如何js正则表达式判断ip地址的合法性？

function isValidIP(ip)
{
var reg =  /^(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])$/
return reg.test(ip);
}

function submitForm(){
var ip = $("#ipAddress").val();

if(!isValidIP(ip))
{
swal({
title:"请输入正确的ip地址",
type:"warning"
});
return;
}
.....
}