js读XML三级联动

XML文件：

<?xml version="1.0" encoding="utf-8" ?>
<Root>
  <country name="中国" id="1001">
    <province name="广东" id="1001001">
      <city name="深圳" id="1001001001"></city>
      <city name="广州" id="1001001002"></city>
      <city name="珠海" id="1001001003"></city>
      <city name="东莞" id="1001001004"></city>
    </province>