One of the most powerful aspects of Node.js is its module system, which allows you to split your code into smaller, reusable files. Additionally, with the use of npm (Node Package Manager), you can access thousands of packages that extend Node.js functionalities, simplifying the development of complex applications.

What are modules?

In Node.js, a module is simply a file that contains code. Every file in Node.js is a module, and you can use the module system to export functionalities from a file and utilize them in others.

For example, we can create a module that exports a greeting function and then use that module in another file.

Creating a Basic Module

Create a file named greet.js with the following content:

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Now, in a separate file, for example app.js, we can import and use this function:

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When you run app.js, you should see the following result in the terminal:

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Working with Packages

Node.js includes npm, a package manager that allows you to install and share modules with other developers. npm is the world's largest package ecosystem, with thousands of packages available for you to use in your projects.

Installing a Package Using npm

Let's install the lodash package, a popular utility library that makes working with arrays, objects, and other data structures easier.

First, initialize a new Node.js project by running the following command in the terminal:

bash

Then, install the lodash package with the following command:

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Using an Installed Package

Once the package is installed, we can require it in our project like any other module:

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When you run this code, you should see something like this:

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package.json and Dependency Management

The package.json file is where npm stores all the information about your project, including the dependencies you've installed. Every time you install a package, npm adds it to this file automatically.

Here's an example of a package.json file after installing lodash:

json

Summary

In this chapter, we have learned how modules allow us to organize our code and how npm facilitates access to thousands of useful packages. This gives us the necessary tools to build complex and scalable applications in Node.js more efficiently.