Take this MERN Stack Developer Practice Test to assess your skills in MongoDB, Express, React, and Node.js. Ideal for interview prep and full-stack development mastery.

MERN Stack Developer Practice Test

Which hook correctly replaces ___ to prevent recalculating expensiveCalculation(num) on every render unless num changes?


You have a MongoDB collection called products with the following document structure to answer the following question?
To optimize this query for performance, which of the following compound indexes would be most appropriate?


You’re building a modular Express.js app and want to apply custom logging middleware to all incoming requests, regardless of their route or HTTP method. Consider the snippet below and what is the value in the  blank?

Which option should replace _____ to ensure the logger runs for every route and method?


 What will happen if next() is not called in Express middleware?


Which command is used to create a compound index in MongoDB?


 In MongoDB, which of the following ensures a field is unique across documents?


 What data type does MongoDB use for document _id by default?


Which method from Node.js 'fs/promises' module is used to read a file asynchronously?

In React, why would you use a controlled component for a form input?

Which MongoDB stage is used in aggregation to filter documents based on conditions?

To uniquely identify elements for reconciliation

Why should keys be provided when rendering lists in React?


Runs immediately after current function finishes

 What is the purpose of process.nextTick()?


Which Node.js module is used for handling binary data streams?


Updating a virtual representation first and then syncing differences

React’s Virtual DOM optimizes performance by:


app.use(express.urlencoded({ extended: true }))

Consider the following Express.js server setup and what is the output of the following?
When you send a POST request to /data with a JSON payload, req.body is coming back as undefined.
Which line of middleware is missing and required to properly parse the incoming JSON body?


What will this MongoDB query return?

db.users.find({ age: { $gt: 30 } })


Which scenario is most appropriate for using the useReducer hook in React?

 In a RESTful API built with Express, consider the following route for creating a new user and what is the value in the blank space?
