0403 (express static, api reg etc., react routing etc.)

Question 1

What is the purpose of the Express Static middleware?

Answer 1

it serves static files

Question 2

What does express.static() return?

Answer 2

it returns a middlewear

Question 3

What are several examples of static files?

Answer 3

images, index.html, main.js, styles.css? files u just get and deliver as is.

extra:
non static files: sound files, files u need server for, files you import (you are running it)

Question 4

What is a good way to serve application images using Express?

Answer 4

put them in an images folder inside (public)?

Question 5

What does fetch() return?

Answer 5

A Promise that resolves to a Response object.

Question 6

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

Answer 6

GET

Question 7

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

Question 8

How does fetch report errors?

Answer 8

fetch is a promise so it can do that

Question 9

How can useEffect be used to load data for a component?

Answer 9

with fetch?

Question 10

What browser function can be used to make HTTP requests to a server in React?

Answer 10

fetch

Question 11

How do you use useEffect to load component data just once when the component mounts?

Answer 11

by using empty brackets (an empty array) as a dependency?, e.g. [ ]

Question 12

How do you use useEffect to load component data every time the data key changes?

Answer 12

pass that key as a dependency in the array, [ ]

Question 13

In a large-scale production app, what are some better alternatives for loading and managing backend data?

Answer 13

Some good open source packages are React Query and Vercel SWR work.

Question 14

errors:
500s are?
400s are?

which is client/server?

Answer 14

500 server
400 client

Question 15

What is the purpose of React “context”?

Answer 15

To be able to pass data from a (distant) parent to many children instead of manually passing props indiviaually
.

Question 16

What values can be stored in context?

Answer 16

static values and also values which can be updated

Question 17

How do you create context and make it available to the components?

Answer 17

import “crateContext”:

import { createContext } from ‘react’;

create it in a file and export it:

export const LevelContext = createContext(1);

Question 18

How do you access the context values?

Answer 18

by wrapping children which are going to use it and passing to them thru a parent (close or distant)

Question 19

When would you use context? (in addition to the best answer: “rarely”)

Answer 19

when u don’t want to set data manually on many children

Question 20

react-custom-hooks

Question 21

react-custom-hooks

Question 22

What is a React custom hook?

Question 23

When are custom hooks useful? When are they not required?

Answer 23

writing less with ordinary hooks.

when another hook is NOT called.

Question 24

What is the syntax (or naming convention) for writing a custom hook?

Question 25

How do you call a custom hook?

Question 26

When do custom hooks execute?

Question 27

What are unit tests?

Answer 27

A way to check if code (usually a function) meets certain conditions and does what is intended. It’s like console logging in that you can check your work, but much more sophisticated.

Officiallty:
A unit test is a way of testing a unit - the smallest piece of code that can be logically isolated in a system. In most programming languages, that is a function, a subroutine, a method or property.

source:
https://smartbear.com/learn/automated-testing/what-is-unit-testing/

Question 28

Why is it important to write unit tests?

Answer 28

To test code, to refactor code, debug

Question 29

What code should be tested with a unit test? What code is not well suited for unit tests?

Answer 29

a unit. small piece of code.

Question 30

What is Jest? What are some other popular JavaScript unit testing frameworks?

Answer 30

A unit testing framework for JS.

Others are Jest, Mocha, Jasmine, AVA

Question 31

In JavaScript, when is scope determined?

Question 32

What allows JavaScript functions to “remember” values from their surroundings?

Question 33

What values does a closure contain?

Answer 33

all that are in scope

Question 34

When is a closure created?

Answer 34

when a function is created

Question 35

How can you tell if a function will be created as a closure?

Question 36

In React, what is one important case where you need to know if a closure was created?

Answer 36

if u have a function that is a dependency in ur useEffect, u need to know if it’s a closure.

you will get a lint error if it’s a closure. to fix this, wrap the function and use a callback.

Question 37

what is a closure

Answer 37

a function which has a reference to a function and varialbes outside of it that it uses in the function