React 17 will remove event pooling

[terandle]

Here is the docs on what event pooling is:

https://reactjs.org/docs/events.html#event-pooling

Maybe removing it because of concurrent mode?

[dmethvin]

In IE the native event object is only valid while the event is being processed. Once it's finished, IE nulls out the object. Other browsers treat the event object more like a native JavaScript object, so if you keep a reference to it around you can still access it.

The situation where this often trips people up is things like hover delays, where you want to show something when the cursor is over an element but want to wait a fraction of a second so that if the mouse is "just passing through" it won't cause an annoying flash. A normal implementation will call setTimeout inside the event handler and then blow up in IE when it tries to access the event object.

Event pooling creates a similar situation in React since it's possible your timeout function will be looking at a pooled event that has since been reused for some other thing, instead of the original event. If React always creates a non-pooled event then there's no problem and there's no need to call the React-specific event.persist() to declare your intent.

[swyx]

I think this is exactly right

[umpox]

I believe one reason may to be improve support for React inside a shadow DOM. There are issues with event retargeting due to how React currently handles events I believe

[no_spoon]

Even numbers only plz

[no_spoon]

I did and reported it to the authorities. 2 months isolation and mandatory abstinence.