Ajax省市联动 | Ajax省市联动

以JQuery为JS，写的Ajax省市联动。
代码如下:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

    <title>无标题页</title>

    <script src="Script/jquery-1.10.2.js" type="text/javascript"></script>

    <script src="Script/Common.js" type="text/javascript"></script>

    <script type="text/javascript">

    var xhr=false;

    var proSel=false;//selPro

    var citySel=false;//selCity

    var Pid=false;

    $(function(){

        xhr=createXhr();

        proSel=$('#selPro');

        citySel=$('#selCity');

        //加载省下拉框数据

        getAreaData(0);

        //省下拉框发生改变时，加载市下拉框数据

        proSel.change(function(){

            Pid=$(this).val();

            getAreaData(Pid);

        });

    });

    //1.

    function getAreaData(pId){

        //1.open

        xhr.open('get','1-getAreaData.ashx?pid='+pId,true);

        //2.set

        xhr.setRequestHeader('If-Modified-since',0);

        //3.onreadystatechange

        xhr.onreadystatechange=function(){

        if(xhr.readyState==4){

                if(xhr.Status==200){

                    var res=xhr.responseText;

                    if (pId==0){

                        data2Sel(res,proSel);

                        //首次加载时，加载市下拉框数据

                        pId=$(':selected').val();

                        getAreaData(pId);

                    }else{

                    data2Sel(res,citySel);

                    }

                }

            }

        };

        xhr.send();

    }

    //2.

    function data2Sel(data,selOption){

        selOption.empty();

        var res=eval(data);

        for(var i=0;i<res.length;i++){

            var opt=false;

            if(i==2){

            opt=$('<option value='+res[i].Id+' selected=true>'+res[i].Name+'</option>');

            }else{

             opt=$('<option value='+res[i].Id+'>'+res[i].Name+'</option>');

            }

            selOption.append(opt);

        }

    }

    </script>

</head>

<body>

    <select id="selPro">

    </select>

    <select id="selCity">

    </select>

</body>

</html>