Finally I figured out the solution to this : COOKIES. The more experienced web developers might say "So, what? Big deal??" but for novice users, for this problem you should consider using cookies. Cookies is what you use to store and share small values.
Refer to this wonderful tutorial on cookies: http://www.sitepoint.com/eat-those-cookies-with-jquery/
and a relevant SO post: jquery save json data object in cookie
To show Javascript Variable Value: Use the value as tooltip for a link element.
To modify Javascript Variable Value: Clicking on a link element can call javascript prompt, where the user can enter new values
To store Javascript Variable Value: Store the value in the cookie
To share among other pages: While storing the cookie use {path:"/"}
Also note that maximum size for cookie can be only 4kb. So, store your data wisely.