React

Question 1

What is React?

Answer 1

A JS library used for building user interface

Question 2

What is a React element?

Answer 2

A plain object describing a component instance or DOM node and its desired properties

Question 3

How do you mount a React element to the DOM?

Answer 3

you have to create a root of the container and then render the react element

Question 4

What is JSX?

Answer 4

A syntax extension to javascript that describes what UI should look like

Question 5

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

Answer 5

React has to be in the scope in order to create the elements

Question 6

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

Answer 6

Using a webpack config

Question 7

What is a React component?

Answer 7

components are like JavaScript functions. They accept arbitrary inputs (called “props”) and return React elements describing what should appear on the screen.

Question 8

How do you define a function component in React?

Answer 8

Just like a JavaScript function

Question 9

How do you mount a component to the DOM?

Answer 9

First you must query the dom and then create a root and then render the root

Question 10

What are props in React?

Answer 10

a type of object where the value of attributes of a tag is stored

Question 11

How do you pass props to a component?

Answer 11

inside a string literal the object props. a property

Question 12

How do you write JavaScript expressions in JSX?

Answer 12

place the expression in curly braces

Question 13

How do you create “class” component in React?

Answer 13

class keyword followed by name extends class object

Question 14

How do you access props in a class component?

Answer 14

the this keyword

Question 15

What is the purpose of state in React?

Answer 15

It allows us to manage and change data

Question 16

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

Answer 16

you use the bind method and onclick attribute

Question 17

What are controlled components?

Answer 17

A controlled component is a component that renders form elements and controls them by keeping the form data in the component’s state.

Question 18

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

Answer 18

value and onChange

Question 19

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

Answer 19

map method

Question 20

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

Answer 20

unique identifier

Question 21

When does React call a component’s componentDidMount method?

Answer 21

The commit phase and last in mounting order

Question 22

Name three React.Component lifecycle methods.

Answer 22

didMoun, componentDidUpdate, and componentWillUnmount

Question 23

How do you pass data to a child component?