Genpact Senior React Native Developer Interview Questions and Answers

Q1. What is the difference between a development dependency and a regular dependency in software development?
Ans. 
Development dependencies are needed for development and testing, while regular dependencies are needed for the application to run.
• Development dependencies are used during the development process, such as testing frameworks or build tools.

• Regular dependencies are required for the application to function properly in production.

• Development dependencies are typically listed in the devDependencies section of package.json, w...read more
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Q2. What do the symbols ^ and ~ represent in the package.json file?
Ans. 
Symbols ^ and ~ in package.json represent version ranges for dependencies.
• The symbol ^ represents a range that allows minor version updates.

• The symbol ~ represents a range that allows only patch updates.

• For example, ^1.2.3 allows any version from 1.2.3 to <2.0.0, while ~1.2.3 allows any version from 1.2.3 to <1.3.0.
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Q3. How can a 404 page be handled in React routing?
Ans. 
404 page can be handled in React routing by creating a Route component with a path of '*' at the end of all other routes.
• Create a Route component with a path of '*' at the end of all other routes in the Switch component.

• Inside the '*' Route component, render a custom 404 page component.

• Use the Switch component to ensure that only one Route is rendered at a time.
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Q4. Some Javascript coding questions.
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Q5. What is the component lifecycle in functional components?
Ans. 
Component lifecycle in functional components involves useEffect hook for side effects.
• Functional components use useEffect hook to handle side effects like fetching data, subscribing to events, etc.

• useEffect hook can be used to mimic componentDidMount, componentDidUpdate, and componentWillUnmount lifecycle methods.

• useEffect hook takes a callback function as its first argument and an optional array of dependencies as its...read more
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Q6. Explain redux data flow
Ans. 
Redux data flow is a unidirectional flow of data in React applications using a centralized store.
• Actions are dispatched to the store

• Reducers update the state based on the action

• Components subscribe to the store to access the updated state
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Q1. Explain Virtual DOM, Key Features of React, Hooks in React, create a todo app in react
Ans. 
Virtual DOM is a lightweight copy of the actual DOM, React key features include component-based architecture, declarative syntax, and virtual DOM, React Hooks are functions that let you use state and other React features without writing a class.
• Virtual DOM is a lightweight copy of the actual DOM that React uses to improve performance by updating only the necessary parts of the DOM.

• Key features of React include componen...read more
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Q2. Javascript Questions- Closures,promises,Async/await,setTimeOut, write acode to reverse a string
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Q1. Self Introduction, some situation based questions
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Q2. Basic HR regular questions
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Q1. React basic,event loop, Lazy Loading, Suspense, Javascript basics
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Q2. Create counter application
Ans. 
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
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Q1. What are the advantages of React
Ans. 
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
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Q2. How the performance optimization can be done in React Js Application
Ans. 
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
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Q3. What is the purpose of useMemo and UseCallBack hook
Ans. 
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
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Q1. Technical and optimization techniques related
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Q2. Coding questions of java script
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Q1. What is prop drilling
Ans. 
Prop drilling is the process of passing props down multiple levels of nested components in React.
• Prop drilling occurs when a prop needs to be passed through multiple levels of components that do not need the prop themselves.

• It can lead to unnecessary passing of props through intermediate components, making the code harder to maintain.

• To avoid prop drilling, you can use Context API, Redux, or React's useContext and useR...read more
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Q2. What is hoisting
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during the compilation phase.
• Variable declarations are hoisted to the top of their scope, but not their assignments.

• Function declarations are fully hoisted, meaning they can be called before they are declared.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q1. Explain useContext hook
Ans. 
useContext hook allows components to access data from a context without passing props down manually
• useContext hook is used to consume a context created by React.createContext

• It takes the context object as an argument and returns the current context value for that context

• It allows components to subscribe to context changes and re-render when the context value changes
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Q1. Frontend developer
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Html, CSS, bootstrap, JavaScript, react.js

Online coding round which included question from React and js

Q1. Common questions from js
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Q2. Coding to do in react
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Q1. Managerial questions
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Q2. Questions based on resume
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Q1. Salary discussion
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