XMLHttpRequest ajax调用无刷新显示后台时间

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>无标题页</title>
</head>

代码
   < script type = " text/javascript "   >
    
var  timeout  =   null // setInterval函数句柄   
     var  xmlHttp  =   false //  
     function  SendRequest()
    {
        
// xmlHttp = false; 
         if  (window.ActiveXObject)
        {   
            
try  
            {
                xmlHttp 
=   new  ActiveXObject( " Msxml2.XMLHTTP " );
            }    
            
catch  (e) 
            {
                xmlHttp 
=   new  ActiveXObject( " Microsoft.XMLHTTP " );
            }   
        }
        
else   if  (window.XMLHttpRequest) 
        {
            xmlHttp 
=   new  XMLHttpRequest();
        } 
        
else
        {
            alert(
' 初始化错误! ' );
            
return ;
        }
        
var  url  =   " Handler.ashx " ;
        
// var url = "Default2.aspx";
        xmlHttp.open( " GET " ,url, true );
        xmlHttp.onreadystatechange 
=  ShowData;
        xmlHttp.send(
null );
    }
    
function  ShowData()
    {
        
if (xmlHttp.readystate  ==   4 )
        {
            
if (xmlHttp.status  ==   200 )
            {
                
var  tag  =  document.getElementById( " container " );
                tag.innerHTML 
=   "" ;
                tag.innerHTML 
=  xmlHttp.responseText;
            }  
        }
    }

    
// 开始自动刷新   
     function  Update() 
    {   
        timeout 
=  window.setInterval( " SendRequest() " 1000 ); // 设定1秒调用一次Default2.aspx页面   
    }   
    
// 停止自动刷新   
     function  StopUpdate() 
    {   
        
if  (timeout  !=   null
        {   
            window.clearInterval(timeout);   
        }   
    }
< / script>

 

<body onload="SendRequest();">
    <form id="form1" runat="server">
    <div>
        <input type="button" value="Start Fresh" onclick="Update();"/> 
        <input type="button" value="Stop Fresh" onclick="StopUpdate();"/>
        <input id="Button1" type="button" value="确定" onclick="SendRequest();"/>
    </div>
    </form>
    <div id="container"><!--容器--></div>
</body>
</html>

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