JavaScript Comments: Explaining and Organizing Your Code

(Code Speaks… But Humans Need Subtitles)

One day you open an old project.
You stare at the screen.
The code stares back at you.

A silent tension fills the room.

“Did I really write this?”

That’s the exact moment you understand the value of comments.

JavaScript comments may look small, but they prevent big disasters.
When used correctly, they strengthen team communication.
When used poorly, they turn into a code graveyard.

Today, we won’t treat comments as just “// writing explanations.”
We’ll treat them as a strategic weapon of clean code.

Ready? Let’s begin.

1️⃣ Single-Line Comments (//)

(Whispers in the Margin of Your Code)

Single-line comments are fast, practical, and perfect for quick thoughts.

// User's birth year
const birthYear = 1998;

Simple. But here’s the real point:

Single-line comments usually provide context.

🎯 When Should You Use Them?

To explain the business logic behind a line
For small warnings
To temporarily disable code while debugging

⚠️ Using Comments for Debugging

const price = 100;
const discount = 20;

// const total = price - discount;
const total = price;

console.log(total);

Here, the discount is temporarily disabled.

But be careful:
If temporary becomes permanent, your project turns into a mess.

👉 Pro tip:
Delete temporary commented-out code once you’re done.

2️⃣ Multi-Line Comments (/* */)

(A Mini Documentary Inside Your Code)

Multi-line comments are used for more detailed explanations.

/*
  This function:
  - Cleans raw user input
  - Removes unnecessary spaces
  - Converts text to uppercase
*/
function normalizeInput(input) {
  return input.trim().toUpperCase();
}

The code here is short.
But in real projects, things get complicated.

🎯 Real-Life Example

/*
  Date format received from the API:
  "2026-02-13T08:15:30Z"

  This function:
  1. Converts the string into a Date object
  2. Adjusts it to local time zone
  3. Returns a UI-friendly readable string
*/
function formatDate(apiDate) {
  const date = new Date(apiDate);
  return date.toLocaleString();
}

This comment tells future developers:

“There’s logic here. This wasn’t written randomly.”

3️⃣ Why Do We Write Comments? (The Philosophy)

Code shows what it does.
Comments explain why it does it.

❌ Bad Example

// Multiply the number by 2
const result = number * 2;

Unnecessary.

✅ Good Example

// API returns decimal instead of percentage, so we multiply by 100
const percentage = apiValue * 100;

Now we have context.
We have reasoning.
We answer the question:
“Why did we do something that looks strange?”

4️⃣ Comments Save Lives in Complex Logic

In real projects, some lines of code…
test your sanity.

const finalPrice =
  user.isPremium &amp;&amp; cart.total > 500
    ? cart.total * 0.8
    : cart.total;

This single line contains drama.

Let’s clarify it:

// If the user is premium and cart total is above 500, apply 20% discount
const finalPrice =
  user.isPremium &amp;&amp; cart.total > 500
    ? cart.total * 0.8
    : cart.total;

Now it’s human-friendly.

5️⃣ JSDoc: Professional-Level Commenting

In large projects, comments are not just explanations.
They are documentation.

/**
 * Adds two numbers
 * @param {number} a - First number
 * @param {number} b - Second number
 * @returns {number} The total result
 */
function sum(a, b) {
  return a + b;
}

Why Is It Important?

IDEs provide smart suggestions
Type checking becomes easier
Huge advantage in team projects

If you’re not using TypeScript, JSDoc is gold.

6️⃣ TODO, FIXME, and Technical Debt

In real life, no project is “perfect.”

// TODO: Make this function async
// FIXME: API throws error when returning null
// HACK: Temporary workaround solution

These labels:

Improve team communication
Make technical debt visible
Bring order to chaos

But remember:
TODOs shouldn’t live forever.

7️⃣ Too Many Comments Are Harmful

Now the critical part.

// Declare variable
let count = 0;

// Increase by 1
count++;

// Print to console
console.log(count);

This looks like a beginner tutorial.

In real projects, unnecessary.

Instead, write clearer code:

let loginAttemptCount = 0;
loginAttemptCount++;
console.log(loginAttemptCount);

If naming is good, comments become less necessary.

8️⃣ Should I Comment or Simplify the Code?

Ask yourself:

“Does this code need a comment to be understood?”

If yes…

Maybe the code should be simplified instead.

Example:

// Block access if user is active but not admin
if (user.isActive === true &amp;&amp; user.role !== "admin") {

Rewrite it more clearly:

const isRestrictedUser =
  user.isActive &amp;&amp; user.role !== "admin";

if (isRestrictedUser) {

Now we need fewer comments.

9️⃣ The Biggest Truth

Comments are:

Letters to your future self.
Guides for your teammates.
Maps of complex business logic.

But:

Bad code cannot be saved by comments.
Comments cannot replace clean structure.
Unnecessary comments pollute your code.

🎬 Conclusion

Code is for computers.
Comments are for humans.

And the most dangerous sentence in software development is:

“I’ll remember this.”

No.
You won’t.

Write comments.
But write them intentionally.
Be concise.
Explain the reason.
Give context.

Because six months later…

Your best friend in that project
will be the comment you wrote.