When should you use closures in JavaScript?
For data privacy, callbacks that access outer variables, functional utilities (memoize, once, debounce, throttle, curry), and the module pattern. Use them when you need a function to remember its lexical scope.
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More FAQs in Closures: Advantages and Disadvantages in JavaScript
Data privacy (true private state), state persistence across calls, enabling functional programming (currying, memoization, composition), powering callbacks and event handlers, the module pattern, and avoiding global pollution.
Memory consumption (closed-over variables are not GC'd until the closure is), potential memory leaks, harder to debug (closed-over variables are not always visible), harder to test (private state), and added complexity with deeply nested closures.
Avoid closing over large objects unnecessarily (extract what you need), avoid accumulating closures that keep big data in long-lived arrays, and avoid closures for simple state where a plain object or class is simpler.
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