Tag: MDN

A practical guide to JavaScript lookbehind assertions: what they are, when to use them, real-world examples, browser/Node compatibility notes, and fallbacks for older environments.

A practical, example-driven guide to the Periodic Background Sync API - how it works, when to use it, code samples, browser support, security considerations, and production-ready best practices for keeping your web app data fresh while respecting battery and privacy.

Learn how to use the PerformanceObserver API to capture real, user-centric performance metrics (LCP, FCP, CLS, FID/INP, long tasks), send them for analysis, set SLOs, and iterate on improvements with code examples, percentile calculations, and real-world optimizations.

Learn how to use the File System Access API to open, read, edit, save and manage files and directories from the browser. Includes hands‑on examples, permission handling, fallbacks and best practices.