Dapatkan JavaScript header otorisasi di halaman saya

<!DOCTYPE html>
<html>
<head>
</head>
<body>
<button onclick="tryit();">PDF</button>
<script>
    function tryit() {
        var win = window.open('_blank');
        downloadFile('/pdf', function(blob) {
            var url = URL.createObjectURL(blob);
            win.location = url;
        });
    }
    function downloadFile(url, success) {
        var xhr = new XMLHttpRequest();
        xhr.open('GET', url, true);
        xhr.setRequestHeader("Authorization", "Basic " + btoa("username:password"));
        xhr.responseType = "blob";
        xhr.onreadystatechange = function() {
            if (xhr.readyState == 4) {
                if (success) success(xhr.response);
            }
        };
        xhr.send(null);
    }

</script>
</body>
</html>
Xenophobic Xenomorph