c t tech Interview Questions and Answers

1. What is the difference between == and === in JavaScript?

   • Answer: == performs loose equality comparison, meaning it coerces the operands to the same type before comparison. === performs strict equality comparison, meaning it checks for both value and type equality without coercion. For example, 1 == "1" is true, but 1 === "1" is false.

2. Explain the concept of closures in JavaScript.

   • Answer: A closure is a function that has access to variables from its surrounding lexical environment, even after that environment has finished executing. This allows functions to "remember" their environment, which is useful for creating private variables and stateful functions.

3. What is the difference between a stack and a queue?

   • Answer: A stack follows the Last-In, First-Out (LIFO) principle (like a stack of plates), while a queue follows the First-In, First-Out (FIFO) principle (like a line at a store).

4. What are the different types of joins in SQL?

   • Answer: Common SQL joins include INNER JOIN (returns rows only when there is a match in both tables), LEFT JOIN (returns all rows from the left table and matching rows from the right table), RIGHT JOIN (returns all rows from the right table and matching rows from the left table), and FULL OUTER JOIN (returns all rows from both tables).

5. Explain normalization in databases.

   • Answer: Database normalization is the process of organizing data to reduce redundancy and improve data integrity. It involves dividing larger tables into smaller ones and defining relationships between them.

6. What is RESTful API?

   • Answer: A RESTful API (Representational State Transfer Application Programming Interface) is an architectural style for building web services. It uses standard HTTP methods (GET, POST, PUT, DELETE) to interact with resources identified by URIs.

7. What is the difference between GET and POST requests?

   • Answer: GET requests are used to retrieve data from a server, while POST requests are used to send data to a server to create or update a resource. GET requests are typically idempotent (making the same request multiple times has the same effect), while POST requests are not.

8. What is the purpose of version control systems like Git?

   • Answer: Version control systems track changes to files over time, allowing developers to collaborate on projects, revert to previous versions, and manage different branches of development.

9. Explain the difference between HTTP and HTTPS.

   • Answer: HTTP (Hypertext Transfer Protocol) is an unencrypted protocol, while HTTPS (Hypertext Transfer Protocol Secure) uses SSL/TLS encryption to secure communication between a client and a server, protecting sensitive data like passwords and credit card information.

10. What is Agile development methodology?

    • Answer: Agile is an iterative and incremental approach to software development that emphasizes flexibility, collaboration, and customer satisfaction. It involves short development cycles (sprints) and frequent feedback loops.

11. What is polymorphism?

    • Answer: Polymorphism allows objects of different classes to be treated as objects of a common type. This allows for flexibility and code reusability.

12. Explain inheritance in object-oriented programming.

    • Answer: Inheritance is a mechanism where one class (subclass or derived class) acquires the properties and methods of another class (superclass or base class). It promotes code reusability and establishes an "is-a" relationship between classes.

13. What is encapsulation?

    • Answer: Encapsulation is the bundling of data and methods that operate on that data within a single unit (class). It protects data from outside access and modification, promoting data integrity and modularity.

14. What is abstraction?

    • Answer: Abstraction is the process of hiding complex implementation details and showing only essential information to the user. It simplifies the interaction with complex systems.

15. What is a design pattern?

    • Answer: A design pattern is a reusable solution to a commonly occurring problem in software design. They provide general, repeatable solutions to common design problems.

16. Explain the Model-View-Controller (MVC) architectural pattern.

    • Answer: MVC separates an application into three interconnected parts: the Model (data), the View (presentation), and the Controller (user interaction). This separation improves code organization and maintainability.

17. What is SOLID principles in object-oriented programming?

    • Answer: SOLID is an acronym for five design principles intended to make software designs more understandable, flexible, and maintainable: Single Responsibility Principle, Open/Closed Principle, Liskov Substitution Principle, Interface Segregation Principle, and Dependency Inversion Principle.

18. What is a microservice architecture?

    • Answer: A microservice architecture is an approach to software development where a large application is built as a collection of small, independent services. Each service focuses on a specific business function and can be developed, deployed, and scaled independently.

19. What is continuous integration/continuous deployment (CI/CD)?

    • Answer: CI/CD is a set of practices that automate the process of building, testing, and deploying software. It enables faster and more reliable software releases.

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