实用JS小汇总--实现异步获取数据

 1 < script type = " text/javascript "  src = " jquery.js " ></ script >
 2 < script type = " text/javascript "  language = " javascript " >
 3  xmlhttp  =   false ;
 4  var requestURL  =   " Chatcontent.aspx " ;
 5 function getNames() 
 6 {          
 7        var url = requestURL;
 8        getHTTPRequestObject();
 9        if(xmlhttp)
10        {
11            xmlhttp.open("POST", url, true);
12            xmlhttp.onreadystatechange = callback; 
13            xmlhttp.send(null);
14        } 
15}
16
17 function callback(response)
18 {
19        if(xmlhttp.readyState == 4) 
20        {
21            if(xmlhttp.status ==200)
22            {
23              eval("var objResults = " + xmlhttp.responseText);
24              
25                
26              var displaytext = "";
27              
28              for (var i=0; i < objResults.Results.shops.length; i++)
29              {
30                displaytext += objResults.Results.shops[i].Name + "<br />"; 
31              }
32              if(displaytext.length > 0)
33              {
34                  var findDIV = document.getElementById("chatcontent");
35                  findDIV.className = 'show';
36                  findDIV.innerHTML = displaytext;                    
37              }
38                   
39            }
40        }
41}
42
43 function getHTTPRequestObject()
44 {
45    try
46    {
47        // 首先尝试以前的遗留对象
48        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
49    }
50    catch(e)
51    {
52        try
53        {
54            // IE对象
55            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
56        }
57        catch(E)
58        {
59            xmlhttp = false;
60        }
61    }
62    if(!xmlhttp && typeof XMLHttpRequest!= 'undefined')
63    {
64        //其它对象，如Mozilla
65        xmlhttp = new XMLHttpRequest();
66    }
67}
68 function begin() 
69 {
70    setInterval("getNames()", 1000);
71}
72
73 </ script >

获取ChatContent.aspx页面Reponse出来的值

 1  DataTable dtReturn  =   new  DataTable();
 2              string  currentusername  =   " test03 " ; // SPContext.Current.Web.CurrentUser.Name;
 3             SqlConnection conn  =   new  SqlConnection( " Data Source=.;DataBase=oaApplication;Integrated Security=true " );
 4              string  DeptName  =   "" ;
 5              string  strwhere  =   "" ;
 6   strwhere  =   " (Ispublic='YES'and timenow>=' "   +  DateTime.Now.ToShortDateString()  +   " ')or (Ispublic='NO' and (user_to=' "   +  currentusername  +   " ' or user_from=' "   +  currentusername  +   " ') and timenow>=' "   +  DateTime.Now.ToShortDateString()  +   " ') or(Ispublic='NO' and user_to=' "   +  DeptName  +   " 'and timenow>=' "   +  DateTime.Now.ToShortDateString()  +   " ') order by ID desc " ;
 7             conn.Open();
 8             SqlCommand cmd  =   new  SqlCommand( @" select top 10 ID,user_from,user_to,chatcontent,timenow,Ispublic from dbo.ChatRoom where  " + strwhere + "" , conn);
 9             SqlParameter param  =   new  SqlParameter();
10             SqlDataAdapter adpt  =   new  SqlDataAdapter(cmd);
11             adpt.Fill(dtReturn);
12             conn.Close();
13              // 构建JSON.
14              // dtReturn = BLL_ChatRoom.GetTenRecored(strwhere).Tables[0];
15             StringBuilder sb  =   new  StringBuilder();
16             sb.Append( " {\ " Results\ " : { \ " shops\ " : [ " );
17              for  ( int  i  =   0 ; i  <  dtReturn.Rows.Count; i ++ )
18              {
19                sb.Append("{\"Name\":\"" + Convert.ToDateTime(dtReturn.Rows[i]["timenow"]) + "  " + (string)dtReturn.Rows[i]["user_from"] + "对" + (string)dtReturn.Rows[i]["user_to"] + " 说道<br/> " + (string)dtReturn.Rows[i]["chatcontent"] + "  " + "\"}");
20                if (i <= (dtReturn.Rows.Count - 2))
21                {
22                    sb.Append(",");
23                }
24            }
25
26             sb.Append( " ]}} " );
27             Response.Write(sb.ToString());