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";
 5function 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
17function 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
43function 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}
68function 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());