Cyntexa React Js Frontend Developer Interview Questions and Answers

Decent questions asked in the online mcq test

Q1. Redux vs context API
Ans. 
Redux is a predictable state container for JavaScript apps, while Context API is a feature in React for passing data through the component tree.
• Redux is more suitable for larger applications with complex state management needs.

• Context API is simpler to use and is built into React, reducing the need for additional libraries.

• Redux provides a single source of truth for the application state, making it easier to debug and ...read more
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Q1. What is enums in typescript, difference between shallow and deep copy, what is virtual dom, what are closures, some psuedo codes, react machine coding. and other basic javascript questions.
Ans. 
Enums in TypeScript are a way to define a set of named constants. Shallow copy only copies the reference, while deep copy creates a new object. Virtual DOM is a lightweight copy of the actual DOM. Closures are functions that have access to their own scope and the scope of their containing function.
• Enums in TypeScript are used to define a set of named constants. For example, enum Color { Red, Green, Blue }

• Shallow copy c...read more
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Q1. Testing related questions, and other javascript and react questions.
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Q1. React Hooks and Project experience
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Q1. Performance Optimization Techniques
Ans. 
Performance optimization techniques for React JS frontend development
• Use React.memo for optimizing functional components

• Avoid unnecessary re-renders by using shouldComponentUpdate or PureComponent for class components

• Implement code splitting to reduce initial load time

• Use lazy loading for components that are not immediately needed

• Optimize images and assets for faster loading times

• Minimize the use of inline styles and u...read more
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Q2. Lazy Loading and other ques related to that
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Q1. General HR Interview
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Focused on JS questions

Q1. React concept explain
Ans. 
React is a JavaScript library for building user interfaces.
• React is a declarative, efficient, and flexible JavaScript library for building user interfaces.

• It allows developers to create reusable UI components.

• React uses a virtual DOM to improve performance by only updating the necessary parts of the actual DOM.

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

• React can ...read more
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Q1. Asked json web tokean authentication, authorisation. architecture of your project.
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Q2. Coding question- create crud app. Given array of objects. Render list in table. Do edit, delete, sort list on object property.
Ans. 
Create a CRUD app to render, edit, delete, and sort a list of objects in a table.
• Create a React component to render a table with data from the array of objects.

• Implement functions for editing and deleting objects from the list.

• Add functionality to sort the list based on object properties.

• Use state and props to manage data and re-render the table when changes occur.
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Q3. Difference bw rem, em, px. React hooks- useEffect, life cycle methods. use cases of hooks.
Ans. 
rem, em, px are units of measurement in CSS. useEffect is a React hook for side effects. Hooks are used for stateful logic in functional components.
• rem: relative to the font-size of the root element (html). Example: 1rem = 16px

• em: relative to the font-size of the element. Example: 2em = 32px if the font-size of the element is 16px

• px: fixed-size units. Example: font-size: 14px

• useEffect: React hook used for side effects ...read more
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Q1. Life Cycle Methods off class components
Ans. 
Life cycle methods are special methods in class components that allow developers to run code at specific points in the component's life cycle.
• componentDidMount() is called after the component has been rendered to the DOM.

• componentDidUpdate() is called after the component's state or props have been updated.

• componentWillUnmount() is called before the component is removed from the DOM.
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Q2. Diffrence between FlatList and ScrollView
Ans. 
FlatList is optimized for rendering large lists efficiently by only rendering the items that are currently visible, while ScrollView renders all of its children at once.
• FlatList is more performant for long lists as it only renders the items that are currently visible on the screen.

• ScrollView renders all of its children at once, which can lead to performance issues with large datasets.

• FlatList supports key extraction fo...read more
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Q3. Real World Scenories Questions
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Given the task to complete page design.

Decent questions asked in the online mcq test

Q1. Redux vs context API
Ans. 
Redux is a predictable state container for JavaScript apps, while Context API is a feature in React for passing data through the component tree.
• Redux is more suitable for larger applications with complex state management needs.

• Context API is simpler to use and is built into React, reducing the need for additional libraries.

• Redux provides a single source of truth for the application state, making it easier to debug and ...read more
Answered by AI
Add your answer