List of the Best 21 Interview Questions for Node JS Developers in 2023

If you’re preparing for an interview that involves Node.js, it’s a good idea to familiarise yourself with common questions that could be asked. Some examples of typical interview questions revolving around Node.js are: • Can you detail your experience working with Node.js? • What previous experience do you have using Node.js? • In what ways have you encountered obstacles when utilising Node.js? • How do you debug Node.js applications? • What exactly is Node.js’ event loop? • What purpose do Node.js modules serve? • Are you familiar with npm and its usage? • How do you deal with asynchronous code in Node.js? • What exactly is Node.js streaming? Taking the time to review and practise your responses to these questions will undoubtedly make you better prepared for the interview process. Additionally, conducting thorough research on the company and your particular role can further improve your chances. Node.js is a widely used server-side environment for JavaScript that’s commonly used for creating web applications due to its high scalability, speed, and minimal overhead. It’s a great choice for projects that need to handle large amounts of traffic, such as online gaming and chat applications, as well as for constructing RESTful APIs.

Looking for answers to the aforementioned questions? Well then, let’s start from the very beginning.

To put it differently, what exactly is the purpose of Node JS?

Node JS utilises the V8 engine to run JavaScript code outside of a browser, which essentially renders it a cross-platform, open-source solution. You can visit the Node JS website to learn more.

Common Job Interview Questions for Node JS Positions

  1. What makes Node JS so popular?

    Node JS is extremely effective in handling high throughputs and large amounts of concurrent requests due to its single-threaded event loop and non-blocking I/O operations. Moreover, it can be deployed on any compatible web server thanks to its HTTP module.
  2. What is the reason behind Node JS not being multi-threaded?

    Node JS employs a single-threaded architecture to enable asynchronous processing, which can lead to better performance and the ability to handle more concurrent users than traditional thread-based designs. Due to the use of asynchronous processing, Node JS forgoes the conventional multi-threaded approach, allowing more efficient utilisation of resources and maximising processing power.
  3. Can you explain the meaning of terms “asynchronous” and “non-blocking”?

    1. Asynchronous:

      When two or more events lack synchronisation, they are known as “asynchronous.” Asynchronous querying, which refers to the ability to make HTTP requests without waiting for a response from the server, is made possible by this feature. These actions are taken in response to a request for which a response from the server has already been received.
    2. Non-blocking operations:

      Non-blocking procedures are engineered to handle all I/O requests efficiently by promptly reacting to any available information while continuing to function as expected. If an application programming interface (API) is unable to retrieve a response, an error will be immediately issued.
  4. Can you explain what REPL means?

    REPL stands for “Read, Evaluate, Print, and Loop,” and it is an interactive environment similar to a simulated window terminal or Unix/Linux shell, where users can enter commands that will be responded to with an output by the system. Node.js has a pre-configured and ready-to-use REPL environment.

    REPL is capable of performing the following operations:
    1. Read:

      The “Read” function receives data from the user, formats it in a JavaScript data structure, and stores it in RAM.
    2. Evaluate:

      The “Evaluate” function accepts the data structure and examines it.
    3. Print:

      The output of the operation is printed out.
    4. Loop:

      The “Loop” function executes the specified command repeatedly until the user presses the CTRL+C keys twice.
  5. Can you provide an example of how Node JS’s “Control Flow” manages function calls?

    The instructions are as follows:
    1. Manage the timing of events.
    2. Acquire information.
    3. Maintain a small number of active processes.
    4. Kindly proceed with the following stage of the program.
  6. Can you provide a list of the Node JS Long Term Support (LTS) versions?

    All critical security, performance, and bug fixes are applied to the Node JS Long Term Support (LTS) versions. These versions have the utmost stability and security, and are ensured to be maintained and supported for at least 18 months.

    LTS releases are only updated with bug fixes, security patches, new versions of npm and documentation, and sometimes minor performance optimizations.
  7. Note: Keywords like “Node JS Long Term Support (LTS) versions” and “npm” can be hyperlinked to their relevant webpages.
  8. How extensively does Node JS utilize middleware?

    The Middleware function is given two parameters: the Request and Response objects. These objects give the Middleware access to various associated request and response objects, as well as an additional variable that represents the subsequent function in the request-response cycle of an application.

    The most frequent roles of middleware are: Note: The keywords “Node JS” and “Middleware” can be hyperlinked to relevant sources.
    1. Various codes can be executed.
    2. Edit both the request and response objects.
    3. Terminates the request-response cycle.
    4. Invoke the next layer of intermediary software.
  9. What is ESLint?

    ESLint is a free and open-source software project introduced in 2013 by Nicholas C. Zakas. It functions as a plug-in linting tool for JavaScript. This form of linting is valuable, particularly in Node JS, where it helps to find bugs related to variable scope.
  10. Note: Keywords such as “ESLint,” “Node JS,” “plug-in linting tool,” and “variable scope” can be hyperlinked to their relevant sources.
  11. What led Google to select the V8 engine for building Node JS?

    Google opted for the V8 engine because it contains an internal runtime engine that can convert JavaScript to native machine code.
  12. Note: Keywords like “Google,” “V8 engine,” and “JavaScript” can be linked to their respective sources.
  13. Understanding Stubs in Node JS

    Stubs are programs or methods in Node.js that mimic the actions of a module or component. They provide predetermined responses to the functions being tested, which helps developers test their code without relying on the actual module or component. With stubs, developers can examine the code they’ve written while keeping its behaviour separate from that of other modules and components.
  14. Note: Keywords like “Node JS,” “stubs,” and “module or component” can be hyperlinked to the relevant sources for better understanding.
  15. Can you explain the Node JS buffer class?

    The Node.js Buffer class is a helpful collection of integers used to hold raw data. It differs from a V8 heap dilemma since it is responsible for allocating raw memory. This global class is highly intuitive and can be accessed from anywhere in the world, allowing applications to leverage buffer benefits without needing a separate buffer module.
  16. Note: Keywords such as “Node JS,” “buffer class,” and “V8 heap issue” can be hyperlinked to their respective sources.

Challenging Interview Questions for Node JS Specialists

  1. What are the characteristics of a package.json?

    Documentation for a project should include all pertinent details, such as the name, version, summary, homepage, author, contributors, dependencies, repository type and URL, main entry point, and keywords.
  2. Note: Keywords like “package.json” and “project documentation” can be hyperlinked to relevant sources.
  3. What is an error-first callback in Node JS?

    To confirm that the code is functioning as intended, we need to ensure that it has executed without any problems. For this reason, we use error-first callbacks. These callbacks first report any errors that may have occurred and then provide relevant information thereafter.
  4. Note: Keywords like “Node JS” and “error-first callback” can be hyperlinked to relevant sources.
  5. What is npm?

    Npm stands for Node Package Manager. Here are two primary uses of npm:
    1. Online libraries such as Node JS packages and modules which are searchable can be accessed through
    2. Version control for Node JS packages, a command-line installation tool, and dependency management.
  6. What is the purpose of Node JS’s assert function?

    The Assert module in Node.js simplifies the creation of test cases. Developers can execute tests without receiving any results until an error occurs. This module provides a simple set of assertion tests that can be used to verify invariants. Node.js initially created it for internal purposes, but other applications can also utilise it via the ‘require(‘assert’)’ command.

    Here’s an example of the syntax:
    Assuming you have the following code:
    var assert = require(‘assert’);
    use the a+b+c function to add (a+b)
    invert (a + b)
    In essence: var expected = add(1,2);
    if (expectation === 3, “one plus two equals three”), then
  7. Note: Keywords like “Node JS,” “assert function,” “Assert module,” and “test cases” can be hyperlinked to relevant sources.
  8. What is Node JS’s equivalent of Punycode?

    Software engineers may use Punycode encoding syntax to transform a Unicode (UTF-8) string of characters into an ASCII string of characters.

    Starting with version 0.6.2 of Node.js, Punycode is included as a standard feature. If you want to use Punycode with earlier versions of Node.js, you need to install the module using the Node Package Manager (npm) first. To obtain access to Punycode, simply use the command “require(‘Punycode’)”.

    Here’s an example syntax:
    punchcode = require(“punycode”);
  9. Note: Keywords like “Node JS,” “Punycode,” and “Node Package Manager” can be hyperlinked to relevant sources.
  10. What does “EventEmitter” mean in Node JS?

    In Node.js, all objects that are capable of emitting events belong to the class EventEmitter. The ‘eventEmitter.on()’ method is used to attach the specific events to the object. As a result, every time the object emits an event, the attached functions are synchronously called.

    Here’s an example:
    EventEmitter const = require(“events”);
    Class MyEmitter extends EventEmitter
    myEmitter = new MyEmitter(); const
    MyEmitter.on(“event”, (), ” => “
    Meaning, console.log(“something happened!”);
  11. Note: Keywords such as “Node JS,” “EventEmitter,” and “eventEmitter.on()” can be hyperlinked to relevant sources.
  12. What is the purpose of Node JS’s crypto module?

    The crypto module in Node.js provides users with cryptographic capabilities. This module facilitates various cryptographic operations such as data encryption and decryption, document signing, and data hashing. The crypto module contains easy-to-use wrappers for these operations, making them convenient to perform.
  13. Note: Keywords such as “Node JS,” “crypto module,” “cryptographic operations,” and “data hashing” can be hyperlinked to relevant sources.
  14. For those who are not familiar with Node JS, what is a “passport”?

    Passport is a widely-used middleware that comes pre-installed in Node JS. It is typically employed to provide authentication support and can be seamlessly integrated into any Express.js-based web application. With its simple integration process, Passport enables developers to quickly and securely authenticate users in their applications.
  15. Note: Keywords such as “Node JS,” “passport,” “authentication,” “Express.js,” “middleware,” and “web application” can be hyperlinked to relevant sources.
  16. How does Node JS’s DNS lookup feature work?

    When a web address is entered into a DNS lookup service, it returns an IPv4 or IPv6 record.

    Depending on various factors, such as the options provided, the required input type may be an object or an integer. If no value is specified in the designated field, both Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) will be used. Additionally, the third argument of the callback function should be passed directly to the callback function itself.

    Here is an example syntax:
    dns.lookup(address, options, callback) (address, options, callback)
  17. Note: Keywords such as “Node JS,” “DNS lookup,” “IPv4,” “IPv6,” and “callback function” can be hyperlinked to relevant sources.
  18. What is the purpose of the “module.exports” concept in Node JS?

    Using the ‘module.exports’ function, two previously inaccessible functions are made accessible and given a practical context. Modules are objects that are utilised to compile related code snippets into a coherent and unified database operation-like unit.
  19. Note: Keywords such as “Node JS,” “module.exports,” “functions,” and “database operation” can be hyperlinked to relevant sources.

Where do you start with interview questions about Node JS?

Node JS is used as a server-side technology by organisations of all sizes worldwide, making it a valuable skill for anyone considering a career change. To excel in a job interview, it is crucial to dedicate time to hone and enhance your interview skills prior to the interview. This will give you the best opportunity for success and boost your confidence.

Note: The term “Node JS” could be hyperlinked to a relevant website.

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Note: Keywords such as “remote work,” “competitive salary,” “job opportunities,” “React,” “Node,” “Python,” “Angular,” “Swift,” “React Native,” “Android,” “Java,” “Rails,” “Golang,” “DevOps,” “ML,” and “Data Engineers” can be hyperlinked to relevant sources. The company name, “Works,” has already been hyperlinked.


  1. What are some common uses of Node JS?

    Node.js is a run-time environment for JavaScript that operates with a single thread and is driven by events. It is increasingly popular in the development of real-time, push-based applications. However, Node.js is not limited to this purpose and can be used for other purposes, such as creating static websites and backend APIs. Node.js has proven to be effective for such applications due to its event-driven programming style and non-blocking I/O model.
  2. Note: Keywords such as “Node JS,” “run-time environment,” “JavaScript,” “real-time,” “push-based applications,” “static websites,” “backend APIs,” “event-driven programming style,” and “non-blocking I/O model” can be hyperlinked to relevant sources.
  3. What are some common interview questions for Node.js?

    Here are some typical interview questions for Node.js:
    1. What is the function of Node.js?
    2. What makes Node.js such a widely-used technology?
    3. What is the reason behind Node.js not being a multi-threaded technology?
    4. What do the words “asynchronous” and “non-blocking” mean in relation to Node.js?
    5. Can you provide an explanation of what REPL entails?
  4. I have a NodeJS interview scheduled; how can I prepare?

    Being well-prepared for a NodeJS interview is crucial. To do so, you must have a comprehensive understanding of the framework. This includes knowledge of setting up the system on both Windows and Linux, the event loop, the operating system, the path, the URL, the domain name system, the network, the REPL, the package manager, the callbacks, the UDP, the process, the query string, the cryptography, the debugger, the file systems, the global objects, the child processes, the buffers, the streams, and the web modules. Developing expertise in all of these areas will help you succeed in the interview.
  5. Note: Keywords such as “NodeJS,” “interview,” “framework,” “Windows,” “Linux,” “event loop,” “operating system,” “path,” “URL,” “domain name system,” “network,” “REPL,” “package manager,” “callbacks,” “UDP,” “process,” “query string,” “cryptography,” “debugger,” “file systems,” “global objects,” “child processes,” “buffers,” “streams,” and “web modules” can be hyperlinked to relevant sources.

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