最简单的Ajax

 

<script type="text/javascript">
var xmlHttp;

function createXMLHttpRequest()
{
    if(windows.ActiveXObject)
    {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    else if(windows.XMLHttpRequest)
    {
        xmlHttp = new XMLHttpRequest();
    }
}

function startRequest()
{
    createXMLHttpRequest();
    xmlHttp.onreadystatechange=handleStateChange;
    xmlHttp.open("GET","xxx.html",true);
    xmlHttp.send(null);
}

function hadnleStateChange()
{
    if(xmlHttp.readyState==4)
    {
        if(xmlHttp.status==200)
        {
            //doSomething;
        }
    }
}
</script>