js三级联动

<select name="" id="p">
　　<option value="0">请选择省</option>
</select>
<select name="" id="c">
　　<option value="0">请选择市</option>
</select>
<select name="" id="a">
　　<option value="0">请选择区</option>
</select>

                        (function(doc) {
                            if(data.code == 200) {
                                var result = data.result;
                                var poption, coption, aoption;
                                for(var i = 0; i < result.length; i++) {
                                    poption = new Option(result[i].name, result[i].id);
                                    doc.querySelector("#p").options.add(poption);
                                }

                                //省点击事件
                                doc.querySelector("#p").addEventListener("change", function() {
                                    doc.querySelector("#c").length = 1;
                                    doc.querySelector("#a").length = 1;
                                    var pval = this.value;
                                    for(var i = 0; i < result.length; i++) {
                                        if(result[i].id == pval) {
                                            var city = result[i].child;
                                            for(var j = 0; j < city.length; j++) {
                                                coption = new Option(city[j].name, city[j].id);
                                                doc.querySelector("#c").options.add(coption);
                                            }
                                            return;
                                        }
                                    }

                                });

                                //市的点击事件
                                doc.querySelector("#c").addEventListener("change", function() {
                                    doc.querySelector("#a").length = 1;
                                    var cval = this.value;
                                    for(var i = 0; i < result.length; i++) {
                                        var city = result[i].child;
                                        for(var j = 0; j < city.length; j++) {
                                            if(city[j].id == cval) {
                                                var aera = city[j].child;
                                                for(var k = 0; k < aera.length; k++) {
                                                    aoption = new Option(aera[k].name, aera[k].id);
                                                    doc.querySelector("#a").options.add(aoption);
                                                }
                                            }

                                        }
                                    }

                                });

                            }
                        }(document));

var data = {
    "code": "200",
    "msg": "success",
    "result": [
        {
            "id": "01",
            "name": "江苏省",
            "child": [
                {
                    "id": "011",
                    "name": "南京市",
                    "child": [
                        {
                            "id": "0111",
                            "name": "雨花台区"
                        }, {
                            "id": "0112",
                            "name": "秦淮区"
                        }, {
                            "id": "0113",
                            "name": "玄武区"
                        }, {
                            "id": "0114",
                            "name": "白下区"
                        }
                    ]
                }, {
                    "id": "012",
                    "name": "苏州市",
                    "child": [
                        {
                            "id": "0121",
                            "name": "吴中区"
                        }, {
                            "id": "0122",
                            "name": "姑苏区"
                        }, {
                            "id": "0123",
                            "name": "高新区"
                        }, {
                            "id": "0124",
                            "name": "开发区"
                        }
                    ]
                }, {
                    "id": "013",
                    "name": "扬州市",
                    "child": [
                        {
                            "id": "0131",
                            "name": "第一区"
                        }, {
                            "id": "0132",
                            "name": "第二区"
                        }, {
                            "id": "0133",
                            "name": "第三区"
                        }, {
                            "id": "0134",
                            "name": "第四区"
                        }
                    ]
                }
            ]
        }, {
            "id": "02",
            "name": "浙江省",
            "child": [
                {
                    "id": "021",
                    "name": "杭州市",
                    "child": [
                        {
                            "id": "0211",
                            "name": "雨花台区"
                        }, {
                            "id": "0212",
                            "name": "秦淮区"
                        }, {
                            "id": "0213",
                            "name": "玄武区"
                        }, {
                            "id": "0214",
                            "name": "白下区"
                        }
                    ]
                }, {
                    "id": "022",
                    "name": "宁波市",
                    "child": [
                        {
                            "id": "0221",
                            "name": "吴中区"
                        }, {
                            "id": "0222",
                            "name": "姑苏区"
                        }, {
                            "id": "0223",
                            "name": "高新区"
                        }, {
                            "id": "0224",
                            "name": "开发区"
                        }
                    ]
                }, {
                    "id": "023",
                    "name": "温州市",
                    "child": [
                        {
                            "id": "0231",
                            "name": "第一区"
                        }, {
                            "id": "0232",
                            "name": "第二区"
                        }, {
                            "id": "0233",
                            "name": "第三区"
                        }, {
                            "id": "0234",
                            "name": "第四区"
                        }
                    ]
                }
            ]
        }
    ]
}