I recently flagged this as "not an answer". It's a link-only answer without an actual link. Full text:
For anyone still stuck, codeacademy.com has an excellent practical tutorial on prototypes in its js lessons called 'Introduction to Objects II' (sadly I can't provide a link as you have to register and login to see it, but it is easy to find).
And yet, I noticed that my flag was marked as "disputed" by a moderator. Did the moderator make a mistake in this case, or is there a gray area here that I'm missing?