Callback Functions and Higher-Order Functions: A Tale of Two Coders

The Day Callback Functions Changed My Life

 
It was raining.
 
Not the nice kind. Not the soft drizzle that makes you crave chai and samosas. No. This was that relentless kind. Grey sky. Heavy mood. Laptop screaming errors at me. My deadline? Oh, it was breathing down my neck.
 
I was stuck.
 
Nothing worked. Console full of red. Coffee long gone cold. I was seconds away from rage-quitting and blaming JavaScript for my life choices.
 
Then, he walked in.

My mentor. Let's call him Dhoni. Cool, composed, always weirdly calm during chaos. He leaned over, looked at my screen for barely 3 seconds, and whispered—
 

"Ever tried using a callback?"

 
Callback? The word hit me like a bouncer. Callback? What’s that—some cricketing term? Or like... a missed call?
 
But Dhoni smiled. The kind of smile that says, “You’ll thank me later.”
 
 

"A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action."

That’s what the books say.
 
But let’s be honest?
 
It’s just a way for your code to say, “Hey, I’m done with this. You take over now.”
Like programming tag-team wrestling. Or relay race. Or friendship.
 
I tried it.
 
And boom. The code worked. No red. Just smooth green logs. I grinned. Dhoni fist-bumped me. The rain? Still going. But inside? Sunshine.
 
 

Enter: Higher-Order Functions

 
Next day. Same desk. Same storm outside. But me? I was different.
 
Confident. Bold. Like Virat after smashing a ton. I wanted more. Wanted to push the limits.
 
That's when Dhoni dropped another gem—
 “Now meet higher-order functions.”

Functions that can take in functions. Or return them. Yeah, you heard right.
 
It felt... illegal.
 
A function. Passing around other functions. Like party invites. Or top-secret envelopes.
 
Here’s what I did:
 

function greet(name, callback) {
  console.log("Hey " + name + ", you there?");
  callback();
}

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

greet("monadarlo", sayBye);

You see that?
 
The name "monadarlo"—not just a string. It became a ritual. A secret handshake. An inside joke with my code.

Here’s another one I cooked up. 

It was a boring afternoon. Bugs fixed. Coffee hot. So, I played around. 

I thought—what if I could decide how someone gets greeted?
Like, formal or casual. Friendly or robotic. Based on mood. 

So, I built this: 

function casualGreeting(name) {
  console.log(`Yo ${name}! What's up?`);
}

function formalGreeting(name) {
  console.log(`Good evening, Mr./Ms. ${name}.`);
}

function greetPerson(name, greeterFunc) {
  greeterFunc(name);
}

greetPerson("monadarlo", casualGreeting);
// Output: Yo monadarlo! What's up?

greetPerson("monadarlo", formalGreeting);
// Output: Good evening, Mr./Ms. monadarlo.

Output:

Yo monadarlo! What's up?
Good evening, Mr./Ms. monadarlo.

See that?
 
The greetPerson function doesn’t care how the greeting happens.
 It just trusts the function you give it. Like—
 “Here, you take the wheel.”
 
That’s higher-order.
That’s power.
 
It’s like letting your code choose the vibe.
 
And yeah, “monadarlo” still gets all the attention.

Why This Matters (Even If You’re Just Starting Out)

 
Here’s the thing.
 Callbacks and higher-order functions aren’t just fancy dev talk.
They’re game-changers.

Want your code to wait for something before running the next step?
Callbacks.

Need less repetitive, cleaner, more elegant code?
Higher-order functions.

Wanna impress your peers?
Casually drop “monadarlo” in a function call. Watch them pause.

These concepts? They make your code feel... alive. Like it knows when to wait. When to act. When to pass control. Like Pant behind the stumps. Quick. Adaptive. A little wild. 

When the Magic Breaks

 
It’s not all sunshine.
 
Callbacks can get... messy.
 One inside another. Then another. Then three more.
 Until your screen looks like spaghetti.
 
That’s called callback hell.
And trust me—you don’t want to live there.

At some point, you’ll scream. Or stare blankly. Or Google "why JavaScript hates me."

But let’s actually see it. Here’s a fresh mess:
 

function getUser(id, callback) {
  setTimeout(() => {
    console.log(`Got user with ID: ${id}`);
    callback(id);
  }, 500);
}

function getOrders(userId, callback) {
  setTimeout(() => {
    console.log(`Fetched orders for user: ${userId}`);
    callback(userId);
  }, 500);
}

function getOrderDetails(orderId, callback) {
  setTimeout(() => {
    console.log(`Fetched details for order: ${orderId}`);
    callback();
  }, 500);
}

getUser(101, function (userId) {
  getOrders(userId, function (orderId) {
    getOrderDetails(orderId, function () {
      console.log("All data fetched successfully.");
    });
  });
});

Output:

Got user with ID: 101  
Fetched orders for user: 101  
Fetched details for order: 101  
All data fetched successfully.

It works. It really does.
 But it’s not nice to look at. Harder to debug. Worse to scale.
 If something breaks in the second function? Good luck finding it in this nested mess.
 
 
So what do you do?
 
Breathe.
 Refactor it. Try promises. Try async/await. Flatten it down. Clean it up.
 
Or just call Dhoni.
 He’ll probably ask if you’ve slept and tell you to use async/await. And he’ll be right.

One More Thing... Closures

 
So there I was. Fixing callback hell. Refactoring things. Making it all pretty.
 
Then Dhoni said something else.
 “Ever wondered how your callback remembers stuff? Even after the outer function's gone?”

I paused. That sounded... spooky.

But it’s not magic. It’s called a closure.
 

A closure is when a function “remembers” the variables from the place where it was created—even if that place is gone.

Closures are like little memory boxes your functions carry.
 Even after the function that created the variable has finished running, the inner function still remembers it.
 
Yeah. It remembers.
 Even when the scope it came from is long gone.
 
Here’s a quick peek:
 

function outer() {
  let name = "monadarlo";

  return function inner() {
    console.log("Hey " + name);
  };
}

const greet = outer();
greet(); // Output: Hey monadarlo

See that?
 
inner() still remembers name.
 Even though outer() is long done and gone. That’s a closure.
 
And here’s the thing:
 
That’s actually how callbacks work underneath.
It’s the secret sauce.

They reach back.
Grab the variables.
Use them.
Even though, technically, they shouldn’t be there anymore.

And once I got that?
Callbacks, async code, event listeners—everything just started making sense.

If this sounds confusing (and honestly, it did confuse me for a while), I’ve written a whole story around it. With cricket, and silly examples, and all the fun stuff.

👉 Check out this blog on Closures in JavaScript
You’ll thank yourself later.

It’s the missing puzzle piece.
The quiet genius behind your callbacks.
The reason your code remembers.

Array Methods: Your First Brush with Higher-Order Power

 
Okay, so let’s shift gears.
 Callbacks are tricky, yeah. But they also open doors.
 
The first time most of us use higher-order functions?
It’s not in some async jungle. It’s right there, in the humble array methods.

Yeah—map, forEach, filter, find, some, every.
They all accept functions. Which means—they’re higher-order.
 
Take this one for example:
 

const players = [
  { name: "Rohit", score: 85 },
  { name: "Hardik", score: 45 },
  { name: "Ashwin", score: 68 },
];

players.forEach(function (player) {
  console.log(`${player.name} scored ${player.score}`);
});

Output:

Rohit scored 85  
Hardik scored 45  
Ashwin scored 68

Simple. Clear. The forEach method accepts a function and runs it on every element.
Boom. Higher-order function.
 
It’s the kind of thing you use before you even realize it’s fancy.
But it is.
 
 

Timer Events: The Ticking Heartbeat of JS

 
Let’s talk time. And ticking.
 
Two built-in legends in JavaScript: setTimeout and setInterval.
 
They take functions. And run them later.
 
That’s it. Simple. Sneaky powerful.
 

setTimeout(function () {
  console.log("Hey! You waited for this message.");
}, 2000);

// Output (after 2 seconds): Hey! You waited for this message.

The clock ticks. Time passes. Then boom—it runs your function. Once.
 
Now here’s setInterval:
 

setInterval(function () {
  console.log("I’ll keep printing this until you stop me.");
}, 3000);

Output:

I’ll keep printing this until you stop me.  
I’ll keep printing this until you stop me.  
(repeats every 3 seconds)

It’s like your annoying cousin who won’t stop texting.
 Useful, but… only if you handle it right.
 
Still, notice the pattern?
 Both accept functions. Both are higher-order.
 
 

Creating Your Own Higher-Order Functions

 
So far we’ve used built-ins.
 Now let’s make one. From scratch.
 
Let’s say you wanna greet someone. First name, last name, a polite message.
 
Here’s one way to do it:
 

function greetCustomer(firstName, lastName, greeting) {
  const fullName = `${firstName} ${lastName}`;
  console.log(`${greeting} ${fullName}`);
}

greetCustomer("Priya", "Mehra", "Namaste");
// Output: Namaste Priya Mehra

Looks okay. But wait.
 
This function is doing too much.
 It’s combining names and greeting people. That’s two jobs. That’s too much.
 
Let’s split it up.
 

function combineName(first, last) {
  return `${first} ${last}`;
}

Clean. Focused. This one just combines the names.
 
Now we use it in our main function:
 

function greetCustomer(nameFunc, firstName, lastName, greeting) {
  const fullName = nameFunc(firstName, lastName);
  console.log(`${greeting} ${fullName}`);
}

greetCustomer(combineName, "Priya", "Mehra", "Namaste");
// Output: Namaste Priya Mehra

See what happened?
 
greetCustomer now takes a function (nameFunc). Which makes it—you guessed it—a higher-order function.
 
Now every part of the code does exactly what it should. Nothing more.
 
And that’s the beauty of higher-order functions.
You build flexible tools. Reusable ones. Clear ones. Maintainable ones.

But there's hope

 
You don’t need to stay stuck in this.
 Try arrow functions, promises, or async/await. They flatten the pyramid. Make your code easier to read, easier to fix.
 
Or when in doubt—just call Dhoni.
 
Sometimes, the magic needs a little cleanup.

Final Over

 
Next time you're stuck, staring out the window as it rains—and your coffee's cold and your deadline's closer than ever—remember this:
 
Callbacks and higher-order functions won’t stop the storm.
But they'll help you dance in it.

They’ll make your code breathe.
They’ll make you feel like you're not fighting the machine—but flowing with it.

And when things go dark?

Just whisper the word: monadarlo.
 
It’s not just a name.
It’s a reminder.
 
That every coder has their callback moment.
 
And yours might be just around the corner.