document.referrer works when a user clicks on a link to navigate to the current page but I don't think it works when you do a manual redirect in a Javascript function.

The only way I can think of is to store the URL of the page before the user is redirected to your current page.

You could store it in a hidden form or a cookie.

This question has also been asked before and its worth having a quick read through here. How do you get the previous url in Javascript?

I took this cookie example from it to show you what I mean.

$.cookie(previousUrl, window.location.href, {path:/});