Home Questions Search Resources

Built for developers preparing for JavaScript, React & TypeScript interviews.

Resources Questions Support

Home Questions Search Progress

Home Questionsperformance

performance

Web performance optimization, metrics, and monitoring

Your Progress

0 of 5 completed

0%

5 Questions

senior Level

How do you identify and fix JavaScript runtime performance issues?

Use Chrome DevTools Performance tab to record and analyze flame charts, identify long tasks, and find layout thrashing. Common fixes include breaking up long tasks, avoiding forced synchronous layouts, using requestAnimationFrame, and moving work to Web Workers.

How do you identify and fix memory leaks in JavaScript applications?

Use Chrome DevTools Memory tab to take heap snapshots and compare them over time. Common leaks include detached DOM nodes, forgotten event listeners, closures holding references, and uncleared timers. Fix by proper cleanup in useEffect, removing listeners, and using WeakMap.

How do service workers improve performance and what caching strategies exist?

Service workers intercept network requests enabling offline support and advanced caching. Strategies include Cache First (fast, stale risk), Network First (fresh, slow), Stale While Revalidate (best UX), and Cache Only/Network Only for specific needs.

What is the Critical Rendering Path and how do you optimize it?

The Critical Rendering Path is the sequence of steps browsers take to render a page: HTML parsing, CSS parsing, render tree construction, layout, and paint. Optimize by minimizing critical resources, reducing file sizes, and removing render-blocking resources.

How do you set up performance monitoring for production applications?

Use Real User Monitoring (RUM) to collect Web Vitals from actual users. Tools like Google Analytics, Datadog, or custom solutions track metrics over time. Set up alerting for regressions, segment data by device/geography, and correlate with business metrics.