In a browser, a user navigates from one URL to another. How do I store all the URLs visited in an array variable? Moreover there shouldn't be duplicates in the array. For e.g. if a user visits, say, www.google.com, it should be stored in the array. If he visits www.google.com again during the same session (or until the user closes the browser window), it shouldn't get added to the array again. Also each open browser window should have it's own array variable. For e.g. if a user visits www.site1.com & www.site2.com in the 1st browser window, the array should hold www.site1.com & www.site2.com. If the user opens another browser window & visits www.abcd.com & www.efgh.com, then the array in the 2nd browser window should hold www.abcd.com & www.efgh.com.

How do I accomplish these tasks?