ajax 异步获取数据实现代码 (js创建ajax对象)

复制代码 代码如下:

  <script type="text/javascript"><!--

  var request = false;

  try {

  request = new XMLHttpRequest();

  } catch (trymicrosoft) {

  try {

  request = new ActiveXObject("Msxml2.XMLHTTP");

  } catch (othermicrosoft) {

  try {

  request = new ActiveXObject("Microsoft.XMLHTTP");

  } catch (failed) {

  request = false;

  }

  }

  }

  if (!request) alert("Error initializing XMLHttpRequest!");

  //获取信息

  function GetInfo() {

  var url = "test.aspx?userName=" + document.getElementById("txtName").value;

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

  request.onreadystatechange = updatePageTime;

  request.send(null);

  }

  //更新页面

  function updatePageTime() {

  if (request.readyState == 4) {

  if (request.status == 200) {

  var response = request.responseText;

  document.getElementById("txtLoginName").value = response;

  } else if (request.status == 404) {

  alert("Requested URL is not found.");

  } else if (request.status == 403) {

  alert("Access denied.");

  } else

  alert("status is " + request.status);

  }

  }

  // --></script>

  <form id="form1" runat="server">

  <input id="txtName" onchange="GetInfo()" type="text" />

  <input id="txtLoginName" type="text" />

  </form>