Example of implementing a JWT token (login page) using node.js, express and Angular. You'll need the proxy.conf.json to run Angular and node in the same machine (to be able to access /api/login). Use ng serve --proxy-config proxy.conf.json -o.

auth.service.ts

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { shareReplay, tap, catchError } from 'rxjs/operators';
import * as moment from "moment";

import { User } from './User';

@Injectable({
  providedIn: 'root'
})
export class AuthService {
  constructor(private http: HttpClient) {
  }

  login(user: User) {
    if (user.name !== '' && user.password !== '') {
      //Verify if response is valid ???
      return this.http.post<User>('/api/login', user)
        .pipe(
          tap(this.setSession),
          shareReplay()
        );
    }
  }

  logout() {
    localStorage.removeItem("token");
    localStorage.removeItem("expires_at");
  }

  public isLoggedIn() {
    return moment().isBefore(this.getExpiration());
  }

  isLoggedOut() {
    return !this.isLoggedIn();
  }

  getExpiration() {
    const expiration = localStorage.getItem("expires_at");
    const expiresAt = JSON.parse(expiration);
    return moment(expiresAt);
  }

  private setSession(authResult) {
    const expiresAt = moment().add(authResult.expiresIn, 'second');

    localStorage.setItem('token', authResult.token);
    localStorage.setItem('expires_at', JSON.stringify(expiresAt.valueOf()));
  }
}

index.js

const express = require('express');
const fs = require('fs');

var _ = require("lodash");
var bodyParser = require("body-parser");
var jwt = require("jsonwebtoken");

var expressJwt = require('express-jwt');

var users = [
  {
    id: 1,
    name: 'jonathanmh',
    password: '%2yx4'
  },
  {
    id: 2,
    name: 'test',
    password: 'test'
  }
];

var privateKey = fs.readFileSync('./private.key', 'utf8');
var publicKey = fs.readFileSync('./public.key', 'utf8');

const checkIfAuthenticated = expressJwt({
  secret: publicKey
});

var signOptions = {
  expiresIn: "30d",
  algorithm: 'RS256'
};

// Express

const app = express();

//parse usual forms
app.use(bodyParser.urlencoded({
  extended: true
}));

//parse json for APIs
app.use(bodyParser.json());

app.get('/api', (req, res) => {
  res.send({ hi: 'there' });
});

app.post('/api/login', function (req, res) {
  if (req.body.name && req.body.password) {
    var name = req.body.name;
  }

  var user = users[_.findIndex(users, { name: name })];

  if (!user) {
    res.status(401).json({ message: 'no such user found' });
  }

  if (user.password === req.body.password) {
    var payload = { id: user.id };
    var token = jwt.sign(payload, privateKey, signOptions);
    res.json({
      message: 'ok',
      token: token,
      expiresIn: jwt.decode(token).exp
    });
  } else {
    res.status(401).json({ message: 'password did not match' });
  }
});

app.route('/api/secret')
  .get(checkIfAuthenticated, function (req, res) {
    res.json({ message: "Success! You can not see this without a token" });
  })

const PORT = process.env.PORT || 5000;

app.listen(PORT, function () {
  console.log("Express running")
});

proxy.conf.json

{
  "/api/*": {
    "target": "http://localhost:5000",
    "secure": false,
    "logLevel": "debug",
    "changeOrigin": true
  }
}

How we can create private.key and public.key on windows, what does it would hold basically?

@jsbimra: You could use a site like csfieldguide to create both the public and the private keys. Just copy-paste them using your favorite (Windows)-editor. Those files would hold the public and private keys of the asymmetric encryption that is being used.