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
11. What are React components primarily used for?
A. Managing server-side data
B. Defining the structure of web pages
C. Writing server-side scripts
D. Running unit tests
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Answer: Defining the structure of web pages
12. In React, what is a component?
A. A server-side script
B. A functional unit of user interface
C. A database schema
D. A CSS stylesheet
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Answer: A functional unit of user interface
13. Which of the following is true about React components?
A. They cannot be reused
B. They are always stateful
C. They can be nested within other components
D. They don't accept props
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Answer: They can be nested within other components
14. What is the purpose of the render method in a React component?
A. To define component styles
B. To handle component events
C. To render the component's UI
D. To manage component state
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Answer: To render the component's UI
15. How can you pass data from a parent component to a child component in React?
A. By using the return statement
B. By modifying the child component's state
C. By using props
D. By using Redux
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Answer: By using props
16. What is the key benefit of using functional components in React?
A. They can have their own state
B. They have better performance than class components
C. They support lifecycle methods
D. They can't be reused
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Answer: They have better performance than class components
17. Which React hook is used for managing state in functional components?
A. useState
B. renderState
C. componentDidUpdate
D. setState
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Answer: useState
18. What does the term "props" stand for in React?
A. Properties
B. Proponents
C. Proprietary
D. Proximate
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Answer: Properties
19. In React, what is the purpose of the constructor method in a class component?
A. To create a new component instance
B. To initialize component state
C. To define component styles
D. To render the component's UI
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Answer: To initialize component state
20. What is the primary difference between class components and functional components in React?
A. Class components use lifecycle methods
B. Functional components use hooks
C. Class components have better performance
D. Functional components cannot accept props
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Answer: Functional components use hooks
