Inténtalo tú mismo - JavaScript Reference onseeking

<!DOCTYPE html>
<html>
<body>

In this example, we attach a "seeking" event to the video element. The currentTime property returns the current position (in seconds) of the video playback.

Move to a new position in the video.

<video id="myVideo" controls>
 <source src="mov_bbb.mp4" type="video/mp4">
 <source src="mov_bbb.ogg" type="video/ogg">
 Your browser does not support HTML5 video.
</video>

Seeked to position:

Video courtesy of <a href="../../www.bigbuckbunny.org/index.html" target="_blank">Big Buck Bunny</a>.

// Attach a seeking event to the video element, and execute a function if a seek operation begins
x.addEventListener("seeking", myFunction);

function myFunction() {
 // Display the current position of the video in a p element with id="demo"
 document.getElementById("demo").innerHTML = x.currentTime;
}
</script>

</body>
</html>