delete all existing HTML
delete all existing HTML : by this method we can clarify that our JavaScript code is wrong or right by opening it on web page and its delete all existing html. <!DOCTYPE html> <html> <body> <button onclick="document.write(15 + 6)"> click me</button> <p> click on button and you will see the result of (15+6) </p> </body> </html> demo here https://jsfiddle.net/4opd5qw2/1/