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
131. What is the primary way to style React components?
A. Inline styles
B. External CSS files
C. JavaScript libraries
D. Inline HTML attributes
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Answer: Inline styles
132. In React, how can you apply inline styles to components using JavaScript objects?
A. By using the style attribute
B. By using the class attribute
C. By using the id attribute
D. By using the src attribute
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Answer: By using the style attribute
133. Which CSS-in-JS library is commonly used for styling React components?
A. Styled Components
B. React Bootstrap
C. Material-UI
D. Redux-Saga
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Answer: Styled Components
134. In React, why is it beneficial to use a CSS-in-JS library like Styled Components?
A. To write traditional CSS styles
B. To externalize all styles to a CSS file
C. To reduce the size of the bundle
D. To improve performance
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Answer: To reduce the size of the bundle
135. What is the advantage of using external CSS files for styling React components?
A. Easy reusability and separation of concerns
B. Inline styles are more efficient
C. Inline styles have better browser support
D. Inline styles offer more features
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Answer: Easy reusability and separation of concerns
136. In React, how do you add CSS classes to components using JSX?
A. By using the class attribute
B. By using the styles attribute
C. By using the className attribute
D. By using the style attribute
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Answer: By using the className attribute
137. When using Styled Components in React, how are styles defined for a component?
A. As tagged template literals
B. As JSX attributes
C. As function expressions
D. As JSON objects
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Answer: As tagged template literals
138. What is a potential drawback of using inline styles in React components?
A. Limited support for dynamic styling
B. Increased separation of concerns
C. Slower rendering performance
D. Difficulty in applying global styles
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Answer: Limited support for dynamic styling
139. Which CSS preprocessor is often used in combination with React for enhanced styling capabilities?
A. Sass
B. HTML
C. JavaScript
D. TypeScript
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Answer: Sass
140. In React, how do you conditionally apply styles to components based on component state or props?
A. By using conditional statements
B. By using the style attribute
C. By using external CSS files
D. By using the class attribute
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Answer: By using conditional statements
