- What is Node.js?
- What is the difference between `require()` and `import`?
- Explain the event loop in Node.js.
- What is the purpose of `package.json`?
- How does Node.js handle asynchronous operations?
- What is middleware in Express.js?
- What are streams in Node.js?
- Explain the concept of "callback hell" and how to avoid it.
- What is a promise and how does it work?
- What is the purpose of the `async` and `await` keywords?
- How do you handle errors in Node.js?
- What is Node Package Manager (NPM)?
- What are the different types of modules in Node.js?
- What is the role of the `eventEmitter` class in Node.js?
- Explain how you can set up a basic HTTP server in Node.js.
- What is the purpose of the `cluster` module in Node.js?
- How does Node.js achieve scalability?
- What is the `process` object in Node.js?
- What are `npm` scripts and how are they used?
- How can you optimize Node.js performance?
1. What is Node.js?
Node.js is an open-source JavaScript runtime environment that executes JavaScript code outside of a web browser. It’s built on the V8 engine and is designed to build scalable network applications with an event-driven, non-blocking I/O model.
2. What is the difference between `require()` and `import`?
`require()` is a function from CommonJS module system, which is used for synchronously including modules in Node.js. `import`, on the other hand, is part of the ES6 module syntax and supports asynchronous loading, offering a more modern approach to modular code.
3. Explain the event loop in Node.js.
The event loop is a fundamental mechanism in Node.js that manages asynchronous operations. It continuously checks the event queue for pending tasks and processes them, allowing Node.js to handle multiple operations without blocking the execution.
4. What is the purpose of `package.json`?
`package.json` is a configuration file that defines the project’s dependencies, scripts, metadata, and other settings. It’s crucial for managing project dependencies, configuring project scripts, and sharing project information with others.
5. How does Node.js handle asynchronous operations?
Node.js handles asynchronous operations through its non-blocking architecture, utilizing callbacks, promises, and async/await. This approach allows it to perform operations like file reading or network requests without halting the execution of other code.
6. What is middleware in Express.js?
Middleware in Express.js is a function that processes requests before they reach the route handler. It can modify the request object, terminate the request-response cycle, or handle errors, providing a way to customize the request processing flow.
7. What are streams in Node.js?
Streams are interfaces that allow reading or writing data in chunks, rather than in a single, complete operation. They enable efficient processing of large data sets by handling data piece-by-piece, reducing memory usage and improving performance.
8. Explain the concept of "callback hell" and how to avoid it.
Callback hell refers to deeply nested callback functions that can make code hard to read and maintain. To avoid it, developers can use Promises, async/await, or modularize code into smaller, manageable functions.
9. What is a promise and how does it work?
A promise is a placeholder for a value that is initially unknown but will be resolved in the future. It represents the result of an asynchronous operation, allowing you to handle success or failure using `.then()` and `.catch()` methods.
10. What is the purpose of the `async` and `await` keywords?
`async` and `await` simplify working with Promises by allowing you to write asynchronous code that looks synchronous. An `async` function returns a promise, and `await` pauses execution until the promise is settled, improving code readability.
11. How do you handle errors in Node.js?
Error handling in Node.js can be done using traditional try/catch blocks for synchronous code, or `.catch()` methods with Promises for asynchronous code. Additionally, error handling middleware can be used in Express.js to manage errors globally.
12. What is Node Package Manager (NPM)?
NPM is a package management tool for Node.js that facilitates the installation, updating, and management of libraries and dependencies. It’s the default package manager that comes with Node.js, enabling you to manage project packages easily.
13. What are the different types of modules in Node.js?
Node.js supports several module systems including CommonJS, which uses `require()` and `module.exports`, and ES6 modules, which use `import` and `export`. Each system has different characteristics and use cases in modular JavaScript development.
14. What is the role of the `eventEmitter` class in Node.js?
The `EventEmitter` class allows objects to emit events and handle them via listeners. It is crucial for implementing an event-driven architecture, enabling custom event handling and communication within Node.js applications.
15. Explain how you can set up a basic HTTP server in Node.js.
To create a basic HTTP server in Node.js, use the `http` module’s `createServer()` method to handle incoming requests and send responses. Here’s a simple example:
const http = require('http');
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World\n');
});
server.listen(3000, '127.0.0.1', () => {
console.log('Server is running at http://127.0.0.1:3000/');
});
16. What is the purpose of the `cluster` module in Node.js?
The `cluster` module is used to spawn multiple Node.js processes (workers) to distribute the load across multiple CPU cores. It enhances performance and reliability by allowing the application to handle more requests concurrently.
17. How does Node.js achieve scalability?
Node.js achieves scalability through its asynchronous, non-blocking architecture, which allows it to handle many connections simultaneously. By leveraging the event loop and asynchronous I/O operations, it scales efficiently for high-performance applications.
18. What is the `process` object in Node.js?
The `process` object provides information and control over the Node.js process. It includes properties and methods for accessing environment variables, handling signals, and interacting with the standard input/output streams.
19. What are `npm` scripts and how are they used?
`npm` scripts are custom commands defined in the `scripts` section of `package.json`. They can automate various tasks like building, testing, or running your application, and are executed using the `npm run
20. How can you optimize Node.js performance?
To optimize Node.js performance, consider techniques such as profiling and monitoring to identify bottlenecks, optimizing code for better memory management, using caching mechanisms, and implementing clustering to utilize multiple CPU cores effectively.
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