XMLHttpRequest 异步处理Url的典型应用

<mce:script type="text/javascript" language="javascript"><!--
//申明对象实例
var xmlhttp = false;
function getHTTPRequestObject()
{
try
{
// try legacy object first
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
}
catch(e)
{
try
{
// try IE implementation now
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
catch(E)
{
xmlhttp = false;
}
}
if(!xmlhttp && typeof XMLHttpRequest!= 'undefined')
{
// we must be using a mozilla based browser
// so create a native request object now
xmlhttp = new XMLHttpRequest();
}
}
//获得一个XMLHttpRequest对象实例
getHTTPRequestObject();

if(xmlhttp)
{
//异步调用
xmlhttp.open("GET", "http://www.baidu.com", true);
xmlhttp.onreadystatechange = function()
{
if(xmlhttp.readyState == 4)
{
//引用返回结果
alert(xmlhttp.responseText);
}
}
xmlhttp.send(null);
}
// --></mce:script>