A practical guide to JavaScript memory management: explains GC’s mark-and-sweep, shows how globals, event listeners, closures, and circular references trigger leaks, and outlines fixes—use WeakRef/FinalizationRegistry, remove listeners, structure closures, break cycles, monitor/profile, and optimize data. Extends to full-stack (lean APIs, front-end optimizations, DB queries) with an e-commerce example to build scalable, reliable apps.