Give an example of reselect usage?

  • A selector that returns the length of an array
  • A selector that filters and sorts data from the Redux store
  • A selector that computes the sum of two numbers
An example of reselect usage is a selector that filters and sorts data from the Redux store. This selector can take other selectors as input and use them to filter and sort the data before returning it. For example, you could create a selector that filters a list of items by a certain category and then sorts the results by price. This selector would only recompute when the input selectors (category and items) have changed, which can help to improve performance.

How do you say that props are read-only?

  • By using Object.freeze()
  • By using Object.preventExtensions()
  • By using Object.seal()
  • By not modifying them directly
In React, props are read-only and should not be modified directly. Attempting to modify props directly can cause bugs and make components unpredictable. Instead, components should create and maintain their own state to manage changes to data.

What's the purpose of at symbol in the redux connect decorator?

  • It is used to reference a component's props
  • It is used to reference the Redux store's state
  • It is used to reference a component's state
The @ symbol in the Redux connect decorator is used to reference the state of the Redux store. This allows the component to access the store's state without having to pass it down as props.

Why fragments are better than container divs?

  • Fragments are easier to use
  • Fragments are more performant
  • Fragments are more semantic
  • Fragments are not better than container divs
Fragments are better than container divs because they are more performant. Using a container div adds an extra DOM node, which can slow down rendering and create problems with styling. Fragments, on the other hand, allow you to group elements without adding any extra nodes to the DOM.

How to fetch data with React Hooks?

  • Use the componentDidMount() method
  • Use the fetch() function in a useEffect() hook
  • Use the componentWillMount() method
  • Use the AJAX library
In React, you can use the useEffect() hook to fetch data from an API. Inside the useEffect() hook, you can use the fetch() function to make a request to the API and update the component state with the response data.

What is the diffing algorithm?

  • A process for comparing two React elements
  • A process for reconciling changes in the React component tree
  • A process for optimizing React component rendering
  • A process for testing React components
The diffing algorithm is the process used by React to reconcile changes in the component tree and update the DOM. The diffing algorithm compares the new tree of React elements with the previous tree and identifies the minimum set of changes needed to update the DOM. This process is also known as reconciliation and is a key part of React's performance optimizations.

Can Redux only be used with React?

  • Yes, Redux can only be used with React
  • No, Redux can be used with any JavaScript framework or library
No, Redux can be used with any JavaScript framework or library, not just React. Redux is a standalone state management library that can be used with any UI framework or library, as well as with vanilla JavaScript applications. While it is commonly used with React, it can also be used with other popular frameworks such as Angular, Vue.js, and Ember.

How you implement Server-Side Rendering or SSR?

  • Use a third-party library
  • Use the "ReactDOMServer" module
  • Use the "ReactServer" package
  • Use the "server-render" package
To implement server-side rendering (SSR) in React, you can use the "ReactDOMServer" module. This module provides a method called "renderToString" that allows you to render a component to HTML on the server. You can then send this HTML to the client, where it can be hydrated into a full React application.

How to prevent unnecessary updates using setState?

  • Use shouldComponentUpdate lifecycle method
  • Use componentDidUpdate lifecycle method
  • Use componentWillUnmount lifecycle method
  • Use React.PureComponent
The shouldComponentUpdate lifecycle method can be used to prevent unnecessary updates to a component when its props or state have not changed. This method should return a boolean value indicating whether the component should update or not. By default, the method returns true, but it can be overridden to provide custom logic for determining whether an update is necessary.

What is the impact of indexes as keys?

  • Can cause issues with component state
  • Causes issues with component reusability
  • Improves performance
  • No impact
Using indexes as keys can cause issues with component state, particularly if the order of the items in the list changes. It can also lead to issues with duplicate keys if items are added or removed from the list. It is generally recommended to use a unique identifier as the key, rather than an index.