Capgemini React Js Frontend Developer Interview Questions and Answers

Virtual DOM is a lightweight copy of the actual DOM, used for efficient updates in React applications.

• Virtual DOM is a concept in React where a lightweight copy of the actual DOM is maintained.

• When changes are made to the virtual DOM, React compares it with the actual DOM and only updates the necessary parts.

• This helps in improving performance by minimizing the number of updates to the actual DOM.

Hooks are a new addition in React 16.8 that allow you to use state and other React features without writing a class.

• Hooks are functions that let you use state and other React features in functional components.

• useEffect is a hook that lets you perform side effects in function components.

• It is similar to componentDidMount, componentDidUpdate, and componentWillUnmount in class components.

• useEffect takes two arguments...read more

Use the spread operator or Object.assign() method to copy an object in JavaScript.

• Use the spread operator: const newObj = { ...oldObj };

• Use Object.assign() method: const newObj = Object.assign({}, oldObj);

Throttling is a technique used to control the rate at which a function is executed.

• Throttling limits the number of times a function can be called over a specified time period.

• It helps in optimizing performance by preventing excessive function calls, especially in scenarios like scroll events or API requests.

• Example: Limiting the number of API calls to a server to prevent overwhelming the server with too many reque...read more

Props are used to pass data from parent to child components in React. Ternary operator is a conditional operator that evaluates a condition and returns one of two values.

• Props are read-only and help in maintaining the unidirectional data flow in React

• Ternary operator syntax: condition ? value if true : value if false

• Example of props:

• Example of ternary operator: const message = isTr...read more