Add: [Backend] Database-connect

Domains/Backend/MiniProjects/DatabaseConnect/.gitignore

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+.env
+node_modules

Domains/Backend/MiniProjects/DatabaseConnect/README.md

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+**Contributor:** Ogagaoghene Esavwede
+**Domain:** Backend
+**Difficulty:** Beginner–Intermediate
+**Tech Stack:** Node.js, Express.js, Mongoose
+
+# 🗄️ Express + Mongoose Database Connection
+
+---
+
+## 📝 Description
+
+A simple Express.js application demonstrating how to **connect to MongoDB using Mongoose** and **set up event listeners** for key database connection states.
+This project helps you understand how to manage and monitor your MongoDB connection lifecycle effectively.
+
+---
+
+## 🎯 Features
+
+- ✅ Connects to MongoDB using **Mongoose**
+- ✅ Monitors key connection events like `connected`, `disconnected`, `error`, etc.
+- ✅ Automatically reconnects on disconnection
+- ✅ Provides clear console feedback for database connection status
+- ✅ Easily configurable via environment variables
+
+---
+
+## 🛠️ Tech Stack
+
+- **Node.js** – Runtime environment
+- **Express.js** – Web framework
+- **Mongoose** – ODM for MongoDB
+
+---
+
+## 🚀 How to Run
+
+### Prerequisites
+
+- Node.js installed (v14 or higher)
+- MongoDB running locally or in the cloud
+- npm package manager
+
+### Installation Steps
+
+1. **Install dependencies**
+
+   ```bash
+   npm install
+   ```
+
+2. **Start MongoDB**
+
+   Make sure MongoDB is running locally or update your `.env` file with your connection URI.
+
+3. **Start the server**
+
+   ```bash
+   npm start
+   ```
+
+4. **Server runs at**
+
+   ```
+   http://localhost:3000
+   ```
+
+---
+
+## 📁 Project Structure
+
+```
+mongoose-connection/
+├── src/
+│   ├── app.js             # Main Express application
+│   └── database.js        # MongoDB connection and event listeners
+├── package.json           # Dependencies and scripts
+├── .gitignore             # Git ignore file
+└── README.md              # Documentation
+```
+
+---
+
+## 📡 Example Usage
+
+### app.js
+
+```javascript
+import express from "express";
+import connectToDatabase from "./database.js";
+
+const app = express();
+const PORT = 3000;
+
+// Connect to MongoDB
+connectToDatabase();
+
+app.get("/", (req, res) => {
+  res.status(200).json({ success: true, message: "hello" });
+});
+
+app.listen(PORT, () => {
+  console.log("Server listening on PORT: " + PORT);
+});
+```
+
+---
+
+### database.js
+
+```javascript
+import mongoose from "mongoose";
+
+export default async function connectToDatabase() {
+  try {
+    const DB_URI = "mongodb://localhost:27017/mysampledb";
+
+    // Event listeners
+    mongoose.connection.on("connecting", () => {
+      console.log("Connecting to database");
+    });
+
+    mongoose.connection.on("connected", () => {
+      console.log("Connected to database");
+    });
+
+    mongoose.connection.on("disconnecting", () => {
+      console.log("Disconnecting from database");
+    });
+
+    mongoose.connection.on("disconnected", () => {
+      console.log("Disconnected from database");
+    });
+
+    mongoose.connection.on("reconnected", () => {
+      console.log("Reconnected to database");
+    });
+
+    mongoose.connection.on("close", () => {
+      console.log("Database connection closed");
+    });
+
+    mongoose.connection.on("error", (error) => {
+      console.error("Database Error:", error);
+    });
+
+    await mongoose.connect(process.env.DB_URI || DB_URI);
+  } catch (error) {
+    console.error("Database connection failed:", error);
+  }
+}
+```
+
+---
+
+## 💻 Code Comparison
+
+### ❌ Old Way (Without Event Handling)
+
+```javascript
+mongoose.connect("mongodb://localhost:27017/mysampledb");
+console.log("Database connected");
+```
+
+### ✅ New Way (With Event Listeners)
+
+```javascript
+mongoose.connection.on("connected", () => {
+  console.log("Connected to database");
+});
+```
+
+---
+
+## 📚 Learning Outcomes
+
+### Skills Practiced
+
+- ✅ Setting up MongoDB connection with Mongoose
+- ✅ Handling connection lifecycle events
+- ✅ Error handling in database connections
+- ✅ Writing modular database connection logic
+
+### Concepts Learned
+
+- Mongoose connection states
+- Event-driven database monitoring
+- Using environment variables for database URIs
+- Clean separation of app logic and database logic
+
+---
+
+## 🎨 Enhancement Ideas
+
+Want to improve this project? Try adding:
+
+1. **Logger Integration** – Replace `console.log` with Pino or Winston
+2. **Retry Mechanism** – Automatically reconnect after disconnection
+3. **Configuration File** – Manage DB settings via a config folder
+4. **Cloud Connection** – Connect to MongoDB Atlas with credentials
+5. **Health Check Route** – Add an endpoint to monitor DB connection status
+
+---
+
+## 🧪 Testing
+
+### Using curl
+
+```bash
+curl http://localhost:3000/
+```
+
+**Terminal Output:**
+
+```
+Connecting to database
+Connected to database
+Server listening on PORT: 3000
+```
+
+---
+
+## 🚀 Future Enhancements
+
+- [ ] Add retry logic for failed connections
+- [ ] Add proper logging system
+- [ ] Implement graceful shutdown
+- [ ] Integrate with a cloud-based MongoDB
+
+---
+
+## 📄 License
+
+MIT License — Free to use and modify!
+
+---
+
+## 🤝 Contributing
+
+This project is open-source and created to help developers **learn how to connect Mongoose with Express and handle database events cleanly**.
+
+Feel free to:
+
+- Fork and enhance
+- Report issues
+- Suggest improvements
+- Use it as a MongoDB starter template
+
+---
+
+Would you like me to add your **LinkedIn and GitHub profile links** to the “Contributor” section too (like in your other README)?

Domains/Backend/MiniProjects/DatabaseConnect/app.js

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+import express from "express";
+import connectToDB from "./database.js";
+
+const app = express();
+const PORT = 3000;
+
+// connect to database
+connectToDB();
+
+// middleware
+app.use(express.json());
+
+// routes
+app.get("/", (req, res) => {
+  console.log("home route hit");
+  res.status(200).json({ success: true, message: "hello" });
+});
+
+app.listen(PORT, () => {
+  console.log("Server listening on PORT: " + PORT);
+});

Domains/Backend/MiniProjects/DatabaseConnect/database.js

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+import mongoose from "mongoose";
+
+export default async function connectToDB() {
+  try {
+    const DB_URI = process.env.DB_URI || "mongodb://localhost:27017/mysampledb";
+
+    mongoose.connection.on("connecting", () => {
+      console.log("connecting to database");
+    });
+
+    mongoose.connection.on("connected", () => {
+      console.log("connected to database");
+    });
+
+    mongoose.connection.on("disconnected", () => {
+      console.log("database connection disconnected");
+    });
+
+    mongoose.connection.on("reconnected", () => {
+      console.log("database reconnected");
+    });
+
+    mongoose.connection.on("close", () => {
+      console.log("database connection close");
+    });
+
+    mongoose.connection.on("error", (e) => {
+      console.log("Database encountered an error");
+      console.error(e);
+    });
+
+    await mongoose.connect(DB_URI);
+  } catch (e) {
+    console.log("Error Occured while connecting to DB");
+    process.exit(1);
+  }
+}