Garbage collection

JavaScript uses automatic memory management. Collectors free objects that are no longer reachable from roots (global object, current stack, closures in scope).

If any reference path remains — closure, cache, listener, timer, DOM node, global — the object stays alive. Setting a local variable to `null` rarely fixes a leak if another path retains it.

`FinalizationRegistry` is not a reliable business-logic cleanup mechanism.

On interviews, explain the concept with a concrete example and name the runtime behavior interviewers probe.

Common pitfalls include mixing similar APIs and forgetting edge cases during live coding.

The trade-off is often clarity versus performance or safety versus convenience.

Checklist:

• Reason from roots and reachability.
• Find retaining references in DevTools.
• Clean listeners and timers on teardown.