npm (Node Package Manager)

npm is the default package manager for Node.js and the world's largest registry of open source JavaScript packages. It installs libraries a project depends on, manages their versions and runs project scripts.

A project lists its dependencies and scripts in package.json; npm install downloads them into the node_modules folder, and package-lock.json records the exact versions installed so every machine gets the same ones. npm run <script> runs tasks such as build or test, and npx runs a package's command without installing it globally. Yarn and pnpm are popular alternatives.

npm init -y              # create package.json
npm install react        # add a dependency
npm install -D eslint    # add a dev dependency
npm run build            # run a script from package.json