SOURCE

layui.use(['layer', 'form'], function(){
 
});

<form class="layui-form" action="">
  
  <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>
 
</form>