Progressive Infotech React Js Frontend Developer Interview Questions and Answers

Q1. React QA and javascript QA
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Even after answering all the questions correctly along with coding done with exact expected output you will get rejected becoz they are fake job interview or eye wash campaign it’s better to avoid.

Q1. All basic and advance concept questions on javascript.
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Q2. React hooks and scenario based questions.
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Q1. Basic questions related to html5,css3,javascript,react js and DSA question to execute also
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Q2. 1.dsa for repeated array
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Implement a data structure and algorithm for finding repeated elements in an array.
• Use a hash map to store the frequency of each element in the array.

• Iterate through the array and update the frequency in the hash map.

• Return the elements with frequency greater than 1 as the repeated elements.
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Q3. 2.dsa for sorting array
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Implementing DSA for sorting array of strings
• Use a sorting algorithm like bubble sort, selection sort, or merge sort

• Compare strings using built-in comparison functions or custom comparison functions

• Ensure the sorting algorithm is efficient and handles edge cases
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Css3 questions JavaScript also. Login page and positions and dsa for flattened the nested array

2 problems, coding problems, java script

Q1. React version, redux middleware
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Q1. What is difference between useState, useContext and redux
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useState is for managing state within a component, useContext is for sharing state between components, and redux is for managing global state across the application.
• useState is a React hook used to manage state within a functional component

• useContext is a React hook used to share state between components without prop drilling

• Redux is a state management library that allows for managing global state across the applicatio...read more
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Q2. What is the difference between== and ===
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The difference between == and === in JavaScript
• == is the equality operator in JavaScript, which performs type coercion before comparing two values

• === is the strict equality operator, which does not perform type coercion and compares both value and type

• Using === is generally considered safer and more predictable than using ==

• Example: 1 == '1' will return true, but 1 === '1' will return false
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Q1. React life cycles
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Q2. Server side rendering
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Q3. Deep and shadow copy
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Q4. Ecmascript6 and latest updates with example
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ES6 is the latest version of ECMAScript with new features like arrow functions, classes, and template literals.
• Arrow functions provide a more concise syntax for writing functions.

• Classes allow for easier object-oriented programming in JavaScript.

• Template literals make it easier to work with strings by allowing interpolation and multiline strings.
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Creating react componont with api integration, list rendering and adding custom filterals

Coding exercise, custom hooks, UI related quetions

Q1. What is hoisting
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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
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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
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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
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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
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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
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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
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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
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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
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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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