Node.js

Question 1

What is Node.js?

Answer 1

Node.js is an open-source, cross-platform JS runtime environment

Running a javascript code without being in the web broswer

Question 2

What can Node.js be used for?

Answer 2

Used for server-side programming
primarily deployed for non-blocking, event-driven servers like traditional websites and back-end API services

Build a back-end, make command-line app, automated scripts in JS

Question 3

What is a REPL?

Answer 3

A read-eval-print loop:
- it reads, evaluates, prints the result and then loop it by writting again in the next line

examples: console.logs() & browser dev console

Question 4

When was Node.js created?

Answer 4

2009 - 2011

Question 5

What back end languages have you heard of?

Answer 5

ruby, PHP, python, C++, java, C, C#, JS, perl, kotlin

Question 6

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

Answer 6

control over information that is executing the current node

Question 7

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

Answer 7

You can just reference it because it is a global object

Question 8

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

Answer 8

it is an array of strings

Question 9

What is a JavaScript module?

Answer 9

It is a specific individual file

Question 10

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

Answer 10

__dirname & __filename & exports & module & require()

Question 11

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

Answer 11

global & process & console object

Question 12

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

Answer 12

Module.exports are the instructions that tell Node.js which bits of code (functions, objects, strings, etc) to export from a given file so that other files are allowed to access the exported code

To expose values to grab other files

Question 13

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

Answer 13

const variableName = require(‘fileName’)

Pulling information from another module

Question 14

What is the JavaScript Event Loop?

Answer 14

part of the JS runtime environment that pushes asynchronous callbacks onto the call stack when the call stack is clear.

example: ajax, delay time

Question 15

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

Answer 15

blocking: operations that block further execution until that op finishes - need to wait for other things to finish - anything that is sitting on the call stack
- For example: for-loop

non-blocking: code that doesn’t block execution - other things will execute while waiting for this code to be executed when there’s like a delay
- HTTP request,

Question 16

What is a directory?

Answer 16

a special file that lists files and directories

Question 17

What is a relative file path?

Answer 17

the location that is relative to a current directory

Question 18

What is an absolute file path?

Answer 18

specifying the location of a file or directory from the root directory - using a ‘/’

takes you to the file from anywhere

Question 19

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

Answer 19

fs module

Question 20

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

Answer 20

fs.writefile()

Question 21

Are file operations using the fs module synchronous or asynchronous?

Answer 21

both

Question 22

What is NPM?

Answer 22

It’s a software registry. Open-source developers to share and borrow packages. It consists of these three things: website, cli, and registry.

Question 23

What is a package?

Answer 23

directory with one or more files & package.json

Question 24

How can you create a package.json with npm?

Answer 24

npm init –yes

Question 25

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

Answer 25

npm install ‘packageFile’
Dependency: a third-party code that your application depends on. piece of software that your software will need.

Question 26

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

Answer 26

The package.json is updated with the new dependency and the package is downloaded from NPM registry to node_modules

Question 27

How do you add express to your package dependencies?

Answer 27

npm install express

Question 28

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

Answer 28

app.listen()
listen - servers are listening to the incoming in that port

Question 29

How do you mount a middleware with an Express application?

Answer 29

app.use((req, res))
call the use method

Question 30

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

Answer 30

req & res

Question 31

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

Answer 31

application/json

Question 32

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

Answer 32

it parses incoming requests with JSON payloads and is based on body-parser

We need this when we need to receive JSON from the API

Question 33

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

Answer 33

It gives specific action to be performed for its method request

Question 34

What does express.static() return?

Answer 34

a path - returns a middleware

Question 35

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

Answer 35

name of the current module or the path to the current module

Question 36

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

Answer 36

joins all given path segments together

Question 37

What does fetch() return?

Answer 37

a Promise that resolves a Response object

Question 38

What is the default request method used by fetch()?

Answer 38

GET

Question 39

How do you specify the request method (GET, POST, etc.) when calling fetch?

Answer 39

fetch(‘ ‘, { method: ‘ ‘});

Question 40

When does React call a component’s componentDidMount method?

Answer 40

immediately after a component is mounted (inserted into the tree).

Question 41

Name three React.Component lifecycle methods.

Answer 41

componentDidMount()
componentDidUpdate()
componentWillUnmount()

Question 42

How do you pass data to a child component?