EPAM Systems React Js Frontend Developer Interview Questions, Process, and Tips

Q1. What projects or technologies I'm interested in?
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Q2. How I describe my seniority ?
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Q3. What was the most important work experience for you and why?
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Q1. How can we adapt the frontend to different view of devices?
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Responsive design using media queries and flexible layouts to adapt frontend to different devices.
• Use media queries in CSS to apply different styles based on screen size

• Utilize responsive frameworks like Bootstrap or Foundation for pre-built responsive components

• Implement flexible layouts using percentage-based widths and max-width properties

• Optimize images for different screen resolutions using srcset and sizes attrib...read more
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Q2. What is a closure in Javascript?
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A closure is a function that has access to its own scope, as well as the outer scope in which it was defined.
• A closure allows a function to access variables from an outer function even after the outer function has finished executing.

• Closures are commonly used to create private variables and functions in JavaScript.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { console
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Q3. What are the advantages of using Typescript? mention your favorite features
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Typescript offers advantages like static typing, improved code quality, better tooling support, and easier refactoring.
• Static typing helps catch errors at compile time

• Improved code quality due to type checking

• Better tooling support with features like code navigation and auto-completion

• Easier refactoring with the help of type annotations

• Faster development with enhanced IDE support
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Q4. Can you describe some Architectural Patterns ?
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Architectural patterns are reusable solutions to common problems in software architecture.
• MVC (Model-View-Controller) - Separates an application into three main components: the model, the view, and the controller.

• MVVM (Model-View-ViewModel) - Similar to MVC but with a ViewModel layer that manages the state and behavior of the view.

• Flux - Unidirectional data flow pattern commonly used with React applications.

• Microservic...read more
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Q5. Can you describe some Design Patterns ?
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Design patterns are reusable solutions to common problems in software design.
• Creational Patterns: Singleton, Factory, Builder

• Structural Patterns: Adapter, Decorator, Facade

• Behavioral Patterns: Observer, Strategy, Command
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Q6. Do you configured some part of a CI/CD pipeline?
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Yes, I have configured various parts of CI/CD pipelines.
• I have set up automated builds using tools like Jenkins or GitLab CI.

• I have configured automated testing processes within the pipeline.

• I have integrated deployment scripts to automatically deploy code to different environments.

• I have set up notifications for build status and deployment success/failure.

• I have worked on optimizing and improving the efficiency of CI/
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Q7. Can you mention some popular hacker attacks?(xxs, sql injection, etc)
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Some popular hacker attacks include XSS (Cross-Site Scripting) and SQL Injection.
• XSS (Cross-Site Scripting) - attackers inject malicious scripts into web pages viewed by other users

• SQL Injection - attackers insert malicious SQL code into input fields to manipulate database queries
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Q8. Solve a React problem, the goal is not trigger re-renders of a siblings components from a parent node, but avoiding the memo, useMemo, or useCallback react utilities. You can modify the original structure
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Q9. Describe the benefits of using SSR (server side rendering)
Ans. 
SSR improves SEO, performance, and initial load time of web applications.
• Improves SEO by serving fully rendered HTML to search engine crawlers

• Enhances performance by reducing time to first paint and time to interactive

• Faster initial load time for users, especially on slower network connections

• Better support for social media crawlers and web scrapers

• Enables content to be visible to users even if JavaScript is disabled
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Q10. How can we fetch our data ? (fetch api, axios, forms, websockets, graphql, trpc, etc)
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Q11. Name performance techniques. It's a wide topic so prepared to explain in detail
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Q12. Do you know how to measure web performance? (lighthouse with it's scores measures)
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Q13. Resolve a Leetcode problem -Merge two intervals.
Ans. 
Merge two intervals by sorting and iterating through the intervals.
• Sort the intervals based on the start value.

• Iterate through the intervals and merge overlapping intervals.

• Return the merged intervals.
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Q1. Difference between defer and async
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defer loads the script after the document has been parsed, async loads the script asynchronously without blocking the document parsing
• defer attribute loads the script after the document has been parsed

• async attribute loads the script asynchronously without blocking the document parsing

• defer scripts are executed in the order they appear in the document, async scripts are executed as soon as they are loaded

• defer is bette...read more
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Q2. Pseudo class vs Pseudo element
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Pseudo class selects elements based on their state, while pseudo element selects parts of an element.
• Pseudo class is used to style elements based on their state, such as :hover, :active, :focus.

• Pseudo element is used to style specific parts of an element, such as ::before, ::after, ::first-line.

• Pseudo class starts with a single colon (:), while pseudo element starts with a double colon (::).
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Q1. What is your method for preparing rice?
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Write a function , which accept a sorted array, and count the unique value in array. There can be negative number in array.eg arr[,-2, -1, -1, 0, 1,1 , 2, 3,3 , 4, 5]