Once user sign up, we store the user data inside cookie in the broswer and also keep a memory copy in the server. 

 

If next time, user refresh the page, we want to tell that the user is already authed.

 

Create a endpoint, to retrive the user data:

app.route('/api/user')  .get(getUser);

 

Router:

import {Request, Response} from 'express';import {sessionStore} from './session-store';export function getUser(req: Request, res: Response) {  // Get sessionid from cookies  const sessionId = req.cookies['SESSIONID'];  // get user according to the session id from the session storage  const user = sessionStore.findUserBySessionId(sessionId);  if (user) {    // if there is user, send successful response    res.status(200).json(user);  } else {    // if there is no user, send empty response    res.sendStatus(204);  }}

 

SessionStorage:

import {Session} from './session';import {User} from '../src/app/model/user';class SessionStore {  private sessions: {[key: string]: Session} = {};  createSession(sessionId: string, user: User) {    this.sessions[sessionId] = new Session(sessionId, user);  }  findUserBySessionId(sessionId: string): User | undefined {    const session = this.sessions[sessionId];    const isSessionValid = session && session.isValid();    return isSessionValid ? session.user : undefined;  }}// We want only global singletonexport const sessionStore = new SessionStore();

 

On the client, once page loaded, we try to get user data first.

import { Injectable } from '@angular/core';import {HttpClient} from '@angular/common/http';import {Observable} from 'rxjs/Observable';import {User} from '../model/user';import {BehaviorSubject} from 'rxjs/BehaviorSubject';import 'rxjs/add/operator/map';import 'rxjs/add/operator/shareReplay';import 'rxjs/add/operator/filter';import 'rxjs/add/operator/do';export const ANONYMOUS_USER: User = {  id: undefined,  email: ''};@Injectable()export class AuthService {  subject = new BehaviorSubject
     
      (undefined);  // filter out undefined user  user$: Observable
      
        = this.subject.asObservable().filter(user => !!user);  isLoggedIn$: Observable
       
         = this.user$.map(user => !!user.id);  isLoggedOut$: Observable
        
          = this.isLoggedIn$.map(isLoggedIn => !isLoggedIn);  constructor(private http: HttpClient) {    this.http.get
         
          ('/api/user')      // when there is valid session id, emit the user$      .subscribe((user) => this.subject.next(user ? user : ANONYMOUS_USER));  }  signUp(email: string, password: string) {    return this.http.post
          
           ('/api/signup', { email, password }).shareReplay() .do((user) => this.subject.next(user)); }}