<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="mov_bbb.mp4" type="video/mp4">
<source src="mov_bbb.ogg" 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>