The ondurationchange attribute triggers when the length of the audio/ video changes in HTML.
Example
You can try to run the following code to implement ondurationchange attribute −
<!DOCTYPE HTML>
<html>
<body>
<video width = "300" height = "200" controls ondurationchange = "display(this)">
<source src = "/html5/foo.ogg" type = "video/ogg" />
<source src = "/html5/foo.mp4" type = "video/mp4" />
Your browser does not support the video element.
</video>
<script>
function display(vLength) {
alert("Video Length: " + vLength.duration + " seconds");
}
</script>
</body>
</html>