Scope, Closures, and this

Lexical scope decides which variables a function can see. A closure remembers variables from its outer scope. this depends on how a function is called (except arrows).

• Inner functions can read outer lets/consts.
• Closures power private state and callbacks.
• Prefer arrows for callbacks when you want lexical this.

function makeCounter() {
  let n = 0;
  return () => {
    n += 1;
    return n;
  };
}
const c = makeCounter();
console.log(c(), c());

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