Zeplinix Technologies Reactjs Developer Interview Questions and Answers

Q1. Basics of react, javascript, hooks
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Q1. What is Pure components/memo/useCallback/HoC
Ans. 
Pure components, memo, useCallback, and HoC are optimization techniques in React for improving performance.
• Pure components are components that only re-render when their props or state change.

• memo is a higher order component that memoizes the result of a component rendering, preventing unnecessary re-renders.

• useCallback is a hook that memoizes functions, preventing unnecessary re-creations on re-renders.

• HoC (Higher Orde...read more
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Q1. CSS specificity questions
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Q2. CSS selectors related questions
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Q3. Javascript basic questions
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Q4. React basic questions
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Q5. Javascript eventloop related guess the output.
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Q6. Write code in react of React.memo
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Q1. Scenario based and General ReactJS and javascript Questions.
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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. What is hoisting in JS
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Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope.
• Hoisting applies to both variable and function declarations.

• Variable declarations are hoisted but not their initializations.

• Function declarations are fully hoisted, allowing them to be called before they are declared.

• Hoisting does not apply to variables declared with let or const.

• Hoisting can lead t...read more
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Q2. What are higher-order functions in JS
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Higher-order functions are functions that take one or more functions as arguments or return a function as their result.
• Higher-order functions can be used to create reusable code by abstracting common patterns.

• They enable functional programming paradigms like currying and composition.

• Examples of higher-order functions in JavaScript include map, filter, and reduce.
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Q3. Difference between var, let, and const in JS
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var is function scoped, let and const are block scoped.
• var can be redeclared and updated within its scope

• let can be updated but not redeclared within its scope

• const cannot be updated or redeclared once declared

• let and const are not hoisted like var

• const must be initialized during declaration
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Q4. What are Hooks in React.js
Ans. 
Hooks are a feature in React.js that allow developers to use state and other React features in functional components.
• Hooks are functions that let you use React features in functional components

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

• Hooks provide a way to reuse stateful logic between components

• Some commonly used hooks are useState, useEffect, and useContext
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Q5. Presentation component vs functional component in React.js
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Q6. Bind(), call(), apply() in JS
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