使用场景是：一个下拉框有太多值 需要搜索做匹配

一：加载文件

<link  rel="stylesheet" />
<script class="lazyload" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" data-original="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"></script>

二：html代码

<select name="hospital_id" id="searchHospital">
    <option value="0">请选择医院</option>
    <foreach name="hospitalData" item="list">
        <option value="{$list.hospital_id}" 
            <if condition="$_GET['hospital_id'] eq $list['hospital_id']">selected</if>>
        {$list.hospital_name}
        </option>
    </foreach>
</select>

三：js

<script>
    $(function(){
        $('#searchHospital').select2({
            placeholder: "Select a state"
        });
    });
</script>