html中JQ（jquery）中获取select被选中的值

<select name="r_id" class="r_id">
                            <option value="">请选择班级</option>
                            {foreach $data as $vo}
                            <option value="{$vo.r_id}" {if condition="input('r_id')==$vo.r_id " }selected{/if}>{$vo.name}</option>
                            {/foreach}
                        </select>


<script>
    $('.r_id').change(function () {
       var checkValue =  $("select option:selected").val();
        
    })
</script>