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fix: double event processing in Firefox (#16522) #16527

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Merged
merged 2 commits into from
Jul 31, 2025
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fix: double event processing in Firefox (#16522) #16527

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6a1d0ea
Fix double event processing (#16522)
laszlokorte Jul 30, 2025
4edbbfc
minor tweaks
Ocean-OS Jul 31, 2025
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5 changes: 5 additions & 0 deletions .changeset/chilly-bananas-train.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'svelte': patch
---

fix: double event processing in firefox due to event object being garbage collected
9 changes: 9 additions & 0 deletions packages/svelte/src/internal/client/dom/elements/events.js
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Expand Up @@ -141,6 +141,13 @@ export function delegate(events) {
}
}

// used to store the reference to the currently propagated event
// to prevent garbage collection between microtasks in Firefox
// If the event object is GCed too early, the expando __root property
// set on the event object is lost, causing the event delegation
// to process the event twice
let last_propagated_event = null;

/**
* @this {EventTarget}
* @param {Event} event
Expand All @@ -153,6 +160,8 @@ export function handle_event_propagation(event) {
var path = event.composedPath?.() || [];
var current_target = /** @type {null | Element} */ (path[0] || event.target);

last_propagated_event = event;

// composedPath contains list of nodes the event has propagated through.
// We check __root to skip all nodes below it in case this is a
// parent of the __root node, which indicates that there's nested
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