不使用jQuery的并行AJAX请求

function sendRequest(url, method, callback) {
  var xhr = new XMLHttpRequest();
  xhr.open(method, url, true);
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      callback(xhr.responseText);
    }
  };
  xhr.send();
}

function parallelRequests(urls, callback) {
  var count = urls.length;
  var responses = [];

  function handleResponse(index, response) {
    responses[index] = response;
    count--;

    if (count === 0) {
      callback(responses);
    }
  }

  for (var i = 0; i < urls.length; i++) {
    sendRequest(urls[i], 'GET', handleResponse.bind(null, i));
  }
}

var urls = ['url1', 'url2', 'url3']; // 替换为实际的请求URL
parallelRequests(urls, function(responses) {
  // 处理并行请求的响应数据
  console.log(responses);
});