converting audio file to base64 using javascript

you can give the below code a try, it uses btoa

function getData(audioFile, callback) {
    var reader = new FileReader();
    reader.onload = function(event) {
        var data = event.target.result.split(',')
         , decodedImageData = btoa(data[1]);                    // the actual conversion of data from binary to base64 format
        callback(decodedImageData);        
    };
    reader.readAsDataURL(audioFile);
}