In class components, the method used to update the state is ________.
- this.updateState
- setState()
- changeState()
- modifyState()
In class components in React, the method used to update the state is setState(). This method is used to update the state object, and React then re-renders the component to reflect the new state. The other options are not valid methods for updating state in class components.
When using libraries like Immer, what is the term used for the function you provide that describes the state changes?
- modifyState
- mutator
- reducer
- transform
When using libraries like Immer, you typically provide a function known as a "reducer" that describes the state changes. This function takes the current state and a draft state, and you specify the changes to be made. The reducer function is a fundamental concept in libraries like Immer and Redux for managing state updates in an immutable fashion.
A component that is used to transform another component by adding additional logic or properties is called a ________.
- HOC (Higher Order Component)
- Container Component
- Stateless Component
- Functional Component
A Higher Order Component (HOC) is used to wrap or enhance other components by adding additional logic or properties. HOCs are a common pattern in React for code reuse and logic sharing. While the other options are types of components used in React, they do not specifically describe the component that adds logic or properties to another.
To reduce the need for prop drilling, one can use HOCs in combination with ________ to provide data directly to the components that need it.
- Context
- Local component state
- Props
- Redux
Higher-Order Components (HOCs) can be combined with Context to provide data directly to components that need it, reducing the need for prop drilling (passing data through multiple intermediate components). Context provides a way to share data across the component tree without explicitly passing props at each level.
Which library is specifically designed for testing React components?
- Axios
- React Query
- React Testing Library
- Redux
React Testing Library is specifically designed for testing React components. It offers a set of utilities for interacting with and asserting the behavior of React components in a way that mimics how users interact with a UI. It promotes best practices for testing React applications and makes it easier to write effective tests for your components.
To run native modules in React Native, developers often use a bridge called ________.
- React Bridge
- Native Link
- JavaScript Bridge
- Module Connector
In React Native, developers often use a bridge called "JavaScript Bridge" to run native modules. This bridge allows communication between JavaScript code and native code, enabling the use of native modules in React Native applications. The other options are not commonly used terms for this concept.
In React, when a parent component renders, it will cause all its ________ components to potentially re-render as well.
- ancestor
- child
- descendant
- sibling
In React, when a parent component renders, it will cause all its child components to potentially re-render as well. This is because React re-renders the child components to ensure that they reflect any changes in the parent's state or props.
You're building a media application that should display high-resolution images. To improve user experience on slower networks, you decide to implement a feature that shows a low-res image first and then replaces it with the high-res image when it's loaded. Which React feature can help you achieve this?
- Lazy loading images with the lazy attribute
- Using react-loadable library
- Using React Suspense and React.lazy()
- Using React.Suspense and React.lazy()
To achieve the described behavior of loading low-res images first and replacing them with high-res images when loaded, you can use React's Suspense and React.lazy() along with the fallback attribute. This allows you to asynchronously load components, such as images, and show a loading fallback while waiting for the high-res image to load. The other options may be used in different contexts but do not directly address this use case.
To optimize large lists in React, you can use a technique called ______ rendering.
- Eager
- Incremental
- Lazy
- Virtual
To optimize large lists in React, you can use a technique called "Incremental" rendering. This approach renders only the visible items in a list, improving performance when dealing with extensive lists. It's a key strategy to enhance user experience in React applications, especially when handling large datasets.
You've noticed that every time a parent component's state changes, a child component re-renders even though its props remain unchanged. How might you optimize the child component to prevent unnecessary re-renders?
- Use React.memo
- Use componentDidUpdate
- Use shouldComponentUpdate
- Use useEffect
You can optimize the child component by using React.memo. This higher-order component (HOC) can wrap your child component, preventing it from re-rendering when its props remain unchanged. componentDidUpdate and useEffect are used for side effects and don't address the issue of unnecessary re-renders. While shouldComponentUpdate can be used in class components, React.memo is the recommended way in functional components.