Let's Learn MongoDB

• MongoDB is a DataBase.
• There are 2 types of DataBase:
  1. Relational DB
     • MySQL
     • SQL
  2. Non-Relational DB
     • MongoDB

Diagram

Code Side	MongoDB Side
DB Setup	DB Formation
Model	Collection
Schema	Documents

Concept of MongoDB

• The Storage will have Containers of data of different apps.
• Every app will have it's own Container to store its data.
• Every Container is the DataBase of that one app or Project.

Example of the DataBase of Amazon.

• The DataBase of Amazon will consist for the following containers of data:
  • User DB
  • Products DB
  • Sales DB
  • Admins DB
  • & Many more.....
• One whole DataBase of Amazon is divided into different parts (i.e., variety of data) known as Model in coding & Collection in DataBase.
• We write code for Model, which makes Collection in DataBase.
  • For Example:
    • Product Model will be coded, which will create Product Collection in the DataBase.
    • User Model will be coded, which will create User Collection in the DataBase.
    • Sales Model will be coded, which will create Sales Collection in the DataBase.

Schemas in code will create Documents in DataBase.

• Schemas in code will create Documents in DataBase.

• The Data of all users is Collection.

• The Data of ONE user in any collection is Document.

Setup Steps for MongoDB

1. Install MongoDB

   • Download from:

   https://www.mongodb.com/try/download/community
   

2. Install MongooseJS

   npm i mongoose

3. Require & Setup Connection

   • Write this code in routes/users.js

   // require mongoose
   const mongoose = require("mongoose");
   
   // Set Connection between mongoose & mongoDB
   mongoose.connect("mongodb://127.0.0.1:27017/DBname");   // Use the name of your DB replacing "DBname". Whatever you wish to use as a name.
   
   // This url is your device's localhost. MongoDB (by default) runs on port 27017
   // Mongoose is connecting to the mongoDB running on the server at the LocalHost.

   • This creates database.

4. Make Schemas

   • Using Schemas you have tell, what will a document of the collection will look like.
   • Use the below code in routes/users.js

   // Creating Schemas
   
   const userschema = mongoose.Schema({
       username: String,
       name: String,
       age: Number
   })
   
   // name-of-value: Type-of-value

   • This tells, how every document will look. (Units of data)

5. Create Model

   // Creating Models
   
   mongoose.model("userData", userschema);    // "userData" is the name of collection created

   • It creates collection in DataBase.

6. Export the Model

   // Export Model
   
   module.exports = mongoose.model("user", userschema);

In the above example, prcticekaro is the database created. userData is a collection created inside the database. userschema defines the structure of data stored in every document of the collection.

Mongoose.js

Mongoose is a JavaScript object-oriented programming library that creates a connection between MongoDB and the Node.js JavaScript runtime environment.

CRUD - Create Read Update Delete

Create

import user.js in index.js to bring all the information about database, collections, schema.

// import users.js as userModel
const userModel = require("./users");

Create documents in index.js

router.get('/create', async function(req,res){
  await userModel.create({
    username: "ansh07",
    age: 20,
    name: "Ansh Singh Sonkhia"
  });
  res.send("Successfullllly Created")
  // This "userModel.create" is asynchronoud JS, So, will go into the side stack & will be implemented after the completion of main stack Synchronous code. That's why we use "await" before it.
  // nhi toh user ko pehle hi message chala jayega
});

• After Creation of this user, mongoDB will return the created user, which we can save.

router.get('/create', async function(req,res){
  const createduser = await userModel.create({
    username: "ansh07",
    age: 20,
    name: "Ansh Singh Sonkhia"
  });
  res.send("Successfullllly Created")
  res.send(createduser);
});

Read

router.get("/allusers", async function(req,res){
  let allusers = await userModel.find();
  res.send(allusers);
});

• .find is used to find
• .findOne is used to find one user

router.get("/allusers", async function(req,res){
  let allusers = await userModel.findOne({username: "harshita"});
  res.send(allusers);
});

Update

Delete

router.get("/delete", async function(req,res){
  let deleteduser = await userModel.findOneAndDelete({
    username: "harsh"
  });
  res.send(deleteduser);
});

Client-Server Diagram

Client	Server
Cookie	Session

• When you have to save data on server - use session.
• When you have to save data on Client's frontend' - use Cookie.

---

• Data saved in the server is more secured than the data saved in the client's cookie.

Sessions

• To use sessions - install this package:

npm i express-session

• Write this code in app.js

var session = require('express-session');

app.use(session({
  resave: false,  // don't save again, if the value of session is NOT changed.
  saveUninitialized: false,   // Don't save any data, which is NOT named.
  secret: "kuchBhiRandomSecretCodeLikhDoo"    // A secret string, on the basis of which our data will be encrypt.
}));

• You can create session in the routes with any name of your choice, whenever someone visits that route.

router.get("/", function (req, res) {
  req.session.anyname = "heloo";
  res.render("index");
});

Example Use-Case

• So, if you want anyone to get banned, when he visits any route...

router.get("/", function (req, res) {
  req.session.banned = true;
  res.render("index");
});

You can use any name for session - banned, ban, noban, lemon, bmw, etc....

If a session is created in any route, it can be checked in all other routes.

router.get("/check-ban", function (req, res) {
  console.log(req.session);
  res.send("You have beeeeeeeeeeen Banned");

  if(req.session.banned === true){
    res.send("You have beeeeeeeeeeen Banned");
  }
  else{
    res.send("not banned");
  }
});

If the server is restarted...

If the server is restarted or restarted by nodemon Then, the session will be deleted.

How to delete session?

router.get("/remove-ban", function (req, res) {
  req.session.destroy(function(err){
    if (err) throw err;
    //console.log(err);
    res.send("Ban Removed Successfullyy")
  })
});

Cookie

• install package cookie-parser

• use code:

var cookieParser = require('cookie-parser');
app.use(cookieParser());

How to use Cookie

Cookie is set on the frontend. So, sent in response

router.get("/", function (req, res) {
  res.cookie("age", 25);	// cookie("cookie-name", cookie-value)
  res.render("index");
});

How to read Cookie?

• The cookie is set on the browser of client.
• And, we have to read it on server.
• So, we have to request it.

router.get("/read", function (req, res) {
	console.log(req.cookies);
	console.log(req.cookies.age);	// to get direct data of cookie named "age"
	res.send("check");
});

How to delete Cookie?

router.get("/delete", function (req, res) {
	res.clearCookie("age");
	res.send("Cookie Cleared Successfullyy");
});

EndGame-1 Completed