js 递加html表单里面行

js 递增html表单里面行
   <div class="form2">
                <h5>学员信息</h5>
                <table cellspacing="5" cellpadding="0" border="0" width="100%">
                    <tbody>
                    <tr>
                        <th width="50">姓名</th>
                        <th width="50">性别</th>
                        <th width="80">部门</th>
                        <th width="60">职务</th>
                        <th width="110">公司电话</th>
                        <th width="110">手机</th>
                        <th>电子邮件</th>
                    </tr>
                    
                    <tr>
                        <td>
                        <input id="UserName" name="UserName" type="text" value="" style="width:50px;"   /></td>
                        <td>
                    <select id="Gender" name="Gender"  style="border-width:0; width:50px" tabindex="0"><option value="nan" selected>男</option><option value="nv" >女</option></select  
                        </td>
                        <td>
                        <input id="Department" name="Department" type="text" value=""  style="width:80px;"   /></td>
                        <td>