Top Node.js Interview Questions and Answers (2024)

Node.js is an open-source server-side JavaScript runtime environment. Node.js is cross-platform, which means it can work on any platform, such as Windows, Linux, MacOS, etc.

Node is extremely popular as it is used to develop web applications, APIs and backend services, real-time chats, e-commerce, IoT, Single-Page Applications, streaming applications, real-time collaboration tools, DevOps tools, etc.

Node.js is a highly sought-after skill, and the following Node.js interview questions and answers can help you prepare for your technical interview.

1. What are the advantages of using Node.js?

Node.js has a lot of advantages that make it a popular choice among developers. 

1. Node.js is relatively easy to learn if you understand JavaScript well.
2. High performance due to it being event-driven and having a single-threaded design
3. Since Node.js uses microservices architecture, it is easier to scale
4. It provides cross-platform support
5. It has a rich ecosystem, and using NPM, you can integrate third-party packages into applications, speeding up web application development.
6. Node.js has a huge community support.
7. Node.js is cost-effective because it enables using JavaScript on both the client and server sides, significantly reducing the time and resources required for development

2. Explain the working of Node.js

Node.js accepts requests from clients in a single thread to the server. These requests are then stored in an Event Queue on the server and passed to the Event loop sequentially on a first-come-first-serve basis. The event loop then handles the asynchronous (non-blocking) operations directly, while asynchronous (blocking) operations are offloaded to the worker pool (libuv’s thread pool). 

3. What is NPM?

NPM stands for Node Package Manager and is the World’s largest software library. NPM allows JavaScript developers to share packages quickly and easily. It consists of two main parts - A CLI (Command Line Interface) for publishing and downloading tools and an online repository that hosts JavaScript packages.\

4. Can you use Node.js for front-end development?

Node.js is primarily intended for use on the server side. However, it can also be used in the front end for tasks like bundling, transpiring, and running build scripts.

5. Why is Node single-threaded? How does Node handle concurrency, even though it is single-threaded?

Being single-threaded allows Node.js to simplify the development model and leverage the performance advantages of asynchronous programming.

Despite being single-threaded, Node.js handles concurrency because of its asynchronous nature and the ability to perform multiple I/O operations simultaneously.  

6. What are spawn() and fork() methods?

The spawn() and fork() methods are provided by the child_process module to create child processes in Node.js. However, there are differences between these two methods. Spawn () creates a new process with a specified command, while fork() creates a new Node.js process that runs a module. 

7. What is callback hell, and how can you avoid it?

Callback hell, or the ‘Pyramid of Doom’ in Node.js, is caused by the nesting of callbacks, making the code difficult to read and maintain.

This can be avoided by:

• Writing comments
• Using named functions
• Modularizing code
• Splitting functions into smaller ones
• Using promises in Node.js
• Using Async/Await

8. Explain streams in Node.js and the different types.

Stream is an abstract interface in Node.js that handles continuous data flows or streaming data.

There are 4 different types of streams:

1. Readable - they are streams from which data can be read
2. Writable - they are streams to which data can be written
3. Duplex - these are readable and writable streams
4. Transform - these duplex streams that can modify data

For your next Node.js job interview preparations, familiarize yourself with as many questions as possible. A thorough understanding of the basics and a strong grasp of advanced topics will give you the confidence to ace any Node.js interview.