Vanilla Networks React Developer Interview Questions and Answers

Q1. 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, meaning they can be called before they are declared.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q2. Difference between map and filter
Ans. 
Map is used to transform each element of an array, while filter is used to select elements based on a condition.
• Map returns a new array with the same length as the original array, but with each element transformed based on a function.

• Filter returns a new array with only the elements that pass a certain condition specified by a function.
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Maths and English aptitude test

HTML5 , CSS3 , Javascript , React.js , bootstrap.

Q1. Technical questions
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Q1. Please give information about the company
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Q1. What is closuer? is normal function call as closuer or not
Ans. 
A closure is a function that has access to its own scope, as well as the scope in which it was defined.
• A closure allows a function to access variables from its outer function even after the outer function has finished executing.

• Closures are created whenever a function is defined within another function.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { console.log(outerVa
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Q2. What is asyn/await
Ans. 
Async/await is a feature in JavaScript that allows for asynchronous code to be written in a synchronous manner.
• Async/await is built on top of promises and provides a more readable and concise way to work with asynchronous code.

• The 'async' keyword is used to define a function as asynchronous, allowing it to use the 'await' keyword inside it.

• When 'await' is used, it pauses the execution of the function until the promise ...read more
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Q3. Remove duplicate from array
Ans. 
Use Set to remove duplicates from array of strings.
• Create a Set from the array to automatically remove duplicates

• Convert the Set back to an array if needed

• Example: const arr = ['apple', 'banana', 'apple', 'orange']; const uniqueArr = [...new Set(arr)];
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Q4. Hoe does react Dom update?
Ans. 
React DOM updates by comparing the virtual DOM with the actual DOM and only updating the necessary components.
• React creates a virtual DOM to represent the UI components.

• When a state or prop changes, React re-renders the virtual DOM.

• React then compares the virtual DOM with the actual DOM to identify the differences.

• Only the necessary components are updated in the actual DOM, minimizing performance impact.
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Q5. What is react hooks explain some
Ans. 
React Hooks are functions that let you use state and other React features without writing a class.
• React 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 useRef.

• Hooks make it easier to reuse logic across components.

• Hooks can be used to manage component state, perform side effects, and more.
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Q6. What is call bind apply?
Ans. 
Call, bind, and apply are methods used to manipulate the value of 'this' in JavaScript functions.
• Call - invokes a function with a specified 'this' value and arguments provided individually.

• Bind - creates a new function that, when called, has its 'this' keyword set to the provided value.

• Apply - invokes a function with a specified 'this' value and arguments provided as an array.
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Q7. What is difference b/w redux and redux toolkit
Ans. 
Redux Toolkit is a set of tools and best practices to simplify Redux development, while Redux is a predictable state container for JavaScript apps.
• Redux Toolkit provides a set of tools like createSlice, createAsyncThunk, and configureStore to simplify Redux setup and reduce boilerplate code.

• Redux Toolkit includes immer library for writing immutable update logic in a more convenient way.

• Redux Toolkit also includes a def...read more
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Q8. Write a RTL test to check the button
Ans. 
Writing a RTL test to check a button in React
• Use the render and fireEvent functions from @testing-library/react

• Find the button element using getByRole('button')

• Simulate a click event using fireEvent.click

• Assert that the button is visible and clickable
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Q9. What inline level and block level elements
Ans. 
Inline and block level elements are two types of HTML elements with different display behaviors.
• Inline elements flow in the same line as surrounding content, while block level elements take up the full width available.

• Examples of inline elements include <span>, <a>, and <strong>.

• Examples of block level elements include <div>, <p>, and <h1>.
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Q10. Explain microtasks in js
Ans. 
Microtasks in JavaScript are tasks that are executed asynchronously and have higher priority than regular tasks.
• Microtasks are scheduled to run after the current script has finished but before the browser has a chance to render.

• They are often used with promises, as promise callbacks are executed as microtasks.

• Microtasks are executed in the same event loop iteration as regular tasks, but before the next rendering.

• Exampl...read more
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Q11. Explain customhooks
Ans. 
Custom hooks are reusable functions that allow you to extract component logic into separate functions.
• Custom hooks are prefixed with 'use' and can call other hooks if needed.

• They can be used to share logic between components without duplicating code.

• Custom hooks can be created for any kind of logic, such as fetching data, managing state, or handling side effects.
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Q12. How to manage state using redux
Ans. 
Redux is a predictable state container for JavaScript apps. It helps manage the state of an application in a centralized store.
• Create a Redux store to hold the state of the application

• Define actions to describe state changes

• Write reducers to specify how the state changes in response to actions

• Dispatch actions to update the state in the store

• Connect components to the Redux store using the connect function from react-red
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Q13. Explain redux work flow
Ans. 
Redux is a predictable state container for JavaScript apps.
• Actions are dispatched to the store

• Reducers specify how the state changes in response to actions

• Store holds the state of the application

• Components can subscribe to the store to access state
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Easy interview about react js and redux . asked write code to fetch api and do some routing

Online coding round which included question from React and js

Q1. Common questions from js
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Q2. Coding to do in react
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Q1. Managerial questions
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Q2. Questions based on resume
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Q1. Salary discussion
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Q1. Coding and basics both asked
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Q1. Coding and basics both asked
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Q1. Tell about yourself
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Q2. Question-Related to react
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Q3. Based on the project what functionality you develop that was toughest for you
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Q1. Questions related to css, html, scenario based, react common concepts on hooks , classes etc. Javascript primitives vs non primitives , polyfills etc
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