require.js

//greet.js
var greet = function() {
  console.log('Hello!');
};
module.exports = greet;

//app.js
var greet = require('./greet'); 
greet();

/**
- The require function takes the path of the greet module as a parameter
- The greet function is then wrapped inside another function
- Wrapping our module code protects variables and functions defined inside our module
- Thus module.exports becomes the way in which we expose our module

The newly wrapped greet module then becomes... 

(function (exports, require, module, __filename, __dirname) {

  var greet = function() {
    console.log('Hello!');
  };
  module.exports = greet;

});

- Then Node invokes the wrapped function by passing 4 parameters

fn(module.exports, require, moule, filename, dirname);

- Then require returns module.exports (which we have set inside our module file)
**/