JSFiddle - React, Tailwind, and code Playground

HTML

<input type="file" id="fileInput">
                <div> duration: <span id='sp'></span>
                    <div>

JavaScript

var fileInput = document.getElementById('fileInput');
var sp = document.getElementById('sp');
fileInput.onchange  = function(){
    var file = fileInput.files[0];
    var reader = new FileReader();
    reader.onload = function() {
        var aud = new Audio(reader.result);
        aud.onloadedmetadata = function(){
            sp.innerHTML = aud.duration;
        };    
    };
    reader.readAsDataURL(file);	
};