Problem 1

Problem Statement: Create a function writeToFile(filePath, content) that takes the path to a file and user input content as input. The function should write the content to the specified file using the fs module.

Function Signature:

const writeToFile = (filePath, content) => {
    // Implementation
}

Expected Output:

Data written to output.txt

Test Cases:

writeToFile('test-files/log.txt', 'Today is MSWD Exam');
// Expected Output: Data written to log.txt
 
writeToFile('test-files/nonexistent-folder/output.txt', 'Content in a non-existent folder.');
// Expected Output: Error writing to file: ENOENT: no such file or directory...

Problem 2

Problem Statement: Create a function executeCommand(command) that takes a shell command as input and executes it using the child_process module. The function should print the output of the command to the console.

Function Signature:

const executeCommand = (command) => {
    // Implementation
}

Expected Output:

Command Output:
File1.txt
File2.txt

Test Cases:

executeCommand('ls -la');
// Expected Output: (output of ls -la)
 
executeCommand('echo "Hello, Node.js!"');
// Expected Output: Hello, Node.js!

Problem 3

Problem Statement: Create a function resolvePath(relativePath) that takes a relative path as input and resolves it to an absolute path using the path module. The function should print the resolved path to the console.

Function Signature:

const resolvePath = (relativePath) => {
    // Implementation
}

Expected Output:

Resolved Path: /Users/username/project/folder/file.txt

Test Cases:

resolvePath('../project/folder/file.txt');
// Expected Output: Resolved Path: /Users/username/project/folder/file.txt
 
resolvePath('nonexistent-folder/file.txt');
// Expected Output: Resolved Path: /Users/username/nonexistent-folder/file.txt

Problem 4

Problem Statement: Create a function checkFileExtension(filePath, expectedExtension) that takes a file path and an expected file extension as input. The function should check if the file has the expected extension using the path module and print the result to the console.

Function Signature:

const checkFileExtension = (filePath, expectedExtension)  => {
    // Implementation
}

Expected Output:

File has the expected extension: .txt

Test Cases:

checkFileExtension('test-files/report.pdf', '.pdf');
// Expected Output: File has the expected extension: .txt

checkFileExtension('test-files/profile_pic.png', '.jpg');
// Expected Output: File does not have the expected extension. Expected: .jpg, Actual: .png

Problem 5

Problem Statement: You are building a web application using Express in Node.js. Create an Express route to handle GET requests to the endpoint "/greet" that takes a query parameter "name" and returns a personalized greeting. If the name parameter is not provided, the default greeting should be "Namaskar, Guest!".

Function Signature:

/**
* Handles GET requests to "/greet" endpoint
* @param {Object} req - Express request object
* @param {Object} res - Express response object
*/
const greetHandler = (req, res) => {
  // Your implementation here
}

Expected Output:

If the "name" parameter is provided: "Namaskar, {name}!"
If the "name" parameter is not provided: "Namaskar, Guest!"

Test Cases:

Request to /greet?name=Girish should return "Namaskar, Girish!"
Request to /greet should return "Namaskar, Guest!"

Problem 6

Problem Statement:

Create a logging middleware for an Express application. The middleware should log detailed information about each incoming request, including the timestamp, HTTP method, URL, request headers, and request body.

Function Signature:

/** 
* Logging middleware for Express 
* @param {Object} req - Express request object 
* @param {Object} res - Express response object
* @param {Function} next - Express next function */

const loggingMiddleware = (req, res, next) => { 
    // Your implementation here 
}

Expected Output:

Each incoming request should be logged with detailed information.

Test Cases:

Make multiple requests and check the server logs for detailed information.

Problem 7

Problem Statement: Create an Express route that throws an error if the request parameter "number" is not a positive integer. Implement an error handling middleware to catch and handle this specific error, returning a custom error message and a 400 Bad Request status.

Function Signature:

/**
* Express route to handle requests with a positive integer parameter
* @param {Object} req - Express request object
* @param {Object} res - Express response object
*/
const positiveIntegerHandler = (req, res) => {
  // Your implementation here
}

Expected Output:

If "number" is a positive integer: Return a success message.
If "number" is not a positive integer: Trigger an error handled by the error handling middleware.

Test Cases:

Request to /positive?number=5 should return a success message.
Request to /positive?number=-2 should trigger the error handling middleware.

Problem 8

Problem Statement:

Create an Express application with MongoDB integration using Mongoose. Implement a function to establish a connection to a MongoDB database. Ensure that the connection is successful and log a success message.

Function Signature:

/**
* Establishes a connection to MongoDB using Mongoose
*/
const connectToMongoDB = () => {
  // Your implementation here
}

Expected Output:

If the connection is successful, log a success message.

Test Cases:

Call connectToMongoDB() and check the server logs for a successful connection message.

Define a Mongoose schema for a "User" with properties: "username" (string) and "email" (string).
Create a Mongoose model for the User schema.
Create an Express route to add a new user to the MongoDB database

Function Signature:

/**
* Adds a new user to the MongoDB database
* @param {Object} user - User object with properties username and email
*/
const addUserToDatabase = (user) => {
  // Your implementation here
}

Expected Output:

If the user is successfully added, log a success message.

Test Cases:

Call addUserToDatabase({ username: 'smaranjit_ghose', email: 'hello@smaranjitghose.com' }) and check the server logs for a success message.

Create an Express route that retrieves all users from the MongoDB database and returns them as a JSON response.

Function Signature:

/**
* Express route to get all users from MongoDB
* @param {Object} req - Express request object
* @param {Object} res - Express response object
*/
const getAllUsers = (req, res) => {
  // Your implementation here
}

Expected Output:

Return a JSON response with an array of user objects.

Test Cases:

Access the route /users and check if the response contains the expected user data.

Remember to connect Mongoose to your MongoDB database using mongoose.connect.

Problem 9

Problem Statement:

Create an Express application with MongoDB integration using Mongoose. Implement a function to establish a connection to a MongoDB database. Ensure that the connection is successful and log a success message.

Function Signature:

/**
* Establishes a connection to MongoDB using Mongoose
*/
const connectToMongoDB = () => {
  // Your implementation here
}

Define a Mongoose schema for the product with properties like "name," "price," and "quantity."
Create a Mongoose Model for the Product Schema
Implement a set of CRUD (Create, Read, Update, Delete) operations for a "Product" entity using MongoDB and Mongoose Implement functions to create, read, update, and delete products.

Function Signature:

/**
* Creates a new product in MongoDB
* @param {Object} product - Product object with properties name, price, and quantity
*/
const createProduct = (product) => {
  // Your implementation here
}
 
/**
* Retrieves all products from MongoDB
* @returns {Array} - Array of product objects
*/
const getAllProducts = () => {
  // Your implementation here
}
 
/**
* Updates a product in MongoDB
* @param {string} productId - ID of the product to update
* @param {Object} updatedProduct - Updated product object
*/
const updateProduct = (productId, updatedProduct) => {
  // Your implementation here
}
 
/**
* Deletes a product from MongoDB
* @param {string} productId - ID of the product to delete
*/
const deleteProduct = (productId) => {
  // Your implementation here
}

Expected Output:

The functions should perform the respective CRUD operations on the "Product" collection in MongoDB.

Test Cases:

Create a product, retrieve all products, update a product, and then delete the product.

Problem 10

Problem Statement: Implement a rate-limiting middleware for an Express application. The middleware should limit the number of requests from a single IP address to a specified rate, and return a 429 Too Many Requests status if the limit is exceeded.

Function Signature:

/**
 * Rate-limiting middleware for Express
 * @param {Object} req - Express request object
 * @param {Object} res - Express response object
 * @param {Function} next - Express next function
 */
const rateLimitMiddleware = (req, res, next) => {
  // Your implementation here
}

Expected Output:

If the number of requests from a single IP is below the limit, allow the request to proceed.
If the limit is exceeded, return a 429 Too Many Requests status.

Test Cases:

Send requests within the limit; all should proceed.
Send requests exceeding the limit; some should return a 429 status.

Problem 11

Problem Statement:

You are developing a complex web application with multiple routes and middleware in Node.js and Express. You want to implement a centralized error handling mechanism to catch and handle errors gracefully without crashing the server. Design a middleware function that intercepts errors thrown by route handlers or other middleware and sends an appropriate error response to the client.

Function Signature:

const errorHandler = (err, req, res, next) => {
    // Your implementation here
}



## Problem 12

 
**Problem Statement:**
Implement an authentication middleware for an Express application. The middleware should check for the presence of a valid JWT (JSON Web Token) in the request headers. If a valid token is present, allow the request to proceed; otherwise, return a 401 Unauthorized status.
 
**Function Signature:**
```javascript
/**
* Authentication middleware for Express
* @param {Object} req - Express request object
* @param {Object} res - Express response object
* @param {Function} next - Express next function
*/
const authenticationMiddleware = (req, res, next) => {
  // Your implementation here
}

Expected Output:

If a valid JWT is present, allow the request to proceed.
If no JWT is present or it's invalid, return a 401 Unauthorized status.

Test Cases:

Request with a valid JWT should proceed.
Request without a JWT or with an invalid JWT should return a 401 Unauthorized status.

Problem 13

Fork the https://github.com/smaranjitghose/ParulUniversityMEAN Repo
Create a clone of the forked repo
Make a new branch mswd_exam
Add a new file "DIVISION_ENROLLMENT_NO_Exam.MD"
The file should contain a breif definition of What is Git? Features of Git
Stage and Commit the Changes
Push to Forked Repo on GitHub
Make a Pull Request

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