React

Question 1

What is React?

Answer 1

A JS library for building UI’s

Question 2

What is a React element?

Answer 2

An object that describes the element

Question 3

How do you mount a React element to the DOM?

Answer 3

ReactDom.render(element, container)

Question 4

What is JSX?

Answer 4

A JavaScript syntax extension

Question 5

Why must the React object be imported when authoring JSX in a module?

Answer 5

JSX compiles into React.createElement

Question 6

How can you make Webpack and Babel work together to convert JSX into valid JavaScript?

Answer 6

Babel transform react jsx

Question 7

What is a React component?

Answer 7

A function that accepts a prop and returns a react element

Question 8

How do you define a function component in React?

Answer 8

function FuncName(props){
return (<h1>hi</h1>);
}
function keyword followed by function name with parameter props.. inside code block return statement with element that represents DOM tags

Question 9

How do you mount a component to the DOM?

Answer 9

ReactDom.render(, container)

Question 10

What are props in React?

Answer 10

A javascript object

Question 11

How do you pass props to a component?

Answer 11

function name with variable initialized to prop value

Question 12

How do you write JavaScript expressions in JSX?

Answer 12

expression inside curly braces

Question 13

How do you create “class” component in React?

Answer 13

class keyword FunctionName extends React.Component opening code block render() definition code block
return react element

Question 14

How do you access props in a class component?

Answer 14

this.props.element

Question 15

What is the purpose of state in React?

Answer 15

Represents information on the elements current situation and allows it to be updated

Question 16

How to you pass an event handler to a React element?

Answer 16

eventName={eventHandler}

name of the event equals the event handler inside of curly braces

Question 17

What are controlled components?

Answer 17

The component that renders the form also controls what happens on user input and keeps the form data in the state

Question 18

What two props must you pass to an input for it to be “controlled”?

Answer 18

onChange & value

Question 19

What Array method is commonly used to create a list of React elements?

Answer 19

map

Question 20

What is the best value to use as a “key” prop when rendering lists?

Answer 20

a property in the object