Node (NPM)

Introduction to NPM (Node Package Manager)

When you install Node.js, you get another incredibly powerful tool bundled with it for free: NPM, which stands for Node Package Manager.

NPM is the world's largest software registry. It contains over two million packages of pre-written JavaScript code that you can easily download and integrate into your own projects. Why reinvent the wheel when another developer has already written and tested the code you need?

1. What exactly is NPM?

NPM consists of three distinct parts:

1. The Website (npmjs.com): A search engine where developers discover packages, read documentation, and manage their profiles.
2. The Command Line Interface (CLI): The terminal tool that developers use to install, publish, and manage packages.
3. The Registry: A massive public database of JavaScript software and the metadata surrounding it.

To verify that you have NPM installed on your machine, run the following command in your terminal:

npm -v

2. Installing Packages Locally

By default, when you use NPM to install a package, it is installed locally. This means the package is only accessible to the specific project folder you are currently inside.

For example, if you want to create an API, you will likely need the popular web framework called express. You can download it into your project by typing:

npm install express

(Note: npm i express is a common shorthand for npm install express)

What happens when you run this?

1. NPM reaches out to the registry to find the express package.
2. It downloads the code into a magical new folder in your directory called node_modules.
3. It automatically creates or updates your package.json file to keep a record of the installation.

Once installed, you can require/import it in your files just like a core Node.js module!

// We can now use the express package!
const express = require('express');
const app = express();

console.log("Express was successfully loaded from node_modules!");

3. Installing Packages Globally

Some packages are not meant to be imported into your code. Instead, they are command-line tools that you want to be able to run from anywhere on your computer, regardless of the folder you are in.

To install a package globally, you add the -g flag to your install command.

For example, nodemon is a fantastic tool that automatically restarts your Node server whenever you save a file:

npm install -g nodemon

Now, instead of running node app.js, you can run nodemon app.js in any directory on your computer!

4. The node_modules Folder

If you open your project folder after running an npm install, you will see a node_modules directory. This folder contains all the source code for the packages you downloaded.