JavaScript comments are used to explain the code to make it more readable. It can be used to prevent the execution of a section of code if necessary. JavaScript comments are ignored while the compiler executes the code.
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 Geeks!" );
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Hello Geeks!
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) |
Computer science portal 13
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" );
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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(); |
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(); |
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