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.
Show All Answers
Practice Test
121. In React, what is the primary purpose of rendering lists of items using the map method?
A. To create new components
B. To display a collection of elements
C. To apply styles to elements
D. To handle user input
Show Answer
Report This Question
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?
A. To style the list items
B. To identify each item in the list
C. To determine the list's length
D. To hide items in the list
Show Answer
Report This Question
Answer: To identify each item in the list
123. Which of the following is true about keys in React lists?
A. Keys are optional
B. Keys can be duplicate values
C. Keys are used for styling purposes
D. Keys are automatically generated
Show Answer
Report This Question
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?
A. It results in a warning but doesn't affect rendering
B. It causes an error during rendering
C. It doesn't affect the rendering
D. It creates a new key automatically
Show Answer
Report This Question
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?
A. Arrays
B. Objects
C. Strings
D. Numbers
Show Answer
Report This Question
Answer: Arrays
126. What is the purpose of the map method when rendering lists in React?
A. To transform the list items
B. To remove duplicate items from the list
C. To add new items to the list
D. To sort the list items
Show Answer
Report This Question
Answer: To transform the list items
127. In React, what is the recommended approach for rendering a list of elements conditionally?
A. By using the if-else statement
B. By using the map method
C. By using the switch statement
D. By using the for loop
Show Answer
Report This Question
Answer: By using the map method
128. When rendering a list of React components, what should the "key" prop be set to?
A. The component's index in the list
B. A unique identifier for each component
C. The component's type
D. The component's name
Show Answer
Report This Question
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?
A. To set the item's content
B. To access the previous item in the list
C. To uniquely identify each item
D. To add styling to the item
Show Answer
Report This Question
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?
A. Adding an item to the end of the list
B. Adding an item to the beginning of the list
C. Both operations have the same efficiency
D. It depends on the list size
Show Answer
Report This Question
Answer: Adding an item to the end of the list
