A component needs to fetch data from an API only once when it's first rendered. Which hook/method can be used to achieve this in a functional component?
- componentDidMount()
- componentWillMount()
- useEffect() with an empty dependency array
- useFetchEffect()
To fetch data from an API only once when a functional component is first rendered, you should use the useEffect() hook with an empty dependency array []. This ensures that the effect runs only once, mimicking the behavior of componentDidMount() in class components.
When a child component is rendered using a Portal, it still inherits the ________ from its parent component.
- Context
- Props
- State
- Styles
When a child component is rendered using a Portal, it still inherits the Props from its parent component. This allows data to be passed from the parent to the child component even when the child is rendered in a different part of the DOM. While state, styles, and context are important in React, they are not inherited by default when using Portals.
In a scenario where you have frequent state updates in different parts of your app, which state management approach might be more performant than Redux?
- Angular's built-in state management
- Local component state
- MobX
- jQuery
In scenarios with frequent state updates, MobX is often considered more performant than Redux. MobX utilizes observables and reacts to changes at a granular level, which can lead to better performance in situations with high-frequency state updates. In contrast, Redux follows a unidirectional data flow, which can be less efficient in such cases.
When a component's output is not affected by a change in state or props, you can optimize its rendering with ______.
- Pure Components
- React.memo()
- useCallback()
- PureComponent()
When a component's output is not affected by a change in state or props, you can optimize its rendering with React.memo(). This higher-order component (HOC) prevents unnecessary re-renders of a component when its input props remain the same. The other options are related to optimization but not specifically for cases where props or state don't change.
When React encounters two elements of different types during the reconciliation process, it will ________ the old tree and build a new one from scratch.
- Append to the existing tree
- Ignore the elements and continue
- Unmount and replace
- Update the old tree
When React encounters two elements of different types during the reconciliation process, it will "Unmount and replace" the old tree and build a new one from scratch. This approach ensures that the new elements are created and inserted correctly in the virtual DOM and the actual DOM, maintaining consistency in the UI.
You're building an e-commerce platform and need to apply different styles based on the user's selected theme. Which React library would be most suitable to dynamically style components?
- Styled-components
- CSS modules
- SCSS (Sass)
- Inline CSS using the style attribute
Styled-components is a popular library for dynamically styling components in React. It allows you to define styles as components and dynamically switch styles based on user themes or other conditions. CSS modules are also an option but are less dynamic. SCSS is a preprocessor, and inline CSS using the style attribute is less suitable for managing complex styles across components.
When creating a generic component in React with TypeScript, how do you pass type arguments to the component?
- Type arguments are not needed for generic components in React with TypeScript.
- By specifying the type arguments in angle brackets when rendering the component.
- By using TypeScript's createGeneric function to pass type arguments.
- By defining type arguments in a separate configuration file.
When creating a generic component in React with TypeScript, you pass type arguments to the component by specifying the type arguments in angle brackets when rendering the component. This informs TypeScript of the specific types you want to use with the generic component. The other options do not follow the correct approach for passing type arguments to generic components in React.
How can you simulate a button click event in React Testing Library?
- Use the simulateButtonClick function.
- Call the fireEvent function with the click event.
- Import the ButtonSimulator component.
- Include an onClick prop in the button element.
In React Testing Library, you can simulate a button click event by calling the fireEvent function with the click event. This function is part of the testing library and allows you to interact with your components in testing scenarios. The other options are not correct. There is no simulateButtonClick function, and ButtonSimulator is not a standard component in React Testing Library. Including an onClick prop in the button element doesn't simulate a click event; it's used for defining the behavior when the button is clicked.
Prop drilling refers to the practice of passing ________ through multiple levels of components.
- Component props
- Context API values
- Redux actions
- Stateful data
Prop drilling is the process of passing component props through multiple levels of nested components to reach a deeply nested child component that needs access to those props. This can lead to maintenance challenges and make the code less maintainable.
In React Transition Group, the ________ component helps in managing a group of CSSTransition components.
- AnimateGroup
- CSSTransitionGroup
- ReactGroup
- TransitionGroup
In React Transition Group, the TransitionGroup component is used to manage a group of CSSTransition components. The TransitionGroup component helps control the mounting and unmounting of components with animation. It is a crucial part of creating smooth transitions in React applications using this library.
How can you coordinate multiple animations simultaneously using React Transition Group?
- Using the
component to manage multiple components. - By using React Hooks to manually control each animation.
- Employing the
class for synchronization. - Utilizing Redux to handle animation state.
To coordinate multiple animations simultaneously in React using React Transition Group, you can use the component. It manages a set of components, ensuring they start and end at the appropriate times. The other options do not represent typical methods for coordinating animations with React Transition Group.
Which library is commonly used for data visualization and charting in React applications?
- Axios
- D3.js
- Express.js
- React Router
D3.js is a widely used library for data visualization and charting in React applications. It provides powerful tools for creating interactive and dynamic data visualizations, making it a popular choice for developers who want to display data in a visually appealing and informative way within their React applications.