SUMAGO INFOTECH Reactjs Developer Interview Questions and Answers

Counter application using Reactjs

• Create a React component for the counter

• Use state to keep track of the count

• Implement functions to increment and decrement the count

• Display the count on the screen

React offers advantages such as virtual DOM for improved performance, reusable components, and easy integration with other libraries.

• Virtual DOM for efficient updates and improved performance

• Reusable components for easier development and maintenance

• Easy integration with other libraries like Redux for state management

• Support for server-side rendering for better SEO performance

Performance optimization in React Js can be achieved through code splitting, memoization, virtualization, and minimizing re-renders.

• Implement code splitting to load only necessary components when needed

• Use memoization techniques like useMemo and useCallback to prevent unnecessary re-renders

• Implement virtualization for long lists or tables to render only visible items

• Minimize re-renders by using shouldComponentUpdate or

useMemo and useCallback are hooks in React used for optimizing performance by memoizing values and functions respectively.

• useMemo is used to memoize the result of a function so that it is only recomputed when its dependencies change.

• useCallback is used to memoize a function instance so that it is not recreated on every render unless its dependencies change.

• Both hooks help in optimizing performance by preventing unneces...read more

Flatten an array without using inbuilt methods

• Use recursion to iterate through the array and flatten it

• Create a new array to store the flattened elements

• Check if each element is an array, if so, recursively call the function to flatten it

Redux is a predictable state container for JavaScript apps. It helps manage the state of an application in a more organized way.

• Redux is a state management tool commonly used with React to manage the state of an application.

• It follows a unidirectional data flow, where the state is stored in a single store.

• Actions are dispatched to update the state, and reducers specify how the state should change in response to actions...read more

Context API is used in React to pass data through the component tree without having to pass props down manually at every level.

• Avoids prop drilling by providing a way to share values like themes, user data, etc. across the component tree.

• Helps in managing global state in React applications.

• Context API consists of Provider and Consumer components to provide and consume the context data.

• Can be used for theming, localizat

States are mutable data managed within a component, while props are immutable data passed from parent to child components.

• States are managed within a component and can be changed using setState method

• Props are passed from parent to child components and are immutable

• States are used for internal component data management, while props are used for passing data between components

• Example: A counter component may have a stat...read more

Data can be passed from children to parents in React components by using callback functions.

• Use callback functions to pass data from child components to parent components

• Parent component passes a function as a prop to child component

• Child component calls the function with the data as an argument to pass data to parent component