250+ React Js MCQ With Online Practice Test

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.

Practice Test

121. In React, what is the primary purpose of rendering lists of items using the map method?

Answer: To display a collection of elements

122. When rendering a list of items in React, what is the purpose of using a unique "key" prop for each item?

Answer: To identify each item in the list

123. Which of the following is true about keys in React lists?

Answer: Keys can be duplicate values

124. What happens if you don't provide a "key" prop when rendering a list of items in React?

Answer: It causes an error during rendering

125. In React, which type of data structure is commonly used for storing lists of items before rendering?

Answer: Arrays

126. What is the purpose of the map method when rendering lists in React?

Answer: To transform the list items

127. In React, what is the recommended approach for rendering a list of elements conditionally?

Answer: By using the map method

128. When rendering a list of React components, what should the "key" prop be set to?

Answer: A unique identifier for each component

129. In React, what is the purpose of the index parameter in the map method when rendering a list of items?

Answer: To uniquely identify each item

130. When working with lists in React, which operation is more efficient: adding an item to the beginning or end?

Answer: Adding an item to the end of the list
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React Js Multiple Choice Questions React Js MCQ React Js Interview Questions With Answers