如何向URL发出Ajax请求，并在url后面附加查询字符串，以便运行url程序

var xhr = new XMLHttpRequest();

var url = "http://example.com/api";
var params = "param1=" + encodeURIComponent(value1) + "&param2=" + encodeURIComponent(value2);
url = url + "?" + params;

xhr.open("GET", url, true);

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

xhr.send(null);

xhr.onreadystatechange = function() {
  if (xhr.readyState === 4 && xhr.status === 200) {
    var response = xhr.responseText;
    // 处理服务器返回的数据
  }
};

var xhr = new XMLHttpRequest();
var url = "http://example.com/api";
var params = "param1=" + encodeURIComponent(value1) + "&param2=" + encodeURIComponent(value2);
url = url + "?" + params;

xhr.open("GET", url, true);
xhr.setRequestHeader("Content-Type", "application/json");

xhr.onreadystatechange = function() {
  if (xhr.readyState === 4 && xhr.status === 200) {
    var response = xhr.responseText;
    // 处理服务器返回的数据
  }
};

xhr.send(null);