1 <form method="post" action="">
 2         省/市：<select id="province" onchange="alter(this.selectedIndex)"></select>
 3         市/区：<select id="city"></select>
 4     </form>
 5     <script type="text/javascript">
 6         //定义省/直辖市数组
 7         var arr_province = ["请选择省/直辖市","北京市","上海市","广东省"];
 8         //定义市/区二维数组
 9         var arr_city = [
10                         ["请选择市/区"],
11                         ["东城区","西城区","朝阳区","宣武区","昌平区","大兴区","丰台区","海淀区"],
12                         ['宝山区','长宁区','丰贤区', '虹口区','黄浦区','青浦区','南汇区','徐汇区','卢湾区'],
13                         ['广州市','惠州市','汕头市','珠海市','佛山市','中山市','东莞市']
14                     ];
15         //获取对象
16         var province = document.getElementById('province');
17         var city = document.getElementById('city');
18         //初始化菜单
19         onload = function () {
20             //指定省option标记的个数
21             province.length = arr_province.length;
22             //数组数据写入<option>标记中
23             for(var i = 0; i < arr_province.length; i++){
24                 province.options[i].text = province.options[i].value = arr_province[i];
25             }
26             //设置省列表默认选项
27             var index = 0;
28             province.index = index;
29             //指定城市option标记的个数
30             city.length = arr_city[index].length;
31             //数组数据写入option标记
32             for (var j = 0; j < arr_city[index].length; j++) {
33                 city.options[j].text = city.options[j].value = arr_city[index][j];
34             }
35         }
36         function alter(index) {
37             //修改省列表的选择项
38             province.index = index;
39             //指定城市option标记的个数
40             city.length = arr_city[index].length;
41             //数组中的数据写入option标记
42             for (var j = 0; j < arr_city[index].length; j++) {
43                 city.options[j].text = city.options[j].value = arr_city[index][j];
44             }
45         }
46     </script>

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