# Callbacks in JavaScript: Why They Exist

If you’ve been learning JavaScript, you’ve definitely seen the word callback.

At first it feels like:

Okay... it's a function... but why is it passed inside another function???

---

What is a Callback?

A callback is simply a function passed into another function.

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

function sayBye() {
  console.log("Bye!");
}

greet("Umer", sayBye);

---

Why Callbacks Exist

1. Handling Asynchronous Code

• API calls
• Fetching data

2. Event Handling

• Button clicks
• User actions

3. Non-blocking Design

JavaScript can run other code while waiting.

---

Final Thoughts

Callbacks may feel confusing at first, but once you understand why they exist, everything becomes clear.