ajax基本實現...

    var vXMLHttp;
    function CXMLHttp() {
        if (window.ActiveXObject) {
            vXMLHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        else if (window.XMLHttpRequest) {
                    vXMLHttp = new XMLHttpRequest();
        }
    }
    function SendMessage() {
        CXMLHttp() ;        
       
        vXMLHttp.onreadystatechange=DoMessage;
       
        url="test.aspx"  ;
        vXMLHttp.open("GET",url,true);       
        vXMLHttp.send();       
    }
    function DoMessage() {
        if (vXMLHttp.readyState==4) {
                document.forms[0].elements['txtMessage'].value=vXMLHttp.responseText;
        }

    }