<script>
    var data = new FormData();
    data.append("username", "test");

    var xhr = new XMLHttpRequest();
    xhr.withCredentials = true;

    xhr.addEventListener("readystatechange", function() {
    if(this.readyState === 4) {
        console.log(this.responseText);
    }
    });

    xhr.open("POST", "https://test.miaodrew.workers.dev/");

    xhr.send(data);
</script>