Nous Infosystems Senior Front end Developer Interview Questions and Answers

React js state and useeffect

Q1. Difference between callback, promises and async await?
Ans. 
Callbacks are functions passed as arguments, promises represent eventual completion of an asynchronous operation, async await is syntactic sugar for promises.
• Callbacks are functions passed as arguments to be executed after a certain task is completed.

• Promises represent the eventual completion of an asynchronous operation and allow chaining of multiple asynchronous operations.

• Async await is syntactic sugar for promises,...read more
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Q2. Explain the life cycle of react?
Ans. 
React has three main phases in its life cycle: Mounting, Updating, and Unmounting.
• Mounting: Component is created and inserted into the DOM.

• Updating: Component is re-rendered when props or state change.

• Unmounting: Component is removed from the DOM.
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Technical questions will be there

Simple coding questions will be asked.

Q1. Only about salary and joining dates.
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Duration was 1 hr and topics were css html react js vs code IDE it was a good experience

Q1. What is Tally t
Ans. 
Tally t is a software used for accounting and financial management.
• Tally t is a popular accounting software used by businesses for managing financial transactions.

• It helps in recording and tracking financial data such as sales, purchases, expenses, and more.

• Tally t provides features like invoicing, inventory management, payroll processing, and tax compliance.

• It is widely used in India and other countries for its user-f
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Q1. Basically javaacript concepts focused
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Q1. What is hoisting
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.
• Variable declarations are hoisted but not their initializations.

• 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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Q2. Name the CSS positions
Ans. 
CSS positions include static, relative, absolute, fixed, and sticky.
• Static - default position, elements are positioned according to the normal flow of the document

• Relative - positioned relative to its normal position

• Absolute - positioned relative to the nearest positioned ancestor

• Fixed - positioned relative to the viewport

• Sticky - acts like a combination of relative and fixed positioning
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Q3. What are semantic tags
Ans. 
Semantic tags are HTML tags that clearly define the content they contain for better accessibility and SEO.
• Semantic tags provide meaning to the content they enclose, making it easier for search engines to understand the structure of the page.

• Examples of semantic tags include

  ,

• Using semantic tags improves the accessibility of the website for users with disabilities, as screen readers can interp
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Q4. What is promise chaining
Ans. 
Promise chaining is a technique in JavaScript where multiple asynchronous operations are chained together to execute sequentially.
• Allows for handling multiple asynchronous operations in a more readable and organized way

• Each promise in the chain returns a new promise, allowing for further chaining

• Helps avoid callback hell by nesting promises inside each other

• Example: promise1.then(result => { return promise2; }).then(re
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Q5. Rest and spread operator
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Q6. What is virtual DOM
Ans. 
Virtual DOM is a lightweight copy of the actual DOM that React uses to improve performance by minimizing direct manipulation of the actual DOM.
• Virtual DOM is a concept in React where a lightweight copy of the actual DOM is created and updated in memory.

• When changes are made to the virtual DOM, React compares it with the actual DOM and only updates the necessary parts, reducing the number of direct manipulations to the ...read more
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Q7. Synthetic events in react
Ans. 
Synthetic events in React are events that are normalized by React to ensure consistent behavior across different browsers.
• Synthetic events are instances of the SyntheticEvent object in React.

• They are cross-browser compatible and have the same interface as native events.

• They are used to handle events like onClick, onChange, etc. in React components.

• Example: Click me
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Q8. What is redux in react
Ans. 
Redux is a predictable state container for JavaScript apps.
• Redux is a state management tool commonly used with React to manage the application's state in a predictable way.

• It helps in maintaining a single source of truth for the state of the entire application.

• Redux follows a unidirectional data flow, making it easier to understand how data changes over time.

• Actions are dispatched to update the state in Redux, and redu...read more
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Q9. What are hooks in react
Ans. 
Hooks in React are functions that let you use state and other React features without writing a class.
• Hooks were introduced in React 16.8.

• They allow you to use state and other React features in functional components.

• Some commonly used hooks are useState, useEffect, useContext, and useReducer.
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Q10. Difference between useMemo and useCallback
Ans. 
useMemo is used for memoizing values, while useCallback is used for memoizing functions.
• useMemo is used to memoize a value and only recompute it when its dependencies change.

• useCallback is used to memoize a function instance and only re-create it when its dependencies change.

• Example: useMemo can be used to memoize the result of a complex computation, while useCallback can be used to memoize a callback function passed t
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