Install jsonwebtoken

    npm i jsonwebtoken

Implement JWT Token

    const express = require('express')
    const jwt = require('jsonwebtoken')
    const TOKEN_SECRET = "7bc78545b1a3923cc1e1e19523fd5c3f20b409509";//process.env.ACCESS_TOKEN_SECRET;
    const app = express()
    const port = 3000

    function authenticateToken(req, res, next) {
        // Gather the jwt access token from the request header
        const authHeader = req.headers['authorization']
        const token = authHeader && authHeader.split(' ')[1]
        if (token == null) return res.sendStatus(401) // if there isn't any token
    
        jwt.verify(token, TOKEN_SECRET, (err, user) => {
        console.log(err)
        if (err) return res.sendStatus(403)
        req.user = user
        next() // pass the execution off to whatever request the client intended
        })
    }

    function generateAccessToken(username) {
        // expires after 60 mins (3600 seconds = 60 minutes)
        return jwt.sign({data:username}, TOKEN_SECRET, { expiresIn: 60*60 });
    }

    // login?username=naresh@gmail.com
    app.get('/login', (req, res) => {

        let username = req.query.username;
        console.log(username);
        let token = generateAccessToken(username)
        console.log(token);
        res.json({token:token})
    });

    // Pass Bearer Token
    app.post('/updateuser',authenticateToken, (req, res) => res.send('Success!'))



    app.listen(port, () => console.log(`Example app listening on port port!`))

Test Login API

• http://localhost:3000/login?username=naresh@gmail.com

• It will return token string

Test Update User API

• http://localhost:3000/updateuser ( POST )

• Pass Bearer Token : token in Postman tool