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.
Which React-Redux hook can be used to dispatch an action to the Redux store?
- useDispatch
- useStore
- useState
- useSelector
The useDispatch hook is used to dispatch actions to the Redux store in a React-Redux application. It provides a reference to the dispatch function, allowing you to trigger actions from your components. The other options are not used for dispatching actions.
To mock a resolved value of a Promise using Jest, you can use the method ________.
- mockResolvedValue
- resolveMock
- promiseValue
- mockPromise
In Jest, to mock a resolved value of a Promise, you can use the mockResolvedValue method. This allows you to specify the value that the Promise should resolve with in your test. The other options are not the correct methods for achieving this specific behavior with Promises in Jest.
How can the combination of Context API and Hooks provide state management solutions comparable to libraries like Redux?
- By allowing for centralized state management.
- By eliminating the need for any additional state management libraries.
- By integrating third-party state management tools.
- By providing advanced server-side rendering.
The combination of Context API and Hooks can provide state management solutions comparable to libraries like Redux by allowing for centralized state management. Context API provides the context to share state across components, while Hooks like useState and useReducer can manage that state effectively. This eliminates the need for additional state management libraries like Redux while maintaining similar functionality.
One popular method for ensuring state immutability in Redux is using the ________ utility functions.
- Immutable.js
- Lodash
- Reselect
- Spread Operator
The spread operator (often denoted as "..." in JavaScript) is a popular method for ensuring state immutability in Redux. It allows you to create shallow copies of objects or arrays, ensuring that changes to the state do not mutate the original state, which is crucial for maintaining the integrity of the Redux store.
In React, event handlers set on components are actually set on the ________ and not on the individual elements.
- component instances
- document root
- individual elements
- parent container
In React, event handlers set on components are actually set on the component instances themselves and not on the individual DOM elements. This allows React to efficiently manage and delegate events within its virtual DOM, making it a key aspect of React's event handling mechanism.
You are building a form in a functional component and need to keep track of form input values. Which hook would be most appropriate to manage the form state?
- useContext
- useEffect
- useMemo
- useState
To manage form input values in a functional component, the most appropriate hook is useState. useState allows you to create and update state variables, which can be used to track form input values as users interact with the form elements. While useEffect, useMemo, and useContext have their use cases, they are not designed for managing form state directly.
React Native's mechanism to "hot reload" and see changes instantly without a full app reload is called ________.
- Instant Refresh
- Quick Reload
- Rapid Refresh
- Swift Update
React Native's mechanism to "hot reload" and see changes instantly without a full app reload is called "Instant Refresh." It is a valuable feature in React Native development that accelerates the development process by allowing developers to view changes immediately. The other options do not accurately describe this specific React Native feature.
You are designing a quiz application where users can click on an option to choose their answer. To highlight the selected option and store the user's choice, you would use ________ to manage this local UI state.
- useState
- useRef
- useReducer
- useContext
To manage the local UI state in a quiz application where users can select answers, you would use the useState hook. useState allows you to create state variables that can hold the selected option and trigger UI updates when the user makes a choice. While useRef, useReducer, and useContext have their use cases, they are not the primary choice for managing local UI state in this scenario.