React JS MCQs with answers Page - 19

Here, you will find a collection of MCQ questions on React JS. Go through these questions to enhance your preparation for upcoming examinations and interviews.

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Q. How do you prevent a form submission from refreshing the page in React?

  • (A) By calling event.preventDefault() in the submit handler
  • (B) By using type='button' on the submit button
  • (C) By removing the form tag
  • (D) By using useState hook

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Q. Which is a valid way to apply inline styles in React?

  • (A) style='color: red;'
  • (B) style={{ color: 'red' }}
  • (C) style={color: red}
  • (D) style='color:red;'

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Q. What will the following JSX compile to?
<div>Hello, {name}</div>

  • (A) Creates a div with static text
  • (B) Creates a div with the value of variable name inserted
  • (C) Throws an error if name is undefined
  • (D) Nothing is rendered

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Q. How do you conditionally render a component in React?

  • (A) Using if-else statements outside JSX
  • (B) Using ternary operators inside JSX
  • (C) Using logical && operator inside JSX
  • (D) All of the above

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Q. What is the correct way to update state based on the previous state?

  • (A) setState(newState)
  • (B) setState(prevState => newState)
  • (C) this.state = newState
  • (D) state = newState

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Q. Which of these hooks is used for complex state logic or multiple related states?

  • (A) useState
  • (B) useReducer
  • (C) useMemo
  • (D) useCallback

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Q. Which package is typically used to enable routing in React applications?

  • (A) react-navigation
  • (B) react-router-dom
  • (C) redux-router
  • (D) react-router-native

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Q. Which of these is a controlled component in React?

  • (A) An input element with value controlled by React state
  • (B) An input element with defaultValue attribute
  • (C) An input element with no value attribute
  • (D) An uncontrolled input

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Q. What does the React.Fragment component do?

  • (A) Renders a hidden div
  • (B) Allows grouping multiple children without adding extra nodes
  • (C) Creates a portal
  • (D) Creates a context provider

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Q. How can you optimize a React component to prevent unnecessary re-renders?

  • (A) Using PureComponent or React.memo
  • (B) Always calling setState
  • (C) Removing keys from list items
  • (D) Avoid using useEffect

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