Step 1: Set Up Your Environment

1. Install Node.js: Make sure you have Node.js installed on your machine. You can download it from nodejs.org.

2. Create a New Directory: Create a new directory for your project and navigate into it.

   mkdir my-backend
   cd my-backend

3. Initialize a New Node.js Project: Run the following command to create a package.json file.

   npm init -y

Step 2: Install Required Packages

Install the necessary packages for your backend.

npm install express mongoose body-parser cors

• express: A web framework for Node.js.
• mongoose: An ODM for MongoDB.
• body-parser: Middleware to parse incoming request bodies.
• cors: Middleware to enable Cross-Origin Resource Sharing.

Step 3: Set Up MongoDB

1. Create a MongoDB Database: If you don't have a MongoDB database, you can create one using MongoDB Atlas or install MongoDB locally.

2. Get Your Connection String: If you're using MongoDB Atlas, get your connection string from the dashboard. It should look something like this:

   mongodb+srv://<username>:<password>@cluster0.mongodb.net/mydatabase?retryWrites=true&w=majority
   

Step 4: Create the Backend Code

Create a file named server.js in your project directory and add the following code:

// server.js
const express = require('express');
const mongoose = require('mongoose');
const bodyParser = require('body-parser');
const cors = require('cors');

// Create an Express application
const app = express();

// Middleware
app.use(cors());
app.use(bodyParser.json());

// MongoDB connection
const mongoURI = 'YOUR_MONGODB_CONNECTION_STRING'; // Replace with your MongoDB connection string
mongoose.connect(mongoURI, { useNewUrlParser: true, useUnifiedTopology: true })
    .then(() => console.log('MongoDB connected'))
    .catch(err => console.error(err));

// Define a schema and model
const DataSchema = new mongoose.Schema({
    name: String,
    value: Number,
});

const DataModel = mongoose.model('Data', DataSchema);

// Routes
app.post('/data', async (req, res) => {
    const { name, value } = req.body;
    const newData = new DataModel({ name, value });

    try {
        const savedData = await newData.save();
        res.status(201).json(savedData);
    } catch (error) {
        res.status(500).json({ message: error.message });
    }
});

app.get('/data', async (req, res) => {
    try {
        const data = await DataModel.find();
        res.status(200).json(data);
    } catch (error) {
        res.status(500).json({ message: error.message });
    }
});

// Start the server
const PORT = process.env.PORT || 5000;
app.listen(PORT, () => {
    console.log(`Server is running on port ${PORT}`);
});

Step 5: Run Your Backend

1. Start the Server: Run the following command in your terminal:

   node server.js

2. Test Your API: You can use tools like Postman or curl to test your API.

   • POST Request: To add data, send a POST request to http://localhost:5000/data with a JSON body like:

     {
       "name": "Sample Data",
       "value": 123
     }

   • GET Request: To retrieve data, send a GET request to http://localhost:5000/data.

Step 6: (Optional) Use Environment Variables

For security reasons, it's a good practice to store sensitive information like your MongoDB connection string in environment variables. You can use the dotenv package for this.

1. Install dotenv:

   npm install dotenv

2. Create a .env file in your project root and add your MongoDB connection string:

   MONGODB_URI=YOUR_MONGODB_CONNECTION_STRING
   

3. Update your server.js to use the environment variable:

   require('dotenv').config();
   const mongoURI = process.env.MONGODB_URI;

Conclusion

You now have a basic backend set up with Node.js, Express, and MongoDB. You can expand this by adding more routes, validation, error handling, and other features as needed.