<script language="javascript" type="text/javascript">
function CheckIsNull()
    {
     var tbx1id=document.getElementById("txtname");
     var userid=jQuery.trim(tbx1id.value);
     if(userid==""||userid==null)
     {
          tbx1id.focus();
          tbx1id.value="";
          return false;
     }
     var tbx2id=document.getElementById("txtpwd");
     var userpwd=jQuery.trim(tbx2id.value);
     if(userpwd==""||userpwd==null)
     {
         tbx2id.focus();
         tbx2id.value="";
         return false;
     }
    $.ajax({
                    //要用post方式   
                    type: "Post",
                    //方法所在页面和方法名   
                    url: "Login.aspx/CheckLogin", 
                    data: ="{'userid':'"+ userid +"','pwd':'"+ userpwd +"'}", 
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (data) {
                        //返回的数据用data.d获取内容
                       alert(data.d);
                    },
                    error: function (err) {
                        alert("wrong");
                    }
                });
                //禁用按钮的提交   
                //return false;
    }
</script>
<div id="divlogin" onclick="CheckIsNull()" >  LogIn</div>当我点击divlogin这个div时,弹出错误CheckIsNull未定义,如果我把$ajax这个函数注释掉,就不会报错,ajax不能直接放在js函数中用吗?