Bug: onTransitionStart

[m1gu3l]

React version: any

Steps To Reproduce

Add onTransitionStart and onTransitionEnd handlers to element with styles that contain transition declaration

Link to code:

react/packages/react-dom-bindings/src/events/DOMEventProperties.js

Line 119 in 0b4f443

export function registerSimpleEvents() {

Link to docs:
https://developer.mozilla.org/en-US/docs/Web/API/Element/transitionstart_event

The current behavior

onTransitionEnd fires, onTransitionStart doesn't

The expected behavior

Both handlers should fire

[eps1lon]

It doesn't look like this bug report has enough info for one of us to reproduce it.

Please provide a CodeSandbox (https://react.new), or a link to a repository on GitHub.

Here are some tips for providing a minimal example: https://stackoverflow.com/help/mcve

[m1gu3l]

https://codesandbox.io/s/stoic-tu-kle13g?file=/src/App.js

[eps1lon]

When we do this, we should also add cancel and run for consistency. Seems like these weren't added because they didn't exist when that particular code was written.

Not sure how much work is required to get this into the current synthetic event system. But then there are also plans to drop the synthetic event system at which point onTransitionStart will just start working automatically.

[gaearon]

Should be easy to add to the list, I think.

[pauldraper]

This has been supported by every major browser since March 2020. https://caniuse.com/mdn-api_element_transitionstart_event

(Is this React thing still active?)