// CALLBACKS IN Js

// A callback is a function passed as an argument to another function,

// which is then executed later (usually after an asynchronous operation).

// Callbacks were the earliest way to handle async code before Promises and async/await.

// EXAMPLE 1: SIMPLE CALLBACK

function greetUser(name, callback) {

console.log("Hi", name);

callback();

}

function sayBye() {

console.log("Goodbye!");

}

greetUser("David", sayBye);//output Hi David

// EXAMPLE 2: CALLBACK WITH A DELAY (ASYNC BEHAVIOR)

function fetchData(callback) {

console.log("Fetching data...");

setTimeout(() => {

console.log(" Data fetched!");

callback("Here is your data");

}, 2000);

}

fetchData((data) => {

console.log("Received:", data);

});

// EXAMPLE 3: CALLBACK HELL (NESTED CALLBACKS)

// Multiple callbacks lead to hard-to-read code (known as callback hell).

function stepOne(callback) {

setTimeout(() => {

console.log("Step 1 complete");

callback();

}, 1000);

}

function stepTwo(callback) {

setTimeout(() => {

console.log("Step 2 complete");

callback();

}, 1000);

}

function stepThree(callback) {

setTimeout(() => {

console.log("Step 3 complete");

callback();

}, 1000);

}

// Nested callbacks (messy structure)

stepOne(() => {

stepTwo(() => {

stepThree(() => {

console.log("All steps done!");

});

});

});