关于"layui"框架选择框不显示的问题的处理

官网源码：

<form class="layui-form" action="">
  <div class="layui-form-item">
    <label class="layui-form-label">输入框</label>
    <div class="layui-input-block">
      <input type="text" name="title" required  lay-verify="required" placeholder="请输入标题" autocomplete="off" class="layui-input">
    </div>
  </div>
  <div class="layui-form-item">
    <label class="layui-form-label">密码框</label>
    <div class="layui-input-inline">
      <input type="password" name="password" required lay-verify="required" placeholder="请输入密码" autocomplete="off" class="layui-input">
    </div>
    <div class="layui-form-mid layui-word-aux">辅助文字</div>
  </div>
  <div class="layui-form-item">
    <label class="layui-form-label">选择框</label>
    <div class="layui-input-block">
      <select name="city" lay-verify="required">
        <option value=""></option>
        <option value="0">北京</option>
        <option value="1">上海</option>
        <option value="2">广州</option>
        <option value="3">深圳</option>
        <option value="4">杭州</option>
      </select>
    </div>
  </div>
  <div class="layui-form-item">
    <label class="layui-form-label">复选框</label>
    <div class="layui-input-block">
      <input type="checkbox" name="like[write]" title="写作">
      <input type="checkbox" name="like[read]" title="阅读" checked>
      <input type="checkbox" name="like[dai]" title="发呆">
    </div>
  </div>
  <div class="layui-form-item">
    <label class="layui-form-label">开关</label>
    <div class="layui-input-block">
      <input type="checkbox" name="switch" lay-skin="switch">
    </div>
  </div>
  <div class="layui-form-item">
    <label class="layui-form-label">单选框</label>
    <div class="layui-input-block">
      <input type="radio" name="sex" value="男" title="男">
      <input type="radio" name="sex" value="女" title="女" checked>
    </div>
  </div>
  <div class="layui-form-item layui-form-text">
    <label class="layui-form-label">文本域</label>
    <div class="layui-input-block">
      <textarea name="desc" placeholder="请输入内容" class="layui-textarea"></textarea>
    </div>
  </div>
  <div class="layui-form-item">
    <div class="layui-input-block">
      <button class="layui-btn" lay-submit lay-filter="formDemo">立即提交</button>
      <button type="reset" class="layui-btn layui-btn-primary">重置</button>
    </div>
  </div>
</form>
 
<script>
//Demo
layui.use('form', function(){
  var form = layui.form;
  
  //监听提交
  form.on('submit(formDemo)', function(data){
    layer.msg(JSON.stringify(data.field));
    return false;
  });
});
</script>

运行结果：

　　　　

解决方法：

　　　　导入代码从

　　　　　　　　

<link rel="stylesheet" href="layui/css/layui.css">
<script src="layui/layui.all.js"></script>

　　　　　换为

　　

<link rel="stylesheet" href="layui/css/layui.css" media="all">
<script src="layui/layui.js" type="text/javascript"></script>
<script src="jquery/jquery-1.9.1.min.js" type="text/javascript"></script>

即可达到预期效果：