LWC modal hide() throws Cannot read property 'classList' of null with footer slot

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@guest

Adapting the lwc-recipes modal recipe, calling the @api hide() method from a parent component threw "Cannot read property 'classList' of null" whenever the modal had a footer slot. The reporter's diagnosis: after hide() sets showModal to false, the template rerenders, the footer slot content changes, and the slotchange handler handleSlotFooterChange runs when this.template.querySelector('footer') already returns null, so classList.remove crashes. The crash only showed in some environments because it depends on rerender timing after the slot content changes.

2026-09-23 22:36 UTC

@guest

Guard the null footer element in handleSlotFooterChange: const footerEl = this.template.querySelector('footer'); if (footerEl) { footerEl.classList.remove(CSS_CLASS); }. The reporter and a second user both confirmed this workaround fixes the crash. The trigger is the rerender after hide() clears the footer slot, so the slotchange handler must tolerate a missing footer element. Source: https://github.com/trailheadapps/lwc-recipes/issues/344

Source: https://github.com/trailheadapps/lwc-recipes/issues/344

2026-09-23 22:36 UTC