ajax调用简单实例

<script>
function createXMLHttp()
{
  var ret = null;
  try {
    ret = new ActiveXObject('Msxml2.XMLHTTP');
  }
  catch (e) {
    try {
      ret = new ActiveXObject('Microsoft.XMLHTTP');
    }
    catch (ee) {
      ret = null;
    }
  }
  if (!ret && typeof XMLHttpRequest != 'undefined')
    ret = new XMLHttpRequest();
  return ret;
}
function loadXmlToElement(fragment_url, element_id)
{
 var element = document.getElementById(element_id);
 element.innerHTML ='<img src="loading.gif" border="0"/>数据加载中...<br/>';
 var xmlhttp = createXMLHttp();
 xmlhttp.open("GET", fragment_url);
 xmlhttp.onreadystatechange = function() 
 {
 if (xmlhttp.readyState == 4 && xmlhttp.status == 200) 
 {
  //alert(xmlhttp.responseXML.getElementsByTagName("data")[0].childNodes[0].nodeValue);
  element.innerHTML =
unescape(xmlhttp.responseXML.getElementsByTagName("data")[0].childNodes[0].nodeValue);
  if(!element.innerHTML || element.innerHTML == "/n")
  {
  try{
   element.innerHTML = unescape(xmlhttp.responseXML.firstChild.childNodes[1].nodeValue);
  }catch(e){}
  }
 }
 }
 xmlhttp.send(null); 
}
</script>
<div id="data">
</div>
<script>
 var url="t.xml";
 //alert(url);
 loadXmlToElement(url,"data");
</script>

<?xml version='1.0' encoding='utf-8' ?>
<data>
<![CDATA[ 
this is a test
]]>
</data>