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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