Node.js

Question 1

What is Node.js?

Answer 1

Node.js is a program that allows JavaScript to be run outside of a web browser. Node.js is powered by V8; the same JavaScript engine in the Google Chrome browser.

Question 2

What can Node.js be used for?

Answer 2

It is commonly used to build back ends for Web applications, command-line programs, or any kind of automation that developers wish to perform.

Question 3

What is a REPL?

Answer 3

read-eval-print loop
Also termed an interactive top-level or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user; a program written in a REPL environment is executed piecewise

Question 4

When was Node.js created?

Answer 4

May 27, 2009

Question 5

What back end languages have you heard of?

Answer 5

Scripting Languages, these are interpreted on-the-fly
python, ruby (jit - just-in-time compilation), php, javascript (jit - 2008), perl, elixir, erlang

Memory Managed Languages - these languages are complied ahead of time, garbage collection
Java / Kotlin, Golang, C#, Haskell, Julia, F#, Fortran

Manual Memory Management - ahead of time compiled, low-level
C++, C, Swift, Rust, D, Zig

SQL - for databases

Question 6

What is theprocessobject in a Node.js program?

Answer 6

The process object is a global that provides information about, and control over, the current Node.js process.

Question 7

How do you access theprocessobject in a Node.js program?

Answer 7

As a global, it is always available to Node.js applications without using require(). It can also be explicitly accessed using require(): 
	const process = require(‘process’);

Question 8

What is the data type ofprocess.argvin Node.js?

Answer 8

The process.argv property returns an array (of strings) containing the command line arguments passed when the Node.js process was launched.

Question 9

What is a JavaScript module?

Answer 9

A single .js file. 
A module is just a bit of code encapsulated in a file, and exported to another file. Modules focus on a single part of functionality and remain loosely coupled with other filed in an application. This is because there are no global or shared variables between modules, as they only communicate via the module.exports object. Any code that you want to be accessible in another file can be a module.

Node.js programmers strive to separate their code into modules that each provide a small chunk of functionality. The program is a result of all these modules working together in concert.

Question 10

What values are passed into a Node.js module’s local scope?

Answer 10

exports, require, module, __filename, __dirname

Question 11

Give two examples oftrulyglobal variables in a Node.js program.

Answer 11

Console, process, global

Question 12

What is the purpose ofmodule.exportsin a Node.js module?

Answer 12

The main purpose of module.exports is to achieve modular programming. By module.exports, we can export functions, objects, and their references from one file and can use them in other files by importing them with the require() method. Exports is the object that is returned from the require() call.

Can achieve abstraction to separate business logic from other modules.
Easy to maintain and manage the code base in different modules.
Enforces separation of concerns.

Question 13

How do you import functionality into a Node.js module from another Node.js module?

Answer 13

require(“./filename’)
It is important to prefix the file name with ./ which tells Node.js that we are importing a local module. When require imports the module, it returns an object with the function as its method.

Question 14

What is a directory?

Answer 14

A directory is a file [system cataloging structure] which contains references to others files and directories.

Question 15

What is a relative file path?

Answer 15

Path to a file from the current directory

Question 16

What is an absolute file path?

Answer 16

Path to a file from the root of the file system, starts with a ‘/‘

Question 17

What module does Node.js include for manipulating the file system?

Answer 17

fs module (in-built File System module)

Question 18

What method is available in the Node.jsfsmodule for writing data to a file?

Answer 18

fs.writeFile

Question 19

Are file operations using thefsmodule synchronous or asynchronous?

Answer 19

There are both synchronous and asynchronous methods.

All asynchronous methods can perform synchronously by appending “Sync” to the function name. [e.g. fs.readFileSync() vs fs.readFile()]