NodeJS interview questions
- What is Node.js and how does it work?
- What is the difference between synchronous and asynchronous code in Node.js?
Synchronous code is executed sequentially, one line of code at a time, blocking the event loop until each operation is complete. Asynchronous code, on the other hand, allows the event loop to continue running while waiting for I/O operations to complete. This makes Node.js highly scalable and efficient.
- What are the advantages of using Node.js?
Some of the advantages of using Node.js include:
- Faster development due to its lightweight and efficient nature
- Ability to handle a large number of concurrent requests
- Support for real-time applications with its event-driven architecture
- Large and active community of developers
- What is npm and what is it used for?
npm is the Node Package Manager, a command-line tool used for installing, managing, and sharing Node.js packages. It is used to install packages and dependencies required for building Node.js applications, as well as to publish and share packages with other developers.
- What is callback hell in Node.js?
Callback hell is a term used to describe the problem of having too many nested callbacks in Node.js code, making it difficult to read and maintain. This problem arises due to Node.js’ asynchronous nature, which requires the use of callbacks to handle I/O operations. To avoid callback hell, developers can use promises or async/await functions.
- What is the purpose of the EventEmitter class in Node.js?
The EventEmitter class in Node.js is used for handling and emitting events. It allows developers to create custom events and attach listeners to them, which are triggered when the event is emitted. This is particularly useful for building real-time applications, where events can be used to signal changes or updates to connected clients.
- How does Node.js handle asynchronous I/O operations?
Node.js uses an event-driven, non-blocking I/O model to handle asynchronous I/O operations. When an I/O operation is initiated, Node.js does not block the thread, but instead registers a callback function to be called when the operation is complete. This allows Node.js to handle a large number of concurrent I/O operations without blocking the event loop.
- What is the purpose of the “exports” object in Node.js?
The “exports” object in Node.js is used to expose functions, objects, or variables from a module to other parts of the application. When a module is loaded using the “require” function, the “exports” object is returned, allowing other modules to access its contents.
- How do you handle errors in Node.js?
In Node.js, errors are typically handled using the try-catch block or by passing an error object as the first parameter to a callback function. Developers can also use the “process.on(‘uncaughtException’)” method to handle uncaught exceptions that occur during the execution of the application.
- What is middleware in Node.js?
Middleware in Node.js is a function that sits between the request and response objects in an HTTP request/response cycle. It can be used to modify the request or response, handle errors, or perform other tasks. Middleware is typically used in web applications to implement authentication, logging, and other common tasks.
How this helps you in your next interview 🙂