JavaScript Comments
Javascript comments explain the code design. They can also be used to prevent the execution of a section of code if necessary. Comments are ignored while the compiler executes the code. Comments are user-friendly as users can get explanations of code using comments.
Syntax:
// For single line comment
/* For block of lines comment ... ... */
Return Value: During the execution of code, comments are ignored.
Example 1: This example illustrates the single-line comment using //.
Javascript
<script> // A single line comment console.log( "Hello Geeks!" ); </script> |
Example 2: This example illustrates the multi-line comment using /* … */
Javascript
<script> /* It is multi line comment. It will not be displayed upon execution of this code */ console.log( "Multiline comment in javascript" ); </script> |
Example 3: Javascript comments can be used to prevent selective execution of code to locate problematic code or while testing new features. This example illustrates that commented code will never execute.
HTML
< body > < label >Enter the first number < input id = "num1" > </ label > < br >< br > < label >Enter the first number < input id = "num2" > </ label > < br >< br > < button onclick = "add()" > Sum </ button > < input id = 'sum' > < script > function add() { var x, y, z; x = Number( document.getElementById("num1").value ); y = Number( document.getElementById("num2").value ); z= x +y; // Comment the code section //document.getElementById("sum").value = z; } </ script > </ body > |
Output:

Explanation: The sum is calculated but not displayed because the code to display sum is written in a comment and will not be displayed
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