250+ React Js MCQ With Online Practice Test

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React.js, often simply called React, is a highly popular JavaScript library for building user interfaces. Developed and maintained by Facebook, React is renowned for its component-based architecture and the ability to efficiently update and render components when data changes. It is a foundational tool for developing modern web and mobile applications, allowing developers to create dynamic and interactive user interfaces with ease. React's vast ecosystem, including tools like React Native for mobile app development, makes it a top choice for frontend development and a key player in the world of web technologies.

81. What is the primary purpose of React Hooks?

Answer: To manage component state

82. In a functional component, how do you declare and use a state variable using the useState Hook?

Answer: const [state, setState] = useState(initialValue)

83. Which built-in Hook is used for performing side effects in a functional component?

Answer: useEffect

84. What is the purpose of the useEffect Hook in React?

Answer: To manage component state changes

85. In a functional component, how do you conditionally apply the useEffect Hook?

Answer: By using an if statement

86. Which Hook allows you to perform data fetching and side effects in response to component updates?

Answer: useEffect

87. In React, how do you create a custom Hook for reusing stateful logic across different components?

Answer: By defining a function that uses existing Hooks

88. What is the primary benefit of using Hooks in React?

Answer: Simplicity and reusability

89. In a functional component, how do you update the state variable declared with the useState Hook?

Answer: By using the setState function

90. What is the React Hook used for subscribing to context within a functional component?

Answer: useContext
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React Js Multiple Choice Questions React Js MCQ React Js Interview Questions With Answers