Garbage Collection in JavaScript Engines

JavaScript engines use generational garbage collectors to reclaim memory from unreachable objects.

Basics

• Young generation: Short-lived objects collected frequently.
• Old generation: Long-lived objects collected less often.
• Stop-the-world pauses: GC can pause execution, so avoid heavy allocations in hot paths.

Common leak patterns

• Detached DOM nodes held by closures.
• Event listeners not removed on cleanup.
• Global caches with no eviction policy.

How to monitor

• Use Chrome DevTools Memory panel for heap snapshots.
• Track long tasks and allocation spikes.

Interview prompt

• Describe how you would find a memory leak in a React app.