Ajax同步与异步传输的示例代码

//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.jb51.net/;   
    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.jb51.net/";   
    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;   
    }  
}