JavaScript | Comments - GeeksforGeeks

26 Oct, 2021
Comments are used to prevent the execution of statements. 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 execution of code, comments are ignored.
Example 1: This example illustrates the single line comment using //.
html
<!DOCTYPE html><html>  <head>    <title>        JavaScript Comments    </title>          <script>                  // Function to add two numbers        function add() {                          // Declare three variables            var x, y, z;                          // Input a number and store it into variable x            x = Number( document.getElementById("num1").value );                          // Input a number and store it into variable x            y = Number( document.getElementById("num2").value );                          // Sum of two numbers            z= x +y;                          // Return the sum            document.getElementById("sum").value = z;        }    </script></head>  <body>    Enter the First number: <input id="num1"><br><br>    Enter the Second number: <input id="num2"><br><br>          <button onclick="add()">        Sum    </button>          <input id="sum"></body>  </html>                    
Example 2: This example illustrates the multi-line comment using /* ... */
html
<!DOCTYPE html><html>  <head>    <title>        JavaScript Comments    </title>          <script>              /* Script to get two input from user        and add them */        function add() {                          /* Declare three variable */            var x, y, z;                          /* Input the two nos. num1, num2            Input num1 and store it in x            Input num2 and store it in y            The sum is stored in a variable z*/            x = Number(document.getElementById("num1").value);             y = Number(document.getElementById("num2").value);            z = x + y;                          document.getElementById("sum").value = z;        }    </script></head>  <body>    Enter the First number : <input id="num1"><br><br>    Enter the Second number: <input id="num2"><br><br>          <button onclick="add()">        Sum    </button>          <input id="sum"></body>  </html>                    
Example 3: This example illustrates that commented code will never execute.
html
<!DOCTYPE html><html>  <head>    <title>        JavaScript Comments    </title>          <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></head>  <body>    Enter the First number: <input id="num1"><br><br>    Enter the Second number: <input id="num2"><br><br>          <button onclick="add()">        Sum    </button>          <input id="sum"></body>  </html>                    
shrijitpandey
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