******** Part 1:-Handling registration part. *******

Step 1:-

• First, install express-generator and nodemon packages globally into your system.

npm i --global express-generatornpm i --global nodemon

“Express-generator”:- this will help you setup basic server

“nodemon”:- this will restart your server automatically after you save changes.

• Now, we can set up a basic express server by just typing:-

express --view=ejs --css=sass <ProjName>

• Now, for creating Models to store data in MongoDB we have to install the “mongoose ”package.

npm i mongoose --save

Step 2:-

• Now, we have to create a User model to store data inside MongoDB. we have to create a new folder named “models” at the root. Once done, we have to create a new “User.js” file inside folder /root/models/ .
• We can set up our model according to our needs refer to the image for more details.

Step3:-

• Now, we have to connect the MongoDB database to our server. so, first import mongoose into app.js file and before we initialize variable app write following code.

mongoose.connect('mongodb://localhost:27017/regis',{ useNewUrlParser: true, useUnifiedTopology: true },(err) => {console.log(err ? err : ' connection true');});

• it will look like this:-

Step 4:-

• now we have to add SignIn and Register links to our index page (root/views/index.ejs). which will help users to navigate to respective pages.

<a class="btn btn-pri" href="/users/login">Login</a><a class="btn btn-pri" href="/users/register">Register</a>

• value of href attribute of login button has to be “/users/login” .
• similarly, for register button href= “/users/register”.

Step 5:-

• Now, we have to handle routes of “/users” inside the users.js file which is inside folder “/root/routes”.
• the Register button on the index page will do a GET request on /users/register route.
• so to handle GET request on /users/register route we can send response as the userRegistrationForm.ejs file to the browser. this fill will contain a From inside it which has action= “/users/register” method= “POST”

tip:- all ejs files have to be into views folder ie(root/views/userRegistrationForm.ejs).

• the userRegistrationForm.ejs file will look like this.

Step 6:-

• Once we fill the form and submit it, it will do a POST request on route “/users/register”.
• now to add data into the database we need to import the User model. so into the users.js file inside routes folder. at the top, we have to require a User model.

let User = require('../models/User');

• Now we can store form data inside “req.body” new variable data.
• Now to add user into the database we can use User.create() method of mongoose.
• once the user is created successfully we can redirect to “/users/login” route.

Step 7:-

**** encrypting(Hashing) password ****

• until now we have stored password entered by the user as it is inside the database. this makes our passwords easily accessible by other peoples.
• That's why we need to encrypt passwords while storing them in the database.
• for Hashing (encrypting) password we need to install “bcrypt ”package into our server.

npm i bcrypt --save

• now for encrypting password while registering new users we have to use mongoose middleware (hook) like pre(save).
• every time User schema is called ,first it will executes pre hook and later do its work.
• so to encrypt the password we have to use bcrypt.hash() method inside pre(save) hook.
• in this hook, we have to change the password inside “req.body” to the hashed password.

tip:- we have to write pre(save) hook before we create model.

********* Part 2: Handling login Part. *********

Step 1:-

• The Login button on index.ejs page will do GET request on route “/users/login”.
• to handle this GET request on “/users/login” route we have to just render “userLoginForm.ejs” page in response.

Step 2:-

• “userLoginForm.ejs” file must contain a simple login form with fields email and password.
• this form must have attribute ( action= “/users/login” method= “POST”)
• the “userLoginForm.ejs” file will look like this.

Step 3:-

• Now to handle POST request on route “/users/login”, we have to first extract email and password from formData inside req.body.
• on following 3 conditions server must be redirected back to “/users/login”.

1. when email and password is empty.
2. When email does not match with users in database.
3. When password does not match with existing password in database.

• Here we have to use User.findOne() method of mongoose to find user in database.
• write respective cases mentioned above to handle errors.

Step 4:-

• Remenber we have stored Hashed(encrypted) password into database but we have normal password now to match with hashed.
• this problem can be solved using “bcrypt.compare()” method of the bcrypt package.
• But first, we have to write the method inside the User model to check if passwords match. that we can do by defining method inside model by using

userSchema.methods.name=function(){};

Step 5:-

• Now inside users.js file to handle routes we can use this checkPassword() method to check if the password matches or not.
• Finally, the route handler must look like this:-

• This will return the “login Successful ” message as a response if the email and password match otherwise will redirect to the login page again.