How do event handlers use closures in JavaScript?
A handler defined inside a setup function closes over the local variables (like a count or an element reference). Each event fires the handler, which can read and update those closed-over variables.
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More FAQs in Closures and the Scope Chain: Real-World Examples
By declaring a variable inside a function and returning methods that access it. The variable is not accessible directly from outside, only through the returned methods. This is the module pattern.
The memoize function closes over a cache object. The returned function checks and updates the cache without exposing it. Each call returns the cached result if available, otherwise computes and stores it.
Because let creates a fresh binding per iteration. Each callback closes over its own copy of i, so they log 0, 1, 2. With var, all callbacks share one i, so they all log the final value.
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