A HOC is a function that takes a component and returns a new component, often with ________.
- Additional state management capabilities.
- Enhanced props or behavior.
- Enhanced styling options.
- Improved performance characteristics.
A Higher Order Component (HOC) is a function in React that takes a component as input and returns a new component with enhanced props or behavior. HOCs are often used to share common functionality across multiple components, making code reuse and abstraction easier in React applications.
In a React application, if you want to offload computationally expensive tasks without blocking the UI thread, you'd typically use ________.
- JSX
- Promises
- Redux
- Web Workers
To offload computationally expensive tasks in a React application without blocking the UI thread, you'd typically use Web Workers. Web Workers are a feature in web browsers that allows you to run JavaScript code in a separate thread, ensuring that the main UI thread remains responsive. This is especially useful for tasks that require significant computational power.
The useReducer hook is especially useful when the next state depends on the ________ state.
- Current
- Global
- Initial
- Previous
The useReducer hook in React is particularly useful when the next state depends on the global state, often referred to as the previous state. It allows developers to manage state transitions and complex logic more effectively, making it a valuable tool in scenarios where state updates are interdependent.
In a large application where tracking state changes is becoming complex, which library could help manage state updates using a more concise and readable syntax, while ensuring immutability?
- Immer
- Lodash
- MobX
- Redux-Saga
In a large application with complex state changes, the library that can help manage state updates using a more concise and readable syntax while ensuring immutability is Immer. Immer simplifies state updates by allowing you to write code that appears mutable but actually produces immutable updates. It's particularly useful when dealing with deeply nested state structures.
In React Router, the ________ prop in the Route component allows passing props directly to the rendered component.
- "component"
- "render"
- "children"
- "props"
In React Router, the "render" prop in the Route component allows passing props directly to the rendered component. This is particularly useful when you need to pass additional props or perform logic before rendering the component associated with a specific route. The other options ("component," "children," and "props") are not used for this specific purpose.
In a web application, there's a requirement to render tooltips directly under the body tag to ensure they always appear on top, but the tooltip logic is nested deep within other components. How can this be achieved in React?
- React.forwardRef()
- React.lazy()
- React.memo()
- ReactDOM.createPortal()
To render tooltips directly under the body tag and ensure they appear on top, you can use ReactDOM.createPortal(). This function allows you to render a React component at a different DOM location, ensuring it's not affected by the hierarchy of nested components. This is commonly used to create overlays like tooltips and modals.
When a component extends ________, it automatically implements shouldComponentUpdate with a shallow comparison of state and props.
- Component
- PureComponent
- React.Component
- React.PureComponent
When a component extends React.PureComponent, it automatically implements shouldComponentUpdate with a shallow comparison of state and props. This shallow comparison helps in optimizing rendering by preventing unnecessary updates when there are no actual changes to state or props.
For platform-specific code in React Native, you can use filename extensions like .ios.js and ________.
- .android.js
- .native.js
- .platform.js
- .react.js
In React Native, for platform-specific code, you can use filename extensions like .ios.js for iOS-specific code and .android.js for Android-specific code. These filename extensions allow you to write platform-specific logic in separate files, making it easier to maintain and customize your app's behavior for different platforms. .platform.js, .native.js, and .react.js are not standard extensions for platform-specific code in React Native.
Your team is experiencing issues with components re-rendering unnecessarily. What immutable state handling technique could help mitigate unnecessary re-renders?
- Caching
- Memoization
- Object.freeze()
- Prototype-based cloning
Memoization is an immutable state handling technique that can help mitigate unnecessary component re-renders. It involves caching the results of expensive function calls based on their input parameters. When the same input parameters are encountered again, the cached result is returned, reducing the need for re-computation and re-rendering.
What does the getStaticProps function in Next.js do?
- It creates a static HTML page without data fetching.
- It fetches data at build time.
- It fetches data at server-side and client-side.
- It retrieves dynamic data at runtime.
The getStaticProps function in Next.js is used to fetch data at build time. It allows you to pre-render pages with data before they are served to the client. This approach improves performance as the data is fetched and generated during the build process, reducing the need for runtime data fetching. It's a key feature for static site generation (SSG) in Next.js.
You've been tasked to ensure the React Native app performs smoothly and feels native. Which of the following strategies would be effective in improving the app's performance?
- Implement code splitting to load only the necessary components on-demand.
- Increase the size of the app bundle to include all possible features upfront.
- Use a JavaScript framework other than React Native to build the app.
- Use a single-threaded architecture to simplify the app's logic.
To improve the performance and responsiveness of a React Native app, implementing code splitting is an effective strategy. This allows you to load only the necessary components when they are needed, reducing the initial load time and improving user experience. Using a single-threaded architecture can lead to performance bottlenecks. Increasing the app bundle size can result in longer load times and negatively impact performance. Using a different JavaScript framework would require rewriting the app and is not a strategy for improving the performance of an existing React Native app.
Why would you use React Portals?
- To control CSS styles globally across a React application.
- To create modals, tooltips, and other UI elements that need to "float" above their parent components.
- To manage state and data fetching in a React application.
- To optimize rendering performance for large lists and grids.
React Portals are used when you need to render UI elements like modals, tooltips, or popovers that should visually "float" above their parent components. Portals enable you to render content outside the parent DOM hierarchy while maintaining proper parent-child relationships in terms of events. They are not primarily used for rendering performance optimization, state management, or global CSS styling.