省市区三级级联，使用layui后端框架，可自主修改为无限级

<div class="layui-form">
    <div class="layui-form-item">
            <label class="layui-form-label">地址</label>
            <div class="layui-input-inline">
                <select name="province" lay-filter="state">
                    <option value="0">请选择</option>
                </select>
            </div>
            <div class="layui-input-inline">
                <select name="city" lay-filter="state">
                    <option value="0">请选择</option>
                </select>
            </div>
            <div class="layui-input-inline">
                <select name="district" lay-filter="state">
                    <option value="0">请选择</option>
                </select>
            </div>
        </div>
</div>

<script type="text/javascript">
        layui.use('form', function(){
            var form = layui.form,
                layer = layui.layer,
                $ = layui.jquery;
            var url =  '你的URL'; //数据请求地址:根据父级ID获取下一级数据array
            var province = ""; //初始化省名
            var city = ""; //初始化市名
            var district = ""; //初始化县/区名
            //获取省数据
            getJSON(url,$("select[name='province']").closest("div"));
            //切换时获取子数据
            form.on('select(state)', function(data){
                $that = $(data.elem);
                urls = url+"?pid="+data.value;
                getJSON(urls,$that.closest("div").next());
            });

            function getJSON(urls,even){
                $.getJSON(urls, function(json){
                    var pid = 0;
                    var name = even.find("select").attr("name");
                    var select = "<select name=\"" + name + "\" lay-filter=\"state\">";
                    select += "<option value=\"0\">请选择 </option>";
                    $(json).each(function(){
                        select += "<option value=\"" + this.id + "\"";
                        if(province == this.name || city == this.name || district == this.name){
                            select += " selected=\"selected\" ";
                            pid = this.id;
                        }
                        select += ">" + this.name + "</option>";
                    });
                    select += "</select>";
                    even.html(select);
                    var nextName = even.next().find("select").attr("name");
                    even.next().html("<select name=\"" + nextName + "\" lay-filter=\"state\"><option value=\"0\">请选择 </option></select>");
                    form.render('select');
                    if(pid != 0){
                        getJSON(url+"?pid="+pid,even.next());
                    }
                });
            }
        });
    </script>

    getJSON方法异步返回数据格式：
    0:{id: "99", name: "东丽区"}
    1:{id: "100", name: "和平区"}