Genpact Reactjs Developer Interview Questions and Answers

Q1. How React Works?
Ans. 
React is a JavaScript library for building user interfaces that uses a virtual DOM to efficiently update the UI.
• React creates a virtual DOM to represent the UI components.

• When state or props change, React compares the virtual DOM with the actual DOM and updates only the necessary parts.

• React uses a component-based architecture to build reusable UI elements.

• React uses JSX, a syntax extension for JavaScript, to write com...read more
Answered by AI
Add your answer
Q2. How Redux Works?
Ans. 
Redux is a predictable state container for JavaScript apps.
• Redux stores the entire state of the application in a single immutable object.

• Actions are dispatched to describe state changes.

• Reducers specify how the state changes in response to actions.

• Components can subscribe to the Redux store to access the state.

• Redux helps manage the state of complex applications and makes it easier to debug and test.

• Example: dispatchin...read more
Answered by AI
Add your answer

Q1. Why is arrow function used
Ans. 
Arrow functions are used for concise syntax, lexical scoping of 'this', and implicit return of single expressions.
• Arrow functions have a more concise syntax compared to traditional function expressions.

• Arrow functions do not bind their own 'this' value, instead they inherit 'this' from the containing scope.

• Arrow functions automatically return the result of a single expression without needing the 'return' keyword.
Answered by AI
Add your answer
Q2. What is the need of de structuring syntax
Ans. 
Destructuring syntax allows for easy extraction of values from arrays or objects in JavaScript.
• Simplifies code by providing a concise way to extract multiple values from arrays or objects

• Improves readability and maintainability of code

• Can be used in function parameters to destructure objects directly

• Example: const person = { name: 'John', age: 30 }; const { name, age } = person;
Answered by AI
Add your answer

There were 15 mcq questions from JS, React,HTML and CSS

Q1. Basic React and Javascript questions
Add your answer

Q1. CSS specificity questions
Add your answer
Q2. CSS selectors related questions
Add your answer
Q3. Javascript basic questions
Add your answer
Q4. React basic questions
Add your answer
Q5. Javascript eventloop related guess the output.
Ans. 
Understanding the JavaScript event loop is crucial for predicting output in asynchronous code execution.
• The event loop handles asynchronous operations in JavaScript, allowing non-blocking execution.

• JavaScript uses a call stack and a message queue to manage execution contexts.

• Example: setTimeout(() => console.log('A'), 0); console.log('B'); outputs 'B' then 'A'.

• Microtasks (like Promises) are processed before macrotas...read more
Answered by AI
Add your answer
Q6. Write code in react of React.memo
Ans. 
React.memo is a higher-order component that optimizes functional components by memoizing their output.
• React.memo prevents unnecessary re-renders by memoizing the component's output based on props.

• It is useful for functional components that render the same output given the same props.

• Example usage: const MemoizedComponent = React.memo(MyComponent);

• You can provide a custom comparison function as the second argument to Re...read more
Answered by AI
Add your answer

Q1. What do you mean by redux and how to use redux
Ans. 
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
Answered by AI
Add your answer
Q2. What is the use of Context Api in React
Ans. 
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...read more
Answered by AI
Add your answer