--description--

What is npm?

• Definition: npm is an online registry for open-source software, functioning like an "app store" for code.

• Official Meaning: npm does not officially stand for "Node Package Manager"; it is a recursive backronymic abbreviation for "npm is not an acronym".

• Three Related Parts:

  • Website (npmjs.com): For looking up packages in the registry.
  • Registry: A large public database storing all packages.
  • CLI (Command Line Interface): A tool installed with Node.js to manage project dependencies.

• Alternatives: While npm is most widely used, popular alternatives include Yarn, PNPM, and Bun.

The package.json File

• Purpose: A configuration file that stores metadata, dependencies, and scripts for a Node.js project.

• Key Fields:

  • name and version: Identify the project.
  • main: Specifies the entry point file, often index.js.
  • license: Defines legal terms (default is ISC).
  • dependencies: Packages required to run the app in production.
  • devDependencies: Tools only needed during development, such as testing frameworks.

• Creation:

  • npm init: Starts an interactive setup process.
  • npm init -y: Installs a package.json with default values instantly.

Semantic Versioning (SemVer)

• Format: MAJOR.MINOR.PATCH.

• Rules:

  • MAJOR: Breaking changes that can affect existing code.
  • MINOR: New features that are backwards compatible.
  • PATCH: Small bug fixes and improvements.

• Range Symbols:

  • ^ (Caret): Allows minor and patch updates (e.g., ^1.2.3 allows 1.x.x).
  • ~ (Tilde): Allows only patch updates (e.g., ~1.2.3 allows 1.2.x).
  • * (Asterisk): Matches any version; used primarily for testing.

Dependency Management

• Installation:

  • npm install <name>: Adds a production dependency.
  • npm install <name> -D: Adds a development dependency.
  • npm install <name>@<version>: Installs a specific version.

• Node Modules & Locks:

  • node_modules/: Contains the actual code for installed packages.
  • package-lock.json: Locks the exact versions of all dependencies and "child dependencies" to ensure consistency across environments.

• Removal: npm uninstall <name> removes the package and updates package.json.

• Maintenance:

  • npm outdated: Identifies which packages have newer versions available.
  • npm update: Updates packages within the allowed SemVer range.

npm Scripts

• Function: Custom commands defined in the scripts section of package.json to automate tasks.
• Execution: Run via npm run <script_name>.
• Shorthands exist for start, test, stop, and restart (e.g., npm start).
• Sequential Execution:
• &&: Runs the second command only if the first succeeds.
• ;: Runs commands one after another regardless of success.
• Concurrent Execution: Use the & operator to run processes in the background.
• Arguments: Pass arguments to scripts using the -- separator (e.g., npm start -- 8000).

Publishing to the npm Registry

• Registry Access: A database of public and private packages.
• Publication Steps:

1. Create a free account at npmjs.com.
2. Log in via terminal using npm login.
3. Ensure a unique name and valid version are in package.json.
4. Create a README.md and .npmignore (to exclude sensitive files).
5. Run npm publish (or npm publish --access public for scoped packages).

• Scopes: Used to avoid name conflicts by publishing under @username/package-name.

Module Systems in Node.js

CommonJS (CJS)

• Default System: The original way Node.js handles modules; loads synchronously.
• Syntax:
• Import: const module = require('./path').
• Export: module.exports = { functionName }.
• Identification: Used for .cjs files or .js files when no type is specified in package.json.

ES Modules (ESM)

• Standardized Format: Modern JavaScript standard; loads asynchronously for efficiency.

• Syntax:

  • Export: export { name } or export default function.
  • Import: import { name } from './path.mjs'.
  • Identification: Used for .mjs files or .js files when package.json contains "type": "module".

--assignment--

Review the npm topics and concepts.