A survey conducted by Stack Overflow in 2021 revealed that React was the most popular front-end web framework among front-end developers, with over 56% of respondents reporting that they had used it before. Similarly, a report published by GitHub in 2020 showed that React was the third most popular project on the platform, after only VS Code and Flutter, which clearly shows its wide adoption in the software development community.
Today we will discuss how to design ReactJS-specific assessments for hiring developers. First, we will go through guidelines for setting up the test and code assignments. Then we will go through fundamental questions related to the ReactJS architecture. In the end, we will share a coding exercise to test the candidate’s skills and programming capabilities in ReactJS.
General Tips for Designing the Test
Before we discuss a ReactJS-specific technical assessment, let’s go through some of the basic guidelines for setting up a technical assessment regardless of the programming language.
Setting the Same Level of Difficulty
By keeping the difficulty level of questions the same, you can ensure that all candidates get an equal chance to showcase their skills and are evaluated on a level playing field. It not only makes the comparison easy for technical managers but also ensures that the evaluation process is fair and unbiased.
Allowing the Same Amount of Time for Code Assignments
For a programmer, it’s crucial to be able to finish tasks within a set deadline. By giving each candidate the same amount of time to complete the code challenges, the interviewer can gauge how well each one performs under time constraints and pressure.
Figure 1 – CodeInterview allows to share the same test with multiple candidates through a URL, ensuring all candidates face the same difficulty level and same time duration to complete the test.
Plagiarism Detection
It is very common these days to copy code solutions from sites such as StackOverflow. To ensure that the candidate has solved the coding challenge without copying the solution from somewhere, it is essential to apply a plagiarism check on the candidate’s code. That will help differentiate a bad nut from a good one.
Hide Applicant Personal Details
Keeping an applicant’s personal details hidden from the evaluator can reduce the chances of bias based on factors such as religion, race, gender, and other personal characteristics. The online tool used for technical hiring should have the feature to hide personal details. This way, hiring managers are less likely to be influenced by conscious or unconscious biases. Also, this increases the chances to focus on the candidate’s technical skills and experience instead of their personal attributes.
Want to learn more about designing code challenges? Check out this article for other best practices.
Essential concepts of ReactJS for Assessing candidates
JSX
JSX is a syntax extension for JavaScript through which ReactJS programmers write HTML-like code in JavaScript files. It is an essential concept for building React applications. JSX makes it easy for developers to create and manage dynamic UI components. Some of the JSX questions that technical managers should be asking candidates are the following:
- Q1: Can you explain the process of JSX compilation into regular JavaScript, and what is the role of Babel in this process?
- Q2: Elaborate on how JSX allows you to create custom components, along with some examples of custom components from your previous projects.
- Q3: Provide an example of how you might use conditional rendering in JSX, either through a ternary operator or an “if” statement.
ReactJS Components
ReactJS components are building blocks that contain both the business logic and presentation. Developers can reuse these components in different areas across an application. Some common examples of ReactJS components are buttons, lists, tables, forms, charts and modals. Sound knowledge of ReactJS components is necessary for developers to build scalable, maintainable, and reusable code.
Here are some of the questions on ReactJS components that you can ask programmers:
- Q1: Explain the lifecycle methods of a ReactJS component and which methods you have used in your projects.
- Q2: What are some of the challenges you have faced when working with ReactJS components, and how did you address them?
- Q3: How do you test a ReactJS component, and what are some best practices for testing a ReactJS component?
ReactJS State
ReactJS State is a data structure containing information about how a component behaves, interacts with the user, and how it is rendered on the screen. State is a fundamental concept in ReactJS and it is critical for developers to understand it in order to create responsive and sophisticated user interfaces.
Find below some of the questions which you can ask to assess a programmer’s ability in ReactJS state management:
- Q1: How to initialize state in a ReactJS component, and what best practices you follow in your project?
- Q2: How do you pass state data between two components, and what are the different ways to do that?
- Q3: what is the difference between local state and global state, and which ones have you used in your projects?
Lifecycle Methods
ReactJS lifecycle methods are called at various points during the lifecycle of a component, allowing developers to perform different tasks at each point. A thorough understanding of life cycle methods is necessary for developers to optimize the performance of their applications and manage state changes.
Let’s go through some of the questions which can help you assess a programmer’s ability to understand the life cycle methods of ReactJS:
- Q1: What are the different phases of the ReactJS component lifecycle, and what methods are executed in each phase?
- Q2: What are some frequent use cases for life cycle methods, and which ones have you implemented in your projects?
- Q3: Elaborate the difference between state and props in a ReactJS component, and how are they related to the component life cycle methods.
Routing
Routing is a way of managing the navigation and flow of a ReactJS application by mapping different URLs to specific UI components. Routing is an important concept in ReactJS and it allows developers to create a single-page application with dynamic screens where different content is displayed without needing to refresh the whole page.
Some important questions to evaluate a programmer’s knowledge of routing are as below:
- Q1: What is the difference between server-side routing and client-side routing? In your projects, which one do you use?
- Q2: How do you create routes in ReactJS, and what information should be part of the route definition?
- Q3: How do you handle dynamic routing and pass parameters to components in ReactJS?
Security
Security in ReactJS refers to different practices and techniques used to combat the risks and safeguard against malicious attacks, including cross-site scripting (XSS) and cross-site request forgery (CSRF). It is inevitable for any ReactJS developer to understand different security aspects to be implemented in a ReactJS application, as web applications are often the target of malicious attacks while vulnerabilities in the code can expose sensitive user data.
Find below some of the questions to assess a ReactJS developer’s expertise in security:
- Q1: Give an example of cross-site scripting (XSS) and what measures did you take in your projects to prevent it?
- Q2: Give an example of cross-site request forgery (CSRF) and what measures did you take in your projects to prevent it?
- Q3: Based on your experience, what are some of the best practices for secure authentication and authorization in a ReactJS application?
Coding Challenge for ReactJS Programmers
Here is a ReactJS coding challenge that tests all the major concepts, including security, life cycle methods, state management, routing, components and JSX.
Create a web application with a login page and a dashboard page. The dashboard should display the user’s profile information and a list of the user’s recent transactions. You can use a JSON file or a static JavaScript object for mock data. Implement the following features in the application:
1. Implement user authentication using a secure token-based authentication such as JWT. Without login, the user should not be able to see the dashboard.
2. Create a functional component that displays the user’s profile information. This component should receive the user’s information as props and use it to display the profile information in JSX.
3. This component should use the “useState” hook to store the transaction data in state, and use the “useEffect” hook to fetch the transaction data from the mock data source when the component is mounted.Implement the logout functionality in the application. When the user logs out, their authentication token should be destroyed.
4. Implement the logout functionality in the application. When the user logs out, their authentication token should be destroyed.
5. Make sure to sanitize and validate user inputs to prevent injection attacks.
6. Implement a route guard that requires the user to be successfully authenticated before they can view their dashboard. If the user is not authenticated, they should be redirected to the login page.
7. Add a feature that allows the user to modify their profile information. A form should be displayed through which users can update their name, email address, and password. Use JSX to render the form in the component. Submitting the form will update the profile information in the parent component’s state.
8. Add a feature through which users can view the details of a particular transaction. Clicking on a transaction should take the user to a route that displays the details of the transaction. Use the “useState” hook to store the transaction details in state, and use the “useEffect” hook to fetch the details of the transaction from the mock data source when the component is mounted.
9. Implement proper error handling in the code.
Summary
Today we discussed how to design a React technical assessment in detail. We went through the different building blocks of ReactJS and shared different questions for evaluating candidates for ReactJs programming roles. We also presented a comprehensive coding exercise to assess React programmers’ programming skills.
The role of an online code assessment tool is integral to technical hiring. When selecting an online tool for technical evaluation of developers, make sure that it has strong integration with different programming languages and frameworks. CodeInterview, for example, has a built-in integration with all modern programming languages, including ReactJS.
Figure 2 – CodeInterview IDE provides built-in integration with top programming languages, including ReactJS. Learn more in a free trial.