Node.js Core Modules & Event Loop 5

Question 1

What is the role of `libuv` in Node.js?

Accepted Answer

A multi-platform support library that provides the event loop and async I/O

Answer

libuv is the C library that provides Node.js with its cross-platform event loop, thread pool, and asynchronous I/O capabilities.

Question 2

How many threads does the default libuv thread pool use?

Accepted Answer

4

Answer

The default libuv thread pool size is 4, used for file system operations, DNS lookups, and other blocking tasks; it can be changed via `UV_THREADPOOL_SIZE`.

Question 3

What does the `stream.pipeline()` utility function do compared to manually piping streams?

Accepted Answer

It automatically handles cleanup and error propagation across all streams in the pipeline

Answer

`stream.pipeline()` properly handles errors and cleanup (destroy) for all streams in the chain, preventing the resource leaks that manual `.pipe()` can cause.

Question 4

Which core module would you use to parse and format URL strings in Node.js?

Accepted Answer

url

Answer

The `url` module provides the WHATWG `URL` class and legacy `url.parse()`/`url.format()` functions for working with URL strings.

Question 5

When a Promise resolves inside a `setTimeout` callback, in what order do its `.then()` callbacks execute relative to other `setTimeout` callbacks?

Accepted Answer

Before the next event loop phase begins, as microtasks

Answer

Resolved Promise `.then()` callbacks are microtasks and drain completely after each task (including setTimeout callbacks) before the event loop advances.

Node.js Practice Test

Node.js Practice Test

Node.js Core Modules & Event Loop 5