As a web developer, it’s crucial to write clean and understandable code. One powerful tool at your disposal is comments in JavaScript. Comments allow you to explain complex code blocks, provide context, and make your code more maintainable. In this guide, we will explore the various ways to comment in JavaScript and best practices for using comments effectively.

JavaScript Comment Types

JavaScript offers two main types of comments: single-line comments and multi-line comments.

Single-Line Comments

Single-line comments are ideal for adding quick explanations or clarifications to a specific line of code. You can create a single-line comment in JavaScript by using two forward slashes (//). Here’s an example:

// This will output 'hello world' to the browser's console.
console.log('hello world');

Single-line comments are useful for providing brief insights into the purpose of a particular line of code.

Multi-Line Comments

Sometimes, a single line is not enough to document or explain the reasoning behind a section of code. That’s when multi-line comments come in handy. Also known as block comments, multi-line comments allow you to add detailed explanations or formal documentation.

To create a multi-line comment in JavaScript, you enclose the comment between a forward-slash followed by an asterisk (/) and an asterisk followed by a forward-slash (/). Here’s an example:

Add two numbers and store the output in a variable called result.
Also, print the output to the browser’s console.
result = 6 * 5;
console.log('Multiplication result is: ', result);

Multi-line comments provide a comprehensive overview of a code block’s purpose and can be immensely helpful for yourself and other developers working on the project.

Best Practices for Using Comments

Now that you understand the different types of comments in JavaScript, let’s explore some best practices for using comments effectively:

Be concise and clear: Write comments that are easy to understand and provide relevant information about the code’s functionality.

Avoid redundant comments: Don’t state the obvious. Focus on explaining complex logic, algorithms, or unusual code.

Update comments: Keep comments up-to-date when modifying code to ensure they accurately reflect the code’s current functionality.

Use proper grammar and formatting: Maintain consistency in your comments by following proper grammar and formatting guidelines.

Don’t leave commented-out code: Remove any commented-out code that is no longer needed. It can clutter the codebase and create confusion.

Collaborate with your team: Discuss commenting conventions and standards with your team to ensure consistency across the project.


In JavaScript, comments play a crucial role in making your code more readable, understandable, and maintainable. By using single-line and multi-line comments effectively, you can provide valuable insights into your code’s logic and facilitate collaboration among developers.

Remember to be concise, clear, and consistent with your comments. Use them to explain complex code blocks, provide context, and document your thought process. With well-placed comments, you can enhance the readability and maintainability of your JavaScript codebase.


What is the purpose of commenting in JavaScript?

The purpose of commenting in JavaScript is to provide explanations, clarifications, and context about the code. Comments help developers understand the code’s functionality, make it more maintainable, and assist in collaboration among team members.

Can comments in JavaScript affect the code’s execution?

No, comments in JavaScript do not affect the code’s execution. They are ignored by the JavaScript interpreter and are solely meant for human readability. Comments are not considered executable code.

Are comments visible in the final JavaScript output?

No, comments are not visible in the final JavaScript output. When you run or deploy JavaScript code, the comments are stripped out during the minification or compilation process. The resulting JavaScript output does not contain any comments.

Is there a character limit for JavaScript comments?

JavaScript does not have a specific character limit for comments. You can write comments of any length, but it’s recommended to keep them concise and focused on providing relevant information. Long comments can be difficult to read and maintain, so it’s best to break them down into smaller, more manageable chunks.

Can I use comments to document my JavaScript code?

Yes, comments are commonly used to document JavaScript code. By providing explanations and documenting the purpose, behavior, and usage of functions, classes, and variables, comments serve as a form of documentation. However, for more extensive and structured documentation, you may consider using dedicated documentation tools or formats, such as JSDoc, which allows you to generate API documentation from code comments.

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