React.js

Question 1

What is React?

Answer 1

A JavaScript library for creating user interfaces. It is typically used with react-dom for web, and react-native for mobile.

Question 2

What is a React element?

Answer 2

A React element is when the element is created using React.createElement.

Question 3

How do you mount a React element to the DOM?

Answer 3

To mount a React element, ReactDOM.render() method is required. The React element and it’s container is needed for the arguments.

Question 4

What is JSX?

Answer 4

JSX is a syntax extension to JavaScript. It is mainly used with React to help describe how the UI should look.

Question 5

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

Answer 5

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Question 6

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

Answer 6

Webpack and Babel must be installed to the devDependencies. The npm packages react and react-dom are also required. Then running the build script to compile it all.

Question 7

What is a React component?

Answer 7

Components allow splitting the UI into independent pieces so they are more reusable and fit more situations.

Question 8

How do you define a function component in React?

Answer 8

Function keyword followed by the function name followed by the code block that returns the JSX syntax.

Question 9

How do you mount a component to the DOM?

Answer 9

By using the render method. The arguments would be the React element and the container which is the DOM query.

Question 10

What are props in React?

Answer 10

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Question 11

How do you pass props to a component?

Answer 11

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Question 12

How do you write JavaScript expressions in JSX?

Answer 12

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Question 13

How do you create “class” component in React?

Answer 13

Class keyword followed by the function name followed by the extends keyword then React.Component. Curly braces for the code block that include render() being defined, and a code block inside that as well to return the React element being created.

Question 14

How do you access props in a class component?

Answer 14

When using the props in a class component, the object this has to be used to define where props is coming from.

Question 15

What is the purpose of state in React?

Answer 15

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Question 16

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

Answer 16

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Question 17

What are controlled components?

Answer 17

A controlled component allows React to control when the state of form elements change by using setState().

Question 18

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

Answer 18

onChange and the value

Question 19

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

Answer 19

array.map()

Question 20

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

Answer 20

A unique string or ID for your key.

Question 21

What makes react so powerful? Is it the this.state and this.setState() and giving control of the DOM to react?

Answer 21

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Question 22

How do you specify the request method (GET, POST, etc.) when calling fetch?

Answer 22

The specific request would be included as the 2nd argument for fetch. The second argument would have an object literal and then the method property inside of it followed by the request.

Question 23

How do you pass data to a child component?

Answer 23

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Question 24

What does fetch() return?

Answer 24

The fetch returns a promise.

Question 25

What is the default request method used by fetch()?

Answer 25

GET