BUG with style={{display:undefined}}

[devnixs]

display:undefined should not apply any style to the element, and yet it does.

Minimal example here:

https://preactjs.com/repl?code=export%20default%20class%20TodoList%20extends%20Component%20%7B%0A%20%20%20%20state%20%3D%20%7B%20visible%20%3A%20true%20%7D%3B%0A%0A%20%20%20%20render(%7B%20%7D%2C%20%7B%20todos%2C%20text%20%7D)%20%7B%0A%20%20%20%20%20%20%20%20return%20(%0A%20%20%20%20%20%20%20%20%20%20%20%20%3Cdiv%3E%0A%09%09%09%09The%20following%20texte%20should%20be%20%7Bthis.state.visible%20%3F%20%27Visible%27%3A%27Hidden%27%7D%0A%09%09%09%09%3Cbr%2F%3E%0A%09%09%09%09%3Cspan%20style%3D%7B%7Bdisplay%3Athis.state.visible%20%3F%20undefined%20%3A%20%27none%27%7D%7D%3EHello%20There!%3C%2Fspan%3E%0A%09%09%09%09%3Cbr%2F%3E%0A%09%09%09%09%3Ca%20href%3D%22%23%22%20onClick%3D%7B(event)%3D%3Ethis.setState(%7Bvisible%3A!this.state.visible%7D)%7D%3EToggle%3C%2Fa%3E%20(click%20me%20multiple%20times)%0A%09%09%09%09%3C%2Fdiv%3E%0A%20%20%20%20%20%20%20%20)%3B%0A%20%20%20%20%7D%0A%7D%0A

[mikewesthad]

Is this a bug because the same thing presumably works in React? Using this { display: this.state.visible ? '' : 'none' } would work in preact.

If it's something that needs to be fixed, I imagine updating this line to add a check if the style prop is undefined (and convert its value to an empty string) would do the trick.

[developit]

Strange bug. It seems like node.style.display = undefined doesn't unset values? Interesting that using null works fine:

https://jsfiddle.net/9gnokkLj/1/

[developit]

Confirmed, this is just a weird detail of how the style property works:
https://jsfiddle.net/szawjdhs/5/

[devnixs]

Yep! But it should be fixed because the view should be a pure function of the state and props.
It's not the case here because it depends on what happened before.
Also, it works with React.

[developit]

Agreed, definitely on the to-do list.

[marvinhagemeister]

Good news: This issue is fixed in Preact X. I can't reproduce it anymore 🎉