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What is the main purpose of React?

To create user interfaces

To build web applications

To write server-side code

To debug JavaScript code

What does JSX stand for?

JavaScript XML

Java Script eXtension

JavaScript Extension

Java Script Xpress

How do you pass data from a parent component to a child component in React?

Props

State

Context

Refs

What is the correct syntax for declaring a function in JavaScript?

function myFunction {...}

var myFunction = () => {...}

let myFunction = {...}

const myFunction = () -> {...}

What is the name of the method that is called when a component is first created?

render()

init()

constructor()

mount()

What is the difference between an element and a component in React?

An element is a plain object representation of a DOM node while a component is a class or function that produces elements

An element is a class or function while a component is a plain object representation of a DOM node

An element is a plain object representation of a DOM node while a component is a string

An element is a string while a component is a class or function

What is the purpose of the useEffect hook in React?

To perform side effects after a component has been rendered

To update the state of a component

To handle events in a component

To initialize a component

which of the following is NOT true about react props

props help passing information from a parent component to a child component via a component element’s HTML attribute

Props are used to pass information up the component tree

the passed variables can be accessed in the child component as a property from the props object

props does not pass information from a child to a parent component

calling useState() would return:

an array of two variables: one representing the currect state and a function to update the current state

two strings

a promise

none

react state is used to make applications interactive and alter information over time

True

False

a function that has its signature in a parent component and called by a child component via props is :

an inline function

a callback handler

an event handler

none of the above

lifting the state up:

moving the state from a child component to the parent component

allows other child component to access the state

requires a callback handler if a child component wants to manage the state

all of the above

extracting data from javascript objects can be done through :

props

children

object destructuring

fetch( )

Variables created with object distructuring can only be named after the keys of the object

True

False

Destructuring the props object in the function signature of the component

makes the code confusing

requires Refactoring the component's arrow function from concise body to block body

makes the code repetetive

none of the above

the props object is as follows {title:'react', id:13} to access these values in a child component:

const App ( { title,id } )=>{...}

const App ()=>{ const { title , id }=props ; }

const App ()=>{ const newTitle=props.title ; const newId=props.id ; }

all of the above

which of the following is not a side-effect :

storing data in the browser's local storage

data fetching

updating the state of the component

requesting data from remote APIs or servers

which of the following is not a method for js localStorage :

getItem()

searchItem()

removeItem()

setItem()

which of the following is not a method for js localStorage :

getItem()

searchItem()

removeItem()

setItem()

const test=true;

test ? console.log('passed') : console.log('denied') ;

output : passed

output : denied

output : passed denied

output : error

useEffect() takes 2 arguments : a function that runs the side-effect and a dependency array

True

False

The dependancy array of the usestate() hook :

if it's not included, the side-effect function will run on every render

if it's empty, the side-effect function will only run once after the component renders for the first time

triggers the side-effect function everytime its content changes

all of the above

const Parent=()=>{

return(

<Child> hello world </Child>

); };

contst Child=({children})=>{

return(

<h1> {children} </h1>

); };

output : children

output : hello world

output : error

none of the above

children prop in react :

makes the component elements behave similarly to native HTML

makes it possible to control a component's XML directly from its instantiation

Anything passed between component elements can be accessed as children in the component

all of the above

removeItem() will execute when the button is clicked

this will cause an infinite loop as the removeItem() is called and not being passed

removeItem() is passed as props

none of the above

all of these are alternatives to pass an event handler function with a parameter exept :

onClick={removeItem(item)}

onClick={()=>removeItem(item)}

onclick={removeItem.bind(null,item)}

const remove=()=>{ removeItem(item)}; return( ...

delays in data arrival can be handled using :

props

side-effects

promise

callback handlers

setTimeOut() is used for :

blocking data

fetching data

simulating data arrival delays

resolving promises

{ test &&

hello world

} is equivalent to :

test +

hello world

if (test==true) {

hello world

}

if (test==true AND p=='hello world') {return}

this syntax is not valid

The '&&' (AND) operator and the ternary( ...? .... : ...) operator are used for conditional rendering :

True

False

const ch1='ahmad mohsen' ;

const ch2='piw piw' ;

const ch3=`${ch1}${ch2}` ;

ch3='ahmadmohsenpiwpiw'

ch3=' '

ch3 ='ahmad mosen piw piw'

none of the above

fetch() takes 2 arguments to retrieve data from an API

a url and a dependency array

two strings

state and a state handler

promise and a dependency array

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