Here’s a comprehensive guide to creating a CRUD (Create, Read, Update, Delete) application using Express.js, React.js, and MongoDB. This guide will cover the backend setup (with Express and MongoDB) and the frontend setup (with React). The full-stack application will allow you to perform CRUD operations

1. Backend Setup (Express.js and MongoDB)

Step 1: Initialize the Node.js Project

1. Open your terminal or command prompt, and navigate to the folder where you want to create the project: mkdir express-react-mongo-crud cd express-react-mongo-crud
2. Initialize a new Node.js project: npm init -y

Step 2: Install Dependencies

Install the necessary backend dependencies using npm:

npm install express mongoose cors dotenv

• express: Web framework for Node.js.
• mongoose: MongoDB ORM to interact with MongoDB.
• cors: To enable cross-origin resource sharing.
• dotenv: To manage environment variables (e.g., MongoDB URI).

Step 3: Set Up Express Server

1. Create the server.js file in the root directory of the project: touch server.js
2. Add the following code to server.js to set up Express and MongoDB:

const express = require('express'); const mongoose = require('mongoose'); const cors = require('cors'); require('dotenv').config(); // For environment variables // Initialize the app const app = express(); // Set up middleware app.use(cors()); app.use(express.json()); // For parsing JSON data // MongoDB connection mongoose.connect(process.env.MONGO_URI, { useNewUrlParser: true, useUnifiedTopology: true }) .then(() => console.log('MongoDB connected')) .catch((err) => console.log('MongoDB connection error: ' + err)); // Define routes const itemRoutes = require('./routes/items'); app.use('/api/items', itemRoutes); // Basic route to check server app.get('/', (req, res) => { res.send('Hello World'); }); // Start the server const port = process.env.PORT || 5000; app.listen(port, () => { console.log(`Server running on port: ${port}`); });

1. Create a .env file to store your MongoDB URI: touch .env
2. Add the following MongoDB connection string to the .env file (adjust for your MongoDB instance): MONGO_URI=mongodb://localhost:27017/crud_app

Step 4: Create MongoDB Model

1. Create a models folder to store the database models: mkdir models
2. Create a Item.js file inside the models folder: touch models/Item.js
3. Add the following code to define the Item model in Item.js: const mongoose = require('mongoose'); const itemSchema = new mongoose.Schema({ name: { type: String, required: true }, description: { type: String, required: true }, }); module.exports = mongoose.model('Item', itemSchema);

Step 5: Create Routes for CRUD Operations

1. Create a routes folder to store the route definitions: mkdir routes
2. Create a items.js file inside the routes folder: touch routes/items.js
3. Add the following CRUD routes to items.js:

 const express = require('express'); const Item = require('../models/Item'); const router = express.Router(); // Create a new item router.post('/', async (req, res) => { const { name, description } = req.body; try { const newItem = new Item({ name, description }); await newItem.save(); res.status(201).json(newItem); } catch (error) { res.status(500).json({ error: error.message }); } }); // Get all items router.get('/', async (req, res) => { try { const items = await Item.find(); res.status(200).json(items); } catch (error) { res.status(500).json({ error: error.message }); } }); // Get a single item router.get('/:id', async (req, res) => { try { const item = await Item.findById(req.params.id); if (!item) return res.status(404).json({ error: 'Item not found' }); res.status(200).json(item); } catch (error) { res.status(500).json({ error: error.message }); } }); // Update an item router.put('/:id', async (req, res) => { try { const updatedItem = await Item.findByIdAndUpdate(req.params.id, req.body, { new: true }); if (!updatedItem) return res.status(404).json({ error: 'Item not found' }); res.status(200).json(updatedItem); } catch (error) { res.status(500).json({ error: error.message }); } }); // Delete an item router.delete('/:id', async (req, res) => { try { const deletedItem = await Item.findByIdAndDelete(req.params.id); if (!deletedItem) return res.status(404).json({ error: 'Item not found' }); res.status(200).json({ message: 'Item deleted' }); } catch (error) { res.status(500).json({ error: error.message }); } }); module.exports = router;

1. Now your backend is set up to handle CRUD operations for items.

2. Frontend Setup (React.js)

Step 1: Create the React App

1. Open a new terminal, navigate to the root folder of your project, and create a new React app inside the client folder: npx create-react-app client cd client
2. Install Axios to handle HTTP requests: npm install axios

Step 2: Create Items.js Component

1. Inside the src folder of your React app (client/src), create a new file named Items.js: touch src/Items.js
2. Add the following code to Items.js for fetching and displaying items:

 import React, { useState, useEffect } from 'react'; import axios from 'axios'; const Items = () => { const [items, setItems] = useState([]); const [name, setName] = useState(''); const [description, setDescription] = useState(''); const [editingItem, setEditingItem] = useState(null); // Fetch all items from backend useEffect(() => { axios.get('http://localhost:5000/api/items') .then(response => setItems(response.data)) .catch(error => console.log(error)); }, []); // Add a new item const handleAddItem = () => { axios.post('http://localhost:5000/api/items', { name, description }) .then(response => { setItems([...items, response.data]); setName(''); setDescription(''); }) .catch(error => console.log(error)); }; // Handle editing an item const handleEditItem = (item) => { setEditingItem(item); setName(item.name); setDescription(item.description); }; // Update an item const handleUpdateItem = () => { axios.put(`http://localhost:5000/api/items/${editingItem._id}`, { name, description }) .then(response => { setItems(items.map(item => (item._id === response.data._id ? response.data : item))); setEditingItem(null); setName(''); setDescription(''); }) .catch(error => console.log(error)); }; // Delete an item const handleDeleteItem = (id) => { axios.delete(`http://localhost:5000/api/items/${id}`) .then(() => setItems(items.filter(item => item._id !== id))) .catch(error => console.log(error)); }; return ( <div> <h1>CRUD Application</h1> <input type="text" value={name} onChange={(e) => setName(e.target.value)} placeholder="Item name" /> <input type="text" value={description} onChange={(e) => setDescription(e.target.value)} placeholder="Item description" /> <button onClick={editingItem ? handleUpdateItem : handleAddItem}> {editingItem ? 'Update Item' : 'Add Item'} </button> <ul> {items.map(item => ( <li key={item._id}> {item.name} - {item.description} <button onClick={() => handleEditItem(item)}>Edit</button> <button onClick={() => handleDeleteItem(item._id)}>Delete</button> </li> ))} </ul> </div> ); }; export default Items;

Step 3: Update App.js to Render Items Component

1. Open src/App.js and update it to include the Items component: import React from 'react'; import './App.css'; import Items from './Items'; function App() { return ( <div className="App"> <Items /> </div> ); } export default App;

Step 4: Run React and Express Servers

1. In your client folder, run the React development server: npm start
2. In the root folder, run the Express backend server: node server.js

OutPut:

Summary

• Backend: Set up Express and MongoDB to handle CRUD operations via API routes (/api/items).
• Frontend: Created a React component (Items.js) to interact with the backend, using Axios for HTTP requests to perform CRUD actions (add, update, delete, fetch items).
• Running both servers: Use npm start for the React frontend and node server.js for the backend server.

You now have a full-stack CRUD application with Express, React, and MongoDB. Let me know if you need further help or clarification!