首先需要的js及css，可以直接在layui官网上下载：https://www.layui.com/

相关引用：

<script src="~/layui-v2.4.5/layui/layui.js"></script>
<script src="~/layui-v2.4.5/layui/layui.all.js"></script>
<link href="~/layui-v2.4.5/layui/css/layui.css" rel="stylesheet" />
<script src="~/layui-v2.4.5/layui/lay/modules/layer.js"></script>

增加如下测试html代码：

<div class="layui-form">
        <div class="layui-fluid">
            <div class="layui-form layui-col-md12">
                <div class="layui-form-item">
                    <div class="layui-col-md4">
                        <label class="layui-form-label">城市<span style="color:red">●</span></label>
                        <div class="layui-input-block">
                            <select name="select_base_cityname" id="select_base_cityname" lay-filter="select_base_cityname" xm-select="select_base_cityname" xm-select-type="1">
                                <option value=""></option>
                                <option value="1">北京</option>
                                <option value="2">上海</option>
                                <option value="3">天津</option>
                                <option value="4">重庆</option>
                            </select>
                        </div>
                    </div>
                </div>
                <div class="layui-row ">
                    <div class="test-table-reload-btn" style="margin-bottom: 10px;">
                        <button type="button" class="layui-btn layui-btn-danger" lay-submit lay-filter="btn_submit" id="btn_submit"><i class="layui-icon">&#xe681</i>获取</button>

</div>
                </div>
            </div>
        </div>
    </div>

配置select多选相关：

<link href="~/layui-v2.4.5/layui/formSelects-v4.css" rel="stylesheet" />
<script src="~/layui-v2.4.5/layui/formSelects-v4.js"></script>
<script type="text/javascript">
    //全局定义一次, 加载formSelects
    layui.config({
        base: '/' //此处路径请自行处理, 可以使用绝对路径
    }).extend({
        formSelects: 'formSelects-v4'
    });
    //加载模块
    layui.use(['jquery', 'formSelects'], function () {
        var formSelects = layui.formSelects;

});
</script>

到这一步，已经能显示多选效果了，如图：

接下来就直接获取选择的值就行了：

<script type="text/javascript">
    layui.use(['form', 'layer', 'jquery', 'table', 'laydate', 'element', 'upload', 'flow'], function () {
        var $$ = layui.jquery;
        var form = layui.form,
            layer = parent.layer == undefined ? layui.layer : parent.layer,
            //layer = layui.layer,
            table = layui.table,
            laydate = layui.laydate,
            element = layui.element,
            upload = layui.upload,
            flow = layui.flow;
        form.render();

form.on('submit(btn_submit)', function (obj) {
            layer.confirm('确认录入无误吗？', {
                btn: ['确认', '再看看']
            }, function () {  
                var getName = JSON.stringify(layui.formSelects.value('select_base_cityname', 'name'));//取值name数组
                layer.msg("你选择的值为：" + getName, { offset: '150px', icon: 1, time: 5000 }, function () {                  
                });
            });
        });

});

</script>

更详细的文档，可以参考：https://hnzzmsf.github.io/example/example_v4.html#select_value

总结：layui还是相对不错的前端框架，在一些项目中，都会看到它的身影。