Json Web token

A JSON Web Token, or JWT, is used to send information that can be verified and trusted by means of a digital signature. It comprises a compact and URL-safe JSON object, which is cryptographically signed to verify its authenticity, and which can also be encrypted if the payload contains sensitive information.

JWTs can be signed using a secret (with the HMAC algorithm) or a public/private key pair using RSA.

Because of it’s compact structure, JWT is usually used in HTTP Authorizationheaders or URL query parameters.

NODE - NPM

Node Doc

Installation:
Head to the Node.js download page and grab the version you need. There are Windows and Mac installers available, as well as pre-compiled Linux binaries and source code. For Linux, you can also install Node via the package manager, as is outlined here.
open command prompt ,check version installed
node -v
npm -v

Basic npm command -
npm init => initializes package.json
npm list -g  => list all global npm packages installed
npm list => list all npm packages installed
npm install <package-name> => install package to local
npm install -g <package-name> => install package globally on the system
npm update <package-name> => updates packages name