ReactJS Online Test

The React test uses scenario-based MCQ questions to evaluate the understanding of React component lifecycle, the ability to work with JSX, user events, React State, functional components, and Hooks to create dynamic React applications. The test has JavaScript MCQs to assess ES6 fundamentals, DOM, Fetch, Promises and Async / Await. The test includes coding questions to evaluate hands-on JavaScript programming skills.

Get started for free

Preview questions

Screen candidates with a 40 mins test

Test duration: 40 mins

Difficulty level: Moderate

Availability: Ready to use

Questions:

5 JavaScript MCQs
5 React MCQs
1 JavaScript Coding Question

Covered skills:

Building Content with JSX

Communicating with Props

Class-Based Components

React State

Lifecycle Methods

Handling User Input with Forms and Events

Making API Requests with React

Building Lists of Records

Using Refs for DOM Access

Understanding Hooks in React

Component and Route Navigation

Deploying a React App

Integrating React with State management libraries

Handling Authentication with React

Using the Context System with React

Get started for free

Preview questions

Use Adaface tests trusted by recruitment teams globally

Adaface is used by 1500+ businesses in 80 countries.

Adaface skill assessments measure on-the-job skills of candidates, providing employers with an accurate tool for screening potential hires.

Use the ReactJS Test to shortlist qualified candidates

The ReactJS Online Test helps recruiters and hiring managers identify qualified candidates from a pool of resumes, and helps in taking objective hiring decisions. It reduces the administrative overhead of interviewing too many candidates and saves time by filtering out unqualified candidates at the first step of the hiring process.

The test screens for the following skills that hiring managers look for in candidates:

Building content with JSX
Communicating with Props
Implementing Class-Based Components
Managing React State
Working with React Lifecycle Methods
Handling User Input with Forms and Events
Making API Requests with React
Building Lists of Records
Accessing DOM with Refs
Understanding Hooks in React
Component and Route Navigation
Deploying a React App
Integrating React with State Management Libraries
Handling Authentication with React
Using the Context System with React

Get started for free

Preview questions

Screen candidates with the highest quality questions

We have a very high focus on the quality of questions that test for on-the-job skills. Every question is non-googleable and we have a very high bar for the level of subject matter experts we onboard to create these questions. We have crawlers to check if any of the questions are leaked online. If/ when a question gets leaked, we get an alert. We change the question for you & let you know.

How we design questions

These are just a small sample from our library of 15,000+ questions. The actual questions on this React.js Online Test will be non-googleable.

🧐 Question
Hard Context re-renders React Context API Conditional Rendering Component Lifecycle State	Solve
Review the following React code: Pick the correct statements: A: The code renders 10 INDIAN RUPEE B: The code renders 10 SINGAPORE DOLLAR C: The code does not render anything and throws an error since JavaScript objects are not valid as React children D: When the currency portion is clicked, the parent component is re-rendered E: When the currency portion is clicked, parent component will skip the re-render because shouldComponentUpdate returns false F: Parent component can be converted to a functional component with memoization (useMemo or memo) to avoid the re-render
Medium Hooks with Conditional Rendering Hooks Conditional Rendering Event Handling	Solve
Consider a React functional component that utilizes various hooks and conditional rendering. The component is designed to fetch and display a list of items from an API, with the ability to filter the list based on user input. Here's the pseudo-code structure: In this component, which of the following is a potential issue or inefficiency? A: The component will re-render excessively due to the `setFilter` call. B: The `useEffect` hook will run on every render, causing performance issues. C: The `fetchItems` function may cause a memory leak if the component unmounts during the fetch. D: The `useMemo` hook for `filteredItems` is unnecessary and can be removed without impact. E: The component will fail to display items when the filter is cleared. F: There are no significant issues; the component is implemented optimally.
Medium Rhyme Reducer Reducer functions Immutable update patterns Lazy initialization	Solve
Which of the following React code snippets - triggers the reducer ‘rhymeReducer’ to update the ‘song’ value to ‘Jack and Jill’ - renders the updated ‘song’ value - does not produce any errors/warnings
Hard State Handling with Custom Hooks Custom Hooks Context API Event Handling	Solve
Consider a React application where a custom hook `useComplexState` is defined to manage a complex state object. The application also uses the Context API to pass down the state and dispatch function. Below is the pseudo-code for the custom hook and a component using it: Given this setup, which of the following statements best describes the potential issue or challenge with `MyComponent`? A: The component will not re-render when the global state changes. B: The `fetchData` function will cause an infinite loop of re-renders. C: The component will lose its state when the global state updates. D: There will be a memory leak due to improper cleanup in `useEffect`. E: The `dispatch` function from `useComplexState` will conflict with the global dispatch. F: There is no issue; the component is implemented correctly.
Medium Async Await Promises Promises Async-Await	Solve
What will the following code output? A: 24 after 5 seconds and after another 5 seconds, another 24 B: 24 followed by another 24 immediately C: 24 immediately and another 24 after 5 seconds D: After 5 seconds, 24 and 24 E: Undefined F: NaN G: None of these
Medium Bitcoin prices Axios Promises	Solve
Review the following JavaScript code and pick the correct options: Assume that the API returns a successful 200 response code and a JSON object as the response body. What would the value of ‘a’ be after the code is executed?
Medium My Module Scope	Solve
What will the output of the following JavaScript code be?
Medium Promise Resolve Promises Async-Await	Solve
What does the following code output?
Easy Throw, Try, Async Promises Async-Await	Solve
What does the following JS code output?
Easy Registration Queue Logic Queues	Solve
We want to register students for the next semester. All students have a receipt which shows the amount pending for the previous semester. A positive amount (or zero) represents that the student has paid extra fees, and a negative amount represents that they have pending fees to be paid. The students are in a queue for the registration. We want to arrange the students in a way such that the students who have a positive amount on the receipt get registered first as compared to the students who have a negative amount. We are given a queue in the form of an array containing the pending amount. For example, if the initial queue is [20, 70, -40, 30, -10], then the final queue will be [20, 70, 30, -40, -10]. Note that the sequence of students should not be changed while arranging them unless required to meet the condition. ⚠️⚠️⚠️ Note: - The first line of the input is the length of the array. The second line contains all the elements of the array. - The input is already parsed into an array of "strings" and passed to a function. You will need to convert string to integer/number type inside the function. - You need to "print" the final result (not return it) to pass the test cases. For the example discussed above, the input will be: 5 20 70 -40 30 -10 Your code needs to print the following to the standard output: 20 70 30 -40 -10
Medium Visitors Count Strings Logic	Solve
A manager hires a staff member to keep a record of the number of men, women, and children visiting the museum daily. The staff will note W if any women visit, M for men, and C for children. You need to write code that takes the string that represents the visits and prints the count of men, woman and children. The sequencing should be in decreasing order. Example: Input: WWMMWWCCC Expected Output: 4W3C2M Explanation: ‘W’ has the highest count, then ‘C’, then ‘M’. ⚠️⚠️⚠️ Note: - The input is already parsed and passed to a function. - You need to "print" the final result (not return it) to pass the test cases. - If the input is- “MMW”, then the expected output is "2M1W" since there is no ‘C’. - If any of them have the same count, the output should follow this order - M, W, C.

	🧐 Question	🔧 Skill
	Hard Context re-renders React Context API Conditional Rendering Component Lifecycle State	3 mins React	Solve
Review the following React code: Pick the correct statements: A: The code renders 10 INDIAN RUPEE B: The code renders 10 SINGAPORE DOLLAR C: The code does not render anything and throws an error since JavaScript objects are not valid as React children D: When the currency portion is clicked, the parent component is re-rendered E: When the currency portion is clicked, parent component will skip the re-render because shouldComponentUpdate returns false F: Parent component can be converted to a functional component with memoization (useMemo or memo) to avoid the re-render
	Medium Hooks with Conditional Rendering Hooks Conditional Rendering Event Handling	3 mins React	Solve
Consider a React functional component that utilizes various hooks and conditional rendering. The component is designed to fetch and display a list of items from an API, with the ability to filter the list based on user input. Here's the pseudo-code structure: In this component, which of the following is a potential issue or inefficiency? A: The component will re-render excessively due to the `setFilter` call. B: The `useEffect` hook will run on every render, causing performance issues. C: The `fetchItems` function may cause a memory leak if the component unmounts during the fetch. D: The `useMemo` hook for `filteredItems` is unnecessary and can be removed without impact. E: The component will fail to display items when the filter is cleared. F: There are no significant issues; the component is implemented optimally.
	Medium Rhyme Reducer Reducer functions Immutable update patterns Lazy initialization	3 mins React	Solve
Which of the following React code snippets - triggers the reducer ‘rhymeReducer’ to update the ‘song’ value to ‘Jack and Jill’ - renders the updated ‘song’ value - does not produce any errors/warnings
	Hard State Handling with Custom Hooks Custom Hooks Context API Event Handling	3 mins React	Solve
Consider a React application where a custom hook `useComplexState` is defined to manage a complex state object. The application also uses the Context API to pass down the state and dispatch function. Below is the pseudo-code for the custom hook and a component using it: Given this setup, which of the following statements best describes the potential issue or challenge with `MyComponent`? A: The component will not re-render when the global state changes. B: The `fetchData` function will cause an infinite loop of re-renders. C: The component will lose its state when the global state updates. D: There will be a memory leak due to improper cleanup in `useEffect`. E: The `dispatch` function from `useComplexState` will conflict with the global dispatch. F: There is no issue; the component is implemented correctly.
	Medium Async Await Promises Promises Async-Await	2 mins JavaScript	Solve
What will the following code output? A: 24 after 5 seconds and after another 5 seconds, another 24 B: 24 followed by another 24 immediately C: 24 immediately and another 24 after 5 seconds D: After 5 seconds, 24 and 24 E: Undefined F: NaN G: None of these
	Medium Bitcoin prices Axios Promises	2 mins JavaScript	Solve
Review the following JavaScript code and pick the correct options: Assume that the API returns a successful 200 response code and a JSON object as the response body. What would the value of ‘a’ be after the code is executed?
	Medium My Module Scope	2 mins JavaScript	Solve
What will the output of the following JavaScript code be?
	Medium Promise Resolve Promises Async-Await	2 mins JavaScript	Solve
What does the following code output?
	Easy Throw, Try, Async Promises Async-Await	2 mins JavaScript	Solve
What does the following JS code output?
	Easy Registration Queue Logic Queues	30 mins Coding	Solve
We want to register students for the next semester. All students have a receipt which shows the amount pending for the previous semester. A positive amount (or zero) represents that the student has paid extra fees, and a negative amount represents that they have pending fees to be paid. The students are in a queue for the registration. We want to arrange the students in a way such that the students who have a positive amount on the receipt get registered first as compared to the students who have a negative amount. We are given a queue in the form of an array containing the pending amount. For example, if the initial queue is [20, 70, -40, 30, -10], then the final queue will be [20, 70, 30, -40, -10]. Note that the sequence of students should not be changed while arranging them unless required to meet the condition. ⚠️⚠️⚠️ Note: - The first line of the input is the length of the array. The second line contains all the elements of the array. - The input is already parsed into an array of "strings" and passed to a function. You will need to convert string to integer/number type inside the function. - You need to "print" the final result (not return it) to pass the test cases. For the example discussed above, the input will be: 5 20 70 -40 30 -10 Your code needs to print the following to the standard output: 20 70 30 -40 -10
	Medium Visitors Count Strings Logic	30 mins Coding	Solve
A manager hires a staff member to keep a record of the number of men, women, and children visiting the museum daily. The staff will note W if any women visit, M for men, and C for children. You need to write code that takes the string that represents the visits and prints the count of men, woman and children. The sequencing should be in decreasing order. Example: Input: WWMMWWCCC Expected Output: 4W3C2M Explanation: ‘W’ has the highest count, then ‘C’, then ‘M’. ⚠️⚠️⚠️ Note: - The input is already parsed and passed to a function. - You need to "print" the final result (not return it) to pass the test cases. - If the input is- “MMW”, then the expected output is "2M1W" since there is no ‘C’. - If any of them have the same count, the output should follow this order - M, W, C.

	🧐 Question	🔧 Skill	💪 Difficulty	⌛ Time
	Context re-renders React Context API Conditional Rendering Component Lifecycle State	React	Hard	3 mins	Solve
Review the following React code: Pick the correct statements: A: The code renders 10 INDIAN RUPEE B: The code renders 10 SINGAPORE DOLLAR C: The code does not render anything and throws an error since JavaScript objects are not valid as React children D: When the currency portion is clicked, the parent component is re-rendered E: When the currency portion is clicked, parent component will skip the re-render because shouldComponentUpdate returns false F: Parent component can be converted to a functional component with memoization (useMemo or memo) to avoid the re-render
	Hooks with Conditional Rendering Hooks Conditional Rendering Event Handling	React	Medium	3 mins	Solve
Consider a React functional component that utilizes various hooks and conditional rendering. The component is designed to fetch and display a list of items from an API, with the ability to filter the list based on user input. Here's the pseudo-code structure: In this component, which of the following is a potential issue or inefficiency? A: The component will re-render excessively due to the `setFilter` call. B: The `useEffect` hook will run on every render, causing performance issues. C: The `fetchItems` function may cause a memory leak if the component unmounts during the fetch. D: The `useMemo` hook for `filteredItems` is unnecessary and can be removed without impact. E: The component will fail to display items when the filter is cleared. F: There are no significant issues; the component is implemented optimally.
	Rhyme Reducer Reducer functions Immutable update patterns Lazy initialization	React	Medium	3 mins	Solve
Which of the following React code snippets - triggers the reducer ‘rhymeReducer’ to update the ‘song’ value to ‘Jack and Jill’ - renders the updated ‘song’ value - does not produce any errors/warnings
	State Handling with Custom Hooks Custom Hooks Context API Event Handling	React	Hard	3 mins	Solve
Consider a React application where a custom hook `useComplexState` is defined to manage a complex state object. The application also uses the Context API to pass down the state and dispatch function. Below is the pseudo-code for the custom hook and a component using it: Given this setup, which of the following statements best describes the potential issue or challenge with `MyComponent`? A: The component will not re-render when the global state changes. B: The `fetchData` function will cause an infinite loop of re-renders. C: The component will lose its state when the global state updates. D: There will be a memory leak due to improper cleanup in `useEffect`. E: The `dispatch` function from `useComplexState` will conflict with the global dispatch. F: There is no issue; the component is implemented correctly.
	Async Await Promises Promises Async-Await	JavaScript	Medium	2 mins	Solve
What will the following code output? A: 24 after 5 seconds and after another 5 seconds, another 24 B: 24 followed by another 24 immediately C: 24 immediately and another 24 after 5 seconds D: After 5 seconds, 24 and 24 E: Undefined F: NaN G: None of these
	Bitcoin prices Axios Promises	JavaScript	Medium	2 mins	Solve
Review the following JavaScript code and pick the correct options: Assume that the API returns a successful 200 response code and a JSON object as the response body. What would the value of ‘a’ be after the code is executed?
	My Module Scope	JavaScript	Medium	2 mins	Solve
What will the output of the following JavaScript code be?
	Promise Resolve Promises Async-Await	JavaScript	Medium	2 mins	Solve
What does the following code output?
	Throw, Try, Async Promises Async-Await	JavaScript	Easy	2 mins	Solve
What does the following JS code output?
	Registration Queue Logic Queues	Coding	Easy	30 mins	Solve
We want to register students for the next semester. All students have a receipt which shows the amount pending for the previous semester. A positive amount (or zero) represents that the student has paid extra fees, and a negative amount represents that they have pending fees to be paid. The students are in a queue for the registration. We want to arrange the students in a way such that the students who have a positive amount on the receipt get registered first as compared to the students who have a negative amount. We are given a queue in the form of an array containing the pending amount. For example, if the initial queue is [20, 70, -40, 30, -10], then the final queue will be [20, 70, 30, -40, -10]. Note that the sequence of students should not be changed while arranging them unless required to meet the condition. ⚠️⚠️⚠️ Note: - The first line of the input is the length of the array. The second line contains all the elements of the array. - The input is already parsed into an array of "strings" and passed to a function. You will need to convert string to integer/number type inside the function. - You need to "print" the final result (not return it) to pass the test cases. For the example discussed above, the input will be: 5 20 70 -40 30 -10 Your code needs to print the following to the standard output: 20 70 30 -40 -10
	Visitors Count Strings Logic	Coding	Medium	30 mins	Solve
A manager hires a staff member to keep a record of the number of men, women, and children visiting the museum daily. The staff will note W if any women visit, M for men, and C for children. You need to write code that takes the string that represents the visits and prints the count of men, woman and children. The sequencing should be in decreasing order. Example: Input: WWMMWWCCC Expected Output: 4W3C2M Explanation: ‘W’ has the highest count, then ‘C’, then ‘M’. ⚠️⚠️⚠️ Note: - The input is already parsed and passed to a function. - You need to "print" the final result (not return it) to pass the test cases. - If the input is- “MMW”, then the expected output is "2M1W" since there is no ‘C’. - If any of them have the same count, the output should follow this order - M, W, C.

Test candidates on core ReactJS Hiring Test topics

Building Content with JSX: Building Content with JSX means creating user interface components in React using JSX syntax. JSX is a syntax extension for JavaScript that allows you to write HTML-like code in your JavaScript files. This skill should be measured in the test to assess a candidate's ability to understand and use JSX to create dynamic and reusable UI components.

Communicating with Props: Communicating with Props involves passing data from one component to another in React. Props are a way to pass information from a parent component to its child component. This skill should be measured in the test to evaluate a candidate's ability to design and implement a component hierarchy that effectively communicates data between components.

Class-Based Components: Class-Based Components are a way to define and create reusable components in React. They are implemented as JavaScript classes that extend the base React Component class. This skill should be measured in the test to assess a candidate's understanding of class-based component syntax and their ability to create and manage component state using class methods.

React State: React State refers to the state management system provided by React. State allows components to hold and manage their own data, which can be updated and rendered automatically in response to changes. This skill should be measured in the test to evaluate a candidate's understanding of state management in React and their ability to create dynamic and interactive UI components that respond to user actions and data changes.

Lifecycle Methods: Lifecycle Methods in React are special methods that are automatically called at specific points during a component's lifecycle, such as when it is mounted or updated. They provide hooks for performing tasks like fetching data, subscribing to events, or updating the component's state. This skill should be measured in the test to assess a candidate's familiarity with the lifecycle methods in React and their ability to utilize them effectively to control and manage component behavior.

Handling User Input with Forms and Events: Handling User Input with Forms and Events involves capturing and processing user input in React. This skill should be measured in the test to evaluate a candidate's ability to create controlled form components, handle form submissions, and respond to user events such as clicks, key presses, and mouse movements.

Making API Requests with React: Making API Requests with React involves fetching data from external APIs and integrating it into React components. This skill should be measured in the test to assess a candidate's knowledge of using tools like the Fetch API or Axios to make asynchronous requests, handle responses, and update component state with the retrieved data.

Building Lists of Records: Building Lists of Records in React refers to rendering dynamic lists of items based on data. This skill should be measured in the test to evaluate a candidate's ability to map over an array of data, generate dynamic list components, and render them efficiently in React.

Using Refs for DOM Access: Using Refs for DOM Access allows direct access to the underlying DOM elements in React components. Refs provide a way to interact with the DOM imperatively, such as obtaining the value of an input field or triggering a focus event. This skill should be measured in the test to assess a candidate's understanding of refs and their ability to use them effectively for DOM manipulation and access.

Understanding Hooks in React: Understanding Hooks in React is about utilizing the Hooks feature introduced in React to write functional components with state and lifecycle features. Hooks provide a way to use React features like state and lifecycle methods in functional components, making them more easy to write, understand, and test. This skill should be measured in the test to evaluate a candidate's familiarity with Hooks and their ability to leverage them to build functional, stateful components in React.

Component and Route Navigation: Component and Route Navigation in React involves managing the navigation and routing within a React application. This skill should be measured in the test to assess a candidate's understanding of React Router or other routing libraries, and their ability to navigate between different components or routes based on user interactions or programmatic logic.

Deploying a React App: Deploying a React App means making a React application available to users by deploying it to a hosting platform or server. This skill should be measured in the test to evaluate a candidate's knowledge of the deployment process for React applications, including build optimization, environment configuration, and deployment strategies.

Integrating React with State management libraries: Integrating React with state management libraries involves using libraries like Redux or MobX to manage the global state of a React application. This skill should be measured in the test to assess a candidate's familiarity with state management concepts and their ability to integrate and utilize state management libraries in React applications to manage complex data flows and shared state.

Handling Authentication with React: Handling Authentication with React involves implementing user authentication and authorization in a React application. This skill should be measured in the test to evaluate a candidate's ability to implement authentication flows, handle user sessions, protect routes, and securely manage user credentials and authentication tokens within a React application.

Using the Context System with React: Using the Context System with React allows sharing data or state between components without passing props through every level of the component tree. Context provides a way to access a value or state from any component within the context tree. This skill should be measured in the test to assess a candidate's understanding of the Context API in React and their ability to utilize it to share data and manage application-wide state in a more efficient and scalable way.

Get started for free

Preview questions

Make informed decisions with actionable reports and benchmarks

View sample scorecard

Screen candidates in 3 easy steps

Pick a test from over 500+ tests

The Adaface test library features 500+ tests to enable you to test candidates on all popular skills- everything from programming languages, software frameworks, devops, logical reasoning, abstract reasoning, critical thinking, fluid intelligence, content marketing, talent acquisition, customer service, accounting, product management, sales and more.

Invite your candidates with 2-clicks

Make informed hiring decisions

Get started for free

Preview questions

Try the most advanced candidate assessment platform

ChatGPT Protection

Non-googleable Questions

Web Proctoring

IP Proctoring

Webcam Proctoring

MCQ Questions

Coding Questions

Typing Questions

Personality Questions

Custom Questions

Ready-to-use Tests

Custom Tests

Custom Branding

Bulk Invites

Public Links

ATS Integrations

Multiple Question Sets

Custom API integrations

Role-based Access

Priority Support

GDPR Compliance

Pick a plan based on your hiring needs

The most advanced candidate screening platform.
14-day free trial. No credit card required.

From

$15

per month (paid annually)

View pricing plans

With Adaface, we were able to optimise our initial screening process by upwards of 75%, freeing up precious time for both hiring managers and our talent acquisition team alike!

Brandon Lee, Head of People, Love, Bonito

It's very easy to share assessments with candidates and for candidates to use. We get good feedback from candidates about completing the tests. Adaface are very responsive and friendly to deal with.

Kirsty Wood, Human Resources, WillyWeather

We were able to close 106 positions in a record time of 45 days! Adaface enables us to conduct aptitude and psychometric assessments seamlessly. My hiring managers have never been happier with the quality of candidates shortlisted.

Amit Kataria, CHRO, Hanu

We evaluated several of their competitors and found Adaface to be the most compelling. Great library of questions that are designed to test for fit rather than memorization of algorithms.

Swayam Narain, CTO, Affable