<!DOCTYPE html>
<html>
<body>
<script>
function myFunction() { alert('The video is now playing');
}
</script>
<p>Press play on the video.</p>
<video controls onplaying="myFunction()"> <source src="https://download.samplelib.com/mp4/sample-5s.mp4" type="video/mp4"> <source src="https://download.samplelib.com/mp4/sample-5s.mp4" type="video/ogg"> Your browser does not support HTML5 video.
</video>
<p>Video courtesy of <a href="https://www.bigbuckbunny.org/" target="_blank">Big Buck Bunny</a>.</p>
</body>
</html>