Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <body> <p>Click the button to wait 3 seconds, then alert "Hello".</p> <p>After clicking away the alert box, an new alert box will appear in 3 seconds. This goes on forever...</p> <button onclick="myFunction()">Try it</button> <script> function myFunction() { setInterval(function(){alert("Hello")},3000); } </script> </body> </html>
Result:
W3Schools.com - Try it yourself