http请求

function sendGetRequest(url, callback) {
  var xhr = new XMLHttpRequest();
  xhr.open("GET", url, true);
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      var response = JSON.parse(xhr.responseText);
      callback(response);
    }
  };
  xhr.send();
}

// 调用示例
sendGetRequest("https://api.example.com/data", function(response) {
  console.log(response);
});