Frequently Asked
Questions

Node.js follows an event-driven, non-blocking I/O model. It uses an event loop to handle asynchronous operations. When an asynchronous task is completed, a callback function is executed. This allows Node.js to efficiently handle a large number of concurrent connections without blocking the execution of other tasks.

npm (Node Package Manager) is the default package manager for Node.js. It is used to install, manage, and share packages (libraries or modules) written in JavaScript. npm simplifies the process of adding external libraries to a Node.js project.

Modules in Node.js are encapsulated units of functionality that can be reused in different parts of a program. Each module has its own scope, and the module.exports object is used to expose functionality to other modules. Modules can be imported using the require keyword.

CommonJS is a module specification that Node.js follows for organizing code into reusable modules. It defines the require and module.exports mechanisms for importing and exporting functionality between modules, providing a way to structure and maintain code.

Express.js is a web application framework for Node.js. It simplifies the process of building web applications and APIs by providing a set of features and tools. Express.js is known for its minimalistic design, flexibility, and middleware architecture, making it a popular choice for web development in the Node.js ecosystem.

Middleware in Express.js are functions that have access to the request, response, and the next middleware function in the application's request-response cycle. They can perform tasks such as modifying the request or response objects, terminating the request-response cycle, or calling the next middleware in the stack.

A RESTful API (Representational State Transfer) is an architectural style for designing networked applications. In Node.js with Express, RESTful APIs can be implemented by defining routes and handlers for HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations on resources.

Routing in Express.js involves defining URL patterns and associating them with specific functions (handlers) that will be executed when a request matches a defined pattern. It helps in organizing and modularizing the application, making it easy to manage different routes and their associated functionality.

Callback hell, also known as the "Pyramid of Doom," occurs when multiple nested callbacks are used, leading to code that is difficult to read and maintain. It can be mitigated by using techniques such as modularization, named functions, and the use of control flow libraries or features like Promises and async/await.

The EventEmitter class is a core module in Node.js that provides an implementation of the observer pattern. It allows objects to subscribe to and listen for events, and emit events when certain actions occur. It is widely used for building custom event-driven architectures in Node.js applications.

CORS is a security feature implemented by web browsers to prevent unauthorized requests from different origins. In Node.js with Express, CORS can be handled by using the cors middleware or by manually setting the appropriate headers to allow or restrict cross-origin requests.

Security vulnerabilities reported by "npm audit" can be addressed by updating the affected packages to versions that have patched the vulnerabilities. The npm audit fix command can automatically install the updated packages. Additionally, developers should regularly review and update dependencies to address security issues proactively.