⚡ Bolt: cache favorites to prevent synchronous localStorage reads

.jules/bolt.md

@@ -0,0 +1,4 @@
+
+## 2026-03-04 - [Caching localStorage for High-Frequency Loops]
+**Learning:** Found a performance bottleneck where `localStorage.getItem` and `JSON.parse()` were being called synchronously inside `getFavorites()`, which was executed on every keystroke during `renderPDFs` search filtering.
+**Action:** Always cache expensive synchronous operations (like `localStorage` parsing) in a variable when they are accessed in high-frequency rendering or filtering loops. Ensure state updating functions like `toggleFavorite` update both the cache and persistent storage.

script.js

@@ -1315,9 +1315,14 @@ async function handleCommentSubmit(e) {
 /* =========================================
    10. EXTRAS (THEME, FAVORITES, EASTER EGGS)
    ========================================= */
+// ⚡ Bolt Optimization: Cache favorites to avoid synchronous localStorage reads and JSON.parse on every render
+let favoritesCache = null;
+
 function getFavorites() {
+    if (favoritesCache !== null) return favoritesCache;
     const stored = localStorage.getItem('classNotesFavorites');
-    return stored ? JSON.parse(stored) : [];
+    favoritesCache = stored ? JSON.parse(stored) : [];
+    return favoritesCache;
 }
 
 function toggleFavorite(event, pdfId) {
@@ -1336,6 +1341,9 @@ function toggleFavorite(event, pdfId) {
         favorites.push(pdfId);
         showToast('Added to saved notes');
     }
+
+    // Update cache before saving
+    favoritesCache = favorites;
     localStorage.setItem('classNotesFavorites', JSON.stringify(favorites));
     renderPDFs();
 }