container. The answer is that React *also* listens to events on portal containers, so this is not an issue.
#### Fixing Potential Issues
As with any breaking change, it is likely some code would need to be adjusted. At Facebook, we had to adjust about 10 modules in total (out of many thousands) to work with this change.
@ -160,6 +164,10 @@ However, the effect *cleanup* function, when it exists, used to run synchronousl
This mirrors how the effects themselves run more closely. In the rare cases where you might want to rely on the synchronous execution, you can switch to `useLayoutEffect` instead.
>Note
>
>You might be wondering whether this means that you'll now be unable to fix warnings about `setState` on unmounted components. Don't worry -- React specifically checks for this case, and does *not* fire `setState` warnings in the short gap between unmounting and the cleanup. **So code cancelling requests or intervals can almost always stay the same.**
Additionally, React 17 executes the cleanup functions in the same order as the effects, according to their position in the tree. Previously, this order was occasionally different.
#### Potential Issues

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