Most frequently asked Node.js interview questions

Node.js interview questions

Node.js-related jobs are constantly appearing in the job postings of leading technology companies. To seize this opportunity, candidates need to prepare carefully before entering a Node.js interview, especially for advanced Node.js interview questions.

Outlined below are the Node.js interview questions thoughtfully segregated into two distinct formats: basic and advanced, providing candidates with a valuable resource that can be stored for convenient and systematic practice, enabling them to fortify their understanding and proficiency in Node.js concepts and effectively prepare for the demands of upcoming interviews in this domain.

Basic Node.js Interview Questions

  • What is Node.js?

Node.js is a runtime environment built on JavaScript, capable of handling multiple concurrent connections in real-time applications or high-performance multi-user applications. Furthermore, Node.js reduces the overhead and enhances collaboration among team members by using the same language on both the server and the client side. Node.js is highly suitable for developing server-side and real-time networking applications.

  • Explain Callback in Node.js and how to handle Callback hell.

Callback is a function that is passed as an argument to another function and is called after the function that contains it completes its processing or an event occurs. This allows for asynchronous processing, such as reading files, sending HTTP requests, or connecting to databases, to continue without waiting for the return value.

Callback hell occurs when a large number of callbacks are nested and become unreadable or unmanageable. At this point, Promises can be one of the solutions to reduce Callback hell. Promises allow us to arrange asynchronous operations in a more readable way and control error handling.

Node.js interview questions

  • Express in Node.js: What is it? The difference between Route and Router

Express in Node.js is a powerful and popular web framework, used to build web applications and APIs easily and quickly. Express provides powerful features and tools for managing HTTP requests, handling user interactions, and creating a variety of web applications.

In Express, a route is a mechanism for defining how an application handles HTTP requests from the user on specific URL paths. Each route is a different path, and is a specific action that the application will perform when the user accesses that path. Conversely, a Router is a part of Express that helps define multiple routes and how they are organized.

  • What is Middleware in Express? Give an example of how it works.

Middleware in Express is a software intermediary mechanism that allows you to perform processing before or after an HTTP request goes through the endpoints or routes of your web application. A popular example of middleware in Express is Morgan. It is very useful for tracking and debugging applications, especially when you need to see detailed information about the request and response to work with errors or improve the performance of your application.

  • What is LoopBack in Node.js? How does it differ from Express?

LoopBack is a framework built on top of Express but focuses on building APIs. LoopBack provides more advanced features to quickly build API applications, including user management, authentication, and data modeling.

Preparing for basic Node.js interview questions and comprehensively mastering the fundamental concepts not only demonstrates your commitment to foundational knowledge but also showcases your ability to address essential aspects of Node.js development. Additionally, augmenting your interview readiness with a thorough understanding of advanced Node.js topics not only signifies the depth of your expertise but also illuminates your capacity to tackle sophisticated challenges and complexities inherent in advanced Node.js development scenarios. By encompassing both basic and advanced areas of Node.js expertise, you can portray your versatility, adaptability, and readiness to excel in diverse and demanding professional environments, thereby leaving a lasting and positive impression on potential employers.

Node.js interview questions

Advanced Node.js Interview Questions

  • How to manage dependencies in a Node.js project and check for dependency updates?

You can use npm or yarn to manage dependencies in a project. Add the dependencies to the package.json file, then use the lock file (such as package-lock.json or yarn.lock) to ensure version consistency. To check for dependency updates, use npm outdated or yarn outdated to check for new versions and update with npm update or yarn upgrade as needed.

  • How to protect Node.js applications from common attacks such as Cross-Site Scripting (XSS) and SQL injection?

This is one of the advanced Node.js interview questions that employers choose to assess your problem-solving skills. If you encounter this question in a Node.js interview, you can provide more than one solution to “show off” your knowledge and skills.

In the case of XSS attacks, you can use a safe template engine such as Handlebars or EJS to render data. You can use a safe function such as Escape to display user data in HTML. Moreover, to control the sources uploaded to the website and prevent unsafe JavaScript code from being executed, you can use the HTTP Header Content Security Policy.

For SQL injection, we can use a built-in query library such as Knex.js to create a safe SQL query. You can use Prepare Statements to avoid passing user values directly into a SQL query. Or, pay attention to checking and processing user input data to remove or encode special characters that could cause attacks.

  • How to deploy Node.js applications to a production environment in a safe and efficient way?

Deploying Node.js applications to a production environment requires configuring the server, managing environment variables, using a process manager tool such as PM2 or systemd, setting up a proxy server (for example, Nginx), and applying HTTPS to secure data transmission. You need to design safe deployment processes and have the ability to back up and restore data.

These are the top most common and should be prepared before going to the Node.js interview. At the moment, SmartOSC is recruiting Node.js positions from Node.js fresher to Node.js Developer, please refer to SmartOSC Career for more information. Wish you soon find a job that suits your wishes!


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