Whenever I save app.js files in react it errors always comes up and unexpected token

class App extends Component {
    render() {
        return (

            const jwt = require('jsonwebtoken')

            app.use(express.json())

            const posts = [{
                username: 'Cr3',
                title: 'Post 1'
            }]

            const express = require('express')
            const app = express()

            app.get('/posts', (req, res) => {
                res.json(posts)
            })

            app.post('/login', (req, res) => {
                //Auth the user using tokens

                const username = req.body.username

                const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_SECRET)
                res.json({ accessToken: accessToken }) //Create access token

                const user = { name: username } //label name as username

            })

            app.listen(3000)

            <
            div id = "colorlib-page" >
            <
            div id = "container-wrap" >
            <
            Sidebar > < /Sidebar> <
            div id = "colorlib-main" >
            <
            Introduction > < /Introduction> <
            About > < /About> <
            Functions > < /Functions>

            <
            /div> < /
            div > <
            /div>


        );
    }
}



export default App;

This is the code, I have no idea why whenever It saves it just goes crazy and shows a bunch of errors, I tried to turning off automatic formatting as well as changing app.js to app.jsx which made it worse for a while, many times when I re-run my node.js server the errors seem to keep pointing at the const jwt stating unexpected token.