ajax省市县三级联动

jsp部分代码：

<div id="pro"></div>
<div id="city"></div>
<div id="place"></div>

js代码：

// 省市县三级联动
    $(function(){
        var ss = "";
        $.get("获取所有省份的action的URL",function(data){
            var json = eval("(" + data + ")");
            ss = ss + "<select onchange='getAllCity(this)' >";
            ss = ss + "<option>== 请选择省（区、市）  ==</option>";
            for ( var i = 0; i < json.length; i++) {
                ss = ss + "<option value="+json[i].id+">" + json[i].name;
                ss = ss + "</option>";
            }
            ss = ss + "</select>";
            $("div#pro").html(ss);
        });
    })
    
    function getAllCity(obj) {
        var ss = "";
        $.get("根据省份ID获取对应所有城市的action的URL?previousId=" + obj.value , function(data) { 
            var json = eval("(" + data + ")");
            ss +="<select onchange='getPalce(this)' >";
            ss +="<option>== 请选择城市 ==</option>";
            for ( var i = 0; i < json.length; i++) {
                ss += "<option value="+json[i].id+">" + json[i].name;
                ss += "</option>";
            }
            ss = ss + "</select>";
            $("div#city").html(ss);

        });
    }
    
    function getPalce(obj){
        var ss="";
        $.get("根据城市ID获取对应所有县区的action的URL?area="+obj.value,function(data){
            var json=eval("(" + data + ")");
            ss +="<select>";
            ss +="<option>== 请选择县区 ==</option>";
            for(var i=0;i<json.length;i++){
                ss += "<option value="+json[i].examPlace+">" + json[i].examPlaceName;
                ss += "</option>";
            }
            ss = ss + "</select>";
            $("div#llace").html(ss);
        });
    
        }