Node.js Developer interview questions

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine that allows you to build scalable network applications. It is used for its non-blocking, event-driven architecture, which makes it efficient for handling multiple requests simultaneously.

Asynchronous operations in Node.js can be handled using callbacks, promises, and async/await. Promises and async/await are more modern and make the code cleaner and more readable compared to traditional callbacks.

The event loop in Node.js is a single-threaded loop responsible for handling asynchronous operations. It allows Node.js to perform non-blocking I/O operations by offloading operations to the system kernel whenever possible.

Node.js performs file I/O using asynchronous APIs, allowing the JavaScript to be non-blocking and proceed without waiting for the file operation to complete. This is achieved using callbacks, promises, or the async/await pattern.

Node.js provides a variety of built-in modules such as http, fs (file system), path, url, and events. These modules provide various functionalities like creating servers, handling file operations, working with file and directory paths, and managing events.

npm, or Node Package Manager, is the default package manager for Node.js. It is used to install, update, and manage dependencies in Node.js projects. Developers also use npm to publish and distribute their own Node.js packages.

The package.json file in a Node.js project holds metadata about the application. It contains information such as the project's name, version, dependencies, scripts, and configuration for npm.

Environment variables are managed in Node.js using the process.env object. Alternatively, packages like dotenv can be used to load environment variables from a .env file into the process.env object.

Middleware in Express.js is a function that has access to the request and response objects in the application’s request-response cycle. Middleware functions can perform tasks like modifying request and response objects, ending the request-response cycle, and calling the next middleware function.

Errors in Node.js can be handled using try-catch blocks for synchronous operations and error-first callbacks or the catch method with promises for asynchronous operations. Express.js also provides middleware to handle errors globally.