js获取客户端用户IP

<script src="http://pv.sohu.com/cityjson?ie=utf-8"></script>

<script type="text/javascript">

     document.write(returnCitySN["cip"]+','+returnCitySN["cname"])

</script>

http://pv.sohu.com/cityjson?ie=utf-8 
返回结果：
var returnCitySN = {"cip": "203.100.83.125", "cid": "CN", "cname": "CHINA"};