Ajax同步和异步传输

//同步传输模式

function RequestByGet(nProducttemp,nCountrytemp)
{
    var xmlhttp

    if (window.XMLHttpRequest)  
    {  
         //isIE   =   false;  
         xmlhttp   =   new   XMLHttpRequest();  
    }  
    else if (window.ActiveXObject)
    {  
         //isIE   =   true;  
         xmlhttp   =   new   ActiveXObject("Microsoft.XMLHTTP");  
    }
                 
    //Web page location.
    var URL="http://www.baidu.com/;
    xmlhttp.open("GET",URL, false);
    //xmlhttp.SetRequestHeader("Content-Type","text/html; charset=Shift_JIS")
    xmlhttp.send(null);
    var result = xmlhttp.status;
   
    //OK
    if(result==200)
    {
        document.getElementById("div_RightBarBody").innerHTML=xmlhttp.responseText;
    }
    xmlhttp = null;
}


//异步传输模式
var xmlhttp

function RequestByGet(nProducttemp,nCountrytemp)
{
    if (window.XMLHttpRequest)  
    {  
         //isIE   =   false;  
         xmlhttp   =   new   XMLHttpRequest();  
    }  
    else if (window.ActiveXObject)
    {  
         //isIE   =   true;  
         xmlhttp   =   new   ActiveXObject("Microsoft.XMLHTTP");  
    }
                 
    //Web page location.
    var URL="http://www.baidu.com/";
    xmlhttp.open("GET",URL, true);
    xmlhttp.onreadystatechange = handleResponse;
    //xmlhttp.SetRequestHeader("Content-Type","text/html; charset=UTF-8")
    xmlhttp.send(null);  
}

function handleResponse()
{
    if(xmlhttp.readyState == 4 && xmlhttp.status==200)
    {
        document.getElementById("div_RightBarBody").innerHTML=xmlhttp.responseText;
        xmlhttp = null;
    }
}