Advantages of organizing dependencies using Node.js/npm

require and module.exports

For starters, the requires.js library has nothing to do with the require()node.js method . This method is a part of node itself, and is the backbone of how node resolves dependencies.

Suppose we make an application with two files: server.jsand herramientas.jslocated in the same folder. Where tools.js has functions that you want to import into server.js, the "main program". So, we have:

// herramientas.js
var exports = {};
module.exports = exports;

exports.sumar = function (a, b) { return a + b };

// server.js
var tools = require('./herramientas');
console.log(tools.sumar(2, 2));

// Resultado al ejecutar
4

This example serves to demonstrate that it require('./nombre_modulo')returns the object that was set in the variable module.exports of the named file nombre_modulo.js.

require()it is also used to import external packages (or modules), another issue in your question.

npm and package.json

npmis node's own tool to assist you during application development. This is why no IDE is needed to work with node, with a text editor it is enough thanks to the npm.

package.jsonis a file in json format (very obvious isn't it?) that contains the information of the package, including the dependencies, but also information about the version, the author and other things.

You can create it manually with your text editor and with the help of the documentation (try with npm help json) or you can use the command npm init, which will interactively request the basic data of your package. If you use this option, be sure to type server.jswhen prompted for the entry point.

dependencies

The command npm install <paquete>searches the node registry for the package (the registry is the official module database), if it exists, it downloads it along with all its direct and indirect dependencies and installs them into a folder in the local directory called node_modules.

The option --savemakes that after downloading the package, update the list of dependencies in package.json, which is very useful because it saves a step, but package.json must already exist in this step and if it does not exist, the option will have no effect. Another way to do the same thing would be to edit package.json, add the dependency and then call npm install.

The option -gindicates that the package should be installed globally instead of inside node_modules. This option is used to install development tools, such as bower, gulp, etc.

By installing globally, it allows commands to be added to your system console (eg npm install bower -ginstall a new system command called bower)

Lastly, external dependencies (those that are installed inside the folder node_modules) are imported using require('nombre_modulo'), meaning you should NOT include the ./.

execution and testing

After the application is built and the dependencies declared, npm startyou run your application. You can also declare unit tests for your module and launch them with npm test.

Unit test setup example:

"scripts": {
    "test": "<comando que hace la prueba>"
}

conclusions

As you can see, it npmhas many advantages. For example, it prevents you from having to manually download all the dependencies of a package, which as a project grows, becomes impractical/scalable. Also, if your package is a library that you are going to publish in the registry, you have the command npm publish <nombre_modulo>that publishes (or updates) your package on the internet so that anyone can use it... of course! through npm install <nombre_modulo>.

To extend @rnd's great answer, if you wanted to use NodeJs modules to be used from the client side, you can use browserify , that way you have the advantages of npm's dependency management on the browser side.