Nested Functions

Last Updated: 22nd October 2025

A nested function is a function inside another function.
The inner function can only be accessed inside the outer function.

Hinglish Tip 🗣: Nested function ka matlab hota hai — ek function ke andar doosra function. Inner function bahar se call nahi hota, sirf outer function ke andar hi use hota hai.

✏️ Syntax

function outerFunction() {
  console.log("This is the outer function");

  function innerFunction() {
    console.log("This is the inner function");
  }

  innerFunction(); // Call inner function here
}

outerFunction();

📚 Key Points

  • The inner function can access variables of the outer function.
  • But the outer function cannot access variables of the inner function.
  • Useful in data hiding, closures, and modular programming.
function greetUser() {
  let name = "Ravi";

  function showMessage() {
    console.log("Hello " + name + "! 👋");
  }

  showMessage();
}

greetUser();

Hinglish Tip 🗣: Inner function outer variable ko use kar sakta hai — yehi concept baad me Closure me kaam aayega.

Need of Nested Functions?

  • To group related logic together.
  • To limit variable scope (data hiding).
  • Used in closures, callback patterns, and modular design.

💡 Quick Practice

  • Create a function calculate() with an inner function add() that adds two numbers.
  • Try to call the inner function from outside — observe what happens.
  • Modify your code to print both messages (“outer called”, “inner called”).
  • Exercise Set 1
  • Exercise Set 2
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