Cognizant Reactjs Developer Interview Questions and Answers

Q1. React basic,event loop, Lazy Loading, Suspense, Javascript basics
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Q2. Create counter application
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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. Splice & slice difference
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Splice is used to add/remove elements from an array, while slice is used to extract a portion of an array without modifying the original array.
• Splice modifies the original array, while slice does not.

• Splice can add elements, remove elements, or replace elements in an array.

• Slice returns a new array with the selected elements from the original array.

• Example: const arr = [1, 2, 3, 4, 5]; arr.splice(2, 1); // removes elem...read more
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Q2. Coding question | How to reverse string
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To reverse a string, iterate through the characters and swap them from start to end.
• Create an empty string to store the reversed result.

• Iterate through the characters of the input string from end to start.

• Append each character to the empty string to reverse the order.

• Return the reversed string.
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Q1. Basics of javascript and react concept.
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Asked about vanilla.js in react interview.

Q1. Explain about the redux workflow
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Redux workflow involves actions, reducers, and store to manage application state.
• Actions are dispatched to describe what happened in the application

• Reducers specify how the application's state changes in response to actions

• Store holds the application state and allows access to it

• Components can subscribe to the store to receive updates when the state changes
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Q2. What is virtual DOM
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Virtual DOM is a lightweight copy of the actual DOM that React uses to improve performance by minimizing actual DOM manipulations.
• Virtual DOM is a concept where a lightweight copy of the actual DOM is created and manipulated by React.

• React uses the virtual DOM to efficiently update the actual DOM by only making necessary changes.

• When state or props change in a React component, a new virtual DOM representation is create...read more
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Q1. Wat is the hooks
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Hooks are a feature in React that allow you to use state and other React features in functional components.
• Hooks were introduced in React 16.8.

• They allow you to use state and other React features without writing a class component.

• Some commonly used hooks are useState, useEffect, useContext, and useRef.

• Hooks must be used at the top level of a functional component.

• Hooks can be custom created as well.
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