一个XmlHttpRequest的小程序

    <script type="text/javascript" language=javascript>
        <!--
        function TestA()
        {
            var http_request;
            if (window.XMLHttpRequest) { // Mozilla, Safari, ...           
                http_request = new XMLHttpRequest();
            } else if (window.ActiveXObject) { // IE
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
            }
           
            http_request.onreadystatechange = function()
            {
                if(http_request.readyState==4)
                {
                    if(http_request.status==200)
                    {
                        document.write(http_request.responseText);
                    }
                    else
                    {
                        alert("error");
                    }
                }
                else
                {
                    //alert(http_request.readyState);
                }
            };
           
            //http_request.overrideMimeType("text/xml");
            http_request.open("POST","URL","true")
            //http_request.setRequestHeader("charset","Utf-8");
            http_request.send("SysTime=true")
        }
        //-->
    </script>