js 对于select option的选择之后不调到默认选项js

直接上代码：

<td align="center">性别：
                                    <select name="gender" id="gender">
                                        <option value="0">男</option>
                                        <option value="1">女</option>
                                        <option value="unlimited" selected="selected">不限</option>
                                    </select>
                                </td>

js代码：

 <script type="text/javascript">
      function set_select_checked2(selectId, checkValue){  
            var select = document.getElementById(selectId); 
            for (var i = 0; i < select.options.length; i++){  
                if (select.options[i].value == checkValue){  
                    select.options[i].selected = true;  
                    break;  
                }  
            }  
        }
                    
      $(document).ready(function () {
            var i = ${genderstr};
            set_select_checked2('gender',i);
                   });
        
        </script>