React Test

If you wanted to import just the Component from the React library, what syntax do you use?

IMPORT REACT.COMPONENT FROM 'REACT'

IMPORT { COMPONENT } FROM 'REACT'

IMPORT COMPONENT FROM 'REACT'

IMPORT [ COMPONENT ] FROM 'REACT'

If a function component should always render the same way given the same props, what is a simple performance optimization available for it?

IMPLEMENT THE USEREDUCER HOOK.

IMPLEMENT THE SHOULDCOMPONENTUPDATE LIFECYCLE METHOD.

IMPLEMENT THE USEMEMO HOOK.

WRAP IT IN THE REACT.MEMO HIGHER-ORDER COMPONENT.

If you see the following import in a file, what is being used for state management in the component? import React, { useState } from

REACT HOOKS

STATEFUL COMPONENTS

MATH

CLASS COMPONENTS

What is the testing library most often associated with React?

CHAI

SINON

JEST

MOCHA

To get the first item from the array ("cooking") using array destructuring, how do you adjust this line? const topics = ["cooking", "art", "history"];

CONST [FIRST] = ["COOKING", "ART", "HISTORY"];

CONST [] = ["COOKING", "ART", "HISTORY"];

CONST FIRST = ["COOKING", "ART", "HISTORY"];

CONST [, FIRST]["COOKING", "ART", "HISTORY"];

How do you handle passing data through the component tree without having to pass props down manually at every level?

REACT SEND

REACT CONTEXT

REACT ROUTER

REACT PINPOINT

What should the console read when the following code is run? const [, , animal] = [

CAT

HORSE

UNDEFINED

MOUSE

What is the name of the tool used to take JSX and turn it into createElement calls?

BABEL

BROWSER BUDDY

JSX EDITOR

REACTDOM

Why might you use useReducer over useState in a React component?

WHEN YOU WANT TO IMPROVE PERFORMANCE

WHEN YOU NEED TO MANAGE MORE COMPLEX STATE IN AN APP

WHEN YOU WANT TO BREAK YOUR PRODUCTION APP

WHEN YOU WANT TO REPLACE REDUX

What can you use to handle code splitting?

REACT.SPLIT

REACT.LAZY

REACT.FALLBACK

REACT.MEMO

When do you use useLayoutEffect?

TO CHANGE THE LAYOUT OF THE SCREEN

WHEN YOU NEED THE BROWSER TO PAINT BEFORE THE EFFECT RUNS

TO OPTIMIZE FOR ALL DEVICES

TO COMPLETE THE UPDATE

Why is it important to avoid copying the values of props into a component's state where possible?

BECAUSE YOU SHOULD NEVER MUTATE STATE

BECAUSE GETDERIVEDSTATEFROMPROPS() IS AN UNSAFE METHOD TO USE

BECAUSE YOU WANT TO ALLOW DATA TO FLOW BACK UP TO THE PARENT

BECAUSE YOU WANT TO ALLOW A COMPONENT TO UPDATE IN RESPONSE TO CHANGES IN THE PROPS

What is the children prop?

A PROPERTY THAT LETS YOU PASS COMPONENTS AS DATA TO OTHER COMPONENTS

A PROPERTY THAT ADDS CHILD COMPONENTS TO STATE

A PROPERTY THAT LETS YOU SET AN ARRAY AS A PROPERTY

A PROPERTY THAT LETS YOU PASS DATA TO CHILD ELEMENTS

Which attribute do you use to replace innerHTML in the browser DOM?

INJECTHTML

STRANGEHTML

DANGEROUSLYSETINNERHTML

WEIRDSETINNERHTML

Which term commonly describes React applications?

CLOSED

INTEGRATED

DECLARATIVE

IMPERATIVE

When using webpack, why would you need to use a loader?

TO PUT TOGETHER PHYSICAL FILE FOLDERS

TO LOAD EXTERNAL DATA

TO LOAD THE WEBSITE INTO EVERYONE'S PHONE

TO PROCESS FILES

A representation of a user interface that is kept in memory and is synced with the "real" DOM is called what?

VIRTUAL DOM

DOM

VIRTUAL ELEMENTS

SHADOW DOM

To create a constant in JavaScript, which keyword do you use?

CONSTANT

CONST

LET

VAR

What do you call a React component that catches JavaScript errors anywhere in the child component tree?

ERROR BOSSES

ERROR BOUNDARIES

ERROR HELPERS

ERROR CATCHERS

In which lifecycle method do you make requests for data in a class component?

COMPONENTDIDMOUNT

COMPONENTWILLRECEIVEPROPS

CONSTRUCTOR

COMPONENTWILLMOUNT

React components are composed to create a user interface. How are components composed?

BY NESTING COMPONENTS

WITH CODE SPLITTING

WITH WEBPACK

BY PUTTING THEM IN THE SAME FILE

All React components must act like _____ with respect to their props.

HIGHER-ORDER FUNCTIONS

RECURSIVE FUNCTIONS

MONADS

PURE FUNCTIONS

Why might you use a ref?

TO REFER TO ANOTHER JS FILE

TO CALL A FUNCTION

TO BIND THE FUNCTION

TO DIRECTLY ACCESS THE DOM NODE

What is sent to an Array.map() function?

THE NUMBER OF TIMES YOU WANT TO CALL THE FUNCTION

A CALLBACK FUNCTION THAT IS CALLED ONCE FOR EACH ELEMENT IN THE ARRAY

A STRING DESCRIBING WHAT THE FUNCTION SHOULD DO

THE NAME OF ANOTHER ARRAY TO ITERATE OVER

Why is it a good idea to pass a function to setState instead of an object?

SETSTATE IS ASYNCHRONOUS AND MIGHT RESULT IN OUT OF SYNC VALUES.

IT AUTOMATICALLY UPDATES A COMPONENT.

IT IS MORE FUNCTIONAL THAN AN OBJECT.

IT MAKES SURE THAT THE OBJECT IS NOT MUTATED.

Which package contains the render() function that renders a React element tree to the DOM?

RENDER

DOM

REACT

REACTDOM

How do you set a default value for an uncontrolled form field?

IT DOES NOT HAVE A NAME PROP.

USE DEFAULTVALUE PROPERTY.

USE DEFAULT PROPERTY.

USE VALUE PROPERTY.

What can you use to wrap Component imports in order to load them lazily?