Express js, React js and Mongo DB

Syllabus

Exercise - 1: Express JS – Routing, HTTP Methods

• 1a. Write a program to define a route, Handling Routes, Route Parameters, Query Parameters and URL building.
const express = require('express'); const app = express(); // Middleware to parse JSON request bodies app.use(express.json()); // user data stored in memory const users = { 1: { id: 1201, name: 'DIET', email: '1201@diet.ac.in' }, 2: { id: 1202, name: 'IT DEPT', email: '1202@diet.ac.in' } }; // Home route app.get('/', (req, res) => { res.send('Welcome to the User API!'); }); // Get all users or filter by name using query parameter app.get('/users', (req, res) => { const name = req.query.name; let result = Object.values(users); //to convert the object to an array if (name) { result = result.filter(user => user.name.toLowerCase() === name.toLowerCase()); } res.json(result); }); // Get a specific user by route parameter (user ID) app.get('/users/:id', (req, res) => { const user = users[req.params.id]; if (user) { res.json(user); } else { res.status(404).send('User not found'); } }); // Add a new user (POST method) app.post('/users', (req, res) => { const { id, name, email } = req.body; if (!id || !name || !email) { return res.status(400).send('Please provide id, name, and email'); } if (users[id]) { return res.status(409).send('User already exists'); } users[id] = { id, name, email }; res.status(201).json(users[id]); }); // Build a sample URL for a user app.get('/build-url/:id', (req, res) => { const id = req.params.id; const fullUrl = `${req.protocol}://${req.get('host')}/users/${id}?source=example`; res.send(`User URL: ${fullUrl}`); }); // Start the server app.listen(3000, () => { console.log('Server is running on http://localhost:3000'); });
• 1b. Write a program to accept data, retrieve data and delete a specified resource using http methods.
// app.js const express = require('express'); const app = express(); const port = 3000; // Middleware to parse JSON from request bodies app.use(express.json()); // database to store users let users = { 1: { id: 1201, name: 'DIET', email: '1201@diet.ac.in' }, 2: { id: 1202, name: 'IT DEPT', email: '1202@diet.ac.in' } }; // Add a new user app.post('/users', (req, res) => { const { id, name, email } = req.body; if (!id || !name || !email) { return res.status(400).send('Please provide id, name, and email'); } if (users[id]) { return res.status(409).send('User already exists'); } users[id] = { id, name, email }; res.status(201).json(users[id]); }); // Get all users app.get('/users', (req, res) => { res.json(Object.values(users)); }); // Get user by ID app.get('/users/:id', (req, res) => { const id = req.params.id; const user = users[id]; if (!user) { return res.status(404).send('User not found'); } res.json(user); }); // Delete user by ID app.delete('/users/:id', (req, res) => { const id = req.params.id; if (!users[id]) { return res.status(404).send('User not found'); } delete users[id]; res.send(`User with ID ${id} deleted`); }); // Start the server app.listen(port, () => { console.log(`Server running at http://localhost:${port}`); });

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Exercise - 2: