Even though most of the time to get information from the page URL you will use the server side programming language, you can actually use Javascript to get the different sections that make up the URL.
To get the URL protocol use the following snippet.
window.location.protocol
Returns http / https
To get the URL host name use the following snippet.
window.location.host
Returns github.com
To get the URL pathname of the file use the following snippet.
window.location.pathname
Returns index.html
If a URL has a '#' target selected this snippet will return the value. For the URL of https://gist.github.com/#top.
window.location.hash
This will return top.