5. How the module system, CommonJS & require works.txt

How the module system, CommonJS & require works:
------------------------------------------------

* JS didn't have a way to organize code.
* Node.js filled this gap with the CommonJS module format.


Modules:
-------

* Modules are the fundamental building blocks of the code structure.
* The module system allows you to organize your code, hide information and only expose the public interface of a component using module.exports.
* Every time you use the "require" call, you are loading another module.

Example:
--------

(function (exports, require, module, __filename, __dirname) {
  function add (a, b) {
    return a + b
  }

  module.exports = add
});


How does require work?:
----------------------
*  Caching the modules on the first "require" call


Require under the Hood:
-----------------------

    * Module loading is done using module.js in lib/module.js
    * Two important functions
         __load  - checks whether module is cached,if so returns it.
         __compile - Runs the file contents in the correct scope and exposes helper variables like exports,module or require to the file.


What’s in your node_modules?
----------------------------

    - The node_modules folder is the place where Node.js looks for modules