app.js

const express = require('express');
const jwt = require('jsonwebtoken');
const app = express();

app.get('/api', (req, res) => {
    res.json({
      message: 'Welcome to the API'
    });
  });

  app.post('/api/posts',verifyToken,(req,res) =>{
    jwt.verify(req.token, 'etkeysecr', (err, authData) => {
        if(err) {
          res.sendStatus(403);
        } else {
          res.json({
            message: 'Post created...',
            authData
          });
        }
      });
  });

  app.post('/api/login',(req,res) =>{
      const user = {
          id: 1,
          username:'Sam',
          email:"example@gmail.com"
      }
      jwt.sign({user: user},'secretkey',{expiresIn: '10h'},(err,token) =>{
          res.json({
              token
          });
      });
  });

  //Verify token
  function verifyToken(req,res,next){
      const bearerHeader =  req.headers['authorization'];
      if(typeof bearerHeader !== 'undefined'){
        // Split at the space
    const bearer = bearerHeader.split(' ');
    // Get token from array
    const bearerToken = bearer[1];
    // Set the token
    req.token = bearerToken;
    // Next middleware
    next();
      }else{
          //forbidden
          res.sendStatus(403)
      }
  };

  app.listen(5000, () => console.log('Server started on port 5000'));