Node.js

Question 1

What is Node.js?

Answer 1

an asynchronous event-driven JavaScript runtime

Question 2

What can Node.js be used for?

Answer 2

run JavaScript outside of a web browser to build applications.

Question 3

What is a REPL?

Answer 3

read-eval-print loop

a computer programming environment that takes user inputs, executes them, and returns the result.

Question 4

When was Node.js created?

Answer 4

Initial release was May 2009

Question 5

What back-end languages have you heard of?

Answer 5

Scripting Language (often interpreted)
JavaScript
Ruby
Python
PHP
Perl

Compiled Language 
C#
Java
Go
Haskell
typescript

Question 6

Questions I have:

Answer 6

What is a runtime?
- all of the stuff that surrounds your program that you didn’t write
What is a thread?
- what the cpu uses as a spot to pick up where it left off in running a program
What is dead-locking?
- when two threads are relying on each other to finish in order to execute the next step

Question 7

What is a computer process?

Answer 7

a process is the instance of a running computer program.

While a computer program is a passive collection of instructions typically stored in a file on disk, a process is the execution of those instructions after being loaded from the disk into memory.

Question 8

Roughly how many computer processes are running on your host operating system? (activity monitor)

Answer 8

628 processes

com.docker.hyperkit is using the most CPU

Question 9

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

Answer 9

the process object is a global object that can be accessed inside any module without requiring it.

Question 10

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

Answer 10

Since it is global you can just use its name like a variable that has already been defined

Question 11

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

Answer 11

array of strings

Question 12

What is the 3 tierd structure of full stack web development?

Answer 12

Front end process
Back end process
Data process (at least one)

Question 13

What is a JavaScript Module?

Answer 13

it is a single .js file.

Authors of Node.js programs strive to separate their code into modules that each provide a small chunk of functionality.

The program as a whole is the result of all these modules working together in concert.

Question 14

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

Answer 14

exports
require
module
\_\_filename
\_\_dirname

Question 15

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

Answer 15

process

global

Question 16

What is the idea behind modular programming?

Answer 16

decompose a solution to a large problem into many smaller solutions to sub-problems

Question 17

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

Answer 17

to tell which bits of code to export from a given file so other files are allowed to access the exported code.

Question 18

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

Answer 18

call the require function and pass in the relative file path of the module needed

Question 19

What is the JS event loop?

Answer 19

it is a way of understanding how code is executed from the stack, collecting and processing events, and executing queued sub-tasks

Question 20

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

Answer 20

non-blocking code is asynchronous code that is being executed while other code can be executed

blocking code is synchronous code that is being executed and not allowing other code to execute. Blocking code is on top of the call stack.

Question 21

What are the 4 concepts that set JS apart from other languages?

Answer 21

Prototypal Inheritance
how “this” works
closures
event loop

Question 22

What is a directory?

Answer 22

Is a special file that holds files

Question 23

What is a relative file path?

Answer 23

path that locates a file starting from the current directory

Question 24

What is an absolute file path?

Answer 24

a path from the root directory and the complete directory list required to locate the file

starts with a /

Question 25

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

Answer 25

fs module

Question 26

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

Answer 26

fs.writeFile(file, data[,options], callback

Question 27

Are file operations using the fs module synchronous or asynchronous?

Answer 27

they can be either depending on the method that is used

Question 28

What is NPM?

Answer 28

World’s largest software registry.

Open source developers from every continent use npm to share and borrow packages, and many organizations use npm to manage private development as well.

3 distinct components:

• website
• command line interface (CLI)
• registry

Question 29

What is a package?

Answer 29

is a file or directory that has a package.json file within it.

A package must contain a package.json file in order to be published to the npm registry.

Question 30

How can you create a package.json with npm?

Answer 30

On the command line navigate to the root directory of your package

Run the command npm init –yes

Question 31

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

Answer 31

Third party code that your application depends on

npm install

Question 32

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

Answer 32

You are able to use that dependency’s code in your own

updates the dependencies within package.json

Question 33

How do you add “express” to your package dependencies?

Answer 33

use npm install express

Question 34

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

Answer 34

.listen( ) method

Question 35

How do you mount a middleware with an Express application?

Answer 35

using the app.use( ) method

Question 36

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

Answer 36

req

res

Question 37

What are middleware functions?

Answer 37

functions that have access to the request object, the response object, and the next middleware function in the application’s request-response cycle.

Question 38

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

Answer 38

application/json

Question 39

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

Answer 39

Express.json parses incoming requests with JSON payloads

Needed when you are transmitting JSON data in web applications

Question 40

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

Answer 40

describe the intent of the client in what they want from the server

Question 41

What does express.static( ) return?

Answer 41

a function (middleware function)

Question 42

What is the local __dirname variable in a Node.js module?

Answer 42

the absolute path of the directory that the current module is in

Question 43

What does the join( ) method of Node’s “path” module do?

Answer 43

the path.join() method joins all given path segments together