layui修改select的值的方法

<input id="ggg" style="display: none;" value="{$hopedepart}" />
<input id="ddd" style="display: none;" value="{$sex}" />

<script>
    function firstload() {
        var str = "#hopedepart option[value='" + $("#ggg").val() + "']";
        var sex = "input:radio[value='" + $("#ddd").val() + "']";
     //   document.write(sex);
        $("#hopedepart option[value='']").removeAttr("selected"); //2.移除默认选项的选中状态  removeAttr("selected")
        $(str).attr("selected", "selected");
        $(sex).attr('checked', 'true');
    }
    firstload();
 
</script>

<script src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
    <!--引入jQuery-->
 
<input type="hidden" id="position_hidden_id" th:value="${staff?.position}">
 
                    <select name='position' id="position_id" lay-filter='aihao'>
                        <option value=''></option>
<option value='前端开发'>前端开发</option>
<option value='后端开发'>后端开发</option>
<option value='产品'>产品</option>
<option value='测试'>测试</option>
<option value='UI'>UI</option>
<option value='人事'>人事</option>
<option value='财务'>财务</option>
<option value='市场'>市场</option>
<option value='总经理'>总经理</option>
</select>
 
<script>
//alert("ggg");
$(document).ready(function(){ 
        var key1=$("#position_hidden_id").val();
        //根据值让option选中 
        $("#position_id option[value='"+key1+"']").attr("selected","selected"); 
       
    });
</script>