Express MongoDB connection

 Step 1: Set Up Your Express.js Project

First, make sure you have Node.js installed on your machine. If not, download and install it from [nodejs.org](https://nodejs.org/).

1. Initialize a New Node.js Project:

   Open your terminal or command prompt, navigate to the directory where you want to create your 

project, and run:

 

   mkdir my-express-app

   cd my-express-app

   npm init -y

   

2. Install Required Packages:

   Install express and mongoose packages. Express.js will be used to create your server, while Mongoose will help you interact with MongoDB in an easier way.

 

  npm install express mongoose

   

3. Create Your Express App:

   Create a file named app.js (or index.js) in your project directory and set up your Express application:

   const express = require('express');

   const mongoose = require('mongoose');

   const app = express();

   const PORT = process.env.PORT || 3000;

   // Connect to MongoDB

   mongoose.connect('mongodb://localhost:27017/mydatabase', {

       useNewUrlParser: true,

       useUnifiedTopology: true

   })

   .then(() => console.log('MongoDB connected'))

   .catch(err => console.error('MongoDB connection error:', err));

   // Define a schema for your data (optional)

   const Schema = mongoose.Schema;

   const dataSchema = new Schema({

       name: String,

       age: Number

   });

   // Create a model based on the schema

   const Data = mongoose.model('Data', dataSchema);

   // Middleware to parse JSON bodies

   app.use(express.json());

   // Route to insert data

   app.post('/data', async (req, res) => {

       try {

           const { name, age } = req.body;

           const newData = new Data({ name, age });

           await newData.save();

           res.status(201).json(newData);

       } catch (err) {

           res.status(400).json({ message: err.message });

       }

   });

   // Start the server

   app.listen(PORT, () => {

       console.log(Server is running on http://localhost:${PORT});

   });

   

 

Step 2: Connect to MongoDB

In app.js, we use Mongoose to connect to MongoDB:

mongoose.connect('mongodb://localhost:27017/mydatabase', {

    useNewUrlParser: true,

    useUnifiedTopology: true

})

.then(() => console.log('MongoDB connected'))

.catch(err => console.error('MongoDB connection error:', err));

- Replace 'mongodb://localhost:27017/mydatabase' with your actual MongoDB connection string. Here, mydatabase is the name of your database.

 Step 3: Define a Schema and Create a Model

Define a schema for your data in app.js. A schema defines the structure of documents (like tables in SQL databases):

   const Schema = mongoose.Schema;

   const dataSchema = new Schema({

       name: String,

       age: Number

   });

- This example schema has fields name (a string) and age (a number). Adjust the schema according to your data structure.

Create a model based on the schema:

   

const Data = mongoose.model('Data', dataSchema);

   

- Data is the model name, and dataSchema is the schema you defined.

 Step 4: Insert Data

Define a route to handle POST requests to insert data into MongoDB:

app.post('/data', async (req, res) => {

    try {

        const { name, age } = req.body;

        const newData = new Data({ name, age });

        await newData.save();

        res.status(201).json(newData);

    } catch (err) {

        res.status(400).json({ message: err.message });

    }

});

- app.post('/data', ...) defines a route /data that handles POST requests.

- req.body contains the data sent with the request. Here, we expect name and age.

- Create a new instance of Data model (newData) with the received data.

- Use newData.save() to save the data to MongoDB.

- Respond with newData in JSON format if successful (status 201), or an error message (status 400) if there's an error.

Step 5: Run Your Express App

Save app.js, go to your terminal or command prompt, and run:

node app.js

- Your Express server will start running on http://localhost:3000.

 Step 6: Test Inserting Data

Use tools like Postman or curl to send a POST request to http://localhost:3000/data with JSON data in the request body, for example:

{

    "name": "John Doe",

    "age": 30

}

- Check the console for server logs and any error messages.

- Verify data insertion by checking your MongoDB database (mydatabase in this example).