React

Question 1

What is React?

Answer 1

React is a JavaScript library for creating user interfaces.

Question 2

What is a React element?

Answer 2

A React element is an object representation of a DOM node.

Question 3

How do you mount a React element to the DOM?

Answer 3

ReactDom.render

Question 4

What is JSX?

Answer 4

a syntax extension to JavaScript. We recommend using it with React to describe what the UI should look like.

Question 5

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

Answer 5

JSX just provides syntactic sugar for the React.createElement(component, props, …children) function

Question 6

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

Answer 6

babel-loader and the plugin

Question 7

What is a React component?

Answer 7

Components let you split the UI into independent, reusable pieces, and think about each piece in isolation.

Question 8

How do you define a function component in React?

Answer 8

function CustomBtn() {
  return Click Me!;
}

“return jsx”

Question 9

How do you mount a component to the DOM?

Answer 9

ReactDOM.render

Question 10

What are props in React?

Answer 10

It is an object which stores the value of attributes of a tag and work similar to the HTML attributes.

Question 11

How do you pass props to a component?

Answer 11

Define a function and pass it as a parameter

Question 12

How do you write JavaScript expressions in JSX?

Answer 12

wrap them with curly braces

Question 13

How do you create “class” component in React?

Answer 13

class and extends

Question 14

How do you access props in a class component?

Answer 14

this.props.whateverhere

Question 15

What is the purpose of state in React?

Answer 15

represent an information about the component’s current situation

Question 16

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

Answer 16

Pass event handlers and other functions as props to child components:

Question 17

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

Answer 17

.map

Question 18

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

Answer 18

The best way to pick a key is to use a string that uniquely identifies a list item among its siblings. Most often you would use IDs from your data as keys:

Question 19

What are controlled components?

Answer 19

those in which form data is handled by the component’s state.