convert base64 string into byte array and save in mp3 file format

function saveBase64AsAudioFile(folderpath,filename,content,contentType){
    // Convert the base64 string in a Blob
    var DataBlob = b64toBlob(content,contentType);

    console.log("Starting to write the file :3");

    window.resolveLocalFileSystemURL(folderpath, function(dir) {
        console.log("Access to the directory granted succesfully");
        dir.getFile(filename, {create:true}, function(file) {
            console.log("File created succesfully.");
            file.createWriter(function(fileWriter) {
                console.log("Writing content to file");
                fileWriter.write(DataBlob);
            }, function(){
                alert('Unable to save file in path '+ folderpath);
            });
        });
    });
}