Top 10 Node.js Interview Questions for Freshers in 2023

Node.js is a popular JavaScript runtime that enables the creation of server-side applications with JavaScript. If you are a fresher looking for a job as a Node.js developer, it's important to be prepared for the common questions you may be asked during a job interview. In this article, we will cover the top 10 Node.js interview questions for freshers, along with detailed answers to help you understand the concepts and prepare for your interview.

Before diving into the specific questions, it's a good idea to brush up on your general knowledge of JavaScript and web development concepts. Familiarizing yourself with the Node.js documentation and learning about its core features, such as the event loop and the file system module, will also be helpful. Additionally, consider practising your coding skills by working on some Node.js projects or exercises. This will not only help you build your portfolio, but it will also give you the chance to apply the concepts you have learned and get a better feel for what it's like to work with Node.js in a real-world setting.

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows developers to run JavaScript on the server side, enabling the creation of server-side applications with JavaScript. Node.js is often used for building real-time web applications, such as chat apps and multiplayer games, as well as for creating APIs (Application Programming Interfaces) and backend services.

The event loop is a key concept in Node.js that allows it to perform non-blocking, asynchronous I/O operations. When a Node.js application starts, it initializes the event loop, which listens for events and executes the appropriate callback functions. The event loop runs in a single thread, but it can delegate blocking tasks to worker threads, allowing the event loop to remain responsive to incoming events.

The JavaScript runtime in a web browser is designed to execute client-side code, such as handling user events, updating the DOM (Document Object Model), and making HTTP requests. In contrast, the Node.js runtime is designed to execute server-side code, such as handling HTTP requests, connecting to a database, and executing backend logic.

Some common use cases for Node.js include building real-time web applications, such as chat apps and multiplayer games, creating APIs and backend services, building command-line tools, and creating server-side scripts for automation tasks.

Node.js uses a single-threaded, event-driven model to handle concurrency. When a request comes in, it is added to an event queue, and a callback function is registered to handle the request. The event loop then processes the request by executing the callback function, allowing the Node.js application to handle multiple requests concurrently without creating additional threads.

The Node.js file system module (fs) is a built-in module that provides a set of functions for interacting with the file system in a Node.js application. It allows developers to read, write, and manipulate files, as well as perform other file system-related tasks. The JavaScript file system API, on the other hand, is a browser-based API that allows developers to create, read, and write files from within a web application.

The NPM registry (short for Node Package Manager) is a public repository of open-source Node.js packages. It is used to distribute and share code, as well as to manage dependencies in a Node.js application. Developers can use the NPM command-line tool to search for and install packages from the registry, as well as to publish their own packages.

A Node.js middleware function is a function that sits between the request and the response in a Node.js application. It is used to perform tasks such as parsing request data, authenticating requests, and modifying the response before it is sent back to the client. Middleware functions are typically organized into a stack, with each function in the stack being executed in turn for each incoming request.

Node.js has a built-in error-handling mechanism that allows developers to handle errors in a structured way. When an error occurs in a Node.js application, it is thrown as an instance of the Error class. Developers can use try-catch blocks to catch errors and handle them appropriately. Alternatively, developers can use the 'uncaughtException' event to register a handler for uncaught errors.

Some common debugging techniques for Node.js applications include using the debugger keyword in the code, using the Node.js debugger module, using the console.log() function to print debug messages, using a debugging tool such as the Node.js Inspector or Chrome DevTools, and using a logging library such as Winston or Bunyan.

I hope these Node.js interview questions and answers are helpful for freshers preparing for job interviews in 2023.

Good luck with your preparation.