Node.js

Question 1

What is Node.js?

Answer 1

an open-source, asynchronous JavaScript runtime environment built on Chrome’s V8 JavaScript engine, which executes outside the browser

Question 2

What can Node.js be used for?

Answer 2

build scalable server side network applications

Question 3

What is a REPL?

Answer 3

a read-eval-print loop is a language shell

Question 4

When was Node.js created?

Answer 4

2009

Question 5

What back end languages have you heard of?

Answer 5

PHP, Python, Ruby, Java, C#

Question 6

What is a CLI?

Answer 6

command line interface, a text-based user interface

Question 7

What is a GUI?

Answer 7

graphical user interface

Question 8

Give at least one use case for each of the commands listed in this exercise.

Answer 8

man -read about a command in the manual
cat -combine text files, print out
ls -list contents of a directory
pwd -view current directory
echo -write a string to a text file, command line
touch -create a new text file, updated access stamp on files
mkdir -create a new directory
mv -move a file to another directory, rename files
rm -remove a file from the hard drive
cp -copy a file

Question 9

What are the three virtues of a great programmer?

Answer 9

laziness, impatience, hubris

Question 10

What is a computer process?

Answer 10

the instance of a computer program that is being executed by one or more threads

Question 11

Roughly how many computer processes are running on your host operating system (Task Manager or Activity Monitor)?

Answer 11

~200

Question 12

Why should a full stack Web developer know that computer processes exist?

Answer 12

a full stack web app is made form multiple processes together

Question 13

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

Answer 13

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

Question 14

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

Answer 14

access it directly with ‘process’ in Node.js, since it is a global object

Question 15

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

Answer 15

an array of strings

Question 16

What is a JavaScript module?

Answer 16

a single JavaScript file

Question 17

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

Answer 17

parameters: exports, require, module, __filename, __dirname

Question 18

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

Answer 18

clearImmediate(immediateObject)
console
process

Question 19

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

Answer 19

to export code to be used in another module

Question 20

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

Answer 20

by calling the require() function (with the argument being a string of the path to the JavaScript file) and assigning the return to a variable

Question 21

What is the JavaScript Event Loop?

Answer 21

a cycling process for how JavaScript executes code in a non-blocking manner, checks if there is something in the call stack again and again, and if not then checks the callback queue (which is made up of completed web APIs),
-if there is something in the queue, it gets moved to the call stack

Question 22

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

Answer 22

blocking code waits for each line of code to be resolved in the call stack, while non-blocking code moves code off to a task queue so that the call stack is not blocked from continuing to run

Question 23

What is a directory?

Answer 23

a pointer or container for files

Question 24

What is a relative file path?

Answer 24

the location of a file from the current file

Question 25

What is an absolute file path?

Answer 25

a complete path, the location of a file from anywhere | starts with a slash /

Question 26

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

Answer 26

fs module

Question 27

What method is available in the Node.js fs module for writing data to a file?

Answer 27

the fs.writeFile() method

Question 28

Are file operations using the fs module synchronous or asynchronous?

Answer 28

asychronous on fs module, though both are possible in node

Question 29

stdin

Answer 29

process input

Question 30

stdout

Answer 30

process output for normal output (logs to the terminal), ex. process.stdout.write()

Question 31

stderr

Answer 31

process output for errors

Question 32

TCP

Answer 32

machines connect to a network, then can connect to each other, sending data back and forth

Question 33

What is a client?

Answer 33

a program or computer which is a data requestor or accesses a service, or a web browser

Question 34

What is a server?

Answer 34

a program or computer which is a data provider or provides functionality to clients

Question 35

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

Answer 35

GET method

Question 36

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

Answer 36

HTTP method, request target, HTTP version

Question 37

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

Answer 37

protocol version, status code, status text

Question 38

What are HTTP headers?

Answer 38

additional information which specifies the request or describe the body included in the message

Question 39

Is a body required for a valid HTTP message?

Answer 39

No, it's optional

Question 40

What is NPM?

Answer 40

a JavaScript package manager, CLI, website, software registry

Question 41

What is a package?

Answer 41

a file in a directory with a package.json, reusable code which can be shared

Question 42

How can you create a package.json with npm?

Answer 42

the CLI command "npm init --yes"

Question 43

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

Answer 43

- a package that your app relies on to function | - npm install

Question 44

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

Answer 44

the package and any of its dependencies are installed in the 'node-modules' folder, also altering the package.json file

Question 45

How do you add express to your package dependencies?

Answer 45

npm install express

Question 46

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

Answer 46

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

Question 47

What is Express?

Answer 47

back end web application framework for Node.js

Question 48

How do you mount a middleware with an Express application?

Answer 48

app.use([path,] callback [,callback...]) method

Question 49

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

Answer 49

req (request) and res (response) objects

Question 50

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

Answer 50

application/json

Question 51

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

Answer 51

HTTP request methods mean what we want to do, but can actually do anything

Question 52

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

Answer 52

- parses the JSON request body to a JavaScript object | - when you will receive JSON from the request body

Question 53

npm run dev:server

Answer 53

- nodemon watches js so it auto restarts server

Question 54

Promise

Answer 54

an object representing the eventual completion or failure of asynchronous operation

Question 55

What are the three states a Promise can be in?

Answer 55

pending, fulfilled, rejected

Question 56

How do you handle the fulfillment of a Promise?

Answer 56

.then() method, pass a handler function as an argument

Question 57

How do you handle the rejection of a Promise?

Answer 57

.then() or .catch() method, pass a handler function as an argument