ajaxÎÊÌâ

ÎÒÔÚ¿Í»§¶ËдÁËÒ»¶ÎjavascriptHTML code:
<script type="text/javascript">
var xmlHttp;
function checkName()
{
createXMLHTTP();
var username = document.getElementById("txt_UserName");
var url = "time.aspx?username="+username.value;
xmlHttp.open("GET",url,true);
xmlHttp.onreadystatechange = checkUserName;
xmlHttp.send(null);
}
function createXMLHTTP()
{
if(window.XMLHttpRequest)
{
xmlHttp=new XMLHttpRequest();//mozillaä¯ÀÀÆ÷
}
else if(window.ActiveXObject)
{
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");//IEÀÏ°æ±¾
}
catch(e)
{}
try
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");//IEа汾
}
catch(e)
{}
if(!xmlHttp)
{
window.alert("²»ÄÜ´´½¨XMLHttpRequest¶ÔÏóʵÀý£¡");
return false;
}
}
}
function checkUserName()
{
if(xmlHttp.readyState==4)
{
if(xmlHttp.status==200)
{
if(xmlHttp.responseText=="true")