ASP和AJAX应用一例,检测注册用户是否有效

t1.html

<script language="javascript" type="text/javascript">
var xmlHttp = false;
try {
  xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
  try {
    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
  } catch (e2) {
    xmlHttp = false;
  }
}
if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
  xmlHttp = new XMLHttpRequest();
}

function callServer() {
  var u_name = document.getElementById("u_name").value;
  if ((u_name == null) || (u_name == "")) return;
  var url = "cu.asp?name=" + escape(u_name);
  xmlHttp.open("GET", url, true);
  xmlHttp.onreadystatechange = updatePage;
  xmlHttp.send(null);  
}

function updatePage() {
  if (xmlHttp.readyState < 4) {
test1.innerHTML="loading...";
  }
  if (xmlHttp.readyState == 4) {
    var response = xmlHttp.responseText;
test1.innerHTML=response;
  }
}
</script>


<form name="form1" action="t1.asp" method="post" autocomplete="off">
用户名: <input type="text" name="u_name" id="u_name" onChange="callServer();" />
<span id="test1">是否能注册</span><br>
密 码：<input type="password" />
<input type="submit" value="注册" />
</form>



cu.asp

<%
Response.Buffer = True
Response.ExpiresAbsolute = Now() - 1
Response.Expires = 0
Response.CacheControl = "no-cache"
Response.AddHeader "Pragma", "No-Cache"
%>
<!--＃i nclude file="conn.asp"-->
<%
name=request.querystring("name")
Set rs = Server.CreateObject ("ADODB.Recordset")
sql = "Select * from u_ser where u_name='"&name&"'"
rs.Open sql,conn,1,1
if rs.eof and rs.bof then
response.write("true")
else
response.write("false")
end if
rs.close
set rs=nothing
call CloseDatabase
%>