Node.js Interview Questions Every Beginner Should Know

Node.js Interview Questions Every Beginner Should Know

Node.js fundamentals come up in every backend interview. Here are the questions beginners must know.

What is Node.js and how does it work?

Node.js is a JavaScript runtime built on V8 that runs JS on the server. It uses libuv for async I/O and an event loop to process callbacks non-blockingly on a single thread.

What is the event loop?

The event loop is a single-threaded loop that processes callbacks from completed async operations. It is what makes Node.js non-blocking and efficient for concurrent I/O.

What is the difference between async and sync code in Node.js?

Sync code blocks the main thread until it completes. Async code returns immediately and runs a callback when done, letting the event loop process other work. Always prefer async for I/O.

What are module.exports and require?

They are Node.js's CommonJS module system. module.exports exports values from a file, and require imports them. This is how Node.js code is split into modules.

What is middleware in Express?

Middleware is a function that runs between the request and the response. It can modify the request, end the response, or call the next middleware. Auth and logging are common middleware.

What is the difference between process and global?

global is the global object in Node.js (like window in the browser). process is a global object that provides information about the running Node.js process, like environment variables and exit events.

The Takeaway

Know these beginner Node.js questions cold: what Node.js is, the event loop, async vs sync, module.exports and require, middleware, and process vs global. These fundamentals come up in every backend interview.