18 Interview questions for Node.js Developers jobs


May 16, 24

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    Table of content
    Relinns Careers Website
  • Top Node.js developer interview questions
  • Conclusion 
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To be consistent, we will begin the article by reviewing the basic Node.JS developer job interview questions and answers that you can ask junior engineers. These questions can be requested at the start of the interview after the candidates introduce themselves.


First and foremost, this is an excellent strategy for getting to know the developer as a person. The way they respond to questions, stop and start thinking, and other minor nuances like this can reveal a lot about the Node.js developer, particularly the amount of effort they put into learning the subject.

Another reason why these fundamental Node.JS developer job interview questions are significant is that they allow you to assess your degree of Node.JS understanding. After considering the candidate's degree of qualification, you can pick what difficult questions to pose to the developers later.


In general, it's critical not to dismiss the fundamental questions just because they're "simple" or "unimportant." The truth is that the questions about entry-level Node.JS developers in the interview can be more essential than the advanced ones – in the end, they define the path of the rest of the interview.

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Top Node.js developer interview questions

Node.js is a modern server-side technology used by an increasing number of businesses. If you have a job interview, it is advised to brush up on your interview skills ahead of time. Although a few general Node.js developer interview questions are asked during all sorts of interviews, we recommend that you prepare by concentrating on questions relevant to your sector.

We've collected a comprehensive list of the most popular Node.js developer job interview questions and the best ways to answer them. It will help you comprehend the essential concepts of Node.js.

What exactly is Node.JS?

It is, without a doubt, the most fundamental question about Node.JS. Naturally, this is frequently the first or one of the first questions asked in an interview.

Even experienced Node.JS developers have difficulty answering this question smoothly. When developers are entirely immersed in Node.JS work, they do not always consider what it is. It is frequently difficult to define this tool in a single short line.

Node.JS is a JavaScript-based tool developed for internal development and implementation.

We may say that this is the most cost-effective version.

Why should we use Node.JS?

It is among the more subjective Node.JS developer job interview questions. The candidate should convey their thoughts on the instrument and its advantages. There are so many that the candidate will most likely discuss those that interest them or benefit them the most.

Here are some possible responses: It is quick, asynchronous, and offers a single, generalized programming language and data type, among other benefits.

Overall, Node.JS is one of the best tools for JavaScript-based server-side development.

How do you differentiate between front-end and back-end development?

One of those Node.JS questions may catch the developer off guard because it is unrelated to Node JS. It should be a simple question for developers. It all boils down to how they would phrase the response.

Front-end developers work on the web page's client (user) side. They work on, develop, and support everything that the client sees – in other words; they are in charge of the page's visual design and functional (for example, buttons, banners, and so on) components. On the other hand, back-end developers concentrate on activities that run in the background and are not visible to clients. They are likewise in charge of the site's functionality.

What are stubs?

Stubs are functions that replicate the functionality of specific modules. They are frequently used in tests since they can answer problems that may arise in the modules.

What are the advantages of using Node.js?

Node.js lets you create scalable network apps very quickly. Some of its advantages are as follows:

  • It is generally quick.
  • It is rarely obstructed.
  • It provides a single programming language and data type.
  • Everything is out of sync.
  • It produces a lot of concurrencies.

How does Node.js function?

A Node.js web server often has a unique process. Let's take a closer look at this process flow.

To interact with the web application, clients make requests to the webserver. Non Blocking or blocking requests are possible:

  • Searching for information
  • Updating and deleting data
  • Node.js collects incoming requests and queues them in the Event Queue.
  • The requests are then routed through the Event Loop one by one. It determines whether the recommendations are simple enough to necessitate using other resources.
  • The Event Loop handles simple requests (nonblocking actions) like I/O Polling and returns the results to the appropriate customers.
  • A single complex request is assigned a single thread from the Thread Pool. This thread is in charge of performing a specific blocked request by accessing external resources such as computers, databases, file systems, etc.
  • When the task is completed, the response is passed to the Event Loop, returning the answer to the client.

Why is Node.js a single-threaded language?

For async processing, Node.js is single-threaded. Instead of the conventional thread-based design, performing async processing on a single thread under typical site loads can improve performance and scalability.

How does Node.js manage the feature of concurrency if it has a single thread?

The Node.JS Platform does not use the Multi-Threaded Request/Response Stateless Model and instead uses the Single-Threaded Event Loop Model. The JavaScript Event-based model has significantly influenced the Node.JS Processing paradigm. As a result, Node.js can handle more concurrent client requests with ease. 

Describe the callback function in Node.js

A callback function is invoked upon the completion of a job. It permits other codes to continue in the meanwhile and avoids blocking. Node.js is an asynchronous platform that mainly relies on callbacks. Node's APIs are all designed to support callbacks.

What are the benefits of utilizing promises rather than callbacks?

Asynchronous logic's control flow is more detailed and structured.

  • The connection is minimal.
  • We've included error handling.
  • Readability has been improved.

What is your definition of I/O?

I/O refers to a program, process, or device that transports data to or from one media and to another.

Every transfer involves the output of one medium and the input of another. A physical device, a network, or files within a system can all serve as the medium.

What exactly do you mean by event-driven programming?

Event-driven programming is a method of initiating numerous functions that strongly rely on events. An event can range from anything like a mouse click to a keystroke. A callback function already registered with the element is executed when an event occurs. This method is mainly based on the publish-subscribe pattern. Node.js is faster than other technologies due to event-driven programming.

How does the event loop work in Node.js?

In Node.js, an event loop handles all asynchronous callbacks in an application. It is a significant component of Node.js and the cause for nonblocking I/O in Node.js. Because Node.js is an event-driven language, you can easily connect a listener to an event, and when the event happens, the listener will execute the callback. When functions such as setTimeout, http.get, and fs.readFile is invoked, Node.js runs the event loop and then continues with the code without waiting for the output. When the operation is complete, Node.js receives the result and executes the callback function. It is why, in a loop, all callback functions are queued. They are carried out one by one after receiving the response.

Describe the REPL in the context of Node.js

REPL is an abbreviation for reading, Eval, Print, and Loop in Node.js. It symbolizes a computer environment, such as a window console or a Unix/Linux shell, in which any command can be input, and the system will respond with an output. By default, Node.js includes a REPL environment. REPL is capable of the following tasks:

Read: Reads user input, parses it into a JavaScript data structure, and stores it in memory.

Eval: Receives the data structure and evaluates it.

Print: This command prints the final output.

Loop: Recursively executes the specified command until CTRL+C is pushed twice.

What exactly are node.js streams?

Streams are EventEmitter entities that can work with streaming data in Node.js. They can be used to handle and manipulate huge files (videos, mp3, etc.) streamed over the network. They make use of buffers for temporary storage.

The stream is divided into the following categories:

Writable: data-writing streams (for example, fs.createWriteStream()).

Readable: data streams that can be read (for example, fs.createReadStream()).

Duplex streams can be read and written in both directions (for example, net.Socket).

Duplex streams can change or transform data as written and read (for example, Zlib.createDeflate()).

What exactly are node.js buffers?

In general, a buffer is a temporary memory mainly utilized by streams to store data until it is used. Pads, which are presented with more use cases than JavaScript's Unit8Array, primarily represent a fixed-length series of bytes. It also supports legacy encodings such as ASCII, utf-8, etc. Outside of the v8, it is a fixed (non-resizable) allocated RAM.

What is middleware?

Middleware is the software that sits between your request and the business logic. It is mainly used to record logs and enable rate limiting, routing, authentication, and anything else that is not part of business logic. Third-party middleware, such as body-parser, is available, and you can develop your middleware for a specific use case.

What is Reactor Pattern in Node.js?

The reactor pattern is yet another pattern for nonblocking I/O operations. However, this is commonly utilized in any event-driven design.

There are two parts to this: 1. Handler 2. Reactor

Reactor: Its job is to route the I/O event to the proper handlers.

Handler: Its responsibility is to work on such events.


Node.JS is undoubtedly a handy web development tool available today. It is built on JavaScript and allows you to adapt to most web development settings.

If you want to recruit a Node.JS developer, you should know what questions to ask. You must know what to expect from the candidate if you review the questions and answers offered in this guide. For more information visit the website Relinns.

 We wish you success in interviewing and scaling your business! Best wishes!


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