JavaScript

Question 1

What are es6 and es7 in JS

Answer 1

Es stands for ECMAscriptn
And they are two versions or updates of js
Es6 is in 2015
Es7 is in 2016
Each one added different features

Question 2

How do you connect your JS with your code ?

Answer 2

Script tag
Src
In the body at the end

Question 3

How to use DOM functions to point to html elemets

Answer 3

document.getelementbyid
Getelementsbyclassname
Queryselector
Queryselectorall

Question 4

What is $ used for in js

Answer 4

Allows you to embed variables inside a string , so changing variable within a static string

Question 5

Explain destructuring objects(say the syntax)

Answer 5

It is a way to extract values from objects or arrays and assign them to variables using shorter syntax.

Question 6

What type of data can you have in an object

Answer 6

Numerical
Objects
Array
String boolean
Null
Undefined

Question 7

How to use destructuring when you have nstead objects?

Answer 7

Const{objectName:{key}}=big object name

Question 8

What are the components of an object

Answer 8

Const object ={ Key:value, ———}
And const object can change values inside

Question 9

How does destructuring work in array?

Answer 9

So as said we are initializing values in easier sytax
const [name]=array name, or [array]
Now name will point to the first element in the array
And you can add other variables after name to point to other values in the array in order

Question 10

How can you shorten the syntax of an object inside a function and what do you call it

Answer 10

You do const object={ parameter1,parameter2,…..}
This will make the object have the parameter name as key and the passed value through the the value of that key.
call Object Property Shorthand

Question 11

What is template literal

Answer 11

a feature added in es6 that allows you to imped variables in strings, concatenate strings, help with readability, and multi line string while using the backtick

Question 12

What is for of loop and what is it’s syntax

Answer 12

A loop where you can iterate through stuff like strings are arrays easily
The syntax is for (let/const anyname of array name or string name)
{Do work here (the name you chose will point to each array element and you can do whatever you want, but it will not modify the array it self, so it will be a variable pointing to the array elements not referencing to the actual array}

Question 13

What is ‘ called

Answer 13

Backtick

Question 14

Why is backtick better than “ or single quotation

Answer 14

Because it is one of the template literature that allows text formatting happen like spaces and new lines.
Any thing you write inside will be written in the console like you wrote.
Without backtick you cannot use variables inside {}

Question 15

How to do a new line in console log when using a “ or single

Answer 15

By \n

Question 16

Talk about spread operator

Answer 16

Now when you make an array =array1
Array will now reference to it
But with spread operator you shallow copy the content of the array to a new array and you can modify stuff.
array=[…array1]
can also used with objects
you can merge, over ride, add new values or just simply copy , using spread operator

Question 17

Does spread operator work to copy objects?

Answer 17

Yes
So …name
Means copy all the data inside

Question 18

What is arrow function

Answer 18

A way to make a function but anonymously

Question 19

What are the ways to make a function

Answer 19

unanimously:
const camelCase= function (){}
Or
Const camelCase= ()=>{}
normal:
function camelCase (parameters)

Question 20

How to make a normal function in js

Answer 20

function name () {}

Question 21

What is the implicit return feature in fucntions

Answer 21

When you have only one line in the function and you just write it without return or {} (only for arrow) not named functions it will consider it as return automatically

Question 22

Explain this
const name = (food=something)=>{} and what do you call it

Answer 22

This means when you forget to pass a parameter your parameter will be automatically set to something, if you pass, it will be updated
Called default parameter

Question 23

Explain includes() function

Answer 23

Will return true or false , will iterate through an array and check if it has that value or not

Question 24

What do you need to do imports and exports when working with js?

Answer 24

You need nodejs at least vs 12
Check node —version
And you name your files .mjs
M is for module
add type ‘module’ is your script tag and don’t forget to put .mjs in src

Question 25

Does folders with package.JSON need to be named with .mjs

Answer 25

No, they already have module Like react So you can import and export without .mjs

Question 26

Why do you use imports and exports

Answer 26

Assume you have multi js files and you have a set of data that you want to move to another file You export it from one and import it to another

Question 27

What is a class

Answer 27

It has the properties (variables , functions) that describe a set of objects

Question 28

What is an instance?

Answer 28

It is a instantiation of a class (عمل مثيل) where it has all the properties in that class

Question 29

What are some needed stuff in the class?

Answer 29

Constructor You write Constructor(variables must be passed when making an object) {this.parameter=parameter;} . . . to print ex: print(){ console.log(this.x,this.y) }

Question 30

How to make an instance or object

Answer 30

const name =new class (variables)

Question 31

Can you export classes?

Answer 31

Yes by writing export and initializing the class normally (same as other stuff)

Question 32

How to inhert classes in js

Answer 32

By using extends Class Name extends Parent { …. }

Question 33

Can extended classes override original functions from parent

Answer 33

Yes and when calling the function it will be called, otherwise the parent function will be called

Question 34

What does super function do and what is it’s syntax

Answer 34

Used in class inhertance It calls the constructor of the parent class within the extended class. You must always call it when doing a child constructor

Question 35

Talk about promises

Answer 35

A promise represents a value (final result) is not immediately known, it waits for the asynchronous operation like fetching data to be over and the value will be known later . Used to handle asynchronous operations

Question 36

Asynchronous functions are

Answer 36

Functions that don’t wait for tasks to happen like API calls or fetching data

Question 37

Is JS async?

Answer 37

Yes

Question 38

What happens when a promise is created

Answer 38

It promises that it will get back with a result ( the async operator will complete) either with success or reject So it does not promise a full success chance

Question 39

Why are .then and .catch used for

Answer 39

After the result of operation is known, it uses them to handle the results Then for success Catch for error

Question 40

What does await do

Answer 40

It pauses excution until promise value is known

Question 41

Is promise a class?

Answer 41

Yes , and it has reject and resolve functions

Question 42

What are reject and resolve?

Answer 42

They are functions in Promise class and they call either then or catch and they will have the values that you put in reject and resolve

Question 43

What is set timeout function

Answer 43

Is a js function that delays the excution of function settimeout(function,delay in ms)

Question 44

how to name functions in js?

Answer 44

by using camelCase

Question 45

how to name classes is js?

Answer 45

by using Capital Letter at the start of your class name

Question 46

when using getElementsByClassName how do they appear in the consol?

Answer 46

as a htmlcollection

Question 47

is it a must to use ; in js?

Answer 47

no

Question 48

when using querySelectorAll how do they appear in the consol?

Answer 48

you get nodelist

Question 49

what does nodelist and htmlcollection have?

Answer 49

they have the elements and all the needed info about the,

Question 50

how to make a null value or undefined value in objs?

Answer 50

x:nuill, y:undefined and you can access them by obj.x or obj.y

Question 51

what happens when you console.log(myObjs)

Answer 51

it will print the object normally

Question 52

assume myFunction is a Function name, what is the difference between myFunction ; and myFunction ();

Answer 52

myFunction will not be called unless something ( an event happenns) myFunction () will be called once the page is loaded

Question 53

what happens when you console.log(funtionName) and console.log(funtionName())

Answer 53

.funtionName will print the text of the function .funtionName() will call the function and will print what it returns

Question 54

how to do imports?

Answer 54

import {name} from './index.mjs' or what ever your file name is

Question 55

What is a promise example implementation?

Answer 55

const myFunction =()=>{ return new Promise ((resolve,reject)=>{ setTimeout(() => { const error=true; if(error) resolve("all good") else reject("bad service") }, 3000); }) } myFunction() .then((data)=>{console.log(data)}) .catch((error)=>{console.error(error)})