Modules

When you are writing a lot of code, you soon reach a point where you have to start thinking about how you want to organize the code. Node modules are CommonJS modules that we discussed earlier when we discussed module patterns. Node modules can be published to the Node Package Manager (npm) repository. The npm repository is an online collection of Node modules.

Creating modules

Node modules can be either single files or directories containing one or more files. It's usually a good idea to create a separate module directory. The file in the module directory that will be evaluated is normally named index.js. A module directory can look as follows:

node_project/src/nav
                --- >index.js

In your project directory, the nav module directory contains the module code. Conventionally, your module code needs to reside in the index.js file—you can change this to another file if you want. Consider this trivial module called geo.js:

exports.area = function (r) {
  return 3.14 * r *...