Node.js

Question 1

What is a CLI?

Answer 1

Command line interface
Text based way to talk to a program

Question 2

What is a GUI?

Answer 2

Graphical user interface
Aimed at consumers of technology (end users)

Question 3

Man (manual/directions and helpful tools)

Answer 3

Man man

Question 4

Cat (concatenate files and prints content into terminal)

Answer 4

Cat filename.txt (prints the content of the file)
Cat filename.txt secondfilename.txt anotherfile.txt > new-file-with-all-three-content.txt (makes a new file with the content from the 3 files)

Question 5

ls (lists all the contents of working directory)

Answer 5

ls (this lists the contents in the directory, but doesn’t show hidden ones that start with ‘.’)
ls -a (this lists (-a) all files, even the hidden ones)
ls -F (this lists whether the files are directories vs files by showing / after the directory name)
ls fileDirectoryName/ (this lists the files in this directory)
ls fileDirectoryName/fileName.txt

Question 6

pwd (print working directory, prints the current working directory aka where are you right now)

Answer 6

pwd (this prints current working directory)
pwd > i-was-here.txt (this writes current working directory into a new file)

Question 7

echo (repeats the text line back into the terminal, console.log for the terminal)

Answer 7

echo ‘Hello, World!’ (prints Hello, World! into terminal)
echo ‘Hello, World!’ > hello.txt (assigns the string into a new file)

Question 8

touch (revise timestamp and create file if it doesn’t exist)

Answer 8

touch new-file-name.txt (makes new file)
touch workingDirectory/new-file-name.txt (creates new file in the directory)
touch parent/child/grandchild/.gitkeep (creates a new file in the grandchild directory)

Question 9

mkdir (makes new directory)

Answer 9

mkdir parent (created a new directory named parent)
mkdir -p parent/child/grandchild (the -p option creates nested parent/child/grandchild directories)

Question 10

mv (move or rename file)

Answer 10

mv old-directory-name new-directory-name (changes the old directory name to the new directory name)

Question 11

rm (remove file or directory **permanent and no warning)

Answer 11

rm file-name.txt (the file is deleted/removed)
rm -r directory-name/ (the -r command removes the directory and all of its contents)

Question 12

cp (copy a file)

Answer 12

cp file-name.txt copy-of-file-name.txt (this copies the file and makes a new file with same content)

Question 13

What are the three virtues of a great programmer?

Answer 13

1. Laziness: The quality that makes you go to great effort to reduce overall energy expenditure. It makes you write labor-saving programs that other people will find useful and document what you wrote so you don’t have to answer so many questions about it.
2. Impatience: The anger you feel when the computer is being lazy. This makes you write programs that don’t just react to your needs, but actually anticipate them. Or at least pretend to.
3. Hubris: The quality that makes you write (and maintain) programs that other people won’t want to say bad things about.

Question 14

What is Node.js?

Answer 14

Runs Javascript outside of a browser
Mainly used for file system access and network access (and gives up DOM access from JavaScript)
Event driven, like CSS

Question 15

What can Node.js be used for?

Answer 15

Backends for web apps (http servers), command lines programs

Question 16

What is a REPL?

Answer 16

Read eval print loop
Reads and evaluates the javascript code and then returns the result and then loops meaning it is ready to read code again
I.e. chrome dev tools console

Question 17

When was Node.js created?

Answer 17

Nov 2009

Question 18

What back end languages have you heard of?

Answer 18

Scripting languages (aka interpreted)
JavaScript, php, ruby, python, lua
JIT (just-in-time-compiled)
JavaScript
Compiled, memory-managed (with a garbage collector)
C# (clr family languages)
C#, F#, visual basic
Java, (jvm/java-virtual-machine family languages)
Kotlin, clojure, groovy,
Compiled, low-level (with no garbage collector)
C, C++, D, zig, rust
Database
Sql

Question 19

What is the process object in a Node.js program?

Answer 19

The process object is an instance (global object, kind of like the window object for browser/front-end) of the running program

Question 20

How do you access the process object in a Node.js program?

Answer 20

You can console log the process object into your javascript file and then run the file in the node program via command
JS file contains console.log(process);
Type in command terminal –> node jsFileName.js

Question 21

What is the data type of process.argv in Node.js?

Answer 21

Array of strings
Contains the command line arguments passed when the Node.js process was launched
First element is full path to process.execPath
Second element is the path to the JavaScript file being executed
Remaining elements are additional command line arguments

Question 22

What is a JavaScript module?

Answer 22

JavaScript module is the file.js
Each file is a small part of the larger picture of the code
Module is the container that contains everything necessary to execute one aspect of the desired functionality

Question 23

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

Answer 23

Export
How this module can provide values and functionality to other modules
Require
How this module can pull values and functionality from other modules
Module
Data model for the whole module
__filename
Full path to this file name of where it is
__dirname
Full path to the directory name of where it is

Question 24

Give two examples of truly global variables in a Node.js program.

Answer 24

Process, global, console

Question 25

What is the purpose of module.exports in a Node.js module?

Answer 25

It stores the function as a value of a named key of the exports key of the module object, so it can be used in another module
module.exports[keyName] = functionName;

Module.exports = {
Add: add,
addSassy: addSassy
}

**This would be to add multiple properties with different function values into the exports property, which can only be stored 1x per module

Question 26

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

Answer 26

Assign the object stored from the other module into a variable via require
Const add = require(‘./add’);

Question 27

What is the JavaScript Event Loop?

Answer 27

When a code that is not happening immediately runs(like setTimeout or getting ajax request), it gets popped off the call stack and pushed onto the webapis stack, where it is processed. When this is done processing and has an output, it gets pushed onto the task queue. The JavaScript Event Loop sees the items in the task queue and will push the first item onto the call stack ONCE the call stack is EMPTIED.

Question 28

What is the difference between “blocking” and “non-blocking” with respect to how code is executed?

Answer 28

Blocking codes are code on the call stack which has to be run one at a time and if it’s take a long time, it is “blocking” the other code in the call stack from running
Non-blocking codes are not on the call stack and processed elsewhere and thus do not block the other codes in the call stack from running

Question 29

What is a directory?

Answer 29

Directory is the parent container for files which have content

Question 30

What is a relative file path?

Answer 30

Relative file path is a url/ that shows the location of the file in comparison to the current file and can only be accessed within the file/program

Question 31

What is an absolute file path?

Answer 31

Absolute file path is a url that contains the location of the file starting from the root. It can be used to access the file from the url alone

Question 32

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

Answer 32

The File system aka fs module
Const fs = require(‘fs’);

Question 33

What is a client?

Answer 33

Some hardware or software that’s requesting information from server

Question 34

What is a server?

Answer 34

Some hardware or software that’s providing information from server that was requested
Host = hardware, the actual physical box
Server = computer program (software programs)

Question 35

Which HTTP method does a browser issue to a web server when you visit a URL?

Answer 35

‘GET’ request method

Question 36

What is on the first line of an HTTP request message?

Answer 36

HTTP Method
Like get, put, post
Request target
Url (with query strings)
resource/thing you can get
Http version (message format)
Defaults to 1.1

Question 37

What is on the first line of an HTTP response message?

Answer 37

Protocol (version)
Usually http/1.1
Status code
I.e. 404 which means not found, doesn’t exist
Status text
I.e. actual text description saying ‘not found’
Looks like http/1.1 404 not found

Question 38

What are HTTP headers?

Answer 38

Meta data about the message exchange between the server and client witten under the first line of the HTTP request or HTTP response message
Additional information that basically describes the original format of the message data and any encoding applied
Like meta information in the head element in html
**we care about Content-Type in the http header of the response message, which will tell us the type of message we received (i.e. application/json; charset=utf-8

Question 39

Is a body required for a valid HTTP message?

Answer 39

No
If the response is too long, you should redirect the content into a separate file to not only reduce API usage, but also easier to access the data in a file
I.e. http –body GET https://example.com > index.html

Question 40

What is NPM?

Answer 40

World’s largest software registry named Node Package Manager
A way to reuse code shared by other developers and to
share your code with other developers and helps
manage the different versions of code
All packages are defined in files called package.json
The website itself
https://docs.npmjs.com/
The registry - big database of packages that are being shared
The Command Line Interface (CLI) / Npm client
When a developer chooses to publish their code, they
can by publish the code up to the registry via the npm
client which is installed on the computer to, which then
other developers can install the package from the
registry via the npm client to reuse that code

Question 41

What is a package?

Answer 41

A directory with one or more files in it that has a package.json with metadata about the package
Doesn’t mean it has to be published to the registry
Helps reuse the package in your code so you don’t have to create one every time
The package/module is the code that is created by someone and then accessed via NPM with the current version(if applicable)

Question 42

How can you create a package.json with npm?

Answer 42

Type in the following command:
npm init –yes (or -y)
It could make it without the –yes and type in every initial properties/values

Question 43

What is a dependency and how do you add one to a package?

Answer 43

It’s a 3rd party package that is depended on, which is a folder containing a program described by package.json file
Package references used by your library without which it cannot work and must be installed along with your library installation automatically
You can add package by using the install command
npm install (package name)

Question 44

What happens when you add a dependency to a package with npm?

Answer 44

‘Dependencies’ gets added as a property with an object as a value, which contains jquery(or whatever you installed as a dependent) as a property with the current version number as its value.
Creates a node_modules directory and installs the package and their code into the directory
node_module
jquery
.package-lock.json

Question 45

How do you add express to your package dependencies?

Answer 45

Create a package.json with npm init –yes command
Install with npm install express command

Question 46

What Express application method starts the server and binds it to a network PORT?

Answer 46

Listen method
app.listen([port[,host[,backlog]]][,callback])

Question 47

How do you mount a middleware with an Express application?

Answer 47

app.use() or app.get, put or post methods with the first parameter a string of where you want to mount
The first parameter of the path is optional
**Like addEventListener request, when the server receives this request, what do you want to do

Question 48

Which objects does an Express application pass to your middleware to manage the request/response lifecycle of the server?

Answer 48

Request object
HTTP Request message (data model)
Response object
HTTP response message (control)
Methods, not properties

Question 49

What is the appropriate Content-Type header for HTTP messages that contain JSON in their bodies?

Answer 49

Content-Type: application/json
**This is written in the header meta data
This is what we’re hoping in receiving, a content type of JSON, but the person who made the code could NOT actually send you JSON if that’s how they structured their code

Question 50

What is the significance of an HTTP request’s method?

Answer 50

Semantics only, and expresses the intent of the code block
Reads the request name and finds the same request method that matches and executes the code block (?)
Allows the server what we want to do in response to the request

Question 51

What does the express.json() middleware do and when would you need it?

Answer 51

What does the express.json() middleware do and when would you need it?