删除select元素里面的所有option及二级分类查询

删除select元素里面的所有option

三种方法：

<select id="city"> 
    <option>湖南</option> 
    <option>上海</option> 
</select>

使用jquery清空

$("#city").find("option").remove(); 
或者 
$("#city").empty(); 
或者
$("#city").html("");

二级查询

/**
 * 二级分类查询
 * @param category
 * @return
 */
@GetMapping("/getMerchantChildrenName")
@ResponseBody
public Map<String,Object> getMerchantChildrenName(Category category){
    Map param = new HashMap();
    List<Category> list2 = merchantService.merchantChildrenName(category);
    if(CollectionUtils.isNotEmpty(list2)){
        param.put("status","200");
        param.put("msg","查询成功");
        param.put("data",list2);
    }
    return  param;
}

<div class="form-group">    
   <label class="col-sm-3 control-label">parentId：</label>
   <div class="col-sm-8">
      <select class="form-control" name="parentId" id="parentId" onchange="getChildrenName(this.value)">
         <option value="-1">请选择</option>
         <option   th:each="parentId:${list}" th:value="${parentId.id}" th:text="${parentId.name }"></option>
      </select>
   </div>
</div>

<div class="form-group">   
   <label class="col-sm-3 control-label">agencyId：</label>
   <div class="col-sm-8">
      <select class="form-control" name="agencyId" id="agencyId"></select>
   </div>
</div>




var prefix = ctx + "merchant/merchant"
var url = prefix + "/getMerchantChildrenName";
function getChildrenName(parentId) {
    $.ajax({
        type: "GET",
        url: url,
        dataType:'json',
        data: {
            "parentId": parentId,
        },
        success: function(param) {
            console.log(param)
            if (param.status==200){
                $("#agencyId").empty();
                var lb = $("#agencyId");//列表框id
                //方法1：添加默认节点
                lb.append("<option value='-1'>--请选择--</option>");
                //转成Json对象
                var result = eval(param.data);
                //循环遍历 下拉框绑定
                $(result).each(function (key) {
                    //赋值
                    var opt = $("<option></option>").text(result[key].name).val(result[key].id);
                    lb.append(opt);
                });
            }  else {
            layer.msg('加载分类失败');
           }
        },
        error: function () {
            layer.msg('error');
        }
    });

}




/**
 * 修改merchant info，agency下属的商户
 */
@RequiresPermissions("merchant:merchant:edit")
@GetMapping("/edit/{id}")
public String edit(@PathVariable("id") Long id, Model model,Category category) {
    Merchant merchant = merchantService.selectMerchantById(id);
    model.addAttribute("merchant", merchant);
    if(merchant.getAgencyId()!=null){
        Category category2=merchantService.getSingleCategory(merchant.getAgencyId());//单个子分类
        model.addAttribute("category2", category2);
    }
    if (category.getParentId() == null) {//一级分类
        category.setParentId(0L);
        List<Category> list = merchantService.merchantParentName(category);
        model.addAttribute("list", list);
    }
    return prefix + "/edit";
}

编辑

<div class="form-group">    
    <label class="col-sm-3 control-label">parentId：</label>
    <div class="col-sm-8">
        <select class="form-control" name="parentId" id="parentId" onchange="getEditChildrenName(this.value)">
            <option value="-1">请选择</option>
            <option   th:each="parentId:${list}" th:selected="${parentId.id==merchant.parentId}"
                      th:value="${parentId.id}" th:text="${parentId.name }"></option>
        </select>
    </div>
</div>
<div class="form-group">   
    <label class="col-sm-3 control-label">agencyId：</label>
    <div class="col-sm-8">
        <select class="form-control" name="agencyId" id="agencyId" >
            <option  th:value="${category2.id}" th:text="${category2.name }"></option>
        </select>
    </div>
</div>