JavaScript Comments
JavaScript comments help explain code, making it easier to understand. You can also use them to temporarily disable parts of your code. The JavaScript compiler ignores comments when running the code.
1. Single Line Comments
A single-line comment in JavaScript is denoted by two forward slashes (//),
Syntax:
// your comment here
Example 1: This example illustrates the single-line comment.
// A single line comment
console.log("Hello Beginner!");
Output
Hello Beginner!
Example 2: In this example, we will assign values to some variables and explain them with single-line comments.
// Declaring a variable and assign value to it
let geek = 'Computer science portal';
console.log(geek)
// Perform operation of addition of two numbers
let sum = 5 + 8
console.log(sum)
Output
Computer science portal 13
2. Multi-line Comments
A multiline comment in JavaScript is a way to include comments that span multiple lines in the source code.
Syntax:
/*
This is a multiline comment
It can span multiple lines
*/
Example: This example illustrates the multi-line comment using /* … */
/* It is multi line comment.
It will not be displayed upon
execution of this code */
console.log("Multiline comment in javascript");
Output
Multiline comment in javascript
JavaScript Comments to Prevent Execution
We can use // or /*…*/ to change the JavaScript code execution using comments. JavaScript Comments are used to prevent code execution and are considered suitable for testing the code.
Example 1: JavaScript comments are used to prevent execution of selected code to locate problems of code or while testing new features. This example illustrates that commented code will never execute.
function add() {
let x = 10;
let y = 20;
let z = x + y;
// console.log(x + y);
console.log(z);
}
add();
Output
30
Example 2: This example uses multi-line comments to prevent the execution of addition code and perform subtraction operations.
function sub() {
let x = 10;
let y = 20;
/* let z = x + y;
console.log(z); */
let z = x - y;
console.log(z);
}
sub();
Output
-10
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