Is an inner function always a closure in JavaScript?

JavaScript Closures vs. Anonymous Functions

In JavaScript, a closure occurs when an inner function has access to the outer scope's variables, even after the outer function has completed execution. Many functions in JavaScript are considered closures, but only a specific subset is of particular interest theoretically.

Case 1: Friend's Code

<code class="js">(function f() {
  var i2 = i;
  setTimeout(function g() {
    console.log(i2);
  }, 1000);
})();</code>

• Function f is not a closure because none of its free variables are closed over. However,
• Function g is a closure for the free variable i2. The variable i2 is captured when g is created.

Case 2: Your Code

<code class="js">setTimeout((function f(i2) {
  return function g() {
    console.log(i2);
  };
})(i), 1000);</code>

• Function f is not a closure because it has no free variables.
• Function g is a closure for the free variable i2. The variable i2 is captured when g is created.

Conclusion

Therefore, in both the provided solutions, the inner function g is a closure, but not the outer ones. This demonstrates that although they achieve the same result, they do so through different mechanisms.

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