I know I can use window.location.pathname to return a url, but how do I parse the url?

I have a url like this: http://localhost/messages/mine/9889 and I'm trying to check to see if "mine" exists in that url?

So, if "mine" is the second piece in that url, I want to write an if statement based on that...

if(second argument == 'mine') { do something }