Can closures cause memory leaks 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.

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.