JavaScript Comments: A Guide to Commenting in JavaScript

If you are new to JavaScript programming or even an experienced developer, understanding how to comment your code effectively is crucial. Comments in JavaScript provide essential information, explanations, and context about your code. In this article, we will explore JavaScript comments, their types, and how to use them effectively. So let’s dive in and discover the world of JavaScript comments!


In JavaScript, comments are pieces of text that are ignored by the interpreter or compiler. They exist purely for human readers to understand the code better. Comments are not executed as part of the program and do not affect its functionality.

Why Are Comments Important in JavaScript?

Comments play a vital role in programming for several reasons:

  • Code Understanding: Comments help you and other developers understand the purpose and functionality of your code.
  • Code Debugging: Well-commented code is easier to debug and maintain since comments provide insights into the code’s logic.
  • Collaboration: When working on a project with a team, comments ensure seamless collaboration by clarifying code sections.
  • Documentation: Comments act as documentation for your code, making it easier for others to use and modify.

Single-Line Comments

Single-line comments in JavaScript start with two forward slashes (//). Anything written after // on the same line is considered a comment and is ignored by the JavaScript interpreter. Single-line comments are useful for adding short explanations or annotations to specific lines of code.

// This is a single-line comment
var age = 25; // Declare and assign the variable age

Multi-Line Comments

Multi-line comments, also known as block comments, start with /* and end with */. These comments can span multiple lines, allowing you to provide detailed explanations or temporarily disable sections of code.

This is a multi-line comment.
It can span multiple lines.
Useful for providing longer explanations.
var name = "John";
/* var age = 30; */ // This line is temporarily commented out

Commenting Best Practices

To ensure your comments are clear, effective, and maintainable, follow these best practices:

  1. Be Descriptive: Write comments that provide meaningful explanations, focusing on why the code does what it does rather than what it does.
  2. Avoid Obvious Comments: Don’t comment on self-explanatory code. Comments should add value and provide insights beyond the obvious.
  3. Regular Maintenance: Keep your comments up to date. As you modify code, ensure that corresponding comments reflect the changes accurately.
  4. Grammar and Formatting: Use proper grammar, punctuation, and formatting in your comments to enhance readability.
  5. Avoid Excessive Comments: Strive for a balance between providing enough information and overwhelming the code with excessive comments.

Examples of JavaScript Comments

Let’s explore some examples to see how comments can be used effectively in JavaScript.

Example 1: Commenting Variable Assignment

// Declare and initialize the variable count
var count = 0;

Example 2: Explaining Functionality

// Calculate the area of a rectangle
function calculateArea(length, width) {
  return length * width;

Example 3: Disabling Code

// Temporary code disable
alert("This line will not execute.");


JavaScript comments are essential tools for code documentation, comprehension, and collaboration. By effectively using comments in your JavaScript code, you can improve its readability, maintainability, and overall quality. Remember to be descriptive, follow best practices, and update comments as your code evolves.


How do you comment in JavaScript?

To comment in JavaScript, you can use either single-line comments (//) or multi-line comments (/* */). Single-line comments are used for short explanations, while multi-line comments are ideal for longer comments or temporarily disabling code.

What is an example of a JavaScript comment?

Here is an example of a JavaScript single-line comment:
// This is a comment in JavaScript

What are the two types of comments in JavaScript?

The two types of comments in JavaScript are single-line comments (//) and multi-line comments (/* */).

What is an inline comment in JavaScript?

In JavaScript, an inline comment refers to adding comments on the same line as the code. Inline comments are typically used to explain specific parts of a line or provide additional context.

How do we write a comment in JavaScript using /* */?

To write a multi-line comment in JavaScript, you can use the opening and closing symbols /* and */. Anything between these symbols is considered a comment.

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