JavaScript | Comments
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> |
Output:
Before clicking on the button:
After clicking on the button:
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> |
Output:
Before clicking on the button:
After clicking on the button:
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> |
Output:
Before clicking on the button:
After clicking on the button:
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