Node Package Manager (NPM)

🔷 What is NPM?

NPM (Node Package Manager) is the default package manager for Node.js. It allows developers to:

• Install libraries/packages (also called modules).
• Share their own packages with others.
• Manage project dependencies.
• Run project-related scripts (like start, test, build).

📌 NPM is the world’s largest software registry – with over 1.5 million packages!

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🔷 Why Use NPM?

• 📥 Install ready-to-use open-source libraries.
• 🔧 Manage and track dependencies in your project.
• 🧪 Run custom scripts like testing, deployment, etc.
• ♻️ Use version control for packages.
• 🧑‍💻 Publish your own packages to the npm registry.

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🔷 Installing and Using NPM

NPM is automatically installed when you install Node.js.

🔍 Check version:

npm -v

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🔷 Working with NPM – Common Commands

Command	Description
npm init	Initializes a Node.js project and creates package.json
npm install <package-name>	Installs a package locally
npm install -g <package>	Installs a package globally
npm uninstall <package>	Uninstalls a package
npm update	Updates all packages
npm list	Lists all installed packages

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🔷 Key Files in NPM Projects

📁 1. package.json

The heart of any Node.js project. It stores metadata about your project and its dependencies.

Example:

{
  "name": "student-app",
  "version": "1.0.0",
  "scripts": {
    "start": "node app.js"
  },
  "dependencies": {
    "express": "^4.18.2"
  }
}

📁 2. package-lock.json

• Automatically generated when npm install runs.
• Locks the version of installed packages to ensure consistent builds.

📁 3. node_modules/

• Folder where all installed dependencies are stored.
• Should not be manually edited.
• Usually ignored in .gitignore.

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🔷 Installing Packages – Examples

✅ Local Installation:

npm install express

This creates:

• node_modules/express/
• Adds entry in dependencies section of package.json

✅ Global Installation:

npm install -g nodemon

Used for tools you want accessible from the command line across projects.

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🔷 Dev Dependencies vs Dependencies

Type	Description	Installed With
dependencies	Packages needed to run your app	npm install
devDependencies	Packages needed only during development/testing	npm install --save-dev

Example:

npm install jest --save-dev

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🔷 Using Scripts in NPM

In package.json, you can define shortcuts for tasks:

"scripts": {
  "start": "node app.js",
  "test": "echo 'Testing...'"
}

Run:

npm start
npm test

You can also add:

npm run build
npm run dev


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🔷 Creating and Publishing Your Own Package (Intro Level)

1. Initialize: bashCopyEditnpm init
2. Write your package logic.
3. Login: bashCopyEditnpm login
4. Publish: bashCopyEditnpm publish

📝 Your package is now available for anyone to install via npm install your-package-name.

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🔷 Real-World Popular NPM Packages

Package Name	Description
express	Web framework for Node.js
mongoose	MongoDB object modeling
cors	Enable CORS in APIs
nodemon	Automatically restarts server on changes
axios	HTTP requests from Node or browser
dotenv	Manage environment variables
jsonwebtoken	Used for JWT-based authentication

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🔷 Benefits of Using NPM in Development

✅ Fast and efficient project setup
✅ Access to the largest module library
✅ Consistent dependency management
✅ Easy collaboration and version control
✅ Active community and frequent updates

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📚 Suggested Practical Activities

1. Create a new project with NPM
   • Use npm init, install some dependencies.
2. Build a REST API using Express
   • Use npm install express
3. Use nodemon for auto-restart
   • Install as dev dependency
4. Write a script in package.json to run your app
5. Explore and install packages from https://www.npmjs.com

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🔚 Conclusion

🔑 NPM is not just a tool — it’s a core part of the Node.js development lifecycle.
Mastering NPM is crucial for every modern backend developer, and especially important for MCA students to build real-world, scalable, and efficient applications.