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
    consol.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. 

Javascript

<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>

Output:

Before clicking on the button:

After clicking on the button: