React interview

Question 1

What is React?

Answer 1

A JavaScript library for building user interfaces.

Question 2

True or False: React uses a virtual DOM.

Answer 2

True

Question 3

What are components in React?

Answer 3

Reusable pieces of UI that can be defined as classes or functions.

Question 4

Fill in the blank: In React, a component’s state is managed using the ______ hook.

Answer 4

useState

Question 5

What is JSX?

Answer 5

A syntax extension for JavaScript that looks similar to XML or HTML.

Question 6

What is the purpose of the useEffect hook?

Answer 6

To perform side effects in function components.

Question 7

What does props stand for in React?

Answer 7

Properties, which are used to pass data from parent to child components.

Question 8

True or False: React components must return a single root element.

Answer 8

True

Question 9

What is the difference between state and props?

Answer 9

State is managed within a component, while props are passed from parent to child components.

Question 10

What is a higher-order component (HOC)?

Answer 10

A function that takes a component and returns a new component.

Question 11

Fill in the blank: In React, the ______ method is used to update the component’s state.

Answer 11

setState

Question 12

What is the purpose of the React Router?

Answer 12

To enable navigation between different components in a React application.

Question 13

What are controlled components in React?

Answer 13

Components that derive their form data from the component’s state.

Question 14

What is TypeScript?

Answer 14

A superset of JavaScript that adds static type definitions.

Question 15

True or False: TypeScript can be used with React applications.

Answer 15

True

Question 16

What is the purpose of interfaces in TypeScript?

Answer 16

To define the shape of an object.

Question 17

What does the ‘any’ type in TypeScript signify?

Answer 17

It allows a variable to hold any type of value.

Question 18

Fill in the blank: In TypeScript, you can define a type using the ______ keyword.

Answer 18

type

Question 19

What is the use of the ‘key’ prop in React?

Answer 19

To uniquely identify elements in a list for efficient updates.

Question 20

What is the significance of the useRef hook?

Answer 20

It allows you to create mutable references to DOM elements.

Question 21

What is the difference between class components and functional components?

Answer 21

Class components are ES6 classes, while functional components are plain JavaScript functions.

Question 22

True or False: React.StrictMode is used to highlight potential problems in an application.

Answer 22

True

Question 23

What is the purpose of the Context API in React?

Answer 23

To provide a way to pass data through the component tree without passing props manually at every level.

Question 24

Fill in the blank: You can manage global state in React using the ______ hook.

Answer 24

useContext

Question 25

What is a React fragment?

Answer 25

A lightweight component that allows grouping of multiple elements without adding extra nodes to the DOM.

Question 26

What is the purpose of the shouldComponentUpdate lifecycle method?

Answer 26

To determine whether a component should re-render.

Question 27

What is the use of the useMemo hook?

Answer 27

To memoize expensive calculations and optimize performance.

Question 28

What does the term 'lifting state up' mean in React?

Answer 28

Moving state to a common ancestor component to share it among child components.

Question 29

What is the purpose of the useCallback hook?

Answer 29

To return a memoized callback function.

Question 30

True or False: React only re-renders components that have changed.

Answer 30

True

Question 31

What is the difference between useEffect and useLayoutEffect?

Answer 31

useLayoutEffect runs synchronously after all DOM mutations, while useEffect runs asynchronously after painting.

Question 32

Fill in the blank: In TypeScript, you can enforce a type on a function parameter using ______ syntax.

Answer 32

functionName(param: type)