select下拉单选框

//1、layui绑定数据
<select name="roleIds" id="userEditRoleSel" lay-filter="selectRoeIds" lay-verify="required" lay-search="">
       <option value="">请选择角色</option>
</select>

//JS获取下拉框数据
$.post(url, data, function (res) {
      if (res.data.length > 0) {
      $.each(res.data, function (key, val) {
          var option = "";
          if (mData.roleName == val.roleName) option = $("<option selected='selected'>").val(val.roleId).text(val.roleName);//选中赋值
           else option = $("<option>").val(val.roleId).text(val.roleName);
             $("#userEditRoleSel").append(option);
        });
              layui.form.render('select');

       }
}, 'json');

//2、写死数据
<select name="sex">
       <option value="">选择性别</option>
       <option value="男">男</option>
       <option value="女">女</option>
</select>