jquery, domain, get URL

You don't need jQuery for this, as simple javascript will suffice:

alert(document.domain);

See it in action:

console.log("Output;");  
console.log(location.hostname);
console.log(document.domain);
alert(window.location.hostname)

console.log("document.URL : "+document.URL);
console.log("document.location.href : "+document.location.href);
console.log("document.location.origin : "+document.location.origin);
console.log("document.location.hostname : "+document.location.hostname);
console.log("document.location.host : "+document.location.host);
console.log("document.location.pathname : "+document.location.pathname);

For further domain-related values, check out the properties of window.location online. You may find that location.host is a better option, as its content could differ from document.domain. For instance, the url http://192.168.1.80:8080 will have only the ipaddress in document.domain, but both the ipaddress and port number in location.host.

Similar to the answer before there there is

location.host

The location global has more fun facts about the current url as well. ( protocol, host, port, pathname, search, hash )

jQuery is not needed, use simple javascript:

document.domain