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Comments | Basic Concepts
Introduction to JavaScript
course content

Course Content

Introduction to JavaScript

Introduction to JavaScript

1. Basic Concepts
2. Variables and Data Types
3. Basic Operations
4. Conditional Statements
5. Loops
6. Functions

bookComments

Sometimes, you may need to prevent a specific part of your code from executing. Deleting the entire code isn't convenient if you want to test a separate section later. There are various scenarios where you may need to temporarily halt the execution of a non-working part of your code. In such cases, comments come to your rescue.

Note

Comments provide a syntax for hiding sections of your code from the interpreter or compiler. They are also valuable for documenting code for other developers.

Single-line Comments

Single-line comments block the entire line of code, ensuring that the code above and below them is executed. The syntax for single-line comments is straightforward: you need to add // before the code on the line you wish to comment out:

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console.log("Line 1"); // console.log("Line 2"); console.log("Line 3");
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The example above shows that the comment // blocks the second code line, which is not executed.

We can also use single-line comments to block multiple lines of code in a row:

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console.log("Line 1"); console.log("Line 2"); // console.log("Line 3"); // console.log("Line 4"); console.log("Line 5");
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Also, we can add the comment at the end of the line.

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console.log("Part 1.1"); console.log("Part 1.2"); console.log("Part 2.1"); // console.log("Part 2.2") console.log("Part 3.1"); console.log("Part 3.2");
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Multi-line Comments

Consider a situation with a large code block, 299 lines long. Commenting each line individually would be time-consuming. That's where multi-line comments come in handy.

Multi-line comments start with /* and end with */. Any code enclosed within them is commented out:

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console.log("Line 1"); console.log("Line 2"); /* console.log("Line 4"); console.log("Line 5"); console.log("Line 6"); console.log("Line 7"); console.log("Line 8"); console.log("Line 9"); */ console.log("Line 11");
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In the example above, we can see that code line from 3 to 10 hasn't been executed.

We can use multi-line comments to comment a part of the line:

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console.log("Part 1", /* "Part 2", */ "Part 3");
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/* console.log("Part 1"); */ console.log("Part 2");
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1. Why are comments used in code?
2. How do we create a single-line comment?
3. What is the syntax for creating a multi-line comment?
4. If you have a large code block and enclose it within `/*` and `*/`, what happens to the enclosed code?
Why are comments used in code?

Why are comments used in code?

Select the correct answer

How do we create a single-line comment?

How do we create a single-line comment?

Select the correct answer

What is the syntax for creating a multi-line comment?

What is the syntax for creating a multi-line comment?

Select the correct answer

If you have a large code block and enclose it within `/*` and `*/`, what happens to the enclosed code?

If you have a large code block and enclose it within /* and */, what happens to the enclosed code?

Select the correct answer

Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 1. Chapter 4
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