Pivotrics User Interface and Frontend Developer Interview Questions and Answers

Resume shortlist candidate for next round technical round.

Q1. What is react virtual dom
Ans. 
React virtual DOM is a lightweight copy of the actual DOM, used for efficient updates and rendering in React applications.
• Virtual DOM is a concept where a lightweight copy of the actual DOM is created and updated by React.

• React compares the virtual DOM with the actual DOM and only updates the necessary parts for better performance.

• This helps in minimizing the number of DOM manipulations and improves the overall perform...read more
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Q2. What are the ES6 features
Ans. 
ES6 features are new additions to JavaScript introduced in ECMAScript 2015.
• Arrow functions for more concise syntax: const add = (a, b) => a + b;

• Let and const for block-scoped variables: let x = 5; const y = 10;

• Template literals for easier string interpolation: const name = 'John'; console.log(`Hello, ${name}!`);

• Classes for object-oriented programming: class Person { constructor(name) { this.name = name; } }

• Destructurin...read more
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Q3. Difference between var,let and const
Ans. 
var is function scoped, let is block scoped, const is block scoped and cannot be reassigned.
• var is function scoped

• let is block scoped

• const is block scoped and cannot be reassigned
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Q4. Difference between spread and rest operator
Ans. 
Spread operator is used to split up array elements or object properties, while rest operator is used to merge multiple elements into an array.
• Spread operator is denoted by three dots (...) and is used to spread array elements or object properties.

• Rest operator is also denoted by three dots (...) and is used to collect multiple elements into a single array.

• Spread operator can be used to concatenate arrays or objects, wh...read more
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Q5. Hooks in reactjs
Ans. 
Hooks in ReactJS are functions that let you use state and other React features without writing a class.
• Hooks were introduced in React 16.8 to allow functional components to have state and lifecycle methods.

• useState() is a hook that allows you to add state to functional components.

• useEffect() is a hook that allows you to perform side effects in functional components.

• Custom hooks can be created to reuse logic across mult...read more
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Q6. What is high order function
Ans. 
A high order function is a function that takes one or more functions as arguments or returns a function as its result.
• High order functions can be used to create more flexible and reusable code.

• They can be used to abstract and encapsulate common patterns in code.

• Examples include map, filter, and reduce functions in JavaScript.
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Q7. What is hoisting
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope.
• Variable declarations are hoisted to the top of their scope but not their initializations.

• Function declarations are fully hoisted, including their definitions.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q8. Diference between display none and visibilityhidden
Ans. 
display none removes element from layout, visibility hidden hides element but still takes up space
• display none removes element from layout flow

• visibility hidden hides element but still takes up space

• display none is more efficient for hiding elements

• visibility hidden is better for hiding elements while keeping layout intact
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