How can I get the html5 audio's duration time

Question

I have a html5 <audio> tag in page, but how can I know its duration time?

<audio controls="">
    <source src="p4.2.mp3">
</audio>

Answer 1

2020 solution:

You will get undefined or NaN (not a number) when the audio metadata isn't loaded yet. Therefore some people suggested to use onloadedmetadata to make sure the metadata of the audio file is fetched first. Also, what most people didn't mention is that you have to target the first index of the audio DOM element with [0] like this:

-- Vanilla Javascript:

var audio = document.getElementById('audio-1');
audio.onloadedmetadata = function() {
  alert(audio.duration);
};

If this won't work try this, however not so reliable and dependent on users connection:

setTimeout(function () {
    var audio = document.getElementById('audio-1');
    console.log("audio", audio.duration);
}, 100);

-- JQuery:

$(document).ready(function() {
   var audio = $("#audio-1")[0];
   $("#audio-1").on("loadedmetadata", function() {
       alert(audio.duration);
   }); 
});