回调函数实例

var xmlHttpRequest;

function fnquery(){

var cypz = '${cpcyModel.cypz}';

var ajx = 'true';

xmlHttpRequest = new XMLHttpRequest(); 

        xmlHttpRequest.onreadystatechange = callback; 

        xmlHttpRequest.open("GET", "<%=webapp%>/cpcy/cpcyAction!list.dhtml?firstFlag=clear&ajax="+ajx, true);

        xmlHttpRequest.send(null);  

}

//回调函数 

   function callback() { 

   alert(xmlHttpRequest.readyState);

       //alert(xmlHttpRequest.readyState); 

       //5。接收响应数据 

       //判断对象的状态是交互完成 

       if (xmlHttpRequest.readyState == 4) { 

           //判断http的交互是否成功 

           if (xmlHttpRequest.status == 200) { 

               //获取服务器器端返回的数据 

               //获取服务器段输出的纯文本数据 

              var responseText = xmlHttpRequest.responseText; 

               alert(responseText);

          if("true" == responseText) {

         

$("#form1").attr('action','cpcyAction!enterlist.dhtml');

$("#form1").attr('method','post');

$("#form1").submit();

}

           } else { 

               alert("出错了！！！"); 

           } 

       } 

   }