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Question 1
Which lifecycle method is called before the component is mounted to the DOM?
componentDidMount()
componentWillMount()
constructor()
render()
Question 2
Which of the following is true about class components?
Class components cannot use state
Class components must use the render method
Class components do not support lifecycle methods
Class components are faster than functional components
Question 3
What will happen in this class component?
class Demo extends React.Component {
constructor(props) {
super(props);
this.state = { count: 0 };
this.setState({ count: 1 });
}
render() {
return <div>{this.state.count}</div>;
}
}
The component renders 1
The component renders 0
Infinite re-render loop
Error: Cannot call setState in constructor
Question 4
Which lifecycle method is called immediately after a component is mounted?
componentWillUnmount
componentDidUpdate
componentDidMount
getSnapshotBeforeUpdate
Question 5
What does componentDidUpdate lifecycle method do?
It is called when the component is unmounted
It is called when the component receives new props or state
It is called before the component mounts
It is called only once after the component is first created
Question 6
Which lifecycle method is called before a component is removed from the DOM?
componentWillUnmount
componentDidMount
componentDidUpdate
getSnapshotBeforeUpdate
Question 7
In class components, how can you initialize the state?
By using this.setState() in the constructor
By declaring state directly inside the component
By using the render method
By using the componentDidMount method
Question 8
What will be the output of the following code?
It will log the initial state 0 on every render.
It will log the incremented state each time the button is clicked.
It will cause an error since the state cannot be updated in the render method.
It will display undefined
Question 9
Given the following class component, what will happen when the button is clicked?
The counter will display NaN
The counter will display 0, and clicking the button will increment the count
The counter will not render anything.
The component will crash when the button is clicked.
Question 10
What does the following code do in a class component?
It logs a message only when the component is first mounted
It logs a message when the component is about to mount
It logs a message every time the component updates
It logs a message when the component is unmounted
There are 10 questions to complete.
