如何在Vanilla JS中发送AJAX post请求和接收回JSON数据？

var xhr = new XMLHttpRequest();

xhr.open("POST", "请求的URL", true);

xhr.setRequestHeader("Content-Type", "application/json");

xhr.onreadystatechange = function() {
  if (xhr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
    var response = JSON.parse(xhr.responseText);
    // 处理返回的JSON数据
  }
};

var data = {
  key1: value1,
  key2: value2
};
xhr.send(JSON.stringify(data));

var xhr = new XMLHttpRequest();
xhr.open("POST", "请求的URL", true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.onreadystatechange = function() {
  if (xhr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
    var response = JSON.parse(xhr.responseText);
    // 处理返回的JSON数据
  }
};
var data = {
  key1: value1,
  key2: value2
};
xhr.send(JSON.stringify(data));