Authentication is one of the big part of any application. JSON web token is one of the safest medium of transferring information between two parties. The token is a long encryped string that has 3 parts-

The headers  - It contains the header information

The paylod - It contains the actual information such the user json object and

The signature - It is a cryptographic signature

Usage:

jwt.sign(payload, secretOrPrivateKey, options, [callback])

payload:

{
    _id: "adnasdaasdjasdh",
    name: "dinesh rawat",
    email: "dinesh.rawat@evontech.com"
}

secretOrPrivateKey:

It could be anything that is used to make a hash
ex:-

"mysupersecretkey"

options:

algorithm (default: HS256)

expiresIn: expressed in seconds or a string describing a time span

notBefore: expressed in seconds or a string describing a time span

audience

issuer

jwtid

subject

noTimestamp

header

Example

// sign with default (HMAC SHA256)
var jwt = require('jsonwebtoken'); //Sign with HMAC SHA256
var token = jwt.sign({
                _id: "adnasdaasdjasdh",
                name: "dinesh rawat",
                email: "dinesh.rawat@evontech.com"
            }, "mysupersecretkey", { expiresIn : 60*60*24 });

console.log(token);

/*
RESULT:
-------

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJfaWQiOiI1Nzg3NTZlNTI3YjFjMGMzMzgyZWQ4ZWUiLCJlbWFpbCI6Imhhcm5lZXQiLCJ0b2tlbiI6IiIsImlhdCI6MTQ2ODU3NDQ3NiwiZXhwIjoxNDY4NjYwODc2fQ.tcvbLZIkLHWsKObtbDcpjHdGJoGnVtHinj8JAkRigpM

Decoding:
 

var decoded = jwt.decode(token);

// get the decoded payload and header
var decoded = jwt.decode(token, {complete: true});
console.log(decoded.header);
console.log(decoded.payload)

Checkout code from git:

https://github.com/dinesh-rawat/jwt-authentication.in.nodejs