MERN Stack Quiz (Intermediate) - All Questions

This intermediate MERN Stack quiz focuses on applied full-stack concepts including REST APIs, MongoDB queries, React state management, Express middleware, and Node.js architecture. Ideal for developers with basic knowledge preparing for interviews and real-world MERN applications.

Question 1: Which MERN component handles business logic and APIs?

React
MongoDB
Backend (Node + Express)
Browser

Explanation: Node.js and Express handle APIs and business logic.

Question 2: What is the role of middleware in Express.js?

UI rendering
Database storage
Request and response processing
State management

Explanation: Middleware processes requests before reaching routes.

Question 3: Which HTTP status code indicates unauthorized access?

Explanation: 401 indicates authentication is required.

Question 4: Which React hook is best for complex state logic?

useState
useEffect
useReducer
useMemo

Explanation: useReducer handles complex state logic.

Question 5: What does CORS stand for?

Client Origin Resource Sharing
Cross-Origin Resource Sharing
Cross-Object Routing System
Client Object Request System

Explanation: CORS allows controlled cross-origin requests.

Question 6: Which Express middleware enables CORS?

helmet
cors
body-parser
morgan

Explanation: cors middleware enables cross-origin requests.

Question 7: Which MongoDB method updates multiple documents?

updateOne()
update()
updateMany()
replaceOne()

Explanation: updateMany() updates multiple documents.

Question 8: What is the purpose of JWT in MERN applications?

UI rendering
State management
Authentication and authorization
Database indexing

Explanation: JWT is used for secure authentication.

Question 9: Which part of JWT ensures data integrity?

Header
Payload
Signature
Token ID

Explanation: Signature verifies token integrity.

Question 10: Which React feature helps avoid unnecessary re-renders?

Virtual DOM
useEffect
useMemo
useState

Explanation: useMemo memoizes expensive calculations.

Question 11: Which HTTP method is idempotent?

POST
PATCH
PUT
CONNECT

Explanation: PUT is idempotent by design.

Question 12: Which MongoDB operator is used for filtering?

$set
$push
$match
$where

Explanation: $where filters documents using conditions.

Question 13: Which tool is commonly used for API testing in MERN?

Webpack
Jest
Postman
Babel

Explanation: Postman is used to test APIs.

Question 14: Which React hook fetches data from APIs?

useEffect
useState
useContext
useRef

Explanation: useEffect is used for side effects like data fetching.

Question 15: Which MongoDB feature improves query performance?

Indexes
Collections
Schemas
Documents

Explanation: Indexes speed up query execution.

Question 16: Which Node.js module handles environment variables?

env
dotenv
config
process-env

Explanation: dotenv loads environment variables from .env.

Question 17: Which HTTP status code indicates forbidden access?

Explanation: 403 means access is forbidden.

Question 18: Which Express method handles all HTTP verbs?

app.get()
app.post()
app.use()
app.all()

Explanation: app.all() handles all HTTP methods.

Question 19: Which React feature allows code splitting?

useCallback
React.lazy()
useMemo
Suspense API

Explanation: React.lazy() enables code splitting.

Question 20: Which MongoDB aggregation stage filters documents?

$group
$sort
$project
$match

Explanation: $match filters documents in aggregation.

Question 21: Which library handles password hashing in MERN?

crypto-js
bcrypt
jwt
hashlib

Explanation: bcrypt securely hashes passwords.

Question 22: Which React hook prevents function recreation?

useEffect
useReducer
useCallback
useRef

Explanation: useCallback memoizes functions.

Question 23: Which Node.js object handles incoming requests?

req
res
app
router

Explanation: req contains incoming request data.

Question 24: Which MongoDB relationship is embedded within documents?

Referenced
Embedded
Linked
Indexed

Explanation: Embedded documents store related data together.

Question 25: Which React hook manages global state without Redux?

useContext
useMemo
useRef
useEffect

Explanation: useContext provides global state sharing.

Question 26: Which HTTP method removes resources?

POST
GET
PUT
DELETE

Explanation: DELETE removes resources.

Question 27: Which Express middleware logs HTTP requests?

helmet
cors
morgan
cookie-parser

Explanation: morgan logs HTTP requests.

Question 28: Which MongoDB method removes documents?

remove()
deleteOne()
drop()
clear()

Explanation: deleteOne() removes a single document.

Question 29: Which React hook accesses DOM elements?

useRef
useState
useEffect
useContext

Explanation: useRef provides direct DOM access.

Question 30: Which Node.js feature enables non-blocking I/O?

Multithreading
Event loop
Worker threads
Promises

Explanation: Event loop enables non-blocking I/O.

Question 31: Which MongoDB command creates indexes?

addIndex()
createIndex()
index()
setIndex()

Explanation: createIndex() creates indexes.

Question 32: Which React feature improves performance by memoization?

useEffect
useMemo
useState
useContext

Explanation: useMemo memoizes values.

Question 33: Which Express object sends responses?

req
res
app
router

Explanation: res sends HTTP responses.

Question 34: Which MongoDB stage reshapes output fields?

$group
$project
$sort
$limit

Explanation: $project reshapes documents.

Question 35: Which HTTP status code indicates server error?

Explanation: 500 indicates internal server error.

Question 36: Which React hook handles side effects cleanup?

useState
useEffect
useContext
useReducer

Explanation: useEffect supports cleanup functions.

Question 37: Which MongoDB feature supports transactions?

Collections
Replica sets
Indexes
Documents

Explanation: Replica sets enable transactions.

Question 38: Which Node.js package manages routing?

http
router
express
path

Explanation: Express manages routing.

Question 39: Which React hook avoids prop drilling?

useEffect
useContext
useMemo
useRef

Explanation: useContext avoids prop drilling.

Question 40: Which MongoDB operator adds elements to arrays?

$push
$set
$add
$insert

Explanation: $push adds elements to arrays.

Question 41: Which Express middleware improves security headers?

helmet
cors
morgan
body-parser

Explanation: helmet adds security headers.

Question 42: Which React hook optimizes expensive functions?

useCallback
useEffect
useReducer
useContext

Explanation: useCallback memoizes functions.

Question 43: Which MongoDB command sorts results?

sort()
order()
group()
arrange()

Explanation: sort() orders query results.

Question 44: Which Node.js module handles paths?

fs
path
url
os

Explanation: path handles file paths.

Question 45: Which React feature loads components lazily?

Suspense
useMemo
useCallback
StrictMode

Explanation: Suspense supports lazy loading.

Question 46: Which MongoDB feature ensures schema structure?

Indexes
Collections
Mongoose schemas
Documents

Explanation: Mongoose schemas enforce structure.

Question 47: Which Express method starts the server?

app.start()
app.run()
app.listen()
app.open()

Explanation: app.listen() starts the server.

Question 48: Which React hook synchronizes state with props?

useEffect
useState
useContext
useRef

Explanation: useEffect syncs state with props.

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MERN Stack Quiz (Intermediate)

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MERN Stack Quiz (Intermediate)