To store the previous state or props in functional components, you can use the ________ hook.

  • useEffect
  • useMemo
  • useRef
  • useState
To store the previous state or props in functional components, you can use the "useRef" hook. The useRef hook allows you to create mutable references to DOM elements and can be used to store previous values. While the other hooks (useState, useEffect, useMemo) are essential in functional components, they serve different purposes.

When animating route transitions in a React application, which component from 'react-router-dom' is commonly used to manage the different routes?

  • BrowserRouter
  • RouteTransition
  • Link
  • Route
When animating route transitions in a React application, the commonly used component from 'react-router-dom' to manage the different routes is the 'Route' component. The 'Route' component allows you to define which component should be rendered for a specific route, making it essential for navigation and route handling in React applications. The other options are not typically used for managing routes.

Overusing React.memo can lead to increased memory usage due to ________.

  • Frequent re-renders
  • Memory leaks
  • Slow performance
  • Undefined errors
Overusing React.memo can lead to increased memory usage due to frequent re-renders. React.memo is a memoization function in React used to optimize functional components by preventing unnecessary re-renders. However, if it's applied excessively, it can cause more re-renders than needed, which increases memory usage.

When two components have different types during reconciliation, how does React handle their child components?

  • React ignores the child components in this case.
  • React throws an error since component types must match.
  • React unmounts the old child components and replaces them with the new ones.
  • React updates the child components to match the new types.
When two components have different types during reconciliation, React unmounts the old child components and replaces them with the new ones. React prioritizes preserving the user interface's integrity and behavior by ensuring that the new component type is rendered correctly. This behavior is crucial for maintaining consistency when components change types.

Which hook allows functional components to consume context values?

  • useConsumer()
  • useContext()
  • useProvider()
  • useValue()
To allow functional components to consume context values in React, you use the useContext() hook. useContext() is a hook provided by React that enables functional components to access the data provided by a Context Provider. It simplifies the process of consuming context values and eliminates the need for a Context Consumer component, making it more convenient for functional components to access context data.

What is the main goal of the reconciliation process in React?

  • To compare virtual and real DOM.
  • To ensure the UI matches the desired state.
  • To optimize server-side rendering.
  • To update the real DOM directly.
The primary goal of the reconciliation process in React is to ensure that the user interface (UI) matches the desired state of the application. React accomplishes this by efficiently updating the virtual DOM and then applying only the necessary changes to the real DOM, resulting in a performant and responsive user experience. It is not about optimizing server-side rendering or directly updating the real DOM.

What is the primary challenge in integrating third-party real-time data in React applications?

  • Dealing with cross-origin requests.
  • Ensuring that the data updates are displayed in real-time.
  • Handling the data synchronization between different components.
  • Managing API rate limits.
The primary challenge in integrating third-party real-time data in React applications is handling data synchronization between different components. React's component-based architecture can make it complex to manage real-time data updates across components. While ensuring data updates are displayed in real-time is essential, it's not the primary challenge but a desired outcome of effective synchronization.

What is the primary benefit of lazy loading components in a React application?

  • Faster initial page load times.
  • Better code organization.
  • Enhanced code security.
  • Smaller bundle sizes.
The primary benefit of lazy loading components in a React application is faster initial page load times. Lazy loading allows you to load components only when they are needed, reducing the initial payload and improving the application's performance. While other options may have their advantages, faster initial page load times are the primary reason for using lazy loading.

When profiling a React application using React DevTools, what color indicates a component that has re-rendered?

  • Blue
  • Green
  • Red
  • Yellow
When profiling a React application using React DevTools, a component that has re-rendered is indicated by the color Red. This visual cue helps developers identify components that are re-rendering, which can be useful for optimizing performance by reducing unnecessary renders. The other colors are not typically associated with indicating re-renders in React DevTools.

When using Render Props, what is the typical method of passing data back to the parent component?

  • Callback function
  • Redux
  • Context API
  • Component state management (e.g., useState)
When using Render Props, the typical method of passing data back to the parent component is through a callback function. The child component that receives the Render Prop invokes this callback function with the data that needs to be passed to the parent component. This callback mechanism facilitates communication between the parent and child components, allowing data to flow from child to parent. The other options are not the typical way to pass data back in this context.