Top Node.js Interview Questions on GitHub: Ace Your Next Interview

Introduction

Node.js is a popular open-source, cross-platform runtime environment that allows developers to build server-side and networking applications using JavaScript. As a result, Node.js has become an essential skill for web developers, and many companies are looking for developers with expertise in this technology. In this article, we will explore some of the most common Node.js interview questions found on GitHub, along with code examples to help you prepare for your next interview.

1. What is Node.js and why is it popular?

Node.js is a runtime environment built on Chrome’s V8 JavaScript engine that allows developers to create server-side applications using JavaScript. It is popular because it enables developers to use a single programming language for both client-side and server-side development, resulting in increased productivity and easier maintenance. Additionally, Node.js is known for its excellent performance, scalability, and large ecosystem of libraries and frameworks.

2. What is the difference between synchronous and asynchronous programming in Node.js?

Synchronous programming means that the code is executed sequentially, with each operation waiting for the previous one to complete before moving on to the next. In contrast, asynchronous programming allows multiple operations to be executed concurrently without waiting for each other to finish. Node.js is designed to support asynchronous programming, which is essential for building high-performance and scalable applications.

3. How does the event loop work in Node.js?

The event loop is a core concept in Node.js that enables asynchronous processing. It continually checks for new events (such as incoming requests or I/O operations) and processes them in a non-blocking manner. This allows Node.js to handle a large number of concurrent connections efficiently.

const fs = require('fs');

fs.readFile('file.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);});

console.log('Reading file...');

4. What are callbacks, and how are they used in Node.js?

Callbacks are functions that are passed as arguments to other functions and are executed at a later time. They are commonly used in Node.js to handle asynchronous operations, such as reading from a file or making an HTTP request. The callback function is called when the asynchronous operation is completed, allowing the program to continue processing other tasks in the meantime.

5. What are Promises and how do they differ from callbacks?

Promises are a more modern approach to handling asynchronous operations in JavaScript, providing an alternative to callbacks. A Promise represents the eventual result of an asynchronous operation and can be in one of three states: pending, fulfilled, or rejected. Promises allow for more readable and maintainable code by chaining multiple asynchronous operations and handling errors more gracefully.

const fs = require('fs').promises;

async function readFile() {
  try {
    const data = await fs.readFile('file.txt', 'utf8');
    console.log(data);
  } catch (err) {
    console.error(err);
  }}

readFile();
console.log('Reading file...');