Which hook allows you to access the previous state or props without triggering a re-render?
- useEffect
- useMemo
- usePrevious
- useState
The usePrevious custom hook allows you to access the previous state or props without triggering a re-render. It's not a built-in hook in React but is often implemented as a custom hook. The useEffect hook can be used to achieve similar functionality, but it can indirectly trigger re-renders, making usePrevious a more direct choice for this specific use case.
During the development phase, you notice that one of your components occasionally throws an error during rendering. However, the error doesn't seem to be caught by any of your error boundaries. What could be a potential reason?
- The error is thrown asynchronously, making it difficult for error boundaries to catch it.
- The component is using a custom error boundary that doesn't have the necessary logic to catch the specific error being thrown.
- The error is originating in a child component of the one you've wrapped with an error boundary, causing it to bypass the boundary.
- The error is thrown during the initial render of the component, before the error boundary can be set up.
A potential reason why the error isn't caught by error boundaries is that it originates in a child component of the one wrapped with an error boundary. Error boundaries only catch errors in the component tree below them, not in their parent components. The other options are less likely explanations. Asynchronous errors (Option 1) can still be caught, custom error boundaries (Option 2) can be configured to catch specific errors, and error boundaries can be set up before rendering (Option 4).
In which situations might you consider using React Fragments?
- When you need to create reusable component logic.
- When you want to group multiple elements without a div.
- When you want to manage state in functional components.
- When you need to fetch data from an external API.
React Fragments are useful when you want to group multiple elements without introducing an extra div wrapper. This is beneficial for cleaner and more semantic JSX code. The other options do not directly relate to the use of React Fragments.
What would be the common mistake of function being called every time the component renders?
- Declaring the function inside the component's render method
- Not using React.lazy() to lazy-load the component
- Not using React.memo() to memoize the component
- Not using the shouldComponentUpdate() method to prevent unnecessary re-renders
A common mistake that can cause a function to be called every time the component renders is declaring the function inside the component's render method. This can cause the function to be recreated every time the component renders, even if the function's dependencies have not changed. To avoid this problem, functions should be declared outside the render method, or in a separate file if they are reused across multiple components.
Should I keep all component's state in Redux store?
- Yes, it is recommended to keep all component state in the Redux store
- No, it is recommended to keep only the necessary state in the Redux store
It is not recommended to keep all component state in the Redux store. While Redux is useful for managing state in large applications, it can also add unnecessary complexity and boilerplate code to small applications. It is recommended to keep only the necessary state in the Redux store and use component state for simpler state management needs.
What are props in React?
- A component's children
- A component's internal data
- A component's methods
- A component's properties
In React, props (short for "properties") are a component's input data that are passed down from a parent component. Props are read-only and cannot be changed by the child component. Props are used to customize the behavior and appearance of a component.
What are the major features of React?
- All the options
- Component reusability
- Server-side rendering
- Virtual DOM
React has several major features, including a virtual DOM, server-side rendering, and component reusability. The virtual DOM helps improve performance by minimizing the number of updates needed to the actual DOM. Server-side rendering allows React to render components on the server before sending them to the client, improving performance and SEO. Component reusability allows developers to create reusable UI components using JavaScript. One-way data binding is not a major feature of React.
Do I need to rewrite all my class components with hooks?
- Yes, it is recommended to use hooks over class components
- No, you can continue to use class components if they are working for your project
- It depends on the project requirements
React Hooks were introduced to provide an alternative way of managing state and lifecycle methods in functional components. However, class components are still fully supported in React, and you can continue to use them if they are working for your project.
How to add Google Analytics for react-router?
- Use the "google-analytics" library with the "react-router-analytics" package
- Use the "react-analytics" library with the "router-react-analytics" package
- Use the "react-ga" library with the "react-router-ga" package
- Use the "react-router-ga" library with the "google-analytics-react" package
In React, you can add Google Analytics for React Router by using the "react-ga" library with the "react-router-ga" package. This will allow you to track pageviews and events for your React Router pages in Google Analytics, and can be configured in the "index.js" or "App.js" files.
What are controlled components?
- Components that are managed by React and cannot be updated directly
- Components that are updated using refs
- Components that are updated using the setState() method
- Components that store their own state
Controlled components are components that store their state in a parent component and are updated using the setState() method. The parent component passes down the component's state as props and also passes down a function to update the state when needed. This approach allows for more control over the component's behavior and simplifies debugging.