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JavaScript Comments

The comments are used to elaborate the code so that the end-user can easily understand the code.
JavaScript comments are used to add information about the code, warnings or suggestions so that the end-user can easily interpret the code.
The code written inside the comments is ignored by the JavaScript engine which is embedded in the browser.
Writing comments while coding may take time, but it maintains the international coding standards.

Advantages of JavaScript comments:

  • Comments make code easy to understand: It can be used to describe the code so the user can easily understand the code.
  • Avoids the unnecessary code: It can also be used to avoid the code being executed.
  • If you want to edit your code later, comments may help you to memorize your logic that you have written while writing that code.

Types of JavaScript Comments:

There are two types of JavaScript comments:
  • Single-line Comment
  • Multi-line Comment

Single-line Comment:

Single line comments are represented using forward slashes. (//)A single line comment can be used before and after the statement.
The following example shows a single-line comment i.e. added before the statement.

Example:

<script>
// This is single line comment
document.getElementById("demo").innerHTML = "Learn JavaScript";
</script>
Try it
The following example shows a single-line comment i.e. added after the statement.

Example:

<script>
var a = 5; // The value of variable a is 5
var b = 10; // The value of variable b is 10
// This will print value of variable b
document.getElementById("demo").innerHTML = b;
</script>
Try it

Multi-line Comment:

The multiline comment can be used to add single as well as multi-line comments, so, it is more convenient.
Multiline comments are starts with a forward slash with an asterisk(/*) and end asterisk with a forward slash(*/).
The following example shows multiline comment:

Example:

<script>
/* The code below will print
value stored in the variable b */
var a = 5;
var b = 10;
document.getElementById("demo").innerHTML = b;
</script>
Try it

Use comments to prevent JavaScript Code Execution:

If you want to add another code while working in the same code document, then you can use comments. You can comment on the previous code and add the alternative code to test it. After completion of the testing, you can uncomment the previous code. In this way, you can test both the codes using comments.

Example:

<script>
var a = 5;
//var b = 10;
document.getElementById("demo").innerHTML = b;
</script>
Try it

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