Node JS Design Patterns

Question 1

What is the core principle of the Node.js core?

Answer 1

Having the smallest possible set of functionalities, leaving the rest to userland modules

This principle allows the community to experiment and iterate quickly on solutions.

Question 2

What is the main building block for creating applications in Node.js?

Answer 2

Modules

Modules structure the code of a program and facilitate reusable libraries.

Question 3

Name two precepts from the Unix philosophy that Node.js embodies.

Answer 3

• Small is beautiful
• Make each program do one thing well

Question 4

What problem does Node.js’s module manager solve?

Answer 4

Dependency hell

It allows multiple packages to depend on different versions of the same package without conflicts.

Question 5

List three advantages of small modules in Node.js.

Answer 5

• Easier to understand and use
• Simpler to test and maintain
• Small in size and perfect for use in the browser

Question 6

What does the Don’t Repeat Yourself (DRY) principle advocate?

Answer 6

Sharing or reusing even the smallest piece of code

Question 7

What is the desired characteristic of Node.js modules in terms of API exposure?

Answer 7

Exposing a minimal set of functionalities

Question 8

True or False: Node.js modules are often designed to be extended.

Answer 8

False

They are created to be used rather than extended.

Question 9

What does the KISS principle stand for?

Answer 9

Keep It Simple, Stupid

Question 10

Who coined the term ‘worse is better’?

Answer 10

Richard P. Gabriel

Question 11

What is the main disadvantage of traditional blocking I/O?

Answer 11

It blocks the execution of the thread until the operation completes.

Question 12

What is the typical solution for handling multiple connections in traditional blocking I/O?

Answer 12

Using a separate thread (or process) for each concurrent connection

Question 13

What does non-blocking I/O allow?

Answer 13

The system call returns immediately without waiting for the data

Question 14

Fill in the blank: In non-blocking I/O, if no data is available, the function returns _______.

Answer 14

a predefined constant indicating no data

Question 15

What is busy-waiting in the context of non-blocking I/O?

Answer 15

Actively polling the resource within a loop until data is available

Question 16

What is event demultiplexing?

Answer 16

A mechanism to handle concurrent non-blocking resources efficiently

Question 17

How does the synchronous event demultiplexer work?

Answer 17

Watches multiple resources and returns events when operations complete

Question 18

What is the event loop in Node.js?

Answer 18

The process that blocks until new events are available to process

Question 19

What does the reactor pattern in Node.js associate with each I/O operation?

Answer 19

A handler, represented by a callback function

Question 20

What is one of the benefits of using a single-threaded model in Node.js?

Answer 20

Minimizing total idle time of the thread

Question 21

True or False: The absence of in-process race conditions allows for simpler concurrency strategies in Node.js.

Answer 21

True

Question 22

What is the reactor pattern?

Answer 22

A specialization of algorithms that associates a handler with each I/O operation.

Question 23

In Node.js, what is a handler represented by?

Answer 23

A callback (or cb for short) function.

Question 24

What does the Event Demultiplexer do in the reactor pattern?

Answer 24

It receives new I/O operation requests and returns control immediately.

Question 25

What happens when a set of I/O operations completes?

Answer 25

The Event Demultiplexer pushes corresponding events into the Event Queue.

Question 26

What does the Event Loop do in the reactor pattern?

Answer 26

It iterates over the Event Queue and invokes the associated handlers.

Question 27

How does a Node.js application exit?

Answer 27

When there are no more pending operations in the event demultiplexer and no more events in the event queue.

Question 28

What is libuv?

Answer 28

The low-level I/O engine of Node.js that abstracts system calls and implements the reactor pattern.

Question 29

Which operating systems use different interfaces for the event demultiplexer?

Answer 29

Linux (epoll), macOS (kqueue), Windows (I/O completion port API).

Question 30

What three components are needed to build the full Node.js platform?

Answer 30

* Bindings for libuv and low-level functionalities * V8 JavaScript engine * Core JavaScript library implementing Node.js API.

Question 31

What is a significant difference between JavaScript in Node.js and in browsers?

Answer 31

Node.js does not have a DOM or window/document objects but has access to OS services.

Question 32

What allows Node.js applications to run the latest JavaScript features?

Answer 32

The use of recent V8 versions and the ability to target specific Node.js versions.

Question 33

What is CommonJS?

Answer 33

The original Node.js module system using the require keyword to import modules.

Question 34

What is the ES modules syntax in Node.js?

Answer 34

The modern module syntax that uses the import keyword, but with different implementation details.

Question 35

What can you access with the fs module in Node.js?

Answer 35

Any file on the filesystem, subject to OS-level permissions.

Question 36

What powerful capability does Node.js offer regarding native code?

Answer 36

The ability to create userland modules that bind to native code.

Question 37

What is the advantage of using the N-API interface in Node.js?

Answer 37

It allows for reusing existing or new components written in C/C++.

Question 38

What is WebAssembly (Wasm)?

Answer 38

A low-level instruction format that allows compiling languages like C++ or Rust into a format understandable by JavaScript VMs.

Question 39

What is the essence of 'Node way' in programming?

Answer 39

Writing smaller, simpler modules that expose only the necessary functionality.

Question 40

What are the three pillars of Node.js architecture?

Answer 40

* V8 * libuv * Core JavaScript library.

Question 41

True or False: Node.js applications are limited to browser features.

Answer 41

False.

Question 42

Fill in the blank: The reactor pattern handles I/O by blocking until new events are available from a set of observed _______.

Answer 42

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