layui下拉选择框select不显示

<form class="layui-form">
    <!-- 这里是form里面的代码 输入框，选择框、复选框，单选框等等 -->
</form>

layui.use(‘form‘, function(){
    var form = layui.form; //只有执行了这一步，部分表单元素才会自动修饰成功

    //……

    //但是，如果你的HTML是动态生成的，自动渲染就会失效
    //因此你需要在相应的地方，执行下述方法来进行渲染
    form.render();
});

form.render(); //更新全部
form.render(‘select‘); //刷新select选择框渲染
//……

<!-- HTML 示例 -->
<div class="layui-form" lay-filter="test1">
  …
</div>
 
<div class="layui-form" lay-filter="test2">
  …
</div>
<!-- JS 示例 -->
<script>
layui.use(‘form‘, function(){
    var form = layui.form,
    form.render(null, ‘test1‘); //更新 lay-filter="test1" 所在容器内的全部表单状态
    form.render(‘select‘, ‘test2‘); //更新 lay-filter="test2" 所在容器内的全部 select 状态
    //……
});
</script>

<div id="layer-test" style="display: none;">
  <form class="layui-form">
    <div class="layui-form-item">
      <label class="layui-form-label">复选框</label>
      <div class="layui-input-block">
        <input type="checkbox" name="CSDN" lay-filter="like" title="复选框一" value="dongsir">
        <input type="checkbox" name="CSDN" lay-filter="like" title="复选框二" value="董先生">
      </div>
    </div>
    <div class="layui-form-item">
      <label class="layui-form-label">开关关</label>
      <div class="layui-input-block">
        <input type="checkbox" name="switch" lay-skin="switch" value="董辉">
      </div>
    </div>
    <div class="layui-form-item">
      <label class="layui-form-label">开关开</label>
      <div class="layui-input-block">
        <input type="checkbox" name="switch" checked lay-skin="switch" value="董先生的CSDN">
      </div>
    </div>
    <div class="layui-form-item">
      <div class="layui-input-block">
        <button class="layui-btn" lay-submit lay-filter="*">立即提交</button>
      </div>
    </div>
  </form>
</div>
<script src="layui/layui.js"></script>
<script>
layui.use(‘form‘, function(){
  var form = layui.form,
      $ = layui.$;

    //layer示例

    layer.open({
        type: 1,
        title: [‘董先生的CSDN博客‘],
        shade: 0.4,
        area:[‘900px‘, ‘650px‘],
        content: $("#layer-test").html(),
        success: function(layero, index){
          form.render();
        }
    });
});
</script>