JSX gets compiled into ________ by tools like Babel.
- CSS
- HTML
- JavaScript
- XML
JSX (JavaScript XML) gets compiled into JavaScript by tools like Babel. It's important to understand that JSX is a syntax extension for JavaScript, allowing developers to write HTML-like code within their JavaScript files. This JSX code is then transformed into standard JavaScript code that browsers can understand.
The ________ method allows you to manually determine if a component should re-render in response to a change in props or state.
- componentDidMount
- render
- setState
- shouldComponentUpdate
The shouldComponentUpdate method in React allows developers to manually determine whether a component should re-render in response to changes in props or state. This method returns a Boolean value - true if the component should re-render and false if it should not. It's a critical method for optimizing React components to avoid unnecessary rendering.
While rendering a list of items, you observed that adding a new item to the top causes a re-render of the entire list. What might be the likely cause of this issue?
- Applying shouldComponentUpdate() to the list components
- Incorrect use of React fragments
- Missing unique keys in the list elements
- Using React.memo() for list components
When adding a new item to a list in React, it's essential to provide unique keys to each list item using the "key" prop. If unique keys are missing or incorrectly assigned, React cannot efficiently identify which items have changed, and it may re-render the entire list. Using React.memo() can help optimize functional components, but it's unrelated to this specific issue. React fragments and shouldComponentUpdate() do not directly address the key issue.
In MobX, which feature allows you to track changes to your state?
- Actions.
- Decorators.
- Observables.
- Promises.
In MobX, you can track changes to your state using "Observables." Observables are the fundamental building blocks that enable you to automatically detect and track changes in your application state. Actions are used to modify state, decorators are used for defining computed properties, and Promises are typically used for handling asynchronous operations but do not directly track state changes.
A colleague is using a type any for all props in a React component. What potential issue might arise from this practice in TypeScript?
- Enhanced Performance
- Improved Code Readability
- Simplified Debugging
- Type Safety Issues
Using type any for all props in a React component can lead to potential Type Safety Issues in TypeScript. This means that TypeScript won't be able to provide compile-time checks and assistance for type-related errors, increasing the risk of runtime errors. While it may make code more flexible, it sacrifices type safety, which is a significant disadvantage in TypeScript.
What is JSX in React?
- A JavaScript XML-like syntax
- A database query language
- A style sheet language
- JavaScript eXtension
JSX stands for JavaScript XML. It allows developers to write HTML-like code within their JavaScript code. React then converts these JSX expressions into actual JavaScript objects before rendering them in the DOM.
What is the primary purpose of the Context API in React?
- Handling HTTP requests.
- Managing global application state.
- Rendering UI components.
- Styling React components.
The primary purpose of the Context API in React is to manage global application state. It allows you to share data, such as user authentication status or theme preferences, across components without prop-drilling. While rendering UI components is a core function of React, the Context API specifically addresses the challenge of managing shared state.
What is the main purpose of Google Maps integration in a React application?
- Displaying real-time weather information.
- Enabling social media sharing.
- Enhancing the user interface with interactive maps.
- Managing state in React components.
Google Maps integration in a React application is primarily used to enhance the user interface by adding interactive maps. Developers can integrate Google Maps to display locations, directions, or any spatial data, making their applications more user-friendly and engaging. It's a common choice for applications that require geolocation features.
What is the purpose of the setState method in React class components?
- To define a new component in React.
- To update and re-render the component with new data.
- To handle HTTP requests in React applications.
- To declare a function in a React component.
The setState method in React class components is used to update and re-render the component with new data. It's essential for managing the component's internal state and triggering re-renders when that state changes. Options 1, 3, and 4 do not accurately describe the purpose of setState.
What is the primary purpose of the React hook useState?
- To manage and update component state.
- To create reusable components.
- To perform API requests.
- To handle router navigation.
The primary purpose of the React hook useState is to manage and update component state. It allows functional components to have stateful behavior, which is crucial for handling dynamic data and user interactions. The other options (create reusable components, perform API requests, and handle router navigation) are not the primary purpose of useState.