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

Are you preparing for an upcoming interview related to Node.js? If so, familiarising yourself with commonly asked questions can help you to be better prepared. Some typical interview questions for Node.js could include: • What experience do you have working with Node.js? • How have you used Node.js in the past? • What challenges have you faced while working with Node.js? • How do you debug Node.js applications? • What is an event loop in Node.js? • What is the purpose of Node.js modules? • Are you familiar with npm and how to use it? • How do you handle asynchronous code in Node.js? • What is streaming in Node.js? To be prepared for the interview, it is important to take the time to review these questions and think through your responses. Additionally, it can be beneficial to research the role you are applying for and find out more about the company. Node.js is a server-side JavaScript environment which is often used for developing web applications. It is popular for its scalability, speed, and low overhead, making it a great choice for enterprise application development. Node.js is often used for building real-time web applications, such as chat applications and online gaming platforms, as well as for building RESTful APIs.

In search of explanations to the above queries? Okay, let’s start from the beginning.

In other words, what does Node JS do?

In order to execute JavaScript code outside of a web browser, Node JS uses the V8 engine, which makes it a cross-platform, open-source solution.

Standard Node JS Job Interview Queries

  1. Why is Node JS so popular?

    Due to its single-threaded event loop and non-blocking I/O operations, Node JS is equipped with the ability to handle very high throughputs and a significant amount of concurrent requests. Furthermore, its HTTP module allows it to be deployed on any compatible web server.
  2. Why is Node JS not multi-threaded?

    Node.js utilises a single-threaded architecture to enable asynchronous processing. This type of processing can result in improved performance and the ability to accommodate more concurrent users than traditional thread-based designs would allow. Asynchronous processing enables Node.js to use a single-threaded paradigm instead of the more conventional approach, allowing for a more efficient utilisation of resources and making the most of the available processing power.
  3. Define the terms asynchronous and non-blocking.

    1. Asynchronous:The term “asynchronous” describes the lack of synchronisation between two or more events. This function enables us to make HTTP requests without having to wait for a response from the server, which is commonly known as asynchronous querying. These actions are performed in response to a request for which a reply from the server has already been obtained.
    2. Non-interfering operations:Non-blocking procedures are designed to handle all I/O requests efficiently, quickly reacting to any available information and continuing to operate as expected. Should the application programming interface (API) be unable to acquire a response, an error will be immediately returned.
  4. Please explain what REPL is.

    Node.js’s REPL stands for “Read, Evaluate, Print, and Loop”. This term is used to refer to an interactive environment, similar to a simulated window terminal or Unix/Linux shell, where users can input commands and the system will respond with an output. Node.js already comes with a REPL environment pre-configured and ready to use.

    REPL is capable of the following operations:
    1. Read:Takes data from the user, formats it in a JavaScript data structure, and saves it in RAM.
    2. Eval:Takes in the data structure and analyses it.
    3. Print:The final result is printed.
    4. Loop:Repeats the specified command until the user presses the CTRL+C keys twice.
  5. Give an example of how Node JS’s “Control Flow” manages calls to functions.

    Instructions are as follows:
    1. Manage the timing of deaths.
    2. Get information
    3. Keep the number of active processes low.
    4. Please initiate the next stage of the program.
  6. Please list the Node JS Long Term Support (LTS) versions.

    All security, performance, and bug fixes that are deemed critical are installed on the Node JS Long Term Support (LTS) version. These versions have the highest priority in terms of stability and security, and are guaranteed to be maintained and supported for a minimum of 18 months.

    LTS releases are only updated with bug fixes, security patches, new versions of npm and documentation, and sometimes minor performance tweaks.
  7. To what extent does Node JS make use of middleware?

    The Middleware function is passed two arguments, namely the Request and Response objects. During the request-response cycle of an application, these objects provide the Middleware access to various related request and response objects, as well as an additional variable that is used to represent the cycle’s subsequent function.

    The most common tasks performed by middleware are:
    1. Codes of all kinds may be run.
    2. Modify both the request and response objects
    3. Put an end to the request-response loop.
    4. Call up the following layer of software intermediaries
  8. ESLint is…

    In 2013, Nicholas C. Zakas created ESLint, a free and open-source software project developed to serve as a plug-in linting tool for JavaScript. This type of linting is especially useful in Node JS, where it can be used to detect bugs related to the variable scope.
  9. When developing Node JS, why did Google choose the V8 engine?

    With V8, a runtime engine built into Chrome, Google is able to convert JavaScript into native machine code.
  10. Stub in Node JS: An Explanation

    In Node.js, stubs are simply programs or methods used to imitate the functioning of a module or component. They provide pre-defined responses to the functions being tested, thereby allowing developers to test the code without having to rely on the actual module or component. By using stubs, developers are able to test the code they have written while isolating its behaviour from the behaviour of other modules and components.
  11. Could you perhaps elucidate the Node JS buffer class?

    The Node.js Buffer class serves as a convenient collection of integers, and is used to store raw data. It is distinct from a V8 heap issue, since it deals with allocating raw memory. This global class is extremely user-friendly and accessible from any location around the world, allowing applications to take advantage of the advantages of buffers without having to load a distinct buffer module.

Tough Interview Questions for Node JS Experts

  1. Tell me about the characteristics of a package.json

    It is essential that all relevant information pertaining to a project is included in the documentation, such as the name, version, summary, homepage, author, contributors, list of dependencies, repository type and URL, main entry point, and keywords.
  2. In Node JS, what does an error-first callback mean?

    In order to ensure that the code is running as expected, we must verify that it has been executed without any issues. To address this, we utilise error-first callbacks. These callbacks first report any errors that have occurred and then provide any relevant information afterwards.
  3. Can you explain what npm is?

    Npm is an abbreviation for the Node Package Manager. Here are npm‘s two primary uses:
    1. Searchable online libraries including Node JS packages and modules; accessible through
    2. Node JS packages version control, an installation command line tool, and dependency management.
  4. To what end does Node JS’s assert function?

    The Node.js Assert module facilitates the creation of test cases. It allows developers to execute tests without providing any results until failure occurs. This module provides a straightforward collection of assertion tests, which can be utilised to verify invariants. Initially crafted for internal usage by Node.js, it can also be adopted in other applications, by utilising the ‘require(‘assert’)’ command.

    Here’s a Sample of the syntax:
    Assume that you have the following code:
    var assert = require(‘assert’);
    use the a+b+c function to add (a+b)
    invert (a + b)
    In a nutshell: var expected = add(1,2);
    if (expectation === 3, “one plus two equals three”) then
  5. Just what is Node JS’s equivalent of Punycode?

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

    As of Node.js version 0.6.2, Punycode is included as standard equipment. If you would like to use Punycode with earlier versions of Node.js, you must first install the module using the Node Package Manager (npm). To gain access to Punycode, simply use the command “require(‘Punycode’)”.

    Here’s some example syntax:
    punchcode = necessitate(“punycode”);
  6. In Node JS, what does “EventEmitter” mean?

    In Node.js, all objects which are capable of emitting events are grouped under the class EventEmitter. The ‘eventEmitter.on()’ method is utilised to attach the specified events to the object. As a result, whenever the object emits any event, the attached functions are called synchronously.

    Here’s an illustration:
    event emitter const = require(“events”);
    It’s clear that class MyEmitter extends EventEmitter
    myEmitter = new MyEmitter(); const
    MyEmitter.on(“event”, (), ” => “
    In other words, console.log(“something happened!”);
  7. To what end does Node JS’s crypto module cater?

    Node.js provides users with cryptographic capabilities through the use of its crypto module. This module enables users to perform a variety of cryptographic operations, including encryption and decryption of data, signing of documents and hashing of data. The crypto module provides convenient wrappers that make these operations easy to accomplish.
  8. For those unfamiliar with Node JS, what exactly is a “passport”?

    Passport is a popular middleware that is pre-installed in Node JS. It is commonly used to provide authentication support, and can easily be integrated into any Express.js-based web application. With its straightforward integration, Passport allows developers to quickly and securely authenticate users within their applications.
  9. Can you explain how Node JS’s DNS lookup feature operates?

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

    Depending on other factors, such as the options presented, the type of input that is required may be either an object or an integer. If no value is provided in the designated box, both Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) will be utilised. Additionally, the third argument of the callback function should be sent directly to the callback function itself.

    Here’s some example syntax:
    dns.lookup(address, options, callback) (address, options, callback)
  10. Why does Node JS have a concept called “module.exports”?

    By employing the ‘module.exports’ function, two functions that were previously inaccessible are made accessible and are given a practical context. Modules are objects that are used to compile related snippets of code into one cohesive unit. This approach can be thought of as analogous to a unified database operation.

When it comes to Node JS interview questions, where do you even begin?

Organisations of all sizes across the globe are leveraging Node JS as a server-side technology, making it an invaluable skill to have for anyone considering a career change. To be well-equipped for a job interview, it is essential to take the time to sharpen and refine your interview skills ahead of time. Doing so will provide you with the best chance of success and increase your confidence.

Are you looking for a reputable US firm that allows you to work remotely and receive a competitive salary? Look no further than Works. Works offers a wide selection of job opportunities in various fields, such as React, Node, Python, Angular, Swift, React Native, Android, Java, Rails, Golang, DevOps, ML, Data Engineers, and more. Search and apply to the job that is right for you today at Works.


  1. To what end is Node JS often put to use?

    Node.js is a single-threaded, event-driven JavaScript runtime environment, which has become increasingly popular for the development of real-time, push-based applications. However, Node.js is not limited to this purpose, and can be employed for a variety of uses, including the creation of static websites and back-end APIs. Node.js has proven to be an efficient tool for such applications, due to its non-blocking I/O model and event-driven programming style.
  2. What are some typical interview questions for Node.js?

    A few typical Node JS interview questions are as follows:
    1. In other words, what does Node JS do?
    2. Why is Node JS so popular?
    3. Why is Node JS not multi-threaded?
    4. The terms “asynchronous” and “non-blocking” need to be defined.
    5. Please explain what REPL is.
  3. I have an interview with Node scheduled; what should I do to be ready?

    It is important to be well-prepared for an upcoming NodeJS interview. To do so, you should become familiar with the framework in its entirety, which includes knowledge of how to set 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. Becoming knowledgeable in all of these elements will help you be successful in the interview.

Join the Top 1% of Remote Developers and Designers

Works connects the top 1% of remote developers and designers with the leading brands and startups around the world. We focus on sophisticated, challenging tier-one projects which require highly skilled talent and problem solvers.
seasoned project manager reviewing remote software engineer's progress on software development project, hired from Works blog.join_marketplace.your_wayexperienced remote UI / UX designer working remotely at home while working on UI / UX & product design projects on Works blog.join_marketplace.freelance_jobs