Не могу получить ответ XMLHttpRequest

function SendData(){
var a = "1";
var b = "2";
let formData = new FormData();
formData.append("FirstParameter", a);
formData.append("SecondParameter", b);
let xhr = new XMLHttpRequest();
xhr.open("POST", "https://mysite.ru", true);
xhr.send(formData);
xhr.onload = function() {
alert(xhr.response);
};
};

function SendData(){
var a = "1";
var b = "2";
let formData = new FormData();
formData.append("FirstParameter", a);
formData.append("SecondParameter", b);
let response = await fetch('https://mysite.ru', {
  method: 'POST',
  body: formData
});
 
let result = await response.json();
alert(result.message);
};

function SendData(){
var a = "1";
var b = "2";
let formData = new FormData();
formData.append("FirstParameter", a);
formData.append("SecondParameter", b);
let xhr = new XMLHttpRequest();
xhr.open("POST", "https://mysite.ru", true);
xhr.send(formData);
xhr.onreadystatechange = function() { // (3)
  if (xhr.readyState != 4) return;
 
  alert('Готово!');
 
  if (xhr.status != 200) {
    alert(xhr.status + ': ' + xhr.statusText);
  } else {
    alert(xhr.responseText);
  }
 
}
};

xhr.open("POST", "https://mysite.ru", true);
xhr.send(formData);
xhr.onreadystatechange = function() { // (3)
  if (xhr.readyState != 4) return;
 
  alert('Готово!');
 
  if (xhr.status != 200) {
    alert(xhr.status + ': ' + xhr.statusText);
  } else {
    alert(xhr.responseText);
  }
 
}