Modules provide a way to encapsulate your code and create privacy. In object-oriented languages, we usually use classes for this. However, I actually believe that this is an anti-pattern rather than a good practice. Classes should be used where inheritance is desired and not just to structure your code.
I'm sure that you've encountered a lot of different module patterns in JavaScript already. One of the most popular ones that creates privacy using a function closure of an immediately invoked function expression (IIFE) is probably the revealing module pattern. If you'd like to read more about this and maybe other great patterns, I recommend the book Learning JavaScript Design Patterns, by Addy Osmani.
Within ECMAScript 6, we can now ...
