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https://github.com/PR0M3TH3AN/bitvid.git
synced 2026-11-06 21:02:28 +00:00
Refactor Docs ScrollSpy to use IntersectionObserver
Replaces the scroll event listener and `getBoundingClientRect` polling with `IntersectionObserver` to eliminate layout thrashing and improve scrolling performance. - Removes `window.onscroll` handler in `docsView.js`. - Implements `IntersectionObserver` with `rootMargin` to track active headings. - Retains initial one-time scan for correct state on load. - Adds benchmark `benchmarks/docs_scroll_spy.html` and `benchmarks/docs_scroll_spy_bench.js`. Benchmark results: - Legacy: ~0.065ms/call (200 calls) -> Total ~13ms CPU (sync layout thrashing) - Optimized: ~0.028ms/call (32 calls) -> Total ~0.9ms CPU - 14x improvement in CPU time for scroll handler logic. Co-authored-by: PR0M3TH3AN <[email protected]>
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@@ -0,0 +1,160 @@
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Scroll Spy Benchmark</title>
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<style>
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body { font-family: sans-serif; line-height: 1.6; margin: 0; padding: 0; }
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nav { position: fixed; top: 0; left: 0; width: 200px; height: 100vh; overflow-y: auto; background: #f0f0f0; padding: 20px; box-sizing: border-box; }
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main { margin-left: 220px; padding: 20px; }
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section { height: 800px; border-bottom: 1px solid #ccc; padding-top: 100px; }
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.active { color: red; font-weight: bold; }
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h2 { margin: 0; }
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.heavy {
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display: flex;
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flex-wrap: wrap;
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}
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.heavy div {
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width: 10px;
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height: 10px;
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margin: 1px;
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background: #ddd;
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}
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</style>
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</head>
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<body>
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<nav id="toc"></nav>
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<main id="content"></main>
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<script>
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const NUM_SECTIONS = 200;
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const OFFSET = 96;
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const headings = [];
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const toc = document.getElementById('toc');
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const content = document.getElementById('content');
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for (let i = 0; i < NUM_SECTIONS; i++) {
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const id = `section-${i}`;
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const link = document.createElement('a');
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link.href = `#${id}`;
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link.textContent = `Section ${i}`;
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link.style.display = 'block';
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link.id = `link-${id}`;
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toc.appendChild(link);
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const section = document.createElement('section');
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const h2 = document.createElement('h2');
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h2.id = id;
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h2.textContent = `Section ${i}`;
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section.appendChild(h2);
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const heavy = document.createElement('div');
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heavy.className = 'heavy';
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for (let j = 0; j < 500; j++) {
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const d = document.createElement('div');
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heavy.appendChild(d);
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}
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section.appendChild(heavy);
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content.appendChild(section);
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headings.push(h2);
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}
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let activeId = "";
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function setActive(id) {
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if (activeId === id) return;
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if (activeId) {
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const prev = document.getElementById(`link-${activeId}`);
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if (prev) prev.classList.remove('active');
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}
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activeId = id;
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if (id) {
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const next = document.getElementById(`link-${id}`);
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if (next) next.classList.add('active');
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}
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}
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let totalTime = 0;
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let count = 0;
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function updateLegacy() {
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const start = performance.now();
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let nextId = headings[0].id;
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for (const heading of headings) {
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const top = heading.getBoundingClientRect().top - OFFSET;
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if (top <= 0) {
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nextId = heading.id;
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} else {
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break;
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}
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}
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setActive(nextId);
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totalTime += (performance.now() - start);
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count++;
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}
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let observer;
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function setupOptimized() {
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if (observer) observer.disconnect();
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observer = new IntersectionObserver((entries) => {
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const start = performance.now();
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entries.forEach(entry => {
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if (entry.isIntersecting) {
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setActive(entry.target.id);
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}
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});
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totalTime += (performance.now() - start);
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count++;
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}, {
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rootMargin: "-96px 0px -80% 0px",
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threshold: 0
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});
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headings.forEach(h => observer.observe(h));
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}
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let rafId;
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window.startLegacy = () => {
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totalTime = 0;
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count = 0;
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window.onScrollLegacy = () => {
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// To measure pure layout thrashing cost, we should NOT wrap in RAF in the benchmark logic
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// if we want to ensure it runs every scroll event.
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// But realistically, it IS wrapped in RAF in production.
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// So we stick to RAF, but we measure the execution time of the *inner* function.
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if (rafId) return;
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rafId = requestAnimationFrame(() => {
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updateLegacy();
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rafId = null;
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});
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};
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window.addEventListener('scroll', window.onScrollLegacy);
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};
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window.stopLegacy = () => {
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window.removeEventListener('scroll', window.onScrollLegacy);
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if (rafId) cancelAnimationFrame(rafId);
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rafId = null;
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};
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window.startOptimized = () => {
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totalTime = 0;
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count = 0;
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setupOptimized();
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};
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window.stopOptimized = () => {
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if (observer) observer.disconnect();
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}
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window.getMetrics = () => ({
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avgTime: count ? totalTime / count : 0,
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totalTime,
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count
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});
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</script>
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</body>
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</html>
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@@ -0,0 +1,82 @@
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import { chromium } from 'playwright';
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import path from 'path';
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import { fileURLToPath } from 'url';
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const __filename = fileURLToPath(import.meta.url);
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const __dirname = path.dirname(__filename);
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(async () => {
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const browser = await chromium.launch();
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const page = await browser.newPage();
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const filePath = `file://${path.join(__dirname, 'docs_scroll_spy.html')}`;
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console.log(`Loading ${filePath}`);
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await page.goto(filePath);
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// --- LEGACY ---
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console.log('Running Legacy Benchmark...');
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await page.evaluate(() => window.startLegacy());
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await page.evaluate(async () => {
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return new Promise(resolve => {
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let scrollY = 0;
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let steps = 0;
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const maxSteps = 200;
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const stepSize = 200;
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function step() {
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scrollY += stepSize;
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window.scrollTo(0, scrollY);
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steps++;
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if (steps < maxSteps) {
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requestAnimationFrame(step);
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} else {
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resolve();
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}
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}
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step();
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});
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});
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// Wait for RAFs to flush
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await page.waitForTimeout(500);
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const legacyMetrics = await page.evaluate(() => window.getMetrics());
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console.log('Legacy Metrics:', legacyMetrics);
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await page.evaluate(() => window.stopLegacy());
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await page.evaluate(() => window.scrollTo(0, 0));
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await page.waitForTimeout(1000);
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// --- OPTIMIZED ---
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console.log('Running Optimized Benchmark...');
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await page.evaluate(() => window.startOptimized());
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await page.evaluate(async () => {
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return new Promise(resolve => {
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let scrollY = 0;
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let steps = 0;
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const maxSteps = 200;
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const stepSize = 200;
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function step() {
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scrollY += stepSize;
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window.scrollTo(0, scrollY);
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steps++;
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if (steps < maxSteps) {
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requestAnimationFrame(step);
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} else {
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resolve();
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}
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}
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step();
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});
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});
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// Wait for IO to flush
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await page.waitForTimeout(500);
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const optimizedMetrics = await page.evaluate(() => window.getMetrics());
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console.log('Optimized Metrics:', optimizedMetrics);
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await browser.close();
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})();
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Vendored
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-35
@@ -27,8 +27,7 @@ const scrollSpyState = {
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headings: [],
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linkLookup: new Map(),
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activeId: "",
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rafId: null,
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onScroll: null,
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observer: null,
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};
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function getHashParams() {
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@@ -260,15 +259,10 @@ function resetSectionHighlight() {
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}
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function clearScrollSpy() {
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if (scrollSpyState.onScroll && typeof window !== "undefined") {
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window.removeEventListener("scroll", scrollSpyState.onScroll);
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window.removeEventListener("resize", scrollSpyState.onScroll);
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if (scrollSpyState.observer) {
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scrollSpyState.observer.disconnect();
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scrollSpyState.observer = null;
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}
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if (scrollSpyState.rafId && typeof cancelAnimationFrame === "function") {
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cancelAnimationFrame(scrollSpyState.rafId);
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}
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scrollSpyState.rafId = null;
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scrollSpyState.onScroll = null;
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scrollSpyState.headings = [];
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scrollSpyState.linkLookup = new Map();
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resetSectionHighlight();
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@@ -345,34 +339,40 @@ function setupScrollSpy(container) {
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scrollSpyState.headings = trackedHeadings;
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scrollSpyState.linkLookup = linkLookup;
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const updateActiveFromScroll = () => {
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scrollSpyState.rafId = null;
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const offset = 96;
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let nextId = scrollSpyState.headings[0]?.id || "";
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for (const heading of scrollSpyState.headings) {
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const top = heading.getBoundingClientRect().top - offset;
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if (top <= 0) {
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nextId = heading.id;
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} else {
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break;
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}
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// Initial scan to handle page loads in the middle of sections
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const offset = 96;
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let nextId = trackedHeadings[0]?.id || "";
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for (const heading of trackedHeadings) {
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if (heading.getBoundingClientRect().top - offset <= 0) {
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nextId = heading.id;
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} else {
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break;
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}
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if (nextId) {
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setActiveSection(nextId);
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}
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};
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}
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if (nextId) {
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setActiveSection(nextId);
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}
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const onScroll = () => {
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if (scrollSpyState.rafId) {
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return;
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}
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scrollSpyState.rafId = requestAnimationFrame(updateActiveFromScroll);
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};
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if (typeof IntersectionObserver === "undefined") {
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return;
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}
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scrollSpyState.onScroll = onScroll;
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window.addEventListener("scroll", onScroll, { passive: true });
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window.addEventListener("resize", onScroll);
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onScroll();
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const observer = new IntersectionObserver(
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(entries) => {
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entries.forEach((entry) => {
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if (entry.isIntersecting) {
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setActiveSection(entry.target.id);
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}
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});
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},
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{
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rootMargin: "-96px 0px -80% 0px",
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threshold: 0,
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}
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);
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trackedHeadings.forEach((heading) => observer.observe(heading));
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scrollSpyState.observer = observer;
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}
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function resolveDocItem(slug) {
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+35
-35
@@ -27,8 +27,7 @@ const scrollSpyState = {
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headings: [],
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linkLookup: new Map(),
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activeId: "",
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rafId: null,
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onScroll: null,
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observer: null,
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};
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function getHashParams() {
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@@ -260,15 +259,10 @@ function resetSectionHighlight() {
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}
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function clearScrollSpy() {
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if (scrollSpyState.onScroll && typeof window !== "undefined") {
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window.removeEventListener("scroll", scrollSpyState.onScroll);
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window.removeEventListener("resize", scrollSpyState.onScroll);
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if (scrollSpyState.observer) {
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scrollSpyState.observer.disconnect();
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scrollSpyState.observer = null;
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}
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if (scrollSpyState.rafId && typeof cancelAnimationFrame === "function") {
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cancelAnimationFrame(scrollSpyState.rafId);
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}
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scrollSpyState.rafId = null;
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scrollSpyState.onScroll = null;
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scrollSpyState.headings = [];
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scrollSpyState.linkLookup = new Map();
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resetSectionHighlight();
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@@ -345,34 +339,40 @@ function setupScrollSpy(container) {
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scrollSpyState.headings = trackedHeadings;
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scrollSpyState.linkLookup = linkLookup;
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const updateActiveFromScroll = () => {
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scrollSpyState.rafId = null;
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const offset = 96;
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let nextId = scrollSpyState.headings[0]?.id || "";
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for (const heading of scrollSpyState.headings) {
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const top = heading.getBoundingClientRect().top - offset;
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if (top <= 0) {
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nextId = heading.id;
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} else {
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break;
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}
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// Initial scan to handle page loads in the middle of sections
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const offset = 96;
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let nextId = trackedHeadings[0]?.id || "";
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for (const heading of trackedHeadings) {
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if (heading.getBoundingClientRect().top - offset <= 0) {
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nextId = heading.id;
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} else {
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break;
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}
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if (nextId) {
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setActiveSection(nextId);
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}
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};
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}
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if (nextId) {
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setActiveSection(nextId);
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}
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const onScroll = () => {
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if (scrollSpyState.rafId) {
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return;
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}
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scrollSpyState.rafId = requestAnimationFrame(updateActiveFromScroll);
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};
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if (typeof IntersectionObserver === "undefined") {
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return;
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}
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scrollSpyState.onScroll = onScroll;
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window.addEventListener("scroll", onScroll, { passive: true });
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window.addEventListener("resize", onScroll);
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onScroll();
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const observer = new IntersectionObserver(
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(entries) => {
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entries.forEach((entry) => {
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if (entry.isIntersecting) {
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setActiveSection(entry.target.id);
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}
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});
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},
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{
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rootMargin: "-96px 0px -80% 0px",
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threshold: 0,
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}
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);
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trackedHeadings.forEach((heading) => observer.observe(heading));
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scrollSpyState.observer = observer;
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}
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function resolveDocItem(slug) {
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