[javascript] how to get the host url using javascript from the current page

I like this one depending of purpose

window.location.href.split("/")[2] == "localhost:17000" //always domain + port

You can apply it on any url-string

var url = "http://localhost:17000/sub1/sub2/mypage.html?q=12";
url.split("/")[2] == "localhost:17000"
url.split("/")[url.split("/").length-1] == "mypage.html?q=12"

Removing protocol, domain & path from url-string (relative path)

var arr = url.split("/");
if (arr.length>3)
   "/" + arr.splice(3, arr.length).join("/") == "/sub1/sub2/mypage.html?q=12"