Ajax开发相关问题

1、关于XMLHttpRequest对象的建立（IE7上试验成功）。2008-3-21
<script language="JavaScript" type="text/JavaScript">

var xmlhttp_request = false;
try
{
if (window.ActiveXObject)
{
for( var i = 20; i >= 0; i-- ) //如果是IE浏览器，则将XMLHttpRequest控件按版本从大到小生成。
{
try
{
if( i == 2 )
{
xmlhttp_request = new ActiveXObject( "Microsoft.XMLHTTP" );
}
else
{
xmlhttp_request = new ActiveXObject( "Msxml2.XMLHTTP." + i + ".0" );
}
// xmlhttp_request.setRequestHeader("Content-Type","text/xml");//这两句加上就出错了
// xmlhttp_request.setRequestHeader("Content-Type","gb2312");
break;
}
catch(e)
{
xmlhttp_request = false;
}
}
}
else if (window.XMLHttpRequest)
{
xmlhttp_request = new XMLHttpRequest();
if (xmlhttp_request.overrideMimeType)
{
xmlhttp_request.overrideMimeType('text/xml');
}
}
}
catch(e)
{
xmlhttp_request = false;
}

if (!xmlhttp_request){
alert("error initializing XMLHttpRequest!");
}

function getInfo(){
alert("getInfo runing!");
var phone = document.getElementById("phone").value;
alert("xmlRequest is:" + xmlhttp_request );
var url = "/StrutsSpring/index.jsp";
xmlhttp_request.open("GET", url, true);
xmlhttp_request.onreadystatechange = updatePage;
xmlhttp_request.send(null);
}

function updatePage(){
if (xmlhttp_request.readystate == 4)
if (xmlhttp_request.status == 200)
alert("server is done!");
else if (xmlhttp_request.status == 404)
alert("Request URL does not exist!");
else
alert("Request error code is " + xmlhttp_request.status);
}
</script>