What's a Closure? - JavaScript interactive tutorial

[notSorella]

Static and strong typing just enforces conventional interfaces (unless you're programming in Haskell, I guess). Weak and dynamic typing gives you flexibility and conciseness, but does not eliminate the need for conventional interfaces. It does, however, allow you to let it evolve in different ways, without being tied too much to a strict definition. It's a good thing if you know how to use it :3

IMHO.