Lecture 299:- User Sign In

To implement user sign in, we need to perform the following steps:

1. Create a form in the sign-in view that takes the user's email and password as input.
2. In the form action, specify the URL to which the form data should be submitted. For example, /users/signin.
3. In the server, create a new route that listens to POST requests on /users/signin.
4. In the server, define a controller function to handle the POST request to /users/signin.
5. In the controller function, extract the email and password from the request body.
6. Query the database to find a user with the given email.
7. If a user is found with the given email, check if the provided password matches the user's password.
8. If the password is correct, create a new session and store the user's ID in the session.
9. Redirect the user to the home page or some other authorized page.
10. If the email or password is incorrect, show an error message to the user.

Here's an example implementation of the POST request to /users/signin:

javascriptCopy code

// server.js const express = require('express'); const app = express(); const mongoose = require('mongoose'); const session = require('express-session'); const User = require('./models/User'); // Set up session middleware app.use(session({  secret: 'secret-key',  resave: false,  saveUninitialized: false })); // Set up body-parser middleware app.use(express.urlencoded({ extended: true })); // Connect to MongoDB mongoose.connect('mongodb://localhost/myapp', {  useNewUrlParser: true,  useUnifiedTopology: true,  useCreateIndex: true,  useFindAndModify: false }); // Define routes // GET request to /users/signin app.get('/users/signin', (req, res) => {  res.render('signin'); }); // POST request to /users/signin app.post('/users/signin', async (req, res) => {  const { email, password } = req.body;  // Find user by email  const user = await User.findOne({ email });  if (!user) {    // User not found    return res.render('signin', { error: 'Invalid email or password' });  }  // Check if password is correct  if (user.password !== password) {    // Incorrect password    return res.render('signin', { error: 'Invalid email or password' });  }  // Save user ID in session  req.session.userId = user._id;  // Redirect to home page  res.redirect('/'); }); // Start server app.listen(3000, () => {  console.log('Server started on port 3000'); });

In this example, we first extract the email and password from the req.body object. We then use User.findOne() to query the database for a user with the given email.

If a user is found, we check if the provided password matches the user's password. If the password is correct, we create a new session and store the user's ID in the session using req.session.userId.

If the email or password is incorrect, we render the signin view again with an error message.

Note that we're using async/await to handle the database query, which is an asynchronous operation. We're also using the express-session middleware to handle sessions, and we're setting the saveUninitialized option to false to prevent the middleware from creating empty sessions for every request.