Express Js Basic Installations

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 Here’s a guide for Day 1 of your Node.js learning journey, covering the installation and basics of Express, setting up an MVC architecture, installing and configuring Nodemon, and using Postman for testing basic `GET` and `POST` operations.

 1. Install Node.js

Before starting, ensure you have Node.js installed on your machine. If not, download and install it from [Node.js official website](https://nodejs.org/).

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 2. Express Installation

1. Create a new project directory:

   mkdir my-express-app
   cd my-express-app

2. Initialize a new Node.js project:

   npm init -y

3. Install Express:

   npm install express

---

 3. MVC Architecture Concept

MVC stands for Model-View-Controller. It’s a design pattern used to separate the concerns of your application:

- Model: Manages the data and business logic.

- View: Handles what the user sees (UI).

- Controller: Receives input from the user and makes calls to Model and View to perform appropriate actions.


Express MVC Setup:

- Models: Will contain the data structure or schema.

- Views: Will manage what users see (usually in web applications).

- Controllers: Will handle the logic of your application.

---

 4. Nodemon Installation

Nodemon is a tool that automatically restarts your Node.js server when file changes in the directory are detected.

1. Install Nodemon globally:

   npm install -g nodemon

2. Alternatively, install Nodemon as a development dependency:

   npm install nodemon --save-dev

3. Update your `package.json` to use Nodemon:

    json:

   "scripts": {
     "start": "node index.js",
     "dev": "nodemon index.js"
   }

   Now, you can run your app in development mode with:

   npm run dev

---

 5. Express Server Configuration

1. Create a new `index.js` file:

   const express = require('express');
   const app = express();

   // Middleware to parse JSON
   app.use(express.json());

   // Basic route
   app.get('/', (req, res) => {
     res.send('Hello World!');
   });

   // Start the server
   const PORT = process.env.PORT || 3000;
   app.listen(PORT, () => {
     console.log(`Server running on port ${PORT}`);
   });


2. Start your server:

   npm run dev

   Your Express server should be running on `http://localhost:3000`.

---

 6. Postman Installation

1. Download and install Postman from [Postman official website](https://www.postman.com/downloads/).

2. Launch Postman after installation.

---

 7. Basic `GET` and `POST` Operations in API

1. `GET` Operation:

   - Add the following route to `index.js`:

     app.get('/api/greet', (req, res) => {
       res.json({ message: 'Hello from the API!' });
     });

   - Test with Postman:

     - Open Postman.
     - Set the request type to `GET`.
     - Enter the URL `http://localhost:3000/api/greet`.
     - Click Send.
     - You should see a response `{ "message": "Hello from the API!" }`.

2. `POST` Operation:

   - Add the following route to `index.js`:
     app.post('/api/echo', (req, res) => {
       const { message } = req.body;
       res.json({ echo: message });
     });

   - Test with Postman:
     - Open Postman.
     - Set the request type to `POST`.
     - Enter the URL `http://localhost:3000/api/echo`.
     - Go to the Body tab and select raw and then JSON format.
     - Enter the following JSON:

       {
         "message": "Hello Express"
       }

     - Click Send.
     - You should see a response `{ "echo": "Hello Express" }`.

---

 Summary

- Express Installation: Learned how to install and configure Express.

- MVC Architecture: Understood the MVC pattern in the context of Express.

- Nodemon Installation: Installed Nodemon to automatically restart the server on changes.

- Express Server Configuration: Set up a basic Express server.

- Postman Installation: Installed Postman for API testing.

- Basic API Operations: Implemented and tested basic `GET` and `POST` operations using Postman.


--------------------------------------------------------------------------------------------------------------------

server.js

const express=require('express');

//object create 

const app=express();

const port=4000; 

//configuration code for accepting json data / form data from ui
app.use(express.json());
app.use(express.urlencoded({ extended: false }));


app.get('/',(req,res)=>{
   res.send("<h3>Welcome to my Express Application and Coding and be Happy</h3>");
})

app.get('/test1',(req,res)=>{
    res.send("<ul><li>hello kolkata</li><li>hello pune</li></ul>");
}) 

app.get('/test2',(req,res)=>{
     let emp={id:10,nm:'raj',age:33,city:['pune','goa','punjab']};
     res.json(emp);
})

app.post('/insert',(req,res)=>{
      let data=req.body;
      console.log(data);
      res.status(200).json({msg:"thank you data received"});
})

app.post('/login',(req,res)=>{
     let data=req.body;
     if(data.uid=="sourav07" && data.pwd=="1234")
     {
        res.status(200).json({msg:"user is valid"});
     }
     else 
     {
        res.status(200).json({msg:"user is invalid"});
     }
})

app.get('/edit/:uid',(req,res)=>{
    let id=req.params.uid;
    console.log("Required id :"+id);
    res.status(200).json({msg:"id received"});
})

app.listen(port,()=>{
    console.log(`server is running in the port ${port}`);
})




package.json
{
  "name": "satsunapp",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev":"nodemon server.js"
  },
  "author": "s.kundu",
  "license": "ISC",
  "dependencies": {
    "express": "^4.19.2",
    "nodemon": "^3.1.4"
  }
}



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