Frontend

This write-up condenses the published DEV tutorial “Browser-based performance testing with K6” into an actionable walkthrough for frontend teams. Why k6 browser Simulates real browser interactions (Chromium) vs. protocol-only tests. Captures Web Vitals (LCP/INP/CLS) and UX signals (spinners, interactivity). Reuses familiar k6 scripting with async/await + locators. Setup Install k6 (latest) and ensure Node/npm are available. Project skeleton: k6-tests/ libs/ # flows (login, add to cart, checkout) pages/ # Page Object Model classes tests/ # test entry scripts utils/ # shared options (browser config, VUs, iterations) Configure browser scenario (utils/k6-options.js): export const browserOptions = { scenarios: { ui: { executor: "shared-iterations", vus: 1, iterations: 15, options: { browser: { type: "chromium" } }, }, }, }; Example flow (simplified) import { browser } from "k6/browser"; import { check } from "k6"; export const options = browserOptions; export default async function () { const page = await browser.newPage(); await page.goto("https://www.saucedemo.com/"); await page.locator("#user-name").type("standard_user"); await page.locator("#password").type("secret_sauce"); await page.locator("#login-button").click(); check(page, { "login ok": () => page.locator(".title").textContent() === "Products" }); await page.close(); } Running & reporting CLI run: k6 run ./tests/buyItemsUserA.js Live dashboard: K6_WEB_DASHBOARD=true K6_WEB_DASHBOARD_OPEN=true k6 run ... Export HTML report: K6_WEB_DASHBOARD=true K6_WEB_DASHBOARD_EXPORT=results/report.html Metrics to watch (aligns to Core Web Vitals) browser_web_vital_lcp — largest content paint; target < 2.5s p75. browser_web_vital_inp — interaction to next paint; target < 200ms p75. browser_web_vital_cls — layout shift; target < 0.1. Add custom checks for “spinner disappears”, “cart count”, “success message”. Tips Keep tests short and focused; one scenario per file. Reuse Page Objects for maintainability. Run with realistic VUs/iterations that mirror expected traffic. Use screenshots on failure for debuggability (page.screenshot()). Takeaway: k6 browser mode gives frontend teams reproducible, scriptable UX performance checks—ideal for catching regressions before they reach real users.

This post distills the key ideas from the published DEV article “Frontend Performance Optimization: A Comprehensive Guide 🚀” into a concise, production-focused playbook. What matters Fast first paint and interaction: prioritize above-the-fold content, cut JS weight, avoid layout shifts. Ship less: smaller bundles, fewer blocking requests, cache aggressively. Ship smarter: load what’s needed when it’s needed (on demand and in priority order). Core techniques 1) Selective rendering Render only what is visible (e.g., IntersectionObserver + skeletons). Defer heavy components until scrolled into view. 2) Code splitting & dynamic imports Split by route/feature; lazy-load non-critical views. Example (React): const Page = lazy(() => import("./Page")); <Suspense fallback={<div>Loading…</div>}> <Page /> </Suspense>; 3) Prefetching & caching Prefetch likely-next routes/assets (<link rel="prefetch"> or router prefetch). Pre-warm API data with React Query/Next.js loader functions. 4) Priority-based loading Preload critical CSS/hero imagery: <link rel="preload" as="style" href="styles.css">. Use defer/async for non-critical scripts. 5) Compression & transfer Enable Brotli/Gzip at the edge; pre-compress static assets in CI/CD. Serve modern formats (AVIF/WebP) and keep caching headers long-lived. 6) Loading sequence hygiene Order: HTML → critical CSS → critical JS → images/fonts → analytics. Avoid long main-thread tasks; prefer requestIdleCallback for non-urgent work. 7) Tree shaking & dead-code elimination Use ESM named imports; avoid import *. Keep build in production mode with minification + module side-effects flags. Measurement & guardrails Track Core Web Vitals (LCP, INP, CLS) plus TTFB and bundle size per release. Run Lighthouse/WebPageTest in CI; fail builds on regressions above agreed budgets. Monitor real-user metrics (RUM) to validate improvements after deploys. Quick starter checklist Lazy-load routes and heavy widgets. Preload hero font/hero image; inline critical CSS if needed. Turn on Brotli at CDN; cache static assets with versioned filenames. Set performance budgets (JS < 200KB gz, LCP < 2.5s p75, INP < 200ms). Automate audits in CI and watch RUM dashboards after each release. Bottom line: Combine “ship less” (smaller, shaken, compressed bundles) with “ship smarter” (prioritized, on-demand loading) and enforce budgets with automated checks to keep your app fast over time.

This article summarizes the DEV post “How to Use React Query for Efficient Data Fetching” and focuses on a minimal, production-ready setup. Why React Query (TanStack Query) Handles fetching, caching, retries, background refresh, and deduping. Removes useEffect + manual loading/error state boilerplate. Scales to pagination, infinite scroll, and SSR hydration. 3-step setup Install: npm install @tanstack/react-query Create a client and wrap your app: import { QueryClient, QueryClientProvider } from "@tanstack/react-query"; const queryClient = new QueryClient(); const App = () => ( <QueryClientProvider client={queryClient}> <MyComponent /> </QueryClientProvider> ); Fetch with useQuery: import { useQuery } from "@tanstack/react-query"; function UsersList() { const { data, isLoading, error } = useQuery({ queryKey: ["users"], queryFn: () => fetch("/api/users").then((r) => r.json()), }); if (isLoading) return <p>Loading…</p>; if (error) return <p>Something went wrong</p>; return <ul>{data.map((u) => <li key={u.id}>{u.name}</li>)}</ul>; } Features you get “for free” Auto refetch on window focus/network reconnect. Stale-while-revalidate caching with configurable TTLs. Retries with exponential backoff for transient failures. Query invalidation to refresh related data after mutations. Devtools for live inspection of query states. Power tips Prefetch likely-next routes to hide latency (e.g., on hover). Use useInfiniteQuery for endless scroll; surface hasNextPage/fetchNextPage. Pass auth tokens via queryFnContext; centralize fetcher. For SSR/Next.js, hydrate with dehydrate/Hydrate to avoid waterfalls. Performance guardrails Set per-query stale times and retry counts to balance freshness vs. load. Log slow queries and cache hit rate; watch INP/LCP when triggering refetches. Keep query keys stable and descriptive (e.g., ["post", postId]). Bottom line: React Query removes state-management overhead for remote data and delivers faster, more resilient UIs with minimal code.

Web design is constantly evolving. Here are the modern design styles every frontend developer should know in 2025. 1. Glassmorphism Glassmorphism creates a frosted glass effect with: Semi-transparent backgrounds Backdrop blur filters Subtle borders Layered depth Implementation .glass-card { background: rgba(255, 255, 255, 0.1); backdrop-filter: blur(10px); border: 1px solid rgba(255, 255, 255, 0.2); box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1); border-radius: 16px; } Use Cases Cards and modals Navigation bars Overlays Dashboard elements 2. Neumorphism Neumorphism (soft UI) creates a soft, extruded look: ...

Vue is introducing support for declarative UI syntax, bringing it closer to mobile development patterns seen in Kotlin and Swift. This new approach moves away from traditional HTML templates, offering a more modern, type-safe way to build user interfaces. The Evolution Traditional Vue templates use HTML: <template> <div class="container"> <h1>{{ title }}</h1> <button @click="handleClick">Click me</button> </div> </template> The new declarative syntax is more similar to SwiftUI or Jetpack Compose: <script setup> import { View, Text, Button } from "vue-declarative"; const title = ref("Hello World"); function handleClick() { console.log("Clicked!"); } </script> <template> <View class="container"> <Text>{{ title }}</Text> <Button onPress="{handleClick}">Click me</Button> </View> </template> Key Benefits 1. Type Safety The declarative syntax provides better TypeScript support: ...

Don’t just be a tool user! Let’s build a frontend error monitoring SDK from scratch. This hands-on guide will walk you through creating your own error tracking system. Why Build Your Own SDK? While there are excellent error monitoring services like Sentry, Rollbar, and Bugsnag, building your own SDK helps you: Understand how error monitoring works under the hood Customize error tracking to your specific needs Learn valuable debugging and monitoring concepts Reduce dependency on third-party services Core Features Our SDK will include: ...

Debugging is an essential skill for any developer, but it can be time-consuming. Here are practical strategies that helped me cut my debugging time in half. 1. Use Browser DevTools Effectively Master the Chrome DevTools or Firefox Developer Tools: Breakpoints: Set breakpoints strategically, not just on errors Network Tab: Monitor API calls and identify slow requests Performance Tab: Profile your application to find bottlenecks Console: Use console.table() for better data visualization 2. Leverage AI-Powered Debugging Tools Modern AI tools can significantly speed up debugging: ...

Based on the DEV article “Building Performant UI with Rust, WebAssembly, and Tailwind CSS,” this summary focuses on the architecture and steps to integrate the stack. Why Rust + WASM Offload CPU-heavy tasks (parsing, transforms, image ops) from the JS main thread. Near-native speed with memory safety. Keeps UI responsive while heavy logic runs in WASM. Why Tailwind here Utility-first styling keeps CSS minimal and predictable. Co-locate styles with components; avoid global collisions. Fast to iterate on responsive layouts for WASM-powered widgets. Integration workflow Compile Rust to WASM with wasm-pack/wasm-bindgen. Import the .wasm module via your bundler (Vite/Webpack/esbuild) and expose JS bindings. Call Rust functions from JS; render results in Tailwind-styled components. Use containers like overflow-x-auto, max-w-full, sm:rounded-lg to keep WASM widgets responsive. Example flow (pseudo) // rust-lib/src/lib.rs (simplified) #[wasm_bindgen] pub fn summarize(data: String) -> String { // heavy work here... format!("size: {}", data.len()) } // web/src/useSummarize.ts import init, { summarize } from "rust-wasm-lib"; export async function useSummarize(input: string) { await init(); return summarize(input); } Performance notes Keep WASM modules small; lazy-load them when the feature is needed. Avoid blocking the main thread—invoke WASM in response to user actions, not eagerly. Profile with browser DevTools + wasm-bindgen debug symbols when needed. Design principles Establish Tailwind design tokens/utilities for spacing/typography early. Encapsulate WASM widgets as reusable components with clear props. Reserve space to prevent layout shifts when results arrive. Good fits Data/analytics dashboards, heavy transforms, visualization prep. Fintech/scientific tools where CPU work dominates. Developer tools needing deterministic, fast processing in-browser. Takeaway: Let Rust/WASM handle the heavy lifting while Tailwind keeps the UI lean and consistent—yielding responsive, performant web experiences.

Security is crucial in web development. Here are essential security practices to protect your applications. 1. Authentication & Authorization Strong Password Policies // Enforce strong passwords const passwordRegex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$/; // Hash passwords (never store plaintext) const hashedPassword = await bcrypt.hash(password, 10); JWT Best Practices // Use short expiration times const token = jwt.sign( { userId: user.id }, process.env.JWT_SECRET, { expiresIn: '15m' } ); // Implement refresh tokens // Store tokens securely (httpOnly cookies) 2. Input Validation Server-Side Validation // Always validate on server const schema = z.object({ email: z.string().email(), password: z.string().min(8), age: z.number().min(18).max(120) }); const validated = schema.parse(req.body); Sanitize Inputs // Prevent XSS const sanitized = DOMPurify.sanitize(userInput); // Prevent SQL Injection (use parameterized queries) db.query('SELECT * FROM users WHERE id = ?', [userId]); 3. HTTPS & SSL/TLS // Always use HTTPS in production // Redirect HTTP to HTTPS // Use HSTS headers app.use((req, res, next) => { if (!req.secure && process.env.NODE_ENV === 'production') { return res.redirect(`https://${req.headers.host}${req.url}`); } next(); }); 4. CORS Configuration // Configure CORS properly app.use(cors({ origin: process.env.ALLOWED_ORIGINS.split(','), credentials: true, methods: ['GET', 'POST', 'PUT', 'DELETE'], allowedHeaders: ['Content-Type', 'Authorization'] })); 5. Rate Limiting // Prevent brute force attacks const rateLimit = require('express-rate-limit'); const limiter = rateLimit({ windowMs: 15 * 60 * 1000, // 15 minutes max: 5 // limit each IP to 5 requests per windowMs }); app.use('/api/login', limiter); 6. SQL Injection Prevention // Always use parameterized queries // Bad db.query(`SELECT * FROM users WHERE email = '${email}'`); // Good db.query('SELECT * FROM users WHERE email = ?', [email]); 7. XSS Prevention // Escape user input const escapeHtml = (text) => { const map = { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#039;' }; return text.replace(/[&<>"']/g, m => map[m]); }; // Use Content Security Policy app.use((req, res, next) => { res.setHeader('Content-Security-Policy', "default-src 'self'; script-src 'self'"); next(); }); 8. CSRF Protection // Use CSRF tokens const csrf = require('csurf'); const csrfProtection = csrf({ cookie: true }); app.use(csrfProtection); app.get('/form', (req, res) => { res.render('form', { csrfToken: req.csrfToken() }); }); 9. Security Headers // Set security headers app.use((req, res, next) => { res.setHeader('X-Content-Type-Options', 'nosniff'); res.setHeader('X-Frame-Options', 'DENY'); res.setHeader('X-XSS-Protection', '1; mode=block'); res.setHeader('Strict-Transport-Security', 'max-age=31536000'); next(); }); 10. Dependency Security # Regularly update dependencies npm audit npm audit fix # Use tools like Snyk, Dependabot 11. Error Handling // Don't expose sensitive information app.use((err, req, res, next) => { if (process.env.NODE_ENV === 'production') { res.status(500).json({ error: 'Internal server error' }); } else { res.status(500).json({ error: err.message }); } }); 12. Logging & Monitoring // Log security events logger.warn('Failed login attempt', { ip: req.ip, email: req.body.email, timestamp: new Date() }); // Monitor for suspicious activity Best Practices Summary Strong authentication Input validation & sanitization Use HTTPS Configure CORS properly Implement rate limiting Prevent SQL injection Prevent XSS CSRF protection Security headers Keep dependencies updated Proper error handling Monitor security events Conclusion Security requires: ...