React.js

Question 1

What is React?

Answer 1

A JavaScript library for building user interfaces

Question 2

What is a React Element?

Answer 2

An object that describes an element

Question 3

How do you mount a react element to the DOM?

Answer 3

ReactDOM.render() method

Question 4

What is React’s lifecycle?

Answer 4

it’s what happens to a component over the course of it’s lifetime

Mount:
what happens when the component is first introduced to the page

Updating:
what happens when the component is interacted with or changed by the user

Unmounting:
what happens when the component finishes

Question 5

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

Answer 5

Value, onChange

Question 6

What are controlled components?

Answer 6

input elements that are controlled by React,

controlled by Value and onChange

Question 7

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

Answer 7

array.prototype.map()

Question 8

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

Answer 8

ideally, a property key that makes the object unique from it’s siblings

ie:
index, number

Question 9

When does React call a component’s componentDidMount method?

Answer 9

after the first successful render

Question 10

Name three React.Component lifecycle methods.

Answer 10

componentDidMount(), componentDidUpdate(), componentWillMount()

Question 11

How do you pass data to a child component?

Answer 11

through props