From efccb59f2bd93cfdaf6e7a52e73c406efdda7fe0 Mon Sep 17 00:00:00 2001
From: Dimitris - Rafail Katsampas <katsampasdr@gmail.com>
Date: Wed, 16 Jun 2021 14:27:51 +0300
Subject: [PATCH] fix: `popstate` listener was not removed on Router unmount

---
 Router.svelte | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/Router.svelte b/Router.svelte
index aa6be6d..d13af44 100644
--- a/Router.svelte
+++ b/Router.svelte
@@ -454,18 +454,20 @@ let previousScrollState = null
 // Update history.scrollRestoration depending on restoreScrollState
 $: history.scrollRestoration = restoreScrollState ? 'manual' : 'auto'
 
+const popStateChanged = (event) => {
+    // If this event was from our history.replaceState, event.state will contain
+    // our scroll history. Otherwise, event.state will be null (like on forward
+    // navigation)
+    if (event.state && event.state.__svelte_spa_router_scrollY) {
+        previousScrollState = event.state
+    }
+    else {
+        previousScrollState = null
+    }
+}
+
 if (restoreScrollState) {
-    window.addEventListener('popstate', (event) => {
-        // If this event was from our history.replaceState, event.state will contain
-        // our scroll history. Otherwise, event.state will be null (like on forward
-        // navigation)
-        if (event.state && event.state.__svelte_spa_router_scrollY) {
-            previousScrollState = event.state
-        }
-        else {
-            previousScrollState = null
-        }
-    })
+    window.addEventListener('popstate', popStateChanged)
 
     afterUpdate(() => {
         // If this exists, then this is a back navigation: restore the scroll position
@@ -588,5 +590,6 @@ const unsubscribeLoc = loc.subscribe(async (newLoc) => {
 
 onDestroy(() => {
     unsubscribeLoc()
+    window.removeEventListener('popstate', popStateChanged)
 })
 </script>