What is WeakRef in JavaScript and when would you use it with closures?
WeakRef (ES2021) holds a weak reference to an object. The GC can free the object even if the WeakRef exists. Use it when a closure needs optional access to an object that should not prevent GC.
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More FAQs in Closures and the Garbage Collector in JavaScript
Closures hold a reference to their lexical environment, keeping all closed-over variables reachable. As long as the closure is reachable, the GC cannot free those variables. This is useful for data privacy but can cause memory growth.
Extract only what you need (close over len, not the whole array), null references when done (use let instead of const), use WeakMap for caches (keys are weakly held), and use WeakRef for optional references.
WeakMap keys are weakly held. When a key is garbage collected, the entry is automatically removed. This prevents memory leaks in caches where closures might otherwise keep keys alive forever.
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