NPM is a package manager for Node.js. It maintains a registry of modules published by developers around the world.
NPM comes packaged with recent Node.js distributions. If you need to manually install NPM, use this one-liner:
curl http://npmjs.org/install.sh | sh
.
package.json and other goodies.
npm link
"scripts": { "test": "...", "start": "..." }
References: