Single-threaded non-blocking I/O concept in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'single-threaded' mean in Node.js?

It means Node.js runs JavaScript code on one main thread, handling tasks one at a time in a sequence.

beginner

Explain 'non-blocking I/O' in simple terms.

Non-blocking I/O lets Node.js start a task like reading a file, then keep doing other work without waiting for the task to finish.

intermediate

How does Node.js handle multiple I/O operations with a single thread?

Node.js uses an event loop to watch for completed tasks and callbacks to handle results, so it can manage many I/O tasks without waiting.

beginner

Why is single-threaded non-blocking I/O good for web servers?

Because it can handle many users at once without waiting, making servers fast and efficient even with many requests.

intermediate

What happens if a task blocks the single thread in Node.js?

The whole program waits and becomes slow, because no other tasks can run until the blocking task finishes.

What does 'non-blocking' mean in Node.js I/O?

A Node.js waits for each task to finish before starting the next

B Node.js can start a task and do other work without waiting

C Node.js uses multiple threads for each task

D Node.js blocks the main thread during I/O

Non-blocking means Node.js starts a task and continues running other code without waiting for the task to finish.

How many main threads does Node.js use to run JavaScript code?

A One thread

B Two threads

C Multiple threads

D Depends on the CPU cores

Node.js runs JavaScript on a single main thread.

What mechanism does Node.js use to manage I/O tasks without blocking?

A Event loop

B Thread pool

C Synchronous calls

D Blocking queue

The event loop watches for completed tasks and triggers callbacks to handle them.

Why can blocking code slow down a Node.js application?

A Because it runs asynchronously

B Because it uses too many threads

C Because it stops the single thread from doing other work

D Because it uses too much memory

Blocking code stops the single thread, so no other code can run until it finishes.

Which of these is a benefit of Node.js single-threaded non-blocking I/O?

A Runs blocking code faster

B Uses multiple CPU cores automatically

C Requires less memory than other languages

D Handles many requests efficiently

Node.js can handle many requests at once without waiting, making it efficient.

Describe how Node.js uses single-threaded non-blocking I/O to handle multiple tasks.

Think about how Node.js can do many things without waiting for each to finish.

Explain why blocking code is a problem in Node.js and how non-blocking I/O solves it.

Consider what happens when the main thread is busy or free.