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<!DOCTYPE html>
<html>
<body>

<h3>A demonstration of how to access a AUDIO element</h3>

<audio id="myAudio" controls>
  <source src="horse.ogg" type="audio/ogg">
  <source src="horse.mp3" type="audio/mpeg">
  Your browser does not support the audio element.
</audio>

<p>Click the button to get the duration of the audio, in seconds.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.getElementById("myAudio").duration;
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>