JSFiddle - React, Tailwind, and code Playground

HTML

<div id="root"></div>

React

class ConverterSec2 extends React.Component {

    uploadFile = ({ target: { files } }) => {
        console.log(files[0])
        let data = new FormData()
        data.append('file', files[0])
    }

    convertFile () {
        var fileInput = document.getElementById('audio-file')
        var ctx = new AudioContext()
        var convertFiles = document.getElementById('convert_button')
        
        //load audio file listener
            if (fileInput.files[0] == undefined) {
                console.log("no file found")
                return false
            }
            
            var soundSource = ctx.createBufferSource();
            var reader1 = new FileReader()
            reader1.onload = function(ev) {
                ctx.decodeAudioData(ev.target.result).then(function(buffer){
                    soundSource.buffer = buffer

                    // create the stretch
                    soundSource.playbackRate.linearRampToValueAtTime(0.0185, ctx.currentTime)
                    //connect source
                    soundSource.connect(ctx.destination)
                    // convert pitch
                    var pitchChange = ctx.createBiquadFilter()
                    pitchChange.type = 'highpass'
                    pitchChange.frequency.value = 432
                    pitchChange.connect(ctx.destination)
                })

            }
            
            reader1.readAsArrayBuffer(fileInput.files[0]);
    }

    downloadFile() {
        let fileInput = document.getElementById('audio-file')
        let file = fileInput.files[0]
        let url = URL.createObjectURL(file)

        let link = document.createElement('a')
        link.href = url
        link.download =  file.name
        link.click()
        link = null

        URL.revokeObjectURL(url)
    }

    render() {
        
        return (
            <div className="sec2">
                    <input type="file" id="audio-file" accept="audio/mpeg, audio/ogg, audio/*" name="file"...