ajax 不错的应用

  <script type="text/javascript" language="javascript">

      var http_request = false;

      function makeRequest(url) {

          http_request = false;

          if (window.XMLHttpRequest) { // Mozilla, Safari,...

  http_request = new XMLHttpRequest();

  if (http_request.overrideMimeType) {

  http_request.overrideMimeType('text/xml');

  }

  } else if (window.ActiveXObject) { // IE

  try {

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

  } catch (e) {

  try {

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

  } catch (e) {}

  }

  }

          if (!http_request) {

  alert('Giving up :( Cannot create an XMLHTTP instance');

  return false;

  }

  http_request.onreadystatechange = alertContents;

  http_request.open('GET', url, true);

  http_request.send(null);

      }

      function alertContents() {

          if (http_request.readyState == 4) {

  if (http_request.status == 200) {

  alert(http_request.responseText);

  } else {

  alert('There was a problem with the request.');

  }

  }

      }

  </script>

  <span

  style="cursor: pointer; text-decoration: underline"

  onclick="makeRequest('test.html')">

  Make a request

  </span>

  

   [Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]