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.
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Practice Test
81. What is the primary purpose of React Hooks?
A. To fetch data from APIs
B. To manage component state
C. To render components
D. To create functional components
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Answer: To manage component state
82. In a functional component, how do you declare and use a state variable using the useState Hook?
A. const [state, setState] = useState(initialValue)
B. const state = useState(initialValue)
C. const [state] = useState(initialValue)
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Answer: const [state, setState] = useState(initialValue)
83. Which built-in Hook is used for performing side effects in a functional component?
A. useEffect
B. useState
C. useRender
D. useLifecycle
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Answer: useEffect
84. What is the purpose of the useEffect Hook in React?
A. To manage component state changes
B. To handle form submissions
C. To create custom Hooks
D. To define new routes
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Answer: To manage component state changes
85. In a functional component, how do you conditionally apply the useEffect Hook?
A. It is always applied
B. By using an if statement
C. By using the useEffect Hook itself
D. It cannot be applied conditionally
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Answer: By using an if statement
86. Which Hook allows you to perform data fetching and side effects in response to component updates?
A. useState
B. useEffect
C. useFetch
D. useData
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Answer: useEffect
87. In React, how do you create a custom Hook for reusing stateful logic across different components?
A. By defining a function that uses existing Hooks
B. By using the useState Hook directly
C. By extending the Component class
D. By using class components
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Answer: By defining a function that uses existing Hooks
88. What is the primary benefit of using Hooks in React?
A. Simplicity and reusability
B. Enhanced performance
C. Improved security
D. Server-side rendering
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Answer: Simplicity and reusability
89. In a functional component, how do you update the state variable declared with the useState Hook?
A. By calling the state variable directly
B. By using the setState function
C. By calling the useState function
D. By invoking the useEffect Hook
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Answer: By using the setState function
90. What is the React Hook used for subscribing to context within a functional component?
A. useContext
B. useReducer
C. useContextProvider
D. useSubscriber
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Answer: useContext
