Current vnode `dom` property is undefined in `onbeforeupdate`

[Martin Boulais]

Mithril.js version: 2.2.2

Browser and OS: Firefox 118.0.2 (64-bit) on Ubuntu 22.04.3 LTS

Code

flems demo

Steps to Reproduce

1. Click on the button to increment the counter

Expected Behavior

I expect the value of vnode.dom to be the actual dom in onbeforeupdate, as it is in onupdate. If this is not the expected behavior, maybe it should be explicited in the documentation.

Current Behavior

Currently vnode.dom is undefined in onbeforeupdate

[Oscar]

Hello :) I think vnode.dom will always be undefined in onbeforeupdate. The reason why it shows the dom after a while, is that you're using a reference to the vnode, which by then has updated. If you deconstruct (or copy) the vnode, it'll stay undefined: flems.

[kfule]

You can access current dom via old.dom of onbeforeupdate(vnode, old).
flems

[Martin Boulais]

Hello,
Thank you for your quick reply. I used a reference on purpose, to be sure that the node that is provided is the one that will be used after the update, which makes sense.
The fact that it is named old mislead me. If I am not wrong, old actually contain the current vnode, and the first argument is passed the future vnode, which indeed do not have a dom element yet.
Closing the issue, thanks!

[Claudia Meadows]

@martinboulais If it helps, the current, most recently received vnode, hasn't been rendered yet, only the previous, old one. The hook exists to know whether to render the current vnode.