Closures and Scope

Key points

1. 1

   A closure is a function plus the variables it can reach from where it was defined, even after the outer function returns.

2. 2

   var is function-scoped and hoisted as undefined; let and const are block-scoped and sit in a temporal dead zone until declared.

3. 3

   Closures in a var loop share one variable; let gives each iteration its own binding.

4. 4

   Factories (functions returning functions) use closures to keep private state, like a counter.

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• Closures
• let