The answer
A closure holds a reference to its lexical environment. As long as the closure is reachable, the environment (and all its variables) cannot be garbage collected. If closures accumulate or keep large objects alive, memory grows unbounded.
Closures and Memory Leaks in JavaScript
How do closures cause memory leaks in JavaScript?
More FAQs in Closures and Memory Leaks in JavaScript
Accumulating handlers in arrays, forgotten timers (setInterval never cleared), event listeners on detached DOM elements, unbounded caches of closures, and accidental closures that keep large objects alive without using them.
Remove event listeners when done, clear timers with clearInterval/clearTimeout, use WeakMap or WeakRef for weak references, bound cache size (LRU), and extract only what you need instead of closing over large objects.
Use Chrome DevTools Memory tab: take heap snapshots, compare them, look for growing retained size. Use the Performance tab to record memory usage over time. Check performance.memory.usedJSHeapSize (Chrome only) for programmatic monitoring.
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