In MobX, a piece of state that can be observed for changes is marked as ________.
- Constructor
- Immutable
- Mutable
- Observable
In MobX, a piece of state that can be observed for changes is marked as an "observable." Observables are used to track changes to state and automatically update any components that depend on them. This is a key concept in MobX, enabling reactive and efficient updates to the user interface based on state changes.
In a React application that uses Web Workers, a user reports that a specific feature is causing the app to freeze. What might be a potential cause?
- The Web Worker script is executing a time-consuming task.
- The React components are not using Redux for state management.
- The browser does not support Web Workers.
- The user's network connection is slow.
If a React application using Web Workers freezes, a potential cause could be that the Web Worker script is executing a time-consuming task, which may be blocking the main thread. Web Workers can only offload tasks if properly managed, and inefficiently designed tasks can still impact performance. The other options are less likely to be the primary cause of app freezing in this scenario.
If an error boundary fails while rendering the error message, the error will propagate to the nearest ________.
- ErrorBoundaryBoundary
- ErrorBoundaryFallback
- React Router
- Redux store
If an error boundary fails to render the error message itself (for example, if it encounters an error during rendering), React will propagate the error to the nearest error boundary higher in the component hierarchy. The ErrorBoundaryBoundary is not a standard term in React; it's used here to emphasize the concept.
You are refactoring a React application and notice that two components, one with a and another with a , are conditionally rendered at the same location based on some state. What would React do during reconciliation when the state changes between these two component types?
- Prioritize rendering the
over the
- Render both components simultaneously
- Replace the existing component with the new one
- Throw an error because of invalid JSX syntax
When conditionally rendering two components at the same location in React, React will replace the existing component with the new one when the state changes. This is because React reconciles the virtual DOM, and when the state changes, it updates the DOM to match the new JSX structure. It doesn't render both components simultaneously, and it doesn't throw an error as long as the JSX syntax is valid.
You're tasked with optimizing a React application to make it available offline. Which technology would you primarily consider implementing to achieve this?
- GraphQL
- RESTful APIs
- Service Workers
- WebSockets
To make a React application available offline, you would primarily consider implementing Service Workers. Service Workers enable the caching and offline availability of web resources, allowing your app to work even when the network connection is lost. WebSockets, RESTful APIs, and GraphQL are relevant technologies but serve different purposes and do not directly enable offline functionality.
You're building a dashboard that frequently updates with real-time data. Which feature of React would best help minimize unnecessary DOM updates?
- PureComponent
- React.memo()
- shouldComponentUpdate()
- useMemo()
To minimize unnecessary DOM updates in React, you should use the useMemo() hook. This hook allows you to memoize the result of an expensive computation so that it's only recomputed when its dependencies change. This is particularly useful when dealing with real-time data that frequently updates to avoid unnecessary re-renders of components.
You're building a real-time dashboard in React that displays stock market data. The data updates every second, but you don't want to overwhelm the user. What strategy can you implement to balance real-time updates and user experience?
- Implement server-side throttling to control data updates.
- Use a web worker to offload data processing and updates.
- Increase the update frequency for the most critical data.
- Display all updates as soon as they arrive to ensure real-time accuracy.
In this scenario, implementing server-side throttling is a suitable strategy to balance real-time updates and user experience. Throttling allows you to control the rate of data updates sent to the client, preventing the user from being overwhelmed with frequent updates. It ensures a smoother user experience while still providing real-time data. The other options may not effectively address the issue and could worsen the user experience.
In Webpack, the comment syntax /* webpackChunkName: "myChunkName" */ is used to ________.
- Add a license header
- Configure the output
- Create a code split
- Define an alias
In Webpack, the comment syntax /* webpackChunkName: "myChunkName" */ is used to create a code split. When you use this syntax in your code, Webpack will create a separate JavaScript bundle (chunk) with the specified name, allowing for efficient code splitting and lazy loading of modules, which can improve performance.
When you want to exclude certain properties from a type, TypeScript provides the ________ utility type.
- Exclude
- Omit
- Partial
- Pick
TypeScript provides the Omit utility type when you want to exclude certain properties from a type. It allows you to create a new type that includes all properties from the original type except the specified ones. This is helpful for creating more specific types based on existing ones.
You're refactoring a class component that contains several lifecycle methods into a functional component. What feature of React would you use to handle side effects in the functional component?
- useState and useEffect
- render method
- componentDidMount and componentDidUpdate
- constructor and componentWillUnmount
In a functional component, you can handle side effects using useState to manage state and useEffect to perform side effects. These hooks replace the lifecycle methods found in class components, making it more concise and easier to manage side effects. componentDidMount and componentDidUpdate are lifecycle methods used in class components, not in functional components. The other options are also not the correct way to handle side effects in functional components.
- Prioritize rendering the
over the
- Render both components simultaneously
- Replace the existing component with the new one
- Throw an error because of invalid JSX syntax
When conditionally rendering two components at the same location in React, React will replace the existing component with the new one when the state changes. This is because React reconciles the virtual DOM, and when the state changes, it updates the DOM to match the new JSX structure. It doesn't render both components simultaneously, and it doesn't throw an error as long as the JSX syntax is valid.
You're tasked with optimizing a React application to make it available offline. Which technology would you primarily consider implementing to achieve this?
- GraphQL
- RESTful APIs
- Service Workers
- WebSockets
To make a React application available offline, you would primarily consider implementing Service Workers. Service Workers enable the caching and offline availability of web resources, allowing your app to work even when the network connection is lost. WebSockets, RESTful APIs, and GraphQL are relevant technologies but serve different purposes and do not directly enable offline functionality.
You're building a dashboard that frequently updates with real-time data. Which feature of React would best help minimize unnecessary DOM updates?
- PureComponent
- React.memo()
- shouldComponentUpdate()
- useMemo()
To minimize unnecessary DOM updates in React, you should use the useMemo() hook. This hook allows you to memoize the result of an expensive computation so that it's only recomputed when its dependencies change. This is particularly useful when dealing with real-time data that frequently updates to avoid unnecessary re-renders of components.
You're building a real-time dashboard in React that displays stock market data. The data updates every second, but you don't want to overwhelm the user. What strategy can you implement to balance real-time updates and user experience?
- Implement server-side throttling to control data updates.
- Use a web worker to offload data processing and updates.
- Increase the update frequency for the most critical data.
- Display all updates as soon as they arrive to ensure real-time accuracy.
In this scenario, implementing server-side throttling is a suitable strategy to balance real-time updates and user experience. Throttling allows you to control the rate of data updates sent to the client, preventing the user from being overwhelmed with frequent updates. It ensures a smoother user experience while still providing real-time data. The other options may not effectively address the issue and could worsen the user experience.
In Webpack, the comment syntax /* webpackChunkName: "myChunkName" */ is used to ________.
- Add a license header
- Configure the output
- Create a code split
- Define an alias
In Webpack, the comment syntax /* webpackChunkName: "myChunkName" */ is used to create a code split. When you use this syntax in your code, Webpack will create a separate JavaScript bundle (chunk) with the specified name, allowing for efficient code splitting and lazy loading of modules, which can improve performance.
When you want to exclude certain properties from a type, TypeScript provides the ________ utility type.
- Exclude
- Omit
- Partial
- Pick
TypeScript provides the Omit utility type when you want to exclude certain properties from a type. It allows you to create a new type that includes all properties from the original type except the specified ones. This is helpful for creating more specific types based on existing ones.
You're refactoring a class component that contains several lifecycle methods into a functional component. What feature of React would you use to handle side effects in the functional component?
- useState and useEffect
- render method
- componentDidMount and componentDidUpdate
- constructor and componentWillUnmount
In a functional component, you can handle side effects using useState to manage state and useEffect to perform side effects. These hooks replace the lifecycle methods found in class components, making it more concise and easier to manage side effects. componentDidMount and componentDidUpdate are lifecycle methods used in class components, not in functional components. The other options are also not the correct way to handle side effects in functional components.