React.js Flashcards

1
Q

What is React?

A

a JavaScript library for creating user interfaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a React element?

A

object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How do you mount a React element to the DOM?

A

ReactDOM.render()

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is JSX?

A

syntax extension to JavaScript (JS plus some more)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

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

A

In order to use the methods on the react object (ex. react.createElement)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

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

A

Use babel loader and the plugin @babel/plugin-transform-react-jsx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a React component?

A

a JS function that accepts props as inputs and returns react elements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do you define a function component in React?

A

function definition or a class, capitalize the names

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do you mount a component to the DOM?

A

ReactDOM.render +

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are props in React?

A

properties passed as inputs in a react component function, objects { }

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do you pass props to a component?

A

as a key=”value” pair inside react element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do you write JavaScript expressions in JSX?

A

{ }

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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

A

array.prototype.map

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

ID number or name from data that distinguishes it from another piece of sibling data

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do you create “class” component in React?

A
class ComponentName extends React.Component {
    render() {
    }
}
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do you access props in a class component?

A

this.props

17
Q

What is the purpose of state in React?

A
  • *implies the passage of time and the change of state

* * keep track of values that change over time

18
Q

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

A

attached as a prop to your react element returned from the render method

19
Q

What are controlled components?

A

form input whose value is controlled by React

20
Q

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

A

value and onChange

21
Q

When does React call a component’s componentDidMount method?

A

Right when component is mounted in ReactDOM.render

22
Q

Name three React.Component lifecycle methods.

A

componentDidMount
componentWillUnmount
componentDidUpdate

23
Q

How do you pass data to a child component?

A

by passing the data through the props when rendering/returning the children react element