How to check session in angular 8 - node.js

Question

I have created login form with angular 8 and node js. I have set the session using node js in back end. i couldnt check session set or not in angular for avoid access dashboard without logged in. Kindly suggest the way to use login system using angular 8 and node js. Thanks.....

Answer 1

A very popular method is to use JWT (JSON Web Tokens) npm package to authenticate.
The process would be:
Send credentials to the server
Server generates and sends back JWT or a Bearer Token
FrontEnd would store it in browser cookies or localStorage
localStorage.setItem('TOKEN', tokenReceivedFromServer);
In subsequent Api Calls the token would be sent to the server in a Header (Authorization).
Authorization: `JWT ${localStorage.getItem('TOKEN')}`
FYI: JWT keyword is removed from string on the server before parsing token
The frontend can check if the token is set in storage to show login page / dashboard

Answer 2

First we need to check the login credentials valid or not in application.
In angular application component typescript file, we have send the data service in argument, the service send the values to backend using httpclient. If credentials valid we set the value in localstorage.
submitLogin(data:any)
{
this.LoginService.loginData(data).subscribe(data =>{
if(data.body.status_code == 404)
{
Swal.fire({
icon: 'warning',
title: 'Invalid E-Mail/Password!',
}).then(function(){
});
}else if(data.body.status_code ==200)
{
localStorage.setItem("user_id",data.body.token);
this.router.navigate(['/Dashboard']);
}else
{
Swal.fire({
icon: 'error',
title: 'Process Failed!',
}).then(function(){
});
}
});
}
In service.ts file make sure about those packages import
import { HttpClient } from '#angular/common/http';
import { Observable, throwError } from 'rxjs';
import {Login} from './login';
in loginData function
url = "http://localhost:3000/loginCheck";
loginData(Login:Login):Observable<any>
{
return this.http.post(this.url,Login,{observe: 'response'});
}
in backend i have used node.js
in file app.js
first install jsonwebtoken package and include in the file.
npm install jsonwebtoken
then set the jsonwebtoken when where condition satisfies
let payload = {subject:employee_id}
let token = jwt.sign(payload,'secretKey')
var response = {
'token': token,
"status_code":200,
}
res.send(response);
res.end();
Whenever we use the login in angular we must use the authguard routing its helps to access dashboard without logged in.
ng generate guard auth
in auth.guard.ts file we must include the package and service
import { CanActivate, Router } from '#angular/router';
import {LoginService} from './login.service';
export class AuthGuard implements CanActivate {
constructor(private LoginService:LoginService,private router:Router) {}
canActivate(): boolean
{
if(this.LoginService.loggedIn())
{
return true
}else
{
this.router.navigate(['/login']);
return false;
}
}
}
In this file we just checking the localstorage value set or not in boolean datatype.
in service file
add the following code for get and return in boolean type
loggedIn()
{
return !!localStorage.getItem('user_id')
}
getToken()
{
return localStorage.getItem('user_id')
}
if its returns true we can access the dasboard, else its redirected to login page.
We must use this canActive function in routing otherwise it will not working
In app-routing.module.ts file
import { AuthGuard } from './auth.guard';
const routes: Routes = [
{path:'Dashboard',component:DashboardComponent},
{path:'receipt',component:ReciptComponentComponent,canActivate:[AuthGuard]},
];
It will helpus to access dashboard without loggedin but we need to check the token valid or not in backend, we can do that using angular interceptors
we should create the new service with interceptors name
ng g service token-interceptor
In interceptor file we need to import the following
import { Injectable,Injector } from '#angular/core';
import { HttpInterceptor } from '#angular/common/http';
import { LoginService } from './login.service';
In interceptors services inject in different way compared to component.
export class TokenInterceptorService implements HttpInterceptor{
constructor(private Injector:Injector) { }
intercept(req:any,next:any)
{
let loginService = this.Injector.get(LoginService);
let tokenzedReq = req.clone({
setHeaders:
{
Authorization: `Bearer ${loginService.getToken()}`
}
});
return next.handle(tokenzedReq)
}
}
we need to create a function in interceptors with the name intercept, then we need to inject the service as per injector.
In backend we need to create the helper function to verify the jsonwebtoken
if the authorization not set we can send the response 401 not found and can redirected to login page
function verifyToken(req,res,next)
{
if(!req.headers.authorization)
{
return res.status(401).send('Unauthorized request');
}
var token = req.headers.authorization.split(' ')[1];
if(!token)
{
return res.status(401).send('Unauthorized request');
}
if(token === 'null')
{
return res.status(401).send('Unauthorized request');
}
//let payload = jwt.verify(token,'secretKey');
let payload = jwt.decode(token,'secretKey');
if(!payload)
{
return res.status(401).send('Unauthorized request');
}
req.userId = payload.subject;
next();
}
then we can use this middleware function wherever we need
for example
app.get('/dashboard',verifyToken,function(req,res){
let events = [];
res.json(events);
});
In dashboard component ts file
this.dashboardService.getData().subscribe(data=>this.dashboardData=data,
err=>{
if(err instanceof HttpErrorResponse)
{
if(err.status===401)
{
this.router.navigate(['/login']);
}
}
})
in dashboard service ts file
url = "http://localhost:3000/dashboard";
getData()
{
return this.http.get<any>(this.url);
}
in app.module.ts file
import { AuthGuard } from './auth.guard';
import { ReciptComponentComponent } from './recipt-component/recipt-component.component';
import { HttpClientModule, HTTP_INTERCEPTORS } from '#angular/common/http';
import { TokenInterceptorService } from './token-interceptor.service';
import { DashboardServiceService } from './dashboard-service.service';
in providers
providers: [AuthGuard,{provide:HTTP_INTERCEPTORS,useClass:TokenInterceptorService,multi:true},DashboardServiceService],