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Scheduler: Cannot read properties of null (reading 'calendar')

Asked by Leo
3 days ago.

Hi Dan,

On the live demo on https://javascript.daypilot.org/demo/scheduler/index.html, using a touch device (Android, Chrome) and some wild scrolling, I receive the following errors.

  • Number one happens when you scroll with momentum and then tap on the screen to stop scrolling. I don’t believe it has a real-world impact.

  • Error two happened directly afterwards - we see this pop up on Sentry quite a lot as well, however I can’t confidently reproduce it.

I have added the code sections - these are from the minified code but might help nonetheless.

bug javascript
Answer posted by Dan Letecky [DayPilot]
2 days ago.

Hi Leo,

The error #2 should be fixed now. There was an issue with events located next to a disabled parent row (treePreventParentUsage: true) when you tried to move them into the disabled row and started dragging very close to the event border.

The error #1 should never happen as the event handler is marked as non-passive. However, another safeguard was added which should prevent it.

If any of these errors still happen with the latest sandbox build (2025.3.6532), please let me know.

Comment posted by Leo
2 days ago.

Hi Dan,

Many thanks for all your fixes!

I can still reproduce #1 on the sandbox build by scrolling on a touch device with momentum, and then tapping & holding onto the grid (triggering an event creation).

- Leo

Comment posted by Dan Letecky [DayPilot]
2 days ago.

Thanks for the reproduction steps. Could you please give it a try with build 2025.3.6535?

Comment posted by Leo
2 days ago.

Perfect - it’s fixed and I can no longer reproduce it :)

Comment posted by Dan Letecky [DayPilot]
2 days ago.

Great, thanks for the update!

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