MrAlokTech · MrAlokTech · Mar 10, 2026
diff --git a/.jules/bolt.md b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-18 - [Optimize render loop by pre-calculating expensive values]
+**Learning:** Repetitive Date parsing (e.g., `new Date()`) and string concatenations for search filtering inside high-frequency render loops (like `renderPDFs` and `createPDFCard`) significantly block the main thread and impact frontend performance. Firestore Timestamp objects add an extra layer of complexity as they must be parsed differently (`.toDate()`) than cached JSON string dates.
+**Action:** Implement a `prepareSearchIndex` step that runs immediately after data load to pre-calculate these expensive values (`_searchStr`, `_formattedDate`, `_isNew`) onto the `pdfDatabase` objects. This dramatically speeds up subsequent array filtering and DOM generation.
diff --git a/bolt_test.js b/bolt_test.js
@@ -0,0 +1,15 @@
+const fs = require('fs');
+let code = fs.readFileSync('script.js', 'utf8');
+
+// Mock DOM
+const jsdom = require("jsdom");
+const { JSDOM } = jsdom;
+const dom = new JSDOM(`<!DOCTYPE html><body><div id="pdfGrid"></div></body>`);
+global.document = dom.window.document;
+global.window = dom.window;
+global.localStorage = {
+    getItem: () => null,
+    setItem: () => {}
+};
+
+console.log('Setup ready');
diff --git a/perf_test.js b/perf_test.js
@@ -0,0 +1,34 @@
+const pdfs = [];
+for (let i = 0; i < 1000; i++) {
+    pdfs.push({ uploadDate: "2023-10-15T12:00:00Z" });
+}
+
+console.time('date_format');
+for(let i = 0; i < pdfs.length; i++) {
+    const uploadDateObj = new Date(pdfs[i].uploadDate);
+    const timeDiff = new Date() - uploadDateObj;
+    const isNew = timeDiff < (7 * 24 * 60 * 60 * 1000);
+    const formattedDate = new Date(pdfs[i].uploadDate).toLocaleDateString('en-US', {
+        year: 'numeric', month: 'short', day: 'numeric'
+    });
+}
+console.timeEnd('date_format');
+
+console.time('precalc');
+// Simulate pre-calculated property
+pdfs.forEach(p => {
+    const uploadDateObj = new Date(p.uploadDate);
+    const timeDiff = new Date() - uploadDateObj;
+    p._isNew = timeDiff < (7 * 24 * 60 * 60 * 1000);
+    p._formattedDate = new Date(p.uploadDate).toLocaleDateString('en-US', {
+        year: 'numeric', month: 'short', day: 'numeric'
+    });
+});
+console.timeEnd('precalc');
+
+console.time('precalc_read');
+for(let i = 0; i < pdfs.length; i++) {
+    const isNew = pdfs[i]._isNew;
+    const formattedDate = pdfs[i]._formattedDate;
+}
+console.timeEnd('precalc_read');
diff --git a/script.js b/script.js
@@ -335,6 +335,35 @@ function getAdData(slotName) {
 /* =========================================
    5. DATA LOADING WITH CACHING
    ========================================= */
+
+function prepareSearchIndex() {
+    const now = new Date();
+    const sevenDays = 7 * 24 * 60 * 60 * 1000;
+
+    pdfDatabase.forEach(pdf => {
+        // 1. Search String (lowercased concatenation for fast indexOf)
+        pdf._searchStr = `${pdf.title || ''} ${pdf.description || ''} ${pdf.category || ''} ${pdf.author || ''}`.toLowerCase();
+
+        // 2. Date parsing (Handle both Firestore Timestamp and Cached ISO String)
+        let uploadDateObj;
+        if (pdf.uploadDate && typeof pdf.uploadDate.toDate === 'function') {
+            uploadDateObj = pdf.uploadDate.toDate();
+            // Optional: convert back to ISO string if we need consistency
+            pdf.uploadDate = uploadDateObj.toISOString();
+        } else {
+            uploadDateObj = new Date(pdf.uploadDate);
+        }
+
+        // 3. Pre-calculate "New" badge status
+        const timeDiff = now - uploadDateObj;
+        pdf._isNew = timeDiff < sevenDays;
+
+        // 4. Pre-format date string
+        pdf._formattedDate = uploadDateObj.toLocaleDateString('en-US', {
+            year: 'numeric', month: 'short', day: 'numeric'
+        });
+    });
+}
 function renderSemesterTabs() {
     const container = document.getElementById('semesterTabsContainer');
     if (!container) return;
@@ -451,6 +480,7 @@ async function loadPDFDatabase() {
 
         if (shouldUseCache) {
             pdfDatabase = cachedData;
+            prepareSearchIndex();
             // --- FIX: CALL THIS TO POPULATE UI ---
             syncClassSwitcher();
             renderSemesterTabs();
@@ -469,6 +499,8 @@ async function loadPDFDatabase() {
             pdfDatabase.push({ id: doc.id, ...doc.data() });
         });
 
+        prepareSearchIndex();
+
         localStorage.setItem(CACHE_KEY, JSON.stringify({
             timestamp: new Date().getTime(),
             data: pdfDatabase
@@ -902,26 +934,22 @@ function renderPDFs() {
 
     // Locate renderPDFs() in script.js and update the filter section
     const filteredPdfs = pdfDatabase.filter(pdf => {
-        const matchesSemester = pdf.semester === currentSemester;
-
-        // NEW: Check if the PDF class matches the UI's current class selection
-        // Note: If old documents don't have this field, they will be hidden.
-        const matchesClass = pdf.class === currentClass;
+        // Fast early returns for exact matches
+        if (pdf.semester !== currentSemester) return false;
+        if (pdf.class !== currentClass) return false;
 
-        let matchesCategory = false;
         if (currentCategory === 'favorites') {
-            matchesCategory = favorites.includes(pdf.id);
-        } else {
-            matchesCategory = currentCategory === 'all' || pdf.category === currentCategory;
+            if (!favorites.includes(pdf.id)) return false;
+        } else if (currentCategory !== 'all') {
+            if (pdf.category !== currentCategory) return false;
         }
 
-        const matchesSearch = pdf.title.toLowerCase().includes(searchTerm) ||
-            pdf.description.toLowerCase().includes(searchTerm) ||
-            pdf.category.toLowerCase().includes(searchTerm) ||
-            pdf.author.toLowerCase().includes(searchTerm);
+        // Use pre-computed search string
+        if (searchTerm && (!pdf._searchStr || !pdf._searchStr.includes(searchTerm))) {
+            return false;
+        }
 
-        // Update return statement to include matchesClass
-        return matchesSemester && matchesClass && matchesCategory && matchesSearch;
+        return true;
     });
 
     updatePDFCount(filteredPdfs.length);
@@ -991,9 +1019,7 @@ function createPDFCard(pdf, favoritesList, index = 0, highlightRegex = null) {
     const heartIconClass = isFav ? 'fas' : 'far';
     const btnActiveClass = isFav ? 'active' : '';
 
-    const uploadDateObj = new Date(pdf.uploadDate);
-    const timeDiff = new Date() - uploadDateObj;
-    const isNew = timeDiff < (7 * 24 * 60 * 60 * 1000); // 7 days
+    const isNew = pdf._isNew;
 
     const newBadgeHTML = isNew
         ? `<span style="background:var(--error-color); color:white; font-size:0.6rem; padding:2px 6px; border-radius:4px; margin-left:8px; vertical-align:middle;">NEW</span>`
@@ -1008,9 +1034,7 @@ function createPDFCard(pdf, favoritesList, index = 0, highlightRegex = null) {
     const categoryIcon = categoryIcons[pdf.category] || 'fa-file-pdf';
 
     // Formatting Date
-    const formattedDate = new Date(pdf.uploadDate).toLocaleDateString('en-US', {
-        year: 'numeric', month: 'short', day: 'numeric'
-    });
+    const formattedDate = pdf._formattedDate;
 
     // Uses global escapeHtml() now
 

diff --git a/search_perf_test.js b/search_perf_test.js
@@ -0,0 +1,36 @@
+const pdfs = [];
+for (let i = 0; i < 1000; i++) {
+    pdfs.push({
+        title: "Introduction to Organic Chemistry",
+        description: "A comprehensive guide to organic chemistry principles.",
+        category: "Organic",
+        author: "John Doe"
+    });
+}
+
+const searchTerm = "organic";
+
+console.time('search_split');
+for(let i = 0; i < 10; i++) {
+    pdfs.filter(pdf => {
+        return pdf.title.toLowerCase().includes(searchTerm) ||
+            pdf.description.toLowerCase().includes(searchTerm) ||
+            pdf.category.toLowerCase().includes(searchTerm) ||
+            pdf.author.toLowerCase().includes(searchTerm);
+    });
+}
+console.timeEnd('search_split');
+
+console.time('precalc_searchStr');
+pdfs.forEach(p => {
+    p._searchStr = `${p.title} ${p.description} ${p.category} ${p.author}`.toLowerCase();
+});
+console.timeEnd('precalc_searchStr');
+
+console.time('search_precalc');
+for(let i = 0; i < 10; i++) {
+    pdfs.filter(pdf => {
+        return pdf._searchStr.includes(searchTerm);
+    });
+}
+console.timeEnd('search_precalc');