You are building a feature where you have to compare the current state and the next state of a component to decide whether it should re-render. How can Immutable.js assist in this comparison?
- Immutable.js allows you to directly modify the component's state without re-rendering.
- Immutable.js is not suitable for this purpose.
- Immutable.js provides a built-in function called shouldComponentUpdate that automatically handles state comparison.
- You must use a third-party library for this comparison.
Immutable.js provides a built-in function called shouldComponentUpdate that allows you to easily compare the current state with the next state to determine whether a component should re-render. This function helps optimize rendering performance by avoiding unnecessary re-renders when the state has not changed.
For improved performance in React Native, what can you use to run computationally heavy operations off the main UI thread?
- JavaScript timers (setTimeout and setInterval).
- Promises and async/await functions.
- Redux for managing state asynchronously.
- Web Workers and the "react-native-webview" library.
To enhance performance in React Native and prevent the main UI thread from becoming unresponsive during computationally heavy tasks, you can use Web Workers and the "react-native-webview" library. Web Workers allow you to run JavaScript code in a separate background thread, keeping the UI responsive. "react-native-webview" provides a WebView component with Web Worker support, making it a suitable choice for offloading heavy computations. JavaScript timers, Promises, and Redux are not primarily designed for offloading heavy computations.
In MobX, what is the best practice for modifying observable state?
- Directly modifying the state without any restrictions.
- Modifying the state only within actions or reactions.
- Only allowing modifications in the constructor of the class.
- Using third-party libraries for state management.
The best practice in MobX is to modify observable state only within actions or reactions. This ensures that state changes are tracked correctly and that MobX can optimize reactivity. Directly modifying the state without restrictions can lead to unpredictable behavior. The other options are not considered best practices in MobX.
Which of the following is a common pitfall when trying to embed expressions in JSX?
- Not using any curly braces, relying on plain text.
- Not using curly braces to enclose expressions.
- Using double curly braces to enclose expressions.
- Using single curly braces instead of double curly braces.
A common pitfall when trying to embed expressions in JSX is not using curly braces to enclose expressions. JSX requires curly braces to indicate that you are embedding JavaScript expressions within the markup. Using single or double curly braces correctly is crucial, and not using any curly braces would result in plain text, not an embedded expression.
What happens if you include a JavaScript object inside curly braces in JSX?
- It throws a runtime error, as objects are not allowed in JSX.
- The object is automatically converted to HTML markup.
- The object is executed as JavaScript code, potentially causing issues.
- The object is treated as a string and rendered as plain text.
When you include a JavaScript object inside curly braces in JSX, the object is treated as a string and is rendered as plain text. JSX does not automatically convert objects to HTML markup or execute them as code by default. Attempting to render an object directly may lead to unexpected rendering issues.
In Next.js, how would you run code exclusively on the server and not expose it to the client-side bundle?
- Include the code in the main JavaScript bundle.
- Place the code in the client/ directory.
- Use a