jquery取radio单选按钮

        // var strMess = '<%=Exchange() %>';
//            if (strMess == "兑换成功") {
//                $("#btnSure").show(); //显示提交按钮
//            }
//            else if (strMess.length > 0) {
//                alert(strMess); return false;
//            }

jquery取radio单选按钮的值
$("input[name='items']:checked").val();
jquery radio取值，checkbox取值，select取值，radio选中，checkbox选中，select选中，及其相关 
获取一组radio被选中项的值 
var item = $('input[name=items][checked]').val(); 
获取select被选中项的文本 
var item = $("select[name=items] option[selected]").text(); 
select下拉框的第二个元素为当前选中值
$('#select_id')[0].selectedIndex = 1; 
radio单选组的第二个元素为当前选中值 
$('input[name=items]').get(1).checked = true;

获取值：

文本框，文本区域：$("#txt").attr("value")； 
多选框checkbox：$("#checkbox_id").attr("value")； 
单选组radio： $("input[type=radio][checked]").val(); 
下拉框select： $('#sel').val();

控制表单元素： 
文本框，文本区域：$("#txt").attr("value",'');//清空内容 
$("#txt").attr("value",'11');//填充内容

多选框checkbox： $("#chk1").attr("checked",'');//不打勾 
$("#chk2").attr("checked",true);//打勾 
if($("#chk1").attr('checked')==undefined) //判断是否已经打勾

单选组radio： $("input[type=radio]").attr("checked",'2');//设置value=2的项目为当前选中项 
下拉框select： $("#sel").attr("value",'-sel3');//设置value=-sel3的项目为当前选中项 
$("<option value='1'>1111</option><option value='2'>2222</option>").appendTo("#sel")//添加下拉框的option 
$("#sel").empty()；//清空下拉框

刚开始接触jquery，很多东西不熟悉 
在用$("#id")来获得页面的input元素的时候，发现$("#id").value不能取到值

<script type="text/javascript">
    function add()
    {    
            if ($("#TextBox1").val() == "")
            {
                alert("输入的名称不能为空!");
                $("#TextBox1").focus();
                return false;
            }
            if ($("#TextBox2").val() == "")
            {
                alert("年龄不能为空!");
                $("#TextBox2").focus();
                return false;
            }
            if ($("#TextBox2").val() != "")     //年龄       
            {
                var intvar =/^d+$/;
                if (!intvar.test($("#TextBox2").val()))
                {
                    alert("年龄格式不正确，请输入2位数字!");
                    $("#TextBox2").focus();
                     return false;
                }
            }
            if ($("#TextBox3").val() == "")
            {
                alert("毕业学校不能为空!");
                $("#TextBox3").focus();
                return false;
            }
            if ($("#TextBoxjy").val() == "") //工作经验
            {
                alert("工作经验不能为空!");
                $("#TextBoxjy").focus();
                return false;
            }
            if ($("#TextBoxjy").val() != "")     //工作经验       
            {
                var intvar2 = /^d+$/;
                if (!intvar2.test($("#TextBoxjy").val())) {
                    alert("格式不正确，请输入2位数字!");
                    $("#TextBoxjy").focus();
                    return false;
                }
            }
            var sex = $("input[name='sex']:checked").val();
            var job = $("input[name='job']:checked").val();
            if (sex == undefined)
            {
                alert("没有选择性别！");
                return false;
            }
            if (job == undefined)
            {
                alert("全/兼职没选中");
                return false;
            }  
            if ($("#TextBox5").val() == "") //电话
            {
                alert("电话不能为空!");
                $("#TextBox5").focus();
                return false;
            }
            if ($("#TextBox5").val() != "") {
                var isMobile = /^(?:13d|15d)d{5}(d{3}|*{3})$/;
                var isPhone = /^((0d{2,3})-)?(d{7,8})(-(d{3,}))?$/;
                if (!isMobile.test($("#TextBox5").val()) && !isPhone.test($("#TextBox5").val()))
                {
                    alert("请正确填写手机号或电话号格式不正确");
                    $("#TextBox5").focus();
                    return false;
                }
            }
            if ($("#FreeTextBox1").val()== "")
             {
                alert("工作经验不能为空");
                $("#FreeTextBox1").focus();
                return false;
            }
            var TextBox1 = escape($("#TextBox1").val());
            var TextBox2 = escape($("#TextBox2").val());
            var TextBox3 = escape($("#TextBox3").val());
            var TextBox5 = escape($("#TextBox5").val());    
            var rad1 =escape(sex);
            var rad2 = escape(job);       
            var TextBoxjy =escape($("#TextBoxjy").val());
            var FreeTextBox1=escape($("#FreeTextBox1").val());
            var Label2 = escape($("#Label2").text());
            var Label4 = escape($("#Label4").text());     
              $.ajax({
                type: "POST",
                url: "add.aspx",          
                data:"Label2="+Label2+"&Label4="+Label4+"&TextBox1=" + TextBox1 + "&TextBox2=" + TextBox2 + "&TextBox3=" + TextBox3+"&TextBox5="+TextBox5+"&rad1="+rad1+"&rad2="+rad2+"&TextBoxjy="+TextBoxjy+"&FreeTextBox1="+FreeTextBox1,
                success: function(msg)
                {
                    if (msg == "ok")
                    {
                        alert("数据提交成功!");
                        window.location.href = 'JobList.aspx';
                    }
                    else
                    {
                        alert("数据提交失败!");
                    }                 
                }
            });
                 
    }
</script>

                       <asp:Label ID="Label1" runat="server"></asp:Label>                                  
                              <asp:Label ID="msg" runat="server" Visible="false"></asp:Label>                                    
                                    <asp:Label ID="Label2" runat="server"></asp:Label>
                                                               <asp:Label ID="Label4" runat="server" Text="Label"></asp:Label>
                                                                                
                       
                                    <input  type="Radio" name="job" value="全职" id="RadioButton3" runat="server"/>   
                                    <input  type="Radio" name="job" value="兼职" id="RadioButton4" runat="server"/>                                       
                                      =                                                        <input id="Submit1" type="button" value="提交简历" onclick="return add()" style="height:35px"/>
                                 
                            
           

           

 

后来终于在伟大的百度帮助下，找到了问题的原因： 
$("")是一个jquery对象，而不是一个dom element

value是dom element的属性

jquery与之对应的是val

val() :获得第一个匹配元素的当前值。

val(val):设置每一个匹配元素的值。

所以，代码应该这样写：

取值：val = $("#id")[0].value; 
赋值： 
$("#id")[0].value = "new value"; 
或者$("#id").val("new value");

或者这样也可以：val = $("#id").attr("value");

  function add() 
    {    
        var Label2 = $("#Label2").text();
        var Label4 = $("#Label4").text();
        alert(Label2);
        if (Label2 == "" && Label4 == "") 
        {
            if ($("#TextBox1").val() == "") 
            {
                alert("输入的名称不能为空!");
                $("#TextBox1").focus();
                return false;
            }
            if ($("#TextBox2").val() == "") 
            {
                alert("年龄不能为空!");
                $("#TextBox2").focus();
                return false;
            }
            if ($("#TextBox2").val() != "")     //年龄        
            {
                var intvar =/^d+$/;
                if (!intvar.test($("#TextBox2").val())) 
                {
                    alert("年龄格式不正确，请输入2位数字!");
                    $("#TextBox2").focus();
                     return false;
                }
            }
            if ($("#TextBox3").val() == "") 
            {
                alert("毕业学校不能为空!");
                $("#TextBox3").focus();
                return false;
            }
            if ($("#TextBoxjy").val() == "") //工作经验 
            {
                alert("工作经验不能为空!");
                $("#TextBoxjy").focus();
                return false;
            }
            if ($("#TextBoxjy").val() != "")     //工作经验        
            {
                var intvar2 = /^d+$/;
                if (!intvar2.test($("#TextBoxjy").val())) {
                    alert("格式不正确，请输入2位数字!");
                    $("#TextBoxjy").focus();
                    return false;
                }
            }
//            var RadioButton1 = $('input:radio[name="RadioButton1"]:checked').val(); //性别
//            var RadioButton2 = $('input:radio[name="RadioButton2"]:checked').val(); //性别
//            if (RadioButton1 == null || RadioButton2==null) 
//            {
//                alert("性别没选中!");
//               // $("#TextBoxjy").focus();
//                return false;
//            }
//            var RadioButton3 = $('input:radio[name="RadioButton3"]:checked').val(); //性别
//            var RadioButton4 = $('input:radio[name="RadioButton4"]:checked').val(); //性别
//            if (RadioButton3 == null || RadioButton4==null)
//             {
//                alert("全/兼职没选中!");
//                // $("#TextBoxjy").focus();
//                return false;
//            }  
//            if ($("#TextBox5").val() == "") //电话 
//            {
//                alert("电话不能为空!");
//                $("#TextBox5").focus();
//                return false;
//            }
//            if ($("#TextBox5").val() != "") {
//                var isMobile = /^(?:13d|15d)d{5}(d{3}|*{3})$/;
//                var isPhone = /^((0d{2,3})-)?(d{7,8})(-(d{3,}))?$/;
//                if (!isMobile.test($("#TextBox5").val()) && !isPhone.test($("#TextBox5").val())) 
//                {
//                    alert("请正确填写手机号或电话号格式不正确");
//                    $("#TextBox5").focus();
//                    return false;
//                }
//            }
//            if ($("#FreeTextBox1").val() != "")
//             {
//                alert("工作经验不能为空");
//                $("#FreeTextBox1").focus();
//                return false;
//            }
//            var TextBox1 = escape($("#TextBox1").val());
//            var TextBox2 = escape($("#TextBox2").val());
//            var TextBox3 = escape($("#TextBox3").val());
//            var TextBox5 = escape($("#TextBox5").val());     
//            var rad1 =escape(RadioButton1);
//            var rad2 =escape(RadioButton2);
//            var rad3 =escape(RadioButton3);
//            var rad4 =escape(RadioButton4);
//            var TextBoxjy =escape($("#TextBoxjy").val());
//            var FreeTextBox1=escape($("#FreeTextBox1").val()); 
//            var Label2 = escape($("#Label2").text());
//            var Label4 = escape($("#Label4").text());
//            if(rad1!=null&&rad3!=null)
//            {       
//                $.ajax({
//                    type: "POST",
//                    url: "Control/WebUserControl.ascx",
//                    data:"Label2="+Label2+"&Label4="+Label4+"&TextBox1=" + TextBox1 + "&TextBox2=" + TextBox2 + "&TextBox3=" + TextBox3+"&TextBox5="+TextBox5+"&rad1="+rad1+"&rad3="+rad3+"&TextBoxjy="+TextBoxjy+"&FreeTextBox1="+FreeTextBox1+",
//                    success: function(msg)
//                    {
//                        if (msg == "cf") 
//                        {
//                            alert("请换个姓名!");
//                        }
//                        if (msg == "ok") 
//                        {
//                            alert("数据提交成功!");
//                            window.location.href = 'JobList.aspx';
//                        }
//                        else 
//                        {
//                            alert("数据提交失败!");
//                        }                    
//                    }
//                });
//           }
//       
              
    }
</script>