React Basics

1/25 React is mainly used for building ___.
- Database
- Connectivity
- User interface
- Design Platform
2/25 Which of the following methods in a React Component should be overridden to stop the component from updating?
- willComponentUpdate
- shouldComponentUpdate
- componentDidUpdate
- componentDidMount
3/25 What is used to pass data to a component from outside?
- setState
- render with arguments
- PropTypes
- props
4/25 What will happen if the following render() method executes?
```
render(){
let langs = ["Ruby","ES6","Scala"]
return (<div>
{langs.map(it => <p>{it}</p>)}
</div>)
}
```
- Displays the list of languages in the array
- Error. Cannot use direct JavaScript code in JSX
- Displays nothing
- Error. Should be replaced with a for..loop for correct output
5/25 How do you write an inline style which specifies the font-size:12px and color:red; in JSX?
- style={{font-size:12,color:'red'}}
- style={{fontSize:'12px',color:'red'}}
- style={fontSize:'12px',color:'red'}
- style={{font-size:12px,color:'red'}}
6/25 What is state in React?
- A persistant storage.
- An internal data store (object) of a component.
7/25 What are the two ways that data gets handled in React?
- state & props
- services & components
8/25 Ref is used for referring an element or component returned by ___.
- react()
- render()
- reduce()
- refer()
9/25 How can you access a prop named 'username' in a functional component?
```
const MyComponent = (props) => { ... }
```
- this.props.username
- props.username
- MyComponent.username
- username
10/25 What does 'PureComponent' do in React?
- Manages pure functions
- Prevents re-rendering if props and state have not changed
- Cleans up the component
- Enhances component performance
11/25 What is the default port where a create-react-app project runs?
- 3000
- 8080
- 5000
- 8000
12/25 Which method is necessary to define in a class component in React?
- componentDidMount()
- shouldComponentUpdate()
- render()
- getDerivedStateFromProps()
13/25 What is the purpose of 'PropTypes' in React?
- To specify the types of props a component can receive
- To document the component code
- To improve performance
- To provide default values to props
14/25 Which of these is not a feature of React?
- Virtual DOM
- Server-side rendering
- Built-in HTTP requests
- One-way data binding
15/25 In which lifecycle method do you make HTTP requests in a class component?
- componentDidMount
- componentWillMount
- componentDidUpdate
- componentWillUnmount
16/25 What is the purpose of the 'useEffect' hook?
- To handle state changes
- To create a new component
- To perform side effects in functional components
- To connect to a Redux store
17/25 How does React handle form submission?
- Using an event handler on the form element
- By automatically sending a POST request
- Using a dedicated React form submission library
- React cannot handle form submissions
18/25 What is 'prop drilling' in React?
- Passing props through multiple layers of components
- A method to define PropTypes in a component
- Drilling down to find errors in props
- A React library for handling properties
19/25 What does 'lifting state up' mean in React?
- Moving state to a common ancestor of components that need it
- Increasing the performance of the state updates
- Automatically handling state changes in child components
- Transferring state to a higher-order component
20/25 Which hook is used to memoize a callback function in React?
- useEffect
- useCallback
- useState
- useMemo
- useRef
21/25 Which method is the right choice to fetch data in a useEffect hook?
- componentDidMount
- useFetch
- fetch API
- getData()
- useDataFetching
22/25 What is the purpose of 'useReducer' in React?
- To handle component lifecycle
- For state management using a reducer function
- To reduce the bundle size of a React app
- To optimize rendering performance
23/25 Which is a valid way to create a component in React?
- function MyComponent() { return <div/>; }
- new ReactComponent(MyComponent)
- React.createComponent(MyComponent)
- class MyComponent extends ReactElement { ... }
24/25 Which of the following is a React hook?
- useComponent
- useState
- useReact
- useElement
25/25 In React, how do you pass data from a parent component to a child component?
- Using context
- Via global variables
- Through props
- By setting state in the child
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React Basics

1/25 React is mainly used for building ___.

2/25 Which of the following methods in a React Component should be overridden to stop the component from updating?

3/25 What is used to pass data to a component from outside?

4/25 What will happen if the following render() method executes?

5/25 How do you write an inline style which specifies the font-size:12px and color:red; in JSX?

6/25 What is state in React?

7/25 What are the two ways that data gets handled in React?

8/25 Ref is used for referring an element or component returned by ___.

9/25 How can you access a prop named 'username' in a functional component?

10/25 What does 'PureComponent' do in React?

11/25 What is the default port where a create-react-app project runs?

12/25 Which method is necessary to define in a class component in React?

13/25 What is the purpose of 'PropTypes' in React?

14/25 Which of these is not a feature of React?

15/25 In which lifecycle method do you make HTTP requests in a class component?

16/25 What is the purpose of the 'useEffect' hook?

17/25 How does React handle form submission?

18/25 What is 'prop drilling' in React?

19/25 What does 'lifting state up' mean in React?

20/25 Which hook is used to memoize a callback function in React?

21/25 Which method is the right choice to fetch data in a useEffect hook?

22/25 What is the purpose of 'useReducer' in React?

23/25 Which is a valid way to create a component in React?

24/25 Which of the following is a React hook?

25/25 In React, how do you pass data from a parent component to a child component?