Understanding Closures in JavaScript – Explained Like You’re 5

Ever heard of the term “closure” in JavaScript and thought, “That sounds complex”? You’re not alone. But the truth is — closures are simple but powerful, and they play a major role behind the scenes in many JavaScript features like callbacks, private variables, and currying.

In this blog, we’ll break down closures in a fun and easy way with examples you’ll remember forever.

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🧠 What is a Closure?

A closure is when a function remembers the variables from the place where it was created, even if it’s called somewhere else.

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📦 Think of It Like a Backpack

Imagine a function carrying a backpack of variables with it. Even if that function is used later or somewhere else, it still has access to what’s inside that backpack.

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✅ Basic Example

javascriptCopyEditfunction outer() {
  let name = "Codey";

  function inner() {
    console.log("Hello, " + name);
  }

  return inner;
}

const greet = outer(); // outer() runs and returns inner()
greet(); // Outputs: Hello, Codey

Even though outer() has finished running, inner() still remembers name.

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🔒 Creating Private Variables

Closures allow us to protect data — variables that cannot be accessed directly from outside.

javascriptCopyEditfunction createCounter() {
  let count = 0;

  return function () {
    count++;
    return count;
  };
}

const counter = createCounter();
console.log(counter()); // 1
console.log(counter()); // 2
console.log(counter()); // 3

count is private — only the inner function can access it.

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🧰 Real Use Cases of Closures

• Event handlers
• setTimeout / setInterval
• Data privacy (private state)
• Currying and partial functions
• Maintaining state without classes

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🧪 Closure with setTimeout

javascriptCopyEditfunction delayLog() {
  for (let i = 1; i <= 3; i++) {
    setTimeout(function () {
      console.log("i =", i);
    }, i * 1000);
  }
}

delayLog();
// Outputs:
// i = 1 (after 1s)
// i = 2 (after 2s)
// i = 3 (after 3s)

Because of closures and let, each timeout remembers its own copy of i.

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❓ Why Do Closures Matter?

• Helps you manage memory and avoid polluting global scope
• Enables powerful patterns like modules and callbacks
• Used in frameworks (React Hooks rely on closures!)