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NPM & Package Management

  • NPM is the default package manager for Node.js used to install, manage, and share project dependencies. This content explains how npm works, the difference between local and global packages, and the role of package.json and package-lock.json in dependency management.

  • 🔹 NPM & Package Management

    Modern Node.js development is not done alone.
     Developers use ready-made code written by others to save time and effort.
     This is possible because of NPM (Node Package Manager).

    In this chapter, we will learn:

    • What npm is

    • How to install packages (local & global)

    • What package.json is

    • What package-lock.json is

    What is npm?

    The Package Manager of Node.js

    npm stands for Node Package Manager.
     It is a tool that comes automatically installed with Node.js.

    npm helps you:

    • Download libraries (packages)

    • Manage project dependencies

    • Share your own packages with others

    Simple Explanation

    Think of npm as an App Store for developers.

    Just like:

    • Play Store installs apps

    • npm installs code libraries

    Instead of installing apps, npm installs JavaScript packages.

    What is a Package?

    A package is a folder of reusable code that solves a specific problem.

    Examples:

    • Handling dates

    • Validating forms

    • Creating servers

    • Connecting databases

    Installing Packages

    Local & Global Installation

    npm allows installing packages in two different ways:

    • Local installation

    • Global installation

    Each has a different purpose.

    Local Packages

    (Local = project-specific)

    Local packages are installed inside a project folder.
     They are used only for that project.

    Example use cases:

    • Express

    • Mongoose

    • Axios

    These packages are saved inside:

Node Modules & npm Essentials

This section covers Node.js project dependencies and package management. It explains the node_modules/ folder, what npm is, how to install packages locally or globally, and the purpose of package.json and package-lock.json files in managing project libraries efficiently. 

node_modules/

  • Global Packages

    (Global = system-wide)

    Global packages are installed once and can be used anywhere on your system.

    Example use cases:

    • npm itself

    • nodemon

    • create-react-app

    When to Use What?

    • Use local packages for project features

    • Use global packages for tools & commands

    🔹 package.json

    The Heart of a Node.js Project

    Every Node.js project has a file called package.json.
     This file acts as the identity card of the project.

    What is package.json?

    It is a JSON file that stores:

    • Project name & version

    • Installed dependencies

    • Scripts to run the project

    • Project metadata

    Why is package.json Important?

    Imagine sending your project to another developer.
     Instead of sending the full node_modules folder, you send only:

Importance of package.json

The package.json file lists all the dependencies and project details. When sharing a Node.js project, instead of sending the entire node_modules/ folder, you can just share package.json, allowing others to install all required packages easily using npm install. 

package.json

  • They can reinstall everything easily.

    What package.json Contains

    • Project information

    • Dependency list

    • Custom scripts (start, dev, test)

    🔹 package-lock.json

    Ensuring Consistency Across Systems

    While package.json tells what to install,
     package-lock.json tells exactly which version was installed.

    Why package-lock.json Exists

    Different versions of a package may behave differently.
     This file ensures:

    • Same package versions

    • Same dependency tree

    • Same behavior on all machines

    Simple Explanation

    Think of:

    • package.json as a shopping list

    • package-lock.json as the exact bill with item versions

    Both work together to keep the project stable.

    When is package-lock.json Created?

    • Automatically generated by npm

    • Updated whenever packages are installed or updated

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