通过XMLHTTP进行一次指定的HEAD请求：
html
head
script type="text/javascript"
var xmlhttp;
function loadXMLDoc(url)
{
xmlhttp=null;
if (window.XMLHttpRequest)
{// all modern browsers
xmlhttp=new XMLHttpRequest();
}
else if (window.ActiveXObject)
{// for IE5, IE6
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
if (xmlhttp!=null)
{
xmlhttp.onreadystatechange=state_Change;
xmlhttp.open("GET",url,true);
xmlhttp.send(null);
}
else
{
alert("Your browser does not support XMLHTTP.");
}
}
function state_Change()
{
if (xmlhttp.readyState==4)
{// 4 = "loaded"
if (xmlhttp.status==200)
{// 200 = "OK"
document.getElementById('p1').innerHTML="This file was last modified on: " + xmlhttp.getResponseHeader('Last-Modified');
}
else
{
alert("Problem retrieving data:" + xmlhttp.statusText);
}
}
}
/script
/head
body
p id="p1"
The getResponseHeader() function returns a header from a resource.
Headers contain file information like length,
server-type, content-type, date-modified, etc./p
button onclick="loadXMLDoc('/example/ajax/test_xmlhttp.txt')"Get "Last-Modified"/button
/body
/html
