7 Node JS Interview Questions to Ask Before You Hire Node JS Developer

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By: Sagar Sharma

7 Node JS Interview Questions to Ask Before You Hire Node JS Developer

If you’re planning to hire Node JS developer for your next project, then you must also be interested in preparing a bunch of technical questions to test the skills and qualifications of candidates.

It’s what you’re here for, right?

You want to find the right Node JS interview questions to ask so that you can determine whether a candidate is qualified for the job or not.

Well, guess what? – You’ve come to the right place.

We’re a multiple Award-Winning Agile Software Development company having over a decade of experience in Node JS development and world-famous brands like Samsung, Cisco, etc. as our clients.

Now, the above paragraph might seem like a bit of showoff but rest assured that the only reason to mention our accolades here is to point out the fact that we know Node JS inside out. And in this blog, we’ll share the most important Node JS interview questions to ask before you hire Node JS developer.

7 Node JS Interview Questions to Ask When Hiring Node JS Developers

The best remote Node JS developers are those who not only have sufficient knowledge about the technology but are also creative when it comes to solving real-life problems.

That being said, here are the most important Node JS interview questions you should be asking when interviewing candidates.

1 – What is Node JS and Where It can be used?

Node JS is basically a JavaScript runtime environment that allows developers to write server-side scripts. It is built on top of Google Chrome’s V8 Engine and uses event-driven, non-blocking I/O model.

Developers and companies use Node JS to develop different kinds of applications and services such as REST APIs, web applications, real-time chat applications, and much more.

If you’re interested to get a better understanding of where exactly Node JS can be used, we’ve written a separate blog on Node JS Use Cases. Be sure to check that out.

And as long as we’re talking about getting a better understanding, we’ve also written a comprehensive article on What is Node JS. Feel free to check that out as well if you’d like to get a deeper understanding of Node JS.

2 – What is the difference between Asynchronous and Non-blocking?

Asynchronous in Node JS basically allows developers to make asynchronous HTTP requests, meaning there will be no need to wait for a server to respond. The application can continue working on other blocks and respond when the server response is received.

Non-blocking, on the other hand, is are functions that are often used with I/O operations. These functions basically respond immediately with whatever data available to keep on executing the incoming requests. And if any response couldn’t be retrieved, then the code will instantly return with an error.

3 – What is a Callback function in Node.js?

Node JS is an asynchronous JavaScript framework. Hence, it does not wait around for a file I/O to finish. – It uses Callbacks.

Callbacks are basically functions that are called at the completion of assigned tasks, which prevents blocking and allows the execution of other code parallelly.

In simple terms, Callbacks provide developers with an interface to say “once you’re done with this, do this thing next”. This, as a result, allows a Node JS application to handle numerous I/O operations running at the same time.

4 – What is package.json? What is it used for?

The Package.JSON is basically a file in Node JS stored at the heart of your application. It’s a manifest file that stores the metadata of your Node JS app where the properties of a package are defined.

Here’s an example:

package json

5 – What do you understand by callback hell?

Callback hell is often referred to as a pyramid of doom. It’s basically a pattern caused due to intensively nested callbacks in a Node JS application that are unwieldy and unreadable.

Simply put, a Node JS application that contains an overload of nested callback functions, which ultimately makes the code hard to read, understand, and debug. This generally happens by developers not implementing the asynchronous logic properly.

6 – What are Promises?

Promises basically give an alternate way to write asynchronous code and they can help you better handle the asynchronous functions in a Node JS application.

Although promises were first introduced in the 80s, but they became popular after the evolution of JavaScript. And today, they’re commonly found in most modern programming languages.

In simple terms, Promises can be used to either return the result or error. And similar to the old-fashioned If-else function, developers are required to use <.then()> function to implement Promises in a Node JS application.

7 – What is the Control Flow function? Explain how “Control Flow” controls functional calls

When you want to write asynchronous code in Node JS, you’ll often require to use lots of callback functions. Now, if you’re developing a complex application, there are chances that will reach the limit of writing nested callbacks, which is 63.

When that happens, you’re highly likely to experience callback hell. And the best way to avoid that from happening is to use the control flow function.

The Control Flow function helps to structure all asynchronous code so that your application doesn’t end up experiencing callback hell.

The Control Flow function will help you:

  • Collect data
  • Control the execution order
  • Integration limit
  • And call the next step in the program

As a result, this will help you to have better control over the code in your Node JS application.


With this, we have finally arrived at the end of important Node JS interview questions to ask before you hire Node JS developer.

The above-mentioned questions, and their answers specifically, will help you determine whether a candidate is worth hiring or not.


Q:1 – What is Node JS?

Ans: Node JS is a cross-platform, open-source, JavaScript runtime engine that executes the JavaScript code outside of browsers.

Q:2 – What are the benefits of Node JS?

Ans: There are many benefits of Node JS such as:

  • Easy to learn
  • High performance
  • Easy scalability
  • Benefit of Full-Stack development
  • Large & active community

Q:3 – Is Node JS good for microservices?

Ans: Yes! Since Node JS is lightweight, using Node JS for creating microservices architecture is a great choice.

Q:4 – Is Node JS better than Python for building Real-Time Applications?

Ans: Yes, Node JS is better for building real-time applications mainly because it supports callbacks and is built upon Chrome’s JavaScript V8 engine, which is a reasonably powerful and fast engine.


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